Osmotic evaporation (OE) was applied to grape juice to increase the sugar content and thus to
improve the quality of wine obtained after fermentation. The use of aqueous solutions of glycerol as extractant
avoids corrosion and scaling, which are the main problems in OE with brines. Preliminary experiments were
performed on lab scale using water or glucose solutions as feed, and NaCl or glycerol as extractant. The runs
with NaCl allowed measurement of the membrane transport properties, whereas glycerol was used to quantify
the concentration polarization phenomena involved. The extract side concentration polarization severely limited
the flux achievable for glycerol concentration above 50% wt, while the extract side concentration was negligible
in the OE with NaCl. The feed side concentration polarization played a minor role for glucose content up to 40%
wt. Experiments with grape juice were performed on pilot scale equipped with plate and frame modules. The
performance were in good agreement with lab results on glucose model solutions, the lower flux observed was
due only to the low temperature of operation. The process was tested on 3 types of grape juice (white, roseĢ, and
red). Treated and control juices were fermented, and corresponding wines were analyzed for selected parameters
and evaluated by sensory analysis. The OE treatment removed water from grape juice and increased both the total
soluble solids and sugar content of juice, thus ethanol content and dry extract in wine always increased. The
osmotic evaporation significantly improved sensory quality of red wine that was judged as having a full body,
more structure, and persistence.
