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 whea t 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 f actorially combined with three S treatments (0, 20 and 100 kg ha(-1) S). Ad dition of S increased loaf volume significantly at two sites where grain S concentration was also significantly increased and grain N:S ratio decrease d. Application of the extra 50 kg ha(-1) N increased grain protein concentr ation 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 conce ntration. Addition of S generally decreased the elastic modulus of gel prot ein and dough resistance but increased dough extensibility. Despite conside rable differences in their dough rheology, the responses in rheology and lo af volume to S were similar in all three varieties. Selected flour samples of Rialto from the Bridgets site were also analysed for the glutenin subuni t distribution, showing that S addition increased the relative proportion o f low-molecular-weight subunits at the expense of high-molecular-weight sub units of glutenin. This study therefore shows that the beneficial effects o f S on breadmaking quality are associated with decreased dough elasticity a nd increased extensibility resulting from effects on the amount and composi tion of the glutenin polymers. The results also indicate that S fertilisati on is required in some areas of England to maintain breadmaking quality. (C ) 1999 Society of Chemical Industry.