pH-regulated structural and interfacial properties of OSA starch/whey protein fiber complexes to improve the storage and digestive stability of citrus essential oil emulsions.

In this study, an emulsion delivery system for citrus essential oil (CEO) based on whey protein fiber (WPF) and OSA modified starch (OFE) was successfully developed, and the stability and bioaccessibility of the CEO emulsion were enhanced by pH regulation. The impact of pH-regulated and OFE modification on the structure, emulsification properties, and CEO release behavior of WPF-OFE was systematically examined. Fourier transform infrared spectroscopy (FTIR) and molecular docking analyses revealed that OFE provided the basis for the formation of the ordered structure, and the main interactions between WPF and OFE were hydrogen bonding and electrostatic interactions. Compared with WPF, OFE-modified WPF enhanced the adsorption at the oil-water interface. The WPF-OFE emulsions showed higher emulsification activity index and emulsion stability index, particularly at pH 6.0, where values reached 23.89 ± 0.48 m/g and 46.81 ± 1.41 min, respectively. Notably, significant improvements (P < 0.05) in storage stability, UV stability, and thermal stability confirmed the efficacy of the WPF-OFE in enhancing emulsion stability. At pH 6.0, OFE effectively retarded CEO release by inhibiting WPF degradation in the gastric digestion and facilitated CEO release by reducing the spatial resistance of oil droplets during intestinal digestion, ultimately achieving high bioavailability of CEO.