Influence of roasting temperature and time on the oxidative stability of argan (Argania spinosa L.) oil

The present work aimed to evaluate the oxidative stability of argan oil extracted from almonds roasted at different temperatures (75 - 175°C) and durations (10 - 30 min). Oxidative stability was determined by monitoring three oxidation parameters (PV, K232, and K270) during storage at 65°C for a period of ten weeks. The roasting induced slight variations in physicochemical parameters of the oil (peroxide value and absorbance at 232 and 270 nm). The total tocopherols content significantly decreased with increasing roasting temperature (from 970.1 mg/kg in control, to 301.2 mg/kg in oil roasted at 175°C/10 min). On the other hand, the total tocopherols significantly increased with roasting time (505.3 mg/kg in oil roasted at 175°C/30 min). Similar variations were noted for the different forms of tocopherols (α-, γ-, and δ-tocopherol). Phospholipid contents significantly increased as a function of both the temperature and time of roasting (from 0.20 for control, to 1.37% in oil roasted at 175°C/30 min). The lowest oxidation rate was obtained at roasting temperature of 175°C. In addition, the oxidation rate decreased when the roasting time increased from 10 to 30 min. Thus, the best oxidative stability of argan oil was recorded at 175°C/30 min. The improvement in stability under this roasting condition would be due to the increase in the content of oil in phospholipids, and the formation of Maillard reaction products which are endowed with antioxidant activity. In a nutshell, roasting makes it possible to increase the stability of argan oil despite the loss of tocopherols. The condition of 175°C/30 min was demonstrated as the best roasting condition.