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Malting

Barley is spread out on the floor of a malt house during a traditional malting process. Malting is the process of converting barley or other cereal grains into malt, for use in brewing, distilling, or in foods and takes place in a malting, sometimes called a malts house, or a malting floor. 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 malts is then kiln-dried to the desired colour and specification. Malts range in colour from very pale through crystal and amber to chocolate or black malts.

 

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 malting is a long, single-storey building with a floor that slopes slightly from one end of the building to the other. Floor malting 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.

 

Malt

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. 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 acrospires (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 non-enzymatically. 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.