Enzyme Activities Shape Malting Quality Standards

Malting quality of barley is a complex characteristic, which is influenced by a combination of interacting traits that are regulated by various genetic and environmental factors. The activities of various enzymes play pivotal roles in determining the malting quality, as they drive the biochemical processes responsible for converting barley saccharides and proteins into fermentable sugars and amino acids during the malting process. In this study, 14 malting barley cultivars were used to investigate the relationship between enzyme activities and malting quality traits. The results revealed a significant correlation between α-amylase activity and malt extract (MEX), viscosity (VIS), free α-amino nitrogen (FAN), and Kolbach index (KI). In contrast, β-amylase activity exhibited a significant correlation solely with diastatic power (DP). β-glucanase activity was significantly correlated with FAN and KI. The elevated expression levels of both <i>HvBmy1</i> and <i>HvBmy2</i> contributed to high DP, and the activation of α-amylase genes (<i>HvAmy1</i> and <i>HvAmy2</i>) and β-glucanase genes (<i>HvGlb1</i> and <i>HvGlb2</i>) played a crucial role in producing high FAN and KI. These results enhance our understanding of the relations between enzyme activity and malting quality traits and thereby may facilitate further breeding for malt barley cultivars.