冻结及冻藏温度对小龙虾冻藏过程中脂质氧化的影响

本研究将小龙虾热烫后置于真空包装盒内，灌水并抽真空，分别于3 种冻结温度（－20、－40 ℃和－55 ℃）的冰柜内冻结至中心温度为－15 ℃，再于2 种冻藏温度（－20 ℃和－40 ℃）的冰柜中冻藏24 周，测定不同温度冻结和冻藏小龙虾肉的脂肪质量分数、游离脂肪酸（free fatty acids，FFAs）含量以及脂肪酸组成、过氧化值（peroxide value，POV）和硫代巴比妥酸反应物（thiobarbituric acid reactive substances，TBARS）值，探讨冻结及冻藏温度对小龙虾脂质氧化的影响。结果表明：随着冻藏时间的延长，6 组小龙虾的脂肪质量分数、不饱和脂肪酸（unsaturated fatty acids，UFAs）和多不饱和脂肪酸（polyunsaturated fatty acids，PUFAs）相对含量显著下降（P＜0.05），FFAs含量和饱和脂肪酸（saturated fatty acids，SFAs）相对含量、POV、TBARS值总体显著上升（P＜0.05）。冻藏温度相同时，－20 ℃冻结的小龙虾肉的POV、TBARS值高于－40 ℃和－55 ℃，而FFAs含量和脂肪酸组成无明显差异；冻结温度相同时，－20 ℃冻藏小龙虾肉脂肪和FFAs含量、POV、TBARS值均明显高于－40 ℃冻藏组，UFAs和PUFAs含量低于－40 ℃冻藏组，SFAs含量高于－40 ℃冻藏组。结论：冻结温度－40、－55 ℃和冻藏温度－40 ℃均减轻了小龙虾肉脂质的水解和氧化程度。

Effect of Freezing Temperature and Frozen Storage Temperature on Lipid Oxidation of Red Swamp Crawfish

Red swamp crawfish were blanched, vacuum packaged, frozen at three different temperatures (?20, ?40 and ?55 ℃) until the internal temperature reached ?15 ℃, and stored at two different temperatures (?20 and ?40 ℃) for up to 24 weeks. The fat and free fatty acids (FFAs) contents, fatty acid composition, peroxide value (POV), and thiobarbituric acid reactive substance (TBARS) value of crawfish meat were measured to investigate the effect of freezing temperature and frozen storage temperature on lipid oxidation. The results showed that as storage time prolonged, the contents of fat, unsaturated fatty acids (UFAs), and polyunsaturated fatty acids (PUFAs) decreased significantly (P < 0.05), while the contents of FFAs and saturated fatty acids (SFAs) as well as POV and TBARS values increased significantly (P < 0.05). At the same frozen storage temperature, the POV and TBARS values of crayfish meat frozen at –20 ℃ were significantly higher than those of crayfish meat –40 and –55 ℃, while there was not a significant difference in FFAs contents or fatty acid composition; at the same frozen temperature, the fat and FFAs contents, POV, and TBARS values of crayfish meat stored at –20 ℃ were significantly higher than those of crayfish meat stored at –40 ℃, but the contents of UFAs and PUFAs during storage at –20 ℃ were slightly lower than at –40 ℃. In addition, SFAs contents during storage at –20 ℃ was higher than, but not significantly different from, those during storage at –40 ℃. These results indicated that freezing at –40 or –55 ℃ and frozen storage at –40 ℃ alleviated the degree of hydrolysis and oxidation of lipids from crayfish meat.