MICROBIAL SPOILAGE OF MEAT AND POULTRY

PRODUCTS

Presented by:- Ketaki Patil SRM university, Chennai

What is Spoilage???

• Spoilage is the process in which food

deteriorates to the point in which it is not

edible to humans or its quality of edibility

becomes reduced.

What is microbial spoilage???

• Microbes can be responsible for the spoilage of food. When they breaks down the food, acids and other waste products are created in the process. While the microbes itself may or may not be harmful, the waste products may be unpleasant to taste or may even be harmful to one's health

How it occurs???• Normal slaughtering techniques

• External sources during bleeding, handling, skinning, cutting and processing.

• Intestinal tract of animals, exterior of animals ( hide, hooves and hairs)

• Knives, cloths, air, and hands and

clothing of workers.

• Depends on methods of slaughtering methods such as mechanical,

chemical, electrical etc.

MEAT SPOILAGE

• Raw meat is subject to change by its own enzymes and microbial action and its fat may be oxidized chemically.

• Autolysis changes include some proteolytic action on muscle and connective tissue and slight hydrolysis of fats.

• The defect caused by excessive autolysis has been called “souring”

Invasion of tissue by micro organism

• Upon the death of the animal, invasion of tissue by contaminating micro organism takes place.

• Factors influence that invasion includes following:-

• The load in the gut of the animal• The physical condition of the animal immediately

before slaughter• The method of killing and bleeding• The rate of cooling

Growth of micro organism in Meat

• Meat is an ideal culture for many microbes because it is high in moisture, rich in nitrogenous foods of various degree of complexity , and plentifully supplied with minerals and accessory growth factors.

• Also, it usually has some fermentable carbohydrate( glycogen) & is at favorable pH for most micro-organism.

Factors influence growth of microorganism

• The kind & amount of contamination with microorganism and the spread of these microorganism in the meat.

• The physical properties of the meat

• Chemical properties of the meat

• Availability of oxygen

• Temperature

Types of Spoilage of Meats

• Spoilage under

1)Aerobic conditions

2)anaerobic conditions

Spoilage under Aerobic conditions

• Under aerobic conditions bacteria may cause

the following-

• Surface slime – which may be caused by

species of Pseudomonas, Acinetobacter,

Moraxella, Alcaligenes, streptococcus,

Leuconostoc, Bacillus, and Micrococcus

• It is early indication of spoilage, often observed

before expiry date.

• Changes in color of meat pigment- The red color of meat, called “bloom”, may be changed to shades of green, brown, gray as result of the production of oxidizing compound . e.g. hydrogen peroxides, hydrogen sulfide.

• Lactobacillus and Leuconostoc are basically responsible.

• Changes in fats:- The oxidation of unsaturated fats may takes place chemically in air and may be catalyzed by light and copper. e.g. oxidative rancidity

• Pseudomonas and Achromobacter are responsible for oxidative rancidity or by yeast.

• Phosphorescence – This rather uncommon defect caused by phosphorescent or luminous bacteria. E.g. Photobacterium spp. Grows on the surface of meat.

• Various surface colours due to pigmented bacteria:- red spot may be caused by Serratia marcescens or other bacteria with red pigment. Pseudomonas syncyanea can impart blue color to the surface, Micrococcus or flavobacterium imparts yellow color with yellow pigment and Chromobacterium lividum and other bacteria gives greenish blue or brownish black spot.

• Off odors and off taste:- “Taints” or undesirable odors and tastes, that appear in a meat . “ souring” is the term applied to almost any defect that gives the sour odor that may be due to volatile acids. e.g. formic, butyric,propionic acids

• “Cold storage flavor” or taint its nothing but stale flavor.

• Actinomycetes may be responsible for Musty or earthy flavor

Aerobic growth of moulds may causes

• Stickiness – surface becomes sticky• Whiskers- when meat is stored at temperatures

near freezing, a limited amount of mycelial growth may takes place without sporulation.

• Black spot- this usually caused by Cladosporium herbarum

• White spot- Sporotricum carnis mostly causes white spots.

• Green patches- this occurs due to species

Penicillum such as p.expansum

P.oxalicum

• Decomposition of fats- many molds have

lipase and hence cause hydrolysis of fats .

Spoilage under anaerobic conditions

• Facultative and anaerobic bacteria can able to grow within the meat under anaerobic conditions and cause spoilage.

• Following changes occurs in such conditions

• Souring

• Putrefacation

• Taint

• Souring – it imparts sour taste to meat due to acids such as formic, propionic, acetic etc. meat’s own enzymes are responsible for it .

• Putrefaction- true putrefaction is the anaerobic decomposition of protein with the production of foul smelling compound such as hydrogen sulfide, indole, ammonia, amines due to species Clostridium

• Taint - Taints” or undesirable odors and tastes, that appear in a meat

Various spoilage features of Meat

• Off odor-off flavours

• Discoloration

• Gas production

Off –odors & off flavours

• Off odors such as sweet and fruity, putrid, sulphury and cheesy, are characterized in aerobically stored meat.

• Species which are responsible Psuedomonas sp. & Psuedomonas fragi

• Sulphur compounds may also contribute off flavor

Discoloration

• The bacterial production of hydrogen

sulphide converts the muscle pigment to

green sulphmyoglobin.

• Hydrogen sulphide is produced from

cystein and is triggered by glucose

limitation L.sake forms hydrogen sulphide.

Gas production

• Clostridium spp. have been associated

with the production of large amount of gas

in vacuum packaged beef , accompanied

by foul off-odors. Gas production (co2) by

lactic acid bacteria without extensive off

odors may be associated with vacuum

packaged beef and pork.

organism Responsible for changes

Psuedomonas species Off odor and off flavor

Microbacterium thermosphactum Spoilage in processed meat

Achromobacter species Spoilage in processed meat

Lactobacter species Spoilage of vacuum packaged cuts or ground meat

Moulds species like Cladosporium Spoilage of beef sides or quarters during prolong storage at 0°c.

Cured meat type Spoilage organism

Sliced ham and bacon Souring due to Streptococcus faecium, & Microbacterium thermosphactum

Pasteurized canned product Bacillus sps., clostridium sps.,enterococci, streptococci and heat resistance lactic acid bacteria

Refrigerated canned product Streptococcus sps.

Type of sausage Type of spoilage Organism responsible

Fresh uncooked sausage Putrefaction souring Achromobacter and Psuedomonas & Microbacterium thermosphactum,

Cooked sausages Irregular green spots on surface, green cores Narrow green rings within the product

Lactobacteriaceae, Leuconostoc, streptococci and pediococci

Cooked sausages sliming Yeast , Microbacterium thermosphactum

References

• Willam C. Frazier Food microbiology

• Principles Of Meat Technology by V.P Singh

• Food microbiology by K. Vijaya Ramesh