Protection of β-carotene from chemical degradation in emulsion-based delivery systems using antioxidant interfacial complexes: Catechin-egg white protein conjugates

•Polyphenol-protein conjugates were synthesized from catechin & egg white protein.•A hydrogen peroxide-ascorbic acid pair was used as a radical initiator.•Conjugate formation was confirmed by electrophoresis, chromatography & spectrometry.•Emulsions stabilized by conjugates had good physical and chemical stability.•The antioxidant conjugates reduced β-carotene degradation in emulsions during storage.

The aim of the present study was to fabricate catechin-egg white protein (CT-EWP) conjugates as novel food-grade antioxidant emulsifiers designed to improve the physicochemical stability of β-carotene (BC) emulsions. CT-EWP conjugates were synthesized using free radical grafting, and the formation of conjugates was confirmed by electrophoresis and liquid chromatography-mass spectrometry. The physicochemical stability of BC emulsions was characterized by measuring alterations in particle size, ζ-potential and BC retention. The particle size and ζ-potential changed more rapidly at 37 °C than at 4 or 25 °C, however no creaming or oiling-off were observed at any of the storage temperatures, suggesting all emulsions were physically stable throughout the 30-day storage period. Compared to emulsions stabilized by EWP or CT + EWP physical mixtures (no conjugation), CT-EWP conjugate-stabilized emulsions had better resistance to environmental stresses, such as thermal processing and high ionic strengths, which was attributed to a stronger steric repulsion between the oil droplets. CT-EWP conjugates also significantly reduced the degradation rate of BC in emulsions during storage (p < 0.05), which was attributed to their strong antioxidant and interfacial activities. These results indicate that CT-EWP conjugates can be utilized to develop food-grade delivery systems to protect chemically labile lipophilic bioactive compounds.

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