Cooking is an act of preparing food for eating. It encompasses a vast range of methods, tools and combinations of ingredients to improve the flavour or digestibility of food. It generally requires the selection, measurement and combining of ingredients in an ordered procedure in an effort to achieve the desired result. Constraints on success include the variability of ingredients, ambient conditions, tools and the skill of the individual cooking.



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

Cooking requires applying heat to a food which usually, though not always, chemically transforms it, thus changing its flavor, texture, appearance, and nutritional properties. There is archaeological evidence of cooked foodstuffs, both animal and vegetable, in human settlements dating from the earliest known use of fire. The earliest use of cooking was possibly done by Homo erectus, although the evidence is in contention among paleoanthropologists.

Effects of cooking

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 4'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.

Proteins

Much edible animal material is made of proteins, including muscle, offal, and egg white. Almost all vegetable matter also includes proteins although generally in smaller amounts. They may also be a source of essential amino acids. When proteins are heated to near boiling point 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 production of stable foams using egg whites. These are believed to be formed through the partial unravelling of the albumen protein molecules in response to beating with a whisk. 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.

Fat

Fats and oils come from both animal and plant sources. In cooking, fats provide tastes and textures but probably the most significant attribute is the wide range of cooking temperatures that can be provided by using a fat as the principal cooking medium rather than water. Commonly used fats and oils include butter, olive oil, sunflower oil, lard, beef fat - both dripping or tallow, rapeseed oil or Canola, and peanut oil. The inclusion of fats tend 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 such as hamburgers or convenience fried cereal snacks. Fats can also be blended with cereal flours to make a range of doughs and pastries. Roux made with heated fat and flour can also absorb large volumes of water-based liquids, including milk and water itself to form smooth sauces. This relies on the properties of starches to create simpler mucilaginous saccharides during cooking, which causes the familiar thickening of sauces.

Oils are commonly emulsified with water-based fluids such as vinegar or lemon juice to make mayonaises. In this the fatty content of egg yolk is used as the emulsification agent.

Carbohydrates

Carbohydrates used in cooking include a variety of sugars and starches including cereal flour, rice, arrowroot, and potato. Long chain sugars such as starch tend to break down into more simple sugars when cooked or made more acidic, such as with lemon juice or vinegar. 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.