Improved Prediction of Malt Fermentability by Measurement of the Diastatic Power Enzymes, β-Amylase, α-Amylase, and Limit Dextrinase: II. Impact of Barley Genetics, Growing Environment and Gibberellin on Levels of α-Amylase and Limit Dextinase in Malt

The determination of the levels of the diastatic power enzymes (DPEs) β-amylase, limit dextrinase, and α-amylase has previously been shown to predict barley malt fermentability. Using micromalted samples of barley from different genotypes and growing environments, it was demonstrated that both these factors were important in determining the level of DPEs in malt. In terms of genotypic effects, a trial of breeders' lines and varieties showed substantial variation in the levels of total β-amylase (means 455-914 U/g), total limit dextrinase (means 268-603 U/kg), and α-amylase (means 154-316 U/g). The application of gibberellin (GA) during malting resulted in substantial increases in the levels of total limit dextrinase and α-amylase and the extent of modification (KI). However, the level of total β-amylase was relatively unchanged. It was also observed that the levels of total limit dextrinase and α-amylase and extent of KI generally were highly correlated (r » 0.6-0.7), which was attributed to the sensitivity of each of these malt quality factors to GA. The results are discussed in terms of their practical importance to barley breeders and maltsters seeking to supply malt that satisfies the malt fermentability requirements of their brewing customers.