Despite the fact that the above combined scheme appears to be very attractive, the separation of the juice into two fractions seems to negatively affect the rheological characteristics of the juice concentrate (Pepper et al., 1985).
The problems encountered with the abovementioned processing schemes (which have reverse osmosis as a core process) have not permitted their application on a commercial scale.
From the range of the above-mentioned process schemes, only plain reverse osmosis has had a commercial folloeup, strictly for the pre-concentration of fruit juices and tomato juice.
On top of quality problems, the complexity of combined process schemes has probably prohibited their commercial application in place of conventional vacuum evaporation.
A potential solution to the above problems and an attractive alternative to evaporative concentration could be offered by a purely osmotic technique.
This paper is an effort to review the research developments with regard to these techniques, namely, direct osmosis, membrane distillation and osmotic distillation.