Investigation of thermal stabilities of pumpkin seed oil and its blend with soybean oil and palm olein

Fat oxidation is considered as the most important reason for food spoilage.Oxidative stability and physicochemical properties of pumpkin seed oil (PSO), soybean oil (SBO), palm olein (PO) and their blends were evaluated.For this purpose, viscosity changes and free fatty acid were studied for all the samples during the heating process at 170 ° C for 18 hours. In addition to oxidative stability were studied By Rancimat at temperatures of 110, 130 and 160 ° Cfor all samples. The results showed that any of the individual investigatedoils in pure form undergone more changes in viscosity rather than when it was blended with other oils. So that the lowest rate of change in viscosity was seen for PSO: PO (50:50) and PSO: SBO: PO (33/3:33/3:33/3) blends. The lowest rate of formation of free fatty acids were determined for PSO: SBO (50:50) and PSO: PO (50:50). The results showed that, as with viscosity, the blending of the oils decreased the rate of formation of free fatty acids as compared with any individual oils. In general,different blends of PSO showed the highest induction time (IT) In Rancimat test. PSO: SBO (30:70) had the lowest IT, inwhich, IT of this blend significantly (05/0> P) increased by increasing the proportion of PSO. The results of this study favorablyshowed that PSO blended with other oils could help to improve the oxidation stability and nutritional properties of the blended oils.