Dielectric Spectroscopy Technique for the Detection of Black Seed Oil Adulterated with Sunflower and Palm Kernel Oil

Abstract

Black seed oil is famous for its medical efficacy against some life-threatening diseases.
Owing to its high commercial value, sharp practices among traders have introduced cheaper oil samples as adulterants to raise their profits. This study explored the use of dielectric spectroscopy as a rapid, non-destructive and eco-friendly method for detecting adulteration in black seed oil (BSO) with palm kernel (PKO) and sunflower oil (SFO) as adulterants. Dielectric properties of
pure black seed oil and its blends with palm kernel oil and sunflower oil were measured over a frequency range of 10Hz to 1MHz using impedance analyzer. The results showed significant differences in the dielectric spectra of pure black seed oil and adulterated samples. The procedure successfully detected adulteration levels as low as 5% palm kernel and sunflower oil in black seed
oil. The capacitance value of BSO exceeds those of PKO and SFO. Therefore, the disparity in capacitance values was successfully used in discriminating levels of adulterant in the oil. As the temperature rises, the capacitance values of the BSO, SFO and PKO equally rise. But, all the samples maintain lower capacitance values than BSO. These results showed that the capacitance of
the oil samples varied with temperature and the value for capacitance of the desired sample-BSO, is always higher at low and high temperatures. The distinguishing factor of capacitance can always be used to detect adulteration of the BSO by any oil. Dielectric spectroscopy offered a promising alternative to other expensive and highly technical methods for detecting adulteration in edible oils, with advantages in speed, simplicity, cost-effectiveness and eco-friendly.