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Substituting synthetic antioxidants with naturally occurring antioxidants has been in the focus of several recent studies. Medicinal and aromatic plants are known to contain a wide array of bioactive compounds. These are endowed with an important antioxidant capacity and other biological activities. This work aimed at assessing potentiality of thyme leaves (TL) as natural additive to enrich and improve oxidative stability of argan oil (AO). To do this, three different proportions (2, 5, and 10%) of TL were added to argan kernels (edible part of fruits) during AO mechanical extraction. AO physicochemical and sensory parameters were evaluated. Such parameters consisted of basic quality indices, fatty acids, sensory evaluation, antioxidant capacity using DPPH• and FRAP assays, pigments (chlorophylls and carotenoids), as well as total phenolic compounds (simple phenolic compounds (SPC) and total flavonoid content (TFC)). The obtained results revealed an improvement of enriched AO physicochemical traits. In fact; at the end of the experiment, there was an increase of pigments, SPC, TFC, antioxidant capacity but a decrease of peroxide value and total oxidation of enriched AO (EAO) as compared to unenriched AO (UAO) in a dose-dependent manner. Regarding fatty acids, generally there are no significant changes between enriched and unenriched AO. Sensory analysis is satisfactory with a reduction of rancidity in EAO depending on TL proportion. However, EAO was marked by high scores of thyme color, flavor, and smell especially with TL at 5 and 10%. Based on the outcomes of this work, it could be concluded that enrichment of AO using TL is a good alternative to synthetic antioxidants giving rise to a new functional product.

The present investigation was performed to evaluate the effects of various synthetic antioxidants (vitamin A, vitamin E, β-carotene, and BHT) on the oxidation of sunflower oil subjected to accelerated thermal storage at 60 °C for three months (12 weeks). The performance of the antioxidants studied was evaluated using several quality parameters: the free fatty acid value (FFA), primary oxidation (via the peroxide value (PV) and K232 value), secondary oxidation products (via the anisidine value (p-AV) and K270 value), and the total oxidation value (TOTOX). The fatty acid composition (FAC), oxidizability value (COX), iodine value (IV), and pigment content (chlorophyll and carotenoid) were also evaluated. The results revealed that the control sample of sunflower oil exhibited higher susceptibility to oxidative deterioration. Antioxidants at 200 ppm were more effective in preserving the oxidative stability of sunflower oil subjected to accelerated storage compared to the control oil. The smallest increases in all stability parameter indexes were recorded for antioxidant-supplemented sunflower oil. However, the IV and chlorophyll and carotenoid contents were reduced. At 200 ppm, vitamin E and β-carotene showed the greatest stability in sunflower oil, while their combination with vitamin A at 100 ppm of each showed the lowest stability. In addition, synthetic antioxidants provided greater protection against the degradation of polyunsaturated fatty acids (PUFAs). The highest level of PUFA degradation was recorded in the control oil, followed by the oil containing vitamin A. In conclusion, adding synthetic antioxidants to sunflower oil improves its stability during storage. However, some authors associated these molecules with a health risk due to carcinogenic effects as these molecules have been listed as "Generally Recognized As Safe" (GRAS). [ABSTRACT FROM AUTHOR]

Argan kernels, fruits regurgitated by goats, are 30% cheaper than the regular kernels used to prepare food argan oil. The use of such argan kernels as a cosmetic ingredient, after refining, is thus economically attractive. The oxidative stability of argan oil prepared from sub-quality kernels is not known. In the present paper, the physicochemical quality, oxidative stability indices, and bioactive compounds of refined argan oil (RAO) obtained from sub-quality kernels and virgin argan oil (VAO) were compared and evaluated over a period of storage of 12 weeks at 60 °C. Quality parameters consisted of free fatty acids (FFAs), peroxide value (PV), p-anisidine value (p-AV), UV extinction coefficients (K232 and K270), total oxidation, iodine and saponification values, induction time, fatty acid composition, and tocopherol content. Our outcomes reveal that the combined effects of refining and storage generally resulted in high values of the routinely measured quality indices, including FFA, p-AV, K270, K232, and PV. Likewise, refining reduced the levels of individual tocopherols and unsaturated fatty acids (USFAs) but increased saturated fatty acids (SFAs). Similar trends were observed under storage with decreased levels of tocopherols and high SFA for both RAO and VAO. Storage also resulted in an increased level of USFAs in the case of RAO but not in VAO. The obtained results show that RAO was more sensitive to oxidation than VAO. At room temperature, RAO had a shorter induction time of six months, implying that RAO will have a shorter shelf life compared to VAR. Thus, such instability means that the refining process for argan oil must be carried out with great care, and this oil needs to be protected once refined. [ABSTRACT FROM AUTHOR]