Clarification of aronia juice with polyethersulfone (PES) ultrafiltration membranes and investigation of membrane fouling mechanisms

Aronia fruit is known as one of the fruits with rich anthocyanin content. Bioactive components found in aronia have various positive effects on human health. The fact that the fruit has a bitter astringent taste makes it difficult to consume fresh and various alternative production techniques are needed. This study was carried out to obtain clear aronia juice and it was aimed to make the production process more efficient by using ultrafiltration membrane technique. Within the scope of the study, the flux profiles and fouling mechanisms of two different commercial ultrafiltration membranes with different polymeric structures and pore sizes during clarification of aronia juice were examined. The performance of the system was evaluated on the basis of flux profile for 150 kDa PES and 50 kDa PESH UF membranes at different operating parameters and the optimum operating conditions were determined by considering the maximum critical permeate flux and minimum fouling data. In the studies carried out in total recycle mode, the flux decrease in the 50 kDa PESH membrane was less and the critical flux value was reached faster. In batch mode, UF process was performed using PES and PESH membranes at 600 ml/min flow rate and 3 bar TMP conditions. When the hydraulic permeability data were examined in membrane cleaning procedures, it was observed that the 50 kDa PESH membrane was less fouled due to its hydrophilic structure. The fouling data recorded during the study were interpreted using the Resistance in Series and Field models. In the Resistance in Series model, the 50 kDa membrane showed higher total resistance and lower fouling resistance, while in the Field model, the formation of a cake layer, which is a reversible fouling in the same membrane, was determined as the dominant mechanism. The permeate and retentate samples were then subjected to general quality analyses and the results were evaluated in comparison with the pretreated control sample. In all quality control analyses, higher values were obtained for the 50 kDa membrane compared to the 150 kDa membrane and closer to the control sample. As a result of all the studies, more efficient results were obtained with the hydrophilic 50 kDa PESH membrane in terms of fouling behavior and final product quality.