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Grain hardness is an important quality characteristic in wheat and barley. In wheat, it has been shown that softness and hardness are associated with the presence or absence, respectively, of an M r 15 000 protein (called friabilin) on the surface of water-washed starch granules. In order to avoid the redistribution during water washing we have isolated starch granules from hard and soft varieties of barley and wheat using a dry sieving procedure. This showed higher levels of friabilin associated with the starch granules of soft than hard wheats, but similar levels in the two types of barley. The friabilin also differed in distribution and extractability between the hard and soft varieties of the two cereals. In soft varieties the protein was associated with the granule surface and was substantially removed by repeated washing with water. In contrast, friabilin was mainly associated with matrix protein in hard varieties and was readily removed by water washing in wheat but not barley. This difference may relate to the binding properties of the matrix proteins in the two species. Even after repeated washing friabilin was still detected in all the granule preparations using immunofluoresence and western blotting, indicating that a small proportion of the total is tightly bound to the granule.

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.