Effect of Roasting Temperature and Time on the Chemical Composition and Oxidative Stability of Argan (Argania spinosa L.) Oils

Abstract

The effect of roasting on the chemical composition and oxidative stability of oils extracted from argan (Argania spinosa L. Skeels) kernel is studied, observing changes in the characteristics of oils from unroasted and roasted kernels. Argan kernels are roasted at different temperatures (150, 175, and 200 °C) and times (10, 30, and 50 min), in an electric air roaster, prior to oil extraction using the Abencor system. Phosphorus content (PC) of oils increases significantly when roasting temperature and time increases. Roasting facilitates the transfer of phenolic compounds to argan oil. However, only minor changes in characteristics such as peroxide value and carotenoid content of argan oils occurs when roasting temperature and time are raised. The amount of γ‐tocopherol still remains over 85% of the total tocopherols after roasting at the harshest conditions (200 °C, 50 min). However, the content of each tocopherol (α, γ, and δ) gradually decreases when roasting temperature and time increases, certainly due to their thermal degradation. The oxidative stability of argan oil improves when the roasting temperature and time rise. Simultaneously, significant augmentations (p < 0.05) are observed in the specific extinction coefficients in oils prepared at high roasting temperature. The color intensity of oils increases markedly over 175 °C roasting temperature. Practical Applications: This research shows the importance of roasting for producing edible argan oils since its composition, quality and stability are influenced by the conditions of this process. Energy transfer by convection avoids the direct heat of the flame onto the argan kernel and allows the possibility that less polycyclic aromatic hydrocarbons (PAHs) are formed. Furthermore, roasting parameters (temperature and time) should be quantitatively controlled to obtain a desired quality of edible argan oils. These results may help to improve roasting processing for edible argan oil extraction. The effect of roasting temperature and time has been studied with a view to obtain oils of high quality in relation to their physicochemical properties. In the extraction process of edible argan oil, the kernel roasting is the key step that improves the quality and stability of the product.

Optimum roasting conditions of argan kernels (Argania spinosa L.) for the production of high-quality edible argan oil

“…Antioxidant components TPC content varied between 59.52 mg/kg, for the lowest kernel roasting conditions, and 231.66 mg/kg for the hardest ones (Table 1), which was higher than that collected in the literature (Cayuela et al 2008;Marfil et al 2011). Roasting facilitated the transfer of these compounds from the grinding paste to the oil; the higher the roasting temperature and time, the higher the total phenolic compounds (Mattha ¨us et al 2010;Marfil et al 2011;Vujasinovic ´et al 2012;Youn and Chung 2012;Demnati et al, 2018). However, only a small amount of phenolic compounds is transferred to the oil, the main concentration remaining in the press cake which presents a 37 times higher TPC than an edible oil.…”

“…Harhar et al (2011) indicate an induction time from 29 to 38 h for oils obtained from roasted kernels at 110 °C, for 15 and 30 min, respectively. Therefore, the increase in roasting temperature and time of argan kernels, improved the oxidative stability of extracted oils (Mattha ¨us et al 2010;Demnati et al 2018). Roasting conditions have an important impact on argan oil oxidative stability, with a determination coefficient, R 2 of 0.982, and roasting temperature as a significant model term, Eq.…”

“…Although the effect of argan kernel roasting-time, at a constant temperature of 110 °C, on edible virgin argan oil composition and stability was previously studied (Harhar et al 2011), scarce information is available concerning the effect of roasting temperature and time on the oil extraction yield and physico-chemical characteristics of edible argan oil (Belcadi-Haloui et al 2018;Demnati et al 2018).…”

The Properties and Application of Argan Oil in Cosmetology

“…Roasted kernels are ground and pressed manually by using quern, and in this way brown coloured mash is produced, that is manually kneaded and every few minutes warm water is added to the mixture. [13] In order to obtain argan oil, the method of extraction under supercritical conditions with use of CO 2 is also used. The bitter remaining oil-rich press cake is used as cattle feed.…”

“…For argan kernels, the optimal roasting time and temperature were also determined, 50 min and 50 °C, respectively. Argan oil, obtained in these conditions, was classified as “extra virgin.”…”