In which, \({FFA(\%)}_{\text{Initial}}\) is the initial acidity of the Crambe oil.

The effects of the mass ratio of buffer solution/oil (B/O), catalyst/substrate (C/S), and ultrasound power (Po) were assessed through the use of a Central Composite Rotational Design (CCRD) with central and axial points, the values of the design were determined after preliminary experiments. Seventeen essays were performed for each design, with three replicates on the central point, and six experiments of axial points. The variable levels of the CCRD for in natura seeds were: ultrasound power of 31.40%, 45.0%, 65.0%, 85.0%; and 98.64%; B/O mass ratio 0.07, 0.45, 1.00, 1.55, and 1.93; and C/S mass ratio of 0.01, 0.07, 0.16, 0.25, and 0.31. For the oil-free seed particles: 31.40%, 45.0%, 65.0%, 85.0%, and 98.64% for ultrasound power; 1.13, 1.40, 1.80, 2.20, and 2.47 for the B/O mass ratio; and 0.010, 0.020, 0.035, 0.050, and 0.060 for C/S mass ratio. All the experiments were carried out for three minutes. The response of the experimental design was the hydrolysis yield, analyzed through the software Statistica version 7.0 (StatSoft Inc., USA). The validation of the model was performed with the software Maple version 13.0 (Waterloo Maple Inc., Canada).

Kinetic experiments were performed at the conditions of higher yield obtained during the CCRD experiments, where for each reaction time, a different test was performed. Additional experiments were performed in a refrigerated incubator with agitation (shaker) at room temperature and 140 rpm.