In the barley seed, its mobilization is induced in order to digest the starch reserves in the endosperm and provide nutrients for the growing seed. The alpha amylase used in the mash comes from the malt, where it is entirely produced in the aleurone layer during malting. The parts of the starch molecule containing these side bonds form the basis of the important unfermentable dextrins produced by mashing. The major limitation to this digestion is the side bonds of starch amylopectin, which are not digested by either alpha or beta amylase. Beta amylase further digests these intermediate molecules mostly into maltose-a sugar of two glucose units-but also to glucose itself and to the three-glucose molecule maltotriose. As a result it opens up the starch molecule, breaking it into a range of intermediate sizes. Alpha amylase contributes to the digestion of starch by breaking internal bonds between glucose molecules. See dextrins.Ī starch molecule is, in essence, a group of glucose molecules linked together. Dextrins contribute strongly to this and give beer a major part of its character. Unlike wine, where virtually all of the sugars are fermented, beer is distinct in having residual sugars to provide sweetness, body, and mouthfeel. Ideally these should be a suitable balance of simple fermentable sugars-glucose, maltose, and maltotriose-and larger unfermentable dextrins roughly in a 3:1 proportion. To focus on the use of alpha amylase in brewing, it is necessary to look at the needs of a successful mash, in particular the spectrum of sugars required in the final wort.
Alpha amylase is an endo enzyme mainly digesting the alpha 1–4 bonds of starch at points within the chain, not at the ends. Together these two amylases produce the spectrum of wort sugars essential in the production of a beer. It digests starch, a large polymer of glucose, into smaller units, exposing it to further digestion by beta amylase. Alpha Amylase is a major mash enzyme of critical concern to brewers in their production of fermentable wort.