The fats make up one of the three classes of organic matter that are the main building materials of living organisms. Probably every living thing contains protein, carbohydrate, and fat, although in some the proportion of fat may be very small.
How fat is synthesized, and just what its function is in living plants, do not appear to be known with any certainty, but its vital importance is evident from its presence in every cell, its concentration in reproductive organs such as pollen grains and seeds, and its intimate association with other substance known to influence life processes, such as the fat-soluble vitamins, sterols, and phospholipids.
To mankind, vegetable fats are important first as food. They are concentrated food materials having more than twice the net heat value of the same weight of carbohydrates or proteins.
In addition, they serve as carriers of fat-soluble vitamins and they furnish the essential fatty acid without which the animal organism cannot thrive.
Besides their direct nutritional value, they have the virtue of making other foods more appetizing. They are indispensable in practical cooking and baking since much food cannot be making fit to eat without fat.
The Proportion of Vegetable Fat
The proportion of fat in natural foodstuffs varies greatly. In white potatoes the lipid content is about 0.5 percent of the dry weight; in English walnuts, it is about 69 percent. Much of the fat consumed by man is taken with the natural foodstuffs without ever having been separated from the other plant material in which occurs.
The most important part of fat technology, therefore, consists in the isolation of fats. The refining and processing needed to make them palatable and suited to various culinary requirements. The nonfood uses, on the other hand, have long been important ones and are becoming relatively more so.
Especially, the expanding uses of fats as chemical raw materials for the synthesis of a great variety of improved and new products has been a feature of the chemical developments of recent years.