不同冷冻方式对淡水鱼品质的影响

为了研究不同冷冻方式对淡水鱼品质的影响，以鮰鱼、鲈鱼、鳜鱼为研究对象，采用－30?℃平板、－80?℃冰箱和－80?℃液氮分别对鮰鱼、鲈鱼、鳜鱼进行冷冻处理，考察了不同冷冻方式对鮰鱼、鲈鱼和鳜鱼的解冻损失率、加压失水率、蒸煮损失率、pH值、色泽、韧性、微观组织结构、水分分布等指标。结果表明：经过－30?℃平板冷冻、－80?℃冰箱和－80?℃液氮处理后，同种淡水鱼解冻损失率、加压失水率、蒸煮损失率呈现下降趋势，其韧性呈现增大趋势，pH值无显著性变化，细胞间隙呈现下降趋势；对于同种淡水鱼，－30?℃平板冷冻组的白度最高，－80?℃冰箱和－80?℃液氮组间无显著差异（P＞0.05）；低场核磁共振结果表明，对于同种淡水鱼，相对其他两种冷冻方式，－30?℃平板冷冻处理组样品的不可移动水（T22）含量下降，自由水（T23）含量显著升高（P＜0.05）；对于不同淡水鱼，经同种冷冻方式处理后其相关指标间差异性较小。从冷冻速率和品质考虑，选择－80?℃冰箱和－80?℃液氮处理更有利于保持淡水鱼的品质。

Effect of Different Freezing Methods on the Quality of Freshwater Fish

In order to study the effects of different freezing methods on the quality of freshwater fish, channel catfish, Lateolabrax japonicus and mandarin fish were frozen by plate freezing at –30 ℃ (treatment 1), in a refrigerator at –80 ℃ (treatment 2) or with liquid nitrogen at –80 ℃ (treatment 3). The thawing loss percentage of frozen fish was measured as well as pressure-induced water loss percentage, cooking loss percentage, pH, color, toughness, microstructure, water distribution after thawing. The results showed that the thawing loss rate, pressure-induced water loss percentage and cooking loss percentage as well as the space between cells in each fish species with freezing treatments 1, 2 and 3 decreased in that order, whereas the toughness increased. Nevertheless, there was no significant difference in pH among the three treatments. Treatment 1 showed the highest whiteness, yet there was no significant difference between the other two treatments (P > 0.05). Low-field nuclear magnetic resonance (NMR) showed that the content of bound water (T22) in each fish species with treatment 1 was decreased compared with the remaining treatments, whereas the content of free water (T23) was significantly increased (P < 0.05). For each treatment, there were no significant differences in all parameters investigated among fish species. From the viewpoint of both freezing rate and quality maintenance, freezing in a refrigerator at –80 ℃ and with liquid nitrogen at –80 ℃ were more suitable for freshwater.