傅立叶变换红外光谱鉴别“地沟油”的有效性评估

Effectiveness Evaluation of Illegal Cooking Oil Identification Based on Fourier Transform Infrared Spectroscopy

摘要:

收集食用植物成品油、食用植物原油、餐厨废弃油脂和煎炸废弃油脂共137份，并制备精炼“地沟油”17份，采集各类油脂样品的傅立叶变换中红外吸收光谱，通过比较分析各类样品在1711 cm-1附近吸收峰的形状差异及1711 cm-1和1745 cm-1两处吸收峰的峰高比值的差异，分析造成差异的原因，评估此处吸收峰对鉴别“地沟油”与食用植物油的有效性。结果表明，油脂FTIR在1711 cm-1的吸收峰，或者1711~1745 cm-1处的双峰并非“地沟油”的特征吸收峰形状，而与油脂的酸价有着密切的关系，其强度大小主要取决于油脂样品酸价的高低。当通过“精炼”或“勾兑”的方法降低“地沟油”及其勾兑产品的酸价后，它们在1711~1745 cm-1处的双峰形状也就随之消失。因此，基于FT-IR的上述吸收峰及其形状还不能有效鉴别“地沟油”与食用植物油。

Abstract:

One hundred-thirty seven oil samples including edible vegetable oil, raw vegetable oil, kitchen-waste oil and fried waste oil were collected. And 17 refined illegal cooking oil samples were prepared. Fourier transform infrared spectroscopy (FITR) was used to discriminate the difference in the oil samples. The shape of spectra in 1711 cm-1 and peak height ratios in 1711 cm-1 and 1745 cm-1 were analyzed and evaluated the effectiveness to separate illegal cooking oil from edible vegetable oil. The results showed that the infrared absorption peak in 1711 cm-1 or the double peaks in 1711 cm-1 and 1745 cm-1 were not specific for illegal cooking oil, but highly related to the oil acid value with positive correlation, which decreased when the acid value of illegal cooking oil decreased by refining or blending. Therefore, the FI-TR absorption peaks could not discriminate illegal cooking oil from edible vegetable oils.