Comparisons of Amylolytic Enzyme Activities and β-Amylases with Differing Bmy1 Intron III Alleles to Sugar Production during Congress Mashing with North American Barley Cultivars

Abstract

This study was conducted to determine the relationships between patterns of activity of malt amylolytic enzymes (α-amylase, β-amylase, and limit dextrinase) and sugar production in two- and six-row North American cultivars over the course of Congress mashing and to test two hypotheses: 1) that maximal activity of and rates of increase in β-amylase activity during the initial phases of mashing would correlate better than the other amylolytic enzymes with sugar production and 2) that β-amylase intron III allelic variation would have little to no association with sugar production during mashing. Malts of twelve barley cultivars were mashed in a micro-masher and assayed for amylolytic enzyme activities and sugar levels at 6 time points during the 115 min mashing regime. Peak activities of β-amylase were positively and significantly correlated with wort total sugars (r = 0.704, P = 0.011), glucose (r = 0.654, P = 0.021), and maltose (r = 0.780, P = 0.003) and negatively and significantly correlated with maltotetraose (r = −0.830, P = 0.001) and maltopentaose (r = −0.767, P = 0.004). In contrast, with the same comparisons, there were no significant correlations with wort total sugars for α-amylase and limit dextrinase and only α-amylase significantly correlated with some individual sugars (glucose, r = 0.611, P = 0.035; maltotriose, r = 0.594, P = 0.042; maltotetraose, r = −0.772, P = 0.003; maltopentaose, r = −0.728, P = 0.007). Correlations of rates of change in β-amylase activity from five min to the time of maximal activity versus rates of change in total sugars and individual sugars revealed positive and significant correlations with wort total sugars (r = 0.794, P = 0.002), maltose (r = 0.851, P = 0.0004), and maltotriose (r = 0.605, P = 0.038) and significantly negatively correlated with maltotetraose (r = −0.663, P = 0.019) and maltopentaose (r = −0.677, P = 0.016). In contrast, with the same comparisons, there were no significant correlations with wort total sugars or individual sugars versus α-amylase or limit dextrinase. Least significant difference (LSD) analysis revealed that there was no consistent pattern in total wort sugars and the most and least abundant wort sugars and maltodextrins produced during mashing amongst cultivars with Bmy1.a or Bmy1.b intron III alleles. There were no significant differences in cultivars with Bmy1.a or Bmy1.b intron III alleles producing the highest levels of total wort sugars early in mashing, when the bulk of total sugars are produced, (1st 30 min: Bmy1.a [Legacy, Tradition]; Bmy1.b [Harrington]) and at the end of mashing (Bmy1.a [Legacy, Pinnacle, Tradition]; Bmy1.b [Harrington, Merit]). This study supports both of the proposed hypotheses.