Three types of food decay
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Biological decomposition of organic matter, with the production of ill-smelling and tasting products, associated with anaerobic (no oxygen present) conditions.
Formula of putrefaction:
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Fermentation , chemical changes in organic substances produced by the action of enzymes. This general definition includes virtually all chemical reactions of physiological importance, and scientists today often restrict the term to the action of specific enzymes, called ferments, produced by minute organisms such as molds, bacteria, and yeasts. For example, lactase, a ferment produced by bacteria usually found in milk, causes the milk to sour by changing lactose (milk sugar) into lactic acid.
Formula of fermentation:
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(1)Microbial rancidity
Like all food components, fats undergo deteriorative changes with time, which result in undesirable flavors and odors. These changes in fats are given the term "rancidity".
Formula of microbial rancidity:
(2)Hydrolytic rancidity
Fatty acids formed through hydrolysis of the lipid(fat) by the water which it contains. Some of the liberated fatty acids are volatile, and some have very unpleasant odours and flavours.
Formula of hydrolytic rancidity
(3)Oxidative rancidity
The oxidation of acylglycerols which occurs in air, without the presence of enzymes, is called autoxidation. Among the products of autoxidation are hydroperoxides, ROOH. These have no taste, but they decompose easily to form aldehydes, ketones and acids, which give oxidised fats and oils their rancid flavours.
It can be slow down by addition of antioxidants.
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