标准化法和主成分法评估牦牛不同部位分割肉品质

为了研究牦牛不同部位分割肉的品质特征，该研究测定了牦牛辣椒条、上脑、眼肉、外脊、里脊、小黄瓜条、大黄瓜条、米龙、霖肉9个部位分割肉的剪切力、蒸煮损失、失水率、L*、a*、b*、蛋白、脂肪、含水率9项品质特性，并通过方差分析法、标准化法、主成分法研究其品质特征。结果表明，除了脂肪和含水率外，其余7项品质特性均存在显著差异性（P＜0.05）。标准化分析结果表明小黄瓜条、大黄瓜条、米龙、霖肉4个后部肉具有相似特征，具有较好的嫩度、较高的蛋白含量、中等水平的持水能力。主成分分析共提取出3个主成分因子PC1（34.69%）、PC2（25.97%）、PC3（19.12%），其中PC1可明显区分出中部肉与后部肉差异，根据因子载荷，牦牛肉化学组成（蛋白、脂肪、含水率）与这一差异密切相关。可以得出以下结论：不同部位牦牛肉品质存在差异，这一差异与其在牦牛胴体上的相对位置有关，而牦牛胴体的后部肉品质优于其他部位，因此可以作为开发高档产品的原料来源。

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.