Abstract: The invention concerns a product for adjusting the degree of alcohol of wines or alcoholic beverages. According to the invention, this process consists in resorting to two coupled reverse osmosis systems each comprising a tank for supplying the product to be processed upstream from a reverse osmosis cell, in equipping the two reverse osmosis cells P and I with membranes with a distinctly different permeability to ethanol, in withdrawing the permeate originating from said cell P, in sending it into said supply reservoir upstream from said cell I, in withdrawing the permeate originating from said cell I and in sending it into the supply tank upstream from cell P, whilst recovering the corresponding concentrates X and Y.