After mashing and gelatinization, distillers add thermostable α-amylases to the cooker. α-amylases hydrolyze the 1,4-α-glucosidic linkages in amylose and amylopectin. That yields soluble short-chain dextrins. These are more suited to saccharification to fermentable glucose or maltose. In that way, thermostable α-amylases help ensure complete starch conversion.
Making beverage alcohol involves converting starch into fermentable sugars. Yeast then transforms these sugars into alcohol. Liquefaction of starch is the first enzymatic step in this process. Liquefaction prepares starch for further breakdown to produce fermentable sugars. The liquefaction step is critical to the overall efficiency of a distiller's process. Effective liquefaction ensures complete starch conversion to fermentable sugars.
In water below 50°C, unmodified starch granules are generally insoluble. To make them soluble, distillers use a process known as gelatinization. They heat the raw material - whether starch, potatoes or grain - usually under pressure. That makes the starch granules absorb a large amount of water and swell to many times their original size. Then the pressure is suddenly released, disrupting the previously organized starch structure. The starch granules lose their individual crystalline structure to become a viscous liquid gel.
Expanding and opening compact starch granules in this way prepares them for liquefaction. In liquefaction, α-amylases hydrolyze the gelatinized starch to yield soluble dextrins. This converts starch in the mash into a free-flowing liquid. Heat-stable α-amylases can go directly into the cooker. Non heat-stable α-amylases must go into the mash tun after cooking.
Starch is a mixture of two carbohydrate polymers; amylose and amylopectin. Both are made up of glucose monomers linked together by glucosidic bonds. α-amylases are endo-enzymes. They work from the inside of the starch molecule, breaking it down randomly. They hydrolyze the 1,4-α-glucosidic linkages in both amylose and amylopectin. This breaks the long-chain starch molecules into short-chain dextrins. The short-chain dextrins are more suitable for later saccharification to fermentable sugars such as glucose or maltose.
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