pH对羔羊背最长肌肌原纤维蛋白热诱导凝胶的影响

【目的】研究pH对无角陶赛特×小尾寒羊F1代羔羊背最长肌肌原纤维蛋白热诱导凝胶硬度、保水性及微观结构的影响，分析凝胶形成过程中作用力的变化，初步揭示pH对羔羊肉热诱导凝胶形成的影响机制。【方法】以不同pH下肌原纤维蛋白热诱导凝胶的硬度、保水性为指标，确定典型pH（5.0、6.0、7.5），并分析该典型pH下肌原纤维蛋白热诱导过程中的化学作用力、热稳定性变化，以及凝胶微细结构的差异。【结果】3个典型pH下羔羊背最长肌肌原纤维蛋白热诱导凝胶表现出不同的凝胶特性：pH 5.0时，凝胶的保水性最差、微观结构杂乱无序；pH 6.0时，凝胶硬度最低；pH 7.5时，凝胶的保水性、硬度最大且具有致密有序的微观结构。形成凝胶的主要作用力为疏水相互作用，但pH对离子键、氢键具有较大影响，不同pH下凝胶的形成机制存在差异。【结论】pH可通过影响体系的化学作用力，改变蛋白质之间以及蛋白质与水之间的相互作用，形成具有不同保水性、质构特性和微观结构特性的凝胶。

Effect of pH on Heat-Induced Gel of Myofibrillar Protein from Lamb M. longissimus dorsi Muscle

【Objective】The effect of pH on myofibrillar protein heat-induced gel of M. longissimus dorsi sampled from Poll Dorset × Small Tail Han Sheep F1 lamb was studied, and the mechanism of pH influencing the formation of lamb myofibrillar protein heat-induced gel was also discussed.【Method】By measuring the water-holding capacity and hardness of lamb myofibrillar protein gels of different pH values, three typical pH values (pH 5.0, 6.0 and 7.5) were selected. Changes of molecular forces and thermal stability during heat-induced gelation were analyzed under the typical pH values. Difference between gel microstructures of three typical pH values was also compared.【Result】Myofibrillar protein heat-induced gels of lamb M. longissimus dorsi muscle showed different gel properties under three typical pH values. Protein gels had the lowest and a disorder microstructure at pH 5.0, and the lowest hardness was appeared at pH 6.0. The highest water-holding capacity and hardness were both appeared at pH 7.5, with a compact and ordered microstructure. The results of molecular forces analysis showed that hydrophobic interactions was the main forces during the gel formation, but pH influenced the ionic bonds and hydrogen bonds of the system. There might be some differences between the gel formation mechanisms under different pH values. 【Conclusion】 The overall results of this study demonstrated that molecular forces of heat induced gels were changed according to pH values, which resulted in different interactions of proteins or proteins and water, and then gels with different water-holding capacity, texture and microstructure were formed at different pH values.