Garlic
2008/9 Schools Wikipedia Selection. Related subjects: Plants
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| Image:Allium sativum plant.jpg Allium sativum, known as garlic
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| Allium sativum L. |
Allium sativum L., commonly known as garlic, is a species in the onion family Alliaceae. Its close relatives include the onion, the shallot, and the leek. Garlic has been used throughout recorded history for both culinary and medicinal purposes. It has a characteristic pungent, spicy flavor that mellows and sweetens considerably with cooking. There is much folklore and confusion surrounding this ancient plant.
A bulb of garlic, the most commonly used part of the plant, is divided into numerous fleshy sections called cloves. The cloves are used as seed, for consumption (raw or cooked), and for medicinal purposes. The leaves, stems (scape) and flowers (bulbils) on the head (spathe) are also edible and most often consumed while immature and still tender. The papery, protective layers of 'skin' over various parts of the plant and the roots attached to the bulb are the only parts not considered palatable.
Origin and distribution
The ancestry of cultivated garlic, according to Zohary and Hopf, is not definitely established: "a difficulty in the identification of its wild progenitor is the sterility of the cultivars."
Allium sativum grows in the wild in areas where it has become naturalised; it probably descended from the species Allium longicuspis, which grows wild in south-western Asia. The 'wild garlic', 'crow garlic' and 'field garlic' of Britain are the species Allium ursinum, Allium vineale and Aleum oleraceum, respectively. In North America, 'Allium vineale, known as 'wild-' or 'crow garlic', and Allium canadense, known as 'meadow-' or 'wild garlic' and 'wild onion', are common weeds in fields. One of the best known "garlics," the so-called elephant garlic, is actually a wild leek ( Allium ampeloprasum).
Cultivation
Garlic is easy to grow and can be grown year-round in mild climates. In cold climates, cloves can be planted in the ground about six weeks before the soil freezes, and harvested in late spring. Garlic plants are not attacked by pests. They can suffer from pink root, a disease that stunts the roots and turns them pink or red. Garlic plants can be grown close together, leaving enough room for the bulbs to mature, and are easily grown in containers of sufficient depth.
Production Trends
Garlic is grown globally, but China is by far the largest producer of garlic with approximately 23 billion pounds annually, accounting for over 75% of world output. India (4%) and South Korea (3%) follow, with the United States (2%) in fourth place, where garlic is grown primarily as a cash crop in every state except for Alaska. This leaves 16% of global garlic production in countries that produce less than 2% of global output.
Uses
Culinary uses
Garlic is widely used around the world for its pungent flavor, as a seasoning or condiment. The flavour varies in intensity and aroma with cooking methods. It is often paired with onion, tomato, or ginger. The parchment-like skin is much like the skin of an onion, and is typically removed before using in raw or cooked form. An alternative is to cut the top off the bulb, coat cloves of garlic by dribbling olive oil (or other oil based seasoning) over them and roast them in the oven. The garlic softens and can be extracted from the cloves by squeezing the (root) end of the bulb or individually by squeezing one end of the clove.
Oils are often flavored with garlic cloves. Commercially prepared oils are widely available, but when preparing garlic-infused oil at home, there is a risk of botulism if the product is not stored properly. To reduce this risk, the oil should be refrigerated and used within one week. Manufacturers add acids and/or other chemicals to eliminate the risk of botulism in their products.
In Chinese cuisine, the young bulbs are pickled for 3–6 weeks in a mixture of sugar, salt and spices. In Russia and the Caucasus, the shoots are pickled and eaten as an appetizer.
It is widely used with kebabs, mezes and various meals in Turkish cuisine.
Immature scapes are tender and edible. They are also known as 'garlic spears', 'stems', or 'tops'. Scapes generally have a milder taste than cloves. They are often used in stir frying or prepared like asparagus. Garlic leaves are a popular vegetable in many parts of Asia, particularly Chinese, Vietnamese, Cambodian, Laotian and Korean cuisines. The leaves are cut, cleaned and then stir-fried with eggs, meat, or vegetables.
Garlic is essential to several Mediterranean dishes. Mixing garlic with eggs and olive oil produces aioli ("garlic and oil" in Provençal). The Spanish variant does not use eggs. Garlic, oil, and a chunky base produce skordalia (from the Greek and Italian names of garlic). Blending garlic, almond, oil and soaked bread produces ajoblanco (ajo blanco is Spanish for "white garlic"). Le Tourin is a French garlic soup.
In Asia, garlic is fundamental to Korean and Thai cuisine. In Chinese cuisine, it is usually chopped and stir-fried with chopped ginger and other aromatics in oil as the basis of sauces. Japanese cuisine uses very little garlic.
Storage
Domestically, garlic is stored warm (above 18°C or 64°F) and dry, to keep it dormant (so that it does not sprout). It is traditionally hung; softneck varieties are often braided in strands called "plaits", or in short plaits. Plaits are sometimes called grappes, following French usage.
Commercially, garlic is stored at 0°C, also dry.
Historical use
From the earliest times garlic has been used as a food. It formed part of the diet of the Israelites in Egypt (Numbers 11:5) and of the labourers employed by Khufu in constructing the pyramid. Garlic is still grown in Egypt, but the Syrian variety is the kind most esteemed now (see Rawlinson's Herodotus, 2.125).
It was consumed by the ancient Greek and Roman soldiers, sailors and rural classes (Virgil, Ecologues ii. 11), and, according to Pliny the Elder ( Natural History xix. 32), by the African peasantry. Galen eulogizes it as the "rustic's theriac" (cure-all) (see F Adams's Paulus Aegineta, p. 99), and Alexander Neckam, a writer of the 12th century (see Wright's edition of his works, p. 473, 1863), recommends it as a palliative of the heat of the sun in field labor.
In his Natural History Pliny gives an exceedingly long list of scenarios in which it was considered beneficial (N.H. xx. 23). Dr. T. Sydenham valued it as an application in confluent smallpox, and, says Cullen (Mat. Med. ii. p. 174, 1789), found some dropsies cured by it alone. Early in the 20th century, it was sometimes used in the treatment of pulmonary tuberculosis or phthisis.
Garlic was rare in traditional English cuisine (though it is said to have been grown in England before 1548), and has been a much more common ingredient in Mediterranean Europe. Garlic was placed by the ancient Greeks on the piles of stones at cross-roads, as a supper for Hecate ( Theophrastus, Characters, The Superstitious Man); and according to Pliny, garlic and onions were invoked as deities by the Egyptians at the taking of oaths. (Pliny also states that garlic de-magnetizes loadstones, which is not factual.) The inhabitants of Pelusium in lower Egypt, who worshipped the onion, are said to have had an aversion to both onions and garlic as food.
To prevent the plant from running to leaf, Pliny (N.H. xix. 34) advised bending the stalk downward and covering with earth; seeding, he observes, may be prevented by twisting the stalk (by "seeding", he most likely means the development of small, less potent bulbs).
Medicinal use and health benefits
| Components of garlic | |
| Phytochemicals | Nutrients |
| Allicin | Calcium |
| Beta-carotene | Folate |
| Beta-sitosterol | Iron |
| Caffeic acid | Magnesium |
| Chlorogenic acid | Manganese |
| Diallyl disulfide | Phosphorus |
| Ferulic acid | Potassium |
| Geraniol | Selenium |
| Kaempferol | Zinc |
| Linalool | Vitamin B1 (Thiamine) |
| Oleanolic acid | Vitamin B2 (Riboflavin) |
| P-coumaric acid | Vitamin B3 (Niacin) |
| Phloroglucinol | Vitamin C |
| Phytic acid | |
| Quercetin | |
| Rutin | |
| S-Allyl cysteine | |
| Saponin | |
| Sinapic acid | |
| Stigmasterol | |
| Alliin | |
| Source: Balch p 97 | |
Garlic has been used as both food and medicine in many cultures for thousands of years, dating as far back as the time that the Egyptian pyramids were built. Garlic is claimed to help prevent heart disease including atherosclerosis, high cholesterol, high blood pressure, and cancer.
Animal studies, and some early investigational studies in humans, have suggested possible cardiovascular benefits of garlic. A Czech study found garlic supplementation reduced accumulation of cholesterol on vascular walls of animals. Another study had similar results, with garlic supplementation significantly reducing the placque in the aortas of cholesterol-fed rabbits. Another study showed that supplementation with garlic extract inhibited vascular calcification in human patients with high blood cholesterol.
However, a NIH-funded randomized clinical trial published in Archives of Internal Medicine in 2007 found that consumption of garlic, in any form, did not reduce cholesterol levels in patients with moderately high baseline levels.
With regard to this clinical trial, theheart.org reports:
| “ | Despite decades of research suggesting that garlic can improve cholesterol profiles, a new NIH-funded trial found absolutely no effects of raw garlic or garlic supplements on LDL, HDL, or triglycerides... The findings underscore the hazards of meta-analyses made up of small, flawed studies and the value of rigorously studying popular herbal remedies. | ” |
In 2007 a BBC news story reported that Allium sativum may have beneficial properties, such as preventing and fighting the common cold. This assertion has the backing of long tradition. Traditional British herbalism used garlic for hoarseness and coughs, both as a syrup and in a salve made of garlic and lard, which was rubbed on the chest and back. The Cherokee also used it as an expectorant for coughs and croup.
Allium sativum has been found to reduce platelet aggregation and hyperlipidemia.
Garlic is also alleged to help regulate blood sugar levels. Regular and prolonged use of therapeutic amounts of aged garlic extracts lower blood homocysteine levels, and has shown to prevent some complications of diabetes mellitus. People taking insulin should not consume medicinal amounts of garlic without consulting a physician. In such applications, garlic must be fresh and uncooked, or the allicin will be lost.
Allium sativum may also possess cancer-fighting properties due to the presence of allylic sulfur compounds such as diallyl disulfide (DADs), believed to be an anticarcinogen.
In 1858, Louis Pasteur observed garlic's antibacterial activity, and it was used as an antiseptic to prevent gangrene during World War I and World War II. More recently it has been found from a clinical trial that a mouthwash containing 2.5% fresh garlic shows good antimicrobial activity, although the majority of the participants reported an unpleasant taste and halitosis.
In modern naturopathy, garlic is used as a treatment for intestinal worms and other intestinal parasites, both orally and as an anal suppository. Garlic cloves are used as a remedy for infections (especially chest problems), digestive disorders, and fungal infections such as thrush.
Garlic has been reasonably successfully used in AIDS patients to treat cryptosporidium in an uncontrolled study in China. It has also been used by at least one AIDS patient to treat toxoplasmosis, another protozoal disease.
Garlic supplementation in rats along with a high protein diet has been shown to boost testosterone levels.
To maximise health benefits from consuming cooked garlic, it has been suggested to allow crushed or chopped garlic to rest for 15 minutes before use to allow enzyme reactions to occur. However the primary compound of interest from this reaction, allicin, is generally deactivated during cooking due to its instability, and may be more beneficial consumed raw.
Properties
When crushed, Allium sativum yields allicin, a powerful antibiotic and anti-fungal compound ( phytoncide). However due to poor bioavailability it is of limited use for oral consumption. It also contains alliin, ajoene, enzymes, vitamin B, minerals, and flavonoids.
The percentage composition of the bulbs is given by E. Solly (Trans. Hon. Soc. Loud., new ser., iii. p. 60) as water 84.09%, organic matter 13.38%, and inorganic matter 1.53% - that of the leaves being water 87.14%, organic matter 11.27% and inorganic matter 1.59%.
The phytochemicals responsible for the sharp flavor of garlic are produced when the plant's cells are damaged. When a cell is broken by chopping, chewing, or crushing, enzymes stored in cell vacuoles trigger the breakdown of several sulfur-containing compounds stored in the cell fluids. The resultant compounds are responsible for the sharp or hot taste and strong smell of garlic. Some of the compounds are unstable and continue to evolve over time. Among the members of the onion family, garlic has by far the highest concentrations of initial reaction products, making garlic much more potent than onions, shallots, or leeks. Although people have come to enjoy the taste of garlic, these compounds are believed to have evolved as a defensive mechanism, deterring animals like birds, insects, and worms from eating the plant.
A large number of sulfur compounds contribute to the smell and taste of garlic. Diallyl disulfide is believed to be an important odour component. Allicin has been found to be the compound most responsible for the spiciness of raw garlic. This chemical opens thermoTRP ( transient receptor potential) channels that are responsible for the burning sense of heat in foods. The process of cooking garlic removes allicin, thus mellowing its spiciness.
When eaten in quantity, garlic may be strongly evident in the diner's sweat and breath the following day. This is because garlic's strong smelling sulfur compounds are metabolized forming allyl methyl sulfide. Allyl methyl sulfide (AMS) cannot be digested and is passed into the blood. It is carried to the lungs and the skin where it is excreted. Since digestion takes several hours, and release of AMS several hours more, the effect of eating garlic may be present for a long time.
This well-known phenomenon of "garlic breath" is alleged to be alleviated by eating fresh parsley. The herb is, therefore, included in many garlic recipes, such as Pistou, Persillade and the garlic butter spread used in garlic bread. However, since the odour results mainly from digestive processes placing compounds such as AMS in the blood, and AMS is then released through the lungs over the course of many hours, eating parsley provides only a temporary masking. One way of accelerating the release of AMS from the body is the use of a sauna. Due to its strong odour, garlic is sometimes called the "stinking rose".
Because of the AMS in the bloodstream, it is believed by some to act as a mosquito repellent. However there is no evidence to suggest that garlic is actually effective for this purpose.
Superstition and mythology
Garlic has been regarded as a force for both good and evil. A Christian myth considers that after Satan left the Garden of Eden, garlic arose in his left footprint, and onion in the right. In Europe, many cultures have used garlic for protection or white magic, perhaps owing to its reputation as a potent preventative medicine. Central European folk beliefs considered garlic a powerful ward against demons, werewolves, and vampires. To ward off vampires, garlic could be worn, hung in windows or rubbed on chimneys and keyholes.
Colloidal silver is often used as antibacterial agent. As with silver, the association of garlic to evil spirits may be based on the antibacterial, antiparasitic value of garlic, which could prevent infections that lead to delusions, and other related mental illness symptoms.
In Northeastern India, it is believed that garlic mixed with water spread around the home will keep snakes from entering.
Cautions
- Known adverse effects of garlic include halitosis (non-bacterial), indigestion, nausea, emesis and diarrhea.
- Garlic may interact with warfarin, antiplatelets, saquinavir, antihypertensives, Calcium channel blockers, hypoglycemic drugs, as well as other medications. Consult a health professional before taking a garlic supplement or consuming excessive amounts of garlic.
- Garlic can thin the blood similar to the effect of aspirin.
- Cases of botulism have been caused by consuming garlic-in-oil preparations. It is important to add acid when creating these mixtures and to keep them refrigerated to retard bacterial growth.
- Whilst culinary quantities are considered safe for consumption, very high quantities of garlic and garlic supplements have been linked with an increased risk of bleeding, particularly during pregnancy and after surgery and child birth. Some breastfeeding mothers have found their babies slow to feed and have noted a garlic odour coming from their baby when they have consumed garlic. The safety of garlic supplements had not been determined for children.
- The side effects of long-term garlic supplementation, if any exist, are largely unknown and no FDA-approved study has been performed. However, garlic has been consumed for several thousand years without any adverse long-term effects, suggesting that modest quantities of garlic pose, at worst, minimal risks to normal individuals. Possible side effects include gastrointestinal discomfort, sweating, dizziness, allergic reactions, bleeding, and menstrual irregularities.
- Some degree of liver toxicity has been demonstrated in rats, particularly in large quantities
- There have been several reports of serious burns resulting from garlic being applied topically for various purposes, including naturopathic uses and acne treatment. On the basis of numerous reports of such burns, including burns to children, topical use of raw garlic, as well as insertion of raw garlic into body cavities is discouraged. In particular, topical application of raw garlic to young children is not advisable.
- Garlic and onions are toxic to cats and dogs.