Evaluation of Indigenous Botswana Sorghum Cultivars with Respect to Their Diastatic Power, α-Amylase, β-Amylase, and Limit Dextrinase Potentials for Malting

Abstract

The malting quality of 11 Botswana sorghum cultivars was assessed using their diastatic power (DP), α-amylase, β-amylase, and limit dextrinase (LD) potentials as parameters. Malt DP and LD were assayed using soluble starch and Limit-Dextrizyme methods, respectively. Malt α- and β-amylase activities were assayed specifically with Ceralpha and Betamyl, respectively, then nonspecifically with a diamylase method in which β-amylase activity is denatured by heating (70°C, 15 min). All malt quality parameters varied significantly (P < 0.001) by grain cultivar. Malt DP, α-amylase, and β-amylase fell within ranges previously reported for industrial sorghum malts. β-Amylase was the principal amylase component of DP in BSH1, Lekgeberwa, SNK, Kanye Standard, Marupantshi, and Mafia at 55, 68, 71, 72, 75, and 88%, respectively. Malt LD was high at 101 (Mafia) to 231 U (Sefofu). For α- and β-amylase, values obtained using both specific assay methods correlated strongly (R2 = 0.94, P < 0.001 for α-amylase; R2 = 0.95, P < 0.001 for β-amylase) with results from the diamylase protocol. The results highlight the need to screen more cultivars for brewing properties. Segao, Lekgeberwa, Sefofu, Town, and Kanye Standard displayed desirable amylolytic properties, suggesting their potential use in the production of lager beer-quality sorghum malts.