Physicochemical Deterioration in Groundnut Oil Used in Frying Beans Cake and Yam

Abstract

Groundnut/peanut virgin oil (VO) was separately and used in frying beans cake (Akara/Kosai) and yam (dundu/doya) according to the Nigerian culinary method, 1 hour daily for five days. to obtain beans cake frying oil (BCFO). Using same procedure, an equal volume was used in frying yam (Isu/Doya) to obtain yam frying oil (YFO). Some physicochemical properties of the beans cake frying oil (BCFO) and yam frying oil (YFO) were daily monitored till the fifth frying day. There were variations in the changes observed in BCFO and YFO, while BCFO show more rapid degradation. The fifth frying day results were also compared with standard values. After the fifth day, frying oils were analyzed for total polar compounds (TPC), subjected to gas chromatography (GC) analysis, and the physicochemical properties were compared with standards. TPC values obtained are 4.3, 15.4 and 19.73 % for VO, YFO and BCFO respectively, this shows BCFO deteriorates more. GC analysis showed the different changes in fatty acid composition of the VO compared to BCFO and YFO. Unsaturated fatty acids decreased in YFO due to hydrolysis and oxidation; however, there was an increase in unsaturated fatty acids in BCFO, and this due to polymerization aided by substances leached from the beans paste. Keywords: Groundnut/peanut oil, frying, physicochemical properties, total polar materials, gas chromatography.