How Does it Work?

The wine to be treated is circulated at high pressure through a reverse osmosis plant to separate a flow of permeate which contains water, alcohol and some of the acetic acid and ethyl acetate to be removed. This is then treated in an anion exchange column where the acetic acid is adsorbed on the charged resin. The treated permeate with the volatile acidity removed is recombined with the bulk of the wine concentrate and returned to tank.

Critical to the success of the Memstar VA reduction process is the use of highly selective reverse osmosis membranes operating under optimum conditions of temperature and pressure. In this application, processing at high pressure (up to 70 bar) is preferable because the membranes perform more selectively than at lower pressure.

This means that virtually none of the desirable wine components (the other acids, anions, sugars, tannins, flavour and colour) pass through the membrane but are retained in the concentrate. They do not come into contact with the ion exchange resin so they cannot be absorbed or contaminated. Very little other acid is lost. Nothing is added to the wine and the volume and alcohol content are not affected.

The process continues for as long as necessary to reduce the volatile acidity to the level desired by the winemaker.

Winemakers' Questions concerning Memstar processes