Acetaldehyde help

Hey guys. Just joined up to see if I could pick your brains regarding possible infection or oxidation or what on my latest batch. I've recently finally moved on from splitting recipes into 2 Mr. Beer Kegs to using a fermenting bucket with airlock...This is my second batch in the bucket...first batch was a Northern Brewer brown ale that I bottled rather quickly that has turned out pretty decent after 3 weeks in the bottle...

Now on to this batch. It is a spiced winter ale kit from Northern Brewer, with some additional DME...and cinnamon and orange peel to up the spices and try to bring it to a real Winter Warmer status.

http://www.northernbrewer.com/shop/spiced-winter-ale-extract-kit.html

OG of 1.069
Possible underpitch of only 1 packet of Safale S-04.
Slow, fairly cool fermentation at 65-66 degrees.
FG of 1.020 after a week or so.

Tried to rouse yeast to see if I could knock off another point or so and was possibly too rough with the bucket...AKA could have sloshed around some leading to oxidation issue???

Warmed up to 70, to again see if I could get the FG down a couple more points...Nothing happened, so stopped messing with it. Figure an attenuation of ~70% with that yeast pitch probably wasn't too bad all in all.

Brewing in a bucket with spigot, so able to draw off samples fairly easily...
At 2 weeks, smells wonderful, big spice note to the nose, a bit sweet as expected.
At 3 weeks, spiciness subsided some, green apple taste creeping in.
Between 3 and 4 weeks, green apple taste became stronger...
At 4 weeks, when I planned to bottle...taste still there.
Retested FG and it has rose to 1.022
4 week and a couple days(today). Seems like off-taste could be subsiding(??), definitely still there though.


So, possible caused of Acetaldehyde tastes....plus my newb thoughts...

1. Incomplete fermenation - possible since I probably did underpitch...although I got a reasonable attenuation out of it...
2. Oxidation - possible since was too rough with the bucket rousing the yeast...
3. Infection - probable...since I just had my microbiologist wife take some to work with her. So are we expecting 0 bacteria growth in our beer? I took the bung out this morning to look and there is no visible sign of infection. It looks like nice clean beer...no colonies of anything sitting on top. But my wife said there are some gram negative rods, gram positive rods and a few gram positive cocci. So there is bacteria in the beer. She is culturing it to get additional information.

Okay, if you've made it this far, thanks for reading. After all of that I'm basically wondering what my options are.

1. Do I consider it infected since there is the presence of any bacteria? Do I just call it a loss?
2. Do I continue to wait and test and see if the flavor goes away.
3. Do I actively try to help out? I have some yeast in the fridge...thought about making up a half gallon of starter with some DME. Once it starts fermenting, add it to the batch and see if the active yeasties can clean up or even find anything more in the original wort to convert...

Thoughts, opinions? Thanks so much for your time....

I have a few comments and questions:
1. Did you rehydrate your yeast? Pitching directly into wort, while sometimes recommended on the package, reduces your viable cell count.
2. Some extract batches stall out around 1.020, there are loads of threads about this that are probably worth a read.
3. Oxidation wouldn't be a major flavor contributor (especially in a spiced beer) after only 4 weeks unless you put this batch in a paint shaker.
4. Remember that this flavor can be associated with young beer and with a beer like this, 4 weeks is pretty young.

My main advice would be to wait it out, with plenty of patience. It will likely turn out fine.

However, your microbiological test results are concerning. What size of sample did you have your wife test? A small sample with that much bacterial diversity would be a big red flag, your contamination rate seems pretty high. Of course, most of our beers have bacteria in them, our goal is to outcompete the bacteria with yeast, but in some cases, very few bacterial cells can produce detectable off-flavors.

If the apple flavor is the only off flavor you are tasting, I would say bottle and wait.

1. I'm a dry pitcher. I've read much on the differnet camps... Agreed on the concept and for something this big I should have at least rehydrated... Or pitched another packet.
2. Also have read quite a bit on the 1.020 extract curse. After 17 batches of extracts all finishing up below that(last was a Nut Brown at 1.009...before that a Saison that finished at 1.005) I lean on the side of the fence of that being anectotal or passed forward from a time of poorly processed extracts...not saying it doesn't happen, but I can't blame it being an extract brew first...
3. Good to know. That was just one of the things I've seen in my search for sour apple off flavor.
4. Hope this is the case. Worried that it was a little late in appearing...hoping it cleans on up...

As for the obvious bacteria...I gave her a few ounces in a sterile specimen cup...I think she just identified on the microscope today. Didn't ask about cell count. A culture should give type tomorrow. Will ask how prevelant it looked...

Acetaldehyde is a fermentation product usually only present in fermentation or very young beer. It's actually quite an unusual flaw to have in ales, but S-04 can throw it. It usually means that fermentation hasn't finished properly, which is easily explained by your 1) underpitch 2) of unhydrated dry yeast into 3) a high gravity beer. The higher gravity wort you pitch dry yeast into, the greater cell death you have, so you underpitched this batch worse than other beers you've made.

When yeast are rehydrated from the dormant dry state, they are briefly unable to regulate what passes into their cells from the environment. Being immediately flooded with a low-pH sugary protein-y soup of nutrients is no fun. "This kills the yeast cell." The stronger the wort, the less fun this is and the fewer cells survive the process.

A properly fermented beer (particularly an ale) should have no acetaldehyde present after a week because it should be more or less done fermenting by then. I'd say you've stalled out due to an underpitch and so the yeast weren't able to clean up their mess. Your best bet would be to pitch a very active starter (high krausen) of a neutral ale yeast like US-05. They'll get to work on the remaining sugar and re-metabolize the acetaldehyde.

daksin said:

Acetaldehyde is a fermentation product usually only present in fermentation or very young beer. It's actually quite an unusual flaw to have in ales, but S-04 can throw it. It usually means that fermentation hasn't finished properly, which is easily explained by your 1) underpitch 2) of unhydrated dry yeast into 3) a high gravity beer. The higher gravity wort you pitch dry yeast into, the greater cell death you have, so you underpitched this batch worse than other beers you've made.

When yeast are rehydrated from the dormant dry state, they are briefly unable to regulate what passes into their cells from the environment. Being immediately flooded with a low-pH sugary protein-y soup of nutrients is no fun. "This kills the yeast cell." The stronger the wort, the less fun this is and the fewer cells survive the process.

A properly fermented beer (particularly an ale) should have no acetaldehyde present after a week because it should be more or less done fermenting by then. I'd say you've stalled out due to an underpitch and so the yeast weren't able to clean up their mess. Your best bet would be to pitch a very active starter (high krausen) of a neutral ale yeast like US-05. They'll get to work on the remaining sugar and re-metabolize the acetaldehyde.

Click to expand...

I'm definitely hoping for something like this, but my beer had no acetaldehyde present after a week...nor did it after 2 weeks...it was 3 weeks in before the flavor showed up. That's what has me concerned...

I did make up a starter and pitched it...now I'll just sit back and wait another week and see how things end up.

But I'm afraid the issue is ultimately going to be a sanitation issue causing infection. The micro results definitely show a high amount of what appears to be aerobic gram positive Lactobacillus... Further reading tell me Lactobacillus can cause a sour taste, so perhaps I'm misidentifying my off flavor...

Anyway, I will give it another week. Check the taste...if it has cleaned up or hasn't worsened I will go ahead and bottle. Hopefully, being in the bottle will help kill off any aerobic bacteria...not sure... As long as it ends up tasting ok, I'll assume the bacteria won't kill me.

Ah, I totally missed that little bit of information. Good luck!

Well, went ahead and called it beer and put it in bottles.



Not the most horrible looking infected beer you can find online...still not sure how much of the off flavor is infection and how much is bad yeast management... I do know that after pitching 1/2 gallon of 1.030 starter that my FG dropped back down to 1.020 after letting it ferment back out. Right now the taste isn't undrinkable...that why it's get to go ahead and go in the bottle... If it doesn't worsen, then I can drink it as is and call it a learning experience.

I would call it a little tart right now...hoping since the majority of the bacteria appear to be aerobic that sealing it off with come CO2 production in the bottle will help stall any activity from the gram positive Lacto... I'll check back in after a month or so and let you know how things are turning out...

sorry to bring up a really old thread, but how did the beer turn out in the end after bottle conditioning?? I'm having a similar issue to the one you described (tasted fine when I took a sample after 8 days in the fermenter, but sour after 3 weeks in the fermenter), and I'm wondering what's going on.
Cheers!