Fats are a class of energy-rich organic compounds occurring widely in organic tissue, especially in the adipose tissue of animals and in the seeds, nuts, and fruits of plants. Fat differ from oil in that they are solid or semisolid at room temperature, while oils are liquid.

Plant oils made largely from cottonseed, soybean and peanut oils are not completely hydrogenated, because hydrogenation (process of turning liquid vegetable oils to solid margarine or lard), when carried out in its totality, produces only saturated fatty acids; and a totally saturated oil has the consistency of a wax and is not appropriate for use in food except in very small amounts added with emulsifiers to food products. Margarine, the most common of the fats made from plant oils, contains about 80% vegetable fat, about 15% skim milk, and emulsifying vitamins, and dye.

a. Edible plant oils: cottonseed, soybean, peanut, corn, olive, coconut, and safflower oils.

Three Types of Edible Fats:

• Saturated - these fats are commonly solid at room temperature. These saturated fats (fully saturated with hydrogen atoms) raise cholesterol and are a primary contributor to heart disease. Butter, lard and most animal fats are examples.
• Monounsaturated and Polyunsaturated - they are usually liquid at room temperature. There are claims that some unsaturated oils will help reduce cholesterol or other fatty deposits in blood vessels and are often eaten to reduce the danger of coronary thrombosis or atherosclerosis, but they actually have little beneficial effect unless they are used as a substitute for saturated fats. Almond, olive, peanut, cottonseed, safflower, sesame, soybean and sunflower are rich sources of this fat.

b. Inedible plant oils: linseed, palm, rape, castor, tung, tall (a by-product of pinewood paper industries), and oiticica oils.

Methods of Plant oils extraction:

• Cold pressing is usually used for first quality food products because few objectionable impurities pass into the oil.
• Hot pressing and Solvent Extraction is usually done after the cold pressing to obtain maximum yield of oil. The lower grades of such oils is may be used as soap stock. Improvements in solvent extraction methods have made their increased use for food products possible. The press cake from the extraction of soybean, cottonseed, rape, and coconut oils is used as cattle feed.