Home > 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:

• temperature

– lower temperatures retard microbial growth

• relative humidity

– higher levels promote microbial growth

• atmosphere

– 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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