Establishment of Oyster-Water-Soluble Protein–EGCG–Linseed Oil-Emulsion System and Its Lipid Oxidation Stability During Storage and In Vitro Gastrointestinal Digestion

(−)-Epigallocatechin-3-gallate (EGCG) is commonly used as an antioxidant, whereas it is more hydrophilic to effectively exhibit antioxidant activities in oil/water interface of emulsions. Food-derived proteins with higher hydrophobicity can enhance the stability of oil-in-water emulsions by keeping the EGCG at the emulsion interfaces. This study utilized oyster-water-soluble protein (OWP)–EGCG complex, incorporating OWPs extracted from oysters and linseed oil to establish the emulsion system. Optimal conditions for preparing the emulsion were found to be at concentration of 1 mg/mL and 10% oil phase, resulting in the smallest particle size and highest absolute value of zeta potential. Various analyses, including particle size, zeta potential, laser confocal microscopy, cold-field scanning electron microscopy, and three-phase contact angle indicated that ratio of 1:0.05 (OWPs to EGCG) provided the best emulsion stability and antioxidant effects during storage, whereas the ratio of 1:0.1 showed the highest in vitro antioxidant stability during gastrointestinal digestion. Notably, the low ratio (1:0.025) of EGCG led to pro-oxidation, as evidenced by increased levels of 2,4-heptadienal and 2,4-decadienal during storage.

Practical Application: This study offers essential insights for creating stable, antioxidant oil-in-water emulsions that utilize proteins derived from food sources and EGCG. It illustrates the importance of optimizing the ratio of protein to EGCG, which is vital not only for enhancing emulsion stability and antioxidant effectiveness during storage but also for facilitating proper antioxidant release during the digestion process. The results underline the potential for pro-oxidation at lower concentrations of EGCG, providing researchers with a method to mitigate this adverse effect in product formulation. This understanding is readily applicable to the design of functional foods, beverages, and systems for delivering nutraceuticals, where it is crucial to control the release and protect oxidation-sensitive bioactive compounds (such as linseed oil) in emulsified forms.