Incorporating ε-Polylysine Hydrochloride, Tea Polyphenols, Nisin, and Ascorbic Acid into Edible Coating Solutions: Effect on Oxidation and Structure of Marinated Egg Proteins

Abstract

Egg processing products lose their attractions due to protein oxidation, 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 protein oxidation and structure, including total sulfhydryl, dityrosine, protein solubility and hydrophobicity, intermolecular forces, particle size, turbidity, secondary structure, and microstructure were determined. Compared to uncoated marinated eggs (Sulfhydryl: 12.02 μmol/g, soluble protein: 1.13 mg/mL, 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 soluble protein content (1.31 and 1.42 mg/mL), 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 oxidation and improved structural stability. Furthermore, CS-NH-TC-coated samples showed more stable protein secondary structures and less disorderly and aggregated protein microstructure. Our study could provide a theoretical basis for stabilizing the protein structure of egg processing products.