The oil was placed in a 500 mL round bottom flask and mixed with an alcoholic solution of KOH (30 g L−1). The mixture sonicated for 30 min in an ultrasonic bath (40 kHz, 160 W) operating at ambient temperature. After the saponification reaction, the mixture was acidified with a H2SO4 solution (volumetric fraction of 27%) and transferred to a separating funnel. The aqueous layer was discarded and the supernatant containing the free fatty acids was heated at 110 °C until total dehumidification.