Cooking
 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 training.
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.
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 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.
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'.
Most 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.
Proteins
Major Article: Protein
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
Main article: Carbohydrates
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
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 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
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
Main
article: Fat
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.
Water
Main article: Water
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
Main articles: 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.
See also
Cooking techniques
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
Roasting - Barbecuing - Grilling - Rotisserie - Searing
Baking
Baking - Baking
Blind - Broiling - Flashbaking
Boiling
Boiling - Blanching - Braising - Coddling
- Double steaming - Infusion - Poaching - Pressure cooking -
Simmering - Steaming - Steeping - Stewing - Vacuum flask cooking
Frying
Frying - Deep
frying - Hot salt frying - Hot sand frying - Pan frying - Pressure
frying - Sautéing - Stir frying
Smoking
Food smoking
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.
See also: Raw foodism
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 un-pasteurized 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-degrees F. (100-degrees 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.
The application of scientific knowledge to
cooking and gastronomy has become known as molecular gastronomy.
This is a sub discipline 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.
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.
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