Quality evaluation of different cuts of yak meat based on standardization analysis and principal component analysis

Abstract: There is now the largest number of yak in China around the world, which has considerable commercial potential. The marketing of yak beef according to different cuts could provide differentiated product of raw meat for consumers and improve industry value of yak beef. But it is uncertain whether the data distribution of meat quality of different cuts from other breeds cattle could be in accordance with yak beef. In order to investigate the quality characteristics of different cuts of yak meat, the shearing force, cooking loss, press loss, L* value, a* value, b* value, crude protein content, crude fat content and moisture of beef cuts of yak such as chuck tender, high rib, ribeye, striploin, tenderloin, eyeround, outside flat, topside, knuckle were determined, and the distribution of quality traits of yak meat among different cuts was analyzed using by analysis of variance, standardization analysis and principal component analysis. There were significant differences in quality traits among various cuts except fat content and moisture (p<0.05). The tenderloin got the lowest score of shearing force with the highest score of cooking loss and press loss in standardization analysis, while the ribeye had the best water holding capacity with score of shearing force higher than 0.6 and lightness (L* value) higher than 0.9. The striploin had worse tenderness and water holding capacity with score of protein content lower than 0.8 which were conventionally considered as high grade product for the other breeds. Meanwhile, the cuts from rear quarters including eyeround, outside flat, topside, knuckle have similar quality characteristics that the shearing force score was lower than 0.4, protein content score was higher than 0.8, the cooking loss score ranged from 0.45 to 0.81 and the press loss score ranged from 0.15 to 0.29 by standardization analysis. That implied that high quality cuts came from rear quarters of carcass of yak. According to the rate of contribution exceeding 75%, three principal component factors could be extracted with PC1 of 34.69%, PC2 of 25.97% and PC3 of 19.12%. The factor PC1 could distinguish cuts of post carcass from middle carcass with factor score of PC1 of post carcass ranged from -0.71 to -1.32 and middle carcass ranged from 0.19 to 1.82. While the PC2 could distinguish chuck tender from other cuts with the score of -2.32 lower than other cuts ranged from -0.27 to 1.03, and PC3 could distinguish ribeye from other cuts with the score of -2.28 lower than other cuts ranged from -0.29 to 1.11. According to the factor loading, this difference between post carcass and middle carcass through PC1 score may be closely related to chemical composition traits including protein content, fat content and moisture with loading plot of -0.77, 0.94 and 0.79 respectively. Therefore, PC1 could be considered as chemical composition factor, PC2 could be considered as meat colour factor with loading plot of -0.83 of L* value and 0.80 of a* value, and PC3 could be considered as water holding capacity factor with loading plot of -0.85 of cooking loss and 0.65 of press loss. It was shown that there were differences among cuts of yak meat, which could be related to the location on carcass of yak.