Multi-step membrane processes for the concentration of grape juice

Grape production and viticulture have great traditions in Hungary. Nowadays wine-making is only profitable if the end-product is quality wine. Good-quality wine can be produced from must which has the proper high sugar content. If there is an unfavorable vintage, it is necessary to enrich the must, to increase its sugar content and to eliminate its other defects. Grape juice is not only a sweetener; it can be used for other purposes too because the juice of the grape is a pleasant, fashionable soft drink as well. However, the must storage can cause some difficulties, as fermentation starts easily. The aim of the investigations was to use osmotic distillation and membrane distillation after the microfiltration and reverse osmosis concentration [1] for water removal from grape juice in order to reach a high sugar content, to the extent that makes it possible to preserve the grape juice without cooling.