Oxidative Stability and Bioactive Composition of Marketed Nigella sativa L. Oils: A Comparative Evaluation

Articles in Press

Document Type : Original Research

Authors
Mukadder Aksoy
Ahmet Ünver
Food Engineering, Necmettin Erbakan University, Konya, Turkey.
Abstract
In this study, the physicochemical properties and oxidative stability of 10 commercial (A–K) and one laboratory-produced (M) cold-pressed black cumin (Nigella sativa L.) oils were evaluated. Analyses included peroxide value, free fatty acidity, fatty acid composition, and thymoquinone (TQ) content. Among the samples, sample C had the highest peroxide value (88.57 meq O₂/kg) and thymoquinone concentration (19.79 mg/g oil), whereas the highest free fatty acidity was observed in sample K (18.53%). Oxidative stability was assessed using the Rancimat method and an accelerated oven storage test at 65 °C over 30 days. During storage, peroxide values ranged from 9.84 to 124.54 meq O₂/kg, showing both increases and decreases depending on the sample. Induction times determined by Rancimat varied between 1.76 and 15.82 hours, indicating an approximately eightfold difference in oxidative resistance among oils. Fatty acid analysis revealed that the oils were rich in linoleic acid (48.30–57.85%) and oleic acid (25.69–42.10%), with palmitic acid ranging from 5.32 to 10.91%. Significant variations in TQ content (0.11–19.79 mg/g oil) were detected, which may be attributed to factors such as seed origin, harvest time, extraction methods, and potential adulteration. These findings demonstrate that the quality of cold-pressed black cumin oils on the market can vary substantially, with some products already exceeding international peroxide and FFA limits or showing unusually low TQ content. This variability highlights the need for standardized production practices and regulatory quality criteria to ensure product safety, authenticity, and consistency.

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Subjects

Journal of Agricultural Science and Technology

Articles in Press, Accepted Manuscript
Available Online from 06 April 2026