Meat

Meat is animal flesh that is used as food. Most often, this means the skeletal muscle and associated fat, but it may also describe other edible tissues such as organs, livers, skin, brains, bone marrow, kidneys, or lungs. Early hunter-gatherers depended on the organized hunting of large animals such as bison and deer. Several breeds of sheep were established in ancient Mesopotamia and Egypt by 3500–3000 BC. and several breeds were established by 2500 BC. Modern domesticated cattle fall into the groups Bos taurus (European cattle) and Bos indicus (zebu), both descended from the now-extinct aurochs.

* Domestic pigs, which are descended from wild boars, are known to have existed about 2500 BC in modern-day Hungary and in Troy; earlier pottery from Jericho and Egypt depicts wild pigs. Pork sausages and hams were of great commercial importance in Greco-Roman times.

Modern agriculture employs a number of techniques, such as progeny testing, to make animals evolve rapidly towards having the qualities desired by meat producers. For instance, in the wake of well-publicised health concerns associated with saturated fats in the 1980s, the fat content of UK beef, pork and lamb fell from 20–26 percent to 4–8 percent within a few decades, both due to selective breeding for leanness and changed methods of butchery.

Even though it is a very old industry, meat production continues to be shaped strongly by the rapidly evolving demands of customers. The trend towards selling meat in pre-packaged cuts has increased the demand for larger breeds of cattle, which are better suited to producing such cuts. Even more animals not previously exploited for their meat are now being farmed, especially the more agile and mobile species, whose muscles tend to be developed better than those of cattle, sheep or pigs. as well as nonmammals, such as the crocodile, emu and ostrich. Another important trend in contemporary meat production is organic farming which, while providing no organoleptic benefit to meat so produced, meets an increasing demand for numerous reasons.

Growth and development of meat animals

Agricultural science has identified several factors bearing on the growth and development of meat in animals.

Genetics

Several economically important traits in meat animals are heritable to some degree (see the table to the right) and can thus be selected for by breeding. In cattle, certain growth features are controlled by recessive genes which have not so far been controlled, complicating breeding. One such trait is dwarfism; another is the doppelender or "double muscling" condition, which causes muscle hypertrophy and thereby increases the animal's commercial value.

Genetic engineering techniques can shorten breeding programmes significantly because they allow for the identification and isolation of genes coding for desired traits, and for the reincorporation of these genes into the animal genome. To enable such manipulation, research is ongoing () to map the entire genome of sheep, cattle and pigs. although this is not yet practical on a commercial scale.

Environment

Heat regulation in livestock is of great economic significance, because mammals attempt to maintain a constant optimal body temperature. Low temperatures tend to prolong animal development and high temperatures tend to retard it. Static magnetic fields, for reasons still unknown, also retard animal development.

The composition of the diet, especially the amount of protein provided, is also an important factor regulating animal growth. Ruminants, which may digest cellulose, are better adapted to poor-quality diets, but their ruminal microorganisms degrade high-quality protein if supplied in excess. Because producing high-quality protein animal feed is expensive (see also Environmental impact below), several techniques are employed or experimented with to ensure maximum utilization of protein. These include the treatment of feed with formalin to protect amino acids during their passage through the rumen, the recycling of manure by feeding it back to cattle mixed with feed concentrates, or the partial conversion of petroleum hydrocarbons to protein through microbial action. In Australia, for instance, where the soil contains limited phosphate, cattle are being fed additional phosphate to increase the efficiency of beef production. Also in Australia, cattle and sheep in certain areas were often found losing their appetite and dying in the midst of rich pasture; this was at length found to be a result of cobalt deficiency in the soil.

Human intervention

Meat producers may seek to improve the fertility of female animals through the administration of gonadotrophic or ovulation-inducing hormones. In pig production, sow infertility is a common problem, possibly due to excessive fatness. No methods currently exist to augment the fertility of male animals.

Growth hormones, particularly anabolic agents such as steroids, are used in some countries to accelerate muscle growth in animals. and have other effects on the composition of the muscle flesh. Where castration is used to improve control over male animals, its side effects are also counteracted by the administration of hormones. The feeding of antibiotics to certain animals has been shown to improve growth rates also. Even between animals of the same litter and sex there are considerable differences in such parameters as the percentage of intramuscular fat.

Main constituents

Adult mammalian muscle flesh consists of roughly 75 percent water, 19 percent protein, 2.5 percent intramuscular fat, 1.2 percent carbohydrates and 2.3 percent other soluble non-protein substances. These include nitrogenous compounds, such as amino acids, and inorganic substances such as minerals.

Muscle proteins are either soluble in water (sarcoplasmic proteins, about 11.5 percent of total muscle mass) or in concentrated salt solutions (myofibrillar proteins, about 5.5 percent of mass). There are several hundred sarcoplasmic proteins. Most of them – the glycolytic enzymes – are involved in the glycolytic pathway, i.e., the conversion of stored energy into muscle power. The two most abundant myofibrillar proteins, myosin and actin, are responsible for the muscle's overall structure. The remaining protein mass consists of connective tissue (collagen and elastin) as well as organelle tissue. or intramuscular fat, which contains considerable quantities of phospholipids and of unsaponifiable constituents such as cholesterol. while white meat contains more broad fibres that tend to work in short fast bursts. In particular, the muscles of stressed animals are low in water and glycogen, and their pH fails to attain acidic values, all of which results in poor meat quality. Consequently, and also due to campaigning by animal welfare groups, laws and industry practices in several countries tend to become more restrictive with respect to the duration and other circumstances of livestock transports.

Slaughter

Animals are usually slaughtered by being first stunned and then exsanguinated (bled out). Death results from the one or the other procedure, depending on the methods employed. Stunning can be effected through asphyxiating the animals with carbon dioxide, shooting them with a gun or a captive bolt pistol, or shocking them with electric current. In most forms of ritual slaughter, stunning is not allowed.

Draining as much blood as possible from the carcase is necessary because blood causes the meat to have an unappealing appearance and is a very good breeding ground for microorganisms. The exsanguination is accomplished by severing the carotid artery and the jugular vein in cattle and sheep, and the anterior vena cava in pigs.

Dressing and cutting

After exsanguination, the carcase is dressed, that is, the head, feet, hide (except hogs and some veal), excess fat, viscera and offal are removed, leaving only bones and edible muscle. Cattle and pig carcases, but not those of sheep, are then split in half along the mid ventral axis, and the carcase is cut into wholesale pieces.

During the first day after death, glycolysis continues until the accumulation of lactic acid causes the pH to reach about 5.5. The remaining glycogen, about 18 g per kg, is believed to increase the water-holding capacity and tenderness of the flesh when cooked. Rigor mortis sets in a few hours after death as ATP is used up, causing actin and myosin to combine into rigid actomyosin and lowering the meat's water-holding capacity, causing it to lose water ("weep"). In muscles that enter rigor in a contracted position, actin and myosin filaments overlap and cross-bond, resulting in meat that is tough on cooking – hence again the need to prevent pre-slaughter stress in the animal.

Over time, the muscle proteins denature in varying degree, with the exception of the collagen and elastin of connective tissue, and rigor mortis resolves. Because of these changes, the meat is tender and pliable when cooked just after death or after the resolution of rigor, but tough when cooked during rigor.

Spoilage and preservation

The spoilage of meat occurs, if untreated, in a matter of hours or days and results in the meat becoming unappetizing, poisonous or infectious. Spoilage is caused by the practically unavoidable infection and subsequent decomposition of meat by bacteria and fungi, which are borne by the animal itself, by the people handling the meat, and by their implements. Meat can be kept edible for a much longer time – though not indefinitely – if proper hygiene is observed during production and processing, and if appropriate food safety, food preservation and food storage procedures are applied. Without the application of preservatives and stabilizers, the fats in meat may also begin to rapidly decompose after cooking or processing, leading to an objectionable taste known as warmed over flavor.

Methods of preparation

at a street fair in New York City's East Village.]] Meat is prepared in many ways, as steaks, in stews, fondue, or as dried meat like beef jerky. It may be ground then formed into patties (as hamburgers or croquettes), loaves, or sausages, or used in loose form (as in "sloppy joe" or Bolognese sauce). Some meat is cured, by smoking, pickling, preserving in salt or brine (see salted meat and curing). Other kinds of meat are marinated and barbecued, or simply boiled, roasted, or fried. Meat is generally eaten cooked, but there are many traditional recipes that call for raw beef, veal or fish (tartare). Meat is often spiced or seasoned, as in most sausages. Meat dishes are usually described by their source (animal and part of body) and method of preparation.

Meat is a typical base for making sandwiches. Popular varieties of sandwich meat include ham, pork, salami and other sausages, and beef, such as steak, roast beef, corned beef, pepperoni, and pastrami. Meat can also be molded or pressed (common for products that include offal, such as haggis and scrapple) and canned.

Meat nutritional information

:Further information: Nutrition, Foodborne illness, Health concerns associated with red meat All muscle tissue is very high in protein, containing all of the essential amino acids, and in most cases is a good source of zinc, vitamin B₁₂, selenium, phosphorus, niacin, vitamin B₆, choline, riboflavin and iron. Several forms of meat are high in vitamin K₂, which is only otherwise known to be found in fermented foods, with natto having the highest concentration. The fat content of meat can vary widely depending on the species and breed of animal, the way in which the animal was raised, including what it was fed, the anatomical part of the body, and the methods of butchering and cooking. Wild animals such as deer are typically leaner than farm animals, leading those concerned about fat content to choose game such as venison. Decades of breeding meat animals for fatness is being reversed by consumer demand for meat with less fat.

Red meat, such as beef, pork, and lamb, contains many essential nutrients necessary for healthy growth and development in children. Nutrients in red meat include iron, zinc, vitamin B₁₂, and protein.

The table in this section compares the nutritional content of several types of meat. While each kind of meat has about the same content of protein and carbohydrates, there is a very wide range of fat content. It is the additional fat that contributes most to the calorie content of meat, and to concerns about dietary health.

Issues with meat consumption

Ethics

Ethical issues regarding the consumption of meat can include objections to the act of killing animals or the agricultural practices surrounding the production of meat. Reasons for objecting to the practice of killing animals for consumption may include animal rights, environmental ethics, religious doctrine, or an aversion to inflicting pain or harm on other sentient creatures. The religion of Jainism has always opposed eating meat, and there are also many schools of Buddhism, Hinduism and Sikhism that condemn the eating of meat. Some people, while not vegetarians, refuse to eat the flesh of certain animals, such as cats, dogs, horses, or rabbits, due to cultural or religious taboo. In some cases, specific meats (especially from pigs and cows) are forbidden within religious traditions. Some people eat only the flesh of animals which they believe have not been mistreated, and abstain from the meat of animals reared in factory farms or from particular products such as foie gras and veal.

Health

:See Articles: Vegetarianism and Vegan Consumption of large quantities of meat, like overconsumption of any caloric food, has certain adverse effects which can include: obesity, heart disease, and constipation. The common misconception of "I can't eat unless there is meat" is largely due to cultural attitudes and how one is raised to think about food. In recent years, health concerns have been raised about the consumption of meat increasing the risk of cancer. Another study found an increase risk of pancreatic cancer for red meat and pork. That study also suggests that fat and saturated fat are not likely contributors to pancreatic cancer. Animal fat, particularly from ruminants, tends to have a higher percentage of saturated fat vs. monounsaturated and polyunsaturated fat when compared to vegetable fats, with the exception of some tropical plant fats; consumption of which has been correlated with various health problems. The saturated fat found in meat has been associated with significantly raised risks of colon cancer, although evidence suggests that risks of prostate cancer are unrelated to animal fat consumption. USDA claims (see Dietary Guidelines for Americans) that consumption of meat as a source of protein in the human diet is crucial, have been resoundingly contradicted by recent studies.

The correlation of meat consumption to increased risk of heart disease is controversial. Some studies fail to find a link between red meat consumption and heart disease (although the same study found statistically significant correlation between the consumption of processed meat and cancer), while another study, a survey ,conducted in 1960, of 25,153 California Seventh-Day Adventists, found that the risk of heart disease is three times greater for 45-64 year old men who eat meat daily, versus those who did not eat meat. In another study in 2010 involving over one million people who ate meat found that only processed meat had an adverse risk in relation to coronary heart disease. The study suggests that eating 50g (less than 2oz) of processed meat per day increases risk of coronary heart disease by 42%, and diabetes by 19%. Equivalent levels of fat, including saturated fats, in unprocessed meat (even when eating twice as much per day) did not show any deleterious effects, leading the researchers to suggest that "differences in salt and preservatives, rather than fats, might explain the higher risk of heart disease and diabetes seen with processed meats, but not with unprocessed red meats."

A 2009 study by the National Cancer Institute revealed a correlation between the consumption of red meat and increased mortality from cancer and cardiovascular diseases. This study has been criticized for using an improperly validated food frequency questionnaire, which has been shown to have low levels of accuracy.

In response to changing prices as well as health concerns about saturated fat and cholesterol, consumers have altered their consumption of various meats. A USDA report points out that consumption of beef in the United States between 1970–1974 and 1990–1994 dropped by 21%, while consumption of chicken increased by 90%. During the same period of time, the price of chicken dropped by 14% relative to the price of beef. In 1995 and 1996, beef consumption increased due to higher supplies and lower prices.

Cooking

Meat, like any food, can also transmit certain diseases, but complete cooking and avoiding recontamination reduces this possibility.

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 published results of a study which 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 creates "negligible amounts" of HCAs. Also, microwaving meat before cooking may reduce HCAs by 90%.

Nitrosamines, present in processed and cooked foods, have been noted as being carcinogenic, being linked to colon cancer. Also, toxic compounds called PAHs, or Polycyclic aromatic hydrocarbons, present in processed, smoked and cooked foods, are known to be carcinogenic.

In vitro and imitation

:Main articles: Imitation meat, In vitro meat

Various forms of imitation meat have been created to satisfy people wishing to reduce or eliminate meat consumption for health, environmental, or ethical considerations, but who still wish to taste the flavor and texture of meat. They are typically some form of processed soybean, (tofu, tempeh), but they can also be based on wheat gluten or even fungus (quorn).

In vitro meat, also known as cultured meat, is animal flesh that has never been part of a complete, living animal. Several research projects are currently experimentally growing in vitro meat, but no meat has yet been produced for public consumption. The goal is to grow fully developed muscle organs, but the first generation will most likely be minced meat products.

Environmental impact

The UN Food and Agriculture Organization (FAO) has estimated that direct emissions from meat production account for about 18% of the world's total greenhouse gas emissions. The FAO figure accounts for the entire meat production cycle - clearing forested land, making and transporting fertiliser, burning fossil fuels in agricultural machinery, and the front and rear end emissions of cattle and sheep. In tracking food animal production from the feed through to the dinner table, the inefficiencies of grain fed meat, milk and egg production range from a 4:1 energy input to protein output ratio up to 54:1, in the opinion of Roger Segelken.

See also

Beef hormone controversy

Bushmeat

Culinary name

Food production

Food science

Gristle

List of meat animals

Livestock/Domestication

Meat-free day

Meat on the bone

Mechanically separated meat

Red meat

Roadkill cuisine

Sinew

Veganism

References

Footnotes

External links

American Meat Science Association website

Qualitionary - Legal Definitions - Meat

* Meat