Abstract: The oxidation of oils and fats leads to a reduction in its nutritional value and sensory properties. Today, a new approach to the use of natural antioxidants such as essential oils and herbal extracts has been developed as a good alternative to chemical antioxidants in foods. The walnut green skin can be used as a source of natural compounds with anti-oxidant and antimicrobial properties. In this study, the walnut green skin extracts were extracted with different concentrations of water and ethanol (0.0, 50, 100%), different temperatures (20, 40 and 60 °C) and different time intervals (1, 6.5 and 12 h). Then, different amounts of optimum extract (200, 400, 600, 800 ppm) were added to soybean oil and stored at 65 ºC for 16 days. The oxidative stability of different treatments was evaluated by measuring the peroxide value, TBA value, on days 0, 8 and 16 and compared to the treatment contains 200 ppm of BHT. The results showed that different concentrations of optimum extracts of green walnut skin can reduce oxidation in different treatments (p<0.05). The concentration of 800 ppm was the most effective extract compared to BHT and 600 ppm concentration had a similar function to BHT. Thus, the extracts of walnut green skin could be used as a natural and effective antioxidant to reduce the oxidation rate of soybean oil.
