Ultrasound-assisted recirculation extraction as an innovative approach for obtaining bioactive compounds from grape pomace.

BACKGROUND

Grape pomace, a by-product generated during winemaking, still retains bioactive compounds with potential applications in the food, pharmaceutical and nutraceutical sectors. This work investigated ultrasound-assisted extraction (UAE) coupled with a recirculation system as a strategy to improve their recovery. The effects of pump speed (909-1864 min-1) and ultrasound power (80-360 W) on phenolic content, monomeric anthocyanins and antioxidant capacity were assessed. Extractions were performed using ethanol-water solution (500 mL L-1 ethanol) at a solid-liquid ratio of 50 g L-1 and kinetic assays established 90 min as the optimal extraction time.

RESULTS

Total phenolic content varied from 8.55 ± 0.15 to 14.04 ± 0.14 g gallic acid equivalent kg-1. Antioxidant capacity varied between 10.11-18.31 g Trolox kg-1 [2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid)] and 7.32-12.90 g Trolox kg-1 (2,2-diphenyl-1-picrylhydrazyl), whereas monomeric anthocyanins varied from 0.149 ± 0.006 to 0.236 ± 0.002 g malvidin-3-O-glucoside kg-1. Ultrasound power significantly enhanced extraction efficiency as a result of intensified cavitation, whereas pump speed showed a synergistic effect at high power. Optimal conditions were established at 1725 min-1 and 320 W. The optimized system achieved greater extraction yields compared to conventional extraction, along with improved antioxidant capacity. Major phenolic compounds identified included gallic, vanillic and protocatechuic acids, catechin, epicatechin, p-coumaric acid, quercetin, and ellagic acid, with malvidin-3-O-glucoside as the predominant anthocyanin.

CONCLUSION

UAE combined with recirculation proved to be a suitable process with scale-up potential, enhancing extraction kinetics and bioactive compound recovery, supporting its application in grape pomace valorization. © 2026 The Author(s). Journal of the Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.