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Structural Modifications of Gluten Proteins in Strong and Weak Wheat Dough During Mixing

^†Corresponding author. E-mail: saharjazaeri@gmail.com
¹Department of Food Science, University of Guelph, ON, Canada. ²Department of Food Science, University of Campinas, Sao Paulo, Brazil. ³Dipartimento di Scienze per gli Alimenti, la Nutrizione e l'Ambiente (DeFENS), Università di Milano, Italy. ⁴Deceased; formerly Department of Food Science and Nutrition, University of Minnesota, St Paul, MN.

The network-forming attributes of gluten have been investigated for decades, but no study has comprehensively addressed the differences in gluten network evolution between strong and weak wheat types (hard and soft wheat). This study monitored changes in SDS protein extractability, SDS-accessible thiols, protein surface hydrophobicity, molecular weight distribution, and secondary structural features of proteins during mixing to bring out the molecular determinants of protein network formation in hard and soft wheat dough. Soft wheat flour and dough exhibited greater protein extractability and more accessible thiols than hard wheat flour and dough. The addition of the thiol-blocking agent N-ethylmaleimide (NEM) resulted in similar results for protein extractability and accessible thiols in hard and soft wheat samples. Soft wheat dough had greater protein surface hydrophobicity than hard wheat and exhibited a larger decrease in surface hydrophobicity in the presence of NEM. Formation of high-molecular-weight (HMW) protein in soft wheat dough was primarily because of formation of disulfides among low-molecular-weight (LMW) proteins, as indicated by the absence of changes in protein distribution when NEM was present, whereas in hard wheat dough the LMW fraction formed disulfide interaction with the HMW fraction. Fourier transform infrared spectroscopy indicated formation of β-sheets in dough from either wheat type at peak mixing torque. Formation of β-sheets in soft wheat dough appears to be driven by hydrophobic interactions, whereas disulfide linkages stabilize secondary structure elements in hard wheat dough.