Influence of sulphur fertilisation on quantities and proportions of gluten protein types in wheat flour

Although different supplies of sulphur (S) during wheat growth are known to influence the quantitative composition of gluten proteins in flour, an effect on the amount and on the proportions of single protein types has yet not been determined. Therefore, wholemeal flours of the spring wheat 'Star' grown on two different soils and at four different levels of S fertilisation (0, 40, 80, 160 mg S per container) were analysed in detail using an extraction/HPLC procedure. The results demonstrated that the amount of total gluten proteins as well as of the crude protein content of flour was little influenced, whereas amounts and proportions of single protein types were strongly affected by the different S fertilisation. The changes were clearly dependent on the Cys and Met content of each protein type. The amount of S-free omega-gliadins increased drastically, and that of S-poor high-molecular-weight (HMW) glutenin subunits increased moderately in the case of S deficiency. In contrast, the amounts of S-rich gamma-gliadins and low-molecular-weight (LMW) glutenin subunits decreased significantly, whereas the amount of alpha-gliadins was reduced only slightly. S deficiency resulted in a remarkable shift of protein proportions. The gliadin/glutenin ratio increased distinctly; omega-gliadins became major components, and gamma-gliadins minor components, whereas the ratio of HMW to LMW glutenin subunits was well-balanced. (C) 2004 Elsevier Ltd. All rights reserved.