VIEW ARTICLE    doi:10.1094/ASBCJ-2007-1210-01

A Comparison of Standard and Nonstandard Measures of Malt Quality (1). Cynthia A. Henson (2), United States Department of Agriculture–Agricultural Research Service Cereal Crops Research Unit, Madison, WI, and Department of Agronomy, University of Wisconsin-Madison, Madison, WI; and Stanley H. Duke, Department of Agronomy, University of Wisconsin-Madison, Madison, WI. (1) Mention of a proprietary product does not constitute a guarantee or warranty of the product by the United States Department of Agriculture and does not imply its approval to the exclusion of other suitable products. (2) Corresponding author. E-mail: <cahenson@wisc.edu>; Phone: +1.608.262.0377; Fax: +1.608.890.0306. This article is in the public domain and not copyrightable. It may be freely reprinted with customary crediting of the source. American Society of Brewing Chemists, Inc., 2008. J. Am. Soc. Brew. Chem. 66(1):11-19, 2008.

The objectives of this study were to compare standard and nonstandard measures of malting quality using simple correlations and to determine whether six highly elite malting barley cultivars could be distinguished from each other using multivariate statistics to analyze 9 standard and 22 nonstandard measures of malting quality. Simple linear regression revealed cultivar differences in the thermostabilities of alpha-amylase, beta-amylase, limit dextrinase, and alpha-glucosidase that were positively correlated with differences in wort osmolyte concentrations (r = 0.853–0.958, P < 0.05–0.01) and differences in the thermostabilities of alpha-amylase, beta-amylase, and limit dextrinase that were correlated with diastatic power (r = 0.872–0.937, P < 0.05–0.01). Principal component analysis (PCA) of the nonstandard measures of malting quality were considered more useful than PCA of the standard measures because the former was able to categorize the six-row cultivar and 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 the six elite malting barleys from the other malts were alpha-glucosidase, limit dextrinase, and alpha-amylase activities, which were lower in these two malts, plus the thermostabilities of alpha-amylase, beta-amylase, and limit dextrinase and wort osmolyte concentrations, which were higher in these two malts. Keywords: alpha-Amylase, beta-Amylase, Enzyme thermostability, alpha-Glucosidase, Limit dextrinase, Osmolyte concentration

Los objetivos de este estudio fue comparar las medidas estándar y no estándar de la calidad maltera usando correlaciones simples y determinando si seis altamente elite cultivares de cebada maltera se podían distinguir unos de otros usando las estadísticas multivariado para el análisis de 9 estándar y 22 no estándar medidas de la calidad maltera. Regresión lineal simple reveló diferencias entre los cultivars en la termoestabilidad de alfa-amilasa, beta-amilasa, dextrinasa límite, y alfa-glucosidasa que se correlacionó positivamente con las diferencias en las concentraciones de osmolitos en el mosto (r = 0.853–0.958, P < 0.05–0.01) y las diferencias en la termoestabilidades de alfa-amilasa, beta-amilasa, y dextrinasa límite que se correlacionaron con el poder diastástico (r = 0.872–0.937, P < 0.05–0.01). Análisis de componentes principales (PCA) de las medidas no estándar de la calidad maltera se considera más útil que el PCA de las medidas estándar, porque la primera era capaz de clasificar los cultivares de maltas de seis-carreras y dos-carreras con el más bajo RDF, una medida importante del rendimiento de la sala de cocción, de ser diferente de las otras maltas de dos-carreras y seis-carreras. Las características de calidad de malta que distinguen los dos más bajo nivel de rendimiento de las maltas de seis-carreras de las otras maltas fueron alfa-glucosidasa, dextrinasa límite, y las actividades de la alfa-amilasa, que fueron inferiores en estos dos maltas, además de la termoestabilidades de alfa-amilasa, beta-amilasa, y dextrinasa límite y concentraciones de osmolitos en el mosto, que fueron mayores en estos dos maltas. Palabras claves: alfa-Amilasa, beta-Amilasa, Concentración de osmolitos, Dextrinasa límite, alfa-Glucosidase, Termoestabilidad de los enzimas