Soft wheat quality as related to protein composition

Soft red and white winter wheats from the eastern United Stares, used prima rily to produce cookies, cakes, and biscuits, have quality requirements ver y different from those of bread wheats. In general, soft wheats have been b red to have low protein content, and conventional wisdom has been that prot ein composition of soft wheat is relatively unimportant. To test this hypot hesis, relationships between soft wheal protein composition and end-use fun ctional quality characteristics were examined. Quantitative protein composi tions of eight cultivars of soft wheats grown in a wide area of the eastern United States during seven years (53 samples total) were analyzed by size- exclusion HPLC. Results were statistically correlated with numerous chemica l and physical characteristics and quality factors of these wheats, their f lours, and of cookies baked from the flours. For the entire sample set, whe ats containing high molecular weight glutenin subunits 2+12 showed signific antly different properties and cookie characteristics from those with subun its 5+10, but amounts of most individual fractions correlated poorly with q uality descriptors. For individual soft wheat cultivars, however. amounts o f many individual gliadin and glutenin subfractions correlated significantl y with quality descriptors such as SDS sedimentation, mixograph absorption, peak mixing time, mixograph number, cookie diameter, and top grain. Protei n contents as a function of genotype and environment also differed greatly among cultivars, as did: ratios of gliadin to glutenin. These results clear ly revealed that suitability of soft wheat cultivars for specific products can be rapidly determined by quantitative and qualitative analyses of prote in composition.