Pervasive Acetaldehyde

I've developed an apparent system-wide issue with my beers. Acetaldehyde. This is a relatively new problem, so I'm trying my level best to ferret out how it's popping up in my beer. Here's the skinny...

Two beers in a row... both have that green apple jolly rancher smell and flavor, almost overwhelming when it reaches room temperature. The first is a doppelbock that was brewed in a group brew in early November. It followed what I consider a typical fermentation... six weeks on primary, two day diacetyl rest, then two months' lagering. The 20 gallon batch was split five ways, and we all pitched our own yeasts and brought them home to ferment. The wort was aerated with an aquarium pump and stone. The yeast starter was 1.5L for 4 gallons. Of note is that of the other four guys, none have developed any acetaldehyde character, which leads me to believe the issue had to have begun at the pitch or afterwards.

The next beer was a kolsch, brewed in February. 1L starter, three weeks on primary, then kegged and cold-conditioned for three more weeks before serving. This batch was not significantly aerated.

So, here's what these two beers have in common:
- both fermented in a white plastic ale pale bucket (without gasket)
- both yeasts prepared in a beaker with starter wort, similar sanitation practices, no stir plate used
- both were kegged in separate kegs, but my racking procedure was the same for both (autosiphoned into a cleaned and StarSan'd keg from elevated vessel)

From what I have read, there are four likely culprits for acetaldehyde... unhealthy yeast or underpitching, racking off the yeast too early, re-introduction of oxygen post-fermentation, and bacterial infection. I honestly don't feel that I'm pulling my beer off of the yeast too soon... it's the same fermentation periods that I've followed for four years, and this is the first time this particular off-flavor has popped up. I feel that it's possible that oxygen is creeping into the beer via the ale pales, but it's my understanding that it takes much longer for that to become apparent. O2 can be entering the beer as I rack from vessel to keg, but there is very little agitation, and no more contact with ambient air than any bottling/kegging procedure (I'm assuming).

This leaves me with unhealthy yeast, or contamination as the likely problems.

I wanted to get you guys' input, particularly if anyone has had this problem pop up and solved it... what did you do?

For a while I had trouble with acet... but my issue resolved when I started kegging. Since you already are kegging, it appears I cannot offer much help. I am curious though, do you remember where you read that "re-introduction of oxygen post-fermentation" may cause acetaldehyde? That intrigues me a bit.

Good luck!

-TH- said:

For a while I had trouble with acet... but my issue resolved when I started kegging. Since you already are kegging, it appears I cannot offer much help. I am curious though, do you remember where you read that "re-introduction of oxygen post-fermentation" may cause acetaldehyde? That intrigues me a bit.

Good luck!

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Acetaldehyde reduces to ethanol, and that is a reversible process.

Given that this happens with different yeasts, and it just starting happening and now happens for every beer, I would guess infection.

-TH- said:

I am curious though, do you remember where you read that "re-introduction of oxygen post-fermentation" may cause acetaldehyde? That intrigues me a bit.

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From the Wiki, among other sources:

https://www.homebrewtalk.com/wiki/index.php/Acetaldehyde

remilard said:

Acetaldehyde reduces to ethanol, and that is a reversible process.

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My first thought when I pondered the possibility that oxidization was behind this was "Wouldn't I also be getting lots of diacetyl?"

The other common element that didn't occur to me are the kegs. These are the second and third beers I've ever kegged. I feel really confident in my cleaning and sanitizing of the kegs, but I wonder if I don't need to replace my vinyl hoses and hammer my autosiphon with a good long Starsan bath?

Also, the guys in my brewclub seemed to feel that I should try fermenting in Better Bottle/Glass Carboy and see if that doesn't restrict O2, or possibly remove the contaminated plastic bucket.

I would address the cheapest and easiest possible solution first-- the pale. If the pale has been used for many years its quite possible it has enough micro-scratches that it might be introducing infection. That being said this is only from what I have read. Best of luck. Keep us posted with your findings.

Make that bucket a grain storage bin and replace it. They are not expensive and not worth creating another bad batch for. I think I pay about $15 for a bucket and lid.

Oxy your kegs and rinse out with starsan. Honestly, I doubt very much it's oxygen in the system.

Yeast problems are very easy to solve. Make them better. There's tons of info on pitching yeast, so it should be very easy to follow proper procedures and amounts.

Thanks for the input, everyone. I've officially retired my plastic buckets. With any luck, this is just a bug I picked up in the plastic. I'll be rocking a weizenbock/dunkelweizen partigyle this weekend, so I sure do hope that blasting my after-cooling gear with my usual strident course of StarSan will keep things clean and green apple free!

Sounds to me like a yeast issue. You would not be picking up enough O2 to notice, and you should be having other off-flavours if you have serious contamination. You mention a time schedule for your fermentation. What about SG readings? Just because it took 6+2 days to ferment the lager last year does not mean it will not take 8+2 days this time around. I always start the D-rest at 75% of expected attenuation. Yeast does not listen to fixed time frames.

Are these your first 2 batches doing lagers/hybrids? What temp did you ferment at and how did you control?

I've brewed kolsch before with no problems.

The doppelbock was my first lager. The doppelbock was fermented in a chest freezer with a Johnsons Control set for 55 degrees, and remained undisturbed for 21 days (give or take). I pulled the bucket out of the freezer and allowed it to sit in my basement (air temp was around 65 degrees) for two days, then returned it to the chest freezer where I stepped it down to 36 degrees, where it lagered for about two months.

Here's a follow-up on my acetaldehyde issue.

Six batches have been brewed and consumed in the same keg equipment since my problem, and none have had a problem with acetaldehyde. At this point, I'm going to call oxygen the culprit. I have never agitated my kegs since these two batches, and I've moved to an oxygen-free racking method.

It is still possible that sanitation may have been an issue, or that for some reason my yeast starters for these batches were unhealthy... but I feel these aren't likely.

In my case, anyway... Keep those yeastie beasties healthy folks!

Did you end-up retiring the buckets? I'm having an acetaldehyde issue and curious if you retired the ale pail(s).

I've also been having an acetaldehyde issue (I think; very green apple, fruity flavors...disgusting).

I believe I've narrowed it down to three possible factors: infected buckets, pitch rates, or fermentation temperature control. I'm really thinking that it's the fermentation temp control. Although I do ferment in a large water bath, I haven't ever really tried to watch or control the temp of the bath. I'm planning on doing a crude D.O.E. this weekend to try and eliminate all possibilities at once. Hopefully I'll find out the culprit.

Sorry if none of this is coherent. Election night drinking games are a *****.

I have also had this problem with my last three beers, all in different fermentation buckets. This has never happened before. All of the beers tasted normal after about 10 days fermentation. When I tasted them again a couple of weeks later they had a cidery green apple flavour.

The first beer I transferred to a carboy and added gelatin, and threw some tin foil over top as I had no more bungs to fit the carboy. I figured I would buy one the next day..I forgot about it for two weeks. I blamed oxidation and my own mistakes for that one.

The second and third beers were brewed days apart, and fermented in a part of my house that was about 66F. This temp has been fine for the last year, with no issues. I tasted two weeks ago and they were good, now they taste like green apples. In the last couple of weeks our heat has come on and that area is now a few degrees warmer. I'm wondering if the warm temperature is what caused the flavours?

I'm sort of confused, because I've fermented many beers in the 68F range with no problems.

Rubes said:

I have also had this problem with my last three beers, all in different fermentation buckets. This has never happened before. All of the beers tasted normal after about 10 days fermentation. When I tasted them again a couple of weeks later they had a cidery green apple flavour.

The first beer I transferred to a carboy and added gelatin, and threw some tin foil over top as I had no more bungs to fit the carboy. I figured I would buy one the next day..I forgot about it for two weeks. I blamed oxidation and my own mistakes for that one.

The second and third beers were brewed days apart, and fermented in a part of my house that was about 66F. This temp has been fine for the last year, with no issues. I tasted two weeks ago and they were good, now they taste like green apples. In the last couple of weeks our heat has come on and that area is now a few degrees warmer. I'm wondering if the warm temperature is what caused the flavours?

I'm sort of confused, because I've fermented many beers in the 68F range with no problems.

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Did you ever figure this out?
I am having a similar issue.

I don't think I've had any more major cases of it, but this one was involving fruit, in my case, and I hear that can increase the chances of acetobacter.??

Ive had this problem a few times over the years and its always caused by a fermenter not truly sealing properly. That's my assessment though as Ive never read anything conclusive its just the only common denominator. I seem to have it more commonly with larger batches as well...like 10-15 gallons fermented together. I recently used a Brute trashcan as a fermenter and couldnt get a seal. Opened it two weeks into fermentation and it was apple city. I know people have open fermented for years but maybe the yeast they used was different.

DylanTO said:

Did you ever figure this out?
I am having a similar issue.

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I think it was caused by an infection. Most of the beers looked fine, but the last one that I had this problem with was obviously infected, it looked absolutely disgusting. The last two beers I brewed were fine, and the things that the bad beers had in common were the same two plastic fermenters.