Cultivar differences in modification patterns of protein and carbohydrate reserves during malting of barley

Winter- and spring-sown barley cultivars of good- and poor-malting quality were micro-malted and samples taken at different stages of the process. Histochemical and biochemical techniques were used to examine changes in total protein, cell walls, carbohydrate reserves and the patterns and extent of grain modification. No differences were observed in the general patterns of protein distribution between mature grains of the various cultivars. In all cases the initial utilisation of the protein reserves was first observed in the sub-aleurone layer of the endosperm, with subsequent modification gradually progressing further into the grain. Differences in the patterns of grain modification were observed, with good-malting cultivars demonstrating faster and more uniform breakdown of cell walls and digestion of endosperm reserves than poor-malting cultivars. These differences cannot be explained by variation in levels of alpha- amylase or β- glucanase; the good and poor quality cultivars examined showed similar levels of extractable activity from malted grains.