EFFECTS OF COOKING

PROTEINS
Edible animal material, including muscle, offal (Variety of meat), milk and egg white, contain substantial amounts of protein. Almost all vegetable matter (in particular legumes and seeds) also includes proteins, although generally in smaller amounts. These may also be a source of essential amino acids. When proteins are heated they become de-natured and change texture. In many cases, this causes the structure of the material to become softer or more friable - meat becomes cooked. In some cases, proteins can form more rigid structures, such as the coagulation of albumen in egg whites. The formation of a relatively rigid but flexible matrix from egg white provides an important component of much cake cookery, and also underpins many desserts based on meringue.
LIQUIDS
Cooking often involves water which is frequently present as in other liquids, both added in order to immerse the substances being cooked (typically water, stock or wine), and released from the foods themselves. Liquids are so important to cooking that the name of the cooking method used may be based on how the liquid is combined with the food, as in steaming, simmering, boiling, braising and blanching. Heating liquid in an open container results in rapidly increased evaporation, which concentrates the remaining flavor and ingredients - this is a critical component of both stewing and sauce making.

FATS
Fats and oils come from both animal and plant sources. In cooking, fats provide tastes and textures. When used as the principal cooking medium (rather than water), they also allow the cook access to a wide range of cooking temperatures. Common oil-cooking techniques include sautéing, stir-frying, and deep-frying. Commonly used fats and oils include butter; olive oil; vegetable oils such as sunflower oil, corn oil, and safflower oil; animal fats such as lard, schmaltz, and beef fat (both dripping and tallow); and seed oils such as rapeseed oil (Canola or mustard oil), sesame oil, soybean oil, and peanut oil. The inclusion of fats tends to add flavor to cooked food, even though the taste of the oil on its own is often unpleasant. This fact has encouraged the popularity of high fat foods, many of which are classified as junk food.
CARBOHYDRATES
Carbohydrates used in cooking include simple sugars such as glucose (from table sugar) and fructose (from fruit), and starches from sources such as cereal flour, rice, arrowroot, potato. The interaction of heat and carbohydrate is complex. Long-chain sugars such as starch tend to break down into more simple sugars when cooked, while simple sugars can form syrups. If sugars are heated so that all water of crystallization is driven off, then caramalisation starts, with the sugar undergoing thermal decomposition with the formation of carbon, and other breakdown products producing caramel. Similarly, the heating of sugars and proteins elicits the Millard reaction, a basic flavor-enhancing technique. An emulsion of starch with fat or water can, when gently heated, provide thickening to the dish being cooked. In European cooking, a mixture of butter and flour called a roux is used to thicken liquids to make stews or sauces. In Asian cooking, a similar effect is obtained from a mixture of rice or corn starch and water. These techniques rely on the properties of starches to create simpler mucilaginous saccharine during Cooking, which causes the familiar thickening of sauces. This thickening will break down, however, under additional heat.