The fouling of ultrafiltration membranes during the fractionation of phytosterols from orange juice

Nurul Hainiza Abd Razak, Yong-Min Chew, Michael Bird

Research output: Contribution to conferencePaper


Ultrafiltration (UF) offers the possibility of separating bioactive compounds from by-products of agro-industrial applications. Plant bioactive compounds such as phytosterols are well known for their health benefits, including the lowering of blood cholesterol levels and a decreased risk of developing coronary heart disease. Natural rubber serum (NRS) contains phytosterols which have a great potential to be used as an alternative source for the nutraceutical industry. Orange juice was selected as a model solution to NRS due to the presence of a similar profile of bioactive compounds. The aim of this study is to separate phytosterol compounds from orange juice using UF. Flat sheet UF membranes (Alfa Laval) with molecular weight cut-off (MWCO) values of 10 kDa fabricated from regenerated cellulose (code RC70PP), polyethersulfone (code GR80PP) and fluoropolymer (code ETNA10PP) were tested to determine the feasibility of isolation of phytosterols. The experiments were performed in a cross flow filtration rig at a transmembrane pressure (TMP) range of 0.5 - 2 bar, and a cross flow velocity (CFV) range of 0.5 - 1.5 m s-1, and at an ambient temperature. Total phytosterol content was analysed using a Liebermann-Burchard based assay. Permeate flux and fouling index was determined. Membrane rejection towards total phytosterols, proteins and sugars was determined, along with antioxidant activity. The regenerated cellulose membrane displayed the highest permeate flux of those tested (22 L/m2 h), along with a higher fouling index (100%) and a good separation efficiency of phytosterols (45% rejection towards phytosterols) from orange juice. Although the yield of phytosterols was relatively low (40 mg/L), there is potential to modify the filtration process and optimise the analysis procedure to produce a greater amount of phytosterols. However, fouling limits the filtration process, and understanding the nature of fouling will be the key to determining the viability of the technology. The effects of cleaning agent upon the restoration of permeate flux is also reported. All membranes investigated displayed cleaning efficiencies of > 95%.
Original languageEnglish
Publication statusPublished - 17 Apr 2018


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