THE USE OF MEMBRANE PROCESSES IN THE CLARIFICATION OF ORANGE AND LEMON JUICES

The ultrafiltration of orange and lemon juices has been investigated on a pilot-plant scale at constant concentration using tubular configuration polymeric and ceramic membranes. The permeate fluxes were found to be strongly dependent on the tangential feed velocity at the membrane but almost independent of the driving force at average pressures over the membrane greater than almost-equal-to 0.2 MPa. These results are due to the formation of a pectin-pulp deposit on the membrane, which effectively controls the ultrafiltration. Because of their different surface structures and roughness this deposit has different properties for the ceramic and polymeric membranes. This causes the latter to behave as rough tubes. The ceramic membranes give higher permeate fluxes at a lower Reynolds number than the polymeric membranes. This and their smooth tube behaviour indicate the possibility of greater energy efficiency for the industrial application of the ceramic than of the polymeric membranes.