冻融对冷藏藏羊肉保水性及蛋白氧化和溶解特性的影响

为了探究反复冻融现象发生对冷藏过程中藏羊肉保水性及肌原纤维蛋白氧化和溶解特性的影响。本文以经反复冻融0、1、3、5次后分别在4 ℃下冷藏1、3、5、7 d的欧拉藏羊肉为研究对象，测定分析肌肉保水性、肌原纤维蛋白（myofibrillar protein，MP）氧化特性、蛋白溶解度及肌纤维显微结构变化。研究发现，在贮藏期间T5组较T3组相比，解冻损失率分别显著增加了63.08%、43.20%、20.58%、16.20%；T5组较T0组相比，滴水损失率显著增加了29.16%、21.09%、22.16%、25.47%，加压损失率显著增加了23.76%、20.45%、21.17%、20.15%（P<0.05）；在不同冷藏时间点MP羰基含量和表面疏水性显著上升，总巯基含量则显著下降（P<0.05）；蛋白溶解度均随冻融循环次数的增加显著下降，肌纤维显微结构的破坏程度也随冻融循环次数的增加而逐渐加重。冻融次数与蛋白氧化程度和溶解度之间呈极显著相关性（P<0.01），且保水性与上述指标之间相关性极显著（P<0.01）。上述结果说明，冻融循环次数越多，肌肉蛋白氧化程度和肌纤维显微结构破坏越严重、蛋白溶解度越低，因而越不利于维持肌肉的保水性；同时，冷藏过程也对肌肉保水性、蛋白氧化、溶解度和肌纤维显微结构有不利影响。因此，对肌肉在贮藏运输和生产加工过程中温度波动的控制对维持肌肉品质具有重要意义。

Effects of Repeated Freezing-thawing on Water Holding Capacity,Protein Oxidation and Dissolution Characteristics of Tibetan Mutton during Chilled Storage

The purpose of this study was to investigate the effects of repeated freeze-thaw phenomenon on on water holding capacity, myofibrillar protein oxidation and dissolution characteristics of Tibetan mutton during chilled storage. Tibetan mutton was as the research objects and after repeated freezing-thawing for 0, 1, 3 and 5 times, the mutton was refrigerated at 4 ℃ for 1, 3, 5 and 7 days. And then the water holding capacity, myofibril oxidation characteristics, protein solubility and muscle fiber microstructure were determined. The results showed that compared with T3 group, the thawing loss rate of T5 group was significantly increased by 63.08%, 43.20%, 20.58% and 16.20%, and compared with T0 group, the drip loss rate of T5 group was significantly increased by 29.16%, 21.09%, 22.16% and 25.47%, respectively and the pressure loss rate significantly increased by 23.76%, 20.45%, 21.17% and 20.15% (P<0.05) during chilled storage. The carbonyl content and surface hydrophobicity all presented a significant increase and total sulfhydryl content presented a significant decrease (P<0.05), meanwhile, with the increase of freezing-thawing cycles the protein solubility decreased significantly as well as the damage degree of muscle fiber microstructure increased gradually. The correlation results showed that freezing-thawing cycles times were significantly correlated with the degree of protein oxidation and protein solubility (P<0.01), and the water holding capacity also had significant correlation with the above indexes (P<0.01). The above results indicated that the more times of freezing-thawing cycle, the more serious oxidative degree of myofibril protein, the more serious damage to muscle fiber microstructure, and the lower protein solubility, which was therefore not conducive to the maintenance of meat water holding capacity. At the same time, the refrigeration process also had adverse effects on water holding capacity, myofibril oxidation, protein solubility and muscle fiber microstructure. Therefore, the control of temperature fluctuation during meat storage, transportation and production is of great significance to maintain meat quality.