Effect of native aggregation state of soluble wheat gluten on deamidation behavior in a carboxylic acid/heat water solution

• The open aggregation state of wheat gluten strikingly boosted degree of hydrolysis and deamidation.
• Gliadins were more susceptible to its native aggregation state than glutenins.
• Tempestuous damage to some of hydrogen bonds, hydrophobic interactions and disulfide bonds during dilution.
• Lower concentration of wheat gluten polymer solution, more flexible of modified wheat gluten after deamidation.
• Increasing opportunity of H+ contacting with amide bonds.

To understand the role of native aggregation state (NAS) of soluble wheat gluten and fractions during deamidation in a carboxylic acid/heat water solution, changes in conformation and deamidation behavior as function of protein concentration from dilute to semi-concentrated regimes to control NAS were investigated by physicochemical properties, SDS-PAGE, molecular force change, intrinsic fluorescence emission spectroscopy (IFES) and FTIR. Our data show that, in this solution, the deamidated proteins displayed features characteristic of more scattered and flexible polymer structure in dilute concentration than concentrated ones. Degree of deamidation (DD), HD and Zeta potential exhibited strongly oppositely with the decreasing concentration. HWM-GS, ω-gliadins and LWM-GS degraded into smaller peptides with decreasing of NAS. FTIR and IFES displayed that improved molecular flexibility with decreasing of concentration as detected by the increasing content of β-turn and β-sheet, as well as the red-shift of wheat gluten and gliadins at the expense of α-helix. Hydrophobic and hydrogen bond increased gradually and were dominant in inter-molecule as function of increasing concentration. The above information demonstrated that NAS of soluble wheat gluten dominated changes of deamidation behavior and conformation in a carboxylic acid/heat water solution.