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Comparisons of amylolytic enzyme activities and ß-amylases with differing Bmy1 intron III alleles to sugar production during congress mashing with North American barley cultivars

Henson, Cynthia A., Duke, Stanley H., Vinje, Marcus A.
Journal of American Society of Brewing Chemists 2012 v.70 no.4 pp. 230
alleles, alpha-amylase, barley, beta-amylase, cultivars, enzyme activity, glucose, introns, limit dextrinase, malt, malting barley, maltodextrins, maltotriose, mashing, North America
This study was conducted to determine the relationships between patterns of activity development of malt amylolytic enzymes (a-amylase, ß-amylase, and limit dextrinase) and sugar production in two- and six-row North American cultivars during the course of Congress mashing and to test two hypotheses: 1) that rates of increase in and maximal activity of ß-amylase in the initial phases of mashing would correlate better than the other amylolytic enzymes with sugar production and 2) that ß-amylase intron III allelic variation would have little to no association on sugar production during mashing. Malts of twelve barley cultivars were mashed in a micro-masher and aliquots removed for amylolytic enzyme activity and sugar assays at 6 time points during the 115 min mashing regime. Peak activities of ß-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) at the time of peak activity. In contrast, with the same comparisons, there were no significant correlations with wort total sugars for a-amylase and limit dextrinase and only a-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 ß-amylase activity from 5 min to maximal activity versus 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 a-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. Cultivars producing the highest levels of total wort sugars early in mashing, when the bulk of total sugars are produced or at the end of mashing as determined by LSD analysis had both the Bmy1.a (1st 30 min, Legacy, Tradition; end of mashing, Legacy, Pinnacle, Tradition) and Bmy1.b (1st 30 min, Harrington; end of mashing, Harrington, Merit) intron III alleles. This study supports both of the proposed hypotheses.