Responses of breadmaking quality to sulphur in three wheat varieties

Field experiments were carried out at three sites in England to investigate the effects of S fertilisation on breadmaking quality of three winter wheat varieties (Hereward, Rialto and Spark) in the 1996-1997 season. The soils at the three sites differed in extractable S contents. Depending on site, either 180 and 230 kg ha(-1) N or 230 and 280 kg ha(-1) N treatments were factorially combined with three S treatments (0, 20 and 100 kg ha(-1) S). Addition of S increased loaf volume significantly at two sites where grain S concentration was also significantly increased and grain N:S ratio decreased. Application of the extra 50 kg ha(-1) N increased grain protein concentration but did not increase loaf volume at any of the sites. Loaf volume was found to correlate more closely with grain S than with grain protein concentration. Addition of S generally decreased the elastic modulus of gel protein and dough resistance but increased dough extensibility. Despite considerable differences in their dough rheology, the responses in rheology and loaf volume to S were similar in all three varieties. Selected flour samples of Rialto from the Bridgets site were also analysed for the glutenin subunit distribution, showing that S addition increased the relative proportion of low-molecular-weight subunits at the expense of high-molecular-weight subunits of glutenin. This study therefore shows that the beneficial effects of S on breadmaking quality are associated with decreased dough elasticity and increased extensibility resulting from effects on the amount and composition of the glutenin polymers. The results also indicate that S fertilisation is required in some areas of England to maintain breadmaking quality. (C) 1999 Society of Chemical Industry.