Argan oil authentication using visible/near infrared spectroscopy combined to chemometrics tools

Abstract

Visible and Near Infra-Red Spectroscopy (Vis/NIRS) technique was investigated as a non-destructive optical method in order to authenticate argan oil. This study focuses on the detection and quantification of argan oil adulteration with cheap vegetable oils, using Vis/NIRS associated with chemometric tools in the spectral ranges from 500 to 1000 nm and 1000 to 1700 nm. The results achieved using baseline and first derivative pretreatments before analyzing data set with multivariate calibration methods are the best. Partial Least Squares (PLS) model has been established to predict the concentration of adulterants in pure argan oil with a correlation of 0.90, Root Mean Square Error of Prediction (RMSEP) of 4.67, Standard Error of Prediction (SEP) of 4.57 and a bias of 1.26. Principal Component Analysis (PCA) model was established to discriminate samples according to the type of adulterants. The results show Vis/NIRS efficiency as a rapid and non-destructive method and the importance of chemometric tools in order to develop accurate models to authenticate argan oil. Less than 1 s run by NIRS allows the identification of adulterants in pure argan oil from a percentage of adulteration of 0.35% without needing to prepare or destruct samples.