Cooking is the act of preparing food for eating by the application of heat. It encompasses a vast range of methods, tools and combinations of ingredients to alter the flavor or digestibility of food. It is the process of selecting, measuring and combining of ingredients in an ordered procedure in an effort to achieve the desired result. Factors affecting the final outcome include the variability of ingredients, ambient conditions, tools, and the skill of the individual doing the actual cooking.

The diversity of cooking worldwide is a reflection of the myriad nutritional, aesthetic, agricultural, economic, cultural and religious considerations that impact upon it.

Applying heat to a food usually, though not always, chemically transforms it, thus changing its flavor, texture, appearance, and nutritional properties. There is archaeological evidence of roasted foodstuffs, both animal and vegetable, in human (''Homo erectus'') campsites dating from the earliest known use of fire, some 800,000 years ago. Other methods of cooking that involve the boiling of liquid in a receptacle have been practiced at least since the 10th millennium BC, with the introduction of pottery.

Proteins

Edible animal material, including muscle, offal, milk and egg white, 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 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 often present as 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 flavors and ingredients - this is a critical component of both stewing and sauce making.

Fat

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 sauteing, stir-frying, and deep-frying. Commonly used fats and oils include butter, olive oil, sunflower oil, lard, beef fat (both dripping and tallow), rapeseed oil or Canola, and peanut oil. The inclusion of fats tends to add flavour 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 crystallisation is driven off, then caramelisation 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.

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 saccharides during cooking, which causes the familiar thickening of sauces. This thickening will break down, however, under additional heat.

Food safety

If heat is used in the preparation of food, this can kill or inactivate potentially harmful organisms including bacteria and viruses. The effect will depend on temperature, cooking time, and technique used. The temperature range from 5°C to 57°C (41°F to 135°F) is the "food danger zone." Between these temperatures bacteria can grow rapidly. Under the correct conditions bacteria can double in number every twenty minutes. The food may not appear any different or spoiled but can be harmful to anyone who eats it. Meat, poultry, dairy products, and other prepared food must be kept outside of the "food danger zone" to remain safe to eat. Refrigeration and freezing do not kill bacteria, but only slow their growth. When cooling hot food, it shouldn't be left on the side or in a blast chiller (an appliance used to quickly cool food) for more than 90 minutes.

Cutting boards are a potential breeding ground for bacteria, and can be quite hazardous unless safety precautions are taken. Plastic cutting boards are less porous than wood and have conventionally been assumed to be far less likely to harbor bacteria. This has been debated, and some research have shown wooden boards are far better. Washing and sanitizing cutting boards is highly recommended, especially after use with raw meat, poultry, or seafood. Hot water and soap followed by a rinse with an antibacterial cleaner (dilute bleach is common in a mixture of 1 tablespoon per gallon of water, as at that dilution it is considered food safe, though some professionals choose not to use this method because they believe it could taint some foods), or a trip through a dishwasher with a "sanitize" cycle, are effective methods for reducing the risk of illness due to contaminated cooking implements.

It is also important to be very careful when using knives. The most important part of knife safety is to make sure your knife is sharp. It is easier to be cut with a dull knife, because more pressure must be applied to make a cut. Also, passing knives to a co-worker can become dangerous. When passing a knife to any other person in the kitchen, place the knife down on a flat, sanitized surface, and let the other person pick it up by the handle. This is the safest way to pass a knife to another person. The last knife hazard is for the person washing dishes. When finished with a knife, it is important that the dishwasher is aware that a knife is there. If the knife is placed in soapy water, it could be potentially dangerous, because someone unaware of the knife could reach in, and get cut. Always make sure the dishwasher knows about sharp objects, or, if possible, wash, dry, and store the knife by yourself. By following these rules, knife hazards will be limited, and you wil be more safe in the kitchen.

The culinary triangle

The ''culinary triangle'' is a concept thought up by Claude Lévi-Strauss involving three types of cooking; these are boiling, roasting, and smoking, usually done to meats.Lévi-Strauss, Claude. "The Culinary Triangle." In ''Food and Culture: A Reader.'' ed. Counihan, Carole and Van Esterik, Penny. Routledge. 1997

The boiling of meat is looked at as a cultural way of cooking because it uses a receptacle to hold water, therefore it is not completely natural. It is also the most preferred way to cook due to the fact that neither any of the meat or its juices are lost. In most cultures, this form of cooking is most represented by women and is served domestically to small closed groups, such as families. Roasting of meat is a natural way of cooking because it uses no receptacle. It is done by directly exposing the meat to the fire. It is most commonly offered to guests and is associated with men in many cultures. As opposed to boiling, meat can lose some parts, thus it is also associated with destruction and loss. Smoking meat is also a natural way of cooking. It is also done without a receptacle and in the same way as roasting. It is a slower method of roasting, however, which makes it somewhat like boiling.