关键词: 牛肉；真实性判别；脂肪酸指纹；放牧；舍饲；软独立建模分类

Abstract: This work was undertaken in order to demonstrate the feasibility of establishing a model based on fatty acid (FA) fingerprints to discriminate between beef from pasturing and barn feeding systems. A total of 91 samples of biceps femoris, longissimus dorsi, and costal subcutaneous fat from pastured and barn fed cattle from eight counties/banners in the dominant beef cattle farming belt of Inner Mongolia were collected for determination of fatty acids (FAs) by gas chromatography (GC), and principal component analysis (PCA) and descriptive statistics were conducted on the obtained data. Furthermore, soft independent modeling of class analogy (SIMCA) was used to establish a model to authenticate pastured and barn-fed beef. Results indicated that all samples were clustered into pasturing and barn feeding groups, that beef samples from grassland and agricultural areas were also clustered separately, that grassland beef samples from Hulun Buir and Xilingol could be separated, that barn-fed beef samples from Horqin Left Wing Rear Banner and Zhenglan Banner in the eastern region were grouped separately, and that barn-fed beef samples from Helingeer?county and Uxin Banner in the mid-western regions tended to be separated. The contents of n-3 polyunsaturated fatty acids (PUFAs), α-C18:3 n3 (α-linolenic acid), C18:0 and C14:0 in pastured beef were significantly higher than those in barn-feeding beef, and the contents of n-3 PUFAs and α-linolenic acid increased by 1.6 and 2.2 times, respectively. On the other hand, the contents of n-6 PUFAs, C18:1 n9c and C18:2 n6c (linoleic acid) in barn-fed beef were significantly higher than those in pastured beef. The ratio of n-6 to n-3 PUFAs in pastured beef was 3.6, closer to the ideal value. However, the paired t-test and blocked F test on means could not distinguish feeding systems or regions in terms of FA profiles, implying that the conventional statistics has limited ability to evaluate the overall pattern of indicator datasets. PCA performed on FA profiles of the three cuts showed better clustering effect on pastured and barn-fee beef than all samples. FAs of costal subcutaneous fat exhibited the farthest clustering distance for both pastured and barn-fee beef. The internal and external verification accuracy of the established SIMCA model were 100% and 92.6%, respectively. FA-based modeling is feasible to distinguish pastured from barn-fed beef. This study can provide innovative ideas and methods for further studies on meat authentication.

Key words: beef; authentication; fatty acid fingerprint; pasturing; barn feeding; soft independent modeling of class analogies