Orange (Citrus sinensis) juice concentration by reverse osmosis

Single strength orange juice was concentrated by reverse osmosis in a plate and frame pilot plant with 0.72 m2 of filtration area. Three transmembrane pressures, 20, 40 and 60 bar, were evaluated and concentration factors of 2.3, 3.8 and 5.8 were obtained. At these transmembrane pressures the final soluble solids contents were of 16, 28 and 36 °Brix, respectively. The vitamin C content increased from 29.3 mg ascorbic acid/100 g (single strength juice) to 53.9, 82.7 and 101.1 mg/100 g, in the concentrated juices obtained at 20, 40 and 60 bar, respectively. Simulating the continuous process, the permeate flux was 28 L/h m2 when the transmembrane pressure was 60 bar, while the processes carried out at 40 and 20 bar, presented, respectively, 20 and 11 L/h m2. The sensory evaluation of the reconstituted juice obtained by dilution of the concentrated juice showed that this product had lost its characteristic aroma and flavour when compared to the fresh orange juice. In a second experiment, some sensory attributes were evaluated in the reconstituted juice obtained by two concentration processes: reverse osmosis and thermal evaporation. The juice from reverse osmosis process had a best preserved flavour. It was concluded that it is feasible to concentrate orange juice by reverse osmosis, maintaining its sensory and nutritional characteristics.