Garlic

Garlic (Allium sativum) is a species in the onion genus, Allium. Its close relatives include the onion, shallot, leek, chive, and Chinese onion.

Garlic is native to Central Asia and northeastern Iran, and has long been a common seasoning worldwide, with a history of several thousand years of human consumption and use. It was known to ancient Egyptians, and has been used both as a food flavoring and as a traditional medicine. In Ancient Rome, it was “much used for food among the poor”. China produces some 80% of the world’s supply of garlic.

Allium sativum grows in the wild in areas where it has become naturalized. The “wild garlic“, “crow garlic“, and “field garlic” of Britain are members of the species Allium ursinumAllium vineale, and Allium oleraceum, respectively. Identification of the wild progenitor of common garlic is difficult, due to the sterility of its many cultivars, which may all be descended from the species Allium longicuspis, which grows wild in central and southwestern Asia. There are at least 120 cultivars originating from Central Asia, making it the main center of garlic biodiversity.

In North America, Allium vineale (known as “wild garlic” or “crow garlic“) and Allium canadense, known as “meadow garlic” or “wild garlic” and “wild onion”, are common weeds in fields. So-called elephant garlic is actually a wild leek (Allium ampeloprasum), and not a true garlic. Single clove garlic (also called pearl or solo garlic) originated in the Yunnan province of China.

Subspecies and varieties

There are two subspecies of A. sativum, ten major groups of varieties, and hundreds of varieties or cultivars.

  • sativumvar. ophioscorodon (Link) Döll, called Ophioscorodon, or hard-necked garlic, includes porcelain garlics, rocambole garlic, and purple stripe garlics. It is sometimes considered to be a separate species, Allium ophioscorodon G.Don.
  • sativumvar. sativum, or soft-necked garlic, includes artichoke garlic, silverskin garlic, and creole garlic.

 

Cultivation

Garlic is easy to grow and can be grown year-round in mild climates. While sexual propagation of garlic is possible, nearly all of the garlic in cultivation is propagated asexually, by planting individual cloves in the ground. In colder climates, cloves are best planted about six weeks before the soil freezes. The goal is to only have the bulbs produce roots and no shoots above the ground. Harvest is in late spring or early summer.

Garlic plants can be grown closely together, leaving enough space for the bulbs to mature, and are easily grown in containers of sufficient depth. Garlic does well in loose, dry, well-drained soils in sunny locations, and is hardy throughout USDA climate zones 4–9. When selecting garlic for planting, it is important to pick large bulbs from which to separate cloves. Large cloves, along with proper spacing in the planting bed, will also increase bulb size. Garlic plants prefer to grow in a soil with a high organic material content, but are capable of growing in a wide range of soil conditions and pH levels.

There are different varieties or subspecies of garlic, most notably hardneck garlic and softneck garlic. The latitude where the garlic is grown affects the choice of type, as garlic can be day-length sensitive. Hardneck garlic is generally grown in cooler climates and produces relatively large cloves, whereas softneck garlic is generally grown closer to the equator and produces small, tightly-packed cloves.

Garlic scapes are removed to focus all the garlic’s energy into bulb growth. The scapes can be eaten raw or cooked.

Diseases

Garlic plants are usually hardy and not affected by many pests or diseases. Garlic plants are said to repel rabbits and moles. The California Department of Food and Agriculture (CDFA) conducts a certification program to assure freedom from nematode and white rot disease caused by Stromatinia cepivora, two pathogens that can both destroy a crop as well as remain in the soil indefinitely, once introduced. Garlic may also suffer from pink root, a typically non-fatal disease that stunts the roots and turns them pink or red; or leek rust. The larvae of the leek moth attack garlic by mining into the leaves or bulbs.

Production

In 2017, world production of garlic was 28.2 million tonnes, with China alone accounting for 79% of the total (table).

The United States grows less than 1% of China’s production. Much of the garlic production in the United States is centered in Gilroy, California, which calls itself the “Garlic Capital of the World”.

Properties

Fresh or crushed garlic yields the sulfur-containing compounds alliin, ajoene, diallyl polysulfides, vinyldithiins, S-allylcysteine, and enzymes, saponins, flavonoids, and Maillard reaction products, which are not sulfur-containing compounds.

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 (cytosol). 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 react 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 onion, shallot, or leeks. Although many humans enjoy the taste of garlic, these compounds are believed to have evolved as a defensive mechanism, deterring animals such as birds, insects, and worms from eating the plant. Because of this, people throughout history have used garlic to keep away insects such as mosquitoes and slugs.

A large number of sulfur compounds contribute to the smell and taste of garlic. Allicin has been found to be the compound most responsible for the “hot” sensation of raw garlic. This chemical opens thermo-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. Allicin, along with its decomposition products diallyl disulfide and diallyl trisulfide, are major contributors to the characteristic odor of garlic, with other allicin-derived compounds, such as vinyldithiins and ajoene. Because of its strong odor, garlic is sometimes called the “stinking rose”. When eaten in quantity, garlic may be strongly evident in the diner’s sweat and garlic 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.

The well-known phenomenon of “garlic breath” is allegedly alleviated by eating fresh parsley. The herb is, therefore, included in many garlic recipes, such as pistoupersillade, and the garlic butter spread used in garlic bread.

Because of the AMS in the bloodstream, it is believed by some to act as a mosquito repellent, but no clinically reported evidence suggests it is actually effective.

Abundant sulfur compounds in garlic are also responsible for turning garlic green or blue during pickling and cooking. Under these conditions (i.e. acidity, heat) the sulfur-containing compound alliin reacts with common amino acids to make pyrroles, clusters of carbon-nitrogen rings. These rings can be linked together into polypyrrole molecules. Ring structures absorb particular wavelengths of light and thus appear colored. The two-pyrrole molecule looks red, the three-pyrrole molecule looks blue, and the four-pyrrole molecule looks green (like chlorophyll, a tetrapyrrole). Like chlorophyll, the pyrrole pigments are safe to eat.

Upon cutting, similar to a color change in onion caused by reactions of amino acids with sulfur compounds, garlic can turn green.

Uses

Culinary uses

Garlic is widely used around the world for its pungent flavor as a seasoning or condiment.

The garlic plant’s bulb is the most commonly used part of the plant. With the exception of the single clove types, garlic bulbs are normally divided into numerous fleshy sections called cloves. Garlic cloves are used for consumption (raw or cooked) or for medicinal purposes. They have a characteristic pungent, spicy flavor that mellows and sweetens considerably with cooking. The distinctive aroma is mainly due to organosulfur compounds including allicin present in fresh garlic cloves and ajoene which forms when they are crushed or chopped. A further metabolite allyl methyl sulfide is responsible for garlic breath.

Other parts of the garlic plant are also edible. The leaves and flowers (bulbils) on the head (spathe) are sometimes eaten. They are milder in flavor than the bulbs, and are most often consumed while immature and still tender. Immature garlic is sometimes pulled, rather like a scallion, and sold as “green garlic”. When green garlic is allowed to grow past the “scallion” stage, but not permitted to fully mature, it may produce a garlic “round”, a bulb like a boiling onion, but not separated into cloves like a mature bulb. It imparts a garlic flavor and aroma in food, minus the spiciness. Green garlic is often chopped and stir-fried or cooked in soup or hot pot in Southeast Asian (i.e. Vietnamese, Thai, Myanmar, Lao, Cambodian, Singaporean), and Chinese cookery, and is very abundant and low-priced. Additionally, the immature flower stalks (scapes) of the hardneck and elephant types are sometimes marketed for uses similar to asparagus in stir-fries.

Inedible or rarely eaten parts of the garlic plant include the “skin” covering each clove and root cluster. The papery, protective layers of “skin” over various parts of the plant are generally discarded during preparation for most culinary uses, though in Korea immature whole heads are sometimes prepared with the tender skins intact. The root cluster attached to the basal plate of the bulb is the only part not typically considered palatable in any form. An alternative is to cut the top off the bulb, coat the cloves by dribbling olive oil (or other oil-based seasoning) over them, and roast them in an oven. 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. In Korea, heads of garlic are heated over the course of several weeks; the resulting product, called black garlic, is sweet and syrupy, and is exported to the United States, United Kingdom, and Australia.

Garlic may be applied to different kinds of bread, usually in a medium of butter or oil, to create a variety of classic dishes, such as garlic bread, garlic toast, bruschetta, crostini, and canapé. The flavor varies in intensity and aroma with the different cooking methods. It is often paired with onion, tomato, or ginger.

Immature scapes are tender and edible. They are also known as “garlic spears”, “stems”, or “tops”. Scapes generally have a milder taste than the cloves. They are often used in stir frying or braised like asparagus. Garlic leaves are a popular vegetable in many parts of Asia. The leaves are cut, cleaned, and then stir-fried with eggs, meat, or vegetables.

Garlic powder has a different taste from fresh garlic. If used as a substitute for fresh garlic, 1/8 teaspoon of garlic powder is approximate to one clove of garlic.

This post is also available in: Persian Russian

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