Abstract: The objective of this research was to investigate effect of NaHCO3 immersion on the sensory quality, fat oxidation and protein oxidation of channel catfish subjected to repeated freeze-thaw cycles. The results showed that the pH value and whiteness of fish fillets decreased significantly, while the thawing loss rate and the degree of fat and protein oxidation increased significantly with increasing number of freeze-thaw cycles. After 4 freeze-thaw cycles, the 2-thiobarbituric acid (TBA) value reached 15 μg/g, indicating that the fish fillets showed deteriorated quality and basically could not be consumed. Compared to the control (without NaHCO3 immersion), NaHCO3 immersion treatment led to an increase in the pH value, and a decrease in the thawing loss rate. It was found that the degree of fat and protein oxidation was highly significantly linearly related to the number of freeze-thaw cycles (R2 > 0.9), and the oxidation rates of fat and protein were greatly reduced with increasing NaHCO3 concentration to 1.0 g/100 mL. Hence, NaHCO3 immersion could to a certain extent inhibit lipid oxidation and protein denaturation in channel catfish during repeated freeze-thaw, maintain water-holding capacity and retard quality deterioration, and this effect was better at 1.0 g/100 mL NaHCO3 concentration than at 0.5 g/100 mL.

Key words: NaHCO3 immersion; freeze-thaw cycle; channel catfish; quality