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

Abstract

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% NaCl rejection. The average permeate flux obtained were between 18 and 50 kg h −1 m −2 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 μm. 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.