Forward osmosis for the concentration of sugarcane juice

During evaporation, the loss of sucrose can occur due to acid-catalysed hydrolysis to glucose and fructose, a reaction that is exponential with temperature. This paper reviews non-thermal methods for concentrating juices, mainly focusing on the developments of forward osmosis (FO) membranes for juice processing, detailing the benefits and limitations of this technology. A laboratory FO membrane was used in this preliminary study to concentrate pure sucrose solutions and clarified juice from ~10 to 45% rds using a calcium chloride draw solution. A small amount of reverse salt flux was observed. The non-sucrose substances in factory juices had little impact on flux performance, with the flux reducing inversely with the volumetric concentration factor. By concentrating to a limit of 45% rds, concentration polarisation factors that can have a detrimental impact on the flux were not realised. Possible strategies were also explored for the integration into the sugar-manufacturing process.