Importance of amounts and proportions of high molecular weight subunits ofglutenin for wheat quality

High molecular weight (HMW) subunits of wheat glutenin are generally consid ered to play a key role in gluten formation and structure, and to be closel y related to wheat quality. Though quantities of HMW subunits in flour have been proposed to be as important for wheat quality as their structures, on ly few quantitative data are available in the literature. Therefore, two as sortments of wheat consisting of 13 international and 16 German cultivars w ere analyzed for their contents and proportions of single HMW subunits usin g an extraction and HPLC procedure on a micro-scale. The results were compa red with quantitative data from the literature that were obtained by sodium dodecylsulfate polyacrylamide gel electrophoresis combined with densitomet ry or by reversed-phase HPLC combined with UV detection. The quantitative a nalyses demonstrated that the contents of HMW subunits varied within a broa d range dependent on genotype and growing conditions. The proportions of su bunits within a given subunit combination, however, varied only within a sm all range. Generally, subunits 2, 5, 7, 10 and 12 were major components and subunits 1, 2*, 6, 8 and 9 were minor components. The levels of HMW subuni ts were highly correlated to dough development time, maximum resistance of dough and gluten, and bread volume. Among HMW subunits the x-type component s (subunits 1-7) were much more important than the y-type components (subun its 8-12). In particular, the presence of subunit 5 (which has an additiona l cysteine residue) and of subunit 7 (which occurs in the greatest amounts) contributed to high wheat quality.