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Soft Wheat Quality as Related to Protein Composition¹

¹Presented in part at the AACC 80th Annual Meeting, San Antonio, TX, November 1995. ²National Center for Agricultural Utilization Research, Biomaterials Processing Research, USDA, Agricultural Research Service, 1815 N. University Street, Peoria, IL 61604. Names are necessary to report factually on available data; however, the USDA neither guarantees nor warrants the standard of the product, and the use of the name by USDA implies no approval of the product to the exclusion of others that may also be suitable. ³Corresponding author. E-mail: huebnefr@mail.ncaur.usda.gov ⁴Midwest Area, USDA-ARS, 1815 N. University St., Peoria, IL 61604. ⁵USDA-ARS, Soft Wheat Quality Laboratory, Wooster, OH 44691.

Soft red and white winter wheats from the eastern United States, used primarily to produce cookies, cakes, and biscuits, have quality requirements very different from those of bread wheats. In general, soft wheats have been bred to have low protein content, and conventional wisdom has been that protein composition of soft wheat is relatively unimportant. To test this hypothesis, relationships between soft wheat protein composition and end-use functional quality characteristics were examined. Quantitative protein compositions 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 chemical and physical characteristics and quality factors of these wheats, their flours, and of cookies baked from the flours. For the entire sample set, wheats containing high molecular weight glutenin subunits 2+12 showed significantly different properties and cookie characteristics from those with subunits 5+10, but amounts of most individual fractions correlated poorly with quality descriptors. For individual soft wheat cultivars, however, amounts of many individual gliadin and glutenin subfractions correlated significantly with quality descriptors such as SDS sedimentation, mixograph absorption, peak mixing time, mixograph number, cookie diameter, and top grain. Protein contents as a function of genotype and environment also differed greatly among cultivars, as did ratios of gliadin to glutenin. These results clearly revealed that suitability of soft wheat cultivars for specific products can be rapidly determined by quantitative and qualitative analyses of protein composition.