Rapid evaluation of frying oil degradation using ultrasonic technology

The quality of frying oils covering a wide range of oil degradation and degree of unsaturation was analyzed using ultrasonic techniques. Ultrasonic velocity and attenuation decreased with temperature, and the average velocity temperature coefficients were −3.59 and −3.51 m s−1 °C−1 for monounsaturated (MUO) and polyunsaturated (PUO) oils, respectively. Velocity was linearly related to viscosity, showing higher values for PUO than for MUO. Velocity was also related to the percentage of polar compounds (R2 = 0.77 and 0.86 for PUO and MUO, respectively) and polymers (R2 = 0.86 for PUO and MUO together). The use of velocity and viscosity in a single prediction model allowed to classify 97.5% of the samples correctly, according to the 25% polar compounds limit. Therefore, ultrasonic techniques can be used to characterize thermal degradation of oils when subjected to different frying conditions, which could be useful for frying operators or inspection services.