Friday, July 22, 2011

Cooking

Cooking is the process of preparing food by use of heat. Cooking techniques and ingredients vary widely across the world, reflecting unique environmental, economic, and cultural traditions. Cooks themselves also vary widely in skill and training.
Preparing food with heat or fire is an activity unique to humans, and some scientists believe the advent of cooking played an important role in human evolution. Most anthropologists believe that cooking fires first developed around 250,000 years ago. The development of agriculture, commerce and transportation between civilizations in different regions offered cooks many new ingredients. New inventions and technologies, such as pottery for holding and boiling water, expanded cooking techniques. Some modern cooks apply advanced scientific techniques to food preparation.

History of cooking
There is no clear evidence as to when cooking was invented. Primatologist Richard Wrangham suggested that cooking was invented as far back as 1.8 million to 2.3 million years ago. Other researchers believe that cooking was invented as late as 40,000 or 10,000 years ago. Evidence of fire is inconclusive, as wildfires started by lightning-strikes are still common in East Africa and other wild areas, and it is difficult to determine when fire was first used for cooking, as opposed to just being used for warmth or for keeping predators away. Most anthropologists posit that cooking fires began a quarter million years ago.
However, some Fire-cracked rock, such as that in Central Texas (United States) are burned rock middens, or enormous piles fire-damaged rock dated to c. 3,500 years ago. These may represent the remains of earth ovens used in cooking since they contain evidence of Dasylirion wheeleri bulbs and other plants. In Great Britain similar Neolithic, Bronze Age and Iron Age features exist, but are commonly called 'burnt mounds'.


Cooking methods
There are very many methods of cooking, most of which have been known since antiquity. These include baking, roasting, frying, grilling, barbecuing, smoking, boiling, steaming and braising. A more recent innovation is microwaving. Various methods use differing levels of heat and moisture and vary in cooking time. The method chosen greatly affects the end result. Some foods are more appropriate to some methods than others.



Ingredients in cooking
Most ingredients in cooking are derived from living things. Vegetables, fruits, grains and nuts come from plants, while meat, eggs, and dairy products come from animals. Mushrooms and the yeast used in baking are kinds of fungi. Cooks also use water and minerals such as salt. Cooks can also use wine or spirits.
Naturally occurring ingredients contain various amounts of molecules called proteins, carbohydrates and fats. They also contain water and minerals. Cooking involves a manipulation of the chemical properties of these molecules.

Proteins
Edible animal material, including muscle, offal, milk, eggs and egg whites, contains 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 denatured 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.

Carbohydrates
Carbohydrates include the common sugar, sucrose (table sugar), a disaccharide, and such simple sugars as glucose (from the digestion of 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 simpler sugars when cooked, while simple sugars can form syrups. If sugars are heated so that all water of crystallisation is driven off, then caramelization 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 Maillard reaction, a basic flavor-enhancing technique.

Fats
Types of fat include vegetable oils and animal products such as butter and lard. Fats can reach temperatures higher than the boiling point of water, and are often used to conduct high heat to other ingredients, such as in frying or sautéing.

Water
Cooking often involves water, which is frequently present 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 is often 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.

Vitamins and minerals
Vitamins are materials required for normal metabolism but which the body cannot manufacture itself and which must therefore come from soil. Vitamins come from a number of sources including fresh fruit and vegetables (Vitamin C), carrots, liver (Vitamin A), cereal bran, bread, liver e ( B vitamins), fish liver oil (Vitamin D) and fresh green vegetables (Vitamin K). Many minerals are also essential in small quantities including iron, calcium, magnesium and sulphur; and in very small quantities copper, zinc and selenium. The micronutrients, minerals, and vitamins in fruit and vegetables may be destroyed or eluted by cooking. Vitamin C is especially prone to oxidation during cooking and may be completely destroyed by protracted cooking.

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