Importance of endosperm modification for malt wort fermentability

Abstract

Malt wort fermentability is dependent on an adequate supply of the essential nutrients required by yeast. The barley and malt factors affecting this supply of nutrients are not well understood. This study used two doubled haploid populations (Arapiles × Franklin, TR251 × HB345), the latter with a hulless barley parent, to investigate effects of barley and malt quality on fermentability. Populations were grown and malted at different locations resulting in a broad range in malt quality with significant differences in extract, modification and enzyme levels. Fermentability, as indicated by apparent attenuation limit and ethanol levels, also showed significant differences among samples. Modification was the most important factor for good fermentability. There appeared to be several different mechanisms by which modification affected fermentability. High viscosities, slow starch release during mashing, increased glucose supply from better β-glucan breakdown and increased free amino nitrogen levels all affected fermentability. Effects of starchdegrading enzymes on fermentability became more significant in better modified malts with α-amylase showing stronger effects than diastatic power. The poorer fermentability of hulless barley malt was predominately due to low levels of α-amylase, although, free amino nitrogen also appeared to be an important factor.