Fabrication of a quaternary ammonium chitosan/pomelo peel extract nanocarrier system for tea polyphenol delivery: characterization, stability, digestibility, and release properties

The application of tea polyphenols is constrained by their inherent chemical instability. In this study, a nanocarrier delivery system for TP was fabricated via electrostatic self-assembly between a natural pomelo peel extract (PP) and quaternary ammonium chitosan (QAC). PP was characterized as a protein-pectin complex, containing 60.1% protein and 23.2% polysaccharides, of which 75.6% was galacturonic acid. PP formed stable complexes with QAC at pH ~4, achieving a TP encapsulation efficiency of 39.6%. The QAC-PP nanocarrier significantly improved TP stability under simulated gastrointestinal conditions, retaining 96.3% of TP after 1 h of gastric digestion and 59.5% after a subsequent 2 h of intestinal digestion. Furthermore, after 12 h of UV irradiation, 58.9% of encapsulated TP remained, substantially higher than the 43.0% retention observed for free TP. This work successfully valorizes pomelo peel waste into an effective nanocarrier, presenting a viable strategy to enhance the stability of TP.