Gliadin [BSA]

Gluten-starch interactions are of specific importance during the processing of cereal-based products. However, the mechanisms for gluten-starch interactions have not been illuminated. The effects of various gliadin/glutenin (gli-glu) ratios (0:10, 3:7, 5:5, 7:3, and 10:0) on the pasting, thermal, and structural properties of wheat gluten-starch mixtures were investigated. The peak, through, and final viscosities were obviously decreased, and the setback value initially increased and then decreased with increasing gli-glu ratios during the rapid viscosity analysis (RVA). Differential scanning calorimetry showed that the enthalpy changes increased with increasing gli-glu ratios. Thermogravimetric analysis showed a slight increase in the degradation temperature of the mixtures as the gli-glu ratio increased, although it was still lower than that of wheat flour. However, there was no significant difference in the weight loss among different gli-glu ratios. Rheometer-Fourier transform infrared (FTIR) spectroscopy showed that the C-6 peak at 996 cm(-1) for all the samples was displaced or disappeared due to the hydrogen bond fracture caused by water molecules entering the starch granules. It was also found that the absorption peak in amide II of gli-starch was more obvious than that of glu-starch. The CLSM obviously described the change structure of mixtures with different gli-glu ratio during starch gelatinizaton. By studying the changes in gluten protein components and how they affected the thermal and structural properties of starch, a simple model was proposed to describe the gelatinization process of the mixtures with different ratios of gli-glu and briefly describe the interactions between starch and wheat gluten components. Optimization of the proportion of protein components in wheat flour will enable greater control over the structural characteristics and elasticity of wheat food products.

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.