Composition and Nutritional Value of Foods

Abstract

Food is a complex mixture of chemicals that an organism takes in and assimilates to promote growth, to expend energy, to replace worn or injured tissue, and to prevent some diseases. Nutrition, however, encompasses many processes, and thus it may be given many definitions. Gregor Mendel, the Austrian botanist and founder of the science of genetics, defined it as ``The Chemistry of Life.'' This definition may be the most appropriate for the food scientist because the process by which food components are assimilated, converted, and utilized are understood and properly managed only when the chemistry is understood. Most foods are extremely complex mixtures of thousands of chemicals. Proteins, carbohydrates, and lipids are organic substances that, with water, usually make up more than 97% of a food's mass. The remainder consists of thousands more compounds, which exist in small amounts measuring in concentrations of parts per million or less. These compounds are often important in the taste, odor, and color of the food. Vitamins and minerals also exist in minute amounts and are extremely important in many of the body's functions. Most food constituents contain chemically active groups that can enter into complicated series of reactions with each other or with surrounding materials such as air, water, packaging, and equipment. Heat, moisture, and concentration changes in food processing together with biological catalysts called enzymes also may induce reactions. The resulting changes in the food may be desirable or undesirable and the food scientist must be able to predict and control the changes to gain the desired effects.