Acetyl and pyruvate groups affect the synergistic interaction between xanthan gum and Gleditsia sinensis polysaccharide by regulating the conformational transition of xanthan gum

The contents of acetyl and pyruvate groups in XG is one of the important factors affecting its order-disorder conformation. However, with the deepening of study on the interaction between XG and other polysaccharides, the impact of this fine structure on the synergistic interaction is still unclear. To resolve this problem, a strategy mainly based on rheology was developed in this study. The deacetylated and depyruvated derivatives were prepared and characterized using FT-IR, XRD, and TG. Moreover, the quantitative results indicated that the acetyl content in Dea-XG is 0.043 % (w/w), and the content of pyruvate group in Dep-XG is 0.99 % (w/w). Rheological experiments revealed that Dea-XG exhibited stronger interactions with GSP (higher viscosity and modulus) compared with XG, while Dep-XG showed weaker synergy. The results of temperature sweep indicated that the binding temperatures of Dea-XG and XG with GSP are above the point of transition from disorder to order of the XG conformation, while Dep-XG is opposite. Temperature-dependent studies further confirm that XG fine structures enhance synergistic effects with GSP by increasing the disordered structure, while increasing the ordered structures inhibit them. This study provides a new idea for comprehensive understanding of the synergistic mechanism between XG and GSP.