Physicochemical Changes in Hazelnut, Olive Pomace, Grapeseed and Sunflower Oils Heated at Frying Temperatures

In order to compare the thermal performances to evaluate suitability for frying, hazelnut oil (HNO), olive pomace oil (OPO), grapeseed oil (GSO) and sunflower oil (SSO) were heated for 5 h / 5 consecutive days at 175 +/- 5 degrees C, and sampled at the end of each day. Free acidity, peroxide value, conjugated dienes, total polar materials, viscosity, and CIE color values were measured. Highest values of free acidity, conjugated dienes, total polar materials and viscosity were observed in grapeseed oil sample. GSO has reached to a very viscous state during the earlier hours of the operation; hence it is not suitable for frying. Better thermal performances have found with HNO and OPO when compared to the control oil, SSO. Therefore, both oils can alternatively be used as new frying oils effectively.