The effect of roasting process on total phenolic compounds and antioxidant activity of two domestic and wild varieties pistachio oil

One of the most favorable results of roasting process is increasing in antioxidant activity which is mainly due to the formation of mailard reaction products. Roasting of domestic pistachio nut (Ahmad Aghayi cultivar) and wild pistachio nut (P.mutica) was performed by two methods of oven and microwave. After oil extraction, the extract meals of pistachios were prepared and their phenolic content and antioxidant activities were determined. Phenolic content of pistachio meal extract was in the range of 915-797 mg Gallic acid in kg oil. By comparing phenolic compounds before and after roasting, it can be realized that roasting can increase the amount of phenolic compounds and antioxidant activity of pistachio meals. Pistachio meal extracts were added to soybean oil without antioxidant. The soybean oil samples containing pistachio extracts as a natural antioxidant, BHT as synthetic antioxidant and an oil without antioxidant as control maintained in oven at the temperature of 60 in 30 days to evaluate the antioxidant stability and sampling was performed in 1, 15 and 30 days. The results of peroxide and thiobarbituric acid during the storage period showed that the extract of pistachio meal can be used as a good source of natural antioxidant to prevent oxidation in oils.