Carbohydrates in Malting and Brewing: Vii. Complex Carbohydrates of Infusion Wort and Their Enzymic Degradation

Abstract

The dextrins of infusion wort were separated into five fractions of increasing complexity of structure by successive precipitations by means of acetone and ethanol and by dialysis. The first fraction contained dextrins averaging four glucose units in chain‐length while fraction 2 had an average chain‐length of 13 and the less soluble fractions were still more complex and were contaminated with pentosans. The various groups of dextrins were all hydrolysed to a considerable extent by β‐amylase except in the case of fractions 2 and 3 where the degree of degradation was only about 20%. These fractions were of highly branched structures as confirmed by their yielding much isomaltose on partial hydrolysis with acid. Although the dextrins are incompletely degraded by α‐ and β‐amylase under normal brewing conditions, enzyme preparations from moulds and even from malt were able to degrade all fractions almost completely under certain circumstances to mono‐, di‐, and trisaccharides. The alcohol‐soluble carbohydrates from infusion wort contained small amounts of isomaltose and panose and the pentoses xylose, arabinose and ribose in addition to the major components previously noted.