Cooking or cookery is the art, technology,
science and craft of preparing food for consumption.
Cooking techniques and ingredients vary widely
across the world, from grilling food over
an open fire to using electric stoves, to
baking in various types of ovens, reflecting
unique environmental, economic, and cultural
traditions and trends.
Types of cooking also depend on the skill
levels and training of cooks.
Cooking is done both by people in their own
dwellings and by professional cooks and chefs
in restaurants and other food establishments.
Cooking can also occur through chemical reactions
without the presence of heat, such as in ceviche,
a traditional South American dish where fish
is cooked with the acids in lemon or lime
juice.
Preparing food with heat or fire is an activity
unique to humans.
It may have started around 2 million years
ago, though archaeological evidence for it
reaches no more than 1 million years ago.The
expansion of agriculture, commerce, trade,
and transportation between civilizations in
different regions offered cooks many new ingredients.
New inventions and technologies, such as the
invention of pottery for holding and boiling
water, expanded cooking techniques.
Some modern cooks apply advanced scientific
techniques to food preparation to further
enhance the flavor of the dish served.
== History ==
Phylogenetic analysis suggests that human
ancestors may have invented cooking as far
back as 1.8 million to 2.3 million years ago.
Re-analysis of burnt bone fragments and plant
ashes from the Wonderwerk Cave in South Africa
has provided evidence supporting control of
fire by early humans by 1 million years ago.
There is evidence that Homo erectus was cooking
their food as early as 500,000 years ago.
Evidence for the controlled use of fire by
Homo erectus beginning some 400,000 years
ago has wide scholarly support.
Archaeological evidence from 300,000 years
ago, in the form of ancient hearths, earth
ovens, burnt animal bones, and flint, are
found across Europe and the Middle East.
Anthropologists think that widespread cooking
fires began about 250,000 years ago when hearths
first appeared.Recently, the earliest hearths
have been reported to be at least 790,000
years old.
Communication between the Old World and the
New World in the Columbian Exchange influenced
the history of cooking.
The movement of foods across the Atlantic
from the New World, such as potatoes, tomatoes,
maize, beans, bell pepper, chili pepper, vanilla,
pumpkin, cassava, avocado, peanut, pecan,
cashew, pineapple, blueberry, sunflower, chocolate,
gourds, and squash, had a profound effect
on Old World cooking.
The movement of foods across the Atlantic
from the Old World, such as cattle, sheep,
pigs, wheat, oats, barley, rice, apples, pears,
peas, chickpeas, green beans, mustard, and
carrots, similarly changed New World cooking.In
the seventeenth and eighteenth centuries,
food was a classic marker of identity in Europe.
In the nineteenth-century "Age of Nationalism"
cuisine became a defining symbol of national
identity.
The Industrial Revolution brought mass-production,
mass-marketing, and standardization of food.
Factories processed, preserved, canned, and
packaged a wide variety of foods, and processed
cereals quickly became a defining feature
of the American breakfast.
In the 1920s, freezing methods, cafeterias,
and fast food restaurants emerged.
Starting early in the 20th century, governments
issued nutrition guidelines that led to the
food pyramid (introduced in Sweden in 1974).
The 1916 "Food For Young Children" became
the first USDA guide to give specific dietary
guidelines.
Updated in the 1920s, these guides gave shopping
suggestions for different-sized families along
with a Depression Era revision which included
four cost levels.
In 1943, the USDA created the "Basic Seven"
chart to promote nutrition.
It included the first-ever Recommended Daily
Allowances from the National Academy of Sciences.
In 1956, the "Essentials of an Adequate Diet"
brought recommendations which cut the number
of groups that American school children would
learn about down to four.
In 1979, a guide called "Food" addressed the
link between excessive amounts of unhealthy
foods and chronic diseases.
Fats, oils, and sweets were added to the four
basic food groups.
== Ingredients ==
Most ingredients in cooking are derived from
living organisms.
Vegetables, fruits, grains and nuts as well
as herbs and spices 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 use water and minerals such as
salt.
Cooks can also use wine or spirits.
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.
=== Carbohydrates ===
Carbohydrates include the common sugar, sucrose
(table sugar), a disaccharide, and such simple
sugars as glucose (made by enzymatic splitting
of sucrose) and fructose (from fruit), and
starches from sources such as cereal flour,
rice, arrowroot and 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.
=== Fats ===
Types of fat include vegetable oils, animal
products such as butter and lard, as well
as fats from grains, including maize and flax
oils.
Fats are used in a number of ways in cooking
and baking.
To prepare stir fries, grilled cheese or pancakes,
the pan or griddle is often coated with fat
or oil.
Fats are also used as an ingredient in baked
goods such as cookies, cakes and pies.
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, deep frying or sautéing.
Fats are used to add flavor to food (e.g.,
butter or bacon fat), prevent food from sticking
to pans and create a desirable texture.
=== Proteins ===
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.
Mushrooms have high protein content.
Any of these may be sources of essential amino
acids.
When proteins are heated they become denatured
(unfolded) and change texture.
In many cases, this causes the structure of
the material to become softer or more friable
– meat becomes cooked and is more friable
and less flexible.
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 in baking cakes, and also underpins
many desserts based on meringue.
=== Water ===
Cooking often involves water, frequently present
in other liquids, which is both added in order
to immerse the substances being cooked (typically
water, stock or wine), and released from the
foods themselves.
A favorite method of adding flavor to dishes
is to save the liquid for use in other recipes.
Liquids are so important to cooking that the
name of the cooking method used is often 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 and minerals are required for normal
metabolism but which the body cannot manufacture
itself and which must therefore come from
external sources.
Vitamins come from several sources including
fresh fruit and vegetables (Vitamin C), carrots,
liver (Vitamin A), cereal bran, bread, liver
(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,
sodium chloride and sulfur; 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.
The bioavailability of some vitamins such
as thiamin, vitamin B6, niacin, folate, and
carotenoids are increased with cooking by
being freed from the food microstructure.
Blanching or steaming vegetables is a way
of minimizing vitamin and mineral loss in
cooking.
== Methods ==
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 because some foods are more appropriate
to some methods than others.
Some major hot cooking techniques include:
Roasting
Roasting – Barbecuing – Grilling/Broiling
– Rotisserie – Searing
Baking
Baking – Baking Blind – Flashbaking
Boiling
Boiling – Blanching – Braising – Coddling
– Double steaming – Infusion – Poaching
– Pressure cooking – Simmering – Smothering
– Steaming – Steeping – Stewing – Stone
boiling – Vacuum flask cooking
Frying
Fry – Deep frying – Hot salt frying – Hot
sand frying – Pan frying – Pressure frying
– Sautéing – Stir frying
Steaming
Steaming works by boiling water continuously,
causing it to vaporise into steam; the steam
then carries heat to the nearby food, thus
cooking the food.
By many it is considered a healthy form of
cooking, holding nutrients within the vegetable
or meat being cooked.
En papillote – The food is put into a pouch
and then baked, allowing its own moisture
to steam the food.
Smoking
Smoking is the process of flavoring, cooking,
or preserving food by exposing it to smoke
from burning or smoldering material, most
often wood.
== Health and safety ==
=== 
Food safety ===
Cooking can prevent many foodborne illnesses
that would otherwise occur if the food is
eaten raw.
When heat is used in the preparation of food,
it can kill or inactivate harmful organisms,
such as bacteria and viruses, as well as various
parasites such as tapeworms and Toxoplasma
gondii.
Food poisoning and other illness from uncooked
or poorly prepared food may be caused by bacteria
such as pathogenic strains of Escherichia
coli, Salmonella typhimurium and Campylobacter,
viruses such as noroviruses, and protozoa
such as Entamoeba histolytica.
Bacteria, viruses and parasites may be introduced
through salad, meat that is uncooked or done
rare, and unboiled water.The sterilizing effect
of cooking depends on temperature, cooking
time, and technique used.
Some food spoilage bacteria such as Clostridium
botulinum or Bacillus cereus can form spores
that survive boiling, which then germinate
and regrow after the food has cooled.
This makes it unsafe to reheat cooked food
more than once.Cooking increases the digestibility
of many foods which are inedible or poisonous
when raw.
For example, raw cereal grains are hard to
digest, while kidney beans are toxic when
raw or improperly cooked due to the presence
of phytohaemagglutinin, which is inactivated
by cooking for at least ten minutes at 100
°C (212 °F).Food safety depends on the safe
preparation, handling, and storage of food.
Food spoilage bacteria proliferate in the
"Danger zone" temperature range from 40 to
140 °F (4 to 60 °C), food therefore should
not be stored in this temperature range.
Washing of hands and surfaces, especially
when handling different meats, and keeping
raw food separate from cooked food to avoid
cross-contamination, are good practices in
food preparation.
Foods prepared on plastic cutting boards may
be less likely to harbor bacteria than wooden
ones.
Washing and disinfecting cutting boards, especially
after use with raw meat, poultry, or seafood,
reduces the risk of contamination.
=== 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 during cooking of vegetables
and fruit containing vitamin C, the vitamin
elutes into the cooking water and becomes
degraded 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 shown that in the specific
case of carotenoids a greater proportion is
absorbed from cooked vegetables than from
raw vegetables.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.
Sulforaphane, a glucosinolate breakdown product,
which may be found in vegetables such as broccoli,
has been shown to be protective against prostate
cancer, however, much of it is destroyed when
the vegetable is boiled.The USDA has studied
retention data for 16 vitamins, 8 minerals,
and alcohol for approximately 290 foods for
various cooking methods.
=== Carcinogens ===
In a human epidemiological analysis by Richard
Doll and Richard Peto in 1981, diet was estimated
to cause a large percentage of cancers.
Studies suggest that around 32% of cancer
deaths may be avoidable by changes to the
diet.
Some of these cancers may be caused by carcinogens
in food generated during the cooking process,
although it is often difficult to identify
the specific components in diet that serve
to increase cancer risk.
Many foods, such as beef steak and broccoli,
contain low concentrations of both carcinogens
and anticarcinogens.Several studies published
since 1990 indicate that cooking meat at high
temperature 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 avoiding meat or eating meat raw may
be the only ways to avoid HCAs in meat 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% by reducing the time needed
for the meat to be cooked at high heat.
Nitrosamines are found in some food, and may
be produced by some cooking processes from
proteins or from nitrites used as food preservatives;
cured meat such as bacon has been found to
be carcinogenic, with links to colon cancer.
Ascorbate, which is added to cured meat, however,
reduces nitrosamine formation.Research has
shown that grilling, barbecuing and smoking
meat and fish increases levels of carcinogenic
polycyclic aromatic hydrocarbons (PAH).
In Europe, grilled meat and smoked fish generally
only contribute a small proportion of dietary
PAH intake since they are a minor component
of diet – most intake comes from cereals,
oils and fats.
However, in the US, grilled/barbecued meat
is the second highest contributor of the mean
daily intake of a known PAH carcinogen benzo[a]pyrene
at 21% after ‘bread, cereal and grain’
at 29%.Baking, grilling or broiling food,
especially starchy foods, until a toasted
crust is formed generates significant concentrations
of acrylamide, a known carcinogen from animal
studies; its potential to cause cancer in
humans at normal exposures is uncertain.
Public health authorities recommend reducing
the risk by avoiding overly browning starchy
foods or meats when frying, baking, toasting
or roasting them.
=== Other health issues ===
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, PhD, 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."Heating
sugars with proteins or fats can produce advanced
glycation end products ("glycotoxins").Deep
fried food in restaurants may contain high
level of trans fat, which is known to increase
levels of low-density lipoprotein that in
turn may increase risk of heart diseases and
other conditions.
However, many fast food chains have now switched
to trans-fat-free alternatives for deep-frying.
== 
Scientific aspects ==
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.
== Home-cooking and commercial cooking ==
Home cooking has traditionally been a process
carried out informally in a home or around
a communal fire, and can be enjoyed by all
members of the family, although in many cultures
women bear primary responsibility.
Cooking is also often carried out outside
of personal quarters, for example at restaurants,
or schools.
Bakeries were one of the earliest forms of
cooking outside the home, and bakeries in
the past often offered the cooking of pots
of food provided by their customers as an
additional service.
In the present day, factory food preparation
has become common, with many "ready-to-eat"
foods being prepared and cooked in factories
and home cooks using a mixture of scratch
made, and factory made foods together to make
a meal.
The nutritional value of including more commercially
prepared foods has been found to be inferior
to home-made foods.
Home-cooked meals tend to be healthier with
fewer calories, and less saturated fat, cholesterol
and sodium on a per calorie basis while providing
more fiber, calcium, and iron.
The ingredients are also directly sourced,
so there is control over authenticity, taste,
and nutritional value.
The superior nutritional quality of home-cooking
could therefore play a role in preventing
chronic disease.
Cohort studies following the elderly over
10 years show that adults who cook their own
meals have significantly lower mortality,
even when controlling for confounding variables."Home-cooking"
may be associated with comfort food, and some
commercially produced foods and restaurant
meals are presented through advertising or
packaging as having been "home-cooked," regardless
of their actual origin.
This trend began in the 1920s and is attributed
to people in urban areas of the U.S. wanting
homestyle food even though their schedules
and smaller kitchens made cooking harder.
== See also
