Food Microbiology
Intrinsic Factors:
- Composition
- pH
- presence and availability of water
- Oxidation-Reduction Potential
– altered by cooking
- Physical Structure
- Presence of Antimicrobial Substances
Extrinsic Factors:
– lower temperatures retard microbial growth
– higher levels promote microbial growth
– oxygen promotes growth
– modified atmosphere packaging (MAP)
use of shrink wrap and vacuum technologies to package food in controlled atmospheres
Microbial Growth and Food Spoilage:
- Food Spoilage
- results from growth of microbes in food
- alters food visibly and in other ways, make it unsuitable for consumption
- involves predictable succession of microbes
- different foods undergo different types of spoilage processes
- toxins are sometimes produced
- algal toxins may contaminate shellfish and finfish
Food Spoilage:
- Approximately 1/3rd of all food manufactured in world is lost to spoilage
- Microbial content of foods (microbial load): qualitative and quantitative.
- Shelf life
- Non-perishable foods
- Semi perishable foods
- Perishable foods
General Principles:
- Minimize contamination by:
- Good management processes
- Acceptable sanitary practices
- Well-tested preservation procedures
Spoilage
- Meat
- Cutting board contamination
- Temperature
- Failure to distribute quickly
- Fecal bacteria from intestines
- Fish
- Polluted waters
- Transportation boxes
Food-Borne Diseases:
- two primary types
- food-borne infections
- food intoxications
Preventing Foodborne Disease:
- Food infections (microbes are transferred to consumer)
- Food poisoning (results from the toxin consumption)
Food-Borne Intoxications:
- ingestion of toxins in foods in which microbes have grown
- include staphylococcal food poisoning, botulism, Clostridium perfringens food poisoning, and Bacillus cereus food poisoning
Toxins:
- ergotism
- toxic condition caused by growth of a fungus in grains
- aflatoxins
- carcinogens produced in fungus-infected grains
- fumonisins
- carcinogens produced in fungus-infected corn
Detection of Food-Borne Pathogens:
- must be rapid and sensitive
- methods include:
- culture techniques – may be too slow
- immunological techniques – very sensitive
- molecular techniques
- probes used to detect specific DNA or RNA
- sensitive and specific
Helpful Suggestions:
- Refrigerate quickly
- Wash hands
- Clean cutting boards
- Avoid home-canned foods
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