Effect of Xanthan Gum on the Freeze-Thaw Stability of Wheat Gluten

The effect of xanthan gum on the freeze-thaw stability of wheat gluten was evaluated during a 60-day storage period at −18 °C with thawing every 5 days for 4 h at 25 °C. The physicochemical and rheological properties of wheat gluten-xanthan gum mixtures with multiple scales were analyzed. In the control samples (wheat gluten without xanthan gum), the molecular weight by size-exclusion chromatography-multiple angle laser light scattering (SEC-MALLs), content of free SH groups measured by UV/VIS spectrophotometry, and the hole sizes in the wheat gluten network structure shown by SEM increased as the freeze-thaw storage time increased, while the surface hydrophobicity index (H0) decreased. For the wheat gluten-xanthan gum mixtures, more disulfide bonds were preserved and numerous small pores in the wheat gluten structure were observed. Meanwhile, the sample with 0.225% xanthan gum (w/w) had the lowest content of free SH groups. The wheat gluten-xanthan gum mixtures had more α-helixes than the control samples with the same freeze-thaw storage time. Rheological analysis showed that the wheat gluten-xanthan gum mixtures had higher elasticity and viscosity than the control samples. Overall, the addition of xanthan gum improved the freeze-thaw stability of the wheat gluten network.