Cooking is the process of preparing food with
heat. Cooks select and combine ingredients using a wide range of
tools and methods. In the process, the flavor, texture,
appearance, and chemical properties of the ingredients can change.
Cooking techniques and ingredients vary widely across the world,
reflecting unique environmental, economic, and cultural
traditions. Cooks themselves also vary widely in skill and
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 stated 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 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. The
only evidence of human use of fire more than two million years ago
is burnt earth with human remains, which most anthropologists
consider coincidence rather than evidence of intentional fire.
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'.
Ingredients in cooking
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 utilize water and minerals
such as salt. Cooks can also use wine, an alcohol-based liquid
from the fermentation of juices of grapes or other fruits.
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.
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 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
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 crystallization
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
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.
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.
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.
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.
Methods of cooking
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. Some major hot cooking techniques include:
Roasting - Barbecuing - Grilling - Rotisserie -
Baking - Baking Blind - Broiling -
Boiling - Blanching -
Coddling - Double steaming - Infusion - Poaching - Pressure
cooking - Simmering - Steaming - Steeping - Stewing - Vacuum flask
Frying - Deep frying - Hot salt frying - Hot
sand frying - Pan frying - Pressure frying - Sautéing - Stir
Main article: Food safety
When heat is used in the preparation
of food, it 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 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. This has been debated, and some research
has 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.
Effects on nutritional content of food
Proponents of Raw foodism argue that
cooking food increases the risk of some of the 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. Peeling
vegetables can also substantially reduce the vitamin C content,
especially in the case of potatoes where most vitamin C is in the
skin. However, research has also suggested that a greater
proportion of nutrients present in food is absorbed from cooked
foods than from uncooked foods.
Baking, grilling or broiling food, especially
starchy foods, until a toasted crust is formed generates
significant concentrations of acrylamide, a possible carcinogen.
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 colorectal
cancer. 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. 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. "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. 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%.
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. 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.
Heating sugars with proteins or fats can
produce Advanced glycation end products ("glycotoxins"). These
have been linked to ageing and health conditions such as diabetes.
Science of cooking
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.
Home-cooking vs. factory cooking
Although cooking has traditionally been a process carried out
informally at home or around a communal fire, cooking is often,
and increasingly, carried out outside the home. Bakeries were an
early form of cooking outside the home, and bakeries in the past
often offered the cooking of foods provided by their customers as
an additional service. In the present day, factory food
preparation is rapidly becoming the norm, with many "ready-to-eat"
foods being prepared and cooked in factories.
"Home-cooking" may be associated with comfort
food, and some commercially produced foods are presented as having
been "home-cooked", regardless of their actual origin.