Unlocking native xanthan gum via succinylation to construct a hydrophilicity-driven O/W emulsion gel for enhanced...

Succinylated xanthan gum (SA-XG) was developed to overcome native XG's poor emulsion-stabilizing capacity caused by inherent high hydrophilicity, yielding a biocompatible emulsion stabilizer for food, cosmetic, and pharmaceutical applications. Under optimized conditions (SA-XG degree of substitution (DS) 0.03, 0.5% w/v concentration, and oil fraction (φ) 0.5), the introduction of carboxyl groups via succinylation significantly enhanced the hydrophilicity and swelling capacity of XG (water contact angle reduced from 68.19 ± 0.08° to 32.72 ± 0.05°, swelling ratio increased by 6% versus native XG). Cryo-scanning electron microscopy (cryo-SEM) showed swollen SA-XG formed a honeycomb-like 3D viscoelastic network, which, coupled with strong electrostatic repulsion (absolute zeta potential >40 mV), endowed the oil-in-water (O/W) emulsion with exceptional 60-day long-term stability (no phase separation) and uniform 40.5 ± 0.07 μm droplets. Notably, this structural basis also conferred the emulsion pH-responsive stability that adapts to gastrointestinal pH fluctuations, the dominant factor governing in vitro digestion performance. The emulsion achieved a luteolin encapsulation efficiency (EE) of 92.2 ± 1.2%, digestive stability of 61.7 ± 0.4%, and bioaccessibility of 45.6 ± 0.5%, representing a 119% improvement in bioaccessibility compared to the native XG emulsion evaluated under identical experimental conditions. MD simulations confirmed this pH-responsive delivery. While maintaining macroscopic colloidal stability, the microscopic SA-XG network exhibited dense hydrogen bonding in gastric fluid (pH 2.5) to inhibit premature release, whereas deprotonation-driven network swelling in intestinal fluid (pH 7.4) facilitated sustained luteolin release. This work proposed a synergistic stabilization framework driven by enhanced hydrophilicity, viscosity, and electrostatic repulsion based on experimental observations, offering a scalable strategy for advanced emulsion delivery systems.