Evaluation of reverse osmosis and osmotic evaporation to concentrate camu-camu juice (Myrciaria dubia)

This study presents a first evaluation of the potential of two membrane processes for the production of concentrated camu-camu juice with high vitamin C content. A clarified camu-camu juice at around 64 g kg-1 of total soluble solids (TSS) with an average ascorbic acid content of 11 g kg-1 was subsequently concentrated by reverse osmosis and osmotic evaporation at low temperature (20-35°C). Reverse osmosis trials were carried out in a pilot scale equipment, using a composite film membrane with 95% NaCI rejection. The average permeate flux obtained were between 18 and 50 kg h` m' depending on the transmembrane pressure used. The maximum total soluble solids content reached was 255 g kg-1 at 60 bar and the ascorbic acid losses were between 8% and 18%. Osmotic evaporation trials were carried out using a laboratory unit with a PTFE flat sheet membrane with an average pore diameter of 0.2 gm. In that case, the juice was concentrated in two steps, the first concentrating the juice up to 250 g kg-1 TSS, and the second from 250 to 640 g kg-1 TSS. The difference in temperature between the juice and the brine had a great influence on the evaporation rate. The higher average evaporating flux obtained was 12 kg h-1 m-2. For all experiments, the ascorbic acid losses were about 3% that indicated the efficiency of the process in maintaining the nutritional quality of the juice regarding vitamin C content. These two membrane concentration processes are very interesting for the concentration of camu-camu juice. The low concentration level that can be reached is the major drawback of reverse osmosis. Osmotic evaporation allows to produce a concentrate with more than 10% of ascorbic acid. (Résumé d'auteur