Study of physicochemical qualities ofpalm-corn composite oil duringintermittent deep frying

Palm oil is the most widely used vegetable oils in Indonesia, while corn oil is suitable for frying and contains phytosterol which can retard oxidative polymerization of heated oil. This research was aimed to study the effect of blending ratio (100:0, 90:10, 80:20, and 70:30 palm to corn oil (v/v)) and frying time (day 0, day 1, day 2, day 3, and day 4) to the physicochemical qualities of heated oil. The physicochemical properties of this oil blend were evaluated during four days of intermittent deep frying. The frying time significantly degraded the quality of oil. The addition of corn oil to palm oil did not give significant effect to the peroxide value, p-Anisidine value, Totox value, and color formation. On the other hand, the addition of corn oil, especially with 70:30 palm to corn oil ratio, was able to reduce the increasing rate of free fatty acid and viscosity of the oils, as well as resulting in lower oil absorption of deep fried soybean curd compared to palm oil. To conclude, the analysis results of viscosity, oil absorption, and free fatty acid indicated that the addition of corn oil to palm oil was able to help the delay of polymerization and hydrolysis reaction, but was not able to reduce the rate of oxidation shown from the results of Peroxide value, p-Anisidine value, and Totox value.