Characterization of the Physicochemical Properties of Virgin and Used Vegetable Oil

Abstract

Vegetable oils form a vital part of the diet in many homes. The repeated use of same oil for deep frying is widespread in commercial as well as domestic cooking processes. This study aimed at investigating the physicochemical properties of popular brands of virgin and used edible oils sold in Nigeria to ascertain the effects of using the same oil for repeated frying. Standard methods prescribed by the Association of Analytical Chemists (AOAC) and American oil Chemists Society recommended practice (AOCS) were used to determine relative density (RD), peroxide value (PV), iodine value (IV), acid value (AV), free fatty acid (FFA), volatile matter (VM), viscosity (VY) and insoluble impurities (IP). Results revealed that the temperature change in the oil samples induced a difference in their RDs, AVs and PVs. This was also observed in the proportions of the FFA content of the oil samples before they were used and after two frying cycles. PVs in the study ranged from 1.40 - 13.60 meqO2/kg; IVs ranged from 48.22-118.02 gI2/100g; RDs ranged from 0.91 -0.95 kg/l; AV ranged from 1.37 - 49.56 mgKOH/g; FFA ranged from 0.59 - 11.56%; VM range was 0.0003 to 0.0484 %. VY range was 136.04 -220.53 mgKOH/g and IPs ranged from 5.03 - 9.02 %.