Conformational rearrangement and polymerization behavior of frozen-stored gluten during thermal treatment

Abstract

To elucidate the underlying mechanism of thermal-induced polymerization process of frozen-stored gluten, the conformational variations and polymerization behavior of fresh and frozen-stored gluten fractions during thermal treatment were comparatively tracked. The combined results of Raman spectra and fluorescence quenching by acrylamide suggested that frozen-stored gluten exhibited lower sensitivity to unfolding response upon heating, and more exposed tryptophan rather than tyrosine was detected for frozen-stored gluten when exceeding 70 °C, leading to the higher apparent binding constant for acrylamide and tryptophan than that of fresh gluten consequently. After the polymerization of glutenin and gliadin at 95 °C, the unstable trans-gauche-trans (t-g-t) conformation of disulfide bonds for frozen-stored gluten occupied more than 80%, while the stable gauche-gauche-gauche (g-g-g) diminished. The trans-gauche-gauche (t-g-g), t-g-t and g-g-g contents for the fresh gluten were similar, accounting for nearly 30%, respectively. Confocal laser scanning microscopy revealed the distorted glutenin network and heterogeneously distributed gliadin aggregates in frozen-stored gluten during thermal treatment. The polymerization ability of high molecular glutenin subunit Ax2, 1Dx5, Bx7.1 as well as the α- and γ-gliadin fractions in frozen-stored gluten were weakened compared with the fresh one.