A study on the effect of repeated heating on the physicochemical and antioxidant properties of cooking oils used by fried food vendors of Lucknow city

Abstract

AbstractThe degradation in the oil quality used by street food vendors during frying operations is an important health concern due to the toxic compounds produced in it. An effective strategy is to detect the oil quality by determining its physicochemical and antioxidant properties to prevent the use of potentially harmful oil. Therefore, this research aimed to investigate the physicochemical and antioxidant properties of frying oils used by local fried food vendors of Lucknow city, India. Oil samples as fresh, after 5th batch and 10th batch of repeated frying (total 15 samples), were collected from five randomly selected street food vendors consumed regularly by the local people. All the samples were analyzed by evaluating physicochemical properties such as specific gravity (SG), viscosity, free fatty acid (FFA), iodine value (IV), peroxide value (PV) and saponification value (SV) using standard methods. The results revealed that almost all repeated frying oils collected were above the permissible limit for FFA, IV, and PV. It was noted that the highest values were obtained in 10th batch of repeated frying oils. On the other hand, slight variation was noted for the SG and SV in all oil samples. Increased usage of the repeated frying oils also resulted in a decrease in total phenolic content and total flavonoid content as compared to values obtained in fresh oil samples. In conclusion, the analysis shows that the repeated frying of vegetable cooking oil degrades its physicochemical and antioxidant qualities, thus should not be consumed. Graphical Abstract