Exploring ultrasound for monitoring phospholipid content in edible oils

This study investigates the feasibility of using ultrasound to monitor phospholipid (PL) content in edible oils during refining, aiming to establish a reliable alternative or complementary method to conventional physico-chemical analyses. Ultrasonic measurements were performed on soybean oil samples (crude, semi-refined, degummed, and fully refined) in a pitch-catch configuration within a temperature-controlled environment. Using refined oil (0 ppm PL) as a reference, the time difference between times-of-flight (ToF) was selected as the key dependent variable. This parameter was estimated using a cross-correlation function enhanced by the Hilbert transform to improve precision for closely spaced signals. The results demonstrate that both ultrasonic velocity and attenuation are sensitive to PL concentration. Waves propagated faster in refined oil, with measurable time differences δ observed for PL concentrations between 15 ppm and 325 ppm. Signal amplitude decreased with increasing PL content. Furthermore, the time difference δ increased at higher temperatures, confirming the need for controlled thermal conditions. These findings confirm the high potential of ultrasound for rapid, in-line monitoring of the degumming process.