Acetaldehyde questions

[kalbarluke]

I am having trouble identifying off flavours in my beer. I've done some research and think it is acetaldehyde but it could be something more sinister. I have some general questions that I hope some people can help me out with:
1) will acetaldehyde increase cloudiness in beer? When I was transferring from fermenter to keg, the first third or so was quite cloudy and then it cleared up quite a bit. Or is it something more sinister?
2) I have read that sodium metabisulfate ban be used to get rid of the acetaldehyde from the keg. If what I have identified is acetaldehyde and want to add sodium metabisulfate, how much should I add? And will it sink to the bottom, binding the acetaldehyde so I can just expunge about a schooner or two of beer and be rid of it?


Any help or advice is welcome.

 

[barls]

no it shouldn't increase cloudiness in beer.
and i have never read that metabisulphate can fix it. the most common fix is add more yeast and it clears up.
acetaaldehyde is most commonly caused by removing the beer from the yeast cake too early. aka leave it another week on the cake and it will be fixed.
it can also be from an infection which will increase haze in beer

whats your normal method for fermenting?
mines normally. pitch leave a couple of weeks maybe longer depending on whats happening.
if i have space cc if not gelatine and keg.
i also naturally carb so the first pint or so is normally cloudy.

 

[gilmoreous]

Could also be from under oxygenation at pitching.

 

[manticle]

I am having trouble identifying off flavours in my beer. I've done some research and think it is acetaldehyde but it could be something more sinister. I have some general questions that I hope some people can help me out with:
1) will acetaldehyde increase cloudiness in beer? When I was transferring from fermenter to keg, the first third or so was quite cloudy and then it cleared up quite a bit. Or is it something more sinister?
2) I have read that sodium metabisulfate ban be used to get rid of the acetaldehyde from the keg. If what I have identified is acetaldehyde and want to add sodium metabisulfate, how much should I add? And will it sink to the bottom, binding the acetaldehyde so I can just expunge about a schooner or two of beer and be rid of it?


Any help or advice is welcome.

If the beer is removed too early from the yeast, you will likely still have yeast in suspension, causing cloudiness.
Can you describe the flavour and can you describe your fermentation process?

Is this happening with all beers, regardless of yeast strain, a few common ones or just one or two?

My understanding is that sodium metabisulfite scavenges oxygen and oxidation reactions can cause ethanol to travel back along its chemical pathway (acetaldehyde is an intermediate product creating during the production of ethanol - the pathway is reversible) so it may be in that context that you have heard it can be applied. I am hypothesising as it is not something I've done or heard tried but my guess is it might be used to prevent rather than remove.

It's not something I'd want lots of in my beer but you could try dosing a glass to see if it makes a difference. Use with caution and don't breathe it in.
However if it is acetaldehyde and the cause is just removal from the cake too early, you may have success dosing the keg with some healthy krausening yeast.

 

[WarmerBeer]

Just a question, but did you crash-chill your beer prior to kegging?

I personally found that, after a number of batches irregularly showing signs of acetaldehyde, that by slowly lowering the temperature of my primary over 5 or 6 days (1.5 degree, twice a day) rather than one big crash chill, it gave the yeast a better chance to clean up after itself. This resulted in a marked reduction, or absence, of acetaldehyde in my beers.

Admittedly, this is all anecdotal evidence, and a small sample size, but if you have temperature control over your ferm fridge, worth a try.

 

[Screwtop]

I am having trouble identifying off flavours in my beer.

We need you to describe these flavours to be able to respond in a helpful way.

Screwy

 

[justatad]

This might give you an idea of some off flavors, watch from abaout 1:00 min
https://www.youtube.com/watch?x-yt-cl=84411374&feature=player_embedded&v=ENCU7YeSB6Y&x-yt-ts=1421828030

 

[kalbarluke]

Just a question, but did you crash-chill your beer prior to kegging?

I personally found that, after a number of batches irregularly showing signs of acetaldehyde, that by slowly lowering the temperature of my primary over 5 or 6 days (1.5 degree, twice a day) rather than one big crash chill, it gave the yeast a better chance to clean up after itself. This resulted in a marked reduction, or absence, of acetaldehyde in my beers.

Admittedly, this is all anecdotal evidence, and a small sample size, but if you have temperature control over your ferm fridge, worth a try.

Yes I do crash chill. I will try your advice in future.

As for describing the taste, it does taste like unripe apples, but also like raw onion. It is difficult to put into words. It does have an aroma.

I had this particular beer in the fermenter for a month. It was a kolsch I pitched with a one litre yeast starter.

Thanks for the advice. I might nuke my fermenter just in case it is infection pf some sort.

 

[manticle]

Everyone's palate is different and descriptions of the same chemical depend as much on level in the beer, individual thresholds and individual's association of their flavour perception with a descriptor as anything else. I sometimes get acetaldehyde as green apples but pumpkin skin and synthetic paint emulsion are more common for me. However raw onion sounds more like a sulphur compound to me unless you used summit (or summat) in your brew. I know it was a kolsch but were the hops 'out of style' at all?

 

[Dunkelbrau]

Just a question, but did you crash-chill your beer prior to kegging?

I personally found that, after a number of batches irregularly showing signs of acetaldehyde, that by slowly lowering the temperature of my primary over 5 or 6 days (1.5 degree, twice a day) rather than one big crash chill, it gave the yeast a better chance to clean up after itself. This resulted in a marked reduction, or absence, of acetaldehyde in my beers.

Admittedly, this is all anecdotal evidence, and a small sample size, but if you have temperature control over your ferm fridge, worth a try.

This is actually something that is important.

Most people don't notice anything because the fridge won't cool the beer down that fast, however yeast can have a reaction even when fermentation is done and release things back into the beer.

I believe its called heat shock response or something if anyone is interested in reading about it.

 

[O-beer-wan-kenobi]

Yes I do crash chill. I will try your advice in future.

As for describing the taste, it does taste like unripe apples, but also like raw onion. It is difficult to put into words. It does have an aroma.

I had this particular beer in the fermenter for a month. It was a kolsch I pitched with a one litre yeast starter.

Thanks for the advice. I might nuke my fermenter just in case it is infection pf some sort.

A month seems a long time on the yeast. I had an off flavour in my lagers that i think was acetaldehyde so I kept them on the yeast cake longer to try and clean up the beer. This didn't help and possibly got worse the longer I left it. In the end I gave up on lagers for a while.
My LHBS said to get the beer off the yeast when it's done and I also heard a podcast with dr Charlie bamforth saying the same so decided to have another go. Now I ferment my lagers until they have fermented out and then give them a few more days before transferring to a keg to lager. Since then I haven't had the problem. I can't say for sure that leaving the beer on the yeast too long was the issue but I haven't had the problem since.

I tried to get rid of the off flavour/aroma using Camden tablets( sodium met??) and burping the keg but it didn't work.

 

[Screwtop]

It was a kolsch I pitched with a one litre yeast starter.

Hmmm, maybe it's not Acetaldehyde, tell me about how you prepared your starter.

Q1 Starter size and gravity

Q2 Was the yeast fresh

Q3 Did you use a stirplate/aerate. If so how long for.

Screwy

 

[kalbarluke]

Hmmm, maybe it's not Acetaldehyde, tell me about how you prepared your starter.

Q1 Starter size and gravity

Q2 Was the yeast fresh

Q3 Did you use a stirplate/aerate. If so how long for.

Screwy

1) used 1 L of water and 1/2 cup of LDME. Boiled for 15 mins and cooled to room temp.
2) no. Don't remember exact age but it was a few months old.
3) no stirplate. Stirred every tive I walked past. 24 hrs.

 

[Screwtop]

1) used 1 L of water and 1/2 cup of LDME. Boiled for 15 mins and cooled to room temp.
2) no. Don't remember exact age but it was a few months old.
3) no stirplate. Stirred every tive I walked past. 24 hrs.

Thanks, I was looking for some other cause, maybe oxidation of your starter wort. some brewers leave the starter on the stirplate way past phase one sometimes for 4 - 5 days.

Screwy