Dispersibility of wheat proteins in aqueous urea solutions—a new parameter to evaluate bread‐making potentialities of wheat flours

Dispersibility of wheat flour proteins in 3M‐urea in 0·01M‐pyrophosphate buffer pH 7‐0 at 4° was highly correlated with bread‐making potentialities of samples representing six hard red winter wheat varieties from 19 locations, and of samples representing composites of hard red winter, northern spring, soft red winter, durum, and soft white (club) varieties from 8 locations. Urea‐dispersible proteins, expressed on an equal‐protein basis, had consistently higher absorbance readings at 280 mμ in poor than in good bread‐making wheat flours. Absorbance of urea‐dispersible proteins of flour increased as a result of deleterious effects of γ‐irradiation of wheat. The protein dispersibility index was negatively correlated with bread‐making potentialities of flours milled from the wheats damaged by γ‐irradiation. It is postulated that ease of dispersibility and disaggregation of proteins in urea are related to structural lability of wheat proteins during mechanical‐ or heat‐processing of wheat dough. Differences in disaggregation due to rupture of hydrogen bonds might explain large differences in oxidation requirements of flours which vary little in levels of disulphideor thiol‐containing amino acids.