Modeling of gel layer transport duringultrafiltration of fruit juice with non-Newtonian fluid rheology

The rheology of fruit juice mixtures generally follows non-Newtonian behavior of powerlaw form. The clarification of fruit juices by membrane separation illustrates an exampleof enhancing the shelf life of a real fruit juice by removing degradable components. How-ever, the presence of high molecular weight proteins, pectins, polysaccharides, fibers, etc.,tends to form gel over the membrane during filtration causing fouling and affecting its per-formance. The proposed model developed from the first principle boundary layer analysis,describes the physical mass transport phenomena and quantifies the various extents offouling using different membrane materials and operating conditions. The model resultsare useful in understanding the complex solute-membrane interplay in fouling and canpredict the effect of gel layer thickness on the process throughput.In this work, the model results were validated experimentally in clarification of bloodorange juice in batch mode using two polysulphone (PS) membranes and polyacryloni-trile (PAN) membrane in hollow fiber configuration, with different molecular-weight-cut-off(MWCO). The results clearly indicated that PS membranes are more prone to fouling at higherpressures compared to PAN membrane. An increase in the feed flow rate had a significanteffect in reducing the growth of gel layer mainly in PS membranes.