Explain Deteriorative changes in fats and oils

The food products undergo changes in flavour due to the chemical changes occurring in fats and oils present in them. The causative factors responsible for such changes are presence of enzymes, atmospheric oxygen and application of high temperature. Lipid oxidation is one of the major causes of food spoilage. It is of great economic concern  to the food industry because it leads to the development of various off-flavours and off odours generally called 'rancid' (oxidative rancidity), in edible oils and fat-containing foods, which render these foods less acceptable. In addition, oxidative reactions can decrease the nutritional quality of food and certain oxidation products are potentially toxic. On the other hand, under certain conditions, a limited degree of lipid oxidation is sometimes desirable, as in aged cheeses and in some fried foods