Quality effect of repetitive use of frying oil by street food vendors on quality of the oil

Background: Frying of food triggers different chemical reactions and most street food vendors use oils repeatedly before discarding in order to reduce cost. This repetitive use coupled with exposure to air can however cause degradation in the oil leading to unpleasant odour and flavor.Objective: The study determined the effect of repetitive use of frying oil by street fried food vendors on the oil quality.Methods: Questionnaire was administered to ten vendors in Ilishan-Remo to ascertain how frying oils are stored and how often they reuse oil to fry. Three samples of frying oils (10ml each) of three randomly selected street fried foods (fish, yam and akara) were obtained every other day for four days and taken to the laboratory where peroxide value and free fatty acid content were analyzed. Data were statistically analyzed using descriptive statistics and the results were presented as mean and standard deviation.Results: All (100%) respondents reused frying oil frequently and mixed fresh oil with degraded oil constantly. Majority (80%) of the vendors did not store the oil properly after each use. The amount of peroxides (43.125- 95.625mEeq/kg) in oil samples exceeded the maximum level of Codex standards (10mEq/kg). The range (0.7% to 3.29 %) of free fatty acids of the oil samples also exceeded the maximum accepted level of 0.3%.Conclusion: There was a high level of deterioration and rancidity in all the oil samples due to poor storage and excessive repetitive use by the street vendors.Keywords: Rancidity, repetitive use, oil, storage, street food