Co-processed [Argania spinosa L. (Skeels)] oil with thyme (Thymus vulgaris L.) leaves—New product optimization

Abstract

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.

Keywords

• Accelerated aging
• Aromatic and medicinal plants
• Natural antioxidants
• Oxidative stability
• Antioxidant capacity
• Sensory analysis