Ultrasound assisted extraction and nanofiltration of phenolic compounds from artichoke solid wastes

• Ultrasound of 20 kHz was used to extract phenolics from artichoke waste (bracts).
• Total phenols and chlorogenic acid were concentrated by nanofiltration.
• Permeate fluxes and fouling were influenced by alcoholic content of extract.
• Hermia's models and surface analyses identified the membrane more susceptible to fouling.
• Membrane selection was done in terms of flux, fouling behavior and phenols retention.

Artichoke wastes from the canning industry are rich in phenolic compounds, which can be used as food additives. This study aims to evaluate the potential of sequential process based on the use of ultrasound extraction and membrane technology for phenolic recovery. In the extraction step, solvent composition and ultrasound power were evaluated to understand their impact on phenolic content and antioxidant capacity. The highest yields were observed for extracts with higher ethanol content (50 and 75%). Therefore, these extracts were selected for concentration by nanofiltration in a tangential module, using differents membranes (NF270, DK and DL). The flux decrease and the phenolic retention were evaluated. Hermia's models and membrane surface characterization were used to investigate the fouling. The highest flux was observed for extracts with 50% of ethanol with a retention of chlorogenic acid higher than 95%. DK membrane showed to be less susceptible to fouling, although the cake formation occurred in all evaluated membranes. The most suitable process condition to obtain the highest phenolic yields was extraction with 50% ethanol and an ultrasound power of 240 W and extracts nanofiltration using DK membrane.