Effect of the operating variables on the extraction and recovery of aroma compounds in an osmotic distillation process coupled to a vacuum membrane distillation system

The coupled operation of osmotic distillation (OD) and vacuum membrane distillation (VMD) for concentration of fruit juices and simultaneous recovery of their aroma compounds was studied. The simulated aqueous fruit juices containing four common aroma compounds were concentrated using osmotic distillation where the feed solution was in contact with a brine solution of CaCl2, through a hydrophobic macroporous membrane contactor. Aroma compounds absorbed in the extraction brine were extracted using a membrane evaporator under vacuum and collected into a cold trap. This way, both concentration and aroma recovery of fruit juices were achieved simultaneously using two hollow fiber membrane modules. The transfer of the aroma compounds was evaluated by using different operating variables such as hydrodynamic conditions, brine concentration and vacuum pressure. The experiments show that the loss of aroma compounds during the concentration processes can be avoided by means of extraction of the aroma compounds from the brine separately, resulting in an average of 75% recovery in aroma compounds. In general, the process of aroma removal and recovery is faster than the concentration process of the fruit juices by osmotic distillation at a technical and commercial level (higher than 45 degrees Brix). Thus, the simultaneous operation of these two membrane processes can be used to decrease the energy requirements for a given production capacity. (C) 2012 Elsevier Ltd. All rights reserved.