Effect of different slaughter/stunning methods on stress response, quality indicators and susceptibility to oxidation of large yellow croaker (Larimichthys crocea)

This study aimed to investigate the effects of different slaughter methods (immersion in ice/water slurry, T-1; gill cut, T-2; CO2 asphyxia, T-3; percussion (hit on the head with a stick), T-4; Melissa officinalis L. essential oil + CO2, T-5) on physiological stress, oxidative stress, and muscle quality in large yellow croaker. In terms of physiological stress, the levels of glucose (GLU), lactate dehydrogenase (LDH), and catalase (CAT) in CO2 asphyxia samples were significantly lower than those in other samples (p < 0.05). The level of cortisol (COR) in T-1 sample was 1.25-1.84 times higher than that of other samples. The GLU level of T-1 group was 3.2 times higher than that of T-3 sample, and significantly higher than that of other samples. The creatine phosphokinase (CPK) and CAT levels of T-2 samples were the highest (2.03 ng/mL and 8.34 U/mL, respectively). Furthermore, the superoxide dismutase (SOD) and glutathione peroxidase (GPx) analysis revealed that T-3 and T-4 samples could maintain good antioxidant enzyme activity during cold storage. The T-3 samples maintained the stability of the protein (the lowest carbonyls and surface hydrophobicity) and reduced lipid oxidation (lower TBARS). In addition, the analysis of pH and water-holding capacity (WHC) revealed that T-3 samples had better muscle quality. The muscle of T-2 samples kept better color due to bloodletting treatment. The samples obtained after addition of Melissa officinalis L. essential oil had poorer indexes in all aspects compared to the T-3 samples, which might be caused by the long anesthesia time of the essential oil.