Nondestructive radiative evaluation of adulteration in coconut oil

Abstract

Food adulteration has become a threat to mankind adversely affecting health. Hence, several techniques have been developed to analyze and quantify the adulterant. Coconut oil is one among the widely used edible oils to which paraffin oil appears as adulterant according to several reports. The present study reports simple, sensitive, nondestructive and trace evaluation methods based on radiative spectroscopic techniques. The coconut oil samples with minute amount of paraffin oil are characterized using Fourier Transform Infrared (FTIR), Near Infrared (NIR), Photoluminescence (PL) and Nuclear magnetic resonance spectroscopic (NMR) techniques. The variations in the optical emission from the samples upon photoexcitation are analyzed through the power spectrum and CIE plots. The variation of iodine value with the adulterant paraffin oil is also studied from the NMR spectrum. We propose a method for the quantification of the adulterant paraffin oil by taking the ratios of peaks in the PL spectra. The regression equation connecting the ratio of peak intensities with the percentage of paraffin oil can be used for finding the level of adulterant. The appearance of new spectral features characteristic to the paraffin oil enables precise estimation of the level of adulteration from the PL spectra compared to other spectroscopic methods.