Chitosan–cinnamaldehyde–whey protein concentrate stabilized W1/O/W2 double emulsion for co-encapsulation of tea polyphenols and β-carotene

Water-in-oil-in-water (W1/O/W2) emulsions are capable of co-encapsulating hydrophilic and hydrophobic compounds, but their practical application is often limited by poor physicochemical stability. In this study, a W1/O/W2 emulsion was developed by stabilizing the internal and external aqueous phases with chitosan (CS) and whey protein concentrate (WPC), respectively, while incorporating cinnamaldehyde (CA) into the intermediate oil phase for potential dual-interface stabilization through interfacial interactions. Optimization of the phase composition led to an emulsion with significantly improved storage stability (extending its shelf-life from 7 to 60 days) and enhanced tolerance ability against pH and ionic strength variations. The optimized emulsion successfully co-encapsulated tea polyphenols (TPPs) and β-carotene (BC), maintaining high bioactive compound levels and preserving antioxidant activity under varying pH and thermal conditions. In vitro gastrointestinal digestion assays revealed that CA-modified emulsions significantly improved the bioaccessibility of TPPs and BC to 61.72% and 48.72%, respectively, corresponding to approximately 3.1-fold and 2.0-fold increase compared to their free form. Moreover, the co-encapsulation system exhibited higher antioxidant capacity. This study provides a promising strategy for improving the stability and co-delivery performance of hydrophilic and lipophilic bioactive compounds, with potential applications in development of functional and value-added foods.