Antioxidants dipping treatment improving quality of frozen tilapia fillets

Abstract: In order to improve the stability of frozen tilapia fillets, thiobarbituric acid (TBA) value, Ca2+-ATPase activity, salt-soluble protein content, total volatile basic nitrogen (TVB-N) content and texture were used as the indices. Single-factor experiments that aimed to figure out how antioxidants solution affected the quality of frozen tilapia fillets by dip treating were carried out, and single factors included vitamin E, isoascorbate and tea polyphenols; then an L9(34) orthogonal experiment with antioxidant compounds was performed. The rules on how antioxidant solutions with different concentrations influenced the quality of frozen tilapia, including TBA value, Ca2+-ATPase activity, salt-soluble protein content, TVB-N content and texture were weighted by subjective weighting method, and all modes of combination were ranked, the optimal concentration of antioxidant solutions and the optimal mode of combination were obtained. The results showed that after single-factor experiments, these 3 antioxidants could improve the quality of frozen tilapia and antioxidant properties, and for the concentration of the impregnation solution, the optimal mass concentrations of vitamin E, sodium ascorbate and tea polyphenols were 6, 6 and 4 g/L respectively, and under the conditions above, the quality index of comprehensive evaluation was increased by 29.11%, 18.46% and 46.28% respectively compared to the control group with distilled water soaking for 60 min. The maximum quality index of comprehensive evaluation corresponded to the 4 g/L tea polyphenols, and accordingly the TBA value, the Ca2+-ATPase activity and the mass fraction of salt-soluble protein were 0.1326 mg/kg, 3.00 μmol Piprot/h and 75.82 mg/g respectively. Moreover, after the orthogonal experiment, considering cost analysis combined with better quality, the best combination of antioxidant compounds was 4 g/L sodium erythorbate, 2 g/L vitamin E and 3 g/L tea polyphenols, and accordingly the TBA value, the Ca2+-ATPase activity and the mass fraction of salt-soluble protein were 0.1248 mg/kg, 3.12 μmol /(mg·h) and 77.72 mg/g, which was better than the effect of any of single antioxidant, and compared to the control group with distilled water soaking for 60 min, the Ca2+-ATPase activity was increased by 52.20%, the mass fraction of salt-soluble protein was increased by 16.78%, and the TBA value was dropped by 46.07%. The composite antioxidant is natural antioxidant formula, its antioxidant property for tilapia fillets has been verified by repeated experiments, which is safe and effective, and the formula is simple and has low cost, so it can be considered to popularization and application in industrial production. Moreover, the results can provide the theoretical basis for the antioxidants application in the frozen aquatic products, which may improve the frozen quality.