Encapsulation of α-tocopherol in whey protein isolate/chitosan particles using oil-in-water emulsion with optimal stability and bioaccessibility

Abstract

The aim of this study was to develop an oil-in-water (O/W) emulsion using whey protein isolate (WPI)-chitosan (CN) complex to encapsulate α-tocopherol and to characterize their stability and bioaccessibility in vitro. The O/W emulsions prepared under the optimal conditions (mass ratio of WPI:CN = 1: 1, corn oil containing 5 g/100 g of α-tocopherol) exhibited a monomodal distribution (d = 803.3 ± 6.9 nm) with encapsulation rate of 86.3 ± 2.3%. The emulsions were stable under NaCl (0–150 mmol/L), sugar (0–5 g/100 g), 55 °C for 30 min, pH 5–6.5, even storage for 20 d at 4 °C and 25 °C. During gastric digestion, WPI situated at the surface of emulsion particles can be digested into small molecular peptides by pepsin, but the structure of the core-shell particles remained due to the cross-linking with CN. During intestinal digestion, the structure of the particles disintegrated over the digestion time, and the inner-oil phase was released. Release profiles of the α-tocopherol and free fatty acids showed a burst effect followed by slow release. These results suggest that the WPI-CN complex could be used to achieve a controlled and sustainable release of liposoluble bioactive compounds from O/W emulsions.