Residues from the production of apple juice still contain a high level of polyphenolic compounds. Aim of this work was to test an extraction system based on the use of ultrasounds in order to recover these compounds. The tests were effected using water as a solvent and varying the intensity of ultrasounds (between 0.43 and 0.76 W/cm2), temperature (between 10 and 40° C) and sonication time (between 5 and 55 min). In contrast, the solid/liquid ratio was kept constant and equal to 150 mg/mL. The obtained data, subjected to statistical analysis by response surface methodology, show that the optimum extracting conditions require using 40° C temperature, 40 min process time and 0.76 W/cm2 ultrasound intensity. The authors point out that in these conditions sonic methodology provides extracts with 30% higher polyphenolic content than that determined in extracts obtained with traditional solvent extraction. In addition, with respect to the latter, sonic samples have much higher antioxidant power which allows concluding that the proposed methodology doesn’t only maximize process yields, but it also reduces the degradation phenomena that take place during traditional extraction processes.
D. Pingret et al., Journal of Food Engineering, 111, 2012, 73-81