Recovery of residual oil from canola meal by ultrasound-assisted extraction, using a green solvent: influence of process variables

Canola oil ranks among the most widely consumed vegetable oils worldwide, and its industrial production yields byproducts with considerable valorization potential. Residual oil retained in canola meal after mechanical pressing is conventionally recovered using hexane extraction, a method associated with environmental and occupational health concerns. This work aimed to develop a sustainable alternative for residual oil recovery .

Seeds were subjected to hydrothermal pretreatment (autoclave steam, 130 °C, 5 min) followed by microwave conditioning (2450 MHz, 5 min). Ultrasound-assisted extraction was then performed using a probe sonicator (VCS-500, Sonics & Materials, USA) with isopropanol as the extraction solvent. The effects of ultrasound amplitude (25–75%) and solid-to-solvent ratio (1:17–1:34) were assessed at fixed extraction time (60 min) and temperature (60 °C). Following each extraction, samples were centrifuged, filtered, and distilled to remove solvent and quantify total extract yield. A hexane wash followed by a second distillation step was applied to isolate and quantify the solvent-free lipid fraction.

ANOVA combined with Tukey's post-hoc test identified 50% amplitude and a 1:22 solid-to-solvent ratio as the best performing conditions, yielding 74% lipid recovery. Increasing ultrasound amplitude significantly increased oil recovery, while solid-to-solvent ratios between 1:22 and 1:28 consistently produced the highest extraction yields. No significant differences in total extract yield were observed across treatments, suggesting that the evaluated process variables selectively affected lipid extraction without significantly altering total extract recovery. The results highlight the potential of ultrasound-assisted extraction to improve residual oil recovery from canola meal while reducing reliance on conventional hexane-based processes.