Beaudry and Lampi (1990a,b) and Herron et al. (1994) reported the use of a classic evaporator in order to re-concentrate the diluted osmotic medium.
In that way, it is only the (inert) osmotic medium (and not the liquid food) which is thermally processed.
The food concentrate retains the freshness of the raw material.
In addition to heat evaporation, some other approaches were tried for the concentration of the osmotic medium.
Thompson (1991) reported that solar ponding or even reverse osmosis and pervaporation could be used to re-concentrate osmotic media in order to restore their osmotic ability.
Petrotos et al. (2000) suggested the use of electrodialysis as the most suitable way to reinforce the osmotic NaCl brines which they used in their osmotic apparatus.
The latter method is well known to the chemical industry,especially in Japan, where electrodialysis is used to concentrate brines for certain chemical processes.
The main characteristic of the electrodialysis process is the extremely low energy
consumption (Lacey & Loeb, 1979) combined with high durability of the membranes, which
have a shelf-life of from six to ten years.