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.

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 are far less likely to harbor bacteria. 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 dilute bleach (1 Tbsp/gal water), or a trip through the dishwasher, are effective methods for reducing the risk of illness due to contaminated cooking implements.

Proteins
Much edible animal material is made of proteins, including muscle, offal, and egg white. Almost all vegetable matter from vegetable based products, 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 unraveling 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 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 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 mayonnaises. 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 crystallization is driven off, then caramelization starts with the sugar undergoing thermal decomposition with the formation of carbon and other breakdown products producing caramel.