Fats and oils are recognized as essential nutrients in both human and animal diets. Nutritionally, they are concentrated sources of energy (9 Kcal/gram); provide essential fatty acids which are the building blocks for the hormones needed to regulate bodily systems; and are a carrier for the oil soluble vitamins A, D, E, and K. They also enhance the foods we eat by providing texture and mouth feel, imparting flavor, and may contribute to the feeling of satiety after eating. Fats and oils are also important functionally in the preparation of many food products. They act as tenderizing agents, facilitate aeration, carry flavors and colors, and provide a heating medium for food preparation. Fats and oils are present naturally in many foods, such as meats, dairy products, poultry, fish, nuts, and in prepared foods, such as baked goods, margarines, dressings and sauces. To understand the nutritional and functional importance of fats and oils, it is necessary to understand their chemical composition.
Fats and oils are constructed of building blocks called “triglycerides” (also known as triacylglycerides) resulting from the combination of one unit of glycerol and three units of fatty acids. They are insoluble in water but soluble in most organic solvents. They have lower densities than water, and may have consistencies at ambient temperature of solid, semi-solid, or clear liquid. When they are solid-appearing at a normal room temperature, they are referred to as “fats,” and when they are liquid at that temperature, they are called “oils.” For simplification purposes, the terms “fat” and “oils” are used interchangeably in the remainder of this publication.
Fats and oils are classified as “lipids” which is a category that embraces a broad variety of chemical substances. In addition to triglycerides, it also includes mono- and diglycerides, phosphatides, cerebrosides, sterols, terpenes, fatty alcohols, fatty acids, fat-soluble vitamins, and other substances.
The fats and oils most frequently used in North America for food preparation and as ingredients include soybean, canola, palm, cottonseed, olive, coconut, peanut, lard, beef tallow, butterfat, sunflower, corn, palm kernel, and safflower. More detailed information on the use of some of these oils in specific products is provided in Chapter IX.