**E**ff**ect of Di**ff**erent Packaging Methods on Protein Oxidation and Degradation of Grouper (***Epinephelus coioides***) During Refrigerated Storage**

**Xicai Zhang 1,2,3,4,5, Wenbo Huang 1,2,3,4 and Jing Xie 1,2,3,4,\***


Received: 13 June 2019; Accepted: 6 August 2019; Published: 7 August 2019

**Abstract:** This study investigates the effect of different packaging methods—namely, air packaging (AP), vacuum packaging (VP), and modified atmosphere packaging (MAP)—on the protein oxidation and degradation of grouper (*Epinephelus coioides*) fillets during refrigerated storage. The carbonyl group, myofibril fragmentation index, free amino acids, FTIR of myofibrillar proteins, and total protein SDS-PAGE were determined. The results showed that the protein oxidation degree of the fillets gradually increased as the storage time increased. The FTIR results indicated that the secondary structure transformed from an α-helix to an irregular curl. SDS-PAGE confirmed the degradation of the myosin heavy chain, and that myosin gradually occurred during refrigerated storage. Meanwhile, protein oxidation and degradation were highly correlated. Protein degradation was accelerated by protein oxidation in myofibrils, which included the increase of protein surface hydrophobicity and changes of the secondary structure. In fact, the protein oxidation and degradation of the grouper fillets were effectively inhibited by MAP and VP during refrigerated storage, and MAP (30% N2 and 70% CO2) had the best results.

**Keywords:** grouper; refrigerated storage; packaging methods; protein oxidation; protein degradation
