Radish seed oil: Ultrasound-assisted extraction using ethanol as solvent and assessment of its potential for ester production

In this study, the ultrasound-assisted extraction (UAE) of radish seed oil (RSO) using ethanol as the solvent was investigated with the aim of ester synthesis by in situ reaction. An experimental design was used to evaluate the effects of temperature, solvent to seed ratio and time on the efficiency of the UAE method and to enable the determination of the conditions that maximize the oil removal. The results were compared to those obtained with the classical extraction method, using ethanol and n-hexane as solvents, in terms of yield and oil characterization. The in situ reaction using the oil obtained by UAE was conducted applying different reaction times and enzyme loadings. The effect of using ultrasonic irradiation in the oil extraction and the in situ reaction was evaluated. The results showed that, under the conditions evaluated, the temperature had the greatest influence on the oil extraction, the maximum yield ((similar to)25%) being obtained at 60 degrees C, with a solvent to seed ratio of 12 mL g(-1) and extraction time of 60 min. This corresponds to 89% of the yield obtained by the classical method using n-hexane. The RSO was predominantly composed of oleic and erucic acids. The UAE allowed the extraction of a greater amount of phytosterols and tocopherols and, consequently, this oil presented greater oxidative stability. In addition, it was observed that the greater availability of the catalyst in the reaction medium favored the conversion of the oil to esters. The application of ultrasonic irradiation provided higher yields of the oil and ethyl esters.