Investigations on membrane performance for coconut water concentration under pressure and by osmotically driven process.

Abstract

BACKGROUND: Coconut water has grown in popularity among people as a ready-to-drink healthy beverage. Nevertheless, its future export expansion is restricted by high operating costs as large volumes of coconut water have to be handled during exporting and for its storage. Besides, large coconut water volumes also consume high energy during the pasteurization/sterilization process. Thus, in this work, we evaluated the potential of employing polymeric membranes for the concentration of coconut water at room temperature via either a pressure-driven or osmotically driven process. RESULTS: Our results indicated that the membrane that was tested under reverse osmosis (RO) mode at 25 bar could significantly concentrate coconut water by reducing its original volume by up to half, with negligible loss of ions/minerals. Upon completion of the RO process, Brix and conductivity of the coconut water were increased by 90% and 61.4%, respectively. As a comparison, the membrane tested under pressure-retarded osmosis (PRO) mode was only able to reduce the volume of coconut water by ~12%. Although coconut water concentration via PRO operation does not require an external driving force, this process suffers from several significant drawbacks, including reverse draw solute flux and the requirement for draw solution generation. CONCLUSION: Based on the results obtained, it can be concluded that the RO membrane process is still the most reliable and practical method of concentrating fruit juice, and its performance could be further enhanced using a high-flux polymeric membrane or through process optimization.