Apple juice concentration using submerged direct contact membrane distillation (SDCMD)

The applicability of SDCMD technology using polypropylene membrane for apple juice concentration was explored in this study. The effect of feed temperature, draw solution flowrate, and draw solution concentration against the permeate flux and nutrient content were investigated. The results suggested a noticeable trade-off between the permeate flux and nutrient content. Severe temperature polarization was occurred during the SDCMD operation due to poor feed hydrodynamic and mixing condition in submerged configuration with stagnant feed. Therefore, the temperature difference of the feed and draw solution flow resulted on negligible driving force. The optimum SDCMD operation condition for apple juice concentration in this study were 3 mL/s draw solution flowrate, 630 g/L draw solution concentration, 14 °C draw solution temperature and 30 °C feed temperature. To avoid excessive heat treatment and prolong operation time, the advantage of membrane modularity was highlighted. Apple juice concentration to up to 35oBrix could be achieved with excellent nutrient preservation.