canned foods. canning canning is a method of preserving food in which the food contents are...

21
CANNED FOODS

Upload: camilla-hampton

Post on 27-Dec-2015

231 views

Category:

Documents


3 download

TRANSCRIPT

Page 1: CANNED FOODS. CANNING Canning is a method of preserving food in which the food contents are processed and sealed in an airtight container.preserving food

CANNED FOODS

Page 2: CANNED FOODS. CANNING Canning is a method of preserving food in which the food contents are processed and sealed in an airtight container.preserving food

CANNING Canning is a method of preserving food in which the

food contents are processed and sealed in an airtight container.

Canning provides a typical shelf life ranging from one to five years, although under specific circumstances a freeze-dried canned product, such as canned, dried lentils, can last as long as 30 years in an edible state

To prevent the food from being spoiled a number of methods are used: pasteurisation, boiling (and other applications of high temperature over a period of time), refrigeration, freezing, drying, vacuum treatment, antimicrobial agents are used

Page 3: CANNED FOODS. CANNING Canning is a method of preserving food in which the food contents are processed and sealed in an airtight container.preserving food

SAFE CANNING METHODS

The boiling water bath method is safe for tomatoes, fruits, jams, jellies, pickles and other preserves. In this method, jars of food are heated completely covered with boiling water (212°F at sea level) and cooked for a specified amount of time

Pressure canning is the only safe method of preserving vegetables, meats, poultry and seafood.

Jars of food are placed in 2 to 3 inches of water in a special pressure cooker which is heated to a temperature of at least 240° F.

Page 4: CANNED FOODS. CANNING Canning is a method of preserving food in which the food contents are processed and sealed in an airtight container.preserving food

This temperature can only be reached using the pressure method.

A microorganism called Clostridium botulinum is the main reason why pressure processing is necessary.

Though the bacterial cells are killed at boiling temperatures, they can form spores that can withstand these temperatures.

The spores grow well in low acid foods, in the absence of air, such as in canned low acidic foods like meats and vegetables. When the spores begin to grow, they produce the deadly botulinum toxins(poisons)

Page 5: CANNED FOODS. CANNING Canning is a method of preserving food in which the food contents are processed and sealed in an airtight container.preserving food

Foods that are low acid have a pH of more than 4.6 and because of the danger of botulism, they must be prepared in a pressure canner.

The low acidic foods include: meats seafood poultry dairy products all vegetables

Page 6: CANNED FOODS. CANNING Canning is a method of preserving food in which the food contents are processed and sealed in an airtight container.preserving food

High acid foods have a pH of 4.6 or less and contain enough acid so that the Clostridium botulinum spores can not grow and produce their deadly toxin. High acidic foods can be safely canned using the boiling water bath method.

The high acidic foods include: fruits properly pickled vegetables

Page 7: CANNED FOODS. CANNING Canning is a method of preserving food in which the food contents are processed and sealed in an airtight container.preserving food

FACTORS THAT LIMIT THE SHELF LIFE OF CANNED FOODS

Cans or glass jars with metal lid can get rusted if not used properly 

Cans could even corrode, if food will chemically react with metal container. Especially highly-acid food like canned tomatoes and fruit juices gets easily corroded. 

Temperatures over 100 degrees Fahrenheit are harmful for canned foods. If the storage temperature rises, the risk of spoilage of food, jumps sharply. There are high chances of loosing nutrient of the caned food, if stored at above 75 degree for very long period

Page 8: CANNED FOODS. CANNING Canning is a method of preserving food in which the food contents are processed and sealed in an airtight container.preserving food

SPOILAGE OF CANNED FOODS

The most important kind of chemical spoilage of canned foods is hydrogen swell, resulting from the pressure of hydrogen gas released by the action of acid of a food on the iron of the can

Hydrogen swells favored by: Increase in acidities of foods Increase in tempratures of storage Imperfections in the tinning and lacquering of

the interior of the can Presence of soluble sulphurs and phosphorus

compounds

Page 9: CANNED FOODS. CANNING Canning is a method of preserving food in which the food contents are processed and sealed in an airtight container.preserving food

TYPES OF SPOILAGE OF CANNED FOODS

Three most important kinds of biological spoilage of commercially canned foods are:

flat sour spoilage TA spoilage putrefacation A fourth kind of spoilage caused by the

action of food on the iron of the can,results in hydrogen swell

Page 10: CANNED FOODS. CANNING Canning is a method of preserving food in which the food contents are processed and sealed in an airtight container.preserving food

FLAT SOUR SPOILAGE

This kind spoilage occurs when canned food remain flat during souring or by development of lactic acid in the food by the flat sour bacteria

This spoilage occurs chiefly in low acid foods such as peas and corn and is caused by species of Bacillus

Flat sour spoilage of acid foods like tomatoes or tomato juice is caused by special facultatively thermophillic species bacillus coagulans

Page 11: CANNED FOODS. CANNING Canning is a method of preserving food in which the food contents are processed and sealed in an airtight container.preserving food

Various species of bacillus that are able to form acid without gas in food may be mesophilies,facultative thermophilies or obligate thermophilies

The spores of mesophilies are less heat resistant and killed by heating process and hence are rarely concerned with flat sour spoilage

the spores of thermophilies are more heat resistant and may survive the heat process and cause flat sour spoilage

Page 12: CANNED FOODS. CANNING Canning is a method of preserving food in which the food contents are processed and sealed in an airtight container.preserving food

TA SPOILAGE

This is a thermophillic spore forming anaerobe that forms acid and gas in foods

The gas(mixture of carbon dioxide and hydrogen) swell the can if it is held long enough at a high temprature and may eventually cause bursting

The spoiled food usually has a sour odour. Sources are same as for flat sources bacteria

Page 13: CANNED FOODS. CANNING Canning is a method of preserving food in which the food contents are processed and sealed in an airtight container.preserving food

SULFIDE OR SULFUR STINKER SPOILAGE

Spoilage caused by Desulfotomaculum nigrificans

Found in low acidic foods such as peas and corn

Spores of this bacterium are less heat resistant than those of flat sour and TA bacteria

The organism is an obligate thermophile and therefore also requires poor cooling of heat processed foods or hot storage for its development

Page 14: CANNED FOODS. CANNING Canning is a method of preserving food in which the food contents are processed and sealed in an airtight container.preserving food

TYPES OF SPOILAGE BY MESOPHILIC SPORE FORMING BACTERIA

MOST SPOILAGE BY MESOPHLIC MICROORGANISMS THAT RESULTS FROM UNDERPROCESSING IS CAUSED BY SPORE FORMING BACTERIA OF THE GENERA BACILLUS AND CLOSTRIDIUM

Page 15: CANNED FOODS. CANNING Canning is a method of preserving food in which the food contents are processed and sealed in an airtight container.preserving food

SPOILAGE BY MESOPHILIC clostridium species:

Sugar fermenting species of clostridium –eg-c.butyricum and c.pasteurianum causes butyric acid fermentation in acidic foods by release of carbon dioxide and hydrogen

Other species such as C. sporogenes,C.putrefaciens,C.botulinum are proteolytic or putrefactive decomposing proteins with the production of malodorous compounds such as hydrogen sulfide,ammonia,indole and skatole

Page 16: CANNED FOODS. CANNING Canning is a method of preserving food in which the food contents are processed and sealed in an airtight container.preserving food

Putrefacative anaerobes also produce carbon dioxide and hydrogen,causing the can to swell

Canned acid foods such as pineapple,tomatoes and pears have been found spoiled by C.pasteurianum

Putrefactive anerobes grow best in the low acid –canned foods such as peas,corn,meat,fish and poultry

Page 17: CANNED FOODS. CANNING Canning is a method of preserving food in which the food contents are processed and sealed in an airtight container.preserving food

SPOILAGE BY MESOPHILLIC bacillus SPECIES:

Spores of various species of Bacillus differ considerably in their heat resistance

Spores of many of the mesophillies are killed in a short time 100 C` or less but few can survive the heat treatments employed in steam-pressure processing

Many species of Bacillus are aerobic and therefore cannot grow in a well evacuated container

Page 18: CANNED FOODS. CANNING Canning is a method of preserving food in which the food contents are processed and sealed in an airtight container.preserving food

Commercially canned foods have been spoiled by bacillus species,especially in poor evacuated cans

aerobacilli or gas forming bacillus species have been reported to cause spoilage of canned peas,asparagus,spinach,peaches and tomatoes

Page 19: CANNED FOODS. CANNING Canning is a method of preserving food in which the food contents are processed and sealed in an airtight container.preserving food

SPOILAGE BY YEAST

Canned fruits,jams ,jellies, fruit juices , syrups and sweetened condesed milk have been spoiled by fermentative yeast with swelling of the cans by carbon dioxide produced

Film yeast may grow on the surface of jellied pickled pork,repacked pickles or olives and similar products but their presence indicates contamination or lack of heat processing ,plus poor evacuation

Page 20: CANNED FOODS. CANNING Canning is a method of preserving food in which the food contents are processed and sealed in an airtight container.preserving food

SPOILAGE BY MOLDS

Molds probably are the most common cause of the spoilage of home canned foods which they enter through a leak in the seal of the container

Jams , jellies, marmalades and fruit butters permit mold growth when sugar concentration are as high as 70 % and in the acidity usually present in these products

Some molds are fairly resistant to heat,especially those forming tightly packed masses of mycelium called sclerotia.

Byssochlamys fulva a pectin fermenting mold,has ascospores that have resisted the heat processing of bottled and canned fruits and have caused spoilage

Page 21: CANNED FOODS. CANNING Canning is a method of preserving food in which the food contents are processed and sealed in an airtight container.preserving food

SPOILAGE OF CANNED MEAT AND FISH Canned fish and meat exhibits two chief types of

spoilage by: bacillus species resulting in softening and souring Clostridium species producing putrid swells Less commonly bacilli may produced acid and gas

and swells the cans Heat process given to Canned cured meats are

insufficient for sterilization therefore it may be subjected to production of carbon dioxide,nitrogen oxide or nitrogen gas from nitrate,sugars and meat or they may subjected to putrefacation with gas produced by Clostridium species

Such species ordinarily is prevented by adequate refrigeration