Varietal and environmental variations in (1→3,1→4)-β-glucan levels and (1→3,1→4)-β-glucanase potential in barley: Relationships to malting quality

Abstract

Three varieties of barley ( Hordeum vulgare cv. Clipper, Galleon and Grimmett) were grown under different soil and environmental conditions at four sites in Australia. Levels of (1→3,1→4)-β-glucans in ungerminated grain and in malt were measured using a specific enzymic assay, and (1→3,1→4)-β-glucanase activity in unkilned (green) malt was determined viscometrically. Hot water extract of malt was used as an index of malting performance of the barley samples. Total (1→3,1→4)-β-glucan content in ungerminated barley depended more on genotypic than environmental factors, whereas (1→3,1→4)-β-glucanase potential was influenced more strongly by environmental conditions. Malting performance was closely correlated with low levels of (1→3,1→4)-β-glucan in the malt and these depended both on low initial levels of the polysaccharide in ungerminated grain and on the production of (1→3,1→4)-β-glucanase during malting. The ability of the grain to produce high levels of (1→3,1→4)-β-glucanase appeared to be a particularly important indicator of malting quality. Thus the malting variety Clipper exhibited malting performances superior to the other varieties at most locations. However, the malting variety Grimmett, which was characterised by a high initial (1→3,1→4)-β-glucan content, produced malt extract values equal to Clipper only when the varieties were grown in Queensland. Levels of 65 °C water-insoluble (1→3,1→4)-β-glucan in ungerminated barley were not related to malting quality.