FACTORS INFLUENCING BETA-AMYLASE ACTIVITY IN SORGHUM MALT

Abstract

An investigation into factors influencing beta-amylase activity in sorghum malt confirmed that ungerminated sorghum grain exhibited essentially no beta-amylase activity. Malted sorghum had beta-amylase activity less than 25% of the level in barley malt. Neither reducing agents nor papain affected beta-amylase activity in sorghum, indicating that the enzyme is not in a bound form, unlike in barley. Isoelectric focusing indicated that sorghum beta-amylase comprises just one major and one minor isozyme of pl approximately 4.4–4.5, unlike the many isozymes all of higher pl in barley. However, like barley, sorghum beta-amylase was more temperature-labile than its alpha-amylase. Beta-amylase activity in sorghum malt was increased by germination time, high germination moisture and over the germination temperature range investigated (24–32°C), 24°C gave the highest activity. The beta-amylase activity of sorghum malts was significantly correlated with malt diastatic power, despite the fact that alpha-amylase and not beta-amylase is the predominant diastatic enzyme in sorghum malt.