红外光谱的陆生动物油脂中反刍动物成分鉴别分析

为有效应对违法掺加导致的饲料安全隐患，完善饲用油脂的高效检测手段，满足饲料质量安全的监管需求，以来源可靠的不同种属动物油脂为研究对象，通过在非反刍动物油脂中掺加不同比例（1%，5%，10%，20%，30%和40% W/W）的反刍动物油脂获得试验样品，首次系统应用傅里叶变换红外光谱结合化学计量学方法探讨了陆生动物油脂中掺加反刍成分的鉴别分析方法与模型。研究表明基于掺加比例1%～40%样品集，偏最小二乘判别分析模型正确判别率为100%，无假阳性和假阴性样品；进一步研究发现，基于陆生动物油脂中反刍成分低掺加比例0.1%～40%，0.2%～40%，0.4%～40%，0.6%～40%和0.8%～40%样品集，偏最小二乘判别分析模型的正确判别率均低于100%。且随着最低掺加比例的降低，假阳性与假阴性样品数明显增多，其正确判别率逐步降低。因此，陆生动物油脂中掺加反刍成分判别分析检量限约为1%；进一步通过脂肪酸组成与差异性分析、红外光谱特征波段和特征化学键对比分析探讨其判别分析机理。非反刍动物油脂光谱3 006 cm-1处吸收峰（代表=C-H(cis-)的拉伸振动）和914 cm-1处吸收峰（代表=HC=CH-(cis-)的弯曲振动）明显高于反刍动物油脂样品，主要表征了顺式脂肪酸和不饱和脂肪酸的显著差异。非反刍动物油脂光谱965 cm-1处吸收峰（代表-HC=CH-(trans-)的弯曲振动）明显低于反刍动物油脂样品，主要表征了反式脂肪酸和饱和脂肪酸的显著差异。掺加比例为1%的混合样品中反式C=C键含量显著高于其他低掺加比例的样品，而不同掺加比例样品的顺式C=C键含量和C-H(-CH₂-)键含量均无显著性差异。因此，基于红外光谱的陆生动物油脂中反刍动物成分鉴别分析主要是基于反式C=C键结构的信息表征。综上所述，红外光谱可作为一种兼顾检测效率与检测精度的技术应用于陆生动物油脂中反刍成分的鉴别分析。

Discriminant Analysis of Ruminant Constituents in Terrestrial Fat and Oils by Infrared Spectroscopy

In order to effectively cope with the feed safety risk caused by illegal additions, improve the detection methods of feeding fat and oils and meet the supervision requirements of feed quality and safety, reliable animal fat and oils were collected, and experimental sample set was obtained by adulterating different proportion (1%, 5%, 10%, 20%, 30% and 40% W/W) of ruminant fats in terrestrial animal fat and oils. Fourier transform infrared spectroscopy (FTIR) combined with stoichiometric analysis was used for discriminant analysis of ruminant constituent in terrestrial fat and oils. Results showed, for the sample set of 1%～40% adulteration proportion, the correct discriminant rate of partial least squares discriminant analysis model was 100%, and no false positive and false negative was found. For the sample set of 0.1%～40%, 0.2%～40%, 0.4%～40%, 0.6%～40% and 0.8%～40% adulteration proportion, the correct discriminant rates were all lower than 100%. With the decrease of the lowest adulteration proportion, the number of false positive and false negative obviously increase, the correct discriminant rate decreases gradually, and the detection limit of FTIR discriminant analysis is proved to be about 1%. The discriminant analysis mechanism was further discussed by comparative analysis of fatty acids, infrared spectral band and chemical bond. It was proved that the absorption peaks at 3 006 cm-1 (representing the tensile vibration of C-H (cis-)) and 914 cm-1 (representing the flexural vibration of -HC=CH-(cis-)) of non-ruminant samples were higher than those of ruminant samples. These mainly reflected the significant difference of cis and unsaturated fatty acids. The absorption peaks at 965 cm-1 (representing the flexural vibration of -HC=CH-(trans-)) of non-ruminant samples were lower than those of ruminant samples, reflecting the significant difference of trans and saturated fatty acids. The content of trans-C=C bond for 1% adulteration proportion was significantly higher than the other samples of lower proportions. There was no significant difference for the content of cis-C=C bond and C-H (-CH₂-) bond between the samples with different adulteration proportions. Therefore, the discrimination of ruminant constituent in terrestrial animal fat and oils by FTIR was mainly based on the characterization of trans-C=C bond structure. In summary, infrared spectroscopy can be used as a technique to discriminant ruminant constituent in terrestrial fat and oils with both high efficiency and accuracy.