Cold-pressed oils (CPOs), rich in unsaturated fatty acids and bioactive lipids, are considered as healthy oils. Photo-oxidation is a major deterioration reaction for edible oils. In this work, cold-pressed flax (Linum usitatissimum) seed, grape (Vitis vinifera) seed and black cumin (Nigella sativa) seed oils were stored under photo-oxidation conditions for 6 days. The oxidation was monitored by measuring peroxide value (PV), and conjugated diene value (CD). Volatile oxidation compounds (VOOs) were detected using headspace solid-phase micro-extraction (HS-SPME) and capillary gas chromatographic (GC) technique. PV of flax, black cumin and grape seed oils reached up to 87.10, 329.0 and 355.7 meq O2/kg at the end of storage, respectively. CD values in flax seed oil were lower than in grape and black cumin seeds oil during storage. Hexanal was the main compound in flax seed oil during storage while (E)-2-heptenal was detected at the 5th day of storage. Alkadienals including 2,4-hexadienal, and 2,4-heptadienal were formed in flax seed oil after 4 days of storage. Hexanal, (E)-2-heptenal and 2-octenal were the measured aldehydes in grape seed oil. Hexanal and (E)-2-heptenal were the major VOOs from black cumin seed oil during the oxidation experiment. The information obtained in this study are useful in the quality control of CPOs during storage.
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We thank Scientific Research Projects Fund of Abant Izzet Baysal University (Turkey) for providing fund support of the project under contract grant number 2015.09.04.922. We also thank Mr. Süha ERSOY (Oneva Cold Pressing, Istanbul, Turkey) to supply CPOs samples.
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Conflict of interest
The authors declare that they have no conflict of interest.
Research involving human and animal participants
This article does not contain any studies with human or animal subjects.