Abstract: Abstract:Yak is mainly distributed in the Qinghai-Tibet Plateau, and there are more than 16 million yaks in China, which accounts for approximately 95% of the world's yaks. Approximately three million yaks are slaughtered per year and the production of meat (skeletal muscle) is approximately 350 thousand tons, while the production of by-product (stomach, intestines, and other internal organs) is approximately 60 thousand tons. At present, those by-products are consumed as low-value products, and the price of by-products is much lower than that of meat, thus, increasing the edible and economic value of by-products is essential. In fact, smooth muscle belongs to a category of muscle tissue that is widely distributed in animal stomach, intestines, and other internal organs. However, smooth muscle has not been treated as meat. Therefore, enhancing the meat value of smooth muscle is a significant goal. In order to investigate the effect of age on collagen content and texture characteristics of yak rumen smooth muscle. The total, soluble, insoluble collagen content, solubility, cross-linking degree, shear force and texture of 1 - 6 years yak rumen smooth muscle were measured. The results showed that the yak rumen smooth muscle total, insoluble collagen and pyridinoline collagen content were significantly increased with the age increase (P<0.05), and the increased rate were 7.61%, 33.86% and 196.46%, respectively. However, soluble collagen content and collagen solubility of yak rumen smooth muscle were significantly decreased with the age increase (P<0.05), and the decreased rate were 30.80% and 35.72%, respectively, which showed the cross-linking degree of yak rumen smooth muscle increased with age increase, while collagen solubility of yak rumen smooth muscle decreased with the age increase. The shear force, hardness and chewiness of yak rumen smooth muscle significantly increased with the age increase (P<0.05), and the increased rate were 96.48%, 91% and 102%, respectively, while cohesiveness, springiness and gumminess of yak rumen smooth muscle were significantly decreased with the age increase (P<0.05), and the decreased rate were 25%, 32% and 39%, respectively, which showed the texture of yak rumen smooth muscle decreased with age increase. Correlation analysis confirmed that the age of yak rumen smooth muscle had a positive significant correlation with the total collagen content, cross-linking degree, shear force, hardness and chewiness (P< 0.01), and had a negative significant correlation with soluble collagen content, collagen solubility, cohesiveness, springiness and gumminess (P<0.01). Moreover, collagen solubility and cross-linking degree of yak rumen smooth muscle had significant effect on shear force and texture (P<0.01). In summary, age of yak rumen smooth muscle had significant effect on the content, solubility, cross-linking degree of collagen and texture. Texture worse with the age increase of yak rumen smooth muscle. Collagen solubility and cross-linking degree of yak rumen smooth muscle had significant effect on shear force and texture. The rumen smooth muscle had suitable eating quality when the yak three years old. Our research identified the collagen content and texture characteristics change rules of smooth muscle at different ages, and the influence of collagen content and texture characteristics, which will provide theoretical basis and data support for the smooth muscle product development and quality control.