The influence of proteolytic and cytolytic enzymes on starch degradation during mashing

Abstract

The objective of this research was to investigate the impact of proteolysis and cytolysis on starch degradation over the course of the mashing process. A proteolytic enzyme (Neutrase 0.8L, Novozymes) and a number of cytolytic enzymes (barley β-glucanase from Megazyme, Shearzyme 500L and Ultraflo Max from Novozymes) were used to test their efficiency on starch degradation during mashing. The proteolytic and cytolytic enzymes had positive effects on the levels of starch-degrading enzymes and starch solubilization during mashing, resulting in higher levels of wort sugar compared with the control, indicating that proteins and residual non-starchy polysaccharides limited the digestibility of starch during mashing. Moreover, the proteolytic enzyme showed a significantly greater improvement than the cytolytic enzymes, yielding a 57% increase in β-amylase, a 173% increase in limit dextrinase, rapid starch solubilization during mashing and a higher percentage of fermentable sugars in resultant wort. The increases in limit dextrinase and β-amylase promoted by the protease suggest that sufficient proteinaceous inhibitor existed in the wort during mashing to inhibit their activities, leading to the unavailability of β-amylase and especially limiting dextrinase. Furthermore, Ultraflo Max, which contained a β-glucanase–xylanase mixture, showed a greater improvement than either the individual β-glucanase or the xylanase on starch hydrolysis. These findings suggest that β-glucanase is the major enzyme responsible for the degradation of cell walls, and that the complete hydrolysis of the residual cell walls depends on the synergistic effect of β-glucanase and xylanase. The results suggest that brewers should adjust the degradation of the cell walls and correct the degree of protein modification in order to obtain the desired wort composition. Copyright © 2014 The Institute of Brewing & Distilling