effect of roasted sesame oil on qualitative properties of frying oil during deep-fat frying

In this study, sesame seed was firstly roasted at 216.8°c for 19.3 minutes and its oil was then extracted. commercial frying oil (cfo) was blended by 10, 20, and 30% roasted sesame oil (rso) and used in deep-fat frying to prepare potato chips. the process was performed daily at 180oc for 1 hour, in five consecutive days. frying performance of the oils was evaluated by the measurement of parameters such as peroxide value, oxidative stability index (osi), total polar compounds (tpc) and fatty acids profile. the results showed that roasting had a great positive influence on phenolic compounds content (21 times) and oxidative stability (3.6 times) of sesame oil. during frying, the level of tpc increased significantly as an increasing rate of 27, 22, 21, 23.2, and 29% was obtained for rso-10%, rso-20%, rso-30%, cfo-tert-butylhydroquinone (tbhq), and cfo, respectively. the osi significantly decreased and, in the fifth day of frying, cfo-tbhq had the highest osi of 10.6 hours followed by rso-30% (8 hours). by increment in rso concentration, the antioxidant capacity of frying oils was elevated, although commercial frying oil containing tbhq exhibited higher activity than rso-30%.