Reverse osmosis
No heat: pressure and a membrane to pull ethanol and water, then diafiltration with water to get under 0.5% ABV.
- Volume loss
- Minimal (<5%); volume is put back with RO water
- Final ABV
- As low as <0.5%
- Best for
- Delicate wines where acidity and phenolics must stay intact, and aroma can be recovered in a separate step.
What it is
Membranes do not boil the wine: they push it under pressure against a selective filter. Ethanol and water go through; acids, tannins and colour stay. That is the point when structure matters and heat is off the table. Aroma and texture still need watching.
The usual pairing is reverse osmosis plus diafiltration.
Reverse osmosis
Under high pressure, small molecules (ethanol, water) leave as permeate. What does not cross — the retentate — is almost the whole wine minus alcohol and water, and becomes the no-alcohol base.
Diafiltration
RO water is added back to the retentate to wash out more ethanol and restore volume. Filter then dilute, and ABV can fall below 0.5% without heat.
The matrix is treated gently. The nose can fade unless aroma is recovered somewhere else. One pass is rarely enough: the cycle is repeated until the target strength.