Enhancing the stabilization of β-carotene emulsion using ovalbumin-dextran conjugates as emulsifier

Abstract

A simple reliable way of improving the emulsifying behaviour of a protein is through covalent binding with a polysaccharide. Thus the effects of ovalbumin (OVA) after modified by dextran (Dex) under traditional wet heating (WH) or microwave heating (MH) on stabilisation and digestion of β-carotene emulsions were comprehensively studied. The emulsifying activity and emulsion stability of OVA were improved significantly after Dex covalent modification under WH or MH condition. OVA–Dex–MH conjugates performed better than OVA and OVA–Dex–WH conjugates in producing an extremely narrow size distribution and high encapsulation rate of β-carotene in emulsion. In addition, OVA–Dex–MH conjugates were considerably more effective in oil droplet stabilization against acidic/alkaline conditions (pH 3.0–10.0), high ionic strength (150 mM NaCl) and high temperature (90 °C for 30 min), consistent with the results of apparent viscosity analysis that the flow behavior index of β-carotene emulsions stabilized by OVA–Dex conjugates decreased compared with that of OVA-stabilized emulsion. Moreover, in the first 30 min of digestion, the degrees of lipolysis in emulsions stabilized by OVA, OVA–Dex–MH, and OVA–Dex–WH conjugates were 60.88%, 80.77%, and 75.32%. However, no significant difference was observed in the protein digestion and bio-accessibility of β-carotene. These results proved that OVA–Dex–MH conjugates have the potential to form stable, food-grade emulsion-based delivery systems against environmental stresses. • EAI and ESI of OVA were improved remarkably after Dex covalent modification. • OVA–Dex–MH conjugates has advantage in producing a narrow size distribution emulsion. • OVA–Dex conjugates can improve the ability of emulsion to resist external environment. • Emulsion resistance to environmental stress was match with apparent viscosity results. • OVA–Dex conjugates were better than OVA in accelerating the release rate of lipids.