DEXTRINS IN BREWING

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Abstract
The dextrins in beer exhibit a characteristic wavy distribution with respect to their molecular weight, so that these dextrins seem to fall into distinct groups. These groups of dextrins (I, II, III and IV corresponding to DP 5–10, DP 11–16, DP 17–21 and DP 22–27) have been isolated by gel-chromatography on Bio-Gel P-2. Debranching of the megalosaccharides in Groups II, III and IV by means of pullulanase shows that they contain two, three and four α-1,6 linkages respectively. The dextrins in Group I are either linear or singly-branched. The distribution patterns of the constituent, linear maltosaccharides have been determined and some likely structures for the multiply-branched dextrins are suggested. The results indicate that the majority of the α-1,6 linkages in amylopectin survive the brewing process; 25% of the α-1,6 linkages show up as singly-branched oligosaccharides and at least 35% as multiply-branched megalosaccharides of DP 11–30. With respect to the fine structure of amylopectin, the implication is that although the average interior chain length is about 6 glucose units, at least 35% of the α-1,6 linkages occur in densely branched clusters (pairs, triplets, quadruplets, etc.), the interior chain length of which is about 3 glucose units. This in turn offers an explanation of the wavy distribution of the dextrins in wort and beer.