Changes in protein conformation and sulphydryl content in soft and hard wheat flours during mixing

Protein chemical interaction in wheat flour and dough has been a recent subject of research by cereal chemists. This is with the view of possibly understanding the chemical processes and modulating them to deliver desired product attributes. In this study, thiol content and protein secondary structural changes were studied during dough development in two varieties (Branson and TW301020) using 5,5’-dithiobis(2-nitrobenzoic acid) (DTNB) assay and FTIR-ATR spectroscopy. Samples were analyzed at dough development time (DDT), middle of stability (MS), stability departure (SD), and time to break down (TBD). Branson had increased -turns (40 – 48%) and random structures (12 – 14%) with corresponding decrease in α-helix (10 – 8%) and β-sheet structures (38 – 30%) during the mixing period. In TW301020, there were decreases in turns (38 – 34%) and α-helix (11 – 9%) from DDT to TBD and a corresponding increase in random structures (14 – 20%) during mixing, though -sheets stayed essentially the same. Branson therefore exhibited higher level of hydrophobic interactions than TW301020. This is amplified by the very comparable accessible thiols in the two flours (0.373 µmol/g and 0.37µmol/g at SD) but higher total thiols in the Branson (1.06 µmol/g at SD) than TW301020 (0.95 µmol/g at SD) although they show very similar trend along the dough development points.