Effect of Oregano, Thyme and Rosemary essential oils in comparison with tert-butyl hydroquinone on the quality characteristics of Nigella Sativa seed oil during storage

Although synthetic antioxidants are effective in stabilizing oils against oxidation, because of their negative effects on the health of consumers, their use are being limited. Therefore, the use of natural antioxidants such as essential oils of some plants is increasing. In this study, the effect of three types of essential oils of  oregano, thyme and rosemary as natural antioxidants at concentrations of  0 (control sample) 250, 500, 750 and 1000 ppm and synthetic antioxidant hydroquinone tertiary butyl (TBHQ) at a concentration of 100 ppm on the oil quality characteristics of Nigella Sative seed oil (OSI index, peroxide value, acidity and thymoquinone content) were evaluated on the extraction days, 30, 60 and 90 days of storage. The results showed that the highest and lowest peroxide values ​​were related to antioxidant-free oil (61.13 meqO2/kg oil) and oil containing 750 ppm rosemary essential oil (7.7 meqO2 / kg oil), respectively. The results also showed that the oil samples did not differ significantly in terms of acidity (p <0.05). Thymoquinone as the active ingredient of the oil was better preserved in oils containing essential oils, so that the highest and lowest values ​​were related to oils containing 750 ppm rosemary essential oil (1684 ppm) and oil without antioxidants (1230 ppm), respectively. In general, the results showed that rosemary essential oil at a concentration of 750 ppm instead of TBHQ can be used to stabilize black seed oil and maintain its properties.