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. 1993 The Institute of Brewing & Distilling