Carrying on with the series of articles on off flavours, so far we’ve covered the following: Skunky, Diacetyl, Oxidised now brings us to a compound called Acetaldehyde.
Now acetaldehyde is said to cause a flavour reminiscent of green apples, it occurs naturally in plants as part of their natural metabolism and is an intermediate in the formation of alcohol. It’s also commonly cited to be the cause of hangovers, so let’s take a look at how it’s created and how to avoid it becoming apparent in your home brew.
Acetaldehyde In Beer
Whilst acetaldehyde is considered an off flavour, it can also be considered part of some beers flavour profile. If you are trying to spot it in a a beer the things to look out for a beers that have aromas or flavours similar to green apples, freshly cut pumpkin or grass or green leaves.
The reason why it can be more apparent in certain styles of beer is in part because certain yeast strains produce more of it than others. The creation of acetaldehyde is a intermediate step in the conversion of sugar to ethanol which of course is one of the primary roles of the yeast. Now under ordinary circumstances the yeast will clear up acetaldehyde to levels where it’s undetectable. If however they don’t have time or chance to do this there will be an apparent off flavour in your home brew.
Preventing Acetaldehyde In Your Home Brew
As mentioned previously acetaldehyde becomes apparent when the yeast don’t have time to clear it up after fermentation, it’s for this reason that young beers (green) may have some green apple flavours. Aging the beer for longer and conditioning properly will allow time for the yeast to remove this undesirable flavour.
Racking the beer off the yeast cake too early is another reason you may have acetaldehyde off flavours in your home brew. It’s obvious that if we need to rely on the yeast to clear up these flavours, if you take the beer off the bulk of the yeast to early then they won’t be able to do as good of a job.
Making sure that you’re pitching the right amount of healthy yeast into well aerated wort also goes without saying, this is standard procedure anyway.
Lastly, selecting a less flocculent yeast strain will keep everything in suspension longer, or rousing the yeast mid way through fermentation will allow them sufficient time to clear everything up.
