Effects of heat on food components

Effects of Heat on Food Nutrients

Food commodities are composed of protein, fats, carbohydrates and water plus trace elements like minerals, vitamins, pigments and flavor elements. It is important to understand how these elements react when heated and when mixed with each other. You must understand why foods behave as they do and then you can get them to behave, as you want them to.

PROTEINS

·         Protein is a major component of meat, fish, poultry, egg and milk. It is present in smaller amounts in nuts, beans and grain.

·         As proteins are heated, they become firm and coagulate. As the temperature increases, they shrink, become firmer and lose more moisture. Exposure of proteins to excessive heat toughens them and makes them dry. Most proteins complete coagulation at 160-185F (71-85C).

·         Connective tissues are special proteins that are present in meats. Meats with a great deal of connective are tough, but some connective tissues dissolve when cooked slowly with moisture.

·         Acids such as lemon juice, vinegar and tomato help to speed coagulation and also help dissolve some connective tissues.

CARBOHYDRATES

·         Starches and sugars are both carbohydrates. Both compounds are present in foods in many different forms. They are found in fruits, vegetables and grain plus in beans and nuts. Meats and fish contain only very small amount of carbohydrates.

·         For a chef, the two most important changes in carbohydrates caused by heat are caramelization and gelatinization.

·         Caramelization is the browning of sugars. The browning of seared meats and the golden crusts of bread loafs are forms of caramelization.

·         Gelatinization occurs when starches absorb water and swell. This is a major principle in the making of sauces and the production of bread and pastries.

·         Acids inhibit gelatinization.

FRUITS & VEGETABLE FIBER

·         Fiber is the name of a group of complex substances that give structure and firmness to plants. This fiber cannot be digested.

·         The softening of fruit and vegetables in cooking is the part breakdown of this fiber.

·         Sugar makes fiber more firm. Fruits cooked in sugar remain more firm.

·         Baking soda and other alkalis make fiber softer. Vegetables should not be cooked with baking soda because they become mushy and also lose their color and the vitamin content.

FATS

·         Fats are present in meat, fish, poultry, eggs, milk products nuts and whole grain and to a lesser extent in vegetables and fruit. Fats are also important as a cooking medium and for frying.

·         Fats could either be solid or liquid at room temperature. Liquid fats are called oils. Melting points of solid fats vary.

·         When fats are heated, they begin to breakdown. When hot enough, they deteriorate rapidly and begin to smoke. The temperature at which this happens is called the smoke point and it varies for different fats and oils.

MINERALS, VITAMINS, PIGMENTS

·         Minerals and vitamins are important to the nutritional quality of the food. Pigments are important to a food’s appearance.

·         All these components may be leached out, or dissolved away from foods during cooking.

·         Vitamins and pigments may also be destroyed by heat, by long cooking and by other elements present during cooking.

·         It is important, then, to select cooking methods that preserve, as much as possible, a food’s nutrients and appearance. These will always be a consideration when cooking techniques are involved.