Gum tragacanth-sodium alginate active coatings containing epigallocatechin gallate reduce hydrogen peroxide content and inhibit lipid and protein oxidations of large yellow croaker (Larimichthys crocea) during superchilling storage

The active coatings supplemented with epigallocatechin gallate (EGCG) (0.16 %, 0.32 %, and 0.64 %, respectively) combined with superchilling storage (-3 ± 0.2 °C) were used to reduce hydrogen peroxide (H2O2) content, and inhibit lipid and protein oxidations of large yellow croaker during 42 days of superchilling storage. EGCG coatings delayed lipid and protein oxidations by inhibiting the generation of H2O2, malondialdehyde (MDA) and carbonyl groups, and maintaining a higher Ca2+-ATPase activity and sulfhydryl content. We also observed that EGCG treatments maintained myofibrillar organized secondary structure by keeping higher α-helix content, and also stabilized tertiary structure during superchilling storage. Low-field nuclear magnetic resonance (LF-NMR) revealed that EGCG treatments might improve the association of water molecules with protein for fixed water. In addition, sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and scanning electron microscope (SEM) images both showed that these treatments could delay the myofibrillar degradation of fresh fish. Overall, we report that the active coatings containing EGCG treatments protect the lipid and protein of large yellow croaker during superchilling storage.