Ethanol

The most popular alcoholic beverage on French tables, wine contains 7-16% ethyl acid by volume.. It is a colourless, water-miscible liquid with the chemical formula CH3-CH2-OH. It is an ingredient in all the alcoholic beverages we consume: wines, beers, ciders, brandies, liqueurs, etc. Inflammable, it is responsible for the "wow" effect of a flambéed banana, for example, and for the drunken intoxication at the end of a drunken meal. Volatile, ethanol evaporates at 78.34°C: that's how it makes way for the other flavours in a wine or spirit when preparing a broth, sauce, etc.

Ethanol is one of the products of the transformation of fermentable sugars in grapes . This natural process, orchestrated by yeast, is called alcoholic fermentation and is a key stage in the winemaking process. The main sugar digested by these microscopic fungi is glucose: this is known as glycolysis, a metabolic reaction that transforms it successively into two pyruvate ions, then into ethanal and CO2 (carbon dioxide). The ethanal is then reduced to ethanol.

The proportion of alcohol in wine is therefore closely linked to the amount of sugar naturally present in the grapes, and therefore to their ripeness as well as to the climate! The sweeter they are at harvest time, the higher the ethanol content of the vintage resulting from vinification. However, it is also possible to add sugars to a wine artificially, thereby increasing its alcohol content. This is known as chaptalisation, but this technique is rarely used. It is reserved for wines of lesser quality.

The alcohol content of a wine, also known as alcohol by volume (ABV), is subject to international regulation. It must appear on the label of every bottle of alcohol, clearly legible and accurate to within 0.5%. The TAV corresponds to the percentage by volume of ethanol in 1 litre of alcoholic beverage, at a temperature of 20°C. It is expressed in degrees: 1 litre of wine containing 110 ml of ethyl acid is therefore a wine at 11°.

Ethyl acid is responsible for the 'warming' effect felt when swallowing a mouthful of wine. This impression becomes stronger as the temperature rises: it will be felt more when tasting reds than whites or rosés, which are served cooler. While ethanol molecules influence a wine's ageing potential, they are primarily responsible for how it feels on the palate when it is consumed, particularly the perception of its 'fatness'. There is no ideal TAV for the quality of a wine: it's all about finding the right balance between alcohol and acidity, as well as tannins for red grape varieties . Done well, it helps to counterbalance the salty, bitter or acidic flavours of a dish.