Quality of used frying fats and oils: Comparison of rapid tests based on chemical and physical oil properties

Most of the present regulations or guidelines on used frying fats and oils for human consumption establish that the content of polar compounds should not be higher than 25% of the oil weight. The standard method for the determination of polar compounds, which is based on adsorption chromatography, is time-consuming and needs laboratory facilities. Thus, rapid and simple methods are necessary to evaluate the quality of frying oils in fried food outlets. In this study, rapid tests based on chemical reactions (Fritest and Oxifritest) and on physical properties (Viscofrit and food oil sensor) have been evaluated in a set of 105 used frying oils as alternative methods to the determination of polar compounds. The results demonstrated that any of the rapid tests assayed are of great utility to determine the point at which frying fats and oils should be discarded. The tests based on physical properties showed better results than those based on chemical reactions, as the number of false results was lower. Furthermore, they can be useful to gain information on the changes in the frying oil quality, as their results showed high correlation coefficients with the determination of polar compounds.This research work was supported by Junta de Andalucía and MCYT (Project AGL 2004–00148). Eliana Rodrigues from the Institute National de Controle de Qualidade em Sau ́de/FIOCRUZ was supported by a fellowship from Coordenaçao de Aperfeiçoamento dePessoal de Nivel Superior do Brasil (CAPES)