Cooking
From Wikipedia, the free encyclopedia
Cooking is the art or practice of preparing food with the use of heat for consumption. 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. Cooking can also occur through chemical reactions without the
presence of heat, most notably as in Ceviche, a traditional South American dish
where fish is cooked with the acids in lemon or lime juice. Sushi also utilizes
a similar chemical reaction between fish and the acidic content of rice glazed
with vinegar.
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History
There is no clear archaeological
evidence when food was first cooked. Most anthropologists
believe that cooking fires began only about 250,000 years ago, when hearths started appearing.[3]
Phylogenetic
analysis by Chris Organ, Charles Nunn, Zarin Machanda, and Richard Wrangham
suggests that cooking may have been invented as far back as 1.8 million to 2.3
million years ago.[4]
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.
Wrangham proposed cooking was
instrumental in human evolution, as it reduced the time required for foraging
and led to an increase in brain size. Since meat has a higher energy density
than vegetables, and cooking it allows more nutrients to be liberated to the
body, the introduction of cooked meat in the human diet reduced the energy
requirements of the digestive system. He estimates the percentage decrease in
gut size of early humans directly correlates to the increase in brain size.[5]
Most other anthropologists, however, oppose Wrangham,[6]
stating that archeological evidence suggests that cooking fires began in earnest
only c.250,000 years ago, when ancient hearths, earth ovens, burnt animal
bones, and flint appear across Europe and the Middle East. Two million years
ago, the only sign of fire is burnt earth with human remains, which most other
anthropologists consider to be mere coincidence rather than evidence of
intentional fire.[7]
The mainstream view among anthropologists is that the increases in human
brain-size occurred well before the advent of cooking, due to a shift away from
the consumption of nuts and berries to the consumption of meat.[8][9]
Food has become a part of material
culture, and cuisine is much more than a substance. In the seventeenth and
eighteenth centuries, food was a classic marker in Europe. However, in the
nineteenth century, cuisine became a defining symbol of national identity. The
discovery of the New World represented a major turning point in the history of
food because of the movement of foods from and to Europe, such as potatoes,
tomatoes, corn, yams, and beans. Food in America consisted of traditions that
were adapted from England, but up until the end of this century, the presence
of new ingredients along with the contact between diverse ethnic groups
influenced experimentation. Industrialization was also a turning point that
changed how food affected the nation.
During the period of
industrialization, food began to be mass produced, mass marketed, and
standardized. 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 twenties, freezing
methods as well as the earliest cafeterias and fast food establishments
emerged. This point in time is when processed and nationally distributed foods
became a huge part of the nation's diet.
Along with changes in food, there
have also been several changes in nutritional guidelines as well. Since 1916, there have been several different
nutrition guidelines issued by the United States government, eventually leading
up to the food pyramid. In 1916, "Food For Young Children" along with
its sequel for adults, "How to Select Foods" was the first USDA guide
to give specific dietary guidelines. Updated in the 1920s to 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 make sure that people got the recommended
nutrients. 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 seven down to four groups that school
children would learn about for decades. In 1979, a guide called
"Food" was published, which addressed the link between too much of
certain foods and chronic diseases. This publication also added "fats,
oils, and sweets" to the four basic food groups and cautioned moderation.
In 1992, the food pyramid was debuted. The USDA introduced this, which
represented proportions of foods in a balanced diet. In 2005, the pyramid got a
makeover and was renamed MyPyramid. Lastly, in 2011, "MyPlate" came
about.
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 (from the
digestion of table sugar) 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 corn and flax oils. 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.
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.
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[10]
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.[11][not
in citation given]
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. 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.
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: XXXX
Cooking
and health
Food
safety
When heat is used in the preparation
of food, it can kill or inactivate potentially 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. Parasites may be introduced
through salad, meat that is uncooked or done rare, and unboiled water.
The sterilizing effect of cooking will depend on temperature, cooking time,
and technique used. However, some bacteria such as Clostridium
botulinum or Bacillus cereus,
can form spores that survive cooking, which then germinate and regrow after the
food has cooled. It is therefore recommended that cooked food should not be
reheated more than once to avoid repeated growths that allow the bacteria to
proliferate to dangerous level.[12]
Cooking prevents many foodborne illnesses
that would otherwise occur if the food was eaten raw. Cooking also increases
the digestibility of some foods such as grains or lactose because most foods,
when raw, are inedible, and some are poisonous. For example kidney beans
are toxic when raw or improperly cooked, due to the presence of phytohaemagglutinin which can be inactivated after cooking for at least ten
minutes at 100 °C.[13]
Slow cooker
however may not reach the desired temperature and cases of poisoning from red
beans cooked in slow cooker have been reported.
Preparation, handling, and storage
of food are other considerations in food safety. According to the USDA, the
temperature range from 40°F to 140 °F, is the "Danger
zone" where bacteria is likely to
proliferate, food therefore should not be stored in this temperature range.
Washing of hands and surfaces, and avoidance of cross-contamination are good
practices in food safety.[14]
Food prepared on plastic cutting boards may be less likely to harbor bacteria
than wooden ones,[15]
other research however suggested otherwise.[16]
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 diluted antibacterial cleaner, or a trip through a dishwasher with a
"sanitize" cycle, are effective methods for reducing the risk of
illness due to contaminated cooking implements.[16]
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.[17]
However, research using an artificial gut has shown that in the specific case
of carotenoids
a greater proportion is absorbed from cooked vegetables than from raw
vegetables.[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.[18]
Sulforaphane,
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.[19]
Cooking
and carcinogens
In a human epidemiological analysis
by Richard Doll and Richard Peto
in 1981, diet was estimated to cause a certain percentage amount of cancers.[20]
Some of these cancers may be caused by carcinogens in food generated during
cooking process, although it is often difficult to identify the specific
components in diet that serve to increase cancer risk. Many food, such as beef
steak and broccoli, contain low concentrations of both carcinogens
and anticarcinogens.[21]
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.[22]
While eating 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%.[22]
Nitrosamines,
present in processed and cooked foods, have also been noted as being
carcinogenic, being linked to colon cancer.
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.[23]
However, in the US, grilled/barbecued meat is the second highest contributor of
the mean daily intake of benzo[a]pyrene
at 21% after ‘bread, cereal and grain’ at 29%.[23]
Baking, grilling or broiling food,
especially starchy foods, until a toasted crust is formed generates significant
concentrations of acrylamide, a possible carcinogen.[24]
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.[25]
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.[26][27]
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."[28]
Heating sugars with proteins or fats
can produce Advanced
glycation end products
("glycotoxins").[29]
These have been linked to ageing and health conditions such as diabetes and
causing obesity.
Deep fried food in restaurants may
contain high level of trans fat which is known to increase level of low-density lipoprotein that 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.[30]
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.
Home-cooking
vs. factory cooking
Although cooking has traditionally
been a process carried out informally in a home or around a communal fire,
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.
"Home-cooking" may be
associated with comfort food, and some commercially produced foods are presented through
advertising or packaging as having been "home-cooked", regardless of their
actual origin.
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