GENERAL INTRODUCTION
Oils and fats play an important role in the economy of all life whether of vegetable of animal origin. For providing energy, fats and oils occupy a higher position than any other energy giving food. They in fact represent the most concentrated form in which energy can be stored in plant or animal tissues. That is why the fat or oil is found stored around the embryos in the seeds of plants, in the yolk of the egg and in the adipose tissues of animals. The deposit of fat which warm blooded animals lay down immediately beneath the skin is regarded useful in assisting to conserve body heat. 

The fats and oils contained in the tissues of plants and animals very considerably in composition not only in different animals and plants but also according to the part of the organism in which they occur. The number of fats occurring in nature is therefore very large.