Effective clarification of pomegranate juice: A comparative study of pretreatment methods and their influence on ultrafiltration flux

The aim of this study was to introduce an effective pre-clarification step in order to improve performance of subsequent ultrafiltration (UF) and to obtain a high quality pomegranate juice (PJ) with improved clarity. The effects of various pre-clarification treatments utilizing gelatin, bentonite and polyvinyl polypyrrolidone (PVPP) on UF performance were evaluated comparatively through analysis of flux behavior and membrane fouling. Quality attributes of the PJs (pH, total acidity, total phenolic content, total monomeric anthocyanins, individual phenolic acids, organic acids, total antioxidant activity and color characteristics) following various pre-clarification treatments were also investigated. On the whole, pre-clarification treatments that included PVPP exhibited a higher overall adsorption capacity, especially of low molecular weight phenolics. The best results with regard to both the fouling behavior of the UF membrane and the juice clarity were achieved by sequential application of PVPP and bentonite. Since lesser amounts of fining agents were used in the pre-clarification treatments, quality attributes of PJ were well preserved comparing conventional clarification applications.