The Study On Meat Characteristics Of Natural Grazing Sunit Sheep

The natural grazing Sunit Sheep with different ages were selected as research group while Small-Tail Sheep with the same age as a control group. The meat production performance, the edible properties of muscle, the flavor precursor substances (fatty acid and amino acids) during growing, the growth characteristics of muscle fiber, and changes in muscle collagen were studied experimentally. The methods employed in this research were combination of normal analysis, Gas chromatography-mass spectrography (GC/MS), Electrophoresis (SDS), High performance liquid chromatography(HPLC) methods. Based on the tests, the characteristics of nutrition, structure and collagen of meat samples were investigated. The study has proved that natural gazing raised Sunit sheep produce excellent and unique characteristics of muscle meat.That Sunit Sheep reached 6 month age has the live body weight of 27.11kg, carcass weight of 12.52kg, dressing rate of 46.18%, the pure meat percentage of 38.96% was established by this research as a standard of raw material animals ready for meat industrySunit Sheep meat has low water loss, high rate of cooked meat, high lever of protein and low moisture. For lambs with 6 month age the water loss 4.16%, rate of cooked meat 57.86%, the average protein lever up to 19.76%, the yield of longissimus dorsi muscle up to 20.16%, and the moisture of biceps femoris muscle lowered to 72.06%. The average fat content in muscle for the 6 month aged animal was 7.25%, cholesterol lever was 27.97mg/kg and it significantly higher that with 12 month age (P<0.05), with the increase of age the cholesterol lever lowered. The diameter of muscle fiber 39.61μm and the fiber density 376.09 pieces/mm2, the muscle fiber diameter and the density were also different significantly along carcass position (P<0.05); It also showed a significant difference in that of yard raising Sunit Sheep (P<0.05). The movement of muscle caused by natural grazing greatly promoted the growth and the diversity of muscle position.Correlation study showed that the shear force value was highly correlated with muscle fiber diameter, fat content and cooked meat percentage (P<0.05), and highly negatively correlated with intermuscle fat content and water loss (P<0.05). The cholesterol lever was highly positive correlated with TBARS value and fat content (P<0.05).The animal meat has a high content of oleic acid, it was 37.23% for the 6 month age lamb and its ratio to the linoleic acid was 40:1. The content of stearic acid was down to 11.78% while it was 21.79% for Small-Tail Sheep raised in yard, and the difference was extremely significant (P<0.01). These contribute to the scarcity of off flavor of Sunit Sheep meatThe content of pentadecanoic acid and daturic acid were evidently higher that in control group (P<0.05), this contributes a certain health functions. The content of palmitic acid and myristic acid declined with age, and accorded with that of cholesterol levers.The contents of amino acids was high, Those were 22.66mg/100mg at 6 month age, 23.31mg/kg at 12 month age, and among the amino acids the content of glutamic acid was up to 14.32mg/100mg and 14.54mg/kg respectively.contributing to meat with nice flavor.The collagen content in the muscle of Sunit Sheep before 12 month age has a significant increase trend (P<0.05).Lever of pyridinoline, an index of cross-linkage degree, increased with age significantly (P<0.01), The lever of pyridinoline in biceps femoris muscle was significantly higher than that in the longissimus dorsi muscle (P<0.05). This indicates that the movement is sufficient for the rear limbs by natural grazing, in turn, it causes the structure of connective tissue to be more developed. Among the collagen the TypeⅠcollagen accounted for 65%-85% and the typeⅢcollagen accounted for 18-25%, the content of Type I collagen which is revertible increased with age while the content of the type III collagen which is invertible declined with age. This accorded with the extend of cross-linkage forming .Correlation study showed that the shear value was highly correlated with the total insoluble and soluble collagen contents and the lever of pyridinoline (P<0.01), and there was also a highly negative correlation between shear force value and solubility (P<0.05).The largest correlation coefficient was for lever of pyridinoline. The content of fat was significantly negative correlated with total insoluble collagen and cross-linkage. (P<0.05) This indicated that the radical factor affecting the tenderness of muscle is the degree of cross- linkage of collagen .