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.