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Thermostability of Barley Malt Proteases in Western Canadian Two-Row Malting Barley

¹Department of Plant Sciences, University of Saskatchewan, 51 Campus Drive, Saskatoon, SK, S7N 5A8 Canada. ²Corresponding author. Phone: (306) 966-5004. Fax: (306) 966-5015. E-mail: masood.rizvi@usask.ca

During the malting process, barley is germinated via a carefully controlled procedure so that its components are degraded to sugars, amino acids, and other low molecular weight compounds that can be used for subsequent fermentation. One of the most important of these processes is the hydrolysis of proteins into peptides and amino acids. During seed germination, proteases hydrolyze insoluble reserve proteins into soluble peptides that are subsequently hydrolyzed into free amino acids. During kilning, green malt is initially air dried at 40–60°C, and then the temperature is gradually increased to 85–95°C. Although most proteases are denatured during kilning, the malt contains a small proportion of heat-stable protease enzymes able to further break down protein in the subsequent mashing process. In this study, protocols were developed and standardized to measure the activity of different proteases. These protocols were then used to study protease thermostability in Canadian two-row spring malting barley lines. We found a wide range in protease activity under controlled conditions. Upon heat treatment, several lines exhibited significant protease thermostability. These thermostable enzymes were purified by ammonium sulfate precipitation and Sephadex columns for further study.