Effects of Compound Preservatives on Quality Characteristics of Refrigerated Micropterus salmoides Fillets

In order to solve the problems of short shelf life of refrigerated Micropterus salmoides and the deterioration of quality during refrigerated storage, three preservatives including trehalose (Tre), ginger extract (GE) and Nisin were selected for single factor experiment. L₉(3⁴) orthogonal experiment was used to optimize the ratio of the compound preservative. The total viable count (TVC), pH, total volatile basic nitrogen (TVB-N) content, sensory evaluation, water holding capacity, moisture distribution, texture properties and myofibrillar protein (MP) oxidation stability indexes of Micropterus salmoides during refrigerated storage were measured with the optimal ratio of the compound preservative. The optimal ratio of the compound preservative (3.0% Tre, 0.06% GE and 0.06% Nisin) was obtained by single factor experiment and orthogonal experiment. The results showed that on the 8th day of refrigeration, the logarithm of TVC of control group (CK group) was 6.01, which exceeded the specified limit of spoilage. At the 16th day of storage, the logarithm of TVC of EG2 group was still lower than 6.00, the content of TVB-N was not more than 20 mg/100 g and the pH was less than 7.20. Compared with CK group, free water content in compound preservative groups (EG1 group and EG2 group (that was preferred group)) were significantly decreased, water holding capacity were significantly increased (P<0.05), and the hardness, chewiness and sensory scores of Micropterus salmoides were better than CK group. The related indexes of MP oxidation stability showed that the total sulfhydryl content and Ca²⁺-ATPase activity in compound preservative groups (EG1 group and EG2 group (that was preferred group)) were significantly higher than those in CK group (P<0.05), while the surface hydrophobicity and carbonyl group content were significantly lower than those in CK group (P<0.05), meanwhile, the protective effect of EG2 group on the oxidation stability of MP was better than that of EG1 group. The correlation analysis showed that there was significant correlation (P<0.01) among the indexes of Micropterus salmoides fillets treated with compound preservatives. Comprehensive analysis showed that the quality deterioration of refrigerated Micropterus salmoides could be effectively delayed and the MP oxidation of refrigerated Micropterus salmoides could be significantly inhibited, among which the optimal ratio group (EG2 group) had the best comprehensive effect. This study would provide a theoretical basis for the development and application of water retention and preservation technology for refrigerated Micropterus salmoides.