Where m is the sample oil mass (g), \(V\) is the volume of
NaOH solution used in the titration (L), \(M_{\text{NaOH}}\) is the NaOH
solution molarity (mol L-1) and\(\text{MM}_{\text{FFA}}\) is the average molar mass of fatty acids in
Crambe oil. The average molar mass of fatty acids in Crambe oil is
317.98 g mol-1, and it was determined in previous work
(Tavares et al., 2018b) performed by the same group.
2.4. Quantification of
Acylglycerols
Analysis of Nuclear Magnetic Resonance (NMR) was performed to determine
the concentration of acylglycerols and the methodology is described
elsewhere (Tavares et al., 2018a).
2.5. Hydrolysis Reactions
The reactions were carried out in a 50 mL Erlenmeyer sonicated using an
Ultronique ultrasound, microtip probe of 4 mm diameter, model disruptor,
maximum power of 500 W. Additional experiments were performed in a
refrigerated incubator with agitation (shaker) at room temperature and
140 rpm.
During preliminary tests, it was observed that after 5 minutes of
sonication, the viscosity of the medium started to increase, affecting
the cavitation phenomenon. The temperature of the mixture was increasing
(more than 40°C), which could be damaging for the reaction and the
equipment. Therefore, for the factorial design experiments, a time of 3
minutes was chosen. A fixed volume of 25 cm3 of water
and oil solution (acetate buffer solution; 0.2 M, pH 4.2) was used. The
buffer solution pH and concentration were determined based on
preliminaries studies performed by the same research group (TAVARES et
al., 2015).
After the reaction time, the resulting hydrolyzed oil emulsion was
centrifuged for 20 minutes at 3000 rpm, and then a sample of
approximately 1g of oil was collected and analyzed. The hydrolysis yield
was calculated by Equation 2 .