Hello! It is actually quite common for wines to contain some acetaldehyde as it is produced during the fermentation process (and to a greater degree in aged red wines). However, its sensory threshold in wine is about 100-125 mg/L while its typical concentration in wine is 5-40 mg/L. Thus, its presence is not usually detected in terms of wine aroma. If it does exceed this sensory threshold (which would result from improper storage or extreme oxidation conditions), it is most definitely considered an "aromatic taint" or flaw in the wine. More often, the undesirable aldehydic aroma detected in a wine is caused by the presence of low concentrations of other aldehydes with much lower sensory thresholds (E-2-hexenal, methional, phenylacetaldehyde, etc.). Free acetaldehyde concentrations in wine are relatively low, but ultimately contribute more in terms of polymeric pigment formation, tannin complexation, and other aged characteristics of aged red wines. I hope this answers your question and if you'd like to discuss this or any other wine chemistry related topics further please let me know! Thanks for the question!!

Good afternoon! Tanks for your explanation. I like very much when an explanation about wine aroma (good or bad) is followed by a value of sensory threshold, like you have just done.

Here in Portugal, I've talked with many winemakers and oenologues, and sometimes they talk about "acetaldehyde taint", but now I know that they are wrong, because probably is not acetaldehyde, but other aldehydes, as you have explained.

Once, I heard somebody trying to explain the benefits of acetaldehyde in the stability of wine pigments (anthocyanins),  and a winemaker sayd that acetaldehyde is bad for wine aroma.

Thats the reason of my question. Thanks a lot for your answer.