The colourless and very volatile liquid (ethanal, outdated ethanal) is the aldehyde of ethanol. The name is often mispronounced, the correct one is "acet-aldehyde". It is a natural component of almost all plant matter. The substance is formed during alcoholic fermentation with the release of carbon dioxide as a precursor of the final product alcohol. Towards the end of fermentation, the proportion normally decreases very sharply. Acetaldehyde is present in all wines in normally small amounts and does not have any negative taste effects in low concentrations. It reacts with anthocyanins, catechins and sulphur dioxide, whereby it is involved in the formation of pigments (dyes). In the bottle, faulty corks can cause it to react with oxygen and thus impair the aroma, especially in white wines. Acetaldehydes bind sulphur in wine, or make it a sulphur eater.