Study on the Effect of Structural Modification of Xanthan Gum on Its Synergistic Gelation Performance with Locust Bean Gum

The synergistic gelation between xanthan gum (XG) and locust bean gum (LBG) is a classic phenomenon widely adopted for quality control of XG functionality; yet the regulatory roles of XG’s side chain groups—particularly glucuronic acid, whose function remains unexplored—have not been systematically elucidated. In this study, three complementary modification strategies including enzymatic hydrolysis, oxalic acid treatment, and dilute alkali treatment were for the first time combined to precisely modulate the contents of pyruvate, acetyl, and glucuronic acid in XG side chains, constructing a series of XG samples with well-defined gradient structures. Enzymatic hydrolysis and oxalic acid treatment reduced the pyruvate content from 5.80% to 1.05% and 1.42%, respectively, while dilute alkali treatment selectively decreased the acetyl content from 3.97% to 2.58%. The effects were systematically investigated through multi-scale characterization including rheology, texture analysis, scanning electron microscopy and thermogravimetric analysis, combined with correlation analysis. The results revealed that glucuronic acid, together with pyruvate, synergistically enhanced gel network stability through electrostatic interactions and hydrogen bonding. In contrast, acetyl groups acted as negative regulators via steric hindrance, inhibiting hydrogen-bond crosslinking. This study clarifies the distinct functional roles of key XG side chain groups, with the first systematic demonstration of glucuronic acid’s contribution, and provides a theoretical basis for the structure-oriented precise design of XG-based functional gels.