Stunning methods before slaughter induce oxidation changes of large yellow croaker during cold storage: the role of mitochondria and underlying mechanisms.

BACKGROUND: Improper stunning methods before slaughter could cause fish to deteriorate more quickly during cold storage. However, it is unclear how stunning methods affect the mitochondrial structure and the role of mitochondria in oxidation in muscle‐based food. RESULTS: This study explored the potential mechanism of oxidation induced by different stunning methods (hit on the head, T1; gill cut, T2; immersion in ice/water slurry, T3; CO2 asphyxiated, T4; 40% CO2 + 30% N2 + 30% O2, T5) in large yellow croaker during cold storage. The results showed that T4 samples had the minimum stress response and the mitochondrial membrane potential and permeability were less damaged. Besides, the mitochondrial functional structure and peroxisome of T4 samples were less damaged compared with other samples, which was reflected in higher total superoxide dismutase, catalase and glutathione peroxidase activities. In terms of oxidation indices, the T4 samples showed higher pH values and iron myoglobin contents and lower total volatile basic nitrogen and thiobarbituric acid reactive substances after 168 h cold storage, indicating that the T4 samples significantly maintained oxidative stability of large yellow croaker. CONCLUSION: The CO2 asphyxiation had the least oxidative damage to large yellow croaker during cold storage, possibly because it had the least effect on mitochondrial structure, reactive oxygen species and antioxidant enzyme activity. © 2023 Society of Chemical Industry. [ABSTRACT FROM AUTHOR]