ENH 222 Lecture Notes - Lecture 14: Water Activity, Aureus, Cobalt-60
16 Jul 2018
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Document Summary
Preservation of food by use of low temperatures: two methods are employed to arrest microbial growth and multiplication, these are chilling (cold storage) and freezing, chilling is keeping food at temperatures between 0-15oc. The commom chilling temperatures ranges between 4-5oc: freezing is keeping food at temperatures between 0oc and - Killing principle: in this principle, spoilage microorganisms are destroyed (killed) in the food, and the food protected against subsequent contamination by being enclosed in an air tight container. Irradiation: with either ionizing or electromagnetic radiation - e. g. gamma rays, cobalt 60 radioactive particles. Radiations kill microorganisms by destruction of dna and by creating toxic reactive compounds in a medium and in microbial cells. Use of gases: by use of ethylene oxide or ozone. The gases destroy both vegetative cells and spores. Pasteurization: is the process of heat treatment at specific temperatures and times, pasteurization is aimed at destroying all pathogenic microorganisms without affecting the nutritive value of the food.
