J. Am. Soc. Brew. Chem. 70(1):10-28, 2012 This study was conducted to test three hypotheses: 1) that alpha-amylase will have less consistent patterns of activity during mashing than will beta-amylase and limit dextrinase; 2) that differing beta-amylase 1 intron III alleles (Bmy1.a and Bmy1.b) would not be useful in predicting high or low activities or thermostabilities among cultivars; and 3) that correlations of alpha-amylase versus beta-amylase activities would be more significant than for either amylase versus limit dextrinase during the initial 55 min of mashing, when the bulk of wort sugars are produced. Malts of six two-row and six six-row barley cultivars were mashed, and amylolytic enzymes were assayed at six time points during mashing. alpha-Amylase activities of four cultivars peaked at 30 min (45 degrees C), six at 55 min (70 degrees C), and two at 75 min (70 degrees C). beta-Amylase activities of all cultivars peaked sharply at 30 min (45 degrees C) into mashing and declined precipitously thereafter, rapidly approaching near nil by 75 min. Limit dextrinase activities of 11 of 12 cultivars peaked at 55 min (70 degrees C), and one peaked at 30 min (45 degrees C). These data indicate no uniform pattern for the development of alpha-amylase activity compared with patterns for beta-amylase and limit dextrinase during mashing. Steptoe, a feed barley cultivar, had much lower peak activities for all three amylolytic enzymes than did malting cultivars. The highest beta-amylase activities during mashing of cultivars with either the Bmy1.a (Legacy, Lacey, and Morex) or Bmy1.b) (Merit and Harrington) intron III alleles were not significantly different as determined by least significant difference (LSD) analysis (P < 0.0001). As temperatures increased from 45 to 70 degrees C (55 min). percentages of the highest beta-amylase activities decreased from 11.9% (Rasmusson) to 41.5% (Steptoe). LSD analysis revealed that Steptoe (Bmy1.a allele) had significantly higher beta-amylase thermostability than did malting cultivars. The highest malting barley thermostabilities for beta-amylases (Lacey [Bmy1.a allele] and Harrington [Bmy1.b allele]) were not significantly different (P < 0.0001). Correlations of alpha-amylase versus beta-amylase activities were positive and significant in seven of nine possible correlations from 5 to 55 min of mashing, whereas alpha-amylase and beta-amylase versus limit dextrinase activity correlations over the same period were significant in two of nine and one of nine correlations, respectively. This study supports all three of the proposed hypotheses.
