Lipids and oils are among invaluable and essential foods which have an important role in health and life survival. However oxidation of lipids during processing and subsequent storing decreases oil quality and deteriorate its flavor; it also ends in oxidative products such as free radicals. The oxidative processes cause various diseases like cancer, diabetes and atherosclerosis . In order to prevent lipid oxidation and consequences of free radicals, use of antioxidants is recommended. In recent years, use of synthetic antioxidants has been limited due to their side effects on health, therefore, researches for antioxidant replacement suggest herbal antioxidant. Pepper mint ( Mentha.piperita) from Lamiaceaefamily is an aromatic plant with antioxidant properties .Recently one of innovation in food packaging technology is active package in which an antioxidant is incorporated into the package. Advantage of this kind of packaging is to increase shelf life of food without direct addition of antioxidant to the food as a result of gradual releasing of antioxidant.In the current study, synthetic antioxidant (BHT) with 0.01 and 0.02 percent concentration and 0.02% and 0.04% pepper mint essential oil were added to pure soy bean oil and poured in polyethylene bottles. Also soy bean oil without antioxidant was filled in active polyethylene bottles containing synthetic antioxidant (0.37% and 1.7%) and the essential oil (0.37% and 84%). They were put in oven set at 40 0 C up to 2 months. Oil sampling was done every 15 days and physicochemical characteristics were tested. Results showed that during storage time antioxidant was released from the package to the oil and the trend was increased over the time. Considering peroxide value and conjugated diene, essential oil in oil delayed the oxidation more than the essential oil in package but BHT in package reduced oxidation more than BHT in oil. Comparing peroxide value and TBA index, essential oil in oil had more antioxidant effect than BHT in oil due to more spectra of phenolic compounds, however there was not significant difference between essential oil and BHT activities in package. As unsaturated fatty acid was dropping during storing, refraction index and iodine value decreased. When it comes to iodine value, all oil treatments declined oxidation, whereas structure of unsaturated fatty acid, refraction index and iodine value did not change.Mint essential oil is suggested as a natural antioxidant. Also active package containing antioxidant especially synthetic antioxidant is a good replacement for direct add of these antioxidants to oil. Key words : Vegetable Oil, Antioxidant, Pepper Mint, Essential oil, Package
