Abstract: To extend the shelf life of perch meat, a composite coating was developed using chitosan, zein, and perilla essential oil (PEsO). Its effects on quality parameters including total viable count (TVC), total volatile basic nitrogen (TVB-N) content, pH, drip loss, and texture and on protein properties including solubility, turbidity, thiol content, surface hydrophobicity, secondary and tertiary structure were evaluated at regular intervals (0, 2, 4, 6, and 8 d) throughout refrigerated storage at 4 ℃. The results showed that after 8 days of refrigeration, compared with the control, the coated fillets showed significantly lower TVC, TVB-N, pH, and drip loss (P < 0.05), and better texture properties (P < 0.05). In addition, water distribution and nuclear magnetic resonance (NMR) imaging showed that the coating improved water retention by affecting water mobility. Regarding protein oxidation, the coating reduced the turbidity, surface hydrophobicity, and carbonyl content of myofibrillar protein (MP) by 12.11%, 42.86%, and 50.68%, respectively. Meanwhile, the sulfhydryl content and solubility were 31.55% and 16.98% higher than those of the control group, respectively. Circular dichroism (CD) spectroscopy showed that the coating delayed the decrease in the proportion of α-helices and maintained the stability of the secondary structure of MP. Fluorescence spectroscopy showed that the coating inhibited the exposure of tryptophan residues and delayed tertiary structure changes. In conclusion, the chitosan-zein-PEsO composite coating effectively delays protein oxidation and denaturation, protects the spatial conformation of proteins, and maintains the quality of refrigerated perch.

Key words: chitosan; zein; perilla essential oil; perch; protein oxidation