COOKING
(Subject: Access to Library and Information System)
2 Liquids
3 Carbohydrates
4 Vitamins and minerals
5 Cooking methods
5.1 Microwave
5.2 Steam
5.3 Braise
5.4 Barbecue
5.5 Grilling
5.6 Stirfry
5.7 Roast or Bake
5.8 Broil or Stew
6 Food safety
7 Effects on nutritional content of food
8 Science of cooking
9 History of cooking
Cooking is the process of preparing food by applying heat, selecting, measuring and combining of ingredients in an ordered procedure for producing safe and edible food. The process encompasses a vast range of methods, tools and combinations of ingredients to alter the flavor, appearance, texture, or digestibility of food. 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 aesthetic, agricultural, economic, cultural, social and religious diversity throughout the nations, races, creeds and tribes across the globe.
Applying heat to food usually, though not always, chemically transforms it, thus changing its flavor, texture, consistency, appearance, and nutritional properties. Methods of cooking that involve the boiling of liquid in a receptacle have been practised at least since the 10th millennium BC, with the introduction of pottery.
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.
Cooking often involves water which is frequently 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 flavor and ingredients - this is a critical component of both stewing and sauce making.
Carbohydrates
Carbohydrates 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 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.
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.
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[1] 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. However, research led by Dr Sue Southon of the Institute of Food Research in Norwich has found that cooking vegetables facilitates the absorption of micronutrients. Cooked food may therefore provide more health benefits than raw food.
Microwave
Main article: Microwave oven
Microwaving cooks food faster than most other methods. You don't need to add fat to meat, poultry, or fish, and use little or no water with vegetables. Microwaving is an excellent way to retain vitamins and color in vegetables. When food is boiled in water and the water is subsequently discarded the water soluble vitamins and minerals are lost.
Steam
Main article: Steaming
Steaming is a good way of cooking vegetables without using fat. Try this method for frozen and fresh vegetables, such as asparagus, broccoli, carrots, spinach, and summer squash. Use a vegetable steamer or colander to hold vegetables, place in pot with a little boiling water and cover. Cook until the vegetables are just tender to preserve color and vitamins.
Braise
Main article: Braising
Braising is used mainly for meats that need longer cooking times to become tender. Root vegetables are also good braised. Brown meat first in small amount of oil or in its own fat, then simmer in a covered pan with a little liquid, try using fruit juice, cider, wine, broth, or a combination of these for added flavor
Barbecue
Main article: Barbecue
Roasting foods on a rack or a spit over coals is a way to prepare meat, poultry, fish, and vegetables too. Barbecuing gives a distinctive smoked flavor to foods. Trim fat from meat to prevent flare-up of flames and to reduce calories.
Grilling
Main article: Grilling
Grilling (Broiling, in the US) is a quick way of cooking foods under direct heat without added fat. It's great for poultry, fish, and tender cuts of meat. Use a broiling pan or rack set in a shallow pan to allow fat to drain away. If basting, use lemon juice, fruit juice, or both for flavor. Vegetables like onions, zucchini, and tomatoes can also be broiled.
Stirfry
Main article: Stirfry
Quick and easy, stirfrying requires relatively little fat and preserves the crispness and color of vegetables. Heat wok or heavy skillet, add just enough oil to cover the base of the pan, add food, and stir constantly while cooking. If using meat, start with thin strips or diced portions of meat, poultry, or fish. When meat is almost done, add small pieces of evenly cut vegetables such as onions, broccoli, cauliflower, zucchini, sprouts, carrots, green peppers, and mushrooms. Serve with a low-salt "sweet & sour" or soy sauce.
Roast or Bake
Main articles: Roast and Baking
Roasting takes somewhat longer than other methods, but requires little work on your part. Poultry and tender cuts of meat may be roasted. Cook in oven, uncovered on a rack in a shallow roasting pan to drain fat and allow heat to circulate around meat. Potatoes, sweet potatoes, winter squashes, and onions can also be baked. Simply wash, prick skins and place vegetables on a baking sheet in oven.
Broil or Stew
Main articles: Broil and Stew
Foods are cooked in hot liquids in these low-fat, low-salt methods. The liquid left after cooking can become a tasty broth, base of a sauce or served together with dish. If keeping sauce separate for future use, chill liquid first and remove any fat that rises to the top. Starchy or root vegetables such as potatoes, corn-on-the-cob, lima beans, and turnips can also be broiled.
Food safety
The effect will depend on temperature, cooking time, and technique used. The temperature range from 41°F to 135°F (5°C to 57°C) is the "food danger zone." Between these temperatures bacteria can grow rapidly. Under optimal conditions, E. coli, for example, 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 should not be left standing or in a blast chiller 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.[3] This has been debated, and some research has shown wooden boards are far better.[4] 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.
Effects on nutritional content of food
Cooking prevents many foodborne illnesses that would otherwise occur if the raw food was eaten. Cooking also increases the digestibility of some foods such as grains. Many foods are inedible raw. For example kidney beans are toxic when raw, due to the chemical phytohaemagglutinin.[5]
Proponents of Raw foodism argue that cooking food increases the risk of some of detrimental effects on food or health. They point out that the cooking of vegetables and fruit containing vitamin c both elutes the vitamin into the cooking water and degrades the vitamin through oxidation.[citation needed] Peeling vegetables can also substantially reduce the vitamin C content, especially in the case of potatoes where most vitamin C is in the skin.[citation needed] However, research has also suggested that a greater proportion of nutrients present in food is absorbed from cooked foods than from uncooked foods.[2]
Baking, grilling or broiling food, especially starchy foods, until a toasted crust is formed generates significant concentrations of acrylamide, a possible carcinogen.[citation needed]
Cooking dairy products may reduce a protective effect against colon cancer. Researchers at the University of Toronto suggest that ingesting uncooked or unpasteurized dairy products (see also Raw milk) may reduce the risk of colon cancer.[citation needed] Mice and rats fed uncooked sucrose, casein, and beef tallow had one-third to one-fifth the incidence of microadenomas as the mice and rats fed the same ingredients cooked.[6][7] This claim, however, is contentious. According to the Food and Drug Administration of the United States, health benefits claimed by raw milk advocates do not exist.[8] "The small quantities of antibodies in milk are not absorbed in the human intestinal tract," says Barbara Ingham, Ph.D., associate professor and extension food scientist at the University of Wisconsin-Madison. "There is no scientific evidence that raw milk contains an anti-arthritis factor or that it enhances resistance to other diseases."
Several studies published since 1990 indicate that cooking muscle meat creates heterocyclic amines (HCAs), which are thought to increase cancer risk in humans. Researchers at the National Cancer Institute found that human subjects who ate beef rare or medium-rare had less than one third the risk of stomach cancer than those who ate beef medium-well or well-done.[9] While eating muscle meat raw may be the only way to avoid HCAs fully, the National Cancer Institute states that cooking meat below 212 °F (100 °C) creates "negligible amounts" of HCAs. Also, microwaving meat before cooking may reduce HCAs by 90%.[10] Nitrosamines, present in processed and cooked foods, have also been noted as being carcinogenic, being linked to colon cancer.
Research has shown that grilling or barbecuing meat and fish increases levels of carcinogenic Polycyclic aromatic hydrocarbons (PAH). However, meat and fish only contribute a small proportion of dietary PAH intake - most intake comes from cereals, oils and fats.[11] German research in 2003 showed significant benefits in reducing breast cancer risk when large amounts of raw vegetable matter are included in the diet. The authors attribute some of this effect to heat-labile phytonutrients.[12]
Heating sugars with proteins or fats can produce Advanced glycation end products ("glycotoxins").[13] These have been linked to ageing and health conditions such as diabetes.
Science of cooking
The application of scientific knowledge to cooking and gastronomy has become known as molecular gastronomy. This is a subdiscipline of food science. Important contributions have been made by scientists, chefs and authors such as Herve This (chemist), Nicholas Kurti (physicist), Peter Barham (physicist), Harold McGee (author), Shirley Corriher (biochemist, author), Heston Blumenthal (chef), Ferran Adria (chef), Robert Wolke (chemist, author) and Pierre Gagnaire (chef).
Chemical processes central to cooking include the Maillard reaction - a form of non-enzymatic browning involving an amino acid, a reducing sugar, and heat.
History of cooking
There is, as yet, no clear evidence as to when cooking was invented. Richard Wrangham argues 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 as to when fire was used for cooking, as opposed to just being used for warmth or for keeping predators away. Most anthropologists contend that cooking fires began in earnest barely 250,000 years ago, when ancient hearths, earth ovens, burnt animal bones, and flint appear across Europe and the middle East. Back 2 million years ago, the only sign of fire is burnt earth with human remains, which most anthropologists consider coincidence rather than evidence of intentional fire.
