Acetaldehyde

[yoey]

I put down my first lager back in April and it has a strong "green apple" flavour which I believe is acetaldehyde.

This brew was an NNL Bohemian Lager fwk using Saflager W34/70 dried yeast. I pitched 2 packets of yeast at 18 deg C, dropped the temp to 11 deg C over 9 hours and fermented at 11 deg C for 12 days, rasied the temp to 18 deg C for 2 days (diacetyl rest), racked to secondary at 3 deg C for 7 days then kegged. I also had a little left over which I bottled, adding 2 coopers carb drops to each bottle and left these at ambient temp for 2 weeks before refrigerating.

The OG was 1045 and FG was 1010 when kegged.

A sample taken while kegging had a very strong taste of green apples. The brew has now been in the keg for 16 weeks (at around 3 deg C) and while the green apple flavour has greatly subsided it is still there.

When I tried the brew that had been bottled there was no green apple flavour at all. It was very nice.

I have a couple of questions...

Due to the fact the bottled beer had no off flavours is it correct to assume that the off flavours would have been cleaned up if I had left the beer in primary for longer? If so how much longer should I have left it and at what temp?

Will the off flavour ever dissappear from the beer or should I give up on it and dump it?

Is it true that drinking a beer with this level of acetaldehyde will give you a worse hangover than drinking a beer without it?

 

[sinkas]

Apparently, Jamil zainacheff says that if you get a small amount of fermenting wort (500ml)and dump it into the beer, the yeast will chew through the acetaldehyde and clear it up, have not tried this though.

 

[sinkas]

Not sure if you can do this with carbonated beer though,

 

[buttersd70]

Not sure if you can do this with carbonated beer though,

If the keg is degassed, and a starter like you described is added and the keg is then sealed, if the amount of fermentable in the starter is right, it would naturally prime the keg again anyway . Which is probably why the bottles were ok - the increased yeast activity from the prime cleared it up.....

Not saying it would work for the acetaldehyde, but if Jamil says it will, I'd say it's a safe bet, and its better than just dumping the lot. If it does work, it just means that you'll need to settle it out in the keg as per any naturally primed keg beer.

 

[Jez]

Might be acetaldehyde but is this your first batch you've kegged? Have you had the green apple taste over a few kegged brews?

I had a very similar problem to what you've described and my first 4 kegged brews were green apple delights. I gave my keg fridge, which was incidentally quite filthy inside, a HUGE scrub down with undiluted domestos (MAKE SURE YOU WEAR GLOVES!). The green apple taste disappeared and has not come back.

If your bottled brew is ok might be worthwhile cleaning the keg fridge.

Jez

 

[yoey]

Might be acetaldehyde but is this your first batch you've kegged? Have you had the green apple taste over a few kegged brews?

I had a very similar problem to what you've described and my first 4 kegged brews were green apple delights. I gave my keg fridge, which was incidentally quite filthy inside, a HUGE scrub down with undiluted domestos (MAKE SURE YOU WEAR GLOVES!). The green apple taste disappeared and has not come back.

If your bottled brew is ok might be worthwhile cleaning the keg fridge.

Jez

I've kegged batches before and after this one (all ales) without the green apple smell and taste.

Thanks for the reply - I might do as you suggest anyway, just to make sure...

 

[yoey]

Apparently, Jamil zainacheff says that if you get a small amount of fermenting wort (500ml)and dump it into the beer, the yeast will chew through the acetaldehyde and clear it up, have not tried this though.

Thanks! I might give this a go on the weekend - I'll post my results.

I'm more concerned with improving my process and learning how to stop this from happening with future brews.

 

[sinkas]

apparently over pitcing is the reason I have created this lovely aroma in the past,

 

[edoeven]

i had some problems with green apple beers... I had made a couple of lagers without issue earlier, then suddenly two in a row tasted like green apples. Both kegged into the same keg also, even after a good clean the same keg also made an ale go green and apply... ARGH, the lagers were brewed with the same yeast and very similar process to the previous sucessfull brews so I figured it (probably) was not that.

so I ended up pulling apart the keg and soaking the whole thing in sanitiser for a few weeks...as well as disconnects/lines.
no more green apples now!

I ended up trying a couple of things like extended rest's, stirring up the sediment from the bottom of the keg, etc, nothing helped get rid of the taste. Resting at higher temp made it worse (as could be expected from an infection i guess). definetly worth giving your kegs a good clean even if you suspect it is a brewing process issue.

i should add that some of my less-beer-fussy friends would still slam down the apple beer without complaint! could be an option before tipping it !

 

[daemon]

I'm about to bottle a NNL Bohemian Lager based brew too, and have had some strange flavours from it as well. This was with a recultured liquid yeast (forget the exact one!) and it's got a spicy/clove smell and taste to it. It's subsided a bit with a week in secondary but still far more dominant than I really want. Temps should have been fine (9-12C) and another lager at the same time has come through nice and clean.

Will wait to see what it's like after a few weeks in bottles and see if things improve from there. Considering the taste of the fresh wort before fermentation, it's so far a little bit disappointing.... but this is my first time attempting a proper lager with lager yeast.

 

[yoey]

apparently over pitcing is the reason I have created this lovely aroma in the past,

I pitched 2 packets of dry yeast as recommended on this site. How much should I pitch? If overpitching was the problem wouldn't the bottled beer have the off flavour as well?

 

[yoey]

i had some problems with green apple beers... I had made a couple of lagers without issue earlier, then suddenly two in a row tasted like green apples. Both kegged into the same keg also, even after a good clean the same keg also made an ale go green and apply... ARGH, the lagers were brewed with the same yeast and very similar process to the previous sucessfull brews so I figured it (probably) was not that.

so I ended up pulling apart the keg and soaking the whole thing in sanitiser for a few weeks...as well as disconnects/lines.
no more green apples now!

I ended up trying a couple of things like extended rest's, stirring up the sediment from the bottom of the keg, etc, nothing helped get rid of the taste. Resting at higher temp made it worse (as could be expected from an infection i guess). definetly worth giving your kegs a good clean even if you suspect it is a brewing process issue.

i should add that some of my less-beer-fussy friends would still slam down the apple beer without complaint! could be an option before tipping it !

I will give my kegs a complete clean and soak and see how that goes.

A mate of mine has tried the beer and said he liked it - but I'm not that keen on it. Guess I can serve it up on Grand Final day... :icon_cheers:

 

[yoey]

I'm about to bottle a NNL Bohemian Lager based brew too, and have had some strange flavours from it as well. This was with a recultured liquid yeast (forget the exact one!) and it's got a spicy/clove smell and taste to it. It's subsided a bit with a week in secondary but still far more dominant than I really want. Temps should have been fine (9-12C) and another lager at the same time has come through nice and clean.

Will wait to see what it's like after a few weeks in bottles and see if things improve from there. Considering the taste of the fresh wort before fermentation, it's so far a little bit disappointing.... but this is my first time attempting a proper lager with lager yeast.

I don't think its the fwk as I also did a Morgans Scharls European Lager kit and it had the same off taste. I've since done a couple of ales and they turned out great. Its only the lagers I have had the problems with. I think its something to do with my process or my gear.

 

[buttersd70]

I pitched 2 packets of dry yeast as recommended on this site. How much should I pitch? If overpitching was the problem wouldn't the bottled beer have the off flavour as well?

Pitching rate from the fermentis website and scaled down from hectolitres to 23L:
18.4- 27.6g at 12-15C
46- 69g at 9c

I agree that any issue in relation to pitching would be in the bottle as well.
Logically, there are 2 variables here. Firstly, keg v bottle, and secondly, sugar prime v gas charge, cos there was no seperation of process untill this point.

- If the problem is infection, then it occured in the keg, not prior to kegging.
- If the problem is acetaldehyde, then the sugar prime fixed it in the bottle.

I think acetaldehyde is the more likely of the 2, given that you said it had the apple taste at the time of bottling/kegging, and the taste has gone from the bottle and lessened in the keg. If it was infection, it would (likely) have got worse, not better, over time in the bottle/keg.

Personally, I would edge my bets, by treating it as an acetaldehyde issue for the moment, and then, when the keg is empty, giving it a full clean just on the off chance that it was infection. (especially if you don't manage to correct the problem and end up ditching, because if this happens, doubt will linger as to what went wrong.)

 

[dr K]

Acetaldehyde is a precursor to ethanol, it will always be produced in a fermenting wort (unless you stop the ferment before you get acetaldehyde in which case you won't get ethanol!!).
The most common reason for acetaldehyde is incomplete fermentation, if the beer continues to ferment (say in the bottle) you might get rid of enough to be below flavor threshold.
Acetaldehyde may also be a result of oxidation of ethanol or an infection, in these cases the beer is going to go from bad to worse.


K

 

[yoey]

Thanks for all the replys.

I'm thinking the off flavour is mainly due to incomplete fermentation as the taste was not evident in the bottle conditioned beer which had gone thru a secondary fermentation for the purpose of carbonation.

As stated above, if infection was the cause then the taste would get worse, but in this case it has improved. So I think this may rule out an infection.

As sinkas recommended I am going to degass the beer and add 500ml of fermenting wort to see if that has any effect - mainly to help identify if the incomplete fermetation was the cause. Doubt has been raised about whether this will be effective on carbonated beer - if it works then I know the problem was the early removal from primary, if not then I am no better or worse off.

I will also take on board the suggestions to do a thorough clean and sterilisation of all my kegs and gear before putting down another lager which I will leave in primary a little longer.

 

[buttersd70]

Let us know how it goes, yoey.

 

[yoey]

Let us know how it goes, yoey.

Will do :icon_cheers:

 

[PistolPatch]

[If you have been really battling with the usual answers to this problem then read to the end for a possible answer.]

I never even realised what this weird but repulsive taste was until recently.

The reasons for it's occurrence in a great beer faults link that Stuster provided are listed as...

a) Premature Removal from Yeast
B) Premature Flocculation
c) Oxygen Depletion
d) Bacterial Spoilage
e) Oxidation

I can discount a) B) and e) straight away.

Oxygen depletion gave me great hope as I used to aerate and then got lazy. I was all excited about this being the answer to my problems and vigorously aerated the two beers I did two weeks ago. But, when I told a repeated gold medal ale winner how I was 99.9% sure this was the answer, he said, "Ah, I hate to tell you this, I never bother aerating my ales."

Agh!!!

The result of those two beers (14 days after pitching) is one has, "that funny taste," and the other doesn't!

I brewed today and something occurred to me but, before we go there, let's wrap up the Bacterial Spoilage possibility.

Bacterial Spoilage: As this taste is erratic and I use 3 fermenters, maybe it is two of those fermenters that have a spoilage? I really doubt this. I am a clean freak in all areas of brewing. Anyway, Katie and Lloyd brewed double-batches with me here last brew day so if their beer comes up clean we'll know. (Mind you, they bottle and I keg.) Another possibility is in the 23 lt kegs I use. Morgan's have found that some of them are rusting on the inside. I don't think this would cause a green apple taste but then again I haven't checked them really well for a long time.

So, what's left???

Trub Into Fermenter

The one thing that never occurred to me until today was how little trub I have been putting into the fermenter for quite some time. I remember well when I initially batch-sparged and BIABed how much trub would be in the fermenter. It was pretty much up to or above the tap outlet of the fermenter.

Now, I have the smallest layer ever.

So, I think this could well be a part of, if not the, problem. It makes sense. Trub is a yeast nutrient after all.

What I have Done Today as a Test

The above only occurred to me half-way through my brew day today so I could only half-test my theory.

The first beer was a pale ale highly hopped at the back end. The second was a very very pale ale (cream ale grain bill including rice and sugar) but highly hopped again at the back end.

The former I basically worked so as I had as close to zero trub as you can get. The latter I put everything in that was in the kettle bar 2.6lts of trub.

I'm hoping I can detect actealdeyde in the former heavier beer and that I can't detect it in the lighter beer.

Fingers crossed and I'll report back,
Pat