The ability of Marula and Orange peels extracts to inhibit oxidation in salad dressing oil was investigated. Marula and Orange peels are often discarded during domestic and industrial processing as by-products and, therefore, a loss of essential antioxidants such as phenolic compounds and vitamins. Marula and Orange peel extracts were analyzed for antioxidant activity, phenolic composition, and their molecular fingerprint through Fourier-transform infrared spectroscopy (FTIR). Generally, Marula peel extracts exhibited a higher antioxidant activity than Orange peel extracts. The efficacy of Marula and Orange peel extracts (600 and 1000 ppm) in stabilizing salad dressing oil was determined under accelerated storage (64 °C) for 15 days. After the addition of Marula and Orange peel extracts on salad dressing samples, peroxide value (PV), free fatty acids (FFA) and iodine value (IV) were measured every three days using standard methods. Salad dressing stabilized with Marula peel extracts showed a significantly lower PV (45.0 meq/Kg) than the control sample (74.0 meq /Kg). These results suggest that the addition of Marula Peel Soxhlet Extracts (MPSE) at 1000 ppm increased the salad dressing oil's oxidative stability. Therefore, revealing Marula peel as a potential antioxidant for the stabilization of sunflower oil-based salad dressings.

Keywords: Marula peel; Orange peel; salad dressing