See under alcohol reduction.
Alcohol in wine can be reduced using various physical and/or chemical processes. Especially in southern regions, it is common to produce aromatic and less alcoholic wines. The simplest form is the addition of fruit juice or grape juice, which is used in the production of coolers, or water (stretching). A certain alcohol content can also be achieved by stopping fermentation by means of cooling, which is mainly practised in Italy for simple wines. The result is sweet, tangy and low-alcohol wines. In most cases, thermal separation processes such as vacuum distillation (vacuum rectification) are used.
The boiling point of ethanol is 78 °Celsius, which is utilised during distillation. This temperature would be too high for the purpose of alcohol reduction, as valuable flavouring 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 minimise any material change. 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 vary from country to country....
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