The colourless and very volatile liquid (ethanal, outdated ethanal) is the aldehyde of ethanol.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.
Health
In the human body, acetaldehyde is formed as an intermediate product during the degradation of ethanol by the so-called alcohol dehydrogenase (see under ADH). It is responsible for the hangover(headache, nausea) after excessive alcohol consumption. Studies have found evidence of a connection between the consumption of alcoholic beverages and increased risk of cancer in the digestive tract. There is an increased formation of oxygen radicals, which damage the membranes of the cells. Crotonaldehyde, which is formed from acetaldehyde, has been identified as the cause. In Germany, more than 1,500 spirits were tested in 2008 and high concentrations of acetaldehyde were found in spirits, port wine and sherry in particular. The highest values were found in Chinese and Mexican spirits. The lowest were found in beer (11 ± 9 mg/l) and wine (36 ± 42 mg/l). European food law only contains the limit value 0.5 grams of acetaldehyde per hectolitre of pure alcohol; no limit values are defined for all other product groups. Up to this value, adverse health effects are excluded. Nevertheless, a re-evaluation seems necessary.
Wine defects
In its pure form, acetaldehyde develops a numbing odour and, when present in larger quantities in wine, causes an unpleasant, sharp-bitter austere tone that is easily recognisable by the senses for experienced tasters even in much smaller quantities than the above limit. It is partly responsible for hangover symptoms such as headaches, nausea and vomiting. It is also the cause of various taste tones such as firn (aged firn), as well as air flavour (aldehyde tone), which is the desired result as a sherry tone. In a pronounced form or with the "wrong wine", such as a sherry tone with normal white wine, this means a wine defect. When reacting with hydrogen sulphide, foul-smelling thiols (mercaptans) can be formed, which cause the boil. See also a list of similar wine faults under Alterston.
