RESULTS: All GMY exhibited post-acidification during storage. The amount of 0.5-1.0 g kg-1 SZS raised titratable acidity, while 1.5-2.5 g kg-1 restrained acid accumulation. SZS dose-dependently increased hardness and consistency and reduced cohesiveness and adhesiveness; 2.0-2.5 g kg-1 groups showed the densest gel. SZS decreased particle size and raised absolute zeta potential to stabilize casein micelles, reduced L* and elevated total color difference (ΔE), turning samples creamy yellow. It remarkably improved DPPH and ABTS scavenging capacity, with the 2.5 g kg-1 group hitting 93.30 g 100 g-1. Fourier-transform infrared (FTIR), Raman and intrinsic fluorescence spectroscopy verified protein secondary structure rearrangement and reconstructed intermolecular forces. It was found 2.0 g kg-1 was the optimal dosage; overdose disrupted colloidal and protein conformational stability. SZS optimized casein polysaccharide networks through hydrogen, hydrophobic and electrostatic interactions.
CONCLUSION: Appropriate SZS supplementation achieved optimal quality regulation of GMY with substantially enhanced storage stability, gel texture and antioxidant activity. This study uncovered the molecular mechanism by which natural plant bioactive compounds improve fermented milk quality via regulating protein conformation and non-covalent interactions, providing theoretical support for the targeted formulation design of functional fermented dairy products. © 2026 Society of Chemical Industry.