Abstract:The stability of Grass Carp Hemoglobin (GCH) and its impact on lipid oxidation and protein oxidation were investigated across pH environments (pH 6.0, 6.5, 7.0, 7.5, 8.0). With increasing storage time, in acidic environments (pH6.0, 6.5), Oxygenated Hemoglobin (OxyHb) decreased significantly, with a 30% and 14% reduction in relative oxygenation rate at 96 hours, respectively, which was lower compared to neutral and alkaline conditions (pH7.0~8.0). Production of MetHemoglobin (MetHb) reached 4.92 μmol/L (6 μmol/L) and 4.3 μmol/L (6 μmol/L) at 72 hours, with MetHb exceeding 70%, significantly higher than in neutral and alkaline conditions (P < 0.05).In acidic environments, the POV values in the GCH group reached 16.1 μmol/kg and 16.2 μmol/kg, and the maximum TBARs values were 4.9 mgMAD/kg and 4.5 mgMAD/kg, significantly higher than in neutral and alkaline conditions (P < 0.05). Total thiol content decreased by 2.5 μmol/g and 1.87 μmol/g in acidic environments, lower than in neutral and alkaline environments, while the GCH group had lower total thiol content compared to the control group. Carbonyl and dimerized tyrosine contents in the GCH group were higher than in the control group (P < 0.05), and in the later stages of storage, these contents were higher in acidic environments compared to alkaline environments. The results demonstrate that GCH exhibited decreased relative oxygenation rates and increased auto-oxidation susceptibility in acidic environments. Lipid and protein oxidation in GCH-treated fish flesh was more pronounced in acidic environments, whereas in slightly alkaline environments, oxidation processes of lipids and proteins were slower, potentially enhancing the preservation of fish products.
