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