Chapter 4 The Microbiology Of Food Preservation Flashcards
What is the temperature range used for Appertization?
> 100 degree
How is Pasteurization performed? And it’s purpose.
Heat process in the range 60-80 degree and applied for up to a few minutes.
Purpose:
1.elimination of pathogen, used for milk, bulk liquid egg, ice cream mix.
2. Extend shelf-life (elimination of spoilage organisms) used for acidic products such as beers, fruit juices, pickles, and sauces.
What is “commercially sterile”?
It is another name for Appertization.
What is HTST pasterurization? How is it performed?
High Temperature Short Time pasterurization is performed at 72 degree for 15s.
What is the temperature that would kill most vegetative cells and a lot of spores?
100 degree
What is the 12D or botulinum cook?
It is a heat process applied to low-acid canned foods that should produce 12 decimal reductions in the number of surviving C. botulinum spores.
To reach the acceptable spoilage rate for canned food, how much decimal reductions should be reached? What is the indicator for process spoilage?
5-6 decimal reductions.
Clostridium sporogenes is the indicator.
How could canned foods go wrong?
- Microbial gas production
- Chemical action leads to swelling
- Microbial growth without gas production. Bacillus species, produce acid but no gas, known as “flat sour”
For the canned food, is it true that the more acidic a product is, the milder the heat process applied?
Yes.
Canned foods are classified into low acid (pH>4.5) and acid foods (pH<4.5). For low acid foods, it is insured to reach 12 decimal reductions of C. botulinum spores. While C. botulinum cannot grow in acid foods. So the heat process could be milder.
How is UHT processing performed?
Ultra High Temperature processing is performed at 130-140 degree for seconds.
Which three electromagnetic spectrum concern food microbiology?
Microwaves, the UV region and gamma rays.
What are the frequencies of microwave radiation used in food processing? What could be the problem of microwave radiation usage?
The frequencies are 2450 MHz and 915 MHz.
The non-uniform heating would lead to cold spots in some microwaved foods.
Compare micro-organisms’ resistance to UV radiation and ionizing radiation.
Resistance to UV radiation: Gram-negatives < bacterial spores < mould spores «_space;viruses
Resistance to ionizing radiation: Gram-negatives < Gram-positives ~= moulds < spores ~= yeasts < viruses.
What is the feature of UV radiation? What is its usage in the food industry? What could go wrong with UV radiation?
- The UV radiation has low penetration.
- The main use is to disinfect air and surfaces and also in the deputation(净化) of shellfish to disinfect the water recirculated through he deputation tank.
- UV could induce spoilage of products containing unsaturated fatty acids leading to rancidity. The wavelengths can cause burning of skin and eye disorders.
