Evaluation of malting properties and activities of three enzymes from sorghum (Sorghum bicolor) during malting

Abstract

Sorghum (Sorghum bicolor (L) Moench), is used as human food such as bread, malt drinks and beers; as livestock feed, renewable energy source such as bioethanol. The experimental monitoring of enzyme activity during malting permits the detection of germination-specific genes. The products of α- amylase (simple sugars), β-amylase (maltose), protease (free amino nitrogen) and polyphenol oxidase (quinone), combined during kilning and mashing, with the development of characteristics flavor and coloured malt. In this study, we investigate malting properties of white and yellow varieties of sorghum while the variation in the activity of the three enzymes namely polyphenol oxidases, amylases and proteases, were monitored as the malting progresses. The result obtained were 95% and 86% germinative energy, 1.49 g and 1.09 g water absorption, 0.751 mg/ml and 0.639 mg/ml crude protein for yellow and white sorghum respectively. The activity of the three enzymes was higher in dormant yellow sorghum than dormant white sorghum. For both varieties, polyphenol oxidase activities were lowest during steeping than in dormant grain, while the highest activities were obtained during germination. Amylases activity did not changed significantly from dormant to germination. The proteases activities were highest during steeping than in dormant while gradually decreased to zero level during germination.