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SEMESTER V
FOOD MICROBIOLOGY
UNIT I
Food as a substrate – Incidence and types of microorganisms in food – Contamination
and Spoilage of Meat, Poultry, Sea foods, Vegetables, Fruits.
UNIT II
Principles of food preservations: Asepsis, Preservation by use of High temperature, Low
temperature, Canning, Drying, Radiation and Food additives.
UNIT III
Food poisoning – Food borne diseases- Bacterial and Non- Bacterial. Microbial quality
and safety – Determining microorganisms in food culture, Microscopy and sampling methods –
Chemical and immunological methods.
UNIT IV
Fermented foods – Idli, Bread, Alcoholic beverages – Wine and Beer, Plant based
fermented foods – Miso, Ogi, Olives, Pickles, Sauerkraut, Soy sauce, Tempeh. Meat and fishery
products – Country cured hams, Dry sausages,Katsuobushi.
UNIT V
Dairy microbiology: Fermented milk products – Butter, Butter milk, Sour cream,
Youghurt, Cheese, Kefir, Koumiss, Taette and Tarhama.
References:
James. M. Jay, 1992, Modern food microbiology 4ed.
Frazier, W. C. and Westhoff D.C. 1989. Food Microbiology 8 ed.
Dubey. R.C. and Maheswari. D.K. A Textbook of Microbiology, 1999. 1 ed.
NEHRU ARTS AND SCIENCE COLLEGEDEPARTMENT OF MICROBIOLOGYMICROBIAL FOOD TECHNOLOGY
QUESTION BANK
SECTION A
1. Give four primary sources of micro organisms found in foods.
2. Write two bacterial genera that spoil the fresh meat.
3. Define Asepsis
4. Role of radiation in Food preservation
5. Define food Poisoning
6. Write two food borne diseases and their causative agents.
7. Which one of the following is unfermented milk product?
a) Kheer b) Curd c) Cheese d) Ghee
8.………………is used as a mold inhibitor in breads and cakes.
a) Calcium propionates b) Sodium propionates c) Sodium benzoate
d) None of these
9. Which one of the following preservatives control browning of fruits and
vegetables caused by enzyme.
a) Sulphur dioxide b) Ethylene c) Sodium d) All the above
10. Aflatoxin are produced by
a)Aspergillus b) Trichoderma c) Pencillium d) None of these
11. …………………….. is an example for bacterial food poison.
a) Botulism b) Trichoderma c) Actinomycetes d) None of these
12. Which one of the following method is used for microbiological examination of food?
a) Direct examination b) Canning c) Asepsis d) Drying
13. Define mycology with example?
14. What are the types of edible mushrooms?
15. The fruits that contain acids are more likely to be spoiled by
a) Bacteria b) Fungi c) Psychrophiles d) Viruses
16. ………................ produces a red colour in the meat.
a) Proteus vulgaris b) Micrococcus luteus c) Pseudomonas syncyanac
d) Serratia marcescens
17. …………………… produce Amatoxin
a) Amanita muscaria b) Amanita phalloides c) Agaricus compestris d) None of the above
18. Nicholas Appert was father of
a) Radiation b) Food additives c) Canning d) All the above
19. Comment on “Botulism”
20. …………….. is an effective drug for bacillary dysentery.
21. Distinguish mare’s milk and whole milk.
22. Ogi is commonly produced in
a) Southern Asia b) Nigeria c) World wide d) America
23. The sauerkraut is a fermentation product of
a) Cereal b) Cucumbers c) Cabbage d) Soya beans
24. …………….. is produced in the southern united states.
a) Katsuobushi b) Country cured hams c) Oliver d) MISO
25. The PH of the milk is
a) 6.2-6.3 b) 6.3-6.5 c) 6.7-6.9 d) 7.0-7.1
26. Which one of the following method is used for food preservation?
a) High salt mixing b) Gamma radiation c) Freeze drying d) All the above
27. Most perishable foods are
a) Meat of fish b) Potatoes c) Cereals d) Flake and sugar
28. Which one of the following is a milk borne disease?
a) Salmonellosis b) Brucellosis c) Hepatitis d) Pertussic
29. Clostidium butulinum is a contaminant for
a) Canned food b) Fermented food c) Liquid food d) Sea food
30. Important enzyme used to test for microbiological quality of milk is
a) Lactose reductase b) MB reductase c) MB lactase d) MB oxidase
31. Important bacterium responsible for spoilage of canned food is
a) Staphylococcus aureus b) Salmonella typhi c) Shigella dyscenteriae d)
Clostriduim butulinum
32. ……………….. is an ideal culture medium for animal pathogenic bacterium
a) Milk b) Meat c) Vegetable d) Fruit
33. The chemical substance that can be used for meat preservation is
a) Nitrate b) Sulphur dioxide c) Sulphite d)All the above
34. …………………. bacteria is involved in oxidation of ethyl alcohol in to acetic acid
a) E.Coli b) Acetobacter sp c) Alcaligenes d) Pseudomonas sp
35. The fungi without cross walls are called ………………..
a) Septate b) Non –septate c) Mycelium d) All the above
36. Write the cheese types with examples.
37. Characteristic flavor compound of butter milk is produced by ……………..
38. Spoliage of cereals depends on…………………….
39. The organisms causing “milk ropy” is …………………
40. ………………… is bottom type yeast in beer fermentation.
41. The antimicrobial substance found in egg white is
a) Latic acid b) Lysozyme c) Mycotoxin d) Bacteriocin
42. The white fuzzy growth of fungi in meat is called
a) Whiskers b) Putrefaction c) Souring d) Phosphorescence
43. Another name for freeze drying is
a) Osmosis b) Lyophilization c) Smoking d) Blanching
44. Microbes can be removed from a liquid food by the process of
a) Freezing b) Refrigeration c) Filtration d) Desiccation
45. The toxin produced by clostridium botulinum belongs to this group
a) Enterotoxin b) Neurotoxin c) Bacteriocin d) Mycotoxin
46. Which one of the following is a viable count method of estimating microganisms
a) MPN method b) Direct microscopic count c) Coulter counter d) Protein
estimation
47. During sauerkraut fermentation the amount of salt mixed with cabbage is
a) 1.5% b) 2.5% c) 3.5% d) 4.5%
48. The temperature at which breads are baked is
a) 100 °C b) 116°C c) 121 °C d) 240 °C
49. The holes in swiss cheese are as a result of microbial production of
a) Oxygen b) Carbondioxide c) Lactic acid d) Acetic acid
50. Lactic acid bacteria produce this aroma compound
a) Diacetyl b) Lactic acid c) Bacteriocin d) Exopolysaccharide
SECTION B
1. Define water activity and mention the minimal aw value for major spoilage organisms.
2. What are the major sources of contamination in fruits?
3. What is pasteurization and explain its objectives.
4. What is smoking? Explain its preservative effect?
5. Differentiate between bacterial exotoxin and endotoxin.
6. Compare and contrast total count and viable count of microbes in food.
7. Write a brief account on bread making.
8. Explain how fermentation serves as a method of food preservation.
9. What are the human pathogens transmitted through milk?
10. Write a brief account on buttermilk.
11. Explain how food serves as substrate for micro organisms. What are the intrinsic factors
of food that influence microbial growth?
12. Write on the contamination and spoilage of sea foods.
13. Discuss freezing of foods and its lethal effect on micro organisms.
14. Write an essay on irradiation of foods.
15. List out various food borne diseases, their causative organisms and foods involved.
16. Write a detailed account on mycotoxins and the key management steps to prevent
mycotoxin contamination.
17. Discuss the production of any one plant based fermented food.
18. Write an account on idli fermentation and the micro organisms involved in the
fermentation.
19. Discuss the production of kefir and koumiss.
20. Explain the probiotic characteristics of lactic acid bacteria.
21. List out any six bacteria contaminating food.
22. Write short notes on A sepsis.
23. Give an account on application of food preservation.
24. Write an essay on spoilage of vegetables.
25. Explain the spoilage of canned food.
26. Write short notes on leavening bread using yeasts.
27. How will you prepare the fermented food?
28. Discuss the food poisoning and food borne inflections.
29. Write an account on maintenance of quality control.
30. What are the factors affecting the growth of micro organisms in food?
31. Explain in detail the principles and methods of food preservation.
32. Write an account on drying, radiation and packing methods of food preservation.
33. Write an essay on spoilage of milk and milk products.
34. Explain the spoilage of cereals and cereal products.
35. Write an essay on fermented food products.
36. How will you prepare spoilage of cereals? Explain.
37. Write an account on bacterial food borne illness.
38. Discuss the investigation of food poisoning out breaks.
39. Briefly discuss about the food borne disease of bacterial origin.
40. Write various diseases caused by Non-bacterial origin.
41. What are the chemical methods to detect the micro organisms present in food materials?
42. Write briefly about the fermented milk products of butter milk and yoghurt.
43. Write briefly about the preparation on olives and sauerkraut.
44. Describe how you will preserve Food materials by High temperature.
45. What are the immunological methods to detect the micro organisms present in food
materials?
46. Mention four important methods adopted to determine the Micro-organisms present in
food samples.
47. Give a detailed account on the non-beveragic, plant based fermented foods.
48. Describe in detail about the meat and fishery products.
49. Describe how you will preserve food materials by low temperature.
50. Define Dairy Microbiology? Write in detail about the sour cream, kefir and koumiss
fermented milk products.
UNIT-1
1.Define food microbiology.
The science that deals with the microorganisms involved in the spoilage, contamination, and preservation of food.
2.Explain how food serves as substrate for micro organisms. What are
the intrinsic factors of food that influence microbial growth?
Food and microorganismsRELEVANCE OF MICROBIOLOGY Food serves as a interacting medium between various living species because, it is a source of nutrients for humans, animals as well as microorganisms. Food fit for human consumption is also a medium for the growth and activity of microorganisms. Hence human food is always associated with a variety of microorganisms. Since the primary function of microorganisms is self-perpetuation, they use the human or animal food as a source of nutrients for their own growth and activity. Microbial activity in a food can be beneficial in certain cases it leads to deterioration of the food and renders it unfit for human consumption. Four aspects of microbial activity are of relevance to processing and preservation of food.
Fermented foods Food chemicals from microorganisms Food poisoning & food borne diseases & Food spoilage.
Fermented foods:
Microorganisms can be used as processing aids in the production of fermented foods. New and modified foods with better shelf stability; palatability, flavour and organoleptic properties are produced by fermentation using specific microorganisms under controlled conditions.
Food chemicals from microorganisms:
A variety of food chemicals and additives produced by fermentation involving select species of microorganisms In addition, microorganisms themselves may be used as food. The biomass produced by fermentation can be harvested & used as a protein rich raw material for the formulation of foods.
Food poisoning & food borne diseases: Pathogenic microorganisms grow in the food utilizing the nutrients in the food & produce toxins, which are detrimental to the health of the consumer when such food is consumed. Food also serves as a vector or medium for certain pathogens that cause food infections & diseases.
Food spoilage:
The metabolic activity of various microorganisms not only utilizes the nutrients in food but also causes the spoilage of food through undesirable enzymatic changes affecting the quality of the food. The enzymatic changes include the formation of products, which contribute off-flavours & affect the organoleptic, textural and keeping qualities of food.
BACTERIA, YEAST AND MOULD:
Introduction:
Thousands of genera and species of microorganisms have been identified and classified. Several hundreds of these are associated in one way or other with food products. Many of them are of industrial importance as they find use in the production of new foods and food chemicals by fermentation and also in the preservation of food products. Microorganisms that are of importance in food microbiology include bacteria, yeast and molds.
Bacteria:
Bacteria are unicellular organisms of aerobic or anaerobic nature and exhibit many morphological forms. Three principal shapes have been well recognized, namely, spherical shapes of cocci, rod shape of bacilli and spiral form of Spirilla and Vibrios.
All bacteria associated with food are small in size, typically a few micrometers long and smaller in diameter. Bacteria form spores, which are seed like and far more resistant to heat, presence of inhibitory chemicals and other adverse conditions during food processing. Most bacteria multiply best at temperatures between 16 and 38C and are termed mesophilic. Psychrotropic or psychrophilic bacteria can grow at low temperatures while thermophilic ones can grow at higher temperatures.
Morphological characteristics important in food bacteriology:
One of the first steps n the identification of bacteria in food is microscopic examination to ascertain the shape, size, aggregation, structure and staining reactions of the bacteria present. The following characteristics may be of special significance.
ENCAPSULATION:
The presence of capsules or slime may account for sliminess of ropiness of a food. In addition, capsules serve to increase the resistance of bacteria to adverse conditions such as heat or chemicals. To the organism they may serve as a source of reserved nutrient.
FORMATION OF ENDOSPORES:
Bacteria of the genera Bacillus, Clostridium, Desulfotomaculum, Sporolactobacillus and Sporosarcina share the ability to form endospores. Of primary interest to the food microbiologists are the spore forming species of the genera Bacillus and Clostridium. Endospores are formed at an intracellular site, are very refractile, and are resistant to heat, ultraviolet light and desiccation.
Sporulation usually appears in the late logarithmic phase of growth, possibly because of nutrient depletion or product accumulation. During this transition of vegetative cell to spore, the spore become refractile, there is a massive uptake of Ca ions, and synthesis of dipicolinic acid(DPA) occurs, a compound absent from vegetative cells. The acquisition of heat resistance by the forming spore is closely correlated to the formation of DPA and the Ca 2+ uptake.
FORMATION OF CELL AGGREGATES:
It is characteristic of some bacteria to form long chains and of others to clump under certain conditions. It is more difficult to kill all bacteria in intertwined chains or sizable clumps than to destroy separate cells.
Cultural characteristics important in food bacteriology:
Bacterial growth in and on foods often is extensive enough to make the food unattractive in appearance or otherwise objectionable. Pigmented bacteria cause discolorations on the surface of liquids, growth may make surfaces slimy, or growth throughout the liquids may result in undesirable cloudiness or sediment.
Physiological characteristics important in food bacteriology:
The bacteriologist is concerned with the growth and activity of bacteria and other organisms in food and with the accompanying chemical changes. These changes include hydrolysis of complex carbohydrates to simple ones, hydrolysis of proteins to polypeptides, amino acids and ammonia or amines and hydrolysis of fats to glycerol and fatty acids.
O.R rxns, which are utilized by the bacteria to obtain energy from foods, yield such products as organic acids, alcohols, aldehydes, ketones and gases. A knowledge of the factors that favour or inhibit the growth and activity of bacteria is essential to an understanding of the principles of food preservation and spoilage.
Genera of Bacteria important in food Bacteriology:
Bacteria that play significant roles in foods are often grouped on the basis of their activity in foods without regard to their systemic classification.
Lactic acid bacteria ferment sugars to lactic acid and include species belonging to genera of Leuconostoc, lactobacillus, streptococcus and pediococcus. Their activity is desirable in a variety of foods such as sauerkraut and other pickled vegetables and dairy products for the production of flavour. They cause spoilage of wines.
Acetic acid bacteria oxidize ethanol to acetic acid. Species of genera Acetobacter and Gluconobacter are the most common. They are useful in vinegar manufacture but ate undesirable in alcoholic beverages.
Butyric acid bacteria are mostly the spore forming anaerobes of the genus clostridium. They produce butyric acid by fermenting sugars. Propionic acid bacteria produce propionic acid andbelong the genus propioni bacterium.
Proteolytic bacteria include a heterogenus group of bacteria, which produce extracellular proteases. Most species belonging to the genera of clostridium, Bacillus, pseudomonas and proteus.
Lipolytic bacteria are also a heterogeneous group of bacteria, which produce lipase. Organisms of the genera pseudomones, Alcaligens, Staphylococcus, Serratia and Micrococcus are lipolytic.
Saccharolytic bacteria ydrilyze disaccharides and polysaccharides to sampler sygas. Ex: Bacillus subtilis and Clostridium butyrium, which are also amylolytic.
Pectinolytic bacteria produce pectinases responsible for softening of plant tissues of loss of getting power in various plant foods. Ex: Bacillus, Achromobacter, Aeromonas, Arthrobacter and Flavobacterium are pectinolytic.
Thermiphylic and thermoduric bacteria are resistant to high temperature. Thermophilic bacteria are resistant. Cause spoilage of low acid canned foods. Important species include Bacillus steresthermiphilus and with thermosaccharoluticum. Thermiduric organisms survive heat treatment such as pasteurization. Ex: Bacillus, clostridium,Micrococcus streptococcus Lactobacillus and Mycobacterium are found in foods.
Psychrotrophic bacteria are able to survive and grow at refrigeration temperatures through their optimum temperatures of growth in around 20 to 30oc. Ex: Pseudomonal, Achromobacter, Alcaligenes and Flavobacterium are psychrotophic.
Halophilic bacteria include species of the genera Bacillus, Micrococcus, Vibrio, Moraxella, Halobacterium organisms require certain minimal concentrations of dissolved Nacl for their growth and survive at higher concentration of salt.
Osmophilic or saccharophilic bacteria grow in high concentrations of sugar. Ex: Leuconostoc species.
Pigmented bacteria produce colours during their growth in foods. Ex: Flavobacterium (yellow to orange), Serratia(red),Halococcus (red to orange) and Halobacterium (pink, red and orange), Lactobacillus plantarum produces rust colour pigment discolouring cheese. Flavobacterium species causes discolouration on the surface of meat and spoilage of Shell fish, poultry, eggs, butter and milk.
Slime or rope forming bacteria include Alcaligenes viscolactis, Enterobacter aerogenes and Klebsiella oxytoca and some species of streptococcus and Lactobacillug plantarum causes ropiness or ropiness in milk.
Gas forming bacteria include species of the genera of Leuconostic, Lactobacillus and propionibacterium which produce carbon-di-oxide species of Eschericbis, Enterobacter proteus, bacillus and Clostridium produce both carbon-di-oxide and hydrogen.
Off-flavour forming bacteria include those of genus streptomyces which produc undesirable flavours and musty of earthy odour and taste. Manu species of pseudomonas produce a variety of metabolites that affect the flavour of foods deleteriously.
Coliform bacteria ex. Escherichia coli and Enterobacter aerogenes. They cause spoilage of a variety of foods producing off-flavours and sliminess.
Some of the important disease causing bacteria include the following:
Which batulinum produces a neutotoxin in canned meat products and causes the fatal disease botulism.Corynebacterium species includes the diphtheria organism which diptheriae.Erwinia species are plant pathogens and damage plants and plant products causing bacterial soft rot.E. C oli species includes some serotypes which are pathogenic to humans.Myco bacterium species includes the tubercle bacilli M. tuberculosis that causes tuberculosis especially through raw milk from infected cows.Salmonella species are enteric pathogens that grow in foods and cause food infection.Shigella species is transported by foods and causes bacittary dysentery.Staphylococcus species includes the important S.aureus which produces an enterotoxin causing food poisoning.Streptococcus species includes pathogenic S.agalartide which causes mastitis in cows and S.pyogenes which causes septic sore throat, Scarlet fever and other diseases in humans. Vibrio species is pathogenic to humans.
3.EXPLAIN ABOUT THE GENERAL CHARACTERISTICS, CLASSIFICATION AND IMPORTANCE OF MOULDS, YEAST AND BACTERIA.General characteristics of moulds in food microbiology.
1) Moulds are multicellular , filamentous fungi whose growth is recognized by its fuzzy or cottony appearance.
2) They may be of white, coloured or dark or smoky.3) The thallus or vegetative body is characteristic feature of moulds.
MORPHOLOGICAL CHARACTERISTICS:I. HYPHAE AND MYCELIUM:
Hyphae à tubular, filamentous structure Mycelium à interwined hyphae Submerged hyphae à growing within the food Aerial hyphae à growing into air above the food
Sclerotia à tightly packed masses of modified hyphae, often thick-walled. à More resistant to heat
Septate à cross wall dividing the hypha into cells Aseptate à no cross walls Apical growth à septate hyphae increase in length by
means of divisison of the Tip cell
. Intercalary growth à division of cells within hyphae
II. REPRODUCTIVE STRUCTURES OF PARTS: Asexual spores à conidia àArthroconidia
àSporangiospores
àChlamydospores
Sexual spores àOosporesàZygospores
àAscospores
àBasidiospores
III. CULTURAL CHARACTERISTICS: Loose & fluffy, compact growth. Upper surface à may be velvety, dry, powdery, wet or gelatinous. Pigmentation à red, purple, yellow, brown, gray, black.
IV. PHYSIOLOGICAL CHARACTERISTICS:Moisture requirements – 14 to 15%
Temperature requirements – mesophiles(25 to 30c)
– psychrophiles(-5 to -10c)
– thermophiles(above 40 to 60c)
Oxygen & pH requirements -- aerobe, pH 2 to 8.5
Food requirements -- from simple to complex
Inhibitors -- fungicidal / mycostatic produced by certain moulds
CLASSIFICATION AND IDENTIFICATION OF MOULDS:
Kingdom : Myceteae
Identification:
1. Hyphae septate or aseptate.2. Mycelium clear or dark.3. Mycelium coloured or colourless.4. Sexual spores à oospores, zygospores or ascospores.5. Asexual spores à Sporangiospores, conidia or arthrospores (oidia)6. Characteristics of the spore head:
a) Sporangia à size, colour, shape, location.b) Spore heads bearing conidia à single conidia, chains, budding conidia or
masses, shape and arrangement of sterigmata or phialides etc.,2. Appearance of sporangiophores or conidiophores.3. Microscopic appearance of asexual spores.4. Presence of special structures à stolons, rhizoids, footcell ,apophysis, chlamydospores,
sclerotia etc.
Classification:
Division : Zygomycotina
Class : Zygomycetes (non septate mycelium, reproduction by sporangiospores, rapid growth)
Order : Mucorales
Family : Mucoraceae
Genus : Mucor
Rhizopus
Thamnidium
Division : Ascomycotina
Class : Pletomycetes(septate mycelium, ascospores(8))
Order : Eurotiales
Family : Trichocomaceae
Genus :Byssochlamys
Eupenicillium
Emericella
Eurotium
Division : Deuteromycotina
1. Class : Coelomycetes
Genus : Colletotrichum
2. Class : Hypomycetes (hyphae give rise to conidia )
Order : Hypomycetales
Family : Moniliaceae
Genus : Alternaria
Aspergillus
Aureobasidium ( Pullularia )
Botrytis
Cladosporium
Fusarium
Geotrichum
Helminthosporium
Monilia
Penicillium
Stachybotrys
Trichothecium
ORGANISM CHARACTERISTICS FOOD SPOILAGEMUCOR:M.racemosus
M.rouxiiNon – septate hyphae.
Sporangium with sporangiospores.
No rhizoids / stolon.
Ripening of cheese.
Whiskers on beef & black spots (frozen milk).
RHIZOPUS:R. stolonifer
(bread mold)
THAMNIDIUM T. elegans
ASPERGILLUSA. glaucus
A. repens
A. niger
A. flavus oryzae
PENICILLIUMP.expansumP. digitatum
P.camemberti
P.roqueforti
P. italicum
NEUROSPPORA(Monilia)
N. sitophila
Non septate hyphae.
Stolons & rhizoids.
Rhizoids are seen, sporangium with sporangiospores.
Sporangium with sporangiospores from sporangiophore.
Grows well in high sugar & salt conc.
Conidia are green, Ascospores are in asci.
Spores are large, tightly packed, black, brownish, black, purple brown & Conidia are rough with pigment & are in chains.
Conidia are yellow to green in colour & produce aflatoxin.
Blue-green spared mold
Olive/yellow-green conidia
Grayish conidia
Bluish-green conidia
Blue green conidia
Budding conidia with conidiophore
Spoilage of berries, fruits, vegetables, bread, apples.
Black spot on beef & frozen mutton.
(watery soft rot)
Chill storaged meat – whiskers.
Spoilage of grape jams & jellies.
Commercial production of citric, gluconate, enzyme production
Black rot of peach, figs, citrus.
Soft rot of fruit
Soft root of Citrus
Ripening of camembert cheese
Ripening of blue cheese
Rotting of citrus fruit.
Red bread mold – pink, loose textured growth
SPOROTRICHUMS. carnis
BOTRYTISB. cinerea
GEOTRICHUM(Oospora/ Oidium)G. candidum(O.lactis) – Dairy mold
CLADOSPORIUMC. herbarum
HELMINTHOSPORIUM
ALTERNARIAA. citriA. tenuisA. brassicae
FUSARIUM
TRICHOTHECIUMT. roseum
AUREOBASIDIUM(Pullularia)
BYSSOCHLAMYSB. fulva
A.A.
Conidiophore with conidia
Conidiophore with swollen tips producing conidia septate mycelium
Septate hyphae, Arthroconidia.
Imparts flavour & aroma to cheese
Dark molds, septate hyphae.
Growth is velvety, Olive coloured to black, Conidia are lemon shaped.
-
Septate mycelia, Brown, many celled conidia are in a chain on the conidiophore
Conidiophore produces conidia are of macro & microconidia.
Septate hypphae with conidiophores &
on bread.
Grows on sugarcane bagasse.
Seen on chilled meat causing white spots.
Disease in grapes – Gray mold of apples, pears, citrus, grapes.
Sour rot of citrus, peaches.
White to cream coloured growth.
Dairy cream, Meat & vegetables.
Black spot on the foods (beef), spoil butter.
Root on stone fruits, black rot of grapes.
Plant ppathogen, Saprophytes on vegetables
Soome sps produce mycotoxins, Rotting citrus ( stem & black rot ) fruit, Black rots of stone fruits, apples, figs.
Grown on foods, Brown rot of citrus fruit & Pineapples, soft rot of figs.
produces mycotoxins.
Yeast like colonies
Asci with ascosporesHeat resistant
Pink rot of fruits.
Blackk spot on beef, fruits & vegetables.
Spoilage of high acid canned foods.
Spoil canned & spoiled fruits.
4.E xplain about the factors influencing the growth of micro-organisms.
FACTORS INFLUENCING THE GROWTH OF MICRO-ORGANISMS Interactions between microorganisms and our foods are sometimes beneficial. Food is the
substrate, for the growth of microorganisms. The type of microorganisms present and the environmental conditions are also important.
The food or substrate dictates what can grow and cannot grow. The characteristics of the food or substrate one can make predictions about the microbial
flora that may develop. The factor that favor or inhibit the growth of microorganisms is essential for the
principles of food spoilage and preservation. The chief compositional factors of a food that influence microbial activity includes:
1. INTRINSIC FACTORS à 1. pH 2.Moisture content 3. Oxidation –reduction potential (Eh)
4. Nutrient content 5.Antimicrobial constituents
6.Biological structures2. EXTRINSIC FACTORS à 1. Temperature
2. RH of the environment 3. Presence or concentration of gases in the environment
INTRINSIC FACTORS:The parameters of plant and animal tissues that are inherent part of the tissues are
referred to as intrinsic factors.1. Hydrogen ion concentration pH:
PH is one of the main factors affecting the growth of survival of microorganisms in culture media
and in foods.
Example:- When pure water ionizes equal number of OH – and H+ are produced. Only a small amount of water ionizes so that the concentration of these ions is very small, -1 X 10^-7 mol/L. This can be summarized as follows:
H2O > OH- + H+[H+] =[OH-] = 1 X 10^-7 mol/LS solution containing equal number of H+ and OH – ions is neutral in reaction. A
solution containing more H+ ions than OH- ions is acid.A solution containing more OH- than H+ ions is alkaline.
Example:- A solution containing 10^-7 mole H+/L has a pH of 7 and is neutral. A solution containing 10^-5 mole H+/L has a pH of 5 and is acid. A solution containing 10^-8 mole H+/litre has a pH of 8 and is alkaline.pH RANGES FOR MICRO-ORGANISMS:-
All microorganisms have a pH range in which they can grow and an optimum pH at which they grow best. Saccharomyces cerevisiae, for example has a pH range of 2.35 – 8.6 with an optimum at pH 4.5.
pH not only influence the growth rate of an organism within its pH range but is also has an overall influence on the growth curve. This is illustrated in Fig. 6.10, which shows the effect of pH on the growth curve. Notice that is pHs below the optimum:
EFFECT ON pH ON THE GROWTH RATE OF BACTERIA, YEAST, AND MOULDS
growth rate decreases; the maximum number of cells produces drops; the length of the lag phase increases; the length of the stationary phase shortens; the death rate increases.
The temperature of the environment (incubation determines the pH minimum for an organism
temperature in the laboratory), the nutrients that are available, the water activity and the presence of inhibitors.
HOW DOES pH AFFECT MICROBIAL CELLS?The internal pH of cells is maintained near to pH 7.0(this may be lower in some
organisms,
e.g., yeasts in which the cells pH has been measured at pH 5.8) and is the pH at which cells metabolism works best.
Cells membranes are impermeable to H+ and OH- ions and, in addition, cells may have a mechanism to pump out H+ ions.
When organisms are subjected to pHs outside their optimum but within the growth range, K+ and OH- ions affect the outer layers of the cells but not the internal pH. pHs above and below the optimum for growth may affect the following: The enzymes (permeases) need for the uptake of nutrients, including essential ions. The production of extra cellular enzymes and their subsequent activity when released. The mechanism of ATP production in the bacteria, which involves the cell
membrane.When the microbial cell is subjected to extreme pHs cell membranes become damages. H+ and OH- ions
can then leak into the cell where enzymes are denatured and nucleic acid molecules are denatured, leading to cell death.
The effect of weak acids on microbial cells is temperature dependent. At concentrations that inhibit growth and cause cell death, they have less effect as the temperature is lowered.
The order of activity of acids in terms of their antimicrobial effect isPropionic > acetic > lactic > citric > phosphoric > hydrochloric.
pH and the growth of micro organisms in foods.Foods are quire variable in terms of their pHs. Most are acidic ranging from the
very acidic to almost neural in reaction.pH changes in foods due to the activity of micro-organisms. Milk sours as a result of latic acid production by streptococi and lactrobacilli. pHs of foods
Food pH Food pHLemon 2.2-2.4 Meat 5.4-6.9Strawberry 3.1-3.9 Halibut 5.6Tomato 3.9-4.6 Lettuce 6.0Pear 3.7-4.7 Cod 6.2-6.6Banana 4.5-4.7 Milk 6.3-6.6Carrot 5.0-6.0 Egg white 8.6-9.6Potato 5.3-5.6
Strong inorganic acid is not often included in processed foods but hydrochloric and phosphoric acids are used in the manufacture of carbonated and non-carbonated drinks. Coals, for example, contain phosphoric acid.
pH ranges for food poisoning bacteria.Organism Minimum Optimum MaximumStaph, aureus 4.0 6.0-7.0 9.8Clostridium perfringens 5.5 7.0 8.0Listeria monocytogenes 4.1 6.0 – 8.0 9.6Samlonella spp 4.05 7.0 9.0
Vibro parahaemolyticus 4.8 7.0 11.0Bacillus cereus 4.9 7.0 9.3Campylobacter 4.9 7.0 9.0Yersinia 4.6 7.0-8.0 9.0Clostridium botulinum 4.2 7.0 9.0
2. Water activityWater in the liquid state is essential for the existence of all living organisms. The
cells of living organisms have very high water content, i.e., more than 75%. The amount of water is required to maintain the cell in an active state, and without liquid water living organisms, including micro-organisms, will not grow or reproduced.
The ways in which water can become unavailable for growth are: The water contains dissolved solute such as sugar or salts. The water is crystallized as ice. The water is present as water of crystallization or hydration. The water is absorbed on to surface (matrix effects).
The amount of water available for microbial growth in terms of the water activity is the amount of water
available in a food(or other materials) for microbial growth. More precisely:
Vapour pressure of a substance or solution Water activity = ------------------------------------------------------------
Vapour pressure of water at the same temperature
The amount of water available to microorganisms in foods is normally indicated in terms of water
Activity the water content is referred to as Equilibrium relative humidity (ERH) atmosphere above a food at equilibrium with the food and is equal to the aw X 100%. Raoult’s law be used to calculate the water activities.THE WATER ACTIVITY OF FOODS:-
The water content of a food may be bare little relationship to its water activity. Fresh meat, for example, has a water content of 75% but a water activity of 0.98. Muscle protein and fat are the bulk of the solids present. These are not soluble in water, have little surface effect and therefore do not contribute in any major way to the water activity. Water soluble materials (glucose, amino acids, mineral salts and vitamins) are present in such small quantities that the water activity of fresh meat is very high.
Foods may have low salt content but low water activity.THE EFFECT OF WATER ACTIVITY ON MICRO-ORGANISMS:-According to Raoult’s law:
naw = ------------
N + n
Where n is the number of moles of solute and N the number of moles of solvent (water)Another, more useful way of writing the equation is :
Xerophiles (Organism loving dry conditions). This term applied specifically to a group of moulds (Xerophilic moulds) that can grow under very dry conditions, i.e., environments with water activities as low as 0.61. They will not grow at water activities higher than about 0.96 and their optimum water activity is in the region of 0.9 – 0.85. These organisms can cause spoilage of dries and salted fish, for example, the mould Xeromyces bisporus.
Halophiles (Salt-loving organisms). a. Moderate halophiles are organisms that require sodium chloride but will grow only at
moderate concentrations, i.e. between 1 and 10% Sodium ions are believed to be involved with the transport mechanisms associated with the cell membrane and the uptake of materials from the environment. For example, Vibrio parahaemolyticus, 1-8% sodium chloride.
Effect of water activity on microorganisms:b. Extreme halpohiles are organisms that will
only grow at high sodium chloride concentrations. Unlike most other bacteria, their cell walls are made of protein. Na + ions appear to form ionic bonds that maintain the stability of these proteins and therefore the structure of the wall. At high salt concentrations the cell wall is rigid and the cells take on a cylindrical shape. As the concentration of Na+ in the environment decreases the cell shape becomes more and more rounded until the cell wall disintegrates and the cells lyse. This happens when the sodium chloride concentration in the environment reaches about 12% Halobacterium Salinarum is associated with the spoilage of salted fish.
Halotolerant (haloduric) organisms: These organisms are able to grow at high sodium chloride concentration but do not have a specific requirement for sodium chloride like the halophiles.Example:- Staphylococcus aureus can grow at sodium chloride concentrations as high as 20%(aw 0.83). Pediococcus halophilus can grow at 20% sodium chloride (aw 0.83)
Osmophilic yeasts:- ( yeasts loving high osmotic pressures) certain yeast that will grow where the water activity is low. Example:- Saccharomyces rouxii (Zygosaccharomyces rouxii) will grow at sugar concentration of 70% and above (aw 0.62).Saccharomyces rouxii can be responsible for the spoilage of foods with high sugar concentrations, eg., soft-centered chocolates.
Osmotolerant organisms:-This terms is applied to organisms (mainly yeasts) that grow best at high water activities but are also tolerant of high sugar concentration can grow at sugar concentrations of 60% and above.
The effect of water activity on the growth curve isProduces a slower growth rate;Increases the length of the lag phase;
Causes the production of fewer cells when the stationary phase starts; Causes cells to die more rapidly during the death phase. Principle groups of foods and their water activity
S. No Aw valve Food involved S. No Aw valve Food involved
1 0.98 and above
Fresh meat and fishFish fruits and vegetablesMilk and most beveragesCanned vegetables in brineCanned fruits in light syrup
4 0.60-0.85
Dried fruitsFlourCerealsJams and jelliesNutsSome aged cheeseIntermediate moisture foods
2 0.93-0.98
Evaporated milk Tomato pasteProcessed cheeseBreadCanned cured meatsFermented sausageCanned fruits in heavy syrupGouda cheese
5 Below 0.60
ChocolateHoneyBiscuitsCrackersPotato chipsDried eggsMilk and vegetables
3 0.85-0.93
Dry or fermented sausageDried beefRaw hamAged cheddar cheeseSweetened condensed milk
Factors affecting the water activity of foods:1. Kinds of solute:
Gel à aW increases. Sugar à aW decreases
2. Nutritive value of food: The better the medium for growth the lowest the limiting aw.
3. Temperature: Temperature increases à aW decreases Temperature decreases à aW increases
4. Oxygen supply: Oxygen increases à aW increases Oxygen decreases à aW decreases
5. pH: pH decreases and aW increases à survive pH decreases and aW decreases à organism donot survive.
6. Inhibitors: Salt / sugar concentration inhibits aW. Water tie up with ions so aW decreases. Organism donot survive due to osmosis.
3.Oxidation – reduction potential:
Oxidation reduction potential or redox potential (OR or Eh) is a measure of whether microbial/material has a tendency to gain electrons 9become reduced) or lose electrons (become oxidized).
Microorganisms vary in their requirement for oxygen and their response to the presence of oxygen in the environment.
1. Aerobic -Requires oxygen in order to generate cellular energy in the form of ATP.
2. Anaerobic:(negative Eh values) - Generate cellular energy without oxygen.
3. Obligate aerobe: (positive Eh value) Requires oxygen for growth.Energy production is by glycolysis, Kreb’s cycle.Organic substrate oxidize to give CO2 and H2O (38 ATP).Eg: Pseudomanas fluorescens, Penicillium sp., Pichia sp., Hansenula sp..
4. Microaerophiles :Requires oxygen in minimum quantity eg. Campylobacter sp.1 –
10%, Optimum – 6%Oxygen concentration above 10% is toxic & kills the organism.
5. Facultative anaerobes:Grows in the absence of oxygen. Energy production is by
glycolysis, Kreb’s cycle Eg. Saccharomyces cerevisiae produces 38 ATP. Eg. for food poisoning bacteria – S. aureus, E.coli.
6. Obligate anaerobes:Donot require oxygen eg. Clostridium botulinum, Cl. perfringens.
Redox of foods & Microbial growth:The actual redox of food will depend on a number of factors :
1. the oxygen concentration in the environment of the food & its access to the food.
2. Density of the food structure, which affects the ability of oxygen in the environment to penetrate.
3. Concentration & types of reducing substances in the food that resist changes in redox towards the positive. Resistance to change in redox in a food is known as poising capacity.
4. The way in which the food is processed.5. The pH of food. For every unit decrease in pH the Eh increases +58mV.
The surface of solid foods in contact with the air will have a positive redox whereas the interior may be negative.Eg. Carcass meat à exterior - +ve200 mV [aerobes, facultative anaerobes]
Interior - -ve150mV Processing & mixing may alter the redox Eg. Milk during milking &
processing [microaerophiles] Heating drives off oxygen & may increase quantity of reducing
substances in a food.
Eg. Canned foods à negative redox (obligate anaerobes, facultative anaerobes, oxygen independent organism).
Spoilage of canned foods à Eg. Rhizopus sp. Byssochlamys fulva .4. Nutrient content:
These are based on : Foods for energy – Carbohydrates, Fats, Proteins, Esters, Alcohols, Peptides,
Aminoacids, organic acids. Foods for growth _ Nitrogen containing foods. Accessory food substances or vitamins.
5. Inhibitory substances & Biological structure: Generally foods have some inhibitors: Eg. Freshly drawn milk – Lactinins, Anticoliform factors. Egg white – Lyzosyme. Canberries – Benzoic acid Propionibacterium – Propionic acid in Swiss cheese inhibits molds. Streptococcus lactis – Nisin which inhibits lactate fermenting organism.
Lactobacillus inactivates nisin.. Yeast – Resistant to SO2
Heating lipids leads to autooxidation & concentrated sugar syrups during browning results in production of furfural & hydroxy methyl furfural which are inhibitory to fermenting organisms.
Food has certain shell / outer covering which prevents the entry of organisms called as biological structures. Eg. Egg shell (vitelline) , Fish[scales], Fruits & vegetables[outer skin].
EXTRINSIC FACTORS:The extrinsic parameters of those properties of the storage environment that affect both
the foods and their microorganisms.1. Temperature:-
Micro organisms are capable of active growth at temperatures well below freezing to temperatures above 1000c.But each individual species has a far more restricted temperature range in which it can grow. The range is determined largely by the influence that temperature has on cell membranes and enzymes and, for a particular organisms, growth is restricted to those temperature at which its cellular enzymes and membranes can function.
The relationship between growth rate and temperature for many microorganisms can be is illustrated.
A is the minimum temperature, i.e., the temperature below which no growth occurs. At temperatures below the minimum, the properties of cell membrane change so that they can no longer transport materials into the cell.
B is the optimum temperature, i.e., the temperature at which the organisms grows at its fastest rate.
C is the maximum temperature, i.e., the temperature above which no growth occurs. At temperature above the maximum enzymes become denatured and cease to catalyze essential cell reactions. These temperatures also damage the proteins and lipids in the cell membrane,
which cease to function normally. So membrane collapse and the cell breakdown (thermal lysis).
The Cardinal temperature for Escherichia coli is
Minimum : 8oC Optimum : 28oC Maximum: 47oCThe minimum and maximum temperatures for growth normally quoted for an organisms depend on the Other factors that influence growth also operating at an optimum, e.g., pH and water activity. If these environmental factors move way from the optimum then the minimum temperature for growth will increase and the maximum temperature decrease. For example,The minimum growth temperature for the food poisoning organism Staphylococcus aureus is 6.7oC and the maximum 48oC when the organism is grown at the optimum ph of 7.0 and optimum water activity of 0.99. if the pH of the environment is reduced to pH 5.0 and the water activity reduced by the addition of 3.0% sodium chloride to the growth medium, then the organism will no longer grow at 48’C and the minimum temperature is increased to 30’C
On the basis of their cardinal temperatures for growth, microorganisms can be divided into five groups:
Mesophiles Obligate psychrophiles Psychrotrophs Thermophiles Extreme thermophiles
Some microbiologist in factor, recognize a sixth category; facultative thermopiles, i.e., organisms that
have an optimum in the mesophilic zone but can grow well into the zone in which thermopiles grow rapidly.
Groups of Microorganisms based on growth temperatures.
Group Minimum0C Optimum oC Maximum oC
Obligate psychrophiles -10 10-15 20
Pshychrotophy -10 20-30 42
Mesophile 5 28-43 52
Thermophile 30 50-65 70
Extreme thermophile 65 80-90 100
Mesophiles (organisms adapted to growth in the middle Temperature Zone)
Adaptation man and other warm-blooded animals, and water in tropical and temperature climates. An important characteristic of mesophiles is their lack of ability to growth at chill temperature (-1 to 5’C).
Example:- Bacteria, Yeasts & moulds
Many food spoilage organisms are also mesophilic.
Temperatures for toxin production by Staphylococcus aureusObligate psychrophiles(cold loving organisms)
Adaptations=> Arctic and Antartic Oceans, and land masses where temperatures are low throughout the year(land below 0’C and oceans 1-5’C).
Example:-Flavobacterium
PSYCHROTROPHS(ORGANISMS FEEDING AT LOW TEMPERATURE)
Adaptation => water and soil in temperate climate(relatively high summer temperatures and low winter temperatures). Minimum temperatures recorded for bacteria in this group are as low as –6.5 oC (Pseudomonas fragii), - 10 oC(moulds) and –12.5 oC( the yeast Debariomyces hansenni).
Psychrotrophs are called facultive psychrophiles, referring to psychrophiles with the ability to grow at relatively high temperatures.
Psychrotrophs are a very important group of organisms causing the spoilage of foods hed at chill temperatures either on melting ice or in the refrigerator.
BACTERIA YEAST MOULDSPseudomonas Candida Penicillium
Alteromonas Torulopsis Aspergillus
Shewanella Saccharomyces Cladosporium
Bacillus Debariomyces Botrytis
Clostridium Rhodotorula Alternaria
Lactobacillus Trichosporon.
In psychrotrophs, a higher amount of unsaturated fatty acid appears to maintain the plasma membrane in a liquid and mobile state at temperature below 5 oC. This ensures that the membrane is biologically active and capable of absorbing nutrients at low temperature.
THERMOPHILES(ORGANISMS LOVING HIGH TEMPERATURES)
Thermophiles are active in soils heated by sunlight compost heaps and silage, where the temperature can reach as high as 70 0C. Thermophiles are responsible for the spontaneous combustion of straw and hay. When the hay becomes damp, mesophiles grow; their metabolic processes generate heat and, because of the high level of insulation in the stack, the temperature moves up into the thermophilic zone .Growth of thermopiles takes over, increasing the temperature even further (up to 70 0C plus), when chemical oxidation causes the stack to spontaneously combust.
Few thermophiles have any significance in foods. Bacillus stearothermophilus, Clostridium thermosaccharolyticum and desulfotomaculum nigrificans(Clostridium nigrificans) are bacteria that cause the spoilage of canned foods stored at elevated temperatures that allow thermophiles to grow.
Three factors seems to be involved:
The cell membrane of thermophiles are abnormally stable because of a high content of saturated fats.
Cells proteins, including enzymes, are unusually heat stable. The ribosomes are heat stable.
What effect does temperature have on the lag phase of growth?
Temperature has a very important effect on the lag phase of growth. As the temperature moves towards the minimum, not only dies growth rate decrease but the length of the lag phase increases. This has important consequence in relation to the preservation of foods at chill temperatures. The increase in storage life of foods held at chill temperature is associated not only with a decrease in the growth rate of spoilage organisms but also in an extension of the lag phase, when the population is not increasing in size. This increase in the length of the lag phase may be as important as decrease in growth rate. The effect of temperature on length of the lag phase and the rate of growth of psychrotroph is illustrated. The effect is not linear. A psychrotroph having a lag phase of 1 hour at its optimum(25 0C) may have lag phase of 30 hours at 5 oC and 60 hours at 0 oC. At temperatures very close to the minimum, lad phases may become very long indeed; 414 days has been recorded for some organisms.
CHILLING INJURY:-Microbial cells can be damages when they are cooled from ambient to chill
temperatures, a phenomenon known as chilling injury. There are two types of chilling injury. Cold shock (Direct chilling injury) is associated with the process of cooling foods
from ambient temperature to chill temperature. The level of injury depends on the rate at which the food is cooled. More cell damage occurs at slow rates of cooling than with fast rates. This type of damage seems to be caused by changes in the structure of the cell membrane resulting in the leakage of important cell metabolites, e.g., amino
acids and ATP from the cell. Actively growth cells are more susceptible than stationary phase cells.
Indirect chilling injury is associated with holding food at chill temperatures for prolonged periods(several days) and is independent of the rate at which the food has been cooled, this type of injury seems to be caused by lack of exchange of materials with the environment leading to the accumulation of toxic metabolic products and/or the depletion of important cell metabolites such as ATP resulting in cell starvation and, eventually, death.
Example:- Salmonella Sp.
How does Freezing cause cell injury and death?Cells injury death caused by freezing depends on the cooling rate as follows:
Slow freezing. When cooling is slow (freezing rates that occurs in domestic freezers) ice crystals from outside the
cell. This causes an increase in the concentration of solute in the environment outside the cell followed by plasmolysis, cell shrinkage and eventually death. There is no evidence hat any mechanical damage is associated with the formation of ice crystals outside the cell. This type of freezing damage is the most lethal. Fast freezing:-
When cooling is fast (freezing rates used in the food industry) ice crystals form inside cells. The
mechanism by which fast freezing causes damage is not well understood but possibilities are:1. Mechanical damage to cell membranes and DND molecules cause by ice crystals;2. An increase in the concentration of internal cell solutes leading to pH changes and an
increase in ionic strength which in turn damage cell protein and nucleic acids;3. Formation of gas bubbles during thawing which cause mechanical damage to cell
membranes. Ultra fast freezing:-
When cooling is ultra fast (freezing rate produced by plunging cells into liquid nitrogen at –196’C)
water freezes to form a glass-like substance and the formation of damaging intracellular ice crystals is reduced. Cell damage is minimized and most of the injury to cells appears to be associated with thawing rather than the freezing process.
WHAT HAPPENS TO INJURED CELLS AFTER THAWING?Cells that are injured but not killed can recover after thawing as long as there is an ample
supply of nutrients (damaged organisms often have growth factor requirements that are not normally evident) and the environment does not contain inhibitors. Injured cells will recover quite readily in thawed foods. Cells of food poisoning organisms that are injured rather than killed
2. RELATIVE HUMIDITY OF ENVIRONMENT :
The Rh of the storage environment is important both from the aw within foods & the growth of microorganisms at the surfaces. When the aw of a food is set at 0.60, it is important that this food be stored under conditions of Rh that do not allow the food to pick up moisture from the air & thereby increase its own surface & subsurface aw to a point where microbial growth can occur. When foods with low aw values are placed in environments of high Rh the foods pick up moisture until equilibrium has been established.
Likewise, foods with a high aw lose moisture when placed in an environment of low Rh. There is a relationship between Rh & temperature that should be borne in mind in selecting proper storage of foods. In general, the higher the temperature is, the lower is the Rh & viceversa.
Foods that undergo surface spoilage from moulds, yeasts & certain bacteria should be stored under conditions of low Rh. Improperly wrapped meats such as whole chickens & beef cuts tend to suffer surface in the refrigerator much before deep spoilage occurs, due to the generally high Rh of the refrigerator & the fact that the meat spoilage flora is essentially aerobic in nature, the changes of surface spoilage in certain foods by storing under low conditions of Rh, it should be remembered that the food itself will lose moisture to the atmosphere under such conditions & thereby become undesirable.
In selecting the proper environmental conditions of Rh, consideration must be given to both the possibility of surface growth & the desirable quality to be maintained in the foods. By altering the gaseous atmosphere, it is possible to retard surface spoilage without lowering Rh.
3. PRESENCE AND CONCENTRATION OF GASES IN THE ENVIRONMENT :
The storage of food in atmosphere containing increased amounts of CO2 upto about 10% is referred to as controlled atmosphere [CA] or modified atmosphere [NA] storage. Usage of this is employed in many countries with apples & pears. The concentration of CO2 generally does not exceed 10% & is applied either from mechanical sources or by use of dry ice (solid CO2).
CO2 has been shown to retard fungal rotting of fruits caused by a large variety of fungi. The mechanism is unknown, but it acts as a competitive inhibitor of ethylene action. Ethylene seems to act as a senescence factor in fruits, and its inhibition would
have the effect of maintaining a fruit in a better state of natural resistance to fungal invasion. Ozone added to food storage environments has a preservative effect on certain
foods. At levels of several parts per million, this has been tried with several foods and
found to be effective against spoilage microorganisms. It is a strong oxidizing agent; it should not be used on high lipid content foods,
since it would cause an increase in rancidity. Both CO2 ozone are effective in retarding the surface spoilage of beef quarters
under long term storage.5.Explain about the contamination and spoilage of vegetables and fruits.
Introduction:
Spoiled food may be defined as food that has been damaged or injured so as to make it undesirable for human use.
Food spoilage may be caused by insect damage, physical injury of various kinds such as bruising and freezing, enzyme activity, or microorganisms.
It was estimated that 20 % of all fruits and vegetables harvested for human consumption are lost through microbial spoilage by one or more of 250-market diseases.
Vegetables and fruits are fresh, dry, frozen, fermented, pasteurized or canned.Contamination:
1. During harvesting => boxes, lugs, baskets, trucks, containers.2. Soil3. During transportation.4. Mechanical damage => processing / trimming5. Washing preliminary soaking distribute spoilage organisms.
a. Re-circulated or reused water may add micro organisms (washing with detergent/ germicidal solution reduce number of micro organisms).
Storage containers / bins Handling Spray water and ice growth of psychographs Equipment tables, blanches, press, filters, cloth, wooden surface.
General microbiological profile of harvested fruits and vegetables:Vegetables: Fruits:
Some microorganisms involved in the spoilage of fresh vegetables.
Bacteria Microorganisms Vegetables SymptomCorynebacterium sepedonicum Potato Ring rot of tuberPseudomonas solanaceanum Potato Soft rotErwinia carotovoraVar.atroseptica
Potato Soft rot
Streptomyces scabies Potato ScabXanthomonas campestris Brassicas Black rotFungi Botrytis cinerea Many Grey mouldBotrytis allii Onions Neck rot
Molds BacteriaFusarium, Alternaria, Aureobasidium, Penicillium, Sclerotinia, Botrytis, Rhizopus
Pseudomonas, Alcaligenes Erwinia AnthomonasMicrococci BacillusLactic acid bacteria Corynebacterium.
Molds BacteriaCladosporium Phoma TrichodermaAnd above organisms.
Pseudomonas, Alcaligenes Erwinia AnthomonasMicrococci BacillusLactic acid bacteria Corynebacterium
Mycocentrospora acerina Carrots Liquorice rotTrichothecium roseum Tomato
CucurbitsPink rot
Fusarium coeruleum Potato Dry rotAspergillus alliaceus Onion
GarlicBlack rot
Preservation of vegetables:1. Asepsis sanitization of equipments.2. Removal of microbes washing chlorinated water, lye solution, and
detergents.3. Blanching / trimming / blanching washing with hot water at 90-100c,
inactivate food enzymes and surface sterilization).4. Heat canning5. Chilling cold water i.e., refrigerator, vaccum cooling
Hydro cooling cold H2O spray Controlled atmosphere Co2 / ozone. Eg potatoes 2.2 to 4.4
c6. Freezing survival of Micrococus, Achromobacter, Enterobacter, spores of
Clostridium and Bacillus.7. Drying explosive puffing
Small pieces of diced partially dehydrated vegetables are placed in a closed rotating chamber.
Heat applied, chamber is pressurized to a pre-determined level
Pressure is released instantaneously
Results internal loss of water
Increased porosity simplifies further drying8. Preservative rutabagas and turpips are parafinned.
o Lettuce, beets, spinach => ZnCo3 (to prevent mold).o Controls Fusarium on potato => biphenyl vapours, Co2 and ozone used.o Saueskraut / cauliflower / lemon => Nacl (2.25 to 2.5%)
High protein vegetable => Nacl (18.6 to 21.2%)o Brine solutiono Salad freshers => sulfiteso Sugars
9. Irradiation gamma radiation (insect) – potato, onion, garlic.Preservation of fruits:
1. Asepsis2. Removal of microbes => trimming3. Use of heat => blanching, canning=> fruit juices
Low PH food => tomatoes, pears, pineapple.High PH food => berries
4. Use of low TChilling => before chilling – propionate, borax, NaHCo3, biphenyl phenols, orthophenyl phenols, hypochloride, So2, thiourea, thiobendazole, dibromotetra chloroethane added to avoid shrinking and surface sterilization occurs.
5. Controlled atmosphere =>increases Co2 and decrease O2 content (Co2 storage) to prevent molds).
6. Modified atmosphere => 100% N2 (N2 gas storage). Co2 storage apples, citrus, grapes, pears, plums,banana peaches Ozone 2-3 ppm (strawberries, grapes, raspberries) Ethylene ripening (color Changes)
7. Freezing, drying dehydration, sulfuring, blanching8. Preservative Na, o- phenyl, phenates, waxes, hypochlorites, biphenyl alkaline Wrapper I2, S, biphenyl, O – phenyl phenol + hexamine, ozone, So2.
Spoilage:S.no Kinds of spoilage Organism involved
1Bacterial soft rot(Soft, mushy bad odour)
Erwinia carotovora, Ps.marginatus, clostridium sp, Bacillus sp.
2 Gray mold Botrytis cinera (gray mycelium)3 Rhizopus soft rot R.stolonifer (Soft mushy black dot sporangia)
4 Anthracnose spots of leaves
Collectotfichum lindemuthianum C.coccodes
5 Aiternaria rots Alternaria tenuis (greenish – brown / black spots)6 Blue mold rot Penicillium digitatum (bluish green rot)7 Downy mildew Phytophthora, Bremia (white woody masses)8 Watery soft rot Sclerotinia sclerotium (vegetable)9 Stem end rot Diplodia, atternaria, Fusarium10 Black mold rot Asp,niger (Dark brown – black smut)11 Black rot Alternaria12 Pink mold rot Trichothecium roseum13 Fusarium rot Fusarium14 Green mold rot Cladosporium sp,Trichoderma sp15 Brown rot Sclerotinia sp16 Sliminess / souring Saprophytic bacteria in piled, wet, heating vegetables Fungal spoilage of vegetables often results in water soaked, mushy areas, while
fungal rots of fleshy fruits such as apples, peaches frequently show brown or cream colored areas in which mold mycelia are growing in the tissue below the skin and aerial hyphae and spores may appear.
Some types of fungal spoilage appear as dry rots, where the infected area is dry and hard and often discolored.
Rots of juicy fruits may result in leakage. Molds are favoured due to deficiency in vitamin B. Spoilage may be by;
Damage by mechanical means, plant pathogens or bad handling will favors entrance.
Direct contact with moist soil – roots, tubers or bulbs. eg carrots, beets, radishes, potatoes
Direct contact with surface soil. Eg: strawberries, cucumbers, and peppers.
Spoilage of fruit and vegetable juices:1. Molds can grow on the surface of juices due to high moisture content, acidity, low in sugar.2. The removal of solids from the juices by extraction and sieving raises the oxidation – reduction potential and favors the growth of yeasts.3. Most fruit juices are acid enough and have sufficient sugar to favors the growth of yeasts.4.Deficiency of vitamin B discourages some bacteria.
Yeast / acetic acid5. Fruit juice Alcohol acetic acid
Mold bacteria Lactic acid bacteria
Lactic acid6. Fruit juices undergo changes like;a. LA fermentation of sugars L.pastorianus
L.brevis Leuonostoc mensenteroides (apple or pear juice) Lactobacillus rabinosus L.leichmanii Microbacterium
b. Fermentation of organic acids of juice by LA bacteriai.e, malic acid lactic and succinic acidsquinic acid dehydroshikimic acidsCitric acid lactic and acetic acidsc. Slime production by L.mesenteroides, L.brevis and L.plantarum in apple juice and L.plantarum and streptococci in grape juice.7. Vegetable juices also contain a plentiful supply of accessory growth factors for microorganisms and hence support the good growth of fastidious lactic acid bacteria.8. Acid fermentation of raw vegetable juice by these and other acid forming bacteria causes yeasts and molds to growth.
6.Explain about contamination and spoilage of eggs (poultry products)spoilage
INTRODUCTION The hen’s egg is an excellent example of a product that normally is well protected
by its intrinsic parameters. Externally, a fresh egg has three structure, each of which is effective to some
degree in retarding the entry of microorganismsI. The outer, waxy shell membrane
II. The shell III. The inner shell membrane.
Internally, lysozyme is present in egg white effective against gram-positive bacteria.
CONTAMINATION:1. Faecal.2. Soil3. Cage => shell => gram positive organisms, Salmonella, Streptococcus,
Staphylococcus, Micrococcus, Sarcina, Bacillus, Alcaligenes, Flavobacterium, Proteus, Serratia, Aeromonas, molds, like Penicillium, Mucor.
PRESERVATION:Eggs have some protective barrier;
a. Shell => cuticle / bloom (layer on shell, polished) if cuticle is removed then organism enters.b. Shell membrane.c. Albumin content => anti Proteolysis factor
PH 9 to 13 has lyzozyme Any organism cannot survive It is less dense If org entered yolk means organism survive.
1. Asepsis => equipment sanitize, handling must be care and prevent contamination.2. Removal of microbes => dry cleaning by sandblasting (washing with hot
water)=> removes bloom so not advisable.* Mechanical egg washer;1 % hypochlorite => to sanitize equipment.2% acetic acid => very effective but reduce the size of shell => don’t store, use immediately as bloom removal.
3. Use of heat => heating in water but avoid coagulationi.e, 57.5 C => 800 sec 60 C => 320 sec
Heating in oil => 60c for 1 min 54.4 C for 30 min
Immersion in hot detergent sanitizer 43.3 to 54.4 c Thermo stabilization => slight coagulation of albumin. Pasteurization => before this add Aluminium and salt to adjust PH
4. Use of low T chilling -1.7 to –0.55c with air circulation.Rh is 70 to 8 (6 months)
For this eggs are selected by candlingThis removes
a. Increased air sacb. Infected eggsc. Rotten eggs
Avoid moisture on the shell Impregnation of eggshell with colorless, odorless, oil improves their
quality.Freezing
Rinse 200-500 ppm of Cl2 / I2
Frozen in 30- or –50lb tin can/ container Add 5% sugar / salt/ glycerol before freezing T –17.8 to –20.5 C
Drying Removal of glucose prevent browning / maillard rxn Removal of glucose may be by 1. Fermentation using Group.D stretococci, Enterobacter aerogenes or
Saccharomyces sp. 2. Using the enzyme glucose oxidase at 10cDryers used areSpray dryer, Drum, Rotor, air, pan and tunnel dryer (60-71C) Final moisture content => 5 to 1% was retained Before drying pasteurization was carried out After drying some organisms can act as contaminants from handlers,
equipment or through air and soil. They are Micrococci, str. facealis, coliforms, Salmonella, spore formers and molds.
6. Use of preservative waxing, oiling prevent O2 entry and maintain dry shell.a. Materials used for dry packaging of eggs are salt, lime, and saw dust, sand and ashes.b. Solution of sodium silicate for dipping.c. Others => borates, permanganates, benzoates, salicylates, formats.d. Washing of eggs with hot solution of germicides;
1. Hypo chlorites2. Ly solution3. Acids4. Formalin5. Quaternary ammonium compounds6. Sealing of shells solution of dimethylourea inhibits mold growth.7. Mycostatic sodium pentachlorophenate8. Fumigation gaseous ethylene oxide9. Co2 + ozone (CA) 0.6 pp for clean eggs
1.5 ppm for dirty eggs10. N2 storage.11. – 0.55 C to 90% Rh keeps eggs fresh for 8 months12. Radiation rays is used to prevent salmonella.
Spoilage:1. General appearance.2. Candling with transmitted light.3. Broken egg
These are obvious for spoilage.Defects in fresh egg:
Fresh eggs may have cracks, leaks, loss of bloom or glass, stained or dirty spots on exterior as well as meat spots (blood clots), general bloodiness, or translucent spots in the yolk when candled. From among these, any breaks in the shell or dirt on the egg will favors spoilage on storage.Changes during storage:
1. Microbial.2. Non – microbial
1. Changes due to non- microbial agents:1. Egg breakage.2. Storage of old eggs results in protein denaturation.3. Air sac increased.
2. Changes due to microbes:Bacteria:1 Green rots Pseudomonas. fluorescens
Bright green colour, fruity / Swedish odour, not detected by candling.
2 Colorless rots Pseudomonas, Acinetobacter, Alcaligenes, coliforms.Identified by candling, odour, white incurstation
3 Black rots Proteus, Pseudomonas, Aeromonas, Pr.melanovegenesOdour – H2S, putrid – muddy brown.
4 Pink rots PseudomonasPinkish ppt of yolk
5 Red rots SerratiaMild odour
6 Others Enterobacter, alcaligenes, Escherichia, Flavobacterium, Paracolobacterium
Fungi:1. Pin spot molding:
1. Penicillium yellow / blue / green spot2. Cladosporium dark green / black spot3. Sporotrichum pink spot
2. Superficial fungal spoilage:*Fuzz / whiskers on shell during storage increase RH and no air circulation.Fungal rotten Penicillium, Cladosporium, Sporotrichum, Mucor, Thaminidium, Botrytis, Alternaria.3. Fungal red rot Sporotrichum4. Black rot Cladosporium Achromobacter peolensPseudomonas. graveolenOff flavour / musty odour Pseudomonas. mucidolensBad odour (hay flavour) Enterobacter cloacae (due to faecal contamination)Cabbage water flavour (fishy flavour) E.coli (due to faecal contamination).
7.Explain about contamination and spoilage of meat and meat product.Introduction
Meat are the most perishable of the important foods, in which the chemical composition of a typical adult mammalian muscle postmortem is presented.
Meat contain an abundance of all nutrient required for the growth of bacteria, yeasts,and molds, and an adequate quantity of these constituents exist in fresh meats in available form.
When spoiled meat products are examined, only a few of the many genera of bacteria, molds ,or yeasts are found.
Almost all cases one or more genera are found to be characteristic of the spoilage of a given type of meat product.
Frequently isolated microorganisms from meatS. no Product Microorganisms isolated 1 Fresh and refrigerated meat Bacteria
Acinetobacetr,Moraxella
PseudomonasAeromonasAlcaligenesMicrococcus
Molds CladosporiumGeotrichum
SporotrichumMucor
ThamnidiumYeasts
CandidaTorulopsis
DebaryomycesRhodotorula
2 Processed meat and cured meats
BacteriaLactobacillus and other lactic
acid bacteria.Acinetobacter
BacillusMicrococcus
SerratiaStaphylococcus
MoldsAspergillusPencilliumRhizopus
ThamnidiumYeast Debaryomyces,TorulaTorulopsis,Trichosporoncandida
Contamination:
1. Lymph node (more number of micro organisms) staphylococcus, streptococcus, clostridium, salmonella
2. Flesh => good culture media as it contains protein, carbohydrate, lipids and vitamins.
3. Bleeding, handling, processing (enter – full circulation in body). Skimming, cutting, knife.
4. Hide, hooves, hair5. Soil, H2o, feed, manure, air, wood (slaughter house)6. Intestinal organism coli forms, pathogenic fungi7. Container, boxes8. Meat surface – molds => Cladosporium, Sporotrichum, Geotrichum,
Thamnidium, Mucour, Penicillium.9. Pseudomonas, Acinetobacter, Moraxella, Alcaligenes, Micro cocci,
Flavobacterium, Proteus utensil contamination and salt tolerant Found in meet products.
Characteristics of some Gram negatives associated with meat.Gram negative
Not fermentative in OF medium
Oxidase +ve Oxidase –ve
Motile non motile non motile
Pseudomonas Acinetobacter
(formerly Moraxella) (Achromobacter)
Psychrobacter (formerly Moraxella-like)
Polar flagella
Not oxidase Oxidase in OF medium in OF mediumPseudomonas PseudomonasShewanella (Achromobacter(Alteromonas)Preservation:1. Asepsis:
Sanitation and H2o spray (before cutting) (utensils) After cutting => hot H2O / detergents etc
2. Use of heat:
Canning1. Commercially sterile (Self stable)=> 90C (11 lbs)
Process by increasing heat + Nacl / salt solution
2. Non self stable => stable for some pots (controlled atm) => heat process (65C with 22 lbs) – canning => refrigeration.
3. Use of low T: Chilling:
o -1.4 to –2.2Co Particularly maintained or else spoilage => beef => 30 dayso Pork, lamb, mutton => 1-2 weekso Real (calf meat) => shorter periodo (CA) + Addition of Co2 + ozone => increase Co2 / ozone leads to
formation of metmyoglobin, from myoglobin change the colour.o Co2 10 to 30% for most meet
100% for bacon.o ozone => 2.5 to 3 ppm (92% Rh) => 60 days maintainedo Chilling T => Pseudomonas, Acinetobacter, Moraxiella, Alcaligenes,
Pediococcus cerevisiae, (salt tolerant) => does not effect in curing. Freezing:
-1.22 to –28.9 C (Pseudomonas, Moraxiella, Acinetobacter, Alcaligenes, Micrococcus, Lactobacillus, Flavobacterium, Proteus).
4. Use of radiation:i. UV [air] surface of meat products
ii. rays Depend meat products [Hard Meat – Increase rays]iii. Increase rays – Porkiv. 20 – 70 K-Grays – Normal
5. Drying: Slice & Dried Sodium nitrites – to dry the surface of meat
6. Freeze drying: Meat Products generally are not freeze Bleeding – removal of liquid to outside Freeze burn – Change in colour – brown colour Smoking
7. Curing: Addition of Salt NaCl – 15% salt (immerse meat)
o 24% salt [inject to meat) Preservating & flavouring agent
o à NaNo3 à Colour Fixative [bright red] & bacteriostatic
Increased concentration lead to brown colour Sugar – adds flavour and serves as an energy source for
nitrate – reducing bacteria4 Methods of introduction of curing agents into meat;
1. Dry2. Pickle
3. Injection4. Direct-Addition
Spoilage of Meat: Oxidation occurs Due to protease, lipases
Factors that influence the invasion of Microbes: Load in the gut Physiological condition of animal Method of killing & bleeding Rate of cooling
Aerobic condition influences the growth of bacteria, molds, yeast.Factors that influence the growth of Microbes in Meat:
Kinds of no. of microbes Physical properties of meat Chemical properties of meat à RH, PH [5.7 to 7.4 based on glycogen], chemical
composition of meat. Availability of O2. Temperature Animal pathogen à Salmonella, Camphylobacter, Pseudomonas.
Spoilage under Aerobic Conditions:1. Surface Slime: Pseudomonas, Acinetobacter, Alcaligenes, Moraxella, Streptococcus, Leuconostoc, Bacillus, Micrococcus, Lactobacillus.2. Discolouration of Meat Pigment:
Autolysis also occur Generally meat has heamoglobin; myoglobin due to oxidation produces
metmyoglobin.Meat
Hb, Myoglobin Oxidation Metmyoglobin[Purplish Pink] [Brown]
Blooms i.e., Red à Green / Brown / Grey Oxidizing compounds peroxidase, H2S results in spoilage. Organisms involved may be Lactobacillus sp., Leuconostoc sp and other
heterofermentative organism3. Changes in Fat:
Oxidation of unsaturated fats catalyzed by light & copper Lipolytic organisms à Pseudomonas, Achromobacter yeast Oxidative rancidity (degradation of fat) results in tallowy odour
4. Phosphorescence: Luminous bacteria Photobacterium on the surface of meat
5. Discolouration of meat due to Bacterial Pigment:Red spot Serratia marcesensYellow Micrococcus, Flavobacterium,
Chromobacter lividium
Greenish / Blue / Brownish Black Proteus & others
6. Taint [Off flavour and odour]: By yeast, Actinomycetes results in musty / earthy flavour Yeasts produce acetate, formate, butyrate & propionate.
Aerobic Growth of Molds:1. Stickness2. Whiskers à Thamnidium Chaeotocladioides, T.elegans, Mucor, M.Mucida, M.raceonogus, Rhizopus.3. Black Spot à Cladosporium herbarum4. White Spot à Sporotrichum Carmi5. Green pathches à P.expansum, P.oxalium, P.asperulum.6. Decomposition of Fat7. Taint à Musty flavour à Thaminidium taint by Thaminidium sp.
Spoilage under Anaerobic Conditions:1 Souring Due to formate, acetate, propionate, lactate, succinate
and fatty acids. By clostridium & other facultative anaerobes After protein / fat lysis in aerobic leads to anaerobic
condition2 . Putrefaction Anaerobic decomposition of protein leads to fowl smell
and results in production of H2S, mercaptans, indole, skatole, NH3, amines
Caused by Clostridium and other facultative anaerobes3 Taint Bone Taint à Souring / putrefaction next to bones
Spoilage of Different Kinds of Meat:Fresh Meat:1 Refrigeration Pseudomonas, Actinetobacter, Moraxiella2 Shine form LA bacteria3 Green discolouration Lactobacillus, Leuconostoc4 Souring Streptococcus, Pediococcus, BrevibacteriumFresh Beef:
1. Oxidation of mycoglobin & Hb.2. White, green, black, greenish blue, yellow, brown, black spots.3. Phosphorescence.4. Shine formn à bacteria, yeast5. 10 C Meat à Pseudomonas6. Whisters & Stickiness
Hamburger:1 Putrefaction at RT2 Souring Near freezing3 Low Temperature Pseudomonas, Acinetobacter, Moraxella, Micrococcs,
Flavobacterium, Alcaligenes4 High
TemperatureBacillus, Clostridium, E.coli, Micrococcus, Sarcina, Mucor, Lactobacillus, Leuconostoc, Penicillium, Alcaligenes, Streptococci, Enterobacter, Proteus, Pseudomonas
Fresh Pork Sausage:1 Souring 0 – 11 C
Lactobacillus,Micrococcus, Microbacterium2 Colour spot Molds3 Dark spot Alternaria [on refrigeration]Cured Meat:1 Cured meat Salted Meat [NaCl / NaNo3]2 Nitrite Anaerobic NaNo3 à favours LA bacteria, G+ve orgs, yeasts,
molds.Dried Beef / Beef Hams:1 Factor H2O, Rh2 Spongy Bacillus3 Sour LA bacteria4 . Red Halobacterium salinarium,
Bacillus5 Blue Ps.syncyaneae, Penicillium
spinulosum, Rhodotorula.6 . Gas in jars Pseudomonas.fluorescens7 Co2 in jars Bacillus.
Sausage:Slime à Moisture à Micrococci & Yeasts
à Decrease à Fuzziness discolouration à Molds Sour àLeuconostoc , LactobacillusSwell package à due to Co2 by heterfermentative LA bacteria.
Fading red colour to chalky grey à BacteriaGreening of sausage à Leuconostoc, LactobacillusProduction of Nitric oxide à Nitrate reducing bacteria.Bacon:
Mold à Aspergillus, Alternaria, Mucor, Rhizopus, PenicilliumHam:* Souring à Alcaligenes, Bacillus, Pseudomonas, Lactobacillus, Proteus, Micrococci.* Putrefaction à Odour – Mercaptans, H2S, Amines, Indole.
Refrigerated Packed Meat:* Due to packaging film & Co2 à Pseudomonas, Acinetobacter, Moraxella* Off flavour, shine & putrefaction.8.Explain about contamination and spoilage of fish and seafood.Introduction
Both salt-water and fresh water fish contain comparatively high levels of proteins and other nitrogenous constituents.
The carbohydrate content of these fish is nil. While fat content varies from very low to rather high value depending upon species.
Of particular importance in fresh flesh is the nature of the nitrogenous compounds. the relative percentage of total –N and protein-N are presented from which it can be seen that not all nitrogenous compounds in fish are in the form of proteins.
Among the non-protein nitrogen compounds are the free aminoacids, volatile nitrogen bases such as ammonia and trimethylamine, creatine, taurine, the betaines, uric acid, anserine, carnosine, and histamine.
(CH3) 3 N OTrimethylamine oxide
TMO reductase (CH3) 3 NTrimethylamine
Contamination:1. Flora of fish depends on the waters in which they live.2. Slime that covers the outer surface of fish is Pseudomonas, Aeromonas,
Acinetobacter, Moraxella, Alcaligenes, Micrococcus, Flavobacterium, Corynebacterium, Sarcina, Serratia, Vibrio, and Bacillus.
3. Northern Waters à PsychrophilesTropical Waters à MesophilesFresh Waters à Aeromonas, Lactobacillus, Brevibacterium, Alcaligenes, Streptococcus.
4. Intestine of fish à Alcaligenes, Pseudomonas, Flavobacterium, Vibrio, Bacillus, Clostridium, Escherichia.
1. Boats, boxes, bins, fish houses & fishers become heavily contaminated with three bacteria & transfer them to fish during clearing.
2. Oysters, other shell fish à Pick up organisms from soil & water à Alcaligenes, Flavabacterium, Moraxella, Acinetobacter, G+ve sp. 7. Shrimps, Crabs, Lobsters s à Bacillus, Micrococcus, Pseudomonas, Acinetobacter, Moraxella, Flavobacterium, Alcaligenes, Proteus.Fish and fish products:
Cooked, frozen products
Frozen fish Vacuum packing
Dried fish Fresh fish Canned
Fermented fish Marinades
Cured,smoked fish
Spoilage:1. Autolysis2. Oxdn or bacterial activity
3.Combination of these. Fish flesh is perishable because of this rapid autolysis of fish enzymes and because
of less acid r x n of fish flesh that favours microbial growth. Unsaturated fish oils are susceptible to oxdn. Rigos mortis [stiffness of body after death] is hastened by struggling of the fish,
lack of O2, warm T and is delayed by a low pH and adequate cooling of the fish. Muscle glycogen low pH Lactic acid
BacteriaFactors influencing kind and rate of spoilage:1. Kind of Fish: Flat fish spoil more rapidly than round fish. Flat fish;
i. PH à 5.5 of its fleshii. Oxidation of unsaturated fats
In certain fishes high in trimethylamine oxide soon yield appreciable amounts, of stale-fishy trimethylamine.
2. Condition of Fish when caught: Feedy fish [full of food when caught, more perishable than those with an empty
intestinal tract]. Fish that are exhausted result of struggling, lack of O2 excessive handling spoil more
rapidly.3. Kind and Extent of Contamination of Fish Flesh with Bacteria: Micro organisms may come from mud, H2O, handlers, exterior’s slime and intestinal
content of fish and to enter gills and pass through vascular system and invade the flesh and entry to body cavity.
Greater the load of bacteria leads to easy spoilage of fish.4. Temperature:Coolingà 0 to –1 C5. Use of an Antibiotic Ice / Dip
Evidences of Spoilage:1. Fresh condition à Staleness2. Colour of fish fade, dirty, yellow, brown discoloration3. Shine on skin increases à flaps & grills.4. Eyes sink & shrink, pupil – Cloudy, Cornea – Opaque.
5. Gills turn to a light pink to grayish –yellow colour.6. Softening à Juice Extraction à squeezed àIdentified by the finger.7. Reddish – brown discoloration towards the tail due to oxidation of Hemoglobin.8. By odors.
Normal, fresh, seaweedy odor à Sticky sweet
Stale fishy (trimethylamine)
Ammoniacal
Final putrid (H2S) (Indole & other malodorous compounds)9. Fatty fishy & rancid odors.Bacterial Spoilage:
1. Pseudomonas, Acinetobacter, Moraxella, Flavobacterium à chilling.2. Higher Temperature à Micrococcus, Bacillus.3. atmospheric temperatureà Escherichia, Proteus, Serratia, Sarcina, Clostridium.4. Bacteria on Surface à Penetrate the flesh
N2 and glucose favour growth
[putrescine, cadaverine], lower fatty acids, CHO, H2 and other Sulfides, mercaptans, indole.
Indicative of putrefaction
5. Musty odor / Muddy odor & taste à StreptomycesDiscolouration:
6. Yellow to greenish yellow colours à Ps.fluorescens7. Yellow à Micrococci8. Red / Pink colours à Sarcina, Micrococcus, Bacillus, Yeasts &
molds. 9. Chocolate brown colour à Asporogenous yeast.
Spoilage of Special kinds of Fish & Sea Foods:1. Salt fish
2. Smoked fish
3. Marinated (sour pickled) fish
4. Japanese fish sausage
5. Shell fish
6. Chilled shrimp
Salt tolerant / halophilic bacteria of Serratia, Micrococcus, Bacillus, Alcaligenes, Pseudo.
Molds
Molds (if acidity increases growth favours)
Souring by volatile acid production by Bacilli or to putrefaction
As on fish spoilage
7. Crab meat
8. Ran lobsters
9. Crabs and oysters
Acinetobacter, Moraxella, Vibrio, Increases in Pseudo, increases Flavobacterium, Micrococcus, Bacillus
Chilling à Pseudo, Acinetobacter, MoraxellaHigh T à Proteus
Pseu, Alcaligenes, Flavobacterium, Bacillus
Vibrio, V.parachemolyticusOysters
Kept alive in shell at chilling Temperature. Decompose rapidly when they are dead Not only rich in protein but also in sugars Near freezing spoilage occurs by Pseudomonas,Acinetobacter,
Moraxella, Flavobacterium, Micrococcus. Spoilage called as sourcing (Proteolytic) At high Temperature souring may be result of Fermentation of sugars by coliforms, Streptococcus, Lactobacillus,
yeast to produce acids and a sour odor.o Pink oysters à Asporogenous yeasto Others are Pseu, Serratia, Proteus, Clostridium growth occurs
UNIT-2
‘
1.Explain about preservation of food using high temperatue.PRINCIPLES OF FOOD PRESERVATION
1.Prevention or delay of microbial decomposition:a) By keeping out microorganisms (asepsis).b) By removal of microorganisms (filtration).c) By hindering the growth and activity of microorganisms.
Eg; by low temperature, drying, anaerobic conditions, chemicals.d) By killing the microorganisms.
Eg; by heat or radiation.2. Prevention or delay of self-decomposition of food:
a. By destruction or inactivation of food enzyme. Eg; blanching.b. By prevention or delay of purely chemical reactions. Eg; prevention of oxidation
by means of an antioxidant.3.Prevention of damage because of insects, animals, mechanical causes etc.,METHODS OF PRESERVATION:
1) Asepsis2) Removal of microorganisms.3) Maintenance of anaerobic conditions à eg: in a sealed, evacuated container.4) Use of high temperature.5) Use of low temperature.6) Drying.7) Use of chemical preservative.8) Irradiation.9) Mechanical destruction of microorganisms à grinding, high pressure.
ASEPSIS:1) It refers Combination of two or more of the above methods.2) to keeping out of microorganisms.3) Inner tissues of healthy plants and animals are free of microorganisms, if they are
present leads to initiate the spoilage.4) If there is protective covering the spoilage may be delayed or prevented. Eg; shells of
nuts, skins of fruits and vegetables, husks of ear corn, shells of egg, skin or membranes or fat on meat or fish.
5) The food technologists are concerned with bioburden of microorganisms where they consider both kinds and numbers of microorganisms in food.
6) Packaging of foods is a widely used application of asepsis. Eg; loose carton or wrapping.
7) Dairy industry à concentration is made during milking process, handling.
8) Canning industry à sealing can prevent contamination.9) Meat packaging industry à sanitary methods of slaughter, handling and processing
reduce the load and thus improve the keeping quality of meat or meat products. Intestinal flora must be removed in animals.
REMOVAL OF MICROORGANISMS:Removal of microorganisms may be by;
1) FILTRATION:The liquid is filtered through a previously sterilized bacterioproof filter made of sintered glass,
Diatomaceous earth, unglazed porcelain, membrane pads or similar material and the liquid is forced through by positive or negative pressure. Eg; fruit juices, beer, soft drinks, wine and water. 2) CENTRIFUGATION: (SEDIMENTATION)
It is not very effective. Sedimentation is used in the treatment of drinking water. When centrifugation (clarification) is applied to milk, the main purpose is not to remove bacteria but to take out other suspended materials, although centrifugation at high speeds removes most of the spores.
3) WASHING:It can act as surface sterilization. Eg; removal of soil microorganisms on
the surface is by washing in fruits, vegetables, (cabbage, cucumber) etc. Washing foods may be dangerous if the water adds spoilage organisms or increases the moisture so that the growth of spoilage organisms is encouraged.
1) TRIMMING:Removal of the spoiled particles of a food or discarding spoiled samples is
important. Eg; Trimming the outer leaves of cabbage heads is recommended for the manufacture of sauerkraut.
MAINTENANCE OF ANAEROBIC CONDITIONS: Sealed packaged foods involve anaerobic conditions. Canned foodsà headspace is filled by carbon dioxide or nitrogen where
maintains anaerobic conditions. Anaerobic conditions prevent the growth of aerobes, aerobic spore formers.
PRESERVATION BY USE OF HIGH TEMPERATURE:The killing of microorganism by heat is due to;
1. denaturation of proteins.2. inactivation of enzymes.3. control of metabolism.
FACTORS AFFECTING HEAT RESISTANCE:1.TEMPERATURE-TIME RELATIONSHIP:Time for killing cells or spores under a given set of conditions decreases as the
temperature is increased.EFFECT OF TEMPERATURE OF HEATING ON TIME NEEDED TO KILLSPORES OF FLAT SOUR BACTERIA:
TEMPERATURES TDT IN MINUTES
100105
1200600
110115120125130135
1607019070301
2. INITIAL CONCENTRATION OF SPORES OR CELLS:If spores and cells are in greater amount then there is need of increased heat
treatment to kill them.EFFECT OF INITIAL NUMBERS OF SPORES ON TIME REQUIRED TO KILL THEM:
INITIAL CONCENTRATION OF SPORES (NO./ML)
TDT MIN. AT 1200C
5000500050050
14100908
3.PREVIOUS HISTORY OF THE CELLS OR SPORES:A) CULTURE MEDIUM: Spores are more resistant in soil than medium. Glucose increases the heat resistance. If there is increased sugar concentration, in turn acid production is increased results in
decreased heat resistance. Phosphate and magnesium said to decrease the resistance of bacterial spores.
B) TEMPERATURE OF INCUBATION:As the temperature increases the resistance also increases. Eg; optimum
temperature- highly resistant. Minimum/Maximum temperature – highly sensitive.C) PHASE OF GROWTH/AGE:
Log phase à decreased heat resistant. Lag and stationary phase à increased heat resistant. Immature spores à less resistant than mature ones. First week of storage (some spores) à increase in resistant but later
decrease in resistant. Dry spores à harder to kill than moist spores.
4. CONCENTRATION OF SUBSTRATE:A) MOISTURE CONTENT:
If moisture content is increases it is easy to sterilize while the dried food requires increased temperature.Eg: spores of Bacillus subtilis à in steam 10 min at 1200c, in glycerol 1700c for 30 min.B) pH: Neutral pHà heat resistant (optimum) Acid/alkali pH à heat sensitive (min/max)
Cameron classified the foods into;Low acid foods à pH (above 5.3),eg; ear ,corns, meat, fish, poultry, milk. Heat resistant.Medium acid foods à pH (between 5.3 and 4.5). Eg; spinach, beets, pumpkin.Acid foods à pH (between 4.5 and 3.7). Eg; tomatoes,pears,pineapple.High acid foods à pH (3.7 and below). Eg; berries,sauerkraut. Heat sensitive.C) SUGARS/SALTS:
Due to increased concentration they can be easily destroyed. Antiseptic or germicidal substances in the substrate aid heat
in the destruction of organisms. H2O2 + heat is used to reduce the bacterial content and is the
basis of a process of milk.HEAT RESISTANCE OF MICROORGANISM AND THEIR SPORES:THERMAL DEATH TIME:
It is defined as the time it takes at a certain temperature to kill a stated number of organisms under specified conditions. It is also referred to as the absolute thermal death time to distinguish it from the majority thermal death time for killing most of the cells or spores present.THERMAL DEATH TIME:
Expressed as the rate of killing.THERMAL DEATH POINT:
It is the temperature necessary to kill the entire organism in 10 minutes.
1. HEAT RESISTANCE OF YEASTS AND YEAST SPORES:The resistance of yeasts and their spores to moist heat varies with the
species and even the strain, with the substrate in which they are heated.1. Vegetative cell of ascospores à 5 – 100c for destruction.2. Spores of yeasts à 600c for 10 –15 min but few are resistant.3. No survival à 1000c4. Vegetative yeasts à 50 –580c for 10 – 15 min.5. Yeasts in bread (interior) à 970c
2.. HEAT RESISTANCE OF MOLD AND MOLD SPORES: Most molds and their spores are killed by;
1. Moist heat à 600c in 5 – 10 min.2. Asexual spore are more resistant than ordinary mycelia ( 600c) ie.,5 – 100c rise.3. Aspergillus, Mucor, Penicillium are more resistant to heat.4. Pasteurization kills spores and vegetative cells.5. Sclerotia are difficult to kill by heat and they can survive at 90- 100 0c to spoil
canned fruits. They can be killed at 1000 min at 830c or 300 min at 850c.6. Mold spores are resistant to dry heat.
3.HEAT RESISTANCE OF BACTERIA AND BACTERIAL SPORES:1. Cocci are more resistant than rods.2. Higher the optimal and maximal temperature of growth, greater the resistance to
heat.3. Capsule is difficult to kill.
4. Cells high in lipid content are harder to kill.
ORGANISM T0 WITH TIMEBacillus anthracisB.subtilisCl.botulinumCl.calidotoleranceN.gonorrhoeaSalmonella typhi
1000c for 1.7 min1000c for 15-20 min1000c for 100 – 330 min1000c for 520 min500c for 2- 3 min600c for 4.3 min
4.HEAT RESISTANCE OF ENZYMES:1. Enzymes are inactivated at 79.40c for 10 min.2. Pasteurization of milk can be checked by the presence of
bovine phosphatase. If this enzyme is observed then the process was not carried out properly is understood.
2.write a short notes on Heat pentration in food substance.
Heat penetration:
The rate of penetration of heat into a food must be known in order to calculate the thermal process necessary for its preservation. Every part of the food in a can must have to obtain the adequate heat treatments to prevent spoilage may be by
1. Conduction – near the center (slow in food, rapid in metals)
2. Convection – heat passes from molecules to molecule.
When solid particles of food are suspended in a liquid, the particles heat by conduction and liquid heats by convection.
Factors involved are:
1. The material of which the container is made.
2. The size and shape of the container.
3. Initial temperature of the food.
4. Retort temperature.
5. Consistency of can contents and size and shape of pieces.
a. Pieces that retain their identity.
b. Pieces that cook apart and become mushy or viscous.
c. Pieces that layer.
6. Rotation and agitation.
Methods involved:
a. Below 100C
b. At 100 C
c. Above 100 C
Pasteurization:
Pasteurization is a heat treatment that kills part but not all of the microorganisms present and usually involves the application of temperature below 100C.1. When more vigorous heat treatments might harm the quality of the product. E.g.: market milk.
2. To kill pathogens. E.g. market milk.
3. Main spoilage organisms are not very heat resistant.
E.g.: yeast in fruit juices.
4. When process requires additional chilling.
5. When competing organisms are to be killed, allowing desired fermentations, usually by added starter organisms. E.g.: cheese making.
Preservative methods used to supplement pasteurization include;
1. Refrigeration.
2. Asepsis.
3. Maintenance of anaerobic conditions.
4. Addition of high concentration of sugar. E.g.: sweet condensed milk.
5. Addition of chemical preservative. E.g.: Pickles
1.Pasteurization time and temperature:
1. Milk Low temperature / long time
LTH / [holding] 62.8C for 30 min
High temperature short time
[HTST] 71.7C for 15 sec
Ultra pasteurization 137.8 C for 2 sec
2. Ice cream mix LTH 71.7 C for 30 min
HTST 82.2 C for 16-20 sec
3. Grape wine 82 –85 C for 1 min
4. Fruit wine 62.8 C for 30 min
5. Beer 60 C for 15 min
6. Dried food 85 C for 30 –90 min
7. Bottled grade juice 76.6 C for 30 min
8. Bottled apple juice 60 C for 15 min
9. Bulk apple juice 85-87.8 C for 30-60 sec
10 Vinegar 65.6 C for 30 min
If pasteurization is not proper, then there is the presence of enzyme bovine phosphatase. Q fever may be transmitted by milk.
2. Heating at 100 C:
1. Boiling
2. Blanching:
It is process where fresh vegetables before freezing or drying involves heating at about 100 C.
3. Baking:
The internal temperature of break, cake or other bakery products approaches but never reaches 100 C as long as moisture is present.
4. Simmering:
Simmering is gentle boiling with the temperature about 100 C.
5. Roasting:
In meat, the internal temperature reaches only about 60 C in rare beef, up to 80C in well-done beef, 85 D in a pork roast.
6. Frying:
The outside of the food very hot, but the center ordinarily does not reach 100 C.
7. Cooking:
Cook implies a specific time and temperature for a thermal process.
8. Warming up:
A small increase in temperature up to heating to 100 C.
3.Heating above 100C:
Milk can be heated to temperatures up to 150C by use of steam infection or steam infusion followed by flash evaporation of the condensed steam and rapid cooling. This is referred to as UHT processes.Canning / appertization:
Canning is defined as the preservation of foods in sealed containers and usually implies heat treatment as the principal factor in the prevention of spoilage. Canning is the general term and is replaced by hermetically sealed containers. Nicolas appert has been called the “Father of canning”.
Cans:
1. Initially glass vessels are used.
2. Later metals, plastics are used.
3. Corks were also used.
4. Recently cans are made of tin.
5. Enamels are coated on to flat sheets of plate before the manufacturer of cans to prevent or slow discoloration or corrosion.
6. Aluminum parts are used for products that do not require high vacuums or high -T processing. E.g.: Beer, foreign fruits, cheese.
7. Plastic flexible pouches or bags are used or plastic laminated with foil are employed mostly for packaging frozen, dried or unprocessed foods. They are also used for foods that can be packaged hot, although steam – pressure sterilization of foods in pouches has been accomplished.
E.g.: Jams, dried food products.
8. Tin cans were first used by Peter Durand.
Food has sulphur and tin has Fe combine to form FeS. Standard enamel is used for cans for highly colored fruits and berries or for beets to prevent the fading of colour caused by tin plate. Enamels are coated with Zno, so that the white ZnSo4 is formed instead of dark FeS, When low acid, sulfur – bearing foods such as corn as canned and darkening of the interior of the can be avoided.
Meat, fat-containing foods should not be stored in cans containing Zno as they split the fats. Special enamels may be employed for certain products. E.g.: milk, meat, wine, beer, soups and some fruit juices.
Food => Remove the spoiled food by trimming => wash with sterile water (Surface sterilization)
Blanching / steam sterilization and cooling
Blanching sets the colour, softens the tissues and kills some microbes
Add sugar / salt solution
Evacuated before sealing
Usually by heating headspace / unfilled part of the container by mechanical means.
Canned food (commercially sterile or practically sterile or bacterially inactive)
Other methods:
1. HTST
2. HC7 / Heat cool fill method.
3. Steam pressure E.g. Tomato juice may be presterilised at 121 C to 132 C to kill spores of B. coagulants before canning and then the sealed cans of juice are given a milder heating.
4. SC / Sterilizing and closing.
5. PFC / Pressure filler cooker.
6. Dehydrocanning.
E.g.: apple slices, food is dried to about half its original weight before canning.
7. Direct gas flame.
8. Steam injection.
9. Flash 18
10. Addition of preservation / irradiation / chemicals.
Pressurized packaged foods / aerosols:
They are packed under pressure of a propellant gas, usually
1. Co2 => inhibits many microbes => aerobic bacteria and molds not lactic acid bacteria. E.g. B. coagulans, Strep. facelis or yeasts.
2. N2 => inhibit anaerobes not aerobes.
3. Nitrous oxide = represses fungi.
E.g.: whipped cream, beverage toppings, salad dressings, oils, and jellies.
Cooling process:
The cans may be cooled by
1. Immersion in cold water.
2. Spray of water.
3. Large cans are cooled slowly to avoid strain or breakage.
4. By means of air currents.
Canning in the home:
1. Boiling
2. Steam pressure
3. Micro over
4. Cold pack method => not for vegetables and meats.
3.write short notes on preservation of food using low temperatue?
PRESERVATION BY USE OF LOW TEMPERATURE
Low temperature preservation is used commonly to retard chemical reactions and action of food enzymes. Therefore there is a gradual decrease in the activity of microorganism and also the spoilage of food.
The growth and metabolic reaction of microorganisms depend upon the enzymes and the rate of enzyme reactions directly affected by temperature.
During low temperature metabolic activity is arrested. Food enzymes are inactivated.
Low temperature methods:
1. Chilling / cold storage.
2. Freezing / frozen storage.
3. Freeze during / Lyophilization.
Chilling / cold storage:
1. It involves cooling by ice or by mechanical refrigeration.
2. It is used to prevent the growth and reduce the metabolic activity of microbe.
3. Temperature is 0 –15C.
4. Ice crystals can be used to store fish, meat during transportation.
5. Use of mechanical refrigerator. E.g. food storage in industry.
Factors:
1. Temperature:
Lower the temperature of storage, the greater the cost. The temperature is selected on the basis of
1. Kind of food.
2. Time.
3. Condition of storage. Certain foods have an optimal storage temperature or range of temperature well above the freezing point and may be damaged by lower temperature.
E.g.: banana should be kept in the refrigerator, best at about 13.3 to 16.7C.
2. RH:
The optimal Rh depends on the temperature, composition of the atmosphere, ray treatments.
Low RH => loss of moisture and hence weight, witting and softening of vegetables and shrinkage of fruits.
High RH => growth of spoilage microorganisms.
E.g.: yeast => 90 –92%
Molds => 85 –90%
Changes in RH and T during storage may cause sweating or precipitation of moisture on the food, so favors microbial spoilage. E.g.: slime on the moist surface of sausage.
3. Ventilation:
To prevent the development of stale odors and flavors, and maintain uniform RH throughout the room. It adequate ventilation is not provided; food in local areas of high humidity may undergo microbial decomposition.
4. Composition of storage atmosphere:
It is controlled by the introduction of Co2, ozone or other gases called as gas storage.
1. Food remains unspoiled for a longer period.
2. Rh may be maintained.
3. Keeping quality is maintained.
4. Higher storage temperature can be used without shortening the keeping time of food eg. Optimal CO2 concentration.
Eggs à 2.5 %, Beef à 10%, Bacon à 100%, Apples à concentration of O2 and CO2 is significant.
5. Irradiation :
UV lamps have been installed in rooms for the storage of meat & cheese.
Freezing / Frozen storage :
The selection & preparation of foods for freezing – fruits & vegetables are selected on the basis of their suitability for freezing & their maturity & are washed, trimming, cut vegetables are scalded/ blanched & fruits may be packed in a syrup.
Meats are selected to minimize enzymatic & microbial changes. Most foods are packaged before freezing, but some foods in small pieces. E.g. Strawberries may be frozen before package.
Scalding or blanching is done:
1. Inactivation of plant enzymes that involve toughness.2. Reduction in microorganisms of the food.3. enhancement of green color 4. wilting of leafy vegetables making them pat
Freezing of foods:
Freezing of foods depends on;
1. Temperature.
2. Circulation of air.
3. Kind of food
4. Size and shape of package.
FreezingQuick freezing Sharp /slow freezing
1. –15 to –29 C for 30 min 1. –15 to –29 C for 3-4 hrs till 72 hrs
2. No food damage 2. Damage of food by crystal formation.
3. Done by: 3. Done by the natural air circulation or
a. Direct immersion of food / package in through electrical fans.
Refrigerant. E.g.: fish in brine
b. Indirect contact (-17.8 to –45.6 c)
c. Air blast freezing (-17.8 to –34.4C)
Rigid air is blown.
Advantage of quick freezing:
1. Shorter period.
2. Prompt prevention of microbial growth.
3. Rapid slowing of enzyme action.
Dehydrofreezing: fruits and vegetables have about half there moisture removed before freezing.
Changes during freezing:
1. Expansion in volume of food.
2. Ice crystals formation may crush cells.
3. Frozen condition chemical and enzymatic reaction proceed slowly.
E.g.: meat, poultry, fish products, proteins may irreversibly dehydrated.
Oxidation
Meat -> red myoglobin -------------à brown metmyoglobin
On surface
Fats (meat, fish) -----à oxidized and hydrolysed
4. Metacryotic liquid:
Unfrozen, concentrated solutions of sugars, salts may ooze from packages of fruits or concentrates during storage as a viruses material.
5. Fluctuation in temperature results in ice crystal formation.
6. Deracination may occur.
7. Freeze burn :
when ice – crystals evaporate from the area at the surface this defect is observed. The spot appears dry, grainy and brownish, tissues become dry and tough.
E.g.: fruits, vegetables, meat, poultry and fish.
8. During freezing vegetative cells die soon but some may remain for a longer period of time.
Changes during thawing:
1. Drip / bleeding:
The pink or reddish liquid that comes from meat during thawing.
2. Leakage:
The liquid oozing out of fruits or vegetables on thawing.
3. The wilting and flabiness of physical damage during freezing.
4. Thawing refers to sudden heating and sudden cooling. The damage of food is due to the freezing and storage but do not become evident earlier. Some of the liquid during thawing may be reabsorbed by the food particles or may remain as such.
If the thawed fleshed foods are below 3.3 C can be used but otherwise food should be discarded.
Effects of freezing:
1. Lethal effects:
Rapid cooling of cells from optimal to 00 c may also result in death and referred to as cold shock, where there is change in lipid membrane damage the permeability of cell or to the release of repair enzyme inhibitors. E.g.: ribonuclease inhibitors
2. Sub – lethal effects:
During enumeration of frozen food there may be reduction but not tree death of organisms. Some may be injured or damaged are called as freeze – injured, frost injured or metabolically injured. Freezing of micro organisms in a food may result in cryoinjuiry.
Response of microorganisms to freezing:
Freezing depends on type of microorganisms usually found in foods involved in preservation. There are various factors involving freezing.
1. On the basis of sensitivity of microorganisms during freezing they can be classified as 3 different groups:
a. Susceptible or sensitive => e.g.: yeast, mould, gram-negative bacteria, and vegetative cells.
b. Moderately resistance => e.g. Staphylococcus, Enterococcus, gram-positive bacteria.
c. Resistant => e.g. Spore forming organisms.
2. Freezing also depends on the freezing rate. Critical range of temperature lead to death of microbes than during rapid freezing.
3. It also depends on the kind of food normally used for presentation. The food used for preservation by freezing usually gets spoiled due to
a. High moisture content.
b. Availability of O2
c. Salt and sugary environment.
4. Freezing also depends on the change in PH or altered acidity or alkalinity in food.
5. During freezing there is increase in moisture content and formation of intracellular crystals. This usually results in altered permeability in membrane and cell wall. Thus results in osmotic imbalance or osmotic shock favoring cell lyses. Intracellular lie crystals are harmful to cells than extra cellular ice crystals.
6. The initial killing rate during freezing is rapid, but it is followed by a gradual reduction of microorganisms are referred as storage death.
PRESERVATION BY USE OF DRYING
Introduction:
Drying is referred to as the removal of water or lowers the water activity or reduces the amount of available moisture.E.g., Dried fish => salt, condensed milk => sweet.
a). Sun Drying à Drying of food by exposure to suns rays.
b). Dehydrated / Desiccated à Drying by artificial means under controlled air flow, T and RB
c). Condensed à Drying where moisture removal from liquid substances
d). Evaporated Similar to dehydrated.
Product Before drying moisture % After drying moisture %1. Milk2. Egg3. Beef4. Apple juice
90
74
60
86
5
2.9
1.5
6.2
Methods of drying:
1. Solar drying:
à Direct sun’s rays
E.g., Raisins, figs, pears, peaches, rice, fish
2. Drying by mechanical dryers:
à Passage of heated air to food under controlled RH.
a) Use of KLIN / EVAPORATOR:
à They are used in form house
à Natural draft from heated air brings drying.
b) Forced draft drying:
à Heated air moves across the food usually in tunnels or food moved in conveyor belts through heated air.c) Spray dried:
à Spraying of liquid into a current of dry, heated air.d). Drum dried:
à Passage over a heated drum, with or without vacuum.3. Freeze drying:
Sublimation of water from frozen food by means of a vacuum and heat.E.g., Meat, Poultry, seafood’s and fruits.
4. Drying during smoking:E.g., wool smoke à desired flavors and preservative are uses. Meat à 43 – 71 C for few hrs to several days prevents mold growth.
It has HCHO, phenol, cresol, methyl and ethyl esters, ketones etc.5. Other methods:
a. Electronic Heatingb. Foam – mat drying ->Lipid whipped to foam, dried with warm air, crushed to
powder, as is pressure – gun puffing of partially dried foods to give a porous structure facilitate further drying.
c. Tower Drying ->Dehumified air at 30 C or less. E.g. Tomato concentrate, milk and potatoes.
Factors:1. Temperature2. Relative humidity of air3. velocity of air4. time of drying
If all these not accounts may lead to case hardening where rapid, evaporation of moisture from the surface than diffusion from the interior leads to hard, horny, impenetratable surface film that hinders further drying.Process:Before Drying, Drying and after Drying:Before reception into plant:
Food has to be inspected without any contamination as;1. Milk -> Pure from udder in low, may be contaminated by handlers, process, and
equipments.2. Meat/ Poultry -> Due to soil, intestinal activity, handlers, equipments.3. Fish -> By intestinal activity, surface slime, and handlers.4. Egg -> Handlers, equipments, hatched hen and soil.
Before Drying:1. Selection: a. Elimination of spoiled foods.
b. Rejection of cracked, dirty foods.c. Sorting for size, maturity and soundness.
2. Washing:Especially fruits and vegetables. These procedures are followed to remove soil
and adhering materials and removes microbes. Water must be pure as it may also acts as a source of contaminate if poor quality of water is used.E.g., Egg -> Moisture helps the bacteria to penetrate the shell.3. Peeling:
May be done by hand, machine, lye bath or abrasion. It reduce the number of microorganisms are on the surface.
4. Sub division:Slicing, cutting should not increase number of organisms but will do so if
equipment is not adequately cleansed and sanitized5. Alkali Dip: It may reduce the microbial population. E.g., Raisins, Grapes, etc -> Hot 0.1 – 1.5 % lye / Na2CO3 6. Scalding / Blanching:
a. Sulfuring of light colored fruits and certain vegetables.
b. Fruits -> 1000 – 3000 ppm of SO2 gasc. Vegetables -> dipping after blanching or spraying of sulfite solution.d. Helps to maintain an attractive light color, conserve vit C, vit A, repels
insect, kills many microorganisms.Drying:
1. Heat2. Freeze drying
After Drying:1. Sweating: Storage in boxes or tins. It is for equalization of moisture or addition of moisture to a desired level.E.g., Dehydration of meat at 60 C -> leads to growth of Staph. aureus ., so that 1000C applicable.2. Packing:
Packed the foods after drying for protection against moisture contamination with microbes, insects.3. Pasteurization:
Fruits usually during package -> 30 to 70 min – time, 70 to 100% - RH, 65.6 to 850C – Temperature.Microbiology of dried foods:
1. Dried fruits: Mold spores may be seen.2. Dried vegetables: Few 100’s per gram to million of organisms due to the
improper pretreatment. E.g.: Bacillus, Micrococcus, Clostridium, E.coli, Enterobacter, Pseudomonas, Streptococci and Lactobacillus, Leuconostoc.
3. Dried eggs: Coli forms, spore formers, molds, Micrococcus, Streptococci.4. Dried milk: Spore formers, Thermoduric, Streptococci, Micrococcus.
Intermediate moisture foods: (IMF)1. Commercially prepared foods haves 20-40% moisture and are non-refrigerated shelf stability are IMF.2. They have reduced water activity.E.g.: Candies, Jams, jellies, honey, bakery items etc.3. Aw may be 0.75 and 0.85 for IMF.4. They can be adjusted by the addition of sugar, salt or glycerols.
4. write short notes on preservation of foods by food additives.
INTRODUCTION
1) A food additive is a substance or mixture of substances, other than the basic food stuff, is present in food as a result of any aspect of production, processing, storage or packaging.
2) The definition emphasizes one interpretation of a food additive, i.e.; it is an intentional additive. There food additives are specifically added to prevent the deterioration or decomposition of a food have been referred to as chemical preservatives.
3) This decomposition may be caused by micro organisms, by food enzymes, or by purely chemical reactions. The inhibition of the growth and activity of
micro organisms is one of the main purposes of the use of chemical preservatives
4) Preservatives may inhibit micro organisms by interfering with their cell membranes, their enzymes activity or their genetic mechanisms.
Factors that influence the effectiveness of chemical preservatives in killing micro organisms or inhibiting their growth.
a. Concentration of the chemicalb. Kind, number, age & previous history of the organismc. Temperatured. Timee. The chemical & physical characteristics of the substrate in which the organism is
found.
The ideal antimicrobial preservative:
A chemical preservative should have a wide range of antimicrobial activity.
Should be nontoxic to human being or animals Should be economical Should not have an effect on the flavor, taste or aroma of the original food Should not be inactivated by the food or any substance in the food Should encourage the development of resistant strains Should kill rather than inhibit micro organisms
Organic acids and their salts:
Lactic, acetic, prop ionic & citric acids or their salts may be added to or
developed in foods
. Citric acid is used in syrups, drinks, Citric acid is used in syrups, drinks,jams &
Jellies
Lactic and acetic acids are added to brines of various kinds, green olives, etc.
Propionates:
Sodium or calcium propionate is used most extensively in the prevention of mold growth & rope development in baked foods & for mold inhibition in many cheese foods and spreads.
Experimentally, or on a limited scale, they have been used in butter, jams, jellies, apple slices & malt extract
They are effective against molds, with little or number inhibition of most yeast and bacteria.
Benzoates:
The sodium salt of benzoic acid has been used extensively as an antimicrobial agent in foods.
It has been incorporated into jams, jellies, carbonate (beverages, fruit salads, pickles, fruit juices etc.
Sorbates:
Sorbic acid, as the calcium, sodium or potassium salt, is used as a direct antimicrobial additive in foods.
It is widely used in cheeses, cheese products, baked goods, beverages, syrups, fruit juices, jellies, jams, dried fruits & pickles.
Sorbic acid & its salts are known to inhibit yeast & molds but are less effective against bacteria.
Acetates:
Derivatives of acetic acid
Dehydroacetic acid has been used to impregnate wrappers for cheese to inhibit the growth of molds
Acetic acid is more effective against yeast & bacteria than against molds.
Nitrites and Nitrates
Combinations of these various salts have been used in curing solutions & curing mixtures for meats.
Nitrites decompose to nitric acid, which forms nitrosomyoglobins when it reacts with the heme pigments in meats & thereby forms a stable red colour.
They are currently added in the form of sodium nitrite, potassium nitrate.
Recent works has emphasized the inhibitory property of nitrites towards Clostrium botulinum in meat products.
Sulfur dioxide and Sulfites:
The Egyptians and Romans burned sulfur to form sulfur dioxide as a means of sanitizing their wine – making equipments & storage vessels.
Today sulfur dioxide and sulfites are used in the wine industry to sanitize equipment to reduce the normal flora of the grape must.
Ethylene propylene oxide:
Ethylene oxide kills all micro organisms; propylene oxide, although it kills many micro organisms.
The primary uses have been as sterility for packaging materials, fumigation of water houses, & “cold sterilization” of numerous plastics, chemicals, pharmaceuticals, syringes & hospital supplies.
They have also been used successfully in dried fruits, dried eggs, cereals, dried yeast and spices
Sugar and salts:
Sodium chloride is used in brines & curing solutions or is applied directly to the food
Enough may be added to slow or prevent the growth of microorganisms or only enough to permit an acid fermentation to take place.
Salt has been reported to have the following effects.
It causes with osmotic pressure & hence plasmolysis of cells
It dehydrates foods by drawing out from the microbial cells.
It ionizes to yield the chlorine ion, which is harmful to organism
It reduces the solubility of oxygen in the moisture,
It sensitizes the cells against carbon dioxide
It interferes which the action of proteolysis enzymes.
Sugars, such as glucose or sucrose, owe their effectiveness as preservatives to their ability to make water unavailable to organisms and to their osmotic effect.
Examples of foods preserved by high sugar concentration are sweetened condensed milk, fruits in syrups, jellies & candies.)
UNIT-3
1.Discuss the food poisoning and food borne inflections.
FOOD BORNE INFECTIONS & INTOXICATIONSIntroduction :
Food borne diseases may be of 2 types,1. food borne infections2. food borne intoxications.
Food borne intoxication is by the presence of microbial toxin formed in the food. Food borne infection is caused by the microbe’s entry into the body through ingestion of
contaminated food & the reaction of the body to their presence or to their metabolites. Food borne infection can be divided into 2 types are [i] food that does not support growth of pathogens but merely carries them. Eg. Diphtheria, Dysentry, Typhoid fever, Brucellosis, Cholera, Infectious hepatitis, Q fever.
[ii] food that serve as a culture medium for the growth of the pathogens to no.s that will increase the infection of the consumer of the food. Eg. E. coli, Salmonella, V.parahaemolyticus. Outbreak of infections are explosive in 2nd type.
CLASSIFICATION OF FOOD BORNE DISEASESFood borne diseases
PoisoningsInfections
Chemical poisonings Intoxications Enterotoxigenic Invasive
Poisonous Poisonous Microbial Sporulation Growth Intestinal Systemic Other
Plant tissues Animal tissues intoxications & lysis mucosa Tissues
Algal Mycotoxins Bacterial toxins Muscle Liver
Toxins
Enterotoxins Neurotoxins Interferes with
Carbohydrate metabolism
FOOD BORNE DISEASES [BACTERIAL]
Intoxications Infections
1. Staphylococcal intoxication – an enterotoxin - 1. Salmonellosis– Enterotoxin & cytotoxin
S. aureus. 2. Cl. Perfringens - Enterotoxin
2. Botulism – neurotoxin – Cl. botulinum. 3. B. cereus – Exoenterotoxin - Gastroenteritis
4. Enteropathogenic E.coli – Enterotoxin - EPEC
5. Others: Vibrio parahemolyticus, Yersiniosis,
Shigellosis, Bacillus.
FOOD BORNE INTOXICATION
Staphylococcus
Introduction:
Food poisonings is caused by the ingestion of the enterotoxin formed in food during the growth of
S. aureus.
The toxin is enterotoxin because it causes gasteroenteritis or inflammation of the lining of the intestinal tract.
Organism:
Cluster of grapes or in pairs and short chains, Golden yellow colonies are formed on solid media.
Coagulase positive, aerobes, facultative anaerobes, some strains are salt tolerant [10-20% Nacl].
Fairly tolerant of dissolved sugars [50-60% sucrose], Fermentative & preteolytic but do not produce obnoxious odour [unattractice].
Based on serology, 6 distinct enterotoxins are classified [type A, B, C1, C2, D, E], Aà most effective toxin, Toxin production varies with food involved.
Water activity [0.86 – aerobes, 0.90 – anaerobes], pH [ 4.8 – aerobes, 5.5 – anaerobes], Temperature [370C – optimum growth, 25 – 45oC – minimum, 4 – 460C - Survive], 660C – 12 mins, 600C – 78 to 83 mins are necessary to destroy the organisms in food.
D value – 60oC – 7.7 mins – Decimal reduction time, Radiation to kill Staphylococci is gamma rays on moist foods – 0.37 to 0.488 Mrad of gamma rays on moist foods.
Enterotoxin character :
Simple protein with molecular weight between 26,000 – 30,000 is a single polypeptide chain are cross linked by a disulphide bridge to form a cystine loop.
Organism is heat labile but toxin is heat stable. Type A & D mainly cause disease. Increased concentration of toxin is necessary to cause disease.
Toxin gets inactivated at 190.6oC. Temperature affects the toxin production [ 370C – 12 hrs, 180C – 3 days, 90C – 7 days, 4 – 6.70C - 4 days].
Foods involved :
Bakery food products [cream biscuits], Milk and milk products, Cured meat, Ham, Poultry and poultry products, Salads, egg and egg products.
Disease :
Incubation period [2 – 4 hrs] – first symptom seen. Common symptoms are salivation, nausea, vomiting, abdominal cramping, diarrhea, dysentry.
In some cases, vomiting, headache, muscular cramping, sweating, chills, weak pulse, respiratory tract problems [ cannot swallow] these may be the secondary symptoms.
Decreased death rate and disease can be cured within 4 days. Active organism secretes enterotoxin into food àFood eatenà Enterotoxin
affects gut giving gasteroenteritis
Enterotoxin ingested along with food affects cells
Enterotoxin affects vomit receptors Water & Sodium pumps out of the cell
Vomiting center in the brain stimulated Diarrhea, fluid and electrolyte loss.
Vomiting Dehydration
Conditions for outbreak :
Food must contain enterotoxin producing Staphylococci. Food must be a good culture medium for growth & toxin production by the
Staphylococci. Temperature must be favourable and enterotoxin bearing food may be ingested.
Prevention of outbreaks :
Prevention of contamination of food with Staphylococci. Killing of Staphylococci growth. Prevention of Staphylococci growth. Contamination of foods can be reduced by :
1. general methods of sanitation.2. Using ingredients free from cocci – eg. Pasteurised milk than raw milk.3. By keeping employees away from foods who have colds, boils,
carbuncles, etc.4. Adequate refrigeration of food.5. Addition of bacteriostatic substances such as serine or antibiotic.
CLOSTRIDIUM BOTULINUM [INTOXICATION]Introduction :
Neurotoxin is produced by Clostridium botulinum which causes disease called Botulism. Death in infants is within 3 – 6 days & adults is 6 – 9 days. Organism is Gram positive, anaerobes, gas forming rod shaped bacteria which occurs in
soil. Antigen are classified based on toxigenicity as A,B,C,D,E,F,G – 7 types. Type A à Highly toxic to humans than B Type B, F & G à Less toxic to man. Type C à Cow, Cattle, other animals. Type D à Cattle. Type E à Fish and fish products.
Growth and toxin production :
The factors that influence the growth of organism are nutrient content of food [canned food, meat & fish], pH, temperature, oxidation - reduction potential, salt concentration, moisture content.
Contamination of food may be due to soil. Toxin is produced at pH 4.5, Organism must autolyse or sporulate to produce toxin. Non-proteolytic toxins are fully activated, These can be activated by binding with trypsin. Medium must have glucose or maltose for growth & toxin production. Medium should have nitrogen source, carbon source, casein and protein. Temperature [350C], pH [acidic – toxin production, Neutral – growth, anaerobic
environment. Nacl inhibits the growth of the organisms.
Toxins :
Toxins are protein substances produced by the organism during the growth and it is thermolabile.
Denaturation of the toxin is at 800C for 5 – 6 mins [type A], 900C for 15 mins [type B].
Radiation is used for toxin denaturation because it sterilizes deeply. Type A & B spores are highly heat resistant and the D valve is 1210C – 0.21 min – Type
A, 1000C – 0.003 to 0.017 mins – Type E.Foods involved :
Meat, string beans, sweet corn, beets, fish, asparagus, spinach, canned foods [ proteolytic – odor,
non-proteolytic – gas production].
Disease :
Incubation period [12 – 36 hrs], symptoms include nausea, vomiting, diarrhea, fatigue, dizziness, headache, constipation, double vision, difficult in swallowing & speaking, mouth dryness, throat constriction, swollen & coated tongue.
Temperature is normal or subnormal, involuntary muscles become paralyzed, paralysis spreads to the respiratory tract, heart & death results due to respiratory failure.
Symptoms are similar for type A,B,E poisoning but nausea, vomiting & urinary retention usually more severe with type E toxin.
Treatment [antitoxin administration, artificial respiration, keeping the patient isolated, maintaining the fluid balance in the body].
Neurotoxin ingested with foodà Neurotoxin passes through gut mucosa into blood stream
Toxin spreads throughout the body through bloodstream
Toxin binds to nerve at the junction This results in paralysis.
Conditions for outbreak :
Presence of the spores of type A, B, E. A food in which the spores can germinate & the clostridia can grow & produce toxin. Survival of the spores of the organism eg. Because of inadequate heating in canning or
inadequate processing. Environmental conditions after processing that will permit germination of the spores,
growth & toxin production by the organism. Insufficient cooking of the food to inactivate the toxin. Ingestion of the toxin bearing food.
Prevention of outbreaks : Use of approved heat processes for canned foods. Rejection of all gassy [swollen] or otherwise spoiled canned foods. Refusal even to taste a doubtful food. Avoidance of foods that have been cooked, held & not well heated. Boiling of a suspected food for atleast 15 mins. Avoidance of raw or precooked foods. To prevent botulism from smoked fish :
1. good sanitation throughout production & handling.2. fish heated to atleast 820C – 30 mins in coldest part.
3. fish be frozen immediately after packaging & kept frozen.4. all packaged be marked “ perishable – keep frozen”.
Infant botulism :
Infants --> predisposed constipation. Weakness, lack of sucking, loss of head control, diminished gag reflex. Death within 3 – 6 days. Milk, canned food [cereals] may cause intoxication.
Through mother’s infection.
2,Discuss the food borne infection of Salmonellosis.Introduction :
Causes gastroenteritis, Gram negative rods, non-spore formers, non-lactose fermenting organisms, facultative anaerobes, ferments glucose to produce gas and belongs to Enterobacteriaceae family.
Classification :
S. tyhi [ infect humans], S. typhimurium [infect animals]. Serotypes --> Somatic Ag [O], Capsular Ag [Vi], Flagellar Ag [H]. Temperature [370C – optimum, 450C – maximum, 6.7 – 7.80C - Minimum], pH [ neutral –
optimum, 4.1 – minimum, 9 - maximum]. Increased H2S à S. typphimurium, S. enteritis, decreased H2S à S. typhi. Grows well in low acid foods [5.5 – 5.7]. Heat sensitive bacteria [ 660C – 12 mins, 600C – 78 to 83 mins]. D value [600C for 0.06 – 11.3 mins]. More concentration of bacteria can cause disease à atleast 100 sp. Very less infective à S.pullorum, Highly infective à S.enteritis.
Sources of Salmonella contamination :
Humans [ Direct / Indirect, feces, handling, water contamination.] Animals [Direct / Indirect] – Dogs, cattle, cat [feces, infection, infected animal meat
contamination, poultry products – hen, chicken, meat & egg] due to improper processing, egg coated with fecal material. Increased refrigeration results in increased moisture & forms the pores & through this the organism enters.
Bakery products – sources through flies, cockroach, insects from infected to normal food.Foods involved :
Bakery products, Meat, Chicken, Milk and milk products – cheese, egg and egg products, cream cakes, Bacon & ham.
Disease :
Incubation period [12 – 36 hrs]. Symptom includes gastrointestinal infection are nausea, vomiting, abdominal pain, diarrhea, headache, chills.
Other evidences are watery, greenish, foul-smelling stool, prostration, muscular weakness, faintness, moderate fever, restlessness, twitching, drowsiness.
Mortality is low [1%]. Diarrhea to death in 2 – 6 days. Symptoms persist for 2 – 3 days, followed by uncomplicated recovery. Carriers – 0.2 to 5
%. Organism ingested along with the food Organisms grows in the host gut
Organism affects gut giving gastroenteritis
Bacterial cells ingested along with the food Cells invade the tissues & release endotoxin
Fever, vomiting , Diarrhea [fluid & electrolyte loss] --- It leads to loss of water & sodium ions
Conditions for outbreak :
Food must contain or become contaminated with the salmonella bacteria. Good culture medium. Viable organism must be ingested.
Prevention of outbreak :
Avoidance of contamination of food [diseased human beings, animals, carriers, contaminated eggs].
Destruction of the organisms in food by heat. Prevention of the Salmonella growth in foods by adequate refrigeration or by other
means. In the prevention of contamination :
1. care and cleanliness in food handling & preparation.2. Food handlers should be healthy & clean.3. Rats & other vermin & insects should be kept away from foods.4. Ingredients used in food should be free of Salmonella.5. Food should not be allowed to stand at room temperature for any length of time.
GASTROENTERITIS
CLOSTRIDIUM PERFRINGENSOrganism :
Gram positive, non-motile, anaerobic, spore forming rods. Temperature [43 – 470C], pH [ 5 – 9 ], D value [900C – 0.015 to .71 mins]. Organism growth is inhibited by 5% Nacl. Toxins produced are A, B, C, D, E where A is infective and C is less infective.
Foods :
Raw foods, soil, sewage, animal feces, meat, fish, poultry.Disease :
Incubation period [8-24 hrs]. Abdominal pain, diarrhea, gas, fever, nausea, vomiting are the symptoms. Enterotoxin released in the gut during sporulation results in fluid accumulation in the
intestine. Toxin is heat labile [ 600C – 10 mins – inactivated].
Symptoms:
1. Enterotoxin heat labile
2. Inactive at 60c for 10 min
3. Abdominal pain, diarrhoea with gas trouble, fever, nausea, vomiting.
4. Mortality is low.Conditions for outbreak :
Food contaminated with the organism. Food is not maintained properly. Inadequate cooling. Food is consumed without reheating.
Cells sporulate & produce enterotoxin
Infective dose:
Large number of vegetative cells in a food are required to produce food poisoning. The minimum seems to be about 7 x 105/g of food ingested but numbers as high as 108 /g or greater may be required.
Prevention of outbreaks:
1. Eat meat immediately after cooking.2. Cool cooked meats rapidly to 7ºC or below for storage and reheat to an internal T of
above 70ºC before consumption.3. Store cooked chilled foods correctly and heat to an internal T of 70 C or above.4. Foods held hot before consumption should be maintained at 60 C or above.5. Avoid transferring spores from raw to cooked meat during boiling, slicing, mincing but
not using common utensils and observing good hygiene.6. Adequate & rapid cooling of cooked foods.7. Reheating.8. Personal hygiene.9. Sanitation.
3.What is foodborne disease? Foodborne disease is caused by consuming contaminated foods or beverages.
Many different disease-causing microbes, or pathogens, can contaminate foods, so there are many different foodborne infections.
In addition, poisonous chemicals, or other harmful substances can cause foodborne diseases if they are present in food. More than 250 different foodborne diseases have been described.
Most of these diseases are infections, caused by a variety of bacteria, viruses, and parasites that can be foodborne. Other diseases are poisonings, caused by harmful toxins or chemicals that have contaminated the food, for example, poisonous mushrooms.
These different diseases have many different symptoms, so there is no one "syndrome" that is foodborne illness. However, the microbe or toxin enters the body through the gastrointestinal tract, and often causes the first symptoms there, so nausea, vomiting, abdominal cramps and diarrhea are common symptoms in many foodborne diseases.
Many microbes can spread in more than one way, so we cannot always know that a disease is foodborne. The distinction matters, because public health authorities need to know how a particular disease is spreading to take the appropriate steps to stop it.
For example, Escherichia coli O157:H7 infections can spread through contaminated food, contaminated drinking water, contaminated swimming water, and from toddler to toddler at a day care center. Depending on which means of spread caused a case, the measures to stop other cases from occurring could range from removing contaminated food from stores, chlorinating a swimming pool, or closing a child day care center. 4.What are the most common foodborne diseases? The most commonly recognized foodborne infections are those caused by the bacteria Campylobacter, Salmonella, and E. coli O157:H7 , and by a group of viruses called calicivirus, also known as the Norwalk and Norwalk-like viruses. Campylobacter is a bacterial pathogen that causes fever, diarrhea, and abdominal cramps. It is the most commonly identified bacterial cause of diarrheal illness in the world. These bacteria live in the intestines of healthy birds, and most raw poultry meat has Campylobacter on it. Eating undercooked chicken, or other food that has been contaminated with juices dripping from raw chicken is the most frequent source of this infection. Salmonella is also a bacterium that is widespread in the intestines of birds, reptiles and mammals. It can spread to humans via a variety of different foods of animal origin. The illness it causes, salmonellosis, typically includes fever, diarrhea and abdominal cramps. In persons with poor underlying health or weakened immune systems, it can invade the bloodstream and cause life-threatening infections. E. coli O157:H7 is a bacterial pathogen that has a reservoir in cattle and other similar animals. Human illness typically follows consumption of food or water that has been contaminated with microscopic amounts of cow feces. The illness it causes is often a severe and bloody diarrhea and painful abdominal cramps, without much fever. In 3% to 5% of cases, a complication called hemolytic uremic syndrome (HUS) can occur several weeks after the initial symptoms. This severe complication includes temporary anemia, profuse bleeding, and kidney failure. Calicivirus, or Norwalk-like virus is an extremely common cause of foodborne illness, though it is rarely diagnosed, because the laboratory test is not widely available. It causes an acute gastrointestinal illness, usually with more vomiting than diarrhea, that resolves within two days.
Unlike many foodborne pathogens that have animal reservoirs, it is believed that Norwalk-like viruses spread primarily from one infected person to another. Infected kitchen workers can contaminate a salad or sandwich as they prepare it, if they have the
virus on their hands. Infected fishermen have contaminated oysters as they harvested them.
Some common diseases are occasionally foodborne, even though they are usually transmitted by other routes. These include infections caused by Shigella, hepatitis A, and the parasites Giardia lamblia and Cryptosporidia. Even strep throats have been transmitted occasionally through food.
In addition to disease caused by direct infection, some foodborne diseases are caused by the presence of a toxin in the food that was produced by a microbe in the food. For example, the bacterium Staphylococcus aureus can grow in some foods and produce a toxin that causes intense vomiting.
The rare but deadly disease botulism occurs when the bacterium Clostridium botulinum grows and produces a powerful paralytic toxin in foods. These toxins can produce illness even if the microbes that produced them are no longer there.
Other toxins and poisonous chemicals can cause foodborne illness. People can become ill if a pesticide is inadvertently added to a food, or if naturally poisonous substances are used to prepare a meal. Every year, people become ill after mistaking poisonous mushrooms for safe species, or after eating poisonous reef fishes. 5.How are foodborne diseases diagnosed? The infection is usually diagnosed by specific laboratory tests that identify the causative organism. Bacteria such as Campylobacter, Salmonella, E. coli O157 are found by culturing stool samples in the laboratory and identifying the bacteria that grow on the agar or other culture medium.
Parasites can be identified by examining stools under the microscope. Viruses are more difficult to identify, as they are too small to see under a light microscope and are difficult to culture. Viruses are usually identified by testing stool samples for genetic markers that indicate a specific virus is present. Many foodborne infections are not identified by routine laboratory procedures and require specialized, experimental, and/or expensive tests that are not generally available.
If the diagnosis is to be made, the patient has to seek medical attention, the physician must decide to order diagnostic tests, and the laboratory must use the appropriate procedures. Because many ill persons to not seek attention, and of those that do, many are not tested, many cases of foodborne illness go undiagnosed.
For example, CDC estimates that 38 cases of salmonellosis actually occur for every case that is actually diagnosed and reported to public health authorities
6.How are foodborne diseases treated? There are many different kinds of foodborne diseases and they may require
different treatments, depending on the symptoms they cause. Illnesses that are primarily diarrhea or vomiting can lead to dehydration if the
person loses more body fluids and salts (electrolytes) than they take in. Replacing the lost fluids and electrolytes and keeping up with fluid intake are important.
If diarrhea is severe, oral rehydration solution such as Ceralyte*, Pedialyte* or Oralyte*, should be drunk to replace the fluid losses and prevent dehydration. Sports
drinks such as Gatorade* do not replace the losses correctly and should not be used for the treatment of diarrheal illness.
Preparations of bismuth subsalicylate (e.g., Pepto-Bismol)* can reduce the duration and severity of simple diarrhea.
If diarrhea and cramps occur, without bloody stools or fever, taking an antidiarrheal medication may provide symptomatic relief, but these medications should be avoided if there is high fever or blood in the stools because they may make the illness worse. *CDC does not endorse commercial products or services7.How do public health departments track foodborne diseases?
Routine monitoring of important diseases by public health departments is called disease surveillance. Each state decides which diseases are to be under surveillance in that state.
In most states, diagnosed cases of salmonellosis, E. coli O157:H7 and other serious infections are routinely reported to the health department.
The county reports them to the state health department, which reports them to CDC. Tens of thousands of cases of these "notifiable conditions" are reported every year. For example, nearly 35,000 cases of Salmonella infection were reported to CDC in 1998.
However, most foodborne infections go undiagnosed and unreported, either because the ill person does not see a doctor, or the doctor does not make a specific diagnosis. Also, infections with some microbes are not reportable in the first place.
To get more information about infections that might be diagnosed but not reported, CDC developed a special surveillance system called FoodNet. FoodNet provides the best available information about specific foodborne infections in the United States, and summarizes them in an annual report.
In addition to tracking the number of reported cases of individual infections, states also collect information about foodborne outbreaks, and report a summary of that information to CDC.
About 400-500 foodborne outbreaks investigated by local and state health departments are reported each year. This includes information about many diseases that are not notifiable and thus are not under individual surveillance, so it provides some useful general information about foodborne diseases.
8.What are foodborne disease outbreaks and why do they occur? An outbreak of foodborne illness occurs when a group of people consume the
same contaminated food and two or more of them come down with the same illness. It may be a group that ate a meal together somewhere, or it may be a group of
people who do not know each other at all, but who all happened to buy and eat the same contaminated item from a grocery store or restaurant.
For an outbreak to occur, something must have happened to contaminate a batch of food that was eaten by a the group of people. Often, a combination of events contributes to the outbreak.
A contaminated food may be left out a room temperature for many hours, allowing the bacteria to multiply to high numbers, and then be insufficiently cooked to kill the bacteria. Many outbreaks are local in nature. They are recognized when a group of people realize that they all became ill after a common meal, and someone calls the local health department. This classic local outbreak might follow a catered meal at a reception, a pot-luck supper, or eating a meal at an understaffed restaurant on a particularly busy day.
However, outbreaks are increasingly being recognized that are more widespread, that affect persons in many different places, and that are spread out over several weeks.
For example, a recent outbreak of salmonellosis was traced to persons eating a breakfast cereal produced at a factory in Minnesota, and marketed under several different brand names in many different states.
No one county or state had very many cases and the cases did not know each other.
The outbreaks was recognized because it was caused by an unusual strain of Salmonella, and because state public health laboratories that type Salmonella strains noticed a sudden increase in this one rare strain.
In another recent outbreak, a particular peanut snack food caused the same illness in Israel, Europe and North America. Again, this was recognized as an increase in infections caused by a rare strain of Salmonella. The vast majority of reported cases of foodborne illness are not part of recognized outbreaks, but occurs as individual or "sporadic" cases.
It may be that many of these cases are actually part of unrecognized widespread or diffuse outbreaks. Detecting and investigating such widespread outbreaks is a major challenge to our public health system.
This is the reason that new and more sophisticated laboratory methods are being used at CDC and in state public health department laboratories. 9.List out the information centers for food safety and foodborne diseases?
National Food Safety Initiative CDC's Food Safety Initiative home page U.S. Food and Drug Administration U.S. Food Safety and Inspection Service (FSIS) U.S. Environmental Protection Agency Role of the federal agencies in food safety Gateway to government food safety information Partnership for Food Safety Education/Fight BAC! TM Food Safety Training and Education Alliance Foodborne Illness Information Center National Food Safety Education Month Travelers' Health
LABORATORY TESTING:
The procedure to be followed in testing the samples of food or specimens from human source upon receipt in the laboratory will depend on the type of food and the information available about the outbreak of food illness.
The first act in most laboratories is to make a microscopic examination of a preparation of the food stained by the Gram’s method. The smear is made from liquid or from the sediments from homogenized, centrifuged food.
The microscopic examination may give a clue to the causative if the sample has been properly refrigerated.
Preventive measures:
To keep foods as free as possible from contamination which pathogenic agents by selection of uncontaminated foods, by adequate pasteurization or other heat processing, by avoiding contamination from infected food handlers or carriers, and by generally good sanitary practice throughout the handling, preparation and serving of foods.
To eliminate opportunities for the growth of pathogens, toxigenic or infectious, in foods by adjustment of the composition, by prompt consumption after preparation, and by adequate refrigeration of perishable foods if they must be hold for any considerable time, keeping foods warm for long periods is especially to be avoided.
To reject suspected foods
To educate the public better concerning the causes and prevention of food borne illness and the dangers involved.
FOOD SANITATION AND PLANT SANITATION:
Employee health standards:
Introduction:
The food industry sanitarian is concerned which specific aseptic practices in the preparation, processing, and packaging of the food products of a plant and the health of cleanliness and sanitation of plant and the health of employee.
Food and plant sanitation:
Specific duties in connection which the food products may involve quality control and storage of raw products, the provision of a good water supply; prevention of the contamination of the foods at all stages during processing from equipment, personnel, & the vermin; and supervision of packaging and ware housing of finished products.
The supervision of cleanliness and sanitation of plant and premises includes not only the maintenang of clean and well sanilized surfaces of all equipment toughing the foods but also generally goods house keeping in and the plant and adequate treatment and disposal of wastes.
Employee health standards:
Duties affecting the health of the employees include provision of a potable water supply, supervision of matters of personal lygiene, regulation of sanitary facilities in the plant and in plant operated of plant lighting, heating and ventilation. The sanitarian may also participate in training employees in sanitary practices.
For the most part, sanitarians concern themselves chiefly with general aspects of sanitation, making inspections, consulting with personnel responsibless for details of canitation and executives directing such work, and training personnel in sanitation.
SEWAGE WASTE TREATMENT AND DISPOSAL:
INTRODUCTION:
The food sanitation is concerned directly or indirectly with the adequate treatment and disposal of wastes from the industry. Solid and concentrated wastes ordinarily are kept separate the watery wastes and may be used directly for food, feed fertilizers, or other purpose; may first be concentrated dried, or fermented (ex: pea vine silage);or may be carted away to available land as unusable waste.
WASTE TREATMENT:
Care is taken to keep out of the waste waters as much wasted liquid or solid food material as possible by taking precautions to avoid introduction into the watery waste of drip, leakage, overflow, spillage, large residues in containers, foam, frozen on and food dust during the handling and processing of the food.
I t is recommended that sewage of human origin be kept separate from other plant waters because of the kept separate from other plant waters because of the possible presence of human intestinal pathogens.
Such sewage may be turned in to a municipal system.
Wastes from food plants ordinarily contain a variety of organic compounds, which range from simple and readily oxidizable kinds to those which are complex and difficult to decompose.
The strength of the sewage or food waste containing organic matter is expressed in terms of biochemical oxygen
demand ( BOD), which is the quantity of O2 used by aerobic microorganisms and reducing compounds in the
Stabilization of decomposable matter during a selected time at a certain temperature.
A period of 5 days at 20oC is generally used, and results are expressed as 5 days BOD.
Wastes from a food plant to be emptied into a body of water must either be so greatly diluted by that water must be treated first to reduce the oxidizable compounds to a harmless level.
Preliminary treatments of food- plant wastes by chemical means may be employed, but most systems of treatment and disposal depend on
1. Screening out of large particles.
2. Floating of fatty and other floating materials
3. Sedimentation of as much of the remaining solids
4. Hydrolysis, fermentation and putrefaction of complex organic compounds and finally5. Oxidation of the remaining solids inn the water to a point where they can enter a municipal sewage treatment and disposal systems.
BIOLOGICAL TREATMENT AND DISPOSAL:
Dilution, by running waste waters into a large body of water.
Irrigation, in which wastewaters are sprayed onto shallow artificial ponds (with or without treatments)
Use of trickling filters; made of crushed rock, coke, filter tile, etc.,
Use of the activated- sludge method, in which wastewater is inoculated heavily with sludge from a previous reaction.
Use of anaerobic tanks of various kinds, where settling, hydrolysis, putrefaction and fermentation take place.
FOOD BORNE:
POISONINGS, INFECTION AND INTOXICATION
NON BACERIAL:
Introduction:
Some food borne disease outbreaks are not caused by bacteria or their toxins but results from mycotoxins, viruses, rickettsiae, parasitic worms, or protozoa or from the consumption of food contaminated with toxin substances.
10.Write a detailed account on mycotoxins and the key management
steps to prevent mycotoxin contamination.
Mycotoxins:
Mycotoxins are fungal metabolites. Some are highly toxic to many animals potentially toxic to human beings. Recent concern is related to their carcinogenic properties and their presence in many food items.
FUNGI AND HUMAN BEINGS:
The fungi include the moulds, yeasts, blights, rusts and mushrooms.
Many fungi are useful. Some are edible. Ex: Mushrooms and single cell protein from yeast.
Other is widely used in industrial and food fermentation.
Ex: Aspergillus oryzae is used in the production of soy sauce, miso and sake and moulds take part in the ripening of certain cheese.
Some mushrooms are harmful or poisonous to humans, but in contrast, moulds have generally been regarded as harmless.
Many fungi can be isolated from plants, including Alternaria, Rhizopus, Fusarium, Cladosporium, Helminthosporium and Chaetomium.
The two predominant genera of fungi in stored products are probably Penicillium and Aspergillus, members of which produce mycotoxins.
The syndrome resulting from the ingestion of toxin in a mold- contaminated food is referred to as mycotoxicosis.
AFLATOXIN:
Aflatoxins are produced by certain strains of A.falvus and A. parasiticus.
CHEMISTRY:
The two major metabolites or aflatoxins have been designated B, and G1 because they fluoresce Blue(B1) and Green (G1).B2 and G2 are the dihydroderivatives of B1 and G1.
TOXICITY:
Aflatoxin B1, the most toxic of the aflatoxins, is toxic to various animals. Many of the other aflatoxin have been shown to be toxic or carcinogenic to different species of fish, mammals and poultry.
SIGNIFICANCE IN FOODS:-
Many foods will support the growth of toxigenic strains if inoculated, including various dairy products, bakery products, fruit juices, cereals and forage crops.
In most cases, the growth of a toxigenic strain and the elaboration of aflatoxin occurs following harvesting or formulation of the product.
Peanuts, cottonseeds, and corn, however, differ significantly in that these products are susceptible to fungal invasion, growth and mycotoxin production before harvesting.
The contamination and potential for aflatoxin production in these crops is related to insect damage, humidity, weather conditions.
OTHER TYPES OF MYCOTOXIN:
Patulin: Produced by Penicillium expansum
OchratoxinProduced by Asperillus ochraceus
Luteoskyrin Produced by Penicillium islandicum
Roquefortine Produced by P. roqueforti
QUALITY CONTROL:
Quality of foods and food products may be defined as the degree of excellence of the various characteristics that influence consumer acceptance as well as consumer safety.
The selection of a particular food by a discerning consumer is made by the judgment of all the physical senses that is, tough, smell, taste and hearing.
Consumer safety requires the evaluation of food quality with respect to nutritional quality, hygienic condition and keeping storage.
MICROBIOLOGICAL EXAMINATION OF FOOD:-
Introduction
The stated chief purposes of microbiological criteria for foods are to give assurance:
1. That the foods will be acceptable from the Public health standpoint that is will not be responsible for the spread of infectious disease or for food poisoning.
2. That the foods will be of satisfactory quality3. The foods will have keeping qualities that should be expected of the product.4. Sampling for tests is a problem since the lack of homogeneity in most foods
makes location, size and number of samples significant.5. Standards usually are based on total numbers of organisms, numbers of
organisms, numbers of indicator organisms or numbers of pathogens.
INDICATOR ORGANISMS:-
It may be necessary to carry out a microbiological examination of a food for one or more of a number of reasons.
Escherichia coli is a natural component of the human gut flora and its presence in the environment, or on foods, generally implies some history of contamination of faecal origin.
Traditional the group chosen has been designated the coliforms- those organisms capable of fermenting lactose in the presence of bile at 37C.
This will include most strains of E. coli but also includes organisms such as Citrobactor and Enterobactor.
DIRECT EXAMINATION:-
. When examining foods, the possibility of detecting the presence of microorganisms by looking at a sample directly under the microscope should not be missed.
. A small amount of material can be mounted and teased out in a drop of water on a slide, covered with a cover slip, and examined.
CULTURAL TECNIQUES:-
The full microbiological examination usually requires that individual viable propagules are encouraged to multiply in liquid media or on the surface, or with in the matrix, of a medium solidified with agar.
A SELEATION OF MEDIA COMMONLY USED IN FOOD MICROBIOLOGY:
MEDIUM USE
1. Plate count agar Aerobic mesophilic count
2. Mac Conkey broth MPN of coliforms in water
3. Brilliant Green/Lactose/ Bile broth MPN of coliforms in food
4. Violet red/ bile/Glucose agar Enumeration of Enterobacteriaceae.
5. Crystal violet /Azide / Blood agar Enumeration of faecal Streptococci.
6. Baird- Parker agar Enumeration of S. aureus
7. Vassiliadis broth Selection enrichment of Salmonella.
8. Thiosulfate / bile/ citrate/ Sucrose agar Isolation of Vibrios
9. Rose Bengal/ Chloramphenicol agar Enumeration of moulds and yeasts
10. Mac Conkey agar E. coli
ENUMERATION METHODS:-
Plate counts-
It has already been suggested that to count microorganisms in a food sample by direct microscopy has a limited sensitivity because of the very small sample size in the field of view at the magnification needed to see microorganisms, especially bacteria.
In a normal routine laboratory the most sensitive methods of detecting the presence of a viable bacterium is to allow it to amplify itself to form a visible colony.
This forms the basis of the traditional pour plate and spread plate and most probable number counts.
ALTERNATIVE METHODS- .Cultural methods are relatively labour intensive and require time for adequate growth to
occur. . Many food microbiologists also consider that the traditional enumeration methods are not
only too slow but lead to an over dependence on the significance of numbers of colony forming units.
. A number of methods have been developed which aim to give answer of redox to as “Rapid methods”.
1. Dye- reduction test:-
A group of tests which have been used for some time in the dairy industry dependent on the response of a number of redox dye to the presence of metabolically active microorganisms.
They are relatively simple and rapid to carry out at low cost. The redox dyes are able to take up electrons from an active biological
system and this results in a change of colour.
2. Immunological methods:-
ELISA.
3. DNA/RNA methodology:-
PCR method
UNIT-4
1. Write an account on idli fermentation and the micro organisms
involved in the fermentation.
FERMENTED FOOD
IDLI:
The idli , also romanized "idly" or "iddly" and plural "idlis", is a savory cake popular throughout South India. The cakes are usually two to three inches in diameter and are made by steaming a batter consisting of fermented black lentils (de-husked) and rice. The fermentation process breaks down the starches so that they are more readily metabolized by the body.
Most often eaten at breakfast or as a snack, idlis are usually served in pairs with chutney, sambar, or other accompaniments. Mixtures of crushed dry spices such as milagai podi are the preferred condiment for idlis eaten on the go.
History
Although the precise history of the modern idli is unknown, it is a very old food in southern Indian cuisine. One mention of it in writings occurs in the Kannada writing of Shivakotiacharya in 920 AD,[1] and it seems to have started as a dish made only of fermented black lentil. Chavundaraya II, the author of the earliest available Kannada encyclopaedia, Lokopakara (c. 1025), describes the preparation of Idli by soaking Urad dal (black gram) in butter milk, ground to a fine paste and mixed with the clear water of curd, and spices.[2] The Kannada king and scholar Someshwara III, reigning in the area now called Karnataka, included an idli recipe in his encyclopedia, the Manasollasa, written in Sanskrit ca. 1130 A.D. There is no known record of rice being added until some time in the 17th century. It may have been found that the rice helped speed the fermentation process. Although the ingredients used in preparing idli have changed, the preparation process and the name have remained the same.
In ancient Tamilnadu, Puttu or pittu (made out of rice flour)was a very popular food and the recipe was very similar to modern idli .
Idli was derived from a tamil word "Ittu Avi" means pour it (or put it)and steam it. Later it turned into (maruviyadu) Ittavi and then into ittali.
The earliest Tamil writings are traced to about 300 BC, but references to edibles and food habits abound in literature between 100 BC and 300 AD (Idaicchangam). Dosai and Vadai, as said above, were popular. Tamils ate meals of all kinds, as well as fish.
Preparation
Idli batter is poured into the round indentations of the idli pans (pictured) and placed into a pressure cooker.
To make idli, two parts uncooked rice to one part split black lentil (Urad dal) are soaked. The lentils and rice are then ground to a paste in a heavy stone grinding vessel (attu kal). This paste is allowed to ferment overnight, until it expands to about 2½ times its original volume. In the morning, the idli batter is put into the ghee-greased molds of an idli tray or "tree" for steaming. These molds are perforated to allow the idlis to be cooked evenly. The tree holds the trays above the level of boiling water in a pot, and the pot is covered until the idlis are done (about 10-25 minutes, depending on size). The idli is somewhat similar to the dosa, a fried preparation of the same batter.
In the olden days, when the idli mold cooking plates were not popular or widely available, the thick idli batter was poured on a cloth tightly tied on the mouth of a concave deep Cooking pan or tava half filled with water. A heavy lid was placed on the pan and the pot kept on the boil until the batter was cooked into idli. This was often a large idli depending on the circumference of the pan. It was then cut into bite-size pieces and eaten.
Contemporary Idlis and variations
Rava idli, a specialty of Karnataka
Southern Indians have brought the popular idli wherever they have settled throughout the world. Cooks have had to solve problems of hard-to-get ingredients, and climates that do not encourage overnight fermentation. One cook noted that idli batter, foaming within a few hours in India, might take several days to rise in Britain. The traditional heavy stones used to wet-grind the rice and dal are not easily transported. Access to Indian ingredients before the advent of Internet mail order could be virtually impossible in many places. Chlorinated water and iodized salt interfere with fermentation.
Newer "quick" recipes for the idli can be rice- or wheat-based (rava idli). Parboiled rice, such as Uncle Ben's can reduce the soaking time considerably. Store-bought ground rice is available, or Cream of Rice may be used. Similarly, semolina or Cream of Wheat may be used for rava idli. Yoghurt may be added to provide the sour flavor for unfermented batters. Prepackaged mixes allow for almost instant idlis, for the truly desperate. However, the additional health benefits of fermentation process will be lacking. Idli Burger is another variation that can be made easily.
Besides the microwave steamer, electric idli steamers are available, with automatic steam release and shut-off for perfect cooking. Both types are non-stick, so a fat-free idli is possible. Table-mounted electric Wet grinders may take the place of floor-bound attu kal. With these appliances, even the classic idlis can be made more easily.
The plain rice/black lentil idli continues to be the popular version, but it may also incorporate a variety of extra ingredients, savory or sweet. Mustard seeds, fresh chile peppers, black pepper, cumin, coriander seed and its fresh leaf form (cilantro), fenugreek seeds, curry leaves , fresh ginger root, sesame seeds, nuts, garlic, scallions, coconut, and the unrefined sugar jaggery are all possibilities. Filled idlis contain small amounts of chutneys, sambars, or sauces placed inside before steaming. Idlis are sometimes steamed in a wrapping of leaves such as banana leaves or jackfruit leaves.
A variety of idlis are experimented these days, namely, standard idli, mini idlis soaked in sambar, rava idli, Kancheepuram idli, stuffed idli with a filling of potato, beans, carrot and masala, ragi idli, pudi idli with the sprinkling of chutney pudi that covers the bite-sized pieces of idlis, malli idli shallow-fried with coriander and curry leaves, and curd idli dipped in masala curds.
Ramasseri Idli : Ramasseri, an offbeat village in Palakkad is known all over Kerala for the idlies it make - the delicious Ramasseri Idli. Spongy and soft Ramasseri Idli is slightly different in shape from the conventional idlies. It is a little flat and round. Ramasseri Idli is eaten with Podi mixed in coconut oil. The beginning was from a Muthaliyar family living near Mannath Bhagavathi Temple in Ramasseri near Elappullly.The recipe of Ramasseri idli dates back to about one century,which again is a trade secret. The Muthaliyar family was migrated to Palakkad from Kanchipuram in Tamil Nadu. The new generation in the profession says that the secret of the recipe and taste were handed down to them from grand old women of the community. Now the idli business is confined to four families in Ramasseri. Selection of rice is very important in making Ramasseri idli. Usually the verities used are Kazhama, Thavalakannan, Ponni etc. The taste starts from the boiling of paddy itself. Drying and dehusking are also important. It is done in a particular way. The combination of rice and black gram is also equally important. For 10 kg of rice, one kg of black gram is used. Idli is made only after four hours of fermentation. Boiling of the idli is done on a cloth covered on the mud pot using firewood. This provides special taste to the preparation.
Leftover Idli can be torn into crumbs and used for preparing dishes such as Idli fry and Idli Upma.
Picture gallery
Idli and Vada served with sambar and two type of chutneys (green and red) on banana leaf.
The South Indian staple breakfast item of idli, sambar, and vada served on a banana leaf. Note the stainless steel plates and cups; characteristic of south Indian dining tables.
Tatte Idli: variations from Karnataka
Sambar idli: Idli soaked in sambar. Chutney is the best companion for this dish.
MTR idli: Famous Mavalli Tiffin Room idli served with pure ghee and sambar. Pure ghee is poured on steaming idli and relished with chutney or sambar.
Button Idli. This usually contains fourteen idli and is therefore called "fourteen idli". However this name came from Floating idli (small idlies floating on sambar, rasam or butter milk)
Sanna(s), a Goan variant of idli.
2.Write a brief account on bread making.BREAD
Bread is one of the fermented food products, the fermentation being brought about mainly by yeast.
Methods of bread production:-
The bread is made by a number of procedures. But the most common methods utilized are,
1. Sponge dough2. Straight dough3. Continuous mix4. Liquid ferment.Sponge dough:-
This is the predominant bread making method using by the baking industry.
Sponge comprises of about 65% of about total flour + a portion of total dough water + yeast & yeast food, its first mixed. This mixing period is brief. The sponge is then discharged into a trough where it will undergo a fermentation period of 4-5 hrs from starting temperature of about 25 0 C to a final rise by 6 0C. Due to exothermic reactions brought about by yeast activity. Sponge volume will increase due to CO2 production.
At the end of sponge fermentation, the sponge is transferred into a dough mixture. The balance of the flour, water remaining ingredients are added into the mixture and allow mixing. First at low speed & at higher speed until the dough is completely mixed. At this point dough has been transformed from a sticky wet appearing nature into smooth cohesive dough characterized by glossy sheen, upon addition of water & input of energy wheat protein & lipids form gluten. The dough due to the unique nature of gluten able to retain the gas & is thereby leavened.
The mixed dough is placed in troughs & allows resting for 20-30 minutes.
Dividing the dough is the next stage. The dough is cut into pieces of desired weight by a machine & conveyed on a belt to a rounder where the rough appearing pieces are removed such that the pieces are held for a rest period of 8-12minutes to compensate for the loss of gas.
The dough pieces are conveyed to moulding machines, which transform the round dough pieces into cylinders. Automatic moulders feed the dough cylinders into bread pans.
Pans-containing dough pieces are placed in fermentation unit called proof-boxes, for last fermentation period prior to baking. They are held at 35-43 0C at a relative humidity of 80-95% for 60minutes. The proof lobes are placed in oven for baking. Gas within the dough expands. Steam & alcohol vapors also contribute to this expansion. Enzymes are active until the bread reaches 75 0C. At this temperature starch gelatinizes & dough structure is set. When the bread surface temperature reaches the 130-140 0C sugars & soluble proteins react chemically to produce an attractive crust colors. The center of the leaf doesn’t exceed 100 0c.
Remaining stages in bread making process includes cooling of the baked bread, slicing, wrapping & distribution to stores.
Function of yeast in bread making:-
Major function of yeast in bread making includes:
1. Leavening2. Flavor development3. Dough maturing
1. Leavening:- Dough is usually leavened by bread yeast which ferment the sugars in the dough & produce Co2 &
alcohol. There is little or no growth during the first 2hrs, after the yeast is added to dough, but some growth in 2-4hrs & then there is a decline in growth in 4-6hrs. Fermentation by the yeast begins as soon as the dough mixed & continuous until the temperature of oven inactivates the yeast enzyme.
During fermentation conditioning of the dough takes place when the flour proteins (gluten) mature i.e., it becomes elastic & springy & are therefore capable of retaining maximal amount of CO2 produced by the yeast. The conditioning results from action on the gluten by: -
Proteolytic enzymes in the flour from the yeast & Malt. Reduction in pH by the acids added & formed.
Dough conditioners called yeast foods are added which include ammonium salts to stimulate the yeast &
various salts.
Example:- Kbro3,Cao,KIO 3 to improve dough characteristics.
Adding increases the rate of gas production by the yeast,
More yeast. Sugar or amylase bearing malt Yeast food.The main objective of the baking during leavening is to have enough gas produced & to have dough
that will hold the gas at the right time.
Heterofermentative lactic acid bacteria & saccharolytic anaerobes can accomplish leavening. Leavening by chemicals is accomplished by using baking powder or by C02 gas, which may be incorporated directly, or ammonium bicarbonate may be used.
2. Flavor development:- Fresh bread has a pleasing & appealing flavor. Bread flavor is derived from 2 main sources.
Yeast fermentation Crust browsing
Yeast fermentation:- The characteristics flavor yeast raised bread arises from yeast fermentation & subsequent reaction of
fermentation products with other dough compounds during baking. During baking some of these flavor compounds escape & other react with amino acids & other compounds of the dough to yield characteristic flavor of bread. Fermentation byproduct formed during yeast fermentation is organic esters, acids, alcohol, carboxyl compounds. Some of the organic compounds formed during fermentation may arise from bacterial action.
Lactic acid bacteria found in dough are associated with yeast. In addition to Saccharomyces cerevisiae other yeast may be responsible for characteristic flavor of certain breads.
Breakdown products of flavor proteins play an important role in flavor & color development. Yeast proteolytic enzyme modify peptones & polypeptides for growth, a portion of these product react with sugars to impart desirable flavor upon baking.
Crust Browning:-
The extent of crust browning is influenced by previous activities of in the Saccharomyces cerevisiae dough. A part of bread flavor is formed in the crust during baking & then diffuses into crumb where it becomes observed.
Compounds produced during Fermentation & Baking:-
Organic acids Aldehydes/Ketones Alchol Carbonyl compounds
Butyric Acetaldehyde Ethanol Furfural
Succinic HCHO n-propanol Glyoxal
Propionic Acetone Isobutanol Methional
Isobutyric Diacetyl Amyl alcohol Hydroxy methyl furfural
Isovaleric Acetoin Isoamyl alcohol
Palmitic
Acetic
Lactic
Formic
Caproic
Valeric
Lauric
Myristic
3. Dough Maturing:-
The changes caused by yeast in the dough are called dough maturing or ripening. A properly matured
dough exhibits optimum rheological properties [optimum dough balance of extensibility & Elasticity] such that it may be machined well & will lead to bread with desirable volume & crumb characteristics, some of the reactions leading to dough maturing are as follows.
Alcohol & Co2 are derived from yeast fermentation. Alcohol is water miscible & since appreciable amounts are formed. It influences the colloidal nature of the flour proteins & alters the interfacial tension within the dough. Some of the CO2 dissolves in aqueous phase & form carbonic acid, which lowers the pH of the system. CO2 also distends the dough work into the dough system.
Ammonia from ammonium sulphate & ammonium chloride added to the dough, as yeast foods are assimilatory S. cerevisiae causing a liberation of H2SO4 & HCl. These acids along with carbonic aid lower the pH, Which in turn influences
Gluten hydration & Swelling The reaction rate of enzyme in the dough
Oxidation-reduction reactions & Various chemical reactions.
ACIDOPHILUS MILK Use:
A lactobacillus acidophilus organism are able to get themselves implanted in the large intestine of human beings through regular consumption of product and thereby controls GI disorders such as diarrhea, dyspepsia, constipation, flatulence, colitis in adults and children.
3.Write a brief account on Wine production.
Harvest in late summer (August), without tools, mainly by men.
Grapes were placed into baskets.
The baskets were emptied into a treading vat.
Treading the grapes underfoot.
The remainder was pressed (wrung out) in a cloth or a sack to gather all liquid.
Fermentation (i.e. grape juice turns into wine - sugar turns into alcohol); the wine has to be sealed, otherwise it turns into vinegar.
one or two days of fermentation - light wine
several weeks - heavy wine
longer period - wine turns into vinegar From the scant evidence it seems that red wine was very common in ancient Egypt; white wine is first securely attested in the third century AD.
In the tomb of Tutankhamun wine jars were found with the inscription: irp nDm 'Sweet wine'. Partly dried grapes, (because they contain concentrated sugar) were used for producing sweet wine.
Sweet wines have a high alcohol content and are therefore longer resistant
'Blended wine' (irp smA), appears on labels found at Malqata. It is not certain whether wine of different years, vineyards or types were mixed.
Other wines mentioned in Egyptian texts were made
from sweet fruits, such as dates and fig.
4.Explain the production of Beer.
There are four main ingredients in a real Beer:
WATER - The quantity and variety of dissolved salts in the water used will play a great part in the character of the final beer. The salts play a part in the extraction of fermentable sugars from the grain as well as affecting the way the yeast behaves during fermentation.
The total salts in Pilsen's water amounts to around 30 parts per million whereas in Burton on Trent UK, the content is 1220 parts per million. The main salts of interest are as follows; Calcium - increases the extract (efficiency of extracting sugars during mashing). It can also help to make the beer clearer. Sulphates - enhance the bitterness of the hops. It was Calcium Sulphate in the local water in Burton on Trent that helped to create the pale ale style of beer. Chlorides - help to enhance sweetness. These are relatively high in the waters of Dublin and London. This is where Porters and Stouts originated. Part of the modern brewing process involves modifying the content of these key ions to produce a water that is best suited to the style of beer being produced. .
MALT - Grapes can be made to release their sugars simply by crushing. In more Northern latitudes where grapes and sweet fruits do not readily grow ancient people turned to another source. It was probably discovered by accident that as a harvested grain started to germinate, it's sugar content seemed to increase. This was due to the conversion of starches in the grain into sugars as the seed began to germinate. If this process is stopped by drying at an optimal point in this process, the grain will contain some sugars plus a quantity of enzymes to aid the extraction of fermentable sugars. The process of mashing (see below) makes use of these enzymes to do just this job.
HOPS - Winemakers used to add aroma to their wines through adding spices and fruit. The favourite for brewers is to add the flower of the hop vine. When wine makers moved to ageing their wines in oak casks, they discovered that the wood performed a similar job but most modern beers are too light in flavour to cope with this process. The herbs and spices once added to wine also acted as a preservative. The hop cones added to beer also perform very well in this respect. The hops add alpha and beta acids that provide bitterness and aroma to the final product. Hops are chosen for their content in these products as required by the beer being produced. They are also added at different stages in the process depending on whether they are being used to provide bitterness or aroma. Our beers use hops to provide both bitterness and aroma.
YEAST - The first winemakers did not realise the spontaneous fermentation of their grapes was caused by the wild yeasts that collected on the skins of the grapes. Some styles of beers still make use of wild yeasts but as the yeast has such a contribution to make to the character of the final beer, most modern brewers prefer to control the yeast culture. They style of ales we produce uses top fermenting yeast. These are yeasts that form a foam on the top of the beer during fermentation. This foam is skimmed at a certain stage in the fermentation and used to start the next beer fermenting. These yeasts are used at higher temperatures. They are pitched in at around 15 deg C and the fermentation temperature rises as the yeast culture grows. The temperature can rise to 25C or more but must be controlled to prevent undesirable products being produced that can affect the final flavour. The sugar content of the liquid is monitored throughout the fermentation and the process is stopped when the desired alcohol strength is reached.
The Process
The malt is cracked (rolled between precisely set rollers) to just split the grains but not produce flour. This stage is critical as we just need grains that are split to release the sugars and enzymes. Grains that are crushed to a flour prevent the mash from being effective and can block filters etc later in the process. This cracked grain is mixed with water at a precisely controlled temperature of around 67 C. This is a temperature that stimulates the enzymes in the malt to convert starches to sugars that are released into the liquid now called a wort.
A process known as sparging is used to try to maximise the extraction by adding more water until the volume of liquid is correct and then recirculating the wort through the grain. Once the sugar extraction is completed 90-120 minutes, the wort is pumped through to a large boiler known as a 'copper'. The wort is now brought to the boil at which point the first batch of hops is added. Hops added at this stage are for bitterness. Any aroma imparted from the hops added at this stage will be boiled off. The wort is boiled for around 90 minutes before the aroma hops are added and the heat removed. After a short period of time, the wort is rapidly cooled and transferred to a fermentation vessel at around 17 deg C. The yeast is added as soon as conditions are right and fermentation generally starts in a few hours. It is important that the temperature is controlled within tight limits as this affects the fermentation products and hence characteristics of the final beer. After a few days, the sugar content and alcohol content reach a target value and the fermentation is stopped by cooling the beer below the yeast activation temperature. The yeast is removed and the beer is then pumped to conditioning tanks. It remains in these tanks for a few days to mature before being transferred to casks or bottles. Bottling involves an additional process to encourage further conditioning in the bottle. The bottled beer is not filtered or pasteurised so that the beer continues to develop once bottled as long as the environment is suitable. If the bottles are stored upright at 14-17 deg C, the yeast continues to ferment slightly and adds some condition to the beer. This yeast will also fall to the bottom of the bottle so the beer should be decanted in one go to prevent the yeast returning to suspension.
It is the control of this process from start to finish that ensures a high quality product. Realising this, we at 'Le Brewery' make great efforts to carefully control this process so that every bottle tastes as good as the last.
We look forward to your visit and feel sure you will enjoy our hand crafted traditional beers.
5.Write a brief note on Plant based fermented foods.
Miso is a traditional Japanese food produced by fermenting rice, barley and/or soybeans, with salt and the fungus kōjikin (the most typical miso is made with soy). The typical result is a thick paste used for sauces and spreads, pickling vegetables or meats, and mixing with dashi soup stock to serve as miso soup called Misoshiru a Japanese culinary staple. High in protein and rich in vitamins and minerals, miso played an important nutritional role in feudal Japan. Miso is still very widely used in Japan, both in traditional and modern cooking, and has been gaining world-wide interest. Miso is typically salty,
but its flavor and aroma depend on various factors in the ingredients and fermentation process. Different varieties of miso have been described as salty, sweet, earthy, fruity, and savory, and there is an extremely wide variety of miso available.
History
The predecessor of miso originated in China during the 3rd century BC or earlier, and it is probable that this, together with related fermented soy-based foods, was introduced to Japan at the same time as Buddhism in the 6th century AD
During the Edo period miso was also called hishio and kuki.
Until the Muromachi era, miso was made without grinding the soybeans, somewhat like natto. In the Kamakura era, a common meal was made up of a bowl of rice, some dried fish, a serving of miso, and a fresh vegetable. In the Muromachi era, Buddhist monks discovered that soybeans could be ground into a paste, spawning new cooking methods where miso was used to flavor other foods.
VarietyBy flavor
The taste, aroma, texture, and appearance of any specific miso vary by miso type as well as the region and season for which the miso was made. The ingredients used, temperature and duration of fermentation, salt content, variety of kōji, and fermenting vessel all contribute. The most common flavor categories of soy miso are:
Shiromiso, "white miso" Akamiso, "red miso"
Kuromiso, "black miso"
Hatchomiso
White and red (shiromiso and akamiso) are the basic types of miso available in all of Japan as well as overseas. Different varieties are preferred in particular regions. For example, in the eastern Kantō region that includes Tokyo, the lighter shiromiso is popular, while in the western Kansai region encompassing Osaka, Kyoto, and Kobe, darker brownish hatchomiso is preferred, and akamiso is favoured in the Tokai area.[citation
needed]
By ingredient
The raw materials used to produce miso may include any mix of soybeans, barley, rice, buckwheat, millet, rye, wheat, hemp seed, and cycad, among others. Lately, producers in other countries have also begun selling miso made from chick peas, corn, adzuki beans, amaranth, and quinoa. Fermentation time ranges from as little as five days to several
years. The wide variety of Japanese miso is difficult to classify, but is commonly done by grain type, color, taste, and background.
mugi : barley tsubu : whole wheat/barley
aka : red, medium flavor
hatchō : aged (or smoked), strongest flavor, along with 'shiro' is most commonly used
shiro : rice, sweet white, fresh, along with 'hatcho' is most commonly used
shinshu: rice, brown color
genmai : brown rice
awase : layered, typically in supermarket
moromi : chunky, healthy (kōji is unblended)
nanban : chunky, sweet, for dipping sauce
inaka : farmstyle
taima : hemp seed
sobamugi : buckwheat
hadakamugi : rye
meri : made from cycad pulp, Buddhist temple diet
gokoku : "5 grain": soy, wheat, barley, proso millet, and foxtail millet
Many regions have their own specific variation on the miso standard. For example, the soybeans used in Sendai miso are much more coarsely mashed than in normal soy miso.
Miso made with rice (including shinshu and shiro miso) is called kome miso.
Using misoStorage and preparation
Miso typically comes as a paste in a sealed container, and should be refrigerated after opening. It can be eaten raw, and cooking changes its flavor and nutritional value; when used in miso soup, most cooks do not allow the miso to come to a full boil. Some people, especially those outside of Japan, go so far as to only add miso to preparations after they have cooled, to preserve the biological activity of the kōjikin. Since miso and soy foods play a large role in the Japanese diet, there are a variety of cooked miso dishes as well.
In food
Miso is a part of many Japanese-style meals. It most commonly appears as the main ingredient of miso soup, which is eaten daily by much of the Japanese population. The pairing of plain rice and miso soup is considered a fundamental unit of Japanese cuisine. This pairing is the basis of a traditional Japanese breakfast.
Miso is used in many other types of soup and souplike dishes, including some kinds of ramen, udon, nabe, and imoni. Generally, such dishes have the title miso prepended to their name (for example, miso-udon), and have a heavier, earthier flavor and aroma compared to other Japanese soups that are not miso-based.
Many traditional confections use a sweet, thick miso glaze, such as mochidango. Miso glazed treats are strongly associated with Japanese festivals, although they are available year-round at supermarkets. The consistency of miso glaze ranges from thick and taffy-like to thin and drippy.
Soy miso is used to make a type of pickle called "misozuke".These pickles are typically made from cucumber, daikon, hakusai, or eggplant, and are sweeter and less salty than the standard Japanese salt pickle. Barley miso, or nukamiso, is used to make another type of pickle.[4] Nukamiso is a fermented product, and considered a type of miso in Japanese culture and linguistics, but does not contain soy, and so is functionally quite different. Like soy miso, nukamiso is fermented using kōji mold.
Other foods with miso as an ingredient include:
dengaku (charcoal-grilled miso covered tofu) yakimochi (charcoal-grilled miso covered mochi)
miso braised vegetables or mushrooms
marinades: fish or chicken can be marinated in miso and sake overnight to be grilled.
corn on the cob in Japan is usually coated with shiro miso, wrapped in foil and grilled.
sauces: sauces like misoyaki (a variant on teriyaki) are common.
Nutrition and health
The nutritional benefits of miso have been widely touted by commercial enterprises and home cooks alike. However, claims that miso is high in vitamin B12 have been contradicted in some studies [1]. Part of the confusion may stem from the fact that some soy products are high in B vitamins (though not necessarily B12), and some, such as soy milk, may be fortified with vitamin B12. Some, especially proponents of healthy eating, suggest that miso can help treat radiation sickness, citing cases in Japan and Russia where people have been fed miso after the Chernobyl nuclear disaster and the atomic bombings of Hiroshima and Nagasaki. Notably, Japanese doctor Shinichiro Akizuki, director of Saint Francis Hospital in Nagasaki during World War II, theorized that miso helps protect
against radiation sickness. Also some experts suggest that miso is a source of Lactobacillus acidophilus.
Olive:
The Olive (Olea europaea) is a species of small tree in the family Oleaceae, native to the coastal areas of the eastern Mediterranean region, from Lebanon, Syria and the maritime parts of Asia Minor and northern Iran at the south end of the Caspian Sea. Its fruit, the olive, is of major agricultural importance in the Mediterranean region as the source of olive oil.
Description
The Olive Tree is an evergreen tree or shrub native to the Mediterranean, Asia and parts of Africa. It is short and squat, and rarely exceeds 8–15 meters in height. The silvery green leaves are oblong in shape, measuring 4–10 cm long and 1–3 cm wide. The trunk is typically gnarled and twisted.
The small white flowers, with four-cleft calyx and corolla, two stamens and bifid stigma, are borne generally on the last year's wood, in racemes springing from the axils of the leaves.
The fruit is a small drupe 1–2.5 cm long, thinner-fleshed and smaller in wild plants than in orchard cultivars. Olives are harvested at the green stage or left to ripen to a rich purple colour (black olive). Canned black olives may contain chemicals that turn them black artificially.
History
The olive is one of the plants most cited in recorded literature. In Homer's Odyssey, Odysseus crawls beneath two shoots of olive that grow from a single stock.[1] The Roman poet, Horace mentions it in reference to his own diet, which he describes as very simple: "As for me, olives, endives, and smooth mallows provide sustenance."[2] Lord Monboddo comments on the olive in 1779 as one of the foods preferred by the ancients and as one of the most perfect foods.[3]
The leafy branches of the olive tree, olive leaf as a symbol of abundance, glory and peace, were used to crown the victors of friendly games and bloody war. As emblems of benediction and purification, they were also ritually offered to deities and powerful figures: some were even found in Tutankhamen's tomb.
Olive oil has long been considered sacred; it was used to anoint kings and athletes in ancient Greece. It was burnt in the sacred lamps of temples as well as being the "eternal flame" of the original Olympic Games. Victors in these games were crowned with its leaves. Today it is still used in many religious ceremonies.
According to Greek mythology the Olive tree, her gift to the people of Attica, won Athena the patronage of the city of Athens over Poseidon [4]
Cultivation and usesFor more details on this topic, see olive (fruit).
An example of black olives.
The olive tree has been cultivated since ancient times as a source of olive oil, fine wood, olive leaf, and olives for consumption. The naturally bitter fruit is typically subjected to fermentation or cured with lye or brine to make it more palatable.
Green olives and black olives are washed thoroughly in water to remove oleuropein, a bitter carbohydrate. Sometimes they are also soaked in a solution of food grade sodium hydroxide in order to accelerate the process.
Green olives are allowed to ferment before being packed in a brine solution. American black ("California") olives are not fermented, which is why they taste milder than green olives.
It is not known when olives were first cultivated for harvest. Among the earliest evidence for the domestication of olives comes from the Chalcolithic Period archaeological site of Teleilat Ghassul in what is today modern Jordan.
The plant and its products are frequently referred to in the Bible, the Book of Mormon, the Qur'an, and by the earliest recorded poets. Farmers in ancient times believed olive trees would not grow well if planted more than a short distance from the sea; Theophrastus gives 300 stadia (55.6 km) as the limit. Modern experience does not always confirm this, and, though showing a preference for the coast, it has long been grown further inland in some areas with suitable climates, particularly in the southwestern Mediterranean (Iberia, northwest Africa) where winters are mild.
Olive plantation in Andalucia, Spain.
Olives are now cultivated in many regions of the world with Mediterranean climates, such as South Africa, Chile, Australia, Mediterranean Basin, Israel, Palestinian Territories and California and in areas with temperate climates such as New Zealand, under irrigation in the Cuyo region in Argentina which has a desert climate. They are also grown in the Córdoba Province, Argentina, which has a temperate climate with rainy summers and dry winters (Cwa)[11]; the climate in Argentina changes the external characteristics of the plant but the fruit keeps its original characteristics [12]. Considerable research supports the health-giving benefits of consuming olives, olive leaf and olive oil (see external links below for research results).
The olive tree provides leaves, fruit and oil. Olive leaves are used in medicinal teas.
Subspecies
There are at least five natural subspecies distributed over a wide range:
Olea europaea subsp. europaea (Europe) Olea europaea subsp. cuspidata (from Eritrea and Ethiopia south throughout East Africa,
also in Iran to China)
Olea europaea subsp. guanchica (Canaries)
Olea europaea subsp. maroccana (Morocco)
Olea europaea subsp. laperrinei (Algeria, Sudan, Niger, India)
Cultivars
Small Olive Tree
Large Olive Tree
Olive Tree Leaves
Olive Tree Trunk
Olive Flowers
A young olive plant, germinated from a seed
Monumental tree in Apulia Region - Southern Italy
There are thousands of cultivars of the olive. In Italy alone at least three hundred cultivars have been enumerated, but only a few are grown to a large extent. The main Italian cultivars are 'Leccino', 'Frantoio' and 'Carolea'. None of these can be accurately identified with ancient descriptions, though it is not unlikely that some of the narrow-leaved cultivars most esteemed may be descendants of the Licinian olive. The Iberian olives are usually cured and eaten, often after being pitted, stuffed (with pickled pimento, anchovies, or other fillings) and packed in brine in jars or tins.
Since many cultivars are self sterile or nearly so, they are generally planted in pairs with a single primary cultivar and a secondary cultivar selected for its ability to fertilize the primary one, for example, 'Frantoio' and 'Leccino'. In recent times, efforts have been directed at producing hybrid cultivars with qualities such as resistance to disease, quick growth and larger or more consistent crops.
Some particularly important cultivars of olive include:
'Manzanillo', a large, rounded-oval fruit, with purple-green skin. Rich taste and thick pulp. A prolific bearer, grown around the world.
'Frantoio' and 'Leccino'. These cultivars are the principal participants in Italian olive oils from Tuscany. Leccino has a mild sweet flavour while Frantoio is fruity with a stronger aftertaste. Due to their highly valued flavour, these cultivars are now grown in other countries.
'Arbequina' is a small, brown olive grown in Catalonia, Spain, good for eating and for oil.
'Empeltre' is a medium-sized black olive grown in Spain, good for eating and for oil.
'Kalamata' is a large, black olive with a smooth and meatlike taste, named after the city of Kalamata, Greece, used as a table olive. These olives are usually preserved in vinegar or olive oil. Kalamata olives enjoy PDO (Protected designation of origin) status.[13]
'Koroneiki' originates from the southern Peloponese, around Kalamata and Mani in Greece. This small olive, though difficult to cultivate, has a high yield of olive oil of exceptional quality.
'Pecholine' or 'picholine' originated in the south of France. It is green, medium size, and elongated. The flavour is mild and nutty.
'Lucques' originated in the south of France (Aude département). They are green, large, and elongated. The stone has an arcuated shape. Their flavour is mild and nutty.
'Souri' (Syrian) originated in Lebanon and is widespread in the Levant. It has a high oil yield and exceptionally aromatic flavour.
'Nabali' is a Palestinian cultivar[14] also known locally as 'Baladi', which along with 'Souri' and 'Malissi' are considered to produce among the highest quality olive oil in the world.[15]
'Barnea' is a modern cultivar bred in Israel to be disease-resistant and to produce a generous crop. It is used both for oil and for table olives. The oil has a strong flavour with
a hint of green leaf. Barnea is widely grown in Israel and in the southern hemisphere, particularly in Australia and New Zealand.
'Maalot' (Hebrew for merits) is another modern Israeli, disease-resistant, Eastern Mediterranean cultivar derived from the North African 'Chemlali' cultivar. The olive is medium sized, round, has a fruity flavour and is used almost exclusively for oil production.
'Mission' originated on the California Missions and is now grown throughout the state. They are black and generally used for table consumption.
Growth and propagation
Olive trees show a marked preference for calcareous soils, flourishing best on limestone slopes and crags, and coastal climate conditions. They tolerate drought well, thanks to their sturdy and extensive root system. Olive trees can be exceptionally long-lived, up to several centuries, and can remain productive for as long, provided they are pruned correctly and regularly.
The olive tree grows very slowly, but over many years the trunk can attain a considerable diameter. A. P. de Candolle recorded one exceeding 10 m in girth. The trees rarely exceed 15 m in height, and are generally confined to much more limited dimensions by frequent pruning. The yellow or light greenish-brown wood is often finely veined with a darker tint; being very hard and close-grained, it is valued by woodworkers.
The olive is propagated in various ways, but cuttings or layers are generally preferred; the tree roots easily in favourable soil and throws up suckers from the stump when cut down. However, yields from trees grown from suckers or seeds are poor; it must be budded or grafted onto other specimens to do well (Lewington and Parker, 114). Branches of various thickness are cut into lengths of about 1 m and, planted deeply in manured ground, soon vegetate; shorter pieces are sometimes laid horizontally in shallow trenches, when, covered with a few centimetres of soil, they rapidly throw up sucker-like shoots. In Greece, grafting the cultivated tree on the wild form is a common practice. In Italy, embryonic buds, which form small swellings on the stems, are carefully excised and planted beneath the surface, where they grow readily, their buds soon forming a vigorous shoot.
Occasionally the larger boughs are marched, and young trees thus soon obtained. The olive is also sometimes raised from seed, the oily pericarp being first softened by slight rotting, or soaking in hot water or in an alkaline solution, to facilitate germination.
Where the olive is carefully cultivated, as in Languedoc and Provence, the trees are regularly pruned. The pruning preserves the flower-bearing shoots of the preceding year, while keeping the tree low enough to allow the easy gathering of the fruit. The spaces between the trees are regularly fertilized. The crop from old trees is sometimes enormous, but they seldom bear well two years in succession, and in many instances a large harvest can only be reckoned upon every sixth or seventh season.
A calcareous soil, however dry or poor, seems best adapted to its healthy development, though the tree will grow in any light soil, and even on clay if well drained; but, as remarked by Pliny, the plant is more liable to disease on rich soils, and the oil is inferior to the produce of the poorer and more rocky ground.
In general, a temperature below 14 °F (-10 °C) may cause considerable injury to a mature tree, but (with the exception of juvenile trees) a temperature of 16 °F (-9 °C) will normally cause no harm.
Fruit harvest and processing
Most olives today are harvested by shaking the boughs or the whole tree. Another method involves standing on a ladder and "milking" the olives into a sack tied around the harvester's waist.Using olives found lying on the ground can result in poor quality oil.
In southern Europe the olive harvest is in winter, continuing for several weeks, but the time varies in each country, and also with the season and the kinds cultivated. A device called the oli-net wraps around the trunk of the tree and opens to form an umbrella-like catcher; workers can then harvest the fruit without the weight of the load around their neck. Another device, the oliviera, is an electronic tool that connects to a battery. The oliviera has large tongs that are spun around quickly, removing fruit from the tree. This method is used for olives used for oil. Table olive varieties are more difficult to harvest, as workers must take care not to damage the fruit; baskets that hang around the worker's neck are used.
The amount of oil contained in the fruit differs greatly in the various cultivars; the pericarp is usually 60–70% oil. Typical yields are 1.5-2.2 kg of oil per tree per year.
Traditional fermentation
Olives freshly picked from the tree contain phenolic compounds and oleuropein, a glycoside which makes the fruit unpalatable for immediate consumption. There are many ways of processing olives for table use. Traditional methods use the natural microflora on the fruit and procedures which select for those that bring about fermentation of the fruit. This fermentation leads to three important outcomes: the leaching out and breakdown of oleuropein and phenolic compounds; the creation of lactic acid, which is a natural preservative; and a complex of flavoursome fermentation products. The result is a product which will store with or without refrigeration.
One basic fermentation method is to get food grade containers, which may include plastic containers from companies which trade in olives and preserved vine leaves. Many bakeries also recycle food grade plastic containers which are well sized for olive fermentation; they are 10 to 20 litres in capacity. Freshly picked olives are often sold at markets in 10 kg trays. Olives should be selected for their firmness if green and general good condition. Olives can be used green, ripe green (which is a yellower shade of green, or green with hints of color), through to full purple black ripeness. The olives are soaked
in water to wash them, and drained. 7 litres (which is 7 kg) of room temperature water is added to the fermentation container, and 800 g of sea salt, and one cup (300g) of white vinegar (white wine or cider vinegar). The salt is dissolved to create a 10% solution (the 800 g of salt is in an 8 kg mixture of salt and water and vinegar). Each olive is given a single deep slit with a small knife (if small), or up to three slits per fruit (if large, eg 60 fruit per kg). If 10 kg of olives are added to the 10% salt solution, the ultimate salinity after some weeks will be around 5 to 6% once the water in the olives moves into solution and the salt moves into the olives. The olives are weighed down with an inert object such as a plate so they are fully immersed and lightly sealed in their container. The light sealing is to allow the gases of fermentation to escape. It is also possible to make a plastic bag partially filled with water, and lay this over the top as a venting lid which also provides a good seal. The exclusion of oxygen is useful but not as critical as when grapes are fermented to produce wine. The olives can be tasted at any time as the bitter compounds are not poisonous, and oleuropein is a useful antioxidant in the human diet.
The olives are edible within 2 weeks to a month, but can be left to cure for up to three months. Green olives will usually be firmer in texture after curing than black olives. Olives can be flavored by soaking them in various marinades, or removing the pit and stuffing them. Herbs, spices, olive oil, feta, capsicum (pimento), chili, lemon zest, lemon juice, garlic cloves, wine, vinegar, juniper berries, and anchovies are popular flavorings. Sometimes the olives are lightly cracked with a hammer or a stone to trigger fermentation. This method of curing adds a slightly bitter taste.
6.Write a brief note on Tempeh Production.
Tempeh is a nutritional super hero. It is high in protein, dietary fiber, iron, potassium, calcium, and phytochemicals like isoflavones. It has been shown to lower cholesterol, high blood pressure and the risk of heart attack and stroke; reduce the risk of some cancers, like colon, breast, ovarian and prostate; ease certain menopausal symptoms; prevent and possibly even reverse the effects of osteoporosis and diabetes. To obtain these protective properties, researchers recommend consuming a minimum of 25 grams soy protein and 30-50 milligrams isoflavones daily. This works out to about 1-2 servings a day. One serving of tempeh, which is 1/2 cup (4 ounces), provides on average 19 grams soy protein, 60 milligrams isoflavones and 7 grams dietary fiber (28% RDA). Tempeh made with only soybeans has more soy protein and isoflavones than those with added grain. Whatever variety you choose, tempeh is the best source and easiest way to get lots of high quality protein, isoflavones and fiber in a minimally processed soy food. Each serving also supplies about 100 milligrams calcium (10% RDA), 550 milligrams potassium (16% RDA), and 5 milligrams iron (30% RDA).
2. Tempeh is a great choice for people who have difficulty digesting plant-based high-protein foods like beans and legumes or soy foods such as tofu. Because tempeh is a fermented soy product, its enzymes are partially broken down, making it easier to metabolize. It does not produce the unpleasant gastrointestinal discomfort and gas that some other plant-based proteins do. This fermentation process actually allows your body to more easily assimilate and absorb tempeh's nutrients. Besides being a terrific cholesterol-free easy-to-digest meat alternative, it is
also ideal for people on low sodium diets. Unlike other fermented soy products, like miso which is very salty, tempeh is extremely low in sodium.
3. Tempeh has a pleasant, wonderfully unique nutty/mushroom flavor. It's rich and savory taste and firm texture makes it easy to create fantastic meals without a lot of fuss. It does not need much preparation or cooking time, making it a marvelously healthy fast food. Just add a little soy sauce or liquid hickory smoke seasoning to enhance its flavor. Then stir-fry, sauté, microwave, stew or bake it to make a variety of delightful dishes and sandwiches. To make a hearty entree in a short amount of time, all you need is tempeh, onions, mushrooms, peppers, olive oil, liquid seasoning, and some cooked brown rice or pasta. Thinly slice the tempeh. Sprinkle some soy sauce or liquid hickory (or mesquite) smoke seasoning on both sides of the slices. Slice the onions, mushrooms and peppers, and sauté in a little olive oil for a few minutes. Add the seasoned tempeh slices and sauté until lightly browned. Salt and pepper to taste.
7. Write a brief note on Country Salt Cured Ham and Bacon.The dilemma facing pioneer mountain cooks was how to keep freshly butchered meat from spoiling without refrigeration. Hogs were butchered in the late fall when the temperature was down around 33 degrees, and while the meat was fresh, it was salt cured. The next spring any leftovers would be smoked under a fire of green hickory or peppered. Sausage was packed in the intestines of the hog, tied off and also hung in the smokehouse for curing. Salting, peppering, and smoking protected the meat from spoiling and from insects. Today it's that salt, pepper, and smoky flavor that we love in country ham, bacon, and sausage.
Clifty Farm's Country Ham
Clifty Farms country ham is from Tennessees oldest smokehouse. Slow bake or boil this salt cured and hickory smoked ham to serve with your home made biscuits or rolls and your holiday dinner will be one to remember. Serve lightly re-fried leftovers at breakfast with red-eye gravy. Four hours soaking recommended. Ogi:
Ogi is a fermented cereal porridge from West Africa, typically made from maize, sorghum, or millet. Traditionally, the grains are soaked in water for up to three days, before wet milling and sieving to remove husks. The filtered cereal is then allowed to ferment for up to three days until sour. It is then boiled into a pap, or cooked to make a stiff porridge.
The fermentation of ogi is performed by various lactic acid bacteria including Lactobacillus spp, and various yeasts including Saccharomyces and Candida spp.
Soy sauce:
Soy sauce (US), soya sauce (Commonwealth), or shoyu (Japan) is a fermented sauce made from soybeans (soya beans), roasted grain, water and salt. Soy sauce was invented in China, where it has been used as a condiment for close to 2,500 years. In its various
forms it is widely used in East and Southeast Asian cuisines and increasingly appears in Western cuisine and prepared foods.
Production
Soy sauce is made from soybeans.
Traditional
Authentic soy sauces are made by mixing the grain and/or soybeans with yeast or kōji (麹, the mold Aspergillus oryzae or A. sojae) and other related microorganisms. Traditionally soy sauces were fermented under natural conditions, such as in giant urns and under the sun, which was believed to contribute to additional flavours. Today, most of the commercially-produced counterparts are fermented under machine-controlled environments instead.
Although there are many types of soy sauce, all are salty and earthy-tasting brownish liquids used to season food while cooking or at the table. Soy sauce has a distinct basic taste called umami by the Japanese (鮮 味 , literally "fresh taste"). Umami was first identified as a basic taste in 1908 by Kikunae Ikeda of the Tokyo Imperial University. The free glutamates which naturally occur in soy sauce are what give it this taste quality.
Soy sauce should be stored away from direct sunlight.
Artificially hydrolyzed
Many cheaper brands of soy sauces are made from hydrolyzed soy protein instead of brewed from natural bacterial and fungal cultures. These soy sauces do not have the
natural color of authentic soy sauces and are typically colored with caramel coloring, and are popular in Southeast Asia and China, and are exported to Asian markets around the globe. They are derogatorily called Chemical Soy Sauce "化學醬油" in Chinese, but despite this name are the most widely used type because they are cheap. Similar products are also sold as "liquid aminos" in the US and Canada.
Some artificial soy sauces posed potential health risks due to their content of the chloropropanols carcinogens 3-MCPD (3-chloro-1,2-propanediol) and all artificial soy sauces pose health risks due to the unregulated 1,3-DCP (1,3-dichloro-2-propanol) which are minor byproducts of the hydrochloric acid hydrolysis [1].
Types
Soy sauce has been integrated into the traditional cuisines of many East Asian and South East Asian cultures. Soy sauce is widely used as a particularly important flavoring in Japanese, Thai, and Chinese cuisine. However, it is important to note that despite its rather similar appearance, soy sauces produced in different cultures and regions are very different in taste, consistency, fragrance and saltiness. As such, it may not be appropriate to substitute soy sauces of one culture or region for another.
Chinese soy sauce
A bottle of Chinese soy sauce, artificially hydrolyzed, as clearly evident from the discoloration of the bottle due to addition of caramel coloring to mask the production method
Chinese soy sauce (simplified Chinese:; traditional Chinese:; pinyin: jiàngyóu; or chǐyóu) is primarily made from soybeans, with relatively low amounts of other grains. There are two main varieties:
Light or fresh soy sauce :A thin (non-viscous), opaque, dark brown soy sauce. It is the main soy sauce used for seasoning, since it is saltier, but it also adds flavour. Since it is lighter in color, it does not greatly affect the color of the dish. The light soy sauce made from the first pressing of the soybeans is called tóuchōu (simplified Chinese: 头抽; traditional Chinese: 頭抽), which can be loosely translated as first soy sauce or referred to as premium light soy sauce. Touchōu is sold at a premium because, like extra virgin olive oil, the flavor of the first pressing is considered superior. An additional classification of light soy sauce, shuānghuáng (雙 璜 ), is double-fermented to add further complexity to the flavour. These latter two more delicate types are usually for dipping.
Dark/old soy sauce: A darker and slightly thicker soy sauce that is aged longer and contains added molasses to give it its distinctive appearance. This variety is mainly used during cooking since its flavour develops under heating. It has a richer, slightly sweeter, and less salty flavour than light soy sauce. Dark soy sauce is partly used to add color and flavour to a dish.
In traditional Chinese cooking, one of the two types, or a mixture of both, is employed to achieve a particular flavour and colour for the dish.
Other types:
Thick soy sauce :Dark soy sauce that has been thickened with starch and sugar. It is also occasionally flavored with MSG. This sauce is not usually used directly in cooking but more often as a dipping sauce or poured on food as a flavorful addition.
Dark soy paste : Although not really a soy sauce, it is another salty soy product. It is one of the main ingredients in a dish called zhajiang mian, lit. "fried paste noodles").
Japanese soy sauce
Koyo organic tamari sauce
Buddhist monks introduced soy sauce into Japan in the 7th century, where it is known as "shoyu". The Japanese word "tamari" is derived from the verb "tamaru" that signifies "to
accumulate," referring to the fact that tamari was traditionally from the liquid byproduct produced during the fermentation of miso. Japan is the leading producer of tamari.
Japanese soy sauce or shō-yu, is traditionally divided into 5 main categories depending on differences in their ingredients and method of production. Japanese soy sauces include wheat as a primary ingredient and this tends to give them a slightly sweeter taste than their Chinese counterparts. They also have an alcoholic sherry-like flavor. Not all soy sauces are interchangeable.
Koikuchi
Originating in the Kantō region, its usage eventually spread all over Japan. Over 80% of the Japanese domestic soy sauce production is of koikuchi, and can be considered the typical Japanese soy sauce. It is produced from roughly equal quantities of soybean and wheat. This variety is also called kijōyu (生 醤 油 ) or namashōyu (生しょうゆ) when it is not pasteurized.
Usukuchi
Particularly popular in the Kansai region of Japan, it is both saltier and lighter in color than koikuchi. The lighter color arises from the usage of amazake, a sweet liquid made from fermented rice, that is used in its production.
Tamari
Produced mainly in the Chūbu region of Japan, tamari is darker in appearance and richer in flavour than koikuchi. It contains little or no wheat; wheat-free tamari is popular among people eating a wheat free diet. It is the "original" Japanese soy sauce, as its recipe is closest to the soy sauce originally introduced to Japan from China. Technically, this variety is known as miso-damari (味噌溜り), as this is the liquid that runs off miso as it matures.
Shiro ("white")
A very light colored soy sauce. In contrast to "tamari" soy sauce, "shiro" soy sauce uses mostly wheat and very little soybean, lending it a light appearance and sweet taste. It is more commonly used in the Kansai region to highlight the appearances of food, for example sashimi.
Saishikomi ("twice-brewed")
This variety substitutes previously-made koikuchi for the brine normally used in the process. Consequently, it is much darker and more strongly flavored. This type is also known as kanro shoyu (甘露醤油) or "sweet shoyu".
Shoyu (koikuchi) and light colored shoyu (usukuchi) as sold in Japan by Kikkoman, 1 litre bottles.
Newer varieties of Japanese soy sauce include:
Gen'en ("reduced salt")
Low-salt soy sauces also exist, but are not considered to be a separate variety of soy sauce, since the reduction in salt content is a process performed outside of the standard manufacture of soy sauce.
Amakuchi
Called "Hawaiian soy sauce" in those few parts of the US familiar with it, this is a variant of "koikuchi" soy sauce.
All of these varieties are sold in the marketplace in three different grades according to how they were produced:
Honjōzō hōshiki
Contains 100% naturally fermented product.
Shinshiki hōshiki
Contains 30-50% naturally fermented product.
Tennen jōzō
Means no added ingredients except alcohol.
All the varieties and grades may be sold according to three official levels of quality:
Hyōjun
Standard pasteurized.
Tokkyū
Special quality, not pasteurized.
Tokusen
Premium quality, usually implies limited quantity.
Other terms unrelated to the three official levels of quality:
Hatsuakane
Refers to industrial grade used for flavoring, powder.
Chōtokusen
Used by marketers to imply the best.
Perhaps the most well-known producer of Japanese soy sauce is the Kikkoman Corporation.
Taiwanese soy sauce
The history of soy sauce making in Taiwan can be traced back to southeastern China, in the provinces of Fujian and Guangdong. Later, the cultural and political separation between Taiwan and China since the end of the First Sino-Japanese War in 1895, when China ceded Taiwan to Japan, brought changes to traditional Chinese soy sauce making in Taiwan. Some of the top Taiwanese makers, such as Wan Ja Shan, Wei-Wong and Ve-Chung have adopted the more sophisticated Japanese technology in making soy sauce for the domestic market and more recently foreign markets as well.
Korean soy sauce
Korean soy sauce, (called Joseon ganjang, 조선간장, in Korean) is a byproduct of the production of doenjang (Korean fermented soybean paste). Joseon ganjang, thin and dark brown in color, is made entirely of soy and brine, and has a saltiness that varies according to the producer. Wide scale use of Joseon ganjang has been somewhat superseded by cheaper factory-made Japanese style soy sauce, called waeganjang (hangul). Currently, Korean soy sauce is made from dripping soy sauce chicken into a pan. This process is widely used because in the process of making soy sauce, you get the benefit of regular chicken. According to the 2001 national food consumption survey in Korea, traditional fermented ganjang comprised only 1.4% of soy sauce purchases.
Vietnamese soy sauce
Vietnamese soy sauce is called xì dầu, nước tương, or sometimes simply tương.
Indonesian soy sauce
Kecap manis Indonesian thick and sweet soy sauce is nearly as thick as molasses.
In Indonesia, soy sauce is known as kecap (or ketjap) (a catchall term for fermented sauces) from which according to one theory the English word "ketchup" is derived. Two main varieties exist:
Kecap asin
Salty soy sauce, which is very similar to Chinese light soy sauce, but usually somewhat thicker and has a stronger flavor; it can be replaced by light Chinese soy sauce in recipes.
Kecap manis
Sweet soy sauce, which has a thick, almost syrupy consistency and a pronounced sweet, treacle-like flavor due to generous addition of palm sugar. It is a unique variety; in a pinch, it may be replaced by molasses with a little vegetable stock stirred in.
Kecap inggris ("English fermented sauce"), or saus inggris ("English sauce") is the Indonesian name for Worcestershire sauce. Kecap Ikan is Indonesian fish sauce.
Malaysian soy sauce
In Singapore and Malaysia, soy sauce in general is dòuyóu (豆油); dark soy sauce is called jiàngyóu (醬油) and light soy sauce is jiàngqīng (醬清). Angmoh tauyew (紅貌豆油, lit. "foreigners' soy sauce") is the Hokkien name for Worcestershire sauce.
Malaysia, which has cultural links with Indonesia, uses the word 'kicap' for soy sauce. Kicap is traditionally of two types: kicap lemak and kicap cair. Kicap lemak is similar to kecap manis but with very much less sugar while kicap cair is the Malaysian equivalent of kecap asin.
Filipino toyo
A popular condiment in the Philippines, it is called toyo (pronounced TOH-yoh), and is usually found beside other sauces such as patis (fish sauce, pronounced pah-TEES) and suka (sugar cane vinegar, pronounced SOO-kah). The flavor of Filipino soy sauce, made from soybeans, wheat, salt, and caramel, is interestingly milder compared to its Asian counterparts--possibly an adaptation to the demands of the Filipino palate and its cuisine. It is thinner in texture and has a saltier taste compared to its Southeast Asian counterparts, much more similar to the Japanese shōyu. It is used as a staple condiment to flavor many cooked dishes and as a marinade during cooking, it is also a table condiment, and is usually mixed and served with kalamansi (a small Asian citrus-lime). Popular Philippine brands are Marca Piña, Silver Swan, Lauriat, Datu Puti, Toyomansi and UFC (Universal Food Public Company).
Hawaiian shoyu
A unique type of soy sauce produced by Aloha Shoyu Company since 1946 is a special blend of soybeans, wheat, and salt, historically common among local Hawaii residents. Hawaii residents rarely use the term "soy sauce," opting to use the Japanese loanword "shoyu" instead. However, while the Japanese word shōyu is pronounced like show you, Hawaii residents prounounce the word like shoi-yu.
8.Write a brief note on Dry Sausage Preparation.
Dry Sausage:
A sausage is a prepared food, usually made from ground meat, animal fat, salt, and spices (sometimes with other ingredients such as herbs), typically packed in a casing. Sausage making is a traditional food preservation technique.
Traditionally, casings are made of animal intestines though are now often synthetic. Some sausages are cooked during processing, and the casing may be removed after that. Sausages may be preserved by curing, drying in cool air, or smoking. When cooking
sausages it is important to ensure they are pricked with a fork or similar implement first in order to prevent their disintegration and to prevent loss of flavour.
Classification of sausages
Sausages from Reunion Island
Swojska (Polish)
Krajańska (Polish)
Szynkowa (Polish)
A frankfurter sausage contains a lot of protein, yet low calories/fat (for meat)
Sausages may be classified in any number of ways, for instance by the type of meat and other ingredients they contain, or by their consistency. The most popular classification is probably by type of preparation, but even this is subject to regional differences of opinion. In the English-speaking world, the following distinction between fresh sausages, cooked sausages and dry sausages seems to be more or less accepted:
Cooked sausages are made with fresh meats and then fully cooked. They are either eaten immediately after cooking or must be refrigerated. Examples include hot dogs, Braunschweiger and liver sausages.
Cooked smoked sausages are cooked and then smoked or smoke-cooked. They are eaten hot or cold, but need to be refrigerated. Examples include Gyulai kolbász, kielbasa and Mortadella.
Fresh sausages are made from meats that have not been previously cured. They must be refrigerated and thoroughly cooked before eating. Examples include Boerewors, Italian pork sausage, breakfast sausage and Yarraque.
Fresh smoked sausages are fresh sausages that are smoked. They should be refrigerated and cooked thoroughly before eating. Examples include Mettwurst and Romanian sausage.
Dry sausages are cured sausages that are fermented and dried. They are generally eaten cold and will keep for a long time. Examples include salami, Droë wors, Sucuk, Landjäger, and summer sausage.
The distinct flavor of some sausages is due to fermentation by Lactobacillus, Pediococcus and/or Micrococcus (added as starter cultures) or natural flora during curing.
Other countries, however, use different systems of classification. Germany, for instance, which boasts more than 1200 types of sausage, distinguishes raw, cooked and pre-cooked sausages.
Raw sausages are made with raw meat and are not cooked. They are preserved by lactic acid fermentation, and may be dried, brined or smoked. Most raw sausages will keep for a long time. Examples include cervelat, mettwurst and salami.
Cooked sausages may include water and emulsifiers and are always cooked. They will not keep long. Examples include Jagdwurst and Weißwurst.
Pre-cooked sausages are made with cooked meat, and may include raw organ meat. They may be heated after casing, and will keep only for a few days. Examples include Saumagen and Blutwurst.
In Italy, the basic distinction is:
Raw sausage (salsiccia) Cured or cooked sausage (salume)
The US has a particular type called pickled sausages, commonly found in gas stations and small roadside delicatessens. These are usually smoked and/or boiled sausages of a highly processed frankfurter (hot dog) or kielbasa style plunged into a boiling brine of vinegar, salt, spices (red pepper, paprika...) and often a pink coloring, then canned in wide-mouth jars. They are available in single blister packs, e.g., Slim Jim meat snacks, or in jars atop the deli cooler. They are shelf stable, and are a frequently offered alternative to beef jerky, beef stick, and kippered beef snacks.
Certain countries classify sausage types according to the region in which the sausage was traditionally produced:
France : Montbéliard, Morteau, Strasbourg, Toulouse, Merguez... Germany : Frankfurt, Thuringia, Nuremberg, Pomerania, ...
Austria : Vienna, ...
Italy : Merano (Meran)
UK : Cumberland, Chiltern, Lincolnshire, Glamorgan ...
Slovenia : Kranjska (klobasa), after the Slovenian name for the province of Carniola
Spain : botifarra catalana, chorizo riojano, chorizo gallego, chorizo de Teror, longaniza de Aragón, morcilla de Burgos, morcilla de Ronda, morcilla extremeña, morcilla dulce canaria, llonganissa de Vic, fuet d'Olot, sobrassada mallorquina, botillo de León, llonganissa de Valencia, farinato de Salamanca, ...
Poland : kielbasa krakowska (Kraków-style), toruńska (Toruń), żywiecka (Żywiec), bydgoska (Bydgoszcz), krotoszyńska (Krotoszyn), podwawelska (literally: "from under Wawel"), zielonogórska (Zielona Góra), rzeszowska (Rzeszów), śląska (Silesia), swojska, wiejska, jałowcowa, zwyczajna, polska, krajańska, szynkowa, parówkowa ...
Hungary : kolbász gyulai (after the town of Gyula), csabai (after the city of Békéscsaba), Debrecener (after the city of Debrecen).
9.Write a brief note on Katsuobushi Preparation.
Katsuobushi:
Katsuobushi is the Japanese name for a preparation of dried, fermented, and smoked skipjack tuna (Katsuwonus pelamis, sometimes referred to as bonito). Katsuobushi and kombu (a type of kelp) are the main ingredients of dashi, a broth that forms the basis of many soups (such as miso soup) and sauces (e.g., soba no tsukejiru) in Japanese cuisine. It is today typically found in bags of small pink-brown shavings. Larger, thicker shavings, called kezurikatsuo, are used to make the ubiquitous dashi stock. Smaller, thinner shavings, called hanakatsuo, are used as a flavoring and topping for many Japanese dishes, such as okonomiyaki. Traditionally, large chunks of katsuobushi were kept at hand and shaved when needed with an instrument called a katsuobushi kezuriki, similar to a wood plane, but in the desire for convenience this form of preparation has nearly disappeared. Katsuobushi, however, retains its status as one of the primary ingredients in Japanese cooking today.
Katsuobushi's umami flavor comes from its high inosinic acid content. Traditionally made katsuobushi, known as karebushi, is deliberately planted with fungus (Aspergillus glaucus) in order to reduce moisture.
When hanakatsuo is added as a topping to a hot dish, the steam has the effect of making the flakes move as if dancing; because of this, katsuobushi topping is also known as dancing fish flakes.
Uses
Other than the main ingredient of dashi stock, other popular uses of katsuobushi include:
Okaka, finely chopped katsuobushi dressed with soy sauce. o As a stuffing for rice balls (onigiri).
o As a topping for rice. Popular for bentō, often covered with nori. A bentō with okaka and nori is called "nori-ben".
o Dried okaka is used as an indredient of furikake rice topping (called "okaka furikake").
As a seasoning for cold tofu along with grated ginger and Welsh onion (a type of spring onion.)
Sprinkled with sesame seeds and chopped nori atop cold soba noodles (zarusoba).
As a topping on takoyaki and okonomiyaki.
As a seasoning on century egg along with sesame oil and soy sauce.
As a high-protein treat for cats sold at pet stores.
Popular culture Katsuobushi was the inspiration for the title of the John Lennon album Shaved Fish. The original Iron Chef Japanese on the television show Iron Chef, Rokusaburo Michiba,
was known on the show for his trademark "broth of vigor", created from katsuobushi.
10.Write a brief note on fermented dairy products.
KEFIRIntroduction:
Kefir is the self-carbonated fermented milk product with high nutritional status and therapeutic value.
It requires a special culture called kefir grains. The grain consists of casein and gelatinous colonies of microorganisms, which live,
in symbiosis. The organism isolated is yeast such as Torula and Saccharomyces kefir and bacteria
such as L.acidophilus, Streptococcus lactis and L.kefiranofaciens. The yeast represents 5 – 10 % of the total micro flora. The grains are irregular in shape, yellowish in color and insoluble in water. Dried grains retain their activity for more than a year when stepped in milk the grains
swell. During fermentation process Lactobacillus sp. produces lactic acid and lacto
fermenting yeast cell produce alcohol and CO2. All activities are controlled by incubation temperature.
Uses:
Starter organisms produce risin, lactimine, streptocine is widely used in hospitals. It is included in diets of patients suffering from intestinal diseases, anemia,
metabolic disorders, hyper toxicity, and allergic diseases. It is beneficial for the treatment of tuberculosis. The product in diet reduces serum cholesterol level in infants.
CULTURED BUTTER MILKUses:
1) It is highly nutritious and suited as a supplement to local foods.2) Fermentation predigests several milk constituents, synthesizes water soluble
vitamin of B complex and makes a nutritionally upgraded milk.It is a fermented product made by using mesophilic starters.
Production:
Milk free from antibiotics & detergents with fat content of 0.5 – 1 % is homogenized at 150c
Heated at 900c – 13 mins & cooled to 230c.
Starter culture [Str. lactis, Str. cremoris – acid production, Str. diacetylactis, Leuconostoc citrovorum – aroma & flavor 1-2%].
Fermentation time is 16 – 20 hrs, acidity – 0.9%, mixed, cooled, bottled & stored at 50c.
Final product is viscous, drink with pleasing aroma, flavour.
KUMISS Prepared from mare milk, which is inoculated with starter culture of 10 – 20%. Cow milk or skimmed milk with 2.5% sucrose is used due to non-availability of mare
milk. Microflora includes Lactobacillus delbrueckeii ssp bulgaricus, L. acidophilus,
Kluveromyces lactis.Use:
Kumiss from mare milk is a good supplementary remedy for treatment of TB.BUTTER
Introduction:
Butter is a concentrate of one of the 3 main constituents of milk ie., fat, proteins, lactose. The later 2 are present only in small proportion. Butterfat also contains the yellow coloring matter carotine and or its transformation products vitamin A and D.
Composition:
Butter and moisture à 16%
Milk fat à 80%
Milk solids à 2%
Butter making process:
1.Preparation of cream, pasteurization, cooling and starter addition:
Cream is produced by mechanical separation of unhomogenized whole milk. Cream is pasteurized between 88 – 930 c. It may be subjected to vacuum cooling to ripening temperature of 16-210 c and ripened with 4% of mixed starter culture having;
1.acid producers like Streptococci lactis /S.cremoris.
2.flavor producers like L.mesenteroides, S.diacetylactics.
The ripening may be in 2/3 stages to produce soft, firm butter.
2. Churning, washing and salting:
The cream is loaded for churning in machines. The machine has 3 sections;
1.churning
2.separating
3.working sections
The churning section consists of a horizontal cylinder and a rotating variable speed rotator/beater [0-1000 rpm] since churning lasts for 1-2 sec it is important to adjust the beater velocity to obtain optimum butter grain size.
The separating section consists of a horizontal cylinder. The first part of the cylinder is equipped with beaters for further treatment mixtures of butter grains and butter milk which is fed from the churning sections.
The second part of the cylinder is designed as a sieve for draining buttermilk. It is equipped with wire gauze, which retains even small butter grains.
The working section consists of inclined sections for transport of the butter. In the production of salted butter, a salt slurry [40-60%] is pumped into the first working section, in which it is worked into the butter before butter proceeds to the second working section. Any
adjustment of butter moisture also takes place in the first working section. Water dosing is done automatically.
Quality of wash water:
The chill water used for washing butter granules is an important source of contamination of butter. The treatment of butter with wash water has 2 purposes:
1. To wash away the free butter milk from the butter granules.2. To control the temperature of the granules for subsequent working process. The
following organisms are known to infect butter through wash water.[P.putrifaciens, P.fluorescens, P.fragi, P.methicica]
Packaging:
Butter is packed either in bulk or in consumer’s size containers. Normally vegetable parchment is used to line butter boxes and also a wrapper for consumer packs. Polyethylene films replace parchment paper. Giving sodium propionate treatment can control mold growth.Flavor of butter:
The flavor of butter is produced by the fermentation of citric acid by Leuconostoc and Streptococcus lactis. Citric acid is converted into pyruvate, co2 , acetic acid. Pyruvate is again metabolized to form CO2 and acetaldehyde. Acetaldehyde under neutral and acidic conditions forms acetic acid and ethanol. Under acidic conditions these products are further metabolized into diacetyl and acetyl methyl carbinol.
Production:
Cream separation [unhomogenised whole milk] was pasteurized at 88 – 930c, cooled at 16-210c.
Starter culture was added [Strep. lactis, Strep. cremoris – acid producers, Leuconostoc mesenteroides,
Strep. diacetylactis – flavor producers].
Churning [adding colour], Draining butter milk, Washing.
Adding salt [40-60%], Working [salt enters butter], Washing
Packing & storage at 50c.
Spoilage and defects:
Many of the defects of butter originate in the cream, from which it is made especially if the cream is held for several days. During this time lactic acid bacteria and other spoilage organisms may grow which may be followed by the growth of the molds, Geotrichum candidum.Flavor defects:
The main defects developing in butter during storage are;
1. Oxidative rancidity 2. Hydrolytic rancidity 3. Putrefactive taintsGrowth of microorganisms in cream and in the milk from which it is separated may result in any of the following bad flavors.
S.no Defects Organism involved
1
2
3
4
5
6
7
8
9
10
11
12
13
14
Acid
Barny flavor
Rancidity
Cheeseiness
Yeast
Musty
Flat
Malty
Unclean
Surface taint/rabbito/putridity
Ester like flavor
Fishiness
Metallic
Feed
Taste like cultured buttermilk due to souring of cream.
Enterobacter
Resulting from lipolytic bacteria and mold.
Lactobacillus
Flavor similar to bakers yeast results from growth of yeast in cream or butter.Produced by molds and Actinomycetes.
Lacking typical flavor Pseudomonas sp.
Produced by Streptococcus lactis
Intense old cream flavor caused by coliforms
P.putrefaciens
P. fragi
Aeromonas hydrophila
Suggestive of metal caused by metal catalyzed oxidation.
Aromatic flavor[feeds eaten by cows]
Colour defects:
1. Dark smoky discolouration àAlternaria, Cladosporium2. green colouration à Penicillium3. Brown colouration à Alternaria4. Orange/yellow spots à Geotrichum5. Dry reddish pink area à Fusarium culmorum6. Pink colonies à yeast
Chemical defects:
1.Rancidity à lipase in cream
2.Tallowiness à oxidation of unsaturated fats catalyzed by copper and bacterial enzymes and favored by low pH, T0 , salt,air, ozone.
3.Fishiness à Trimethylamine is produced from lecithin.
11.Write a brief note on Cheese Production.
CheeseIntroduction:
Cheese making is a convenient way of converting fat & protein present in milk into a nutritious
product with good keeping qualities. Microorganisms play an important role in this process to provide texture & flavor to the product. It is one of earliest method of preserving milk solids. Cheese is a compressed fermented milk product.
Classification:-
Cheese can be classified into several types based on several criteria;
a. Based on the firmness of cheese. [Moisture]b. Source of milk. [Cow, buffalo]c. Ripening. [Fungi/bacteria]d. Country of origin. [eg: cheddar à English, Roquefort à Southeast France]e. Content of fat. [Skim milk, full cream milk]f. Manufacturing process.
The basic procedure of manufacturing is same for all types of cheese. There are 4 major steps in the
Production of cheese.
1. Control of the properties of milk.2. Coagulation3. Separation of whey & curd4. Cheese ripening
I. Control of the properties of milk:-
Good quality milk is more important for cheese making because it is not possible to pasteurize
Cheese milk intensively. The bacterial content of milk used for cheese making should be low because microorganisms growing in raw milk may develop unwanted flavour & enzyme. Some organisms survive pasteurization & cause fault in cheese. The number of psychrotrophs & thermoduric organism should be low. The physical, chemical & biological properties of the milk should be controlled.
Basic stages involved in cheese making:-
*Standardization:-
Standardization of milk is done to adjust for fat or to have a balance rate of fat & casein (1: 0.7).
*clarification:-
The clarifier is an effective alternative for filtration for the removal of extraneous matter, leucocytes & Some bacteria. It is carried out at 32- 380 c Centrifugally.
Bactofugation:- If centrifuged milk is passed through the unit the 2nd time about 90% of the remaining 10% bacteria
is removed. The sludge can be sterilized & reincorporated into the milk.
Homogenization:- Milk is homogenized at low pressure the purpose is to reduce the whey exudation from the coagulum
to make cheese whiter & make promote fat hydrolysis.
Thermization:- When raw milk must be stored for a few days using for cheese it is subjected to heat treatment 630 c
for 10-15 sec & cool to 50c prior to storing.
II. Coagulation:-
It is carried out by the use of any of the following methods:-
Use of lactic acid. Addition of bacteria like lactobacillus sp. Or addition of milk clotting enzyme rennet. Application of heat. By the addition of salt. Alteration of pH.
Among these only a few methods are applicable. The commonly used method is by the adjustment
of pH.
Coagulation by pH adjustment or Ripening of milk:-
This is achieved by heating the milk at around 30-33 0 C & adding the starter bacteria. The organisms grow using lactose as an energy source & converting it into lactic acid by a complex series of reaction by involving many different enzymes. Selected strains of lactic acid organisms are used which increase the acidity.
Functions of the starter:-
Ensures consistent acid development. Aids rennet reaction & subsequent coagulation by the developed acidity. Helps expulsion of whey from the curds. Contributes to flavor & texture of cheese during ripening. Suppresses the growth of undesirable organisms.
Microorganisms used for cheese making are;
Type Function
1. Strep. lactis Acid formation
2. Strep. cremoris Acid formation
3. Strep. diacetylactis Acid, gas & flavor production.
4. Strep. thermohiles Acid production in high scald cheese.
5. L. bulgaricus Acid production.
6. Strep. faecalis Acid & flavor in high scald cheese.
7. Propionibacterium shermanii Gas & flavor production.
Starters are used at concentration ranging from 0.5 to 2% of milk. The organism multiply during cheese making from about 10 7 CFU/ml in milk to around 10 9 cfu/gm of the curd. The growth gets checked at the salting cheese stage. All additives are added & mixed separately before rennet addition. To provide uniform colour to cheese annatto colour [alkaline extract from seeds of Bixa orelana] is added to get yellow tint. Calcium chloride at 0.01 to 0.03% of the milk is used to improve the firmness of the coagulation by rennet. The addition of 15gms of salt per 100kg of cheese milk prevents blowing (development of too much of gas in the cheese) caused by coliform bacteria or butyric acid or propionic acid bacteria.
Rennetting:-
After a mild increase in acidity of milk created by starter rennet extract is added to milk & uniformly distributed to effect coagulation of milk. The coagulation enzymes are,
Type Source of Enzymes
* Animal Calf (Chymosin or pepsin )
Pig (Pepsin)
* Bacteria B. Subtilis
B. Polymyra
B. mesenteroides
* Fungi Mucor meihei
M. pusilus
Endothica parasitica.
The enzymes act in 3 phases;
1. Primary / Enzymatic phase:-
It results in the conversion of one of the milk protein from a colloidal suspension to a fibrous network. This is done in the presence of calcium.
1. Secondary/Clotting phase:- The coagulation of the other function of enzymatic activity & coagulation can be achieved by an increase
in temperature or decrease in pH.
2. Tertiary/ Proteolytic phase:- Chymosin hydrolyze the milk protein to polypeptides. A part of polypeptides are broken down to
peptides & amino acids.
III. Separation of curd & whey:-
Separation can be done by mechanical means. Whey separation depends on temperature, pH & physical characteristics of the curd. Increased temperature enhances whey separation. Whey separating is carried out by the following methods:-
By cutting the curd & allowing the whey to flow. By placing the curd in perforated containers & allowing the whey to drain through the
perforations. The curd can also be collected on a clean cloth & whey can be filtered out.
For cutting the curd, special knives are used for different sizes of cubes.
Scalding:-
High scald cheese the temperature may be 52-58 0 C, in medium scald 30-42 0 C & in low scald around 30-35 0 C. During combined action of stirring & heat, lactic acid
with the curd particle is formed by the starter organisms, embedded in cheese particles & curd cubes shrinks in size. When the desired development in the curd has reached whey is drained for texturing the curd
Draining the whey:-
The curd is allowed to settle, acidity measured, when it has reached desired level, the whey is run off until the compact mass of curd is formed in the vat.
Milling:-
It helps in uniform distribution of salt (1-2%) salt acts as a preservative & flavor enhancer.
Pressing:-
The curd is filled in moulds & pressed. The degree of pressing & length of time various with the type of cheese.
Packaging & storing:-
Packaging protects à flavor contamination
Entry to external molecules. Loss of moisture. Enhances appearance.
Wax coating /plastic film for hard cheese. Aluminium / plastic film for semi-hard cheese. Maturing period is 2-24 months. The cheese is stored in increased T 0 in fermentation
room & shifted to ripening room having lower temperature for the development of proteolysis, lipolysis, aroma & texture.
IV . Cheese ripening:-
It refers to the changes in the body to texture accompanied by the development of characteristic flavor typical to that of cheese. Flavor & aroma is produced by the action of microorganisms & enzymes which breakdown,
Carbohydrate producing lactic acid, acetic acid, Co2 & diacetyl. H2O insoluble proteins to protease, peptons, peptides, amino acids, organic acids,
NH3. Fat to lower fatty acids, their esters & Ketones.
These changes are brought about by enzymes from,
-> Lactic acid bacteria in starter culture.
-> Miscellaneous non-starter bacteria in milk.
->Rennet & its substitutions used to coagulate the milk.
->Other microorganisms growing within or surface of cheese.The cheesy flavor is mainly due to carboxyl, nitrogenous compound, fatty acids, sulphur
compounds etc.
Manufacture of Cheddar cheese.
Raw milk
Pasteurize at 71 – 750C – 15 secs [pasteurization reduces the number of spoilage organisms & lactic acid bacteria & kills most pathogens]
Cool & incubate in cheese vat at 300c [add starter culture Lactococcus lactics ssp cremoris 1 – 1.5%]
[lactic acid fermentation develops]
Milk with 0.19 to 0.21 % lactic acid [rennet added].
[curd’s formation]
Cutting of curds.
[ whey released]
Scalding 38 – 400c & stirring [acid production continues without starter culture].
Cheddaring – Squeezing & Stretching the curd [acid production continues without starter growth giving a final lactic acid concentration of 0.6 – 0.8 % - primary metabolism].
Milling and salting [ salting prevents further starter activity, assists in preservation & adds flavor & further release of whey]
Moulding & pressing [further release of whey]
Ripening
[secondary metabolism- Proteinase enzyme released from starter organism produce aminoacid , indole, sulphur compounds and phenol to enhance flavor. H2O2 and bacteriocin àto inhibit pathogen and spoilage organisms]
[moisture content]
Soft cheese Semi-soft cheese Hard cheese Very hard cheese [ Very low
[50-80 %] [39-50%] [34 – 39%] moisture].
Eg: unripenedà cottage cheese
Ripened à camembert cheese
Salt cured à feta cheese
Eg: Ripened by mouldsà Roquefort cheese
Ripened by bacteria à Brick, Gowda, Limburger
Eg: cheddar cheese SPOILAGE OF CHEESE:1.DURING MANUFACTURING:
RAW MILK:
Eg: Grana, Parmesan, Asiago old.
Off flavor is produced by gas forming organisms. Eg: Clostridium, coliforms, yeasts. Gassiness is produced by Clostridium, Bacillus polymyxa [produces gas and defects
in ripening cheese]. Bitter flavor is produced by coliforms, Micrococci, Yeasts [acid proteolytic bacteria]. Leuconostoc produces Holes/openness in cheddar cheese. Proteolysis, gas production is by undesirable microbes. Sliminess/Off flavor is produced by Pseudomonas fragi, Alcaligenes metaalcaligenes.2.DURING RIPENING:
Physical changes [hole formation, change nature of texture] Chemical changes [undesirable end product, metal discoloration] Gas holes/eyes/cracks/splitting [Clostridium-butyric acid+gas] Undesirable acid [Propionibacterium sp.] Bitterness [Streptococci] Acid + proteolytic [coliforms, Micrococci] Yeast flavor/sweet fruity flavor [yeast] Putrefaction [Clostridium tyrobutyricum, Cl.lentoputrescens, Cl.sporogenes] Discoloration ;
Eg: rusty spots à Lactobacillus plantarum, L.brewis
Yellow/pink/brownà Propionibacterium
Reddish brown to grayish brown due to oxidation of tyrosine by bacteria.
3.FINISHED CHEESE:
OOSPORA [GEOTRICHUM] Dairy mold à G.lactis Red colour àG.rubrum/G.crustacea Red spot àG.aurianticum Cheese cancer à G.caseocorans
CLADOSPORIUM [DARK/SMOKY COLOUR]
Dark green to black colour à C.herbarum
PENICILLIUM [GROWS IN CRACKS]
Green sporesàP.puberulum Yellowish brown spot à P.casei Camembert discolouration à P.aurantiovirens
12.Write a brief note on Yoghurt Production.
4.BLACK SPOT/OFF FLAVOR à Monilia sp.,/M.nigra
5. DISCOLOURATION à Aspergillus/Mucor/ Alternaria/ Scopulariopsis6.Yellow /red growth àBrevibacterium linens
Yoghurt [Bulgarian milk].
Yoghurt is the fermented milk product characterized by its viscous consistency, a strong acidulous taste due to high acidity [pH 4.6] and a distinct aroma caused mainly by acetaldehyde. Large-scale manufacture only started in the UK in the 1960s but since then yoghurt has become an increasingly important dairy product with many different varieties now available in supermarkets and other retail outlets.Spoilage:
1. Bloom cartons/frothy consistency and yeasty off flavor, odour àyeast ferments sugar into CO2
and ethanol.
2. Mould growth is less but spoils the surface of yoghurt particularly in under filled cartons.Prevention:
1. Sterilization of filling equipment.2. Careful storage of packaging.3. Installation of filtered air laminar and airflow facilities in filling rooms.4. Use of UV in filling areas.5. Periodic fumigation of filling rooms.6. Control of spillages.7. Use of sulphate in fruit.8. Heat treatment of final product.9. Use of preservative in the final product.10. Proper use of fruit and fruit syrups to prevent contamination.
Whole milk, Skim milk + water, Whole milk + cream
Pasteurization [850c – 30 mins batch process,90 - 950 c – 10minutes continuous ] inhibits Salmonella, Listeria, Camphylobacter.
Homogenize [60 – 650c] – smooth texture
Emulsifier’s addition [agar, gums, alginate to increase the viscosity]
Sweeteners addition [5% sugar inhibit lactic acid production].
Heat [90 – 950c] & cool
Inoculate with starter [Strep. salivarius ssp thermophilus, Lactobacillus delbreukii ssp bulgaricus]
Incubate [4 – 16 hrs at 30 – 450c] & Cool [ 10 – 150c]
Add fruit and flavor
Package [Maintain at chill temperature at 4.50c – 2 wks].
Recently, a different type of yoghurt has been produced that uses a mixture of;
L.acidophilus+Bifidobacterium bifidumà AB yoghurt
L.acidophilus+Bifidobacterium bifidum+S.salivarius thermophilusà ABT yoghurt
These bio or therapeutic yoghurt are said to have health promoting properties. Manufacture of this type of yoghurt involves direct vat inoculation with the starter followed by incubation at 370 c for about 16 hrs giving a final product with a pH of 4.2 to 4.4 and a milder creamier flavor.
Nutritive value of yoghurt:
During fermentation of milk the composition of minerals remain unchanged while proteins, carbohydrates, vitamins and fats to some extent are subjected to changes. The substances formed are lactic acid, alcohol, CO2 ,antibiotics and vitamins. The following processes make yoghurt
1.Proteolysis:
Proteolysis in milk takes place by exopeptidases and endopeptidases of lactic acid bacteria. So biological value increases 85.4 to 90%. This increases due to breakdown of proteins into peptides,
amino acids. The contents of essential amino acid such as leucine, isoleucine, methionine, phenyl alanine, tyrosine, tryptophan and valine increases which offers special advantage.2.Hydrolysis of lactose:
Lactose in milk is hydrolysed by metabolic activity of bacteria. Lactic acid inhibits the growth of putrifactants. It is important for organolectic properties and calcium absorption.
3.Lipolysis:
The homogenization process reduces the size of globules which become digestible, as a result of lipolytic activity the free fatty acid increases, which have some physiological effect.
4.Changes in vitamins:
There is more than 2 fold increase in vitamins of B group especially thiamine, riboflavin and nicotinamide.
5. Antibacterial activities:
The antibiotic properties are associated with Lactobacilli in yoghurt and materials responsible are lactic acid, H2O2 and lactobacilline.6.Therapeutic properties:
1. Easy absorption and better assimilation. Eg; milk [32% in 1 hr], yoghurt [91% in 1 hr].2. Improves appetite due to its pleasant refreshing and pungent taste. It is highly nourishing
invigorating.3. Gastric juice secreted by the action of yoghurt and desirable ratio of calcium and
phosphorous induced by it leads to a high digestive capacity.4. Removes excessive fat from liver and enhances bile secretion. It has therapeutic
importance in GI disturbances hepatitis, nephritis, diarrhea, colitis, anemia, and anorexia.5. It provides relief to chronic diarrhea in spruce and ulcerative colitis. Fat free yoghurt is
importance to those who suffer from heart diseases.6. Yoghurt possesses potent anti-tumour activity. Pathogenic bacteria are not able to survive
due to low pH.
13.Write a brief note on Saurkraut Production.
Fermented Vegetables Sauerkraut
The sauerkraut fermentation is an example of a microbial succession. Microbial succession involves the growth of a group or species of micro organisms in an environment, the conditions of which then change as a result of their activities so that another group or species is favoured and becomes dominant. The microbial succession involved in the fermentation of sauerkraut can pass through 3 phases.Phase 1:
1. Leuconostoc mesenteroides initiates the fermentation. The organism is heterofermentative, converting sugars in the brine into lactic acid, acetic acid, ethanol and Co2.Sugars L.mesenteroides L.A + A.A + Ethanol + Co2
2. The role of this organism in the fermentation is complex and fundamental to the production of good quality sauerkraut.
a. Rapid reduction of pH [below 4.0] within 2 days due to fermentation of lactic and acetic acids. This reduces and inhibits the bacteria other than lactic acid bacteria that may cause the cabbage to putrefy and enzymes that may cause the cabbage to soften.
b. Co2 production helps to purge O2, from the brine. This creates an anaerobic condition which is important in restricting the growth of organisms other than lactic acid bacteria. Co2 will also inhibit the growth of some G-ve bacteria and stimulate the growth of other lactic acid bacteria that form part of the fermentation flora.
c. The anaerobic conditions produced stabilize vitamin C in the cabbage so that a large percentage of the vitamin present in the raw material is retained.
d. Reducing sugars produced from the breakdown of excess sucrose in the brine can cause the product to darken by combining with amino acids present [Maillard Browning] Leuconostoc prevents this process by converting fructose to mannitol and glucose to dextran. Both are available as a carbohydrate source to other lactic acid bacteria and although the dextran produces a slime, this is only temporary.
e. Leuconostoc may produce growth factors that help to stimulate the growth of more fastidious lactic acid bacteria.
f. Leuconostoc contributes in a major way to the final flavour and aroma of the finished product.
Early in this phase [the 1st 15 hrs] there is also some growth of gram-negative organisms. These organisms, mainly coliforms, help to remove oxygen from the brine and disappear within a day or two.Phase II:
As lactic acid accumulates in the brine and the pH drops, the more acid-tolerant Lactobacillus brevis and Lactobacillus plantarum start to increase in numbers. Both organisms produce lactic acid [L.brevis is heterofermentative and L.plantarum is homofermentative] and after about 6-8 days become the dominant flora.Phase III:
After about 16-18 days the numbers of L.brevis decline and the population becomes dominated by L.plantarum. The organism continues to ferment any residual sugars to produce lactic acid and a fully stable product in which all the sugars have been fermented.
The final sauerkraut has a stable pH of 3.8 and contains 1.7 to 2.3% acid [calculated as lactic acid] with a ratio of acetic : lactic acid of about 1 : 4. Diacetyl, acetaldehyde and a number of esters have been identified in the final product, which contribute to its characteristic odour and flavour.Microbiological Problems:
1. High Temperature:
At high temperatures of 32 C and above growth of Leuconostoc mensenteroides is prevented and the population becomes dominated by Lactobacillus plantarum and pediococcus pentosaceous. Both organisms are homofermentative, their growth resulting in product that darknes readily and has a poor flavour.2. Aerobic conditions:
Aerobic conditions produced when the fermenting cabbage is not covered properly or air pockets are allowed to form when the cabbage is packed into vats, will allow the growth of yeasts and moulds. Discolourations E.g., the pink colour is due to growth of the yeast Rhodotorula, off flavours [yeasty or mouldy flavour] and softening due to pectinolytic activity of moulds are resulting defects.3. Uneven or Low salt Concentrations:
Uneven or low salt concentrations may allow putrefactive bacteria to grow, resulting in a spoiled product.Sauerkraut Defects and Spoilage:
Sauerkraut may be inferior quality because of abnormal fermentation and excessively high T inhibits the growth of Leuconostoc and consequently the flavour production. It may permit the growth of pediococcus cerevisiae and development of undesirable flavours. Low T may prevent lactic bacteria and encourages the growth of containments from soil. E.g., Enterobacter and flavobacterium. The long fermentation may favour the growth of L.brevis which yields a sharply acid flavour. Too much salt may encourage Pediococcus and Yeast. Abnormal fermentation of cabbage may result in cheese like odour caused by propionic butyric, caproic and valeric acid along with isobutyric and isovaleric acid.
1. Soft Kraut:
It may result from a faulty fermentation and from exposure to air or excessive pressing and / or tamping.2. Dark Brown / Black Kraut:
It is due to oxidation during exposure to air and is caused by combined action of plant enzyme and microorganisms destruction of acid by film yeast and molds make cardition favourable for proteolytic and pectolylic microorganisms to rot the kraut. Darkening is encouraged by uneven salting and high T. Brown colour may result from iron in hoops and tanning from barrels.3. Pink Kraut:
It is caused by red asporogenous yeast in the presence of air and high salt that has been distributed unevenly. The development of pink colour is favoured by high T, dirty vats, low acidity and iron salts.4. Ropy Krauts / Slimy Krauts:
It is caused by encapsulated varieties of L.plantarum. The sliminess may disappear on longer holding and cooking of the kraut.
Sauerkraut is subjected to spoilage at its surface, where it is exposed to air. Film yeasts and molds destroy the acidity permitting other microorganisms to grow and cause softening.
5. Salt Burn:
If salt concentration increases the surface may be darken to black. [high salt and high T]
PICKLESCucumber pickles may be prepared without fermentation or partial or complete
fermentation. They can be pasteurized to improve their keeping quality. Brined acidified cucumbers are heated so that the interior of the cucumber will be maintained at 73.9 C for atleast 15 min. Both heating and cooling should be rapid. These are 2 chief types of fermented pickles;
a. Salt or salt stock pickles b. Dill pickles.I. Preparation of Salt or Salt Stock Pickles: Immature cucumber are washed, placed in barrels or tanks and brined. Sometimes about 1% of glucose is added if the cucumbers are low in sugar. The addition of sugar will favour the production of gassy pickles or bloaters.Addition of Salt:
The rate of addition of salt and total amount added varies considerably 2 methods of salting, low salt method and high salt method.
High salt method à 50 salometer [10.5% NaCl] and final 60 salometer [15% NaCl]
Low salt method à 30 salometer [8% NaCl] and final 45 salometer The cucumbers are keyed down under a surface layer of brine and fermentation begins. In both methods salt is added at weakly intervals to increase the salometer reading by about 3 salometer up to 60. In the low salt method the increase is about 2 per week up to 50. In warm climates the salt content of brine may be increased more rapidly and cool climates a weaker brine may be added initially.1. The Traditional Fermentation:
The traditional process usually takes 6-9 weeks for completion, depending on he salting method and T employed. The number of salt tolerant sp. Of bacteria may grow initially in the newly brined fresh cucumbers. These may be marked difference in the kinds of bacteria growing in different lots, depending on the number of and kinds introduced by the cucumbers or dirt left on them and by the water of the brine, initial concentration of sodium chloride and rate of increase, and the T of the brined cucumbers. Low salt concentration will favour more kinds of bacteria, faster the acid production and greater the acidity. First to grow is Pseudomonas and Flavobacterium, types considered undesirable. Bacillus sp are likely to come on from the soils on the cucumber and their growth is undesirable. In brines of low salt content coliform bacteria, Leuconostoc mesenteroides, str. Faecatis, Pediococcus cerevisiae may grow and form acid and in 15% brines gas forming cocci may produce some acid. Later L.brevis may contribute to acidity if the salt concentration is not too high. L.plantarum developes acidity in both low and high salt brines. It becomes decreasingly active as the salt concentation increased. The total lactic acid content is 0.6 to 0.8%. Heterofermentative lactics yield pickles that are firm and have better density than homofermentative lactics.
Yeast may grow after some acid has been formed by the bacteria. Two types,
1. Film / Oxidative yeast:Which grows on the surface of the brine and destroy lactic acid by oxidation. E.g.,
Debaryomyces, Endomycopsis, Candida.The control includes daily agitation of the surface or the addition of the mineral
oil, sorbic acid or other substances. Pickle vats are located out in the sunlight which inhibits surface growth on the brine.2. Fermentative Yeast:
Which grows down in the brine and ferment sugar to alcohol and Co2. E.g., Torulopsis, Zygosaccharomyces, Hansenula. Gas produced by these yeast, bubbles from the brine and may be responsible for bloated pickles.
When the cucumber are first brined they are chalky white and opaque but during the fermentation and cure the colour changes from bright green to yellowish green and the flesh becomes increasingly translucent. The salt pickles are prepared for use in making special products such as sour, sweet sour, mixed pickles, relishes or other products.2. The controlled fermentation:
This process is designed to eliminate or minimize the defects of the traditional fermentation. First the cucumbers are washed, brined and sanitized [cl – 80 ppm] in the vat. The chlorimated brine is then acidified with glacial acetic acid. These 2 process suppers the growth of undesired bacteria. Following a purge with N2, sodium acetate is added [0.5%] to buffer the brine. This ensures effective utilization of all the fermentable carbohydrate present. After 10-24 hrs they are inoculated with special cultures of pediococcus cerevisiae and L.plantarum. During the active fermentation [10-14 days] N2 purges are repeated and additional salt is added to maintain 25 salometer.II Preparation of Dill pickles:
1. They are named because of the addition of dill herb and spices.2. They may be unfermented or fermented or made from salt stock.3. The fermentation to produce dill pickles have a lower concentration of salt and
brine is acidified with vinegar at the start. The low salt content favours and increased rate of acid production, but adds to the risk of undesirable microbial changes. The flavouring materials dill, spices, garlic etc., also act as a source of undesirable micro organisms treated spices containing low micro organisms are available 2 types of fermented dill pickles
a. Overnight b. GenuineS.No. Overnight Genuine1
23456
Slow acid fermentation [20 sal]
Weak acidified brineCured weed of dill addedLactic acid à 0.3 to 0.6%Salt concn à 5.3%Kept in cold
Org à L.mesenteroides Str.faecalis, P.cerevisiae, L.plantarumVinegar addedT 15-30 CAcid à 1-1.5%Salt concn initial à 7.5 to 8.5%Final concn à 3.4 to 4.5%
Defects and Spoilage:Fermented pickles are subjected to a number of defects most of which are caused
by bacteria.
1. Hollow Pickles:If cucumbers are allowed to stand for a while after harvesting and before
fermenting or it may be due to loose packing in vat, insufficient weighting, too rapid a fermentation and too strong or too weak a brine cause hollow pickles.2. Floaters or Bloaters:
It may result from gas being formed by yeast, L.plantarum or coliform which can produce Co2. This can be controlled by purging the brine with N2 to remove dissolved Co2. Floaters are favoured by thick skin that doesnot allow gas to diffuse out, by rapid gas production during fermentation, high initial salt by added sugar or / and acid.3. Slippery pickles:
It occurs when cucumbers are exposed to air permitting the growth of encapsulated bacteria. Slipperiness also may be due to broken scums of film yeast that have grown on the surface of the brine and dropped on to the cucumber.4. Soft Pickles:
They are made so by pectolytic enzymes mostly from molds and from cucumber flowers. These molds are mostly of the general Penicillium, Fusarium, Cladosporium, Alternaria.
Bacteria à Bacillus, Aeromonas, Coliforms.These can degrade;
Pectinase à PectinPectin Esterase à Pectinic acidPoly methyl galacturnose à Galactournoic acid
Softening is favoured by;a. An insufficient amount of salt. b. Too high a Tc. Low aciditya. Presence of air favouring the growth of film yeast or mold.b. Infusions of may blossoms.
5. Black Pickles:May owe their colour due to the formation of H2S by bacteria and combination
with iron in the water to yield black ferrous sulfide. It is also due to the growth of black pigmented Bacillus nigrificans and B.subtilis.
i.e., Iron à WaterSulphide à From Vat / H2O / CaCo3 [Gypsum]
6. Ropy Pickle Brine: Favoured by unidentified motile, Gram –ve encapsulated rods. Favoured by
i. Low saltii. Low acid
iii. High T
UNIT-5
FERMENTED DAIRY PRODUCTS:
1.Write a brief note on Kefir Production.
KEFIRIntroduction:
Kefir is the self-carbonated fermented milk product with high nutritional status and therapeutic value.
It requires a special culture called kefir grains. The grain consists of casein and gelatinous colonies of microorganisms, which live,
in symbiosis. The organism isolated is yeast such as Torula and Saccharomyces kefir and bacteria
such as L.acidophilus, Streptococcus lactis and L.kefiranofaciens. The yeast represents 5 – 10 % of the total micro flora. The grains are irregular in shape, yellowish in color and insoluble in water. Dried grains retain their activity for more than a year when stepped in milk the grains
swell. During fermentation process Lactobacillus sp. produces lactic acid and lacto
fermenting yeast cell produce alcohol and CO2. All activities are controlled by incubation temperature.
Uses:
Starter organisms produce risin, lactimine, streptocine is widely used in hospitals. It is included in diets of patients suffering from intestinal diseases, anemia,
metabolic disorders, hyper toxicity, and allergic diseases. It is beneficial for the treatment of tuberculosis. The product in diet reduces serum cholesterol level in infants.
CULTURED BUTTER MILKUses:
3) It is highly nutritious and suited as a supplement to local foods.4) Fermentation predigests several milk constituents, synthesizes water soluble
vitamin of B complex and makes a nutritionally upgraded milk.It is a fermented product made by using mesophilic starters.
Production:
Milk free from antibiotics & detergents with fat content of 0.5 – 1 % is homogenized at 150c
Heated at 900c – 13 mins & cooled to 230c.
Starter culture [Str. lactis, Str. cremoris – acid production, Str. diacetylactis, Leuconostoc citrovorum – aroma & flavor 1-2%].
Fermentation time is 16 – 20 hrs, acidity – 0.9%, mixed, cooled, bottled & stored at 50c.
Final product is viscous, drink with pleasing aroma, flavour.
2. Write a brief note on Kumiss Production.KUMISS
Prepared from mare milk, which is inoculated with starter culture of 10 – 20%. Cow milk or skimmed milk with 2.5% sucrose is used due to non-availability of mare
milk. Microflora includes Lactobacillus delbrueckeii ssp bulgaricus, L. acidophilus,
Kluveromyces lactis.Use:
Kumiss from mare milk is a good supplementary remedy for treatment of TB.BUTTER
Introduction:
Butter is a concentrate of one of the 3 main constituents of milk ie., fat, proteins, lactose. The later 2 are present only in small proportion. Butterfat also contains the yellow coloring matter carotine and or its transformation products vitamin A and D.
Composition:
Butter and moisture à 16%
Milk fat à 80%
Milk solids à 2%
Butter making process:
1.Preparation of cream, pasteurization, cooling and starter addition:
Cream is produced by mechanical separation of unhomogenized whole milk. Cream is pasteurized between 88 – 930 c. It may be subjected to vacuum cooling to ripening temperature of 16-210 c and ripened with 4% of mixed starter culture having;
1.acid producers like Streptococci lactis /S.cremoris.
2.flavor producers like L.mesenteroides, S.diacetylactics.
The ripening may be in 2/3 stages to produce soft, firm butter.
2. Churning, washing and salting:
The cream is loaded for churning in machines. The machine has 3 sections;
1.churning
2.separating
3.working sections
The churning section consists of a horizontal cylinder and a rotating variable speed rotator/beater [0-1000 rpm] since churning lasts for 1-2 sec it is important to adjust the beater velocity to obtain optimum butter grain size.
The separating section consists of a horizontal cylinder. The first part of the cylinder is equipped with beaters for further treatment mixtures of butter grains and butter milk which is fed from the churning sections.
The second part of the cylinder is designed as a sieve for draining buttermilk. It is equipped with wire gauze, which retains even small butter grains.
The working section consists of inclined sections for transport of the butter. In the production of salted butter, a salt slurry [40-60%] is pumped into the first working section, in which it is worked into the butter before butter proceeds to the second working section. Any adjustment of butter moisture also takes place in the first working section. Water dosing is done automatically.
Quality of wash water:
The chill water used for washing butter granules is an important source of contamination of butter. The treatment of butter with wash water has 2 purposes:
3. To wash away the free butter milk from the butter granules.4. To control the temperature of the granules for subsequent working process. The
following organisms are known to infect butter through wash water.[P.putrifaciens, P.fluorescens, P.fragi, P.methicica]
Packaging:
Butter is packed either in bulk or in consumer’s size containers. Normally vegetable parchment is used to line butter boxes and also a wrapper for consumer packs.
Polyethylene films replace parchment paper. Giving sodium propionate treatment can control mold growth.Flavor of butter:
The flavor of butter is produced by the fermentation of citric acid by Leuconostoc and Streptococcus lactis. Citric acid is converted into pyruvate, co2 , acetic acid. Pyruvate is again metabolized to form CO2 and acetaldehyde. Acetaldehyde under neutral and acidic conditions forms acetic acid and ethanol. Under acidic conditions these products are further metabolized into diacetyl and acetyl methyl carbinol.
Production:
Cream separation [unhomogenised whole milk] was pasteurized at 88 – 930c, cooled at 16-210c.
Starter culture was added [Strep. lactis, Strep. cremoris – acid producers, Leuconostoc mesenteroides,
Strep. diacetylactis – flavor producers].
Churning [adding colour], Draining butter milk, Washing.
Adding salt [40-60%], Working [salt enters butter], Washing
Packing & storage at 50c.
Spoilage and defects:
Many of the defects of butter originate in the cream, from which it is made especially if the cream is held for several days. During this time lactic acid bacteria and other spoilage organisms may grow which may be followed by the growth of the molds, Geotrichum candidum.Flavor defects:
The main defects developing in butter during storage are;
2. Oxidative rancidity 2. Hydrolytic rancidity 3. Putrefactive taintsGrowth of microorganisms in cream and in the milk from which it is separated may result in any of the following bad flavors.
S.no Defects Organism involved
1
2
3
4
5
6
7
8
9
10
11
12
13
14
Acid
Barny flavor
Rancidity
Cheeseiness
Yeast
Musty
Flat
Malty
Unclean
Surface taint/rabbito/putridity
Ester like flavor
Fishiness
Metallic
Feed
Taste like cultured buttermilk due to souring of cream.
Enterobacter
Resulting from lipolytic bacteria and mold.
Lactobacillus
Flavor similar to bakers yeast results from growth of yeast in cream or butter.Produced by molds and Actinomycetes.
Lacking typical flavor Pseudomonas sp.
Produced by Streptococcus lactis
Intense old cream flavor caused by coliforms
P.putrefaciens
P. fragi
Aeromonas hydrophila
Suggestive of metal caused by metal catalyzed oxidation.
Aromatic flavor[feeds eaten by cows]
Colour defects:
7. Dark smoky discolouration àAlternaria, Cladosporium8. green colouration à Penicillium9. Brown colouration à Alternaria10. Orange/yellow spots à Geotrichum11. Dry reddish pink area à Fusarium culmorum12. Pink colonies à yeast
Chemical defects:
1.Rancidity à lipase in cream
2.Tallowiness à oxidation of unsaturated fats catalyzed by copper and bacterial enzymes and favored by low pH, T0 , salt,air, ozone.
3.Fishiness à Trimethylamine is produced from lecithin.
Cheese
Introduction:
Cheese making is a convenient way of converting fat & protein present in milk into a nutritious
product with good keeping qualities. Microorganisms play an important role in this process to provide texture & flavor to the product. It is one of earliest method of preserving milk solids. Cheese is a compressed fermented milk product.
Classification:-
Cheese can be classified into several types based on several criteria;
g. Based on the firmness of cheese. [Moisture]h. Source of milk. [Cow, buffalo]i. Ripening. [Fungi/bacteria]j. Country of origin. [eg: cheddar à English, Roquefort à Southeast France]k. Content of fat. [Skim milk, full cream milk]l. Manufacturing process.
The basic procedure of manufacturing is same for all types of cheese. There are 4 major steps in the
Production of cheese.
5. Control of the properties of milk.6. Coagulation7. Separation of whey & curd8. Cheese ripening
I. Control of the properties of milk:-
Good quality milk is more important for cheese making because it is not possible to pasteurize
Cheese milk intensively. The bacterial content of milk used for cheese making should be low because microorganisms growing in raw milk may develop unwanted flavour & enzyme. Some organisms survive pasteurization & cause fault in cheese. The number of psychrotrophs & thermoduric organism should be low. The physical, chemical & biological properties of the milk should be controlled.
Basic stages involved in cheese making:-
*Standardization:-
Standardization of milk is done to adjust for fat or to have a balance rate of fat & casein (1: 0.7).
*clarification:-
The clarifier is an effective alternative for filtration for the removal of extraneous matter, leucocytes & Some bacteria. It is carried out at 32- 380 c Centrifugally.
Bactofugation:- If centrifuged milk is passed through the unit the 2nd time about 90% of the remaining 10% bacteria
is removed. The sludge can be sterilized & reincorporated into the milk.
Homogenization:- Milk is homogenized at low pressure the purpose is to reduce the whey exudation from the coagulum
to make cheese whiter & make promote fat hydrolysis.
Thermization:- When raw milk must be stored for a few days using for cheese it is subjected to heat treatment 630 c
for 10-15 sec & cool to 50c prior to storing.
II. Coagulation:-
It is carried out by the use of any of the following methods:-
Use of lactic acid. Addition of bacteria like lactobacillus sp. Or addition of milk clotting enzyme rennet. Application of heat. By the addition of salt. Alteration of pH.
Among these only a few methods are applicable. The commonly used method is by the adjustment
of pH.
Coagulation by pH adjustment or Ripening of milk:-
This is achieved by heating the milk at around 30-33 0 C & adding the starter bacteria. The organisms grow using lactose as an energy source & converting it into lactic acid by a complex series of reaction by involving many different enzymes. Selected strains of lactic acid organisms are used which increase the acidity.
Functions of the starter:-
Ensures consistent acid development. Aids rennet reaction & subsequent coagulation by the developed acidity. Helps expulsion of whey from the curds. Contributes to flavor & texture of cheese during ripening. Suppresses the growth of undesirable organisms.
Microorganisms used for cheese making are;
Type Function
1. Strep. lactis Acid formation
2. Strep. cremoris Acid formation
3. Strep. diacetylactis Acid, gas & flavor production.
4. Strep. thermohiles Acid production in high scald cheese.
5. L. bulgaricus Acid production.
6. Strep. faecalis Acid & flavor in high scald cheese.
7. Propionibacterium shermanii Gas & flavor production.
Starters are used at concentration ranging from 0.5 to 2% of milk. The organism multiply during cheese making from about 10 7 CFU/ml in milk to around 10 9 cfu/gm of the curd. The growth gets checked at the salting cheese stage. All additives are added & mixed separately before rennet addition. To provide uniform colour to cheese annatto colour [alkaline extract from seeds of Bixa orelana] is added to get yellow tint. Calcium chloride at 0.01 to 0.03% of the milk is used to improve the firmness of the coagulation by rennet. The addition of 15gms of salt per 100kg of cheese milk prevents blowing (development of too much of gas in the cheese) caused by coliform bacteria or butyric acid or propionic acid bacteria.
Rennetting:-
After a mild increase in acidity of milk created by starter rennet extract is added to milk & uniformly distributed to effect coagulation of milk. The coagulation enzymes are,
Type Source of Enzymes
* Animal Calf (Chymosin or pepsin )
Pig (Pepsin)
* Bacteria B. Subtilis
B. Polymyra
B. mesenteroides
* Fungi Mucor meihei
M. pusilus
Endothica parasitica.
The enzymes act in 3 phases;
1. Primary / Enzymatic phase:-
It results in the conversion of one of the milk protein from a colloidal suspension to a fibrous network. This is done in the presence of calcium.
3. Secondary/Clotting phase:- The coagulation of the other function of enzymatic activity & coagulation can be achieved by an increase
in temperature or decrease in pH.
4. Tertiary/ Proteolytic phase:- Chymosin hydrolyze the milk protein to polypeptides. A part of polypeptides are broken down to
peptides & amino acids.
III. Separation of curd & whey:-
Separation can be done by mechanical means. Whey separation depends on temperature, pH & physical characteristics of the curd. Increased temperature enhances whey separation. Whey separating is carried out by the following methods:-
By cutting the curd & allowing the whey to flow. By placing the curd in perforated containers & allowing the whey to drain through the
perforations. The curd can also be collected on a clean cloth & whey can be filtered out.
For cutting the curd, special knives are used for different sizes of cubes.
Scalding:-
High scald cheese the temperature may be 52-58 0 C, in medium scald 30-42 0 C & in low scald around 30-35 0 C. During combined action of stirring & heat, lactic acid with the curd particle is formed by the starter organisms, embedded in cheese particles & curd cubes shrinks in size. When the desired development in the curd has reached whey is drained for texturing the curd
Draining the whey:-
The curd is allowed to settle, acidity measured, when it has reached desired level, the whey is run off until the compact mass of curd is formed in the vat.
Milling:-
It helps in uniform distribution of salt (1-2%) salt acts as a preservative & flavor enhancer.
Pressing:-
The curd is filled in moulds & pressed. The degree of pressing & length of time various with the type of cheese.
Packaging & storing:-
Packaging protects à flavor contamination
Entry to external molecules. Loss of moisture. Enhances appearance.
Wax coating /plastic film for hard cheese. Aluminium / plastic film for semi-hard cheese. Maturing period is 2-24 months. The cheese is stored in increased T 0 in fermentation
room & shifted to ripening room having lower temperature for the development of proteolysis, lipolysis, aroma & texture.
IV . Cheese ripening:-
It refers to the changes in the body to texture accompanied by the development of characteristic flavor typical to that of cheese. Flavor & aroma is produced by the action of microorganisms & enzymes which breakdown,
Carbohydrate producing lactic acid, acetic acid, Co2 & diacetyl. H2O insoluble proteins to protease, peptons, peptides, amino acids, organic acids,
NH3. Fat to lower fatty acids, their esters & Ketones.
These changes are brought about by enzymes from,
-> Lactic acid bacteria in starter culture.
-> Miscellaneous non-starter bacteria in milk.
->Rennet & its substitutions used to coagulate the milk.
->Other microorganisms growing within or surface of cheese.The cheesy flavor is mainly due to carboxyl, nitrogenous compound, fatty acids, sulphur
compounds etc.
Manufacture of Cheddar cheese.
Raw milk
Pasteurize at 71 – 750C – 15 secs [pasteurization reduces the number of spoilage organisms & lactic acid bacteria & kills most pathogens]
Cool & incubate in cheese vat at 300c [add starter culture Lactococcus lactics ssp cremoris 1 – 1.5%]
[lactic acid fermentation develops]
Milk with 0.19 to 0.21 % lactic acid [rennet added].
[curd’s formation]
Cutting of curds.
[ whey released]
Scalding 38 – 400c & stirring [acid production continues without starter culture].
Cheddaring – Squeezing & Stretching the curd [acid production continues without starter growth giving a final lactic acid concentration of 0.6 – 0.8 % - primary metabolism].
Milling and salting [ salting prevents further starter activity, assists in preservation & adds flavor & further release of whey]
Moulding & pressing [further release of whey]
Ripening
[secondary metabolism- Proteinase enzyme released from starter organism produce aminoacid , indole, sulphur compounds and phenol to enhance flavor. H2O2 and bacteriocin àto inhibit pathogen and spoilage organisms]
[moisture content]
Soft cheese Semi-soft cheese Hard cheese Very hard cheese [ Very low
[50-80 %] [39-50%] [34 – 39%] moisture].
Eg: unripenedà cottage cheese
Ripened à camembert cheese
Salt cured à feta cheese
Eg: Ripened by mouldsà Roquefort cheese
Ripened by bacteria à Brick, Gowda, Limburger
Eg: cheddar cheese
Eg: Grana, Parmesan, Asiago old.
Off flavor is produced by gas forming organisms. Eg: Clostridium, coliforms, yeasts. Gassiness is produced by Clostridium, Bacillus polymyxa [produces gas and defects
in ripening cheese]. Bitter flavor is produced by coliforms, Micrococci, Yeasts [acid proteolytic bacteria]. Leuconostoc produces Holes/openness in cheddar cheese. Proteolysis, gas production is by undesirable microbes. Sliminess/Off flavor is produced by Pseudomonas fragi, Alcaligenes metaalcaligenes.2.DURING RIPENING:
Physical changes [hole formation, change nature of texture] Chemical changes [undesirable end product, metal discoloration] Gas holes/eyes/cracks/splitting [Clostridium-butyric acid+gas] Undesirable acid [Propionibacterium sp.]
SPOILAGE OF CHEESE:1.DURING MANUFACTURING:
RAW MILK:
Bitterness [Streptococci] Acid + proteolytic [coliforms, Micrococci] Yeast flavor/sweet fruity flavor [yeast] Putrefaction [Clostridium tyrobutyricum, Cl.lentoputrescens, Cl.sporogenes] Discoloration ;
Eg: rusty spots à Lactobacillus plantarum, L.brewis
Yellow/pink/brownà Propionibacterium
Reddish brown to grayish brown due to oxidation of tyrosine by bacteria.
3.FINISHED CHEESE:
OOSPORA [GEOTRICHUM] Dairy mold à G.lactis Red colour àG.rubrum/G.crustacea Red spot àG.aurianticum Cheese cancer à G.caseocorans
CLADOSPORIUM [DARK/SMOKY COLOUR]
Dark green to black colour à C.herbarum
PENICILLIUM [GROWS IN CRACKS]
Green sporesàP.puberulum Yellowish brown spot à P.casei Camembert discolouration à P.aurantiovirens
Yoghurt [Bulgarian milk].
Yoghurt is the fermented milk product characterized by its viscous consistency, a strong acidulous taste due to high acidity [pH 4.6] and a distinct aroma caused mainly by acetaldehyde. Large-scale manufacture only started in the UK in the 1960s but since then yoghurt has become an increasingly important dairy product with many different varieties now available in supermarkets and other retail outlets.Spoilage:
1. Bloom cartons/frothy consistency and yeasty off flavor, odour àyeast ferments sugar into CO2
and ethanol.
2. Mould growth is less but spoils the surface of yoghurt particularly in under filled cartons.Prevention:
11. Sterilization of filling equipment.12. Careful storage of packaging.13. Installation of filtered air laminar and airflow facilities in filling rooms.14. Use of UV in filling areas.15. Periodic fumigation of filling rooms.
4.BLACK SPOT/OFF FLAVOR à Monilia sp.,/M.nigra
5. DISCOLOURATION à Aspergillus/Mucor/ Alternaria/ Scopulariopsis6.Yellow /red growth àBrevibacterium linens
16. Control of spillages.17. Use of sulphate in fruit.18. Heat treatment of final product.19. Use of preservative in the final product.20. Proper use of fruit and fruit syrups to prevent contamination.
Whole milk, Skim milk + water, Whole milk + cream
Pasteurization [850c – 30 mins batch process,90 - 950 c – 10minutes continuous ] inhibits Salmonella, Listeria, Camphylobacter.
Homogenize [60 – 650c] – smooth texture
Emulsifier’s addition [agar, gums, alginate to increase the viscosity]
Sweeteners addition [5% sugar inhibit lactic acid production].
Heat [90 – 950c] & cool
Inoculate with starter [Strep. salivarius ssp thermophilus, Lactobacillus delbreukii ssp bulgaricus]
Incubate [4 – 16 hrs at 30 – 450c] & Cool [ 10 – 150c]
Add fruit and flavor
Package [Maintain at chill temperature at 4.50c – 2 wks].
Recently, a different type of yoghurt has been produced that uses a mixture of;
L.acidophilus+Bifidobacterium bifidumà AB yoghurt
L.acidophilus+Bifidobacterium bifidum+S.salivarius thermophilusà ABT yoghurt
These bio or therapeutic yoghurt are said to have health promoting properties. Manufacture of this type of yoghurt involves direct vat inoculation with the starter followed by incubation at 370 c for about 16 hrs giving a final product with a pH of 4.2 to 4.4 and a milder creamier flavor.
Nutritive value of yoghurt:
During fermentation of milk the composition of minerals remain unchanged while proteins, carbohydrates, vitamins and fats to some extent are subjected to changes. The substances formed are lactic acid, alcohol, CO2 ,antibiotics and vitamins. The following processes make yoghurt
1.Proteolysis:
Proteolysis in milk takes place by exopeptidases and endopeptidases of lactic acid bacteria. So biological value increases 85.4 to 90%. This increases due to breakdown of proteins into peptides,
amino acids. The contents of essential amino acid such as leucine, isoleucine, methionine, phenyl alanine, tyrosine, tryptophan and valine increases which offers special advantage.2.Hydrolysis of lactose:
Lactose in milk is hydrolysed by metabolic activity of bacteria. Lactic acid inhibits the growth of putrifactants. It is important for organolectic properties and calcium absorption.
3.Lipolysis:
The homogenization process reduces the size of globules which become digestible, as a result of lipolytic activity the free fatty acid increases, which have some physiological effect.
4.Changes in vitamins:
There is more than 2 fold increase in vitamins of B group especially thiamine, riboflavin and nicotinamide.
5. Antibacterial activities:
The antibiotic properties are associated with Lactobacilli in yoghurt and materials responsible are lactic acid, H2O2 and lactobacilline.6.Therapeutic properties:
7. Easy absorption and better assimilation. Eg; milk [32% in 1 hr], yoghurt [91% in 1 hr].8. Improves appetite due to its pleasant refreshing and pungent taste. It is highly nourishing
invigorating.9. Gastric juice secreted by the action of yoghurt and desirable ratio of calcium and
phosphorous induced by it leads to a high digestive capacity.10. Removes excessive fat from liver and enhances bile secretion. It has therapeutic
importance in GI disturbances hepatitis, nephritis, diarrhea, colitis, anemia, and anorexia.11. It provides relief to chronic diarrhea in spruce and ulcerative colitis. Fat free yoghurt is
importance to those who suffer from heart diseases.12. Yoghurt possesses potent anti-tumour activity. Pathogenic bacteria are not able to survive
due to low pH.
3. Write a brief note on Tarhana Production.
Tarhana:
Tarhana (Turkish), tarkhina, tarkhana, tarkhwana trachanas/trahanas (Greek τραχανάς) or (xino)chondros, трахана/тархана (Bulgarian), kishk (Egypt), or kushuk (Iraq) are dried foods based on a fermented mixture of grain and yoghurt or fermented milk, usually consumed as soup. As it is both acid and low-moisture, it preserves milk proteins effectively for long periods. Tarhana is very similar to some kinds of kishk.
The Turkish tarhana consists of cracked wheat (or flour), yoghurt, and vegetables fermented then dried. The Greek cuisine trahana contains only cracked wheat or a cous cous-like pasta and fermented milk. In Cyprus, it is considered a national specialty, and is often flavored with bay leaf, wild thyme, and fennel seed. They are cooked as soup by adding them to stock or water - or to milk (giving them similarity to breakfast cereals).Trahana may be stored as small cakes or as coarse lumps.
History
Hill and Bryer argue that tarhana is akin to τρακτον/tractum, a thickener Apicius wrote about in the first century, which most other authors consider to be a sort of cracker crumb. Dalby (1996) connects it to the described (and condemned) in Galen's Geoponica 3.8. Weaver (2002) also considers it of Western origin.
Perry, on the other hand, argues that the phonetic evolution of τραγανός to tarhana is unlikely, and that it probably comes from Persian tarkhâne. He considers the resemblance to τραγανός and to 'coarse' coincidental, though he speculates that may have influenced the word by folk etymology.
In Persian language sources the name of this food is mentioned in the form of Tarkhana by al-Zamakhshari in his dictionary, in 11th century, and in the form of Tarkhina in Jahangiri encyclopedia (named after Jahangir the Mughal emperor of India), in 13th centruy CE. Tar in Persian means wet or soaked and khan or khwan (both spelled the same and W is not pronounced) means dining place/table, or food, or large wooden bowl. Therefore, in Persian it would mean the watered or soaked food that quite matches the way the soup is made; Tarhana must be soaked in water and other possible ingredients are then added and cooked for some time.
Preparation
Tarhana is prepared by mixing flour, yoghurt or sour milk, and possibly cooked vegetables, salt, and spices (notably tarhana herb); letting the mixture ferment; then drying, grinding, and sieving the result. The fermentation produces lactic acid and other compounds giving tarhana its characteristic taste and keeping properties: the pH is lowered to 3.4-4.2, and the drying step reduces the moisture content to 6-10%, resulting in a medium inhospitable to pathogens and spoilage organisms, while preserving the milk proteins.wadays, tarhana soup is available as a convenience food in the form of dehydrated soup in packets.
4. Write a brief note on Taette Production.
Taette:
The taette is a fermented milk product and it is commonly used in scandivania. This taette is much different from kefir and kumiss. In kefir and kumiss the combination of cultures is used for the fermentation process. That is Streptococcus lactis and Lactobacillus bulgaricus and a lactose fermenting yest is inoculated. But in the taette, the yeast and rope forming strains Streptococcus lactis is inoculated in the milk. The combination of cultures is not added here.