Malts
Barley is the most commonly malted grain, in part because of its high diastatic power or enzyme content, though wheat and rye are also used. 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.
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