Exposure to heat can enhance the peroxide oxygen formation in pistachio since it contains high amount of unsaturated fats. Should work out to find a suitable temperature for desirable flavour development with reduced time period. Prolonged heat may cause increased level of peroxide value.

I am agree with Suraji. And additionally, you can increase the temperature and decrease the time. So, you can decrease the peroxidation level with decrease exposed time.

Dear Masoomeh, Although heat may increase peroxide vale but the extent of increase depends to moisture content of crude pistachios along with heating temperature and duration. Addition of salt may also increase PV as it may increase temperature.