Does the ultrasonic field improve the extraction productivity compared to classical methods – Maceration and reflux distillation?

• Ultrasonic-assisted extraction, maceration and solvent reflux distillation were used to obtain the rapeseed oil. • The experimental design was carried out, using the full factorial matrix technique. • The effects of the rapeseed to hexane mass ratio, extraction time and percentage of the available US power upon the extraction process were studied. • A thorough comparison of the ultrasonic-assisted extraction, maceration and solvent reflux distillation techniques was done, using several metrics. Rapeseed oil consists of a blend of high-quality lipid acids, which is consumed by the food and nutrition industry and other clients in general. Ultrasonic-assisted extraction, as an unconventional method of introducing the energy needed into the system, maceration and solvent reflux distillation were used to obtain the rapeseed oil. The results obtained were compared in terms of yield productivity and specific energy. The experimental design was carried out using the full factorial matrix technique, while the response surface methodology was applied to find the optimum operating conditions giving the highest extract concentration. Effects of the solid-solvent mass ratio, extraction time and ultrasound intensity field on the extraction yield were studied. Good results were obtained after 5 min of ultrasonic-assisted extraction time, 80% ultrasonic-assisted power and 1:6 molar ratio, when the extraction yield (19.2 ± 0.04%) is much higher compared to the two conventional methods. A thorough comparison of the ultrasonic-assisted extraction, maceration and solvent reflux distillation techniques was done. Using a new metric (energy productivity), maceration performs remarkably well, proving to be a serious competitor to ultrasonic-assisted extraction, because good results can be obtained without very large investments and difficult to solve scale-up problems, implied by ultrasonic-assisted extraction.