冻融对牛瘤胃平滑肌胶原蛋白降解、交联及品质的影响

Effect of Freeze-Thaw Cycles on the Degradation,Cross-Linking and Quality of Bovine Rumen Smooth Muscle Collagen

为探究冻融过程中肌内结缔组织变化对牛瘤胃平滑肌品质的影响。以牛瘤胃为研究对象,分析不同冻融次数下牛瘤胃平滑肌剪切力、pH值、解冻损失率、胶原蛋白溶解性、胶原蛋白降解酶活力、吡啶交联物含量及微观结构的变化规律。结果表明,随冻融次数的增加,胶原蛋白降解酶(β-半乳糖苷酶和β-葡糖醛酸酶)活力、交联物(赖氨酸吡啶啉和羟赖氨酸吡啶啉)含量、胶原蛋白溶解性、解冻损失率整体呈显著上升趋势(P<0.05),牛瘤胃平滑肌肌内膜肌束膜断裂损伤程度加重,肌纤维之间空隙增大,排列较松散;剪切力、pH值在冻融超过1次后显著下降(P<0.05)。解冻损失率与pH值呈显著负相关(P<0.05),与羟赖氨酸吡啶啉和赖氨酸吡啶啉含量呈极显著正相关(P<0.01),剪切力与β-半乳糖苷酶活力、β-葡糖醛酸酶活力、胶原蛋白溶解性呈极显著负相关(P<0.01)。综上,pH值降低和交联物的形成导致解冻损失增加,而剪切力的下降主要取决于冰晶对肌肉的破坏和蛋白降解的作用。在冻融3次后,剪切力下降速率变慢,解冻损失率升高速率加快。因此控制冻融次数在3次以内,可使平滑肌在保证品质的基础上降低企业损失。

This study aimed to explore the effect of intramuscular connective tissue changes during freeze-thaw cycles on the quality of bovine rumen smooth muscle. The changes in the shear force, pH, thawing loss rate, collagen solubility, collagendegrading enzyme activity, cross-linked pyridine content and microstructure of bovine rumen smooth muscle subjected to different freeze-thaw cycles were analyzed. The results showed that the activity of collagen-degrading enzymes including β-galactosidase(β-gal) and β-glucuronidase(β-GD), the contents of cross-linked lysine pyridinoline(LP) and hydroxylysine pyridinoline(HP), collagen solubility and thawing loss rate significantly increased with increasing freeze-thaw cycles(P <0.05). Similarly, the degree of rupture of endomysium and perimysium as well as the gap between muscle fibers increased,so that the arrangement of muscle fibers became looser. The shear force and pH significantly decreased when the number of freeze-thaw cycles was greater than 1(P < 0.05). The thawing loss had a significantly negative correlation with pH(P <0.05), but a significantly positive correlation with the contents of cross-linked HP and LP(P < 0.01). The shear force a had significantly negative correlation with β-gal activity, β-GD activity, and collagen solubility(P < 0.01). In conclusion, the decrease in pH and the formation of crosslink can lead to an increase in thawing loss, and the decrease in shear force mainly depends on the damage of ice crystal to muscle and protein degradation. The rate of shear loss decreases slowly and the rate of thawing loss increases after 3 freeze-thaws. Therefore, controlling freeze-thaw cycles within three cycles can reduce the loss of enterprises while ensuring the quality of smooth muscle.