Comparison of the physicochemical properties and volatile compositions of some essential oils from different commercial brands

Recently, interest in natural products such as essential oils has been increasing among consumers. This study therefore aimed to determine and compare the physicochemical and volatile composition of commercially available essential oils of various brands (black cumin seed, sweet almond, pine turpentine and castor oils). For these purposes, the colour, refractive index, viscosity, acid, peroxide, iodine, conjugated diene and triene values of the essential oils were determined. Additionally, the volatile composition of the samples was quantified using gas chromatography-mass spectrometry. Statistically significant differences were observed not only among oils but also among the various brands in the same oil group in terms of physicochemical features. Pine turpentine (PT) oils had the highest peroxide value, whereas castor (CO) oils had the lowest peroxide value. The acid values of black cumin seed (BC) oils were higher than those of the PT, CO, and sweet almond (SA) oils. As expected, the volatile compositions of different essential oils differed. Remarkably, significant differences were observed among the various brands, even within the same oil group, in terms of volatile compounds. Consumers use essential oils for many purposes such as nutraceutical, therapeutic, and cosmetic. Therefore, it is important to determine the quality characteristics of these commercially available oils in order to prevent adulteration and imitation.