Influence of Mentha piperita L. extract in the quality of soybean oil during microwave heating

Oil oxidation accelerates through different methods such as frying and microwave heating which leads to reduced its quality and nutritional value. One of the most effective methods of preventing or delaying oils oxidation is adding antioxidants. In this study, the protective effect of Mentha piperita L. extract added to soybean oil was studied during microwave heating. To achieve this purpose, hidroalcoholic extract of Mentha piperita L. was provided by maceration and analysis of its chemical composition was performed by GC-MS. Antioxidant activity of the extract by DPPH free radical scavenging and OSI test was determined. Oil quality parameters such as peroxide value and acid value, and also, analysis of fatty acid profiles were evaluated during microwave heating. The results showed that the hidroalcoholic extract of Mentha piperita L. had antioxidant compounds like menthone and menthol which caused to increase DPPH inhibition capacity and OSI value. With increasing the microwave heating time, acid value and peroxide value of soybean oil increased. However, with adding different concentrations of the extract, the increase rate of these values, significantly reduced. In addition, with increasing the microwave heating time, the amount of linoleic acid, alpha-linolenic acid, PUFA, USFA, Iodine value, Cox index, PUFA/SFA and USFA/SFA reduced and the amount of palmitic acid, stearic acid and SFA increased. Moreover, with the extract addition to soybean oil, the amount of linoleic acid, alpha-linolenic acid and oleic acid increased and thus the amount USFA, PUFA, MUFA, Iodine value and Cox index took an upward trend. In conclusion, the Mentha piperita L. extract could remarkably reduce the oxidation of soybean oil.