Detection and quantification of soybean and corn oils as adulterants in avocado oil using fourier transform mid infrared (FT-MIR) spectroscopy aided with multivariate calibration

Abstract

Authentication of high value edible oils like avocado oil (AO) is an emerging issue. AO can be target of adulteration with low priced oils like soybean and corn oils. The present study is intended to quantify soybean oil (SO) and corn oil (CO) in avocado oil (AO) using the combination of Fourier transform mid infrared (FT-MIR) spectroscopy and chemometrics. The quantification was carried out by partial least square (PLS) calibration using some spectral processing, namely normal spectra, smoothing, and derivation treatment. Frequencies of 1427-779 cm-1 with normal spectra were suitable for the quantification of SO in AO which revealed high coefficient determination (R2), i.e. 0.9994 and low root mean square error of calibration (RMSEC), i.e 0.86% (v/v). Meanwhile, R2 of 0.9994 and RMSEC of 0.87% (v/v) were obtained by PLS at the combined spectra at frequency regions of 1477-721, 1728-1685, and 3035-2881 cm-1 for quantification of CO in AO. The model was further validated using independent samples and offered high R2 values of 0.9994 (for CO) and 0.9998 (for SO) with root mean square error of prediction (RMSEP) of 0.88% (v/v) (CO) and 0.52 % (v/v) (SO), respectively. In general, FT-MIR spectroscopy serves rapid and accurate determination of CO and SO in AO for authenticity studies.