Dextrins are polymers of glucose molecules formed during the degradation of starch in the mashing process. The starch comprises amylose, a straight-chain polymer of glucose linked alpha 1,4, and amylopectin, a branched glucose polymer with alpha 1,4 links in the chain and alpha 1,6 links at the branch points. Starch is derived predominantly from malted barley, although other cereal sources (adjuncts) can also contribute. During the mashing process a series of malt enzymes, notably alpha and beta amylases, break down the starch polymers into smaller units comprising several glucose molecules, which may be arranged either straight chain or in a branch formation. These glucose polymers can be further degraded into much smaller units comprising glucose (a single glucose molecule), maltose (two glucose molecules), and maltotriose (three glucose molecules), which can be utilized by the brewing yeast in fermentation. However, depending on the extent of the enzyme activity, some of the glucose polymers do not degrade completely and are carried forward into the wort. These polymers, which can account for a notable percentage of the total extract, are unable to be fermented by the yeast and remain in the beer at the end of fermentation. In some beers, notably “low-calorie” or “lite” beers, the residual nonfermentable dextrins in the wort are reduced to lower levels through the addition of extraneous enzymes or prolonged mash periods. At high levels residual dextrins can impact the “body” or “mouthfeel” in beers, although they have no flavor of their own. Brewers wishing higher dextrin content in their beers can achieve this through the use of higher mash saccharification temperatures or using dextrin-rich types of caramel or crystal malts as a proportion of the grist.
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