Homebrewers Association | AHA Forum

General Category => Yeast and Fermentation => Topic started by: Carson B on April 24, 2021, 11:53:22 am

Title: Acetaldehyde in Lagers
Post by: Carson B on April 24, 2021, 11:53:22 am
I have gotten what I believe to be acetaldehyde (green apples, cider) in every lager I've made. I've never gotten it in any other beer, nor had any off-flavors in any other beer I've ever made. I sanitize like crazy, have glycol-mediated temperature control, so on and so forth. I've read major causes of acetaldehyde are oxidation (I transfer everything under CO2; beer never touches oxygen until the glass), infection, and incomplete fermentation. I don't see any of those being my issue, especially considering I've never had those problems with other beers. I cannot for the life of me figure out why I'm getting acetaldehyde, so I've come here for help. Perhaps the biggest help in identifying the issue is that I only notice it once the beer is crashed, kegged, and carbonated. Here's the last recipe and some notes as an example:

46% - Pilsner
26% - Munich
25% - Vienna
03% - Victory

OG: 1.049
FG: 1.012

90-minute boil
20 IBUs total of Hallertau Mit. and Saaz at 60 minutes

Wyeast 2308 Munich Lager pitched at proper rate after starter

Fermented at 50 degrees for a week when activity stopped, then gradually raised to 67 for diacetyl rest.
Once final gravity was reached and no off-flavors detected (about two weeks), cold crashed to 35 gradually and then held there for another two weeks.
Kegged after cold crashing. Five weeks brew day to keg. Planned to continue to crash/lager in the keg with floating dip tube.

Any detectives out there who can spot what might be causing this? This is just one of about five lagers I've tried, some with different yeast, and they've all had acetaldehyde. I am at my wits end.
Title: Re: Acetaldehyde in Lagers
Post by: majorvices on April 24, 2021, 12:05:05 pm
Hmmmm .... have you tried a different yeast? Seems like you are doing everything right.

Edit: I see you have. How trusting are you of your Co2 source? I have tested Co2 with a DO meter before with unpleasant surprises.
Title: Re: Acetaldehyde in Lagers
Post by: Carson B on April 24, 2021, 12:11:45 pm
Thanks for your response. I get all my CO2 from the same home-brew shop, and have never had reason to doubt it, but also haven't checked it for any DO. I haven't had issues with it on other beers. When I cold crash, I hook up the fermenter to CO2 for some positive pressure to avoid suck-back. If there is any O2 in there, that would explain everything. Still not sure why I wouldn't notice it in other beers though. Good avenue to look into still
Title: Re: Acetaldehyde in Lagers
Post by: majorvices on April 24, 2021, 12:21:08 pm
Maybe try natural conditioning and see if the problem persists. If they aren't getting beverage grade co2 it could *possibly* be a problem.
Title: Re: Acetaldehyde in Lagers
Post by: RC on April 24, 2021, 12:25:33 pm
First thing that pops into my head is, are you sure it's not also in your other beers? Ales are generally more strongly flavored, and the subtle presence of off-flavors is easier to miss. Maybe it's just more noticeable in your lagers because they are more "delicate" (man I hate that word when describing lagers).

What is your brewing water? Is it RO or distilled? If so, do you only use this water for your lagers? That would point to zinc deficiency. The enzyme that converts acetaldehyde to ethanol needs zinc to function properly. Sometimes just adding zinc sulfate is the solution to mystery acetaldehyde.

All that said, if you are not tasting off-flavors before cold-crashing, and then you do taste them, then clearly something is happening after cold-crashing. And the only thing that makes sense is oxygen exposure. Do you purge your kegs first? Are you filling them all the way?
Title: Re: Acetaldehyde in Lagers
Post by: Carson B on April 24, 2021, 12:33:57 pm
First thing that pops into my head is, are you sure it's not also in your other beers? Ales are generally more strongly flavored, and the subtle presence of off-flavors is easier to miss. Maybe it's just more noticeable in your lagers because they are more "delicate" (man I hate that word when describing lagers).

What is your brewing water? Is it RO or distilled? If so, do you only use this water for your lagers? That would point to zinc deficiency. The enzyme that converts acetaldehyde to ethanol needs zinc to function properly. Sometimes just adding zinc sulfate is the solution to mystery acetaldehyde.

All that said, if you are not tasting off-flavors before cold-crashing, and then you do taste them, then clearly something is happening after cold-crashing. And the only thing that makes sense is oxygen exposure. Do you purge your kegs first? Are you filling them all the way?

All good things to consider.

(1) If it's in other beers, I truly do not notice. And it's so strong in lagers, to the point of making them undrinkable, that I'd be surprised if it is in other beers. I also have no clue what would be causing it during at least the actual brewing and fermentation process.

(2) The water is typically a 50/50 split between RO and my tap water, dechlorinated with a Campden tablet. I use Brunwater for water chemistry stuff. I use it for most other beers as well. I do not know what the Zinc content is, though. I will absolutely add some Zinc sulfate next time. Never heard of doing that - what kind of concentration are we talking? It's worth noting I do add Wyeast Nutrient in the boil, and I imagine that's pretty zinc-rich.

(3) I go to great lengths to prevent oxygen exposure. The keg is filled with Starsan solution, then I push it out with CO2, purging the whole keg. The beer is then transferred under closed CO2 system. Full keg. I then purge the headspace further just for safety. Habit I got in making a bunch of NEIPAs.
Title: Re: Acetaldehyde in Lagers
Post by: Carson B on April 24, 2021, 12:34:49 pm
Maybe try natural conditioning and see if the problem persists. If they aren't getting beverage grade co2 it could *possibly* be a problem.

I've got a 2.5-gallon keg crashing in the fridge that I think I will bottle. I've never bottled them before, so that's a good next step to see where the problem might be starting. Thanks
Title: Re: Acetaldehyde in Lagers
Post by: denny on April 24, 2021, 12:59:49 pm
Are you certain it's acetaldehyde?
Title: Re: Acetaldehyde in Lagers
Post by: RC on April 24, 2021, 01:01:00 pm
In light of the new info, I can't imagine your beer is deficient in zinc.

If you do try the zinc sulfate, the dosage is exceedingly small: 10-20 mg per 5 gal. This small an amount can be hard to measure on a typical homebrewing scale, but you can make a large solution with an amount that is easier to weigh. Definitely don't use more than this, though, as too much is toxic to yeast.

You mention that you pitch at the proper rate, but what rate are you using, and how do you make your starters for your lagers?

This one is a stumper. I have one or two other ideas as to a source of possible oxygen, but they would involve your other beers as well. If this really is just limited to your lagers, then what do you do different for your lagers vs. your other beers? That would point to the cause.
Title: Re: Acetaldehyde in Lagers
Post by: Carson B on April 24, 2021, 01:03:44 pm
In light of the new info, I can't imagine your beer is deficient in zinc.

If you do try the zinc sulfate, the dosage is exceedingly small: 10-20 mg per 5 gal. This small an amount can be hard to measure on a typical homebrewing scale, but you can make a large solution with an amount that is easier to weigh. Definitely don't use more than this, though, as too much is toxic to yeast.

You mention that you pitch at the proper rate, but what rate are you using, and how do you make your starters for your lagers?

This one is a stumper. I have one or two other ideas as to a source of possible oxygen, but they would involve your other beers as well. If this really is just limited to your lagers, then what do you do different for your lagers vs. your other beers? That would point to the cause.

I pitch lagers at a calculated 1.5 million cells/mL scaled for gravity. Typical DME starter on a stir plate. The only difference is the lower fermentation temperature and extended cold crash. Everything else is exactly the same. Truly a stumper
Title: Re: Acetaldehyde in Lagers
Post by: Carson B on April 24, 2021, 01:06:10 pm
Are you certain it's acetaldehyde?

Not certain from a chemical analysis standpoint, but it's certainly not coming from any of the ingredients, and the flavor/aroma descriptors fit acetaldehyde perfectly (green apple, cider, etc.).
Title: Re: Acetaldehyde in Lagers
Post by: RC on April 24, 2021, 01:16:41 pm
In light of the new info, I can't imagine your beer is deficient in zinc.

If you do try the zinc sulfate, the dosage is exceedingly small: 10-20 mg per 5 gal. This small an amount can be hard to measure on a typical homebrewing scale, but you can make a large solution with an amount that is easier to weigh. Definitely don't use more than this, though, as too much is toxic to yeast.

You mention that you pitch at the proper rate, but what rate are you using, and how do you make your starters for your lagers?

This one is a stumper. I have one or two other ideas as to a source of possible oxygen, but they would involve your other beers as well. If this really is just limited to your lagers, then what do you do different for your lagers vs. your other beers? That would point to the cause.

I pitch lagers at a calculated 1.5 million cells/mL scaled for gravity. Typical DME starter on a stir plate. The only difference is the lower fermentation temperature and extended cold crash. Everything else is exactly the same. Truly a stumper

Hmmm...what about that extended cold crash. It takes time for oxygen to wreak its havoc. If your CO2 has excess oxygen in it, then you are allowing it more time to damage your lagers vs your ales, therefore you might notice it only in your lagers, even though your ales are also being damaged (they're just not being given enough time to show the damage). I'm not suggesting you are doing anything wrong, because it doesn't sound like you are. But as majorvices said, it could be your CO2, and the oxygen damage is revealing itself only in your lagers because of that longer cold crash.
Title: Re: Acetaldehyde in Lagers
Post by: BrewBama on April 24, 2021, 01:30:55 pm
Here’s a chart I’ve had for a while for a reference between the various grades. Not sure which vendor this is from or if it’s a standard all vendors adhere to. I just get my CO2 from a welder supply shop because it’s convenient.  So far so good.

(https://uploads.tapatalk-cdn.com/20210424/222111c0bae747b39dd800f83bedb8a1.jpg)
Title: Re: Acetaldehyde in Lagers
Post by: majorvices on April 24, 2021, 01:44:10 pm
Here’s a chart I’ve had for a while for a reference between the various grades. Not sure which vendor this is from or if it’s a standard all vendors adhere to. I just get my CO2 from a welder supply shop because it’s convenient.  So far so good.

(https://uploads.tapatalk-cdn.com/20210424/222111c0bae747b39dd800f83bedb8a1.jpg)

I tested some tanks we got from Sexton on our DO meter on YH a couple years back. They weren't 99.5%  pure. I don't remember what the reading was but off-hand, but it was high. If they aren't filled properly the reading can be higher than expected and whose gonna know if you don't check 'em?

I still get my home tanks filled there and they seemed to fix the problem when I told them about it but who knows what is going on with these tanks.
Title: Re: Acetaldehyde in Lagers
Post by: Carson B on April 24, 2021, 03:19:21 pm
Thank you everyone, sincerely, for the replies. Sometimes I'm surprised at how willing people are to try to diagnose someone else's issues when that beer will never reach them anyways! haha! It seems the leader in the clubhouse is the extended cold crash with extended CO2 exposure. I have bottled half of the batch as suggested above, and the next lager I make I think I'll take it straight from fermenter to keg (when it is tasting totally fine) and skip the cold crash just to see what happens
Title: Re: Acetaldehyde in Lagers
Post by: denny on April 24, 2021, 04:46:57 pm
Thank you everyone, sincerely, for the replies. Sometimes I'm surprised at how willing people are to try to diagnose someone else's issues when that beer will never reach them anyways! haha! It seems the leader in the clubhouse is the extended cold crash with extended CO2 exposure. I have bottled half of the batch as suggested above, and the next lager I make I think I'll take it straight from fermenter to keg (when it is tasting totally fine) and skip the cold crash just to see what happens

I hope I don't seem like I'm picking on you,  but in this situation I always think....you followed the same basic procedures with basically the same ingredients and process as many of us.  So, why aren't there more reports of this? I always wonder if there's something we're all missing.
   

Title: Re: Acetaldehyde in Lagers
Post by: Carson B on April 24, 2021, 04:56:54 pm
Thank you everyone, sincerely, for the replies. Sometimes I'm surprised at how willing people are to try to diagnose someone else's issues when that beer will never reach them anyways! haha! It seems the leader in the clubhouse is the extended cold crash with extended CO2 exposure. I have bottled half of the batch as suggested above, and the next lager I make I think I'll take it straight from fermenter to keg (when it is tasting totally fine) and skip the cold crash just to see what happens

I hope I don't seem like I'm picking on you,  but in this situation I always think....you followed the same basic procedures with basically the same ingredients and process as many of us.  So, why aren't there more reports of this? I always wonder if there's something we're all missing.
   

I'm always after the most on-the-nose advice/criticism I can find. That's how you get better. I've seen people get very defensive on here, and that's not what I'm after. I appreciate all the honest feedback. I'm trying to figure out what I'm missing, too. There's always the chance I'm just tasting something different, and it's not acetaldehyde. But, that's my best guess. Fits the descriptors perfectly. Whatever it is is certainly not welcomed in my lagers!  ;D
Title: Re: Acetaldehyde in Lagers
Post by: mainebrewer on April 25, 2021, 04:15:36 am
You may want to try transferring your beer into the keg before it is completely finished. Purge the keg (either a sani or fermentation purge), when the beer is almost finished fermenting (3-4 points remaining) do a closed transfer to the keg and let the beer finish in the keg. The yeast in the beer will use up any remaining O2 in the keg and when the beer is finished it will be fully carbonated. A spunding valve will be helpful in monitoring the CO2 pressure in the keg.
Title: Re: Acetaldehyde in Lagers
Post by: majorvices on April 25, 2021, 06:16:25 am
You may want to try transferring your beer into the keg before it is completely finished. Purge the keg (either a sani or fermentation purge), when the beer is almost finished fermenting (3-4 points remaining) do a closed transfer to the keg and let the beer finish in the keg. The yeast in the beer will use up any remaining O2 in the keg and when the beer is finished it will be fully carbonated. A spunding valve will be helpful in monitoring the CO2 pressure in the keg.

Not saying not to try this, but some of the ways mentioned to avoid acetaldehyde is by not racking too early.
Title: Re: Acetaldehyde in Lagers
Post by: MNWayne on April 25, 2021, 09:29:43 am
Whenever my lagers tasted a little "cidery" I attributed it to poor balance.  Insufficient bittering or excessive unfermentables.  Bittering is very process dependent. Maybe your 20 IBUs is not really 20.  Maybe some gypsum would help accentuate the hops a bit and offset what I'm guessing is an under-bittered beer.  I'm guessing here, I could be way off.
Title: Re: Acetaldehyde in Lagers
Post by: narcout on April 25, 2021, 09:55:52 am
There's always the chance I'm just tasting something different, and it's not acetaldehyde. But, that's my best guess. Fits the descriptors perfectly. Whatever it is is certainly not welcomed in my lagers!  ;D

For $30, you could get it tested.

https://oregonbrewlab.com/products/#offflavor

If it's really driving you nuts, it might be worth it.
Title: Re: Acetaldehyde in Lagers
Post by: majorvices on April 25, 2021, 10:03:52 am
That's worth the price IMO!
Title: Re: Acetaldehyde in Lagers
Post by: denny on April 25, 2021, 10:21:32 am
That's worth the price IMO!

Dana does amazing work.
Title: Re: Acetaldehyde in Lagers
Post by: mainebrewer on April 25, 2021, 11:31:42 am
You may want to try transferring your beer into the keg before it is completely finished. Purge the keg (either a sani or fermentation purge), when the beer is almost finished fermenting (3-4 points remaining) do a closed transfer to the keg and let the beer finish in the keg. The yeast in the beer will use up any remaining O2 in the keg and when the beer is finished it will be fully carbonated. A spunding valve will be helpful in monitoring the CO2 pressure in the keg.

Not saying not to try this, but some of the ways mentioned to avoid acetaldehyde is by not racking too early.

Several of the previous suggestions were oxidation and questioning the CO2 purity. This would pretty much eliminate those from consideration.
Title: Re: Acetaldehyde in Lagers
Post by: RC on April 25, 2021, 07:06:39 pm
There's always the chance I'm just tasting something different, and it's not acetaldehyde. But, that's my best guess. Fits the descriptors perfectly. Whatever it is is certainly not welcomed in my lagers!  ;D

For $30, you could get it tested.

https://oregonbrewlab.com/products/#offflavor

If it's really driving you nuts, it might be worth it.

If I already know a certain off-flavor is in my beer, then wouldn't these off-flavor tests just be telling me what I already know?
Title: Re: Acetaldehyde in Lagers
Post by: hopfenundmalz on April 25, 2021, 07:42:46 pm
Here is a reason to make sure your Keg is purged and the CO2 is as pure as you can get - when alcohol oxidizes it becomes acetaldehyde. Just saying.

Analysis of a beer for acetaldehyde would remove doubt. Why do I say this? Some yeasts produce apple esters. Not green apple, but ripe red Apple. We think apple=acetaldehyde, and that is not always true.

A test would say how much acetaldehyde is there. All beer has acetaldehyde, the goal is for it to be below human threshold.
Title: Re: Acetaldehyde in Lagers
Post by: erockrph on April 25, 2021, 08:42:28 pm
Here is a reason to make sure your Keg is purged and the CO2 is as pure as you can get - when alcohol oxidizes it becomes acetaldehyde. Just saying.

Analysis of a beer for acetaldehyde would remove doubt. Why do I say this? Some yeasts produce apple esters. Not green apple, but ripe red Apple. We think apple=acetaldehyde, and that is not always true.

A test would say how much acetaldehyde is there. All beer has acetaldehyde, the goal is for it to be below human threshold.

Right. It seems odd to me that you're having acetaldehyde issues across so many beers. All of the explanations I've seen so far really seem like a bit of a stretch. Acetaldehyde isn't typically a common problem. I think that if you're having issues with multiple beers, then either you're a supertaster for acetaldehyde, or it's probably something else.

Any chance you could have a low level infection somewhere in your system? Maybe some microbe is producing another flavor compound that is coming across as apple?

Sent from my SM-G975U using Tapatalk
Title: Re: Acetaldehyde in Lagers
Post by: MNWayne on April 26, 2021, 07:22:14 am
Does the flavor present itself with other yeast strains?  What about ferment temps?  If you are only controlling ambient ferment chamber temperature without monitoring actual wort temp, you may be fermenting way warmer than you think.
Title: Re: Acetaldehyde in Lagers
Post by: hmbrw4life on April 26, 2021, 07:26:13 am
Wyeast 2308 Munich Lager pitched at proper rate after starter

Whats the "proper rate"?
Has this rate been verified with a scope and a count? If using a online calculator, I have found them from mildly to wildly inaccurate (but not one right). This is from scoping and actually counting.
Title: Re: Acetaldehyde in Lagers
Post by: majorvices on April 26, 2021, 07:44:09 am
Acetaldehyde isn't typically a common problem.

I disagree with this. It's one of the more common problems, especially in lagers. I think if it is a problem with process it becomes more evident in delicate lagers as opposed to stronger flavored lager.

Don't mean to set everyone barking up the wrong tree with the Co2 impurity comment either. Just the OP says he only noticed it after the beer was kegged and carbbed. Of course it seems like lots of off flavors work that way.
Title: Re: Acetaldehyde in Lagers
Post by: denny on April 26, 2021, 08:34:30 am
There's always the chance I'm just tasting something different, and it's not acetaldehyde. But, that's my best guess. Fits the descriptors perfectly. Whatever it is is certainly not welcomed in my lagers!  ;D

For $30, you could get it tested.

https://oregonbrewlab.com/products/#offflavor

If it's really driving you nuts, it might be worth it.

If I already know a certain off-flavor is in my beer, then wouldn't these off-flavor tests just be telling me what I already know?

I see the tests as confirming that what you think you know is correct.
Title: Re: Acetaldehyde in Lagers
Post by: majorvices on April 26, 2021, 09:01:03 am
Wyeast 2308 Munich Lager pitched at proper rate after starter

Whats the "proper rate"?
Has this rate been verified with a scope and a count? If using a online calculator, I have found them from mildly to wildly inaccurate (but not one right). This is from scoping and actually counting.

I've found the MR Malty calculator to be actually pretty accurate compared to cell counts I did in my brewery. In fact I had a new lab guy at one point in time who had horrible math and I used to the Mr Malty to double check his calculations. Obviously you can't tell viability but if you know the yeast is healthy and fresh you should get pretty close.
Title: Re: Acetaldehyde in Lagers
Post by: Homebrew_kev on April 26, 2021, 10:16:15 am
Any detectives out there who can spot what might be causing this? This is just one of about five lagers I've tried, some with different yeast, and they've all had acetaldehyde. I am at my wits end.

Sounds like oxidation to me. I'd check o2 exposure when cold crashing in regards to suck back. Also, when kegging - do a closed transfer if you can. If you can't, purge the keg with co2, then siphon in the beer (with the lid open) while pushing co2 in the gas post at a very low psi - close it up, and purge 3 more times.
Title: Re: Acetaldehyde in Lagers
Post by: majorvices on April 26, 2021, 12:20:50 pm
One of the things I have been doing to avoid "suck back" is to fill a collapsable bag with Co2 and attaching it to the blow off. Theoretically you should be able to attach it like a blow off to capture Co2. Then, when the beer cold crashes it just sucks back in the Co2 from the bag.


Here's the bag I have ben using (they have 1 gallon sized bags too)

https://www.usplastic.com/catalog/item.aspx?itemid=122655

Here's the valve that works on them

https://www.usplastic.com/catalog/item.aspx?itemid=136411
Title: Re: Acetaldehyde in Lagers
Post by: denny on April 26, 2021, 01:09:30 pm
One of the things I have been doing to avoid "suck back" is to fill a collapsable bag with Co2 and attaching it to the blow off. Theoretically you should be able to attach it like a blow off to capture Co2. Then, when the beer cold crashes it just sucks back in the Co2 from the bag.


Here's the bag I have ben using (they have 1 gallon sized bags too)

https://www.usplastic.com/catalog/item.aspx?itemid=122655

Here's the valve that works on them

https://www.usplastic.com/catalog/item.aspx?itemid=136411

I use the Grainfather pressure kit to pressurize the fermenter when I cold crash.  But I only have one of those.  If I have more than one going, I simply seal the other fermenters.