Process Intensification of Anthocyanin Recovery and Fouling Mitigation from Blueberry Pomace via Ultrasound-Integrated Membrane Processing

This study evaluated the performance of ultrasound-assisted membrane processes for the recovery of anthocyanins from blueberry pomace extract (BPE). Ultrasound was applied both as a pretreatment and as an integrated assistance during ultrafiltration (UF) to improve membrane performance and bioactive compound recovery. Prior to UF, microfiltration (MF) was applied to untreated BPE, during which permeate flux declined by 85%; ultrasound pretreatment reduced this decline to 79.4%, indicating mitigation of early-stage fouling. In UF systems, ultrasound pretreatment (US-pretreatment) increased the initial permeate flux by 8.83% in UF and by 35% in ultrasound-assisted UF (UA-UF). Total resistance was highest for UF of untreated BPE and lowest for UA-UF of US-pretreated BPE, while ultrasound integration reduced cake layer resistance by up to 37%. US-pretreatment significantly enhanced total phenolic, flavonoid, and monomeric anthocyanin contents of BPE (p < 0.05). Permeate fractions also exhibited improved bioactive compound transmission, with total phenolic content and DPPH antioxidant capacity in UA-UF permeates increasing by 12.7% and 8.96%, respectively, compared to UF. HPLC analysis confirmed that US-pretreatment increased total anthocyanin recovery without altering the relative anthocyanin profile. Antioxidant evaluation revealed assay-dependent responses, with ABTS showing more pronounced enhancement than DPPH, reflecting mechanistic differences in radical scavenging behavior. Overall, the synergistic application of US-pretreatment and membrane processing improved extraction efficiency, reduced fouling development, and enhanced permeate enrichment. These findings demonstrate the potential of ultrasound-assisted membrane technology as a sustainable strategy for valorizing berry processing by-products into anthocyanin-rich functional ingredients.