Potassium hydroxide was completely dissolved in MeOH under stirring in a glass batch reactor equipped with mechanic stirrer. Then the vegetable oil was added into the reactor and the reaction mixture was maintained under stirring at 5000 rpm for 2 h at room temperature (23 ± 1 °C). For the dende oil the mixture was stirred during 4 h due to its higher viscosity. Table 1 displays the reaction conditions for the transesterification reactions, considering the mass ratio of 100:33:1 (vegetable oil:MeOH:KOH). After 2 h (4 h for dende oil) for the reaction completion the mixture was allowed to stand and the two phases (one rich in glycerin and the other one in methyl ester) were separated. The excess of methanol in the methyl ester phase was removed by rotary evaporation at 70 °C. The methyl ester was then washed twice with a phosphoric acid water solution (5%, v/v) and with brine until a clear phase (methyl ester) was obtained. The methyl esters were analyzed by GC on a Shimadzu GC-17A chromatograph with flame ionization detector, equipped with a polydimethylsiloxane column (CBPI PRONA-M50-042) 50 m, 0.15 mm i.d. and film thickness of 0.2 μm, working between 60 and 110 °C, at a heating rate of 10 °C min−1, standing at the final temperature for 5 min. The injector and detector temperatures were 250 °C. The methyl esters content in the reaction product was determined using dibutyl phthalate as internal standard. The reaction was repeated two or three times until purity of more than 99 mass% in methyl esters were detected by CG. It is worth mentioning that for the consecutive reactions a similar procedure was followed, using the reaction product instead of vegetable oil as reagent and the same amounts of methanol and KOH. The methyl esters were finally stored in amber flasks in a refrigerator at 6 °C.