Effect of Light and Oxygen on Argan Oil Stability during a Long-Term Storage
|Rahma Belcadi-Haloui1, Abderrahmane Zekhnini2, Miloud El Hadek3 and Abdelhakim Hatimi1
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The effect of light and oxygen on the traditional argan oil stability was studied for a period of 12 months. The samples were stored in transparent glass vials at room temperature in the presence of air, nitrogen or in the darkness. The autoxidation was evaluated by monitoring four parameters: tocopherols, unsaturated fatty acids (oleic and linoleic acids), conjugated dienes and peroxide value. The results obtained showed that the oil deteriorated more rapidly in the presence of light compared to the dark. This degradation was more pronounced in the presence of air compared to the nitrogen. Indeed, the results indicated that the time before the maximum level of hydroperoxides, resulting from the degradation of unsaturated fatty acids, was to about 200 days. This period corresponded to the oxidative stability of the oil that was highly depending on the presence of the antioxidants such as tocopherols. Thus, the loss of these molecules led to accelerating unsaturated fatty acids degradation and producing conjugated dienes and hydroperoxides which are the primary products of oxidation. Since the α-tocopherol was destroyed during the first days of storage, these are the γ- and δ-tocopherols which expressed most significant and longer antioxidant effect. The use of nitrogen as storage environment permitted slightly delaying tocopherols deterioration and therefore unsaturated fatty acids oxidation.