Vacuum rectification

A reduction of alcohol in wine can be achieved by means of various physical and/or chemical processes. This is a relatively common practice, especially in southern regions, with the aim of producing more aromatic and less alcoholic wines. The simplest and cheapest form is the addition of fruit juice or grape juice, which is used in the production of cooler, or of water (stretching). A certain alcohol content can also be achieved by stopping the fermentation by means of cooling, which is mainly practised in Italy for simple wines. The result is sweet, sparkling wines with low alcohol content. Thermal separation processes such as vacuum distillation (vacuum rectification) are usually used.

Process

The boiling point of pure ethanol is about 78 °Celsius, which is used in distillation. However, this temperature would be too high for the purpose of alcohol reduction, as valuable aroma substances would be lost. Therefore, this is done at a reduced pressure of 0.07 to 0.15 bar (otherwise 1 bar) in the temperature range of 30 to 60 °Celsius in order to keep a material change as low as possible. The retention time and temperature should be as low as possible. Other processes include electrodialysis, high-pressure extraction, filtration (nanofiltration, ultrafiltration), osmosis (reverse osmosis, osmotic distillation), pervaporation and spinning cone column. The specifications regarding the permitted processes differ from country to country. In Austria, the...