Abstract: 【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.

Key words: lamb meat , myofibrillar protein , heat-induced gel , pH , molecular forces