用加热萃取电导率双频法检测食用动物油脂中液体石蜡

Analysis of Liquid Paraffin in Edible Animal Fats by Warming Extraction Conductivity Dual Frequency Measurement

以常温下固态食用动物油脂炼制牛油、炼制羊油与炼制猪油为测量对象,采用加热融化进行液相萃取后与工业液体石蜡液相萃取液按不同体积比例制备成系列测量样品,用电导率双频测量法测量混合萃取液电导率。电导率双频测量法采用倍频交流正弦信号输入方式,有效化解了电导池极化效应与电容效应对测量所产生的影响。将混合萃取液电导率平均值达到未混掺有液体石蜡的食用油脂萃取液电导率的1.5倍作为食用油脂中是否混掺有液体石蜡的评判阈值,发现食用炼制牛油、炼制羊油与炼制猪油等的液体石蜡体积浓度比检测下限分别为5.8%、1.9%、3.8%。结果表明,用电导率双频测量法结合加热萃取方式测量食用动物油脂与工业液体石蜡混合萃取液电导率测量精度较高,可用于食用动物油脂品质评估取证。

Solid phase animal fats under room temperature including beef tallow, mutton tallow and lard tallow were taken as measurement samples, which were melted by heating, extraction liquids from which were mixed with that from a kind of mineral oil named industrial liquid paraffin with various volume ratios. Conductivities of the sam- ples were measured by conductivity dual frequency measurement, with which a real physical model were funded in which the capacity effect and polarization effect were taken into consideration and were efficiently resolved by inputting dual frequency sinusoidal signals instead of inputting one. The lower detections of volume ratio for beef tallow, mutton tallow and lard tallow were found to be 5.8%, 1.9% and 3.8 separately, when it was taken as a judgment threshold that the average conductivity value for mixed extraction liquid of animal fats with industrial liquid paraffin was equal to 1.5 times that of pure extraction liquid of animal fats. The precision of measuring conductivities of mixed extraction liquid samples by combination of dual frequency method with heating extraction was presented to be fairly high, which might make it practicable to discriminate industrial liquid paraffin illegally mixed into edible animal fats.