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

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 degrees 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 degrees C, the unstable trans-gauchetrans (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 alpha- and gamma-gliadin fractions in frozen-stored gluten were weakened compared with the fresh one.