雪山草鸡宰后肌肉成熟过程中剪切力及肌纤维结构的变化

以120日龄、体重1.5～1.6 kg的雪山草母鸡为原料,取其胸大肌在4℃条件下排酸成熟,于0.5 h、2.0 h、4.0 h、8.0 h和24.0 h 5个时间点取样,研究其肌节长度和肌纤维直径等微观结构以及剪切力的变化。结果表明:肌纤维直径在宰后2.0～4.0 h显著增大(P<0.05),4.0～8.0 h显著减小(P<0.05),之后变化趋于平缓;肌节长度在宰后0.5～4.0 h显著减小,4.0～8.0 h显著增大(P<0.05),之后变化也趋于平缓;而肌肉剪切力(嫩度指标)则在宰后0.5～2.0 h显著增大(P<0.05),2.0～8.0 h显著减小(P<0.05),之后缓慢减小。雪山草鸡宰后肌肉僵直过程中,肌纤维直径变粗,肌节长度缩短,肌肉剪切力增大。而解僵排酸过程中变化正好相反。三者之间呈现一定的相关性。此外雪山草鸡在宰后4℃条件下8.0 h肌肉成熟基本完成。

Changes of shear force and ultrastructure of Xueshan chicken muscles during postmortem aging

In this experiment,120-day-old Xueshan chickens with body weights of 1.5-1.6 kg were taken as the material.The ultrastructural changes of sarcomere length,muscle fiber diameter and shear force value of pectoral muscle at 0.5 h,2.0 h,4.0 h,8.0 h and 24.0 h during postmortem aging under 4 ℃ were evaluated.Results showed that postmortem aging under 4 ℃ could significantly improve the tenderness of meat.The muscle fiber diameter of Xueshan chickens increased significantly at 2.0-4.0 h postmortem(P<0.05) and reduced significantly at 4.0-8.0 h postmortem(P<0.05).The sarcomere length values significantly reduced at 0.5-4.0 h postmortem and increased at 4.0-8.0 h postmortem(P<0.05).The shear force significantly increased at 0.5-2.0 h(P<0.05) and significantly decreased at 2.0-8.0 h postmortem(P<0.05),then decreased slowly.During postmortem aging muscle fiber diameter and shear force increased with reduced sarcomere length level,while during resolution of rigor the results was the opposite.The changes of shear force value of Xueshan chickens were positively correlated with the sarcomere length and muscle fiber diameter.The results also demonstrated that aging process of Xueshan chicken completed at 8.0 h postmortem at 4 ℃ in general.