Physicochemical characterization of emulsions stabilized with polysaccharide conjugates extracted from Pu'er tea and their protective effect on curcumin

This study aimed to investigate the influence of different storage periods on the emulsifying properties of polysaccharide-protein complexes (pTPC) in Pu 'er tea through structural analysis and macroscopic characterization, and further explore the stability of pTPC-stabilized nano-emulsions in various environmental conditions. Through determination of chemical composition, interfacial tension, and infrared spectroscopy, it was found that compared to pTPC-13, the higher amino acid content of pTPC-18 led to enhanced hydrogen bonding and electrostatic interactions between intramolecular polysaccharides and polyphenols, thereby increasing its adsorption rate and interfacial film thickness. Additionally, the stability of pTPC-18 stabilized nano-emulsions showed no significant changes in zeta potential and particle size over 0–90 days of storage, pH 2.0–9.0, 25–100 °C, Na⁺ and Ca²⁺, whereas pTPC-13 stabilized emulsions exhibited noticeable droplet aggregation and layering instability under the same stress conditions. Furthermore, for curcumin encapsulation, pTPC-18 nano-emulsions (60%) demonstrated stronger protection of curcumin compared to pTPC-13 nano-emulsions (39%). These results suggest that during long-term storage, the relative increase in protein and polyphenol content within pTPC-18 enhances its emulsifying properties, providing new insights into the development of lipid-active substance delivery systems.