不同部位牦牛肉肌纤维特性与肉品质差异

Differences in Myofiber Characteristics and Meat Quality of Different Yak Muscles

为从肌纤维特性方面探究牦牛3个部位肌肉品质的差异,本研究以牦牛背最长肌、腰大肌和半膜肌为研究对象,比较了其剪切力、肌节长度、肉色、蒸煮损失率和pH值的差异,采用酶组织化学染色和实时荧光定量聚合酶链式反应法表征了其肌纤维特性,并分析了每个品质指标与肌纤维之间的相关性。结果表明:3个部位肌肉的品质指标差异明显,其中腰大肌有较高的pH值和a^*值,嫩度较好,而背最长肌保水性较好;3个部位的肌纤维特性差异显著(P<0.05),腰大肌具有较高比例的Ⅰ型肌纤维(50.8%)和较高的MYH7 mRNA相对表达量,肌纤维直径显著低于背最长肌和半膜肌(P<0.05);Ⅰ型肌纤维数目比和肉品质密切相关,其与剪切力呈负相关,与肌节长度和蒸煮损失率呈正相关;Ⅰ型肌纤维面积比与L^*值呈显著负相关(P<0.05)。结论:可以通过提高肌肉中Ⅰ型肌纤维的比例来改善牦牛肉品质。

The meat quality of three yak muscles: Longissimus lumborum(LL), Psoas major(PM) and Semimembranous(SM) was compared by considering their myofibril characteristics as well as quality traits(Warner-Bratzler shear force, sarcomere length, meat color, cooking loss rate and pH). The myofiber characteristics were measured by histochemical analysis and quantitative real-time polymerase chain reaction. Meanwhile, the correlation between meat quality traits and myofiber characteristics was analyzed. A significant difference was observed among yak muscles in meat quality traits. PM muscle had higher pH, a^* value and better tenderness than the other muscles. However, the water-holding capacity(WHC) of LL was better than the other muscles. Similarly, there was a significant difference in myofiber characteristics among the muscles(P<0.05). PM had higher number of type Ⅰ fiber(50.8%) and higher relative mRNA expression of MYH7 but significantly lower fiber diameter(P<0.05) than the other muscles. The percentage of the number of type Ⅰ fiber was highly correlated with meat quality traits;it was negatively correlated with shear force, but it was positively correlated with sarcomere length and cooking loss. The area of type Ⅰ fiber was negatively correlated with L^* value(P<0.05). These results suggest that the quality of yak meat could be improved by increasing the proportion of type Ⅰ fiber in muscles.