micro ch. 13

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micro ch. 13
2011-02-23 22:44:05

exam 2
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  1. 1/3 of all food manufactured is.. .
    lost to spoilage
  2. microbial content of foods have...
    • qualitative - which microbes present
    • quantitative - how many of them present
  3. microbial load
    microbial content of particular food
  4. nonperishable foods
    • eg. potato chips and pasta products
    • -low numbers of microbe and long shelf lives
  5. semiperishable foods
    • eg. breads and citrust fruits
    • -contain more moisture and higher numbers of microbes will develop
  6. perishable foods
    • eg. fish and eggs
    • -present most favorable conditions for microbial growth and eventually contain highest numbers of microbes
    • -shortest shelf life
  7. conditions for spoilage
    water, pH (slightly acidic), physical structure, oxygen and temperature,
  8. choke points
    places where animals come together
  9. two types of grain spoilage:
    • 1. caused by ascomycete Aspergillus flavus
    • 2. caused by Claviceps purpurea
  10. Aspergillus flavus
    • produces aflatoxins, accumulate in stored grains
    • -fungus implicated in liver and colon cancers in humans
  11. Claviceps purpurea
    cause of ergot poisoning (ergotism), manifest in neurological symptoms, trigger convulsions and hallucinations when consumed
  12. food preservation methods
    heat, pasteurization, low temperatures, drying, osmotic pressure, chemical preservatives, and radiation
  13. heat kills microorganisms by
    changing physical and chemical properties of their proteins
  14. canning
    • most useful application of heat in food technology
    • -Bryan Donkin replaced iron cans coated with tin
  15. commercial sterilization
    sterilizing process designed to eliminate mose resistant bacterial spores, not as rigorous as true sterilizing for medical instruments
  16. pasteurization
    • -by Louis Pasteur
    • -to eliminate bacteria in wines
    • -lowers total number of bacteria & reduces change of spoilage
  17. holding method
    • more traditional method of pasteurization
    • -involves heating milk in large bulk tanks at 62.8 degree C for 30 mins
  18. flash method
    • moderm method of pasteurization
    • -machines pass milk thru hot cylinder at 71.7˚C for a period of 15 - 17 seconds
    • -milk then cooled rapidly
  19. ultrapasteurization
    • newer method, used in some dairy plants
    • -milk and milk products are subjected to heat at 82.2˚C for 3 seconds
  20. thermoduric
  21. thermophilic
  22. lower temperatuer
    • reduces rate of enzyme activity in micrboes and slows rate of growth and reproduction
    • -extends shelf life
  23. lypohilization
    • freeze-drying,
    • food is deep frozen, vacuum pump draws off water
  24. osmosis
    • flow of water
    • -force that drives the water is termed osmotic pressure
  25. chemical preservative
    must be inhibitory to microves while easily broken down and eliminated by body without side effects.