Concentration of red orange juice by osmotic distillation: effect of operating conditions on water transport

The concentration of fruit juices reduces the volume with consequent reduction of transport, storage and packaging costs. In addition, the concentrates are more stable, presenting higher resistance to microbial and chemical deterioration than the original juice as a result of water activity reduction. The traditional concentration of fruit juices is usually performed by multistage vacuum evaporation processes, in which the water is removed at high temperatures. However, high-energy consumption, color changes and reduction of nutritional value due to thermal effects are main drawbacks of traditional evaporation processes. Membrane concentration processes such as reverse osmosis (RO), membrane distillation (MD) and osmotic distillation (OD) are able to overcome some of the problems associated with thermal evaporation. In particular, the concentration of fruit juices by OD has been investigated by many Authors on laboratory or industrial pilot scale. These studies often report results concerning the quality of the final concentrate and the performance of the process in terms of evaporation fluxes in comparison with other traditional concentration processes and membrane process such as reverse osmosis and membrane distillation. This study was undertaken in order to study the effect of operating conditions such as feed concentration, feed velocity, feed temperature, brine concentration and brine velocity on water transport during the concentration of red orange juice. Experimental results were compared with those reported in literature for model solutions such as aqueous glucose and sucrose solutions and real systems.