Biochemical and Genetic Basis of Wort Fermentability

Abstract

Factors that affect wort fermentability were investigated with 180 doubled haploid lines from an Arapiles/Franklin cross. Barley, grown in South Australia during 2001, was micromalted and analysed using standard methods. Samples were found to have a wide range in malting quality with lines both superior and inferior to the parents for all traits analysed. QTL and statistical analysis of data indicated, for this population, that poor malt modification, beta-glucan in particular, had the greatest negative effect on fermentability. Fermentability was also negatively correlated with the maltotetrose content of wort. A significant QTL for this sugar was coincident with the chromosome 4H locus for the heat-stable beta-amylase (sd2H). Lines with the heat stable enzyme, inherited from Arapiles, had improved fermentabilities of IOB extracts but not of EBC extracts. Glucose, possibly coming from beta-glucan hydrolysis, was found to have a positive effect on fermentability. A significant QTL for wort fructose was in the area of the sdw semi-dwarfing gene on chromosome 3H, highlighting the potential impact of agronomic traits on the genetic analysis of malt quality.