Acetaldehyde?

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Brew_DD2

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Bit of a strange one this. Just went to keg my latest Kölsch after the first one from a wee while back was a real success.

After racking to my bottling bucket I couldn't help but notice an odd smell. I decided to take a sample test and there was a distinctive appley/peardrop flavour that was rather unpleasant. I did a quick Google for off-flavours and it appears acetaldehyde is the most likely culprit.

This is where is gets a little strange. 10 days into fermentation I took a gravity reading and the beer was at 1.008 and tasted superb, very clean and no signs of apple. At this stage I brought the temperature up to 19c (primary fermentation temperature was at 16c). I had intended to keg the following week but life got in the way and it's ended up being about 6 weeks in total in the primary fermenter.

Now as far as I was aware, acetaldehyde usually only presents itself in a very young beer. So, what's gone on here? Beer spent too long on the yeast cake? Possible infection? Gravity today also 1.008.
 

foxy

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If you have already kegged it let it sit for a couple of weeks and have another taste, I have had it before in a bottled beer and it went, I am pretty sure that the yeast strain I used was the cause of mine.
 

Brew_DD2

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I just can't understand how it could have taken on green beer character when it previously wasn't there.
 

foxy

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May have something to do with the extended period on the yeast cake, what yeast did you use?
 

strange-steve

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It's possible what you tasted was just the yeast character, kolsch yeasts have been known to have a pear/apple fruitiness.
 

Brew_DD2

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CML Kölsch yeast. I could live with it if it was subtle but it's really not pleasant.
 

BeerCat

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I dont really know what a Kolsch should taste like as never had one. Only used the CML yeast and i think it really does benefit from being left in the bottle for a few months before drinking. I have not found the yeast taste to be unpleasant though as i brewed this about 5 times. I do add a slice of lemon to most bottles of Lager as i like the zing. I raise the temps after a few days and try and ferment as cold as possible. What yeast did you use?
 

Duxuk

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I've had 3 brews which have got the acetaldehyde taste. One was strong and I had to dispose of it. One was mild and went in 2 weeks in the bottle. I currently have a keg which has been unpleasant.................Until now!
It has just about become undetectable so I am very relieved.
The common factors have been that all 3 were fermented without temp. control in warm summer weather, and all only exhibited the flavour right at the end of the fermentation. Could it be that the theory is wrong? My experience (and maybe yours) suggests that you can get this nasty taste developing at a late stage.
Acetaldehyde is apparently a precursor to ethanol in the fermentation process. What seems to have happened in these cases is that the final step has stopped. Somewhat like a stuck fermentation but stuck half way through!
As suggested above give it time.
 

Brew_DD2

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Cheers gents. Dux I find it curious that two weeks in it wasn't there and the beer tasted great and then it appeared weeks later. I'm sure the contact time with the yeast cake must be a factor as temperature is not an issue for me.

Given how it tasted when it was really green I'm not completely convinced it is acetaldehyde. Unless it can present itself later down the line.
 

Brewed_Force

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My latest pseudo lager, using CML kolsch yeast has a pronounced 'fruity' taste. I did pitch at 28C as I couldn't wait any longer for the wort to cool in the hot weather a couple of weeks ago.
Is the taste due to the kolsch yeast or the temperature? Will it eventually dissipate?
 

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