Chitosan-sodium alginate bioactive coatings containing ε-polylysine combined with high CO2 modified atmosphere packaging inhibit myofibril oxidation and degradation of farmed pufferfish (Takifugu obscurus) during cold storage

In this study, we explored the effectiveness of chitosan (CH) and sodium alginate (SA) bioactive coatings containing increasing concentrations of ε-polylysine (ε-PL) (0.1%, 0.2%, and 0.3%) combined with modified atmosphere packaging (MAP) in 60%CO 2 /5%O 2 /35%N 2 to inhibit myofibril oxidation and degradation of farmed pufferfish during a cold storage period of 18 days. Our research revealed that ε-PL-enriched CH-SA coatings and high CO 2 MAP noticeably delayed myofibril oxidation by inhibiting the formation of carbonyl groups and by keeping higher sulfhydryl content. We also observed that these treatments preserved myofibril Ca 2+ -ATPase activity, protected their organized secondary structure by retaining higher contents of α-helix and β-sheet, and also stabilised tertiary structure during cold storage. The transmission electron microscope (TEM) images showed that the distortion degree of Z-disk and M-line had become deeper and the gap between sarcomeres had expanded gradually when a comparison was carried out between fresh fish and fish at the end of the cold storage period of 18 days. However, the treated samples were still regular in appearance with distinct light I-bands, dark A-bands and Z-disk. Overall, we report that coatings containing ε-PL and high CO 2 MAP treatments appear to protect the myofibrils of farmed pufferfish during cold storage.