Incorporating ε-polylysine hydrochloride, tea polyphenols, nisin, and ascorbic acid into edible coating solutions: Effect on oxidation and structure of marinated egg proteins

Egg processing products lose their attraction due to protein oxidation and degradation, while the edible coating incorporating antioxidant and antimicrobial agents can address this deficit. In this work, chitosan (CS) in combination with ε-polylysine hydrochloride, tea polyphenols, nisin, and vitamin C (CS–NH-TC) was applied as a novel edible coating material for preserving marinated eggs for 20 days and its effects on egg quality, and protein oxidation and structure were determined. The CS–NH–TC coating exhibited the highest antioxidant and antibacterial activities among all coatings. Compared to uncoated marinated eggs (Sulfhydryl: 12.02 μmol/g, dityrosine: 6251.8, protein hydrophobicity: 3691, turbidity: 0.13 mg/mL, particle size: 342.13 nm), CS- and CS–NH–TC-coated eggs exhibited improved protein stability, as evidenced by a higher sulfhydryl (22.20 and 30.92 μmol/g) and lower dityrosine content (4722 and 4216), protein hydrophobicity (2891.72 and 865.75), turbidity (0.06 and 0.03 mg/mL), and particle size (292.06 and 256.57 nm). Additionally, edible coatings, especially CS–NH–TC coatings, were positively correlated with smaller intermolecular force changes in marinated eggs, corresponding to suppressed protein oxidation and conformational changes. Furthermore, CS–NH–TC-coated samples showed more stable protein secondary structures and less disorderly and aggregated protein microstructure, and better color, texture, and sensory scores. Our study could provide a theoretical basis for stabilizing the protein structure of egg processing products.