Concentrated must is a natural sweetener in wine production, and in addition, it is a vitamin- and aroma-rich drink. In this study the basis of a complex membrane process was developed for must concentration. Modeling the experimental results and using recent economic data, the optimal process parameters were calculated to produce 45degrees Brix sugar concentration in the retentate, which saves the must without preservatives. The costs of the membrane process were compared with those of traditional evaporation.