A key biochemical process in brewing is the hydrolysis of starch by DP enzymes into yeast fermentable sugars during the mashing stage of brewing. Efficient starch hydrolysis during mashing requires starch gelatinization at ~62-64°C, along with sufficient DP enzyme activity to achieve starch hydrolysis. This investigation considers the release of yeast fermentable sugars in parallel with the activity of the DP enzymes during an IoB 65°C (1:3 grist:water + Ca), with a conventional Congress (1:4 grist:water) small scale mash, using malt from three current Australian varieties. Traditionally, it is recognized with the DP enzymes, that a-amylase is relatively thermostable while beta-amylase and limit dextrinase are relatively thermolabile at conventional mashing temperatures. In addition, beta-amylase, and in particular limit dextrinase, have bound and latent fractions that require release from inhibitors or binding proteins before they are able to contribute to starch hydrolysis. One mechanism appears to be that the heat applied during mashing at temperatures around 65°C liberates these enzymes. Of similar importance is the structure of starch which determines the temperature of gelatinization. In addition, starch branching and chain length are important to the efficiency of hydrolysis by the DP enzymes. The results in terms of starch characteristics, DP enzyme release, thermostability and activity is examined to understand the relative contribution of the DP enzymes to fermentable sugar production in the mash. This understanding will have significant implications for the choice of small scale mash protocol for malt quality evaluation, the targeting of DP enzyme alleles for barley malt quality improvement and the selection of malt for brewing.
Evan Evans commenced malt quality and brewing research at University of Adelaide in 1992. Between 2002 and 2013 he relocated to the University of Tasmania working towards improving malt quality to improve beer quality and the efficiency of the brewing process. In 2013, Dr Evans started the Tassie Beer Dr Consultancy. Dr Evans is currently serving on the IBD Awards Committee and is a member of the editorial board for the Journal of the ASBC. In 2005, Dr Evans was made a Fellow of the Institute of Brewing and Distilling.