Effect of enzymatic pretreatment and different fluxes on membrane fouling resistances during sour cherry juice filtration

Sour cherry juice is a popular fruit juice known for its high phenolic content and associated health benefits. However, effective clarification and processing remain challenging due to the complexity of conventional multi-step methods. Membrane-based processing offers advantages but is hindered by membrane fouling, which involves complex mechanisms. This study investigates the effect of enzymatic pretreatment on membrane fouling during sour cherry juice clarification at different permeate fluxes. Juice with and without pectinase pretreatment was filtered through a flat-sheet polyethersulfone microfiltration membrane at fluxes ranging from 8 to 52 L m−2 h−1. Microfiltration was performed using a submerged 0.4 μm PES flat-sheet membrane at a transmembrane pressure of 0.03–0.35 bar. Total hydraulic resistance was analyzed using Darcy’s law and divided into cake (RC), pore blocking (RP), and fluid (RF) resistances. A multi-scale model incorporating pore blocking and cake parameters was optimized with experimental data to characterize fouling. RC dominated at high fluxes regardless of pretreatment, while enzymatic pretreatment significantly reduced RF and increased RP. Flux was the primary driver of all resistances (p < 0.05), with pretreatment affecting only RP and RF. The model effectively captured the contrasting trends of cake formation and pore blockage, with R2 values of 0.99 (without enzyme) and 0.82 (with enzyme). Optimized parameters support more efficient, sustainable clarification of sour cherry juice.