Malts And Malting

Malts are cereal grains that have been germinated to a limited extent to alter their physical and biochemical states. Usually they are dried and partially cooked (cured), and the rootlets are removed before use (1-10). There are many types of malt. Barley malts vary in color from a pale straw-yellow to nearly black. The darker malts have characteristic colors and aromas and they give particular flavors to products made from them, but in contrast to pale malts, they contain few or no enzymes. Most malts are prepared from barley, but smaller amounts are made from wheat, rye, possibly triticale, oats, sorghum, and millet. Barley is often preferred for malting because the adherent husk protects the grain during handling and malting whereas naked grains, like wheat and sorghum, are readily damaged and crushed. Barley can be induced to germinate evenly and generate useful levels of hydrolytic enzymes (including cytases, proteases, and amylases), and varieties are available for making many kinds of malts. Also, the relatively low gelatinization temperature of large barley starch granules (about 60-65°C [140-149°F]) renders them easily converted when the malt is mashed. Malts are used in making beers, African-style opaque beers, whiskeys, malt vinegars, and syrupy extracts and in some bakery products, confectionery, breakfast cereals, baby foods, malt coffee, and malted-milk beverages (1-10).

Small amounts of malt flours are used in baking. However, for most purposes malts must be mashed, sometimes after they are mixed with other starch-containing materials, to produce a sugary solution or extract (1,3,4). In mashing, ground malt is mixed in a chosen ratio with warm water and the mixture is heated, in a controlled way, to progressively higher temperatures. After a time the liquid or sweet wort, which contains the extract materials dissolved from the malt, is separated from the residual undissolved solids, known as spent grains or draff. The latter is usually used to feed animals, but other uses are being sought. The sweet wort is processed further to produce beer, whiskey, vinegar, extract, diastase, and so on (1-10). However, mashing to prepare opaque beers is somewhat different (1,3). If ground malt is extracted with cold, slightly alkaline water to prevent enzyme activity, then about 18 to 21% of the malt solids (the cold-water extract) dissolve. If the malt is mashed with hot water (e.g., 65°C; 149 °F) then the hot-water extract is about 77 to 83% of the dry matter of the malt, depending on the quality of the malt and the mashing procedure used. Mashing processes vary in the degree of grinding of the malt, the liquid-to-solids ratio, the temperatures used, and the durations of the different stages. The hot-water extract is much larger than the cold-water extract because during the hot mash, enzymes act to hydrolyze insoluble materials to give soluble products (1,2,4,9,10). Some degradation of proteins and cell-wall polysaccharides occurs, but the main change is the conversion of insoluble starch into a complex mixture of soluble sugars and dextrins. The increase in the density of wort above that of water is a measure of the amount of extract in solution (1,4). For most purposes the yield of hot-water extract and its quality (color, level of fermentable sugars, contents of amino acids and proteins, etc.) are the major measures of malt quality. In making beers, malt vinegars, and whiskeys it is the simple sugars that yeasts convert to ethanol and carbon dioxide (1,2,3,5,9). Malts are usually analyzed by one of three internationally recognized systems (1,4).

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