Improving Storage Stability of Pistachio Oil Packaged in Different Containers by Using Rosemary (Rosmarinus officinalis L.) and Peppermint (Mentha piperita) Essential Oils

In this study, the antioxidant capacity of rosemary (REO) and peppermint (PEO) essential oils along with butylated hydroxytoluene (BHT) is investigated on oxidative stability of pistachio oil packaged in glass and polyethylene terephthalate (PET). The essential oils (EOs) and their mixture are added at 1500 and 3000 ppm concentrations into the oil stored for 80 days at 60 °C under darkness. In order to evaluate the efficacy of antioxidants, peroxide value (PV), thiobarbituric acid, total phenolic compounds, oxidative stability index (OSI), conjugated dienes and trienes, free fatty acids (FFAs), and iodine value is measured at intervals of 20 days. The results show that natural antioxidants can reduce PV and FFA levels about five‐ and threefolds compared to control, respectively. The OSI in raw pistachio oil (16 h) reduces to 5 h, while in treated sample by REO the reduction is only to 13 h after storage. Generally, the results reveal that in all measured parameters, following order can be observed for antioxidant activity: 3000 ppm REO>3000 ppm PEO>100 ppm BHT >1500 ppm REO >1500 ppm mixed >1500 ppm PEO > control. Moreover, the findings show that glass container is better than PET to retard oxidation process. Practical Application: Pistachio oil is known as a functional and commercial oil that is susceptible to oxidation due to its high level of unsaturated fatty acids. In this work, rosemary and mint essential oils as natural antioxidant are applied for improving oxidation stability of pistachio oil. Antioxidant capacity of rosemary (REO) and peppermint (PEO) essential oils is investigated on oxidative stability of pistachio oil packaged in glass and polyethylene terephthalate (PET). The essential oils are added at 1500 and 3000 ppm concentrations into the oil stored for 80 days at 60 ºC under darkness. The results reveal that in all measured parameters, following order can be observed for antioxidant activity: 3000 ppm REO >3000 ppm PEO >100 ppm BHT >1500 ppm REO >1500 ppm mixed >1500 ppm PEO > control. The findings show that glass container is better than PET to retard oxidation process.