The unfermentable fraction of extract accounts for approximately 25% of the total carbohydrate in worts. This is usually referred to as dextrin, but, as Enevoldsen (1974) points out, it contains small quantities of monosaccharides such as arabinose, xylose and ribose, the disaccharide isomaltose, trisaccharides such as panose and iosopanose and p-glucans. Thus, true dextrins, containing four or more glucose units, comprise approximately 90% of the residual carbohydrate in beer. Some 40-50% of the dextrins are oligosaccharides containing 4-9 glucose units, the remaining 50-60% are higher dextrins with 10 or more glucose units. Enevoldsen and Schmidt (1974) demonstrated that the concentration and spectrum of dextrins in worts and beers were identical. Furthermore, they also observed that the concentrations of individual dextrins for all worts and beers examined showed a characteristic pattern of peaks and troughs (Table 2.5 and Fig. 2.14). Dextrins containing four glucose units are always the most abundant dextrin, and regular peaks occur separated by approximately 4-5 glucose units.
Dextrins are derived from starch of the malt endosperm and therefore they may be linear glucose polymers joined by a-(l ->4) linkages or branched molecules containing
Table 2.4 Fermentable sugar contents of worts produced by the procedures indicated (data abstracted from Hoekstra, 1974).
Origin of brewery (fermentation)
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