Utilization of Red Onion Skin Extract as a Natural Antioxidant to Reduce Free Fatty Acid Levels in Used Cooking Oil

— The quality of cooking oil, both bulk and packaged, can decrease over time and oil utilization and one of the factors that influence this is the oxidation reaction and hydrolysis reaction. Long storage time can cause an increase in free fatty acid levels because during storage oil undergoes physico-chemical changes due to hydrolysis and oxidation processes. This research aims to utilize shallot skin extract to reduce the levels of free fatty acids found in used cooking oil. Thus, shallot skin is extracted using the maceration method. The independent variables are 5 samples of used cooking oil and cooking oil storage time of 0.3 and 6 days. A fixed variable was determined in the form of the extract content used at 1.6% because it was considered the most effective. The method used to collect data on free fatty acid levels is the alkalimetric titration method. The highest reduction in free fatty acid levels from used cooking oil samples was obtained with a reduction of 30.10% on the 6th day.