Improved Prediction of Malt Fermentability by Measurement of the Diastatic Power Enzymes beta-Amylase, alpha-Amylase, and Limit Dextrinase: II. Impact of Barley Genetics, Growing Environment, and Gibberellin on Levels of alpha-Amylase and Limit Dextrinase in Malt. D. Evan Evans (1), Tasmanian Institute of Agricultural Research, University of Tasmania, Hobart, TAS, Australia; Chengdao Li and Stefan Harasymow, Department of Agriculture and Food Western Australia, South Perth, WA, Australia; and Sophia Roumeliotis and Jason K. Eglinton, School of Agriculture, Food and Wine, University of Adelaide, Glen Osmond, SA, Australia. (1) Corresponding author. E-mail: eevans@utas.edu.au; Phone: +61-(0)3-6226-2638; Fax: +61-(0)3-6226-2642. J. Am. Soc. Brew. Chem. 67(1):14-22, 2009.

The determination of the levels of the diastatic power enzymes (DPEs) beta-amylase, limit dextrinase, and alpha-amylase has previously been shown to predict barley malt fermentability. Using micromalted samples of barley from different genotypes and growing environments, it was demonstrated that both these factors were important in determining the level of DPEs in malt. In terms of genotypic effects, a trial of breeders’ lines and varieties showed substantial variation in the levels of total beta-amylase (means 455–914 U/g), total limit dextrinase (means 268–603 U/kg), and alpha-amylase (means 154–316 U/g). The application of gibberellin (GA) during malting resulted in substantial increases in the levels of total limit dextrinase and alpha-amylase and the extent of modification (KI). However, the level of total beta-amylase was relatively unchanged. It was also observed that the levels of total limit dextrinase and alpha-amylase and extent of KI generally were highly correlated (r ≈ 0.6–0.7), which was attributed to the sensitivity of each of these malt quality factors to GA. The results are discussed in terms of their practical importance to barley breeders and maltsters seeking to supply malt that satisfies the malt fermentability requirements of their brewing customers. Keywords: alpha-Amylase, beta-Amylase, Barley genetics, Gibberellin, Limit dextrinase, Malt fermentability

La determinación de los niveles de las enzimas de poder diastástico (DPEs) beta-amilasa, dextrinasa límite, y alfa-amilasa ha sido demostrado para predecir la potencial de fermentación de la malta. Uso de muestras de una micromaltaje de cebada de diferentes genotipos y entornos crecientes, se demostró que ambos factores son importantes para determinar el nivel de DPEs en malta. En términos de efectos genotípica, un experimento de las líneas de los criadores y variedades mostraron variación sustancial en los niveles del total de beta-amilasa (medios 455–914 U/g), total dextrinasa límite (medios 268–603 U/kg), y alfa-amilasa (medios 154–316 U/g). La aplicación de giberelinas (GA) durante el malteado dio lugar a aumentos sustanciales en los niveles de total dextrinasa límite y alfa-amilasa y el alcance de modificación (KI). Sin embargo, el nivel total de beta-amilasa fue relativamente sin cambios. También se observó que los niveles de total dextrinasa límite y alfa-amilasa y la extensión de KI en general fueron altamente correlacionados (r ≈ 0.6–0.7), que se atribuyó a la sensibilidad de cada uno de estos factores de calidad de malta a GA. Los resultados se discuten en términos de su importancia práctica para los criadores de cebada y malteadors tratando de suministro de malta que satisfaga los requisitos de potencial de fermentación de la malta para sus clientes. Palabras claves: alfa-Amilasa, beta-Amilasa, Dextrinasa límite, Genética de cebada, Giberelina, Potencial de fermentación de malta