|Duke, Stanley - UNIV OF WISCONSON|
Submitted to: Journal of American Society of Brewing Chemists
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: July 12, 2007
Publication Date: January 1, 2008
Citation: Henson, C.A., Duke, S.H. 2008. A comparison of standard and nonstandard measures of malt quality. Journal of American Society of Brewing Chemists. 66(1):11-19. Interpretive Summary: Brewers impose rigorous criteria in assessing malt quality and this is reflected in the premium price that is paid to the barley growers. Typically, anywhere from eight to 15 different tests are conducted and the results for each parameter must fit within the narrow ranges that are acceptable to brewers. In spite of the narrow range of acceptable results and of the rigorous testing there are still processing performance differences between malts that have been judged as acceptable for malting purposes. This study identified combinations of traits that collectively result in some elite malting barley cultivars underperforming other elite malting barley cultivars. The impact of this work is that breeders now have several new traits they can breed for brewers that are new measures of malt quality that can ultimately result in improved cultivars of malting barley.
Technical Abstract: The objectives of this study were to determine if six highly elite malting barley cultivars could be distinguished from each other by using univariate and multivariate statistics to analyze nine standard and 22 nonstandard measures of malting quality. Simple linear regression revealed cultivar differences in activities of alpha-glucosidase and in the thermostabilities of alpha-amylase, beta-amylase and limit dextrinase that were correlated with differences in wort osmolyte concentrations. This method also identified cultivar differences in the thermostabilities of alpha-amylase, beta-amylase and limit dextrinase that were correlated with differences in diastatic power. Results from principal component analysis (PCA) of the non-standard measures of malting quality were considered to be better than the results of PCA of the standard malting quality parameters because the former was able to categorize the six-row cultivar and the two-row cultivar with the lowest real degree of fermentation, an important measure of brewhouse performance, as being different from the other two- and six-row malts. The malt quality traits that distinguished the two lowest performing of these six elite malting barleys from the other malts were activities of alpha-glucosidase, limit dextrinase and alpha-amylase, which were lower in these two malts, plus the thermostabilities of alpha-amylase, beta-amylase and limit dextrinase and in wort osmolyte concentrations, which were higher in these two cultivars.