Concentration of grape juice: Combined forward osmosis/evaporation versus conventional evaporation

The present study aimed to evaluate the process of forward osmosis (FO) for the concentration of grape juice using NaCl as the osmotic solution facing the thermal evaporation process, commonly used in industry. A combined experiment (FO + evaporation) was also performed to evaluate the potential of FO as a pre-concentration process. FO experiments were performed according to the Box-Behnken design. Some degree of concentration of the grape juice was obtained in all FO experimental runs, and it was observed a strong influence of the parameters studied on the fluxes. In the evaporation experiments, the quality of the final product was affected concerning the content of phenolic compounds, which have undergone significant degradation by heat. In the combined process, grape juice concentration to up to 65.7 degrees Brix could be achieved showing greater retention of quality factors and bioactive compounds, highlighting the advantage of FO and its potential as a pre-concentration step.