Microbial spoilage of meat, fish and sea.pptx

micobiolpgy

1. Microbial spoilage of meat, fish and sea foods.

2. General types of Microbial  Spoilage of meat Common type of microbial spoilage of meat can be classified on the basis of whether they occur under aerobic or anaerobic condition and whether they are caused by bacteria, yeast, or mold.

3. Spoilage of meat under aerobic conditions: Bacterial spoilage of meat : Surface spoilage: It is caused by  Pseudomonas, Streptococcus, Bacillus  and  Micrococcus. Temperature and available moisture influence type of microorganisms causing slime. Change in color of meat : Red color of meat may be changed into green brown or grey due to production of oxidising agent, H 2 S, etc. by microorganisms. For example,  Lactobacillus  and  Leuconostoc   cause greening of sausage

4. Spoilage of meat under aerobic conditions Change in fat: Fat of meat may become rancid due to lipase producing microorganisms such as  Pseudomonas  and  Achromobacter . Surface color due to pigmented bacteria: Pseudomonas   give blue color,  Chromobacterium gives greenish blue to brownish black color,  Flavobacterium   give yellow color. Off odors and off taste : Undesirable odor and taste called taint are caused by many bacteria due to production of volatile acids such as formic acid, acetic acid, butyric acid etc. Actinomycetes give musty or earthy flavor

5. Spoilage of meat under aerobic conditions Fungal spoilage of meat : (molds) Stickness :  Many molds grow on surface of meat and make it sticky to touch. Whiskers: when meat is kept at temperature near freezing, mold grow slowly without sporulation on surface producing while cottony growth . Black spot : It is caused by  Cladosporium White spot : It is caused by  Sporotrichum carnis . Green spot:  It is caused by  Penicillium   species. Change in fat : Many molds produce lipase and cause hydrolytic rancidity of fat. Off odor and off taste: Many molds give musty flavor to meat in the vicinity of their growth.

6. Spoilage of meat under aerobic conditions By yeast: Under aerobic condition, yeast grow on surface of meat causing sliminess, rancidity of fat, off odor and taste and discolorations like white, pink, brown spots.

7. Spoilage of meat under anaerobic conditions

8. Poultry Meat Poultry meat like meat of other animals is also susceptible to contamination by various sources . Contamination of skin and lining of the body cavity take place during various processing operations. The organisms of great importance in poultry are Salmonella spp. and Campylobacter jejuni Freezing further reduces the number of microorganisms in the poultry meat provided the temperature is maintained quite low (-18°C or below).

9. Composition of a fish • Water 65 – 80 % • Fat 1 – 20 % • Protein 14 – 20 % Fish Spoilage due to Microbial Action Microbial action involves chiefly bacterial spoilage of the fish flesh. A large number of bacteria present on the body, gills and gut of the fish find a good medium for development due to high moisture (75-80%) contents in the fish flesh.

10. proteiolytic microbes such as Pseudomonas , Chromobacterium , Halobacterium , Micrococcus, etc. • The carbohydrates present in small amount in the fish flesh are degraded by carbohydrate fermenting microbes like Streptococcus, Leuconostoc , Micrococcus, etc . • Fat contents of the fish flesh are decomposed by relatively few gram negative bacteria.