Effect of mixing temperature on protein secondary structure and thiols in soft and hard wheat flour dough

Dough rheology is important to manufacture different food products. This has primarily been attributed to the differences in flour protein content. Temperature has significant influence on gluten properties and dough rheology. The objective of this study was to find out conformational changes and differences in thiol content of dough from soft wheat flour (SWF) and hard wheat flour (HWF) mixed at four temperatures (4, 15, 30, 40°C). Doughs were sampled at four points - dough development time (DDT), mid-stability (MS), stability departure (SD) and time to breakdown (TBD). Conformational changes of sampled doughs were studied using attenuated total reflectance Fourier transform infrared (ATR/FTIR) spectroscopy and thiols by DNTB assay. There were significant increases in beta sheets and decreases in beta turns for SWF at DDT and SD as mixing temperature increased. Changes in beta sheets and beta turns in HWF at DDT and SD as mixing temperature increased were not significant. The 30°C HWF dough showed significant decrease in accessible thiols with a corresponding increase in total thiols during mixing for all the sampling points. In SWF dough, there were increases in accessible and total thiols during mixing for the 30°C sample. HWF exhibited more accessible thiols though the two had comparable total thiols. Susceptibility of beta sheets and turns to changes in SWF and the low accessible thiols may explain why soft wheat has short dough development time and short stability.