Determination of some physicochemical properties of grape seed oils subjected to different temperature treatment

The aim of this study is determination of the changes in some physical and chemical properties of grapeseed oil by heat treatment. The heat treatment at 40°C and 80°C for 30 minutes were applied to the seeds, provided from Tekirdag Viticulture Research Institute, of Cabernet Sauvignon, Alfons Lavallee, Şiraz and Hamburg Misketi grapes which were grown in Tekirdag Region and harvested in 2018. After heat treatment applied to the seeds, grape seed oils were obtained by cold press. The viscosity, color, free fatty acid, peroxide value, fatty acid composition of cold pressed grape seed oils were analyzed and changes in these properties were examined. Without heat treatment, the only analysis performed in grape seeds was the crude fat content and the values in all varieties were identified in the range of 6,04-9,29%. All other analyzes were carried out in oils obtained by cold press from grape seeds. Accordingly, it was indicated that the initial viscosity values of the oils were in the range of 44,767-52,800 mPa.s and this value increased slightly by heat treatment. When the color values of the oils were examined, it was observed that the color of the oils darkened by heat treatment.Free fatty acidity and peroxide values increased with the heat treatment and it was determined that these varied between 0.203-0.790% and 7.222- 14.874 meq O2/kg respectively when varieties and heat are taken into account. Phenolic substance and antioxidant capacity valuesdecreased gradually by heat treatment. When fatty acid composition was examined; it was determined that the average palmitic (C16:0) and linoleic acid (C18:2) values of all cultivars decreased, the average oleic (C18:1) and linolenic (C18:3) acid values of all cultivars increased as heat treatment temperature increased. Stearic acid (C18:0) values decreased at 40oC and increased at 80oC. After the heat treatment (40oC and 80oC), total saturated fatty acid value decreased at 40oC temperature and increased at80oC temperature; total unsaturated fatty acid value increased at 40oC and decreased at 80oC.