Reconcentration of spent solutions from osmotic dehydration using direct osmosis in two configurations Original Research Article

The main objective of the present study is to evaluate direct osmosis as a process to reconcentrate osmotic dehydration spent solutions. The reconcentration is performed using two modes: off-site (during which osmotic and stripping solutions are brought into contact in a membrane module) and on-site direct osmosis (the osmotic solution is reconcentrated at the same time as the osmotic dehydration process takes place). During the off-site direct osmosis Desal5-DK membrane performed the best, giving for 40, 50 and 60 °Brix fluxes of 3, 1.9, 1.7 kg/m2 h, respectively, first because of its properties and, second, because it is not very thick, which reduces the mass transfer resistance between the solutions. The low water fluxes obtained when on-site direct osmosis was used (0.06 and 0.023 for 40 and 50 °Brix, respectively), can be attributed mainly to the low driving force and problems related to stirring and the design of the membrane support. The apples osmodehydrated during the on-site direct osmosis were used in the sensory analysis. The panellists indicated that the apples that were osmodehydrated using the reconcentrated solution had best overall taste.