Effects of Ozone Gas and Slightly Acidic Electrolyzed Water on the Quality of Salmon (Salmo salar) Fillets from the Perspective of Muscle Protein

To elucidate the mechanisms of ozone gas (OG) and slight acid electrolyzed water (SA) on the quality changes in texture, water-holding capacity, and softening of salmon, the bacterial growth, total volatile basic nitrogen, thiobarbituric acid reactive substance, a* value, texture properties, carbonyl content and free sulfhydryl content, myofibrillar fragmentation index, and proteolytic activities of salmon treated by OG (1 mg/m³ for 10 min) and SA (ACC 30 mg/L, 5 min) individually and in combination were studied. The results showed that total viable counts of SA + OG (dipped in SAEW for 5 min, followed by exposure to ozone for 10 min) was about 3.36 log CFU/g lower than the control (CK) (dipped in distilled water for 5 min) on day 10. Further studies indicate that at the end of storage, the hardness of SA + OG fillets only decreased by 33.95%, while the drip loss and myofibrillar fragmentation index (MFI) were the lowest (i.e., 14.76% and 101.07). The activity of cathepsin D was extensively inhibited by SA + OG, which was only 2.063 U/g meat at the end. In addition, the carbonyl content was 1.90 μmol/g protein, and the free sulfhydryl content was 39.70 mg/mL in the SA + OG group, indicating that protein oxidation was also effectively inhibited. Correlation analysis shows that bacteria and endogenous proteases are the main causes of protein degradation. Overall, the combination of OG and SAEW is an effective way to maintain the muscle quality of salmon by inhibiting bacterial growth and endogenous enzymes.