Although most beers contain glucose and fructose only in trace quantities (if at all), a few brands, especially low calorie lagers, do contain significant concentrations of one or both. This appears to be associated with the use of amyloglucosidase to break certain nonfermentable sugars remaining in wort down to their fermentable components, thus reducing the carbohydrate content remaining after fermentation. Glucose consists of two anomers, termed alpha and beta pyranose respectively, and while the alpha anomer is preferred by the yeast it is the beta anomer which is mainly formed by amyloglucosidase. Since high glucose concentrations inhibit the fermentation of fructose, the latter sugar also tends to remain behind. This is particularly the case when the enzyme is added to the wort in the fermenting vessel. The two sugars can also be found in other beers, in this case as a result of the action of invertase (produced by yeast) on fructan, a barley polysaccharide composed of glucose and fructose molecules, residual amounts of which can survive malting and mashing. Invertase can also be found in commercial amyloglucosidase preparations.
Keywords : amyloglucosidase beer composition fermentation fructose glucose invertase residue