Effect of Freezing-Thawing Times on Collagen Properties and Quality of Yak Meat

To investigate the effects of freezing-thawing times on the collagen properties and the yak meat quality. The changes of shear force, pH, thawing loss, cooking loss, color difference, texture, collagen content and solubility, enzyme activity and microstructure of yak meat were analyzed on different freezing-thawing times. The results showed that with the increase of freezing-thawing times, the shear force of yak meat decreased by 59.72%, moreover, the collagen solubility, β-galactosidase and β-galacturonase activity, thawing loss, cooking loss and b^* value of yak meat increased significantly (P<0.05). Furthermore, the collagen content, shear force, pH, L^* value, a^* value and texture decreased significantly (P<0.05). The correlation results showed that shear force was significantly and positively correlated with L^*, a^*, pH, collagen content and solubility, and texture index (P<0.01). The shear force had a significantly negative correlation with thawing loss, cooking loss, b^*, β-galactosidase activity and β-glucuronidase activity (P<0.001). A significantly positive correlation with the pH and collagen properties (P<0.001). There were significantly positive correlation between collagen properties and texture (P<0.001). With the increase of freezing-thawing times, the tissue structure of yak meat showed severe damage, with blurred borders of muscle fibers. In conclusion, with the increase of freezing-thawing times, the collagen content of yak meat decreased, the solubility increased, the shear force decreased, and the texture worse, and the collagen characteristics had influenced the quality of yak meat, no more than 3 times of freezing-thawing was the suitable times to keep the processing quality of yak meat. The results provide theoretical basis and data support for the product development and quality control of yak meat.