Glossary

Reverse osmosis

What it is

Wine pushed against a dense semi-permeable filter (pores on the order of 0.1-1 nm) under pressure: that is reverse osmosis (RO). Ethanol leaves together with water as liquid (permeate). Acids, tannins and colour stay, in essence, on the retentate side. The wine is not boiled.

It is not osmotic distillation. There the wine does not cross the membrane: ethanol crosses as vapour through hydrophobic pores, without high pressure. Mixing the two up is the most common error in sheets and press copy. Full method page: reverse osmosis.

When it fits

RO suits cellars that want to limit heat and protect phenolic structure or acidity, at the cost of managing the water that leaves with the alcohol (diafiltration: replace with suitable water and repeat cycles to the target strength). Aroma and texture still need attention: removing ethanol also moves volatiles and lightens mouthfeel. It serves both partial cuts (1-2 %) and, with more cycles, work down towards ≤ 0.5 % vol.

Treat the glossary entry as the short definition and the technology page as the worked explanation (diafiltration, hybrids, examples). Do not paste the full RO article into the glossary; link it.

Label / EU note

Regulation (EU) 2021/2117 lists it among “membrane techniques”, alongside nanofiltration and osmotic distillation. That authorises the family; it does not make the three interchangeable. Bottle wording follows category / shelf rules (dealcoholised, alcohol-free / 0.0%), not the equipment name.

See also