Assessing the Impact of the Level of Diastatic Power Enzymes and Their Thermostability on the Hydrolysis of Starch During Wort Production to Predict Malt Fermentability

摘要

In this study, commercially produced malts were used for small-scale simulated mashing trials to investigate the impact of differences in the level and thermostability of malt diastatic power (DP) enzymes on the resultant wort fermentability. A modified European Brewery Convention/ American Society Brewing Chemists mashing protocol was used with mash-in temperatures ranging between 45 and 76℃ for full-malt and 30% rice adjunct mashes. Malt extract yield varied little with mashing temperature for most varieties in this temperature range. However, the fermentability, maltose content, and free amino nitrogen of that extract was considerably affected by mashing temperature with 65℃ achieving the highest fermentability for all malt varieties. Multilinear regression analysis of full-malt and rice adjunct mashing trials at 65℃ using 43 commercial malts showed that the level of α-amylase and total limit dextrinase activity, Kolbach Index, and the total β-amylase activity level and thermostability were the most important malt quality predictors of wort fermentability. These conclusions suggest that the conventional DP assessment could be replaced with the measurement of its component enzymes outlined above so that maltsters could better satisfy brewers malt quality expectations by blending and defining their malt quality in terms of these fermentability predicting factors. This information would be particularly useful to brewers who brew with multiple varieties and blends from different suppliers. The focus on individual enzyme characteristics by barley breeders is likely to provide selection targets that are more accurate and achievable.%En este estudio, maltas de producción comercial fueron utilizadas en pruebas de escala reducida de simulacros de maceración para investigar el impacto de diferencias en nivel y termoestabilidad de enzimas de energía diastasica (ED) de malta en la fermentescibilidad resultante de mosto. Un protocolo de maceración modificado de "European Brewery Convention/ American Society of Brewing Chemist" fue utilizado a temperaturas de adición de macerado de 45 a 76℃ en macerados de malta completa y macerados de 30% de adjuntos de arroz. El rendimiento de extracto de malta varió poco con la temperatura de maceración en la mayoría de las variedades en esta gama de temperaturas. Sin embargo, la fermentescibilidad, contenido de maltosa, y nitrógeno amino libre de ese extrac- to fue considerablemente afectado por la temperatura de maceración, de cual 65℃ tuvo el mayor alcance de fermentescibilidad para todas las variedades de malta. El análisis de regresión multilinear de las pruebas de maceración de malta completa y adjuntos de arroz a 65℃ utilizando 43 maltas comerciales demostró que el nivel de α-amilasa y actividad total de dextrinasa límite, Indice Kolbach, y nivel total de actividad β-amilasa y termoestabilidad fueron los predecidores más importantes de calidad de malta para la fermentescibilidad del mosto.