Effect of Ozone Water Treatment on the Quality and in Vitro Digestion Characteristics of Tilapia Surimi

Tilapia fillets rinsed in ozone water were made into surimi, and the effects of ozone water concentration and rinsing time on the quality and in vitro digestive properties of surimi were investigated. Furthermore, the mechanism by which ozone water rinsing improved the quality of tilapia surimi was investigated by analyzing the degree of myofibrillar protein oxidation. The results showed that the whiteness, hardness and gumminess of surimi were significantly increased by ozone water rinsing (P < 0.05), and the surimi rinsed with 10 mg/L ozone water for 10 min had the best gel properties. With the increase in ozone water concentration and rinsing time, the thiobarbituric acid reactive substances (TBARS) value of surimi tended to increase, and the carbonyl content of myofibrillar proteins increased and the total sulfhydryl content gradually decreased. The sensory evaluation results showed that the best sensory quality was obtained by rinsing with 10 g/mL ozone water for 10 min. sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) showed that rinsing with 10–18 mg/L ozone water caused the proteins to cross-link and form small soluble aggregates, while ozone water at concentrations more than 18 mg/L caused the formation of large insoluble aggregates. According to Raman spectra, after rinsing with 10–18 mg/L ozone water, the secondary structure of myofibrillar proteins was gradually unfolded, and the α-helix was gradually converted to β-sheet and random coil. Ozone water rinsing increased the degree of hydrolysis of surimi during in vitro digestion, the highest being observed with 10 mg/mL ozone water rinsing for 10 min. The content of small peptides (100-1000 Da) after digestion was significantly higher than that of the other experimental groups (P < 0.05). In conclusion, moderate oxidation of myofibrillar proteins could improve the quality of tilapia surimi, and the surimi rinsed for 10 min in 10 mg/mL ozone water had the highest sensory quality and the best gel characteristics and in vitro digestive characteristics.