PHYSIOLOGICAL, BIOCHEMICAL AND GENETIC REGULATION OF CARBOHYDRATE METABOLISM IN CEREAL TISSUES
Location: Cereal Crops Research
Title: A Comparison of Barley Malt Amylolytic Enzyme Activities and Malt Sugar Concentrations
Submitted to: North American Barley Research Workshop Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: August 18, 2008
Publication Date: October 26, 2008
Citation: Duke, S.H. and Henson, C.A. 2008. A Comparison of Barley Malt Amylolytic Enzyme Activities and Malt Sugar Concentrations. In: North American Barley Researchers Workshop Proceedings, October 26-29, 2008, Madison, Wisconsin. p. 28.
This study was conducted to test the hypothesis that barley malt alpha-amylase activity would correlate better with malt sugar concentrations than the activities of beta-amylase, or limit dextrinase. Seeds of four two-row and four six-row North American elite barley cultivars were steeped and germinated in a micromalter for 6 days. At 24h intervals throughout germination, green malt was removed and kilned. Malts were assayed for individual amylolytic activities and malt sugars were extracted and assayed. Increases in malt alpha- and beta-amylase and limit dextrinase activities were greatest between day 1 and day 2 of germination. Over all days of germination, for all cultivars combined, malt alpha-amylase activities correlated much better with total sugar concentrations (r=0.830, P<0.0001) than beta-amylase activities (r=0.665, P<0.0001), and somewhat better than limit dextrinase activities (r=0.785, P<0.0001). Correlations of individual sugar concentrations (glucose, maltose, sucrose, fructose, and the maltodextrins maltotriose through maltoheptaose) for all cultivars combined over all days of germination were greater with alpha-amylase activities than with beta-amylase or limit dextrinase activities (e.g. glucose and maltose r value, respectively: alpha-amylase, r=0.872, P<0.0001, r=0.763, P<0.0001; beta-amylase, P=0.587, P<0.0001, r=0.679, P<0.0001; and limit dextrinase, r=0.806, P<0.0001, r=0.733, P<0.0001). Over all days of germination, individual cultivar malt alpha-amylase activities correlated better with total sugar concentrations (low to high, r=0.738, P<0.0001 [Harrington] to r=0.925, P<0.0001 [Legacy]) than beta-amylase activities (low to high, r=0.446, P=0.064 Harrington] to r=0.891, P<0.0001 [Legacy]) or limit dextrinase activities (low to high, r=0.577, P=0.012 [Harrington] to r=0.867, P<0.0001 [Lacey]). Correlations of individual sugar concentrations for individual cultivars over all days of germination, for the most part, were greater with alpha-amylase activities than with beta-amylase or limit dextrinase activities (e. g. low to high r values for glucose: alpha-amylase, r=0.791, P<0.0001 [Garnet] to r=0.901, P<0.0001 [B1202]; beta-amylase, r=0.619. P=0.0008 [B1202] to r=0.849, P<0.0001 [Garnet]; limit dextrinase, r=0.763, P=0.0002 [Harrington] to r=0.890, P<0.0001 [Merit]). Overall, malt alpha-amylase activity correlated better with sugar production during malting and a short period of mashing than other malt amylolytic enzymes, supporting the tested hypothesis.