出典(authority):フリー百科事典『ウィキペディア（Wikipedia）』「2013/02/14 16:11:21」(JST)
Malt is germinated cereal grains that have been dried in a process known as "malting". The grains are made to germinate by soaking in water, and are then halted from germinating further by drying with hot air.[1][2][3][4] Malting grains develops the enzymes required to modify the grain's starches into sugars, including the monosaccharide glucose, the disaccharide maltose, the trisaccharide maltotriose, and higher sugars called maltodextrines. It also develops other enzymes, such as proteases, which break down the proteins in the grain into forms that can be used by yeast. Malt also contains small amounts of other sugars, such as sucrose and fructose, which are not products of starch modification but were already in the grain.
Malted grain is used to make beer, whisky, malted shakes, malt vinegar, confections such as Maltesers and Whoppers, flavored drinks such as Horlicks, Ovaltine and Milo, and some baked goods, such as malt loaf, bagels and rich tea biscuits. Malted grain that has been ground into a coarse meal is known as "sweet meal".[5][6] Various cereals are malted, though barley is the most common. A high-protein form of malted barley is often a label-listed ingredient in blended flours typically used in the manufacture of yeast breads and other baked goods.[7]
The term "malt" refers to several products of the process: the grains to which this process has been applied, for example malted barley; the sugar, heavy in maltose, derived from such grains, such as the baker's malt used in various cereals; or a product based on malted milk, similar to a malted milkshake (i.e., "malts").
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Malting is the process of converting barley into malt, for use in brewing, distilling, or in foods and takes place in a maltings, sometimes called a malthouse, or a malting floor. The sprouted barley is kiln-dried by spreading it on a perforated wooden floor. Smoke, coming from an oasting fireplace (via smoke channels) is then used to heat the wooden floor and the sprouted grains. The temperature is usually around 55 °C (131 °F). A typical floor maltings is a long, single-storey building with a floor that slopes slightly from one end of the building to the other. Floor maltings began to be phased out in the 1940s in favour of "pneumatic plants". Here, large industrial fans are used to blow air through the germinating grain beds and to pass hot air through the malt being kilned. Like floor maltings, these pneumatic plants are batch processes, but of considerably greater size, typically 100 ton batches compared with 20 ton batches for floor malting.
The malting process starts with drying the grains to a moisture content below 14%, and then storing for around six weeks to overcome seed dormancy. When ready, the grain is immersed or steeped in water two or three times over two or three days to allow the grain to absorb moisture and to start to sprout. When the grain has a moisture content of around 46%, it is transferred to the malting or germination floor, where it is constantly turned over for around five days while it is air-dried. The grain at this point is called "green malt". The green malt is then kiln-dried to the desired colour and specification.[8] Malts range in colour from very pale through crystal and amber to chocolate or black malts.[9]
Barley is the most commonly malted grain, in part because of its high diastatic power or enzyme content, though wheat, rye, oats and rice are also used.[10] Also very important is the retention of the grain's husk, even after threshing, unlike the bare seeds of threshed wheat or rye. This protects the growing acrospire (developing plant embryo) from damage during malting, which can easily lead to mold growth. It also allows the mash of converted grain to create a filter bed during lautering (see brewing). Malt is often divided into two categories by brewers: base malts and specialty malts. Base malts have enough diastatic power to convert their own starch and usually that of some amount of starch from unmalted grain, called adjuncts. Specialty malts have little diastatic power; they are used to provide flavor, color, or "body" (viscosity) to the finished beer. Specialty caramel or crystal malts have been subjected to heat treatment to convert their starches to sugars nonenzymatically. Within these categories is a variety of types distinguished largely by the kilning temperature (see mash ingredients). In addition, malts are distinguished by the two major species of barley used for malting, two-row and six-row.[11]
Malt extract is also known as extract of malt. It is a sweet, treacly substance used as a dietary supplement.[12] It was popular in the first half of the twentieth century as a supplement for the children of the British urban working-class, whose diet was often deficient in vitamins and minerals. Children were given cod liver oil for the same reason but it proved so unpalatable that it was combined with extract of malt to produce "Malt and Cod-Liver Oil." It was given as a "strengthening medicine" by Kanga to Roo and Tigger in The House at Pooh Corner.
The 1907 British Pharmaceutical Codex's instructions for making nutritional extract of malt do not include a mash-out at the end of extraction, and include the use of lower mash temperatures than is typical with modern beer-brewing practices. The Codex indicates that diastatic activity is to be preserved by the use of temperatures not exceeding 55 °C (131 °F).
Malt extract production
Malt extract is frequently used in the brewing of beer. Its production begins by germinating barley grain in a process known as malting. This procedure entails immersing barley in water to encourage the grain to sprout, then drying the barley to halt the progress when the sprouting begins. The drying step stops the sprouting, but the enzymes remain active due to the low temperatures used in base malt production.[13] In one before-and-after comparison, malting decreased barley's extractable starch content by about 7% on a dry matter basis, and turned that portion into various other carbohydrates.[14]
In the next step, brewers use a process called mashing to extract the sugars. Brewers warm cracked malt in temperature-modulated water, activating the enzymes,[15] which cleave more of the malt's remaining starch into various sugars, the largest percentage of which is maltose.[14] Modern beer mashing practices typically include high enough temperatures at mash-out to deactivate remaining enzymes, thus it is no longer diastatic. The liquid produced from this, wort, is then concentrated by using heat or a vacuum procedure to evaporate water[12] from the mixture.
The concentrated wort is called malt extract. Brewers have the option of using a liquid (LME) or dry (DME) form of it. Each has its pros and cons, so the choice is dependent solely on the individual brewer's preferences.
Liquid malt extract is a thick syrup. Some brewers choose to work only with LME, because they feel it works best for the result they wish to achieve. Also, it requires one less processing step, so it is appealing to those favoring the purest form of product available. However, it is very sticky and, therefore, messier to work with and has a shorter shelf life, and some feel the results are just as good with DME.
A new encapsulating technology permits the production of malt granules. Malt granules are the dried liquid extract from malt used in the brewing or distilling process.[16]
Scientists aim to discover what goes on inside barley grains as they become malted to help plant breeders produce better malting barley for food and beverage products. Agricultural Research Service scientists are interested in specialized enzymes called serine-class proteases[17] that digest beta-amylases, which convert carbohydrates into "simple sugars" during the sprouting process.[18] The enzyme also breaks down stored proteins into their amino acid derivatives. The balance of proteins and carbohydrates broken down by the enzyme affect the malt’s flavor.
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| リンク元 | 「麦芽」「cereal」「triticale」「wheat germ」 |
| 拡張検索 | 「maltophilia」「isomaltase」「malt extract」 |
| 関連記事 | 「MALT」 |