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Weird second fermentation

Yeast & Fermentation
#1

I have had this happen several times. I still secondary all my beers because I like more work and cannot justify being more efficient. No, seriously, I brew in buckets and use the secondary process to free up buckets, allow a little more aging and clarifying and because I am still excited about seeing part of my beer before I put it in a glass. Going from bucket to keg just seems too “production oriented” to me.

My normal process is that I brew, primary goes normal, control temps in low to mid 60’s, generally two weeks minimum in primary. I rack when I can tell it is done. I had been doing extract and sometimes I was not getting my FG as low as I would like, but when the foam drops and the SG is stable, I rack to secondary, generally between two and 3 weeks. Secondary is generally a week or so for normal beers, then I cold crash and keg if I have an open keg. Often I have to wait a little longer to wait for a keg to kick.

For the last several months I have been brewing double batches, meaning two completely different brews in one session. After racking to secondary (I know it is not too early) I let the batches condition at room temps (65-75). This has happened 3-4 times now. One of the two, after about a week in secondary, with stable warm temps, will start to bubble again. Then a thin layer of foam develops and keeps growing. It is slow to grow but it does increase. The two brews that I have in secondary now are extract version of the Midnight Beatdown Wheaten Porter and Waldo Lake Amber. I think it is the Porter that this second fermentation is happening to.

In the past it has happened to a Caribou Slobber and an Oatmeal Stout. The Caribou Slobber (keg just kicked) was my second batch and was clearly different than my first. Less sweet, and seemed “thinner”. Very little mouth feel. Just like something was missing. The Oatmeal Stout is really good, but is not at all sweet, not that I expect sweetness from an oatmeal.

I am really curious what is causing this secondary fermentation. It seems that this has happened with different yeast strains. I am pretty (100%) sure it is not an infection. Should I let it go forever or cut it off when this starts by cold crashing?

#2

how are you sure this is not an infection?

#3

Does the gravity drop? If so, you have either some contamination, or a stalled fermentation that’s picked back up in the conditioning vessel. There really aren’t any other options.

If the gravity doesn’t drop, then it’s probably just CO2 off-gassing as the beer warms up.

#4

I guess I cannot be 100% sure that this is not an infection, but in the past there have been no offensive smells or flavors when I let this go.

I would have to check, but I think the gravity dropped about half a point after letting the oatmeal stout go like this for about 10 days to 2 weeks, after sitting dormant for about a week in secondary.

And this batch has been up to temp for well over a week before this started 2 days ago. Both batches currently in secondary sat for a solid week at room temps with zero activity before this one restarted.

All of these are darker extract beers. Is it possible that it takes this long for some of the “unfermentable” sugars to start to do something?

#5

[quote=“560sdl”]Both batches currently in secondary sat for a solid week at room temps with zero activity before this one restarted.
All of these are darker extract beers. Is it possible that it takes this long for some of the “unfermentable” sugars to start to do something?[/quote]
In that case, you can be all but certain that it’s a contamination or stalled fermentation.

You could be seeing a wild yeast strain getting started on the longer sugars that aren’t fermentable by the Saccharomyces. It would make sense that the Brettanomyces or whatever it is would have more to work with given all the long-chain sugars in the dark extract.

#6

[quote=“a10t2”][quote=“560sdl”]Both batches currently in secondary sat for a solid week at room temps with zero activity before this one restarted.
All of these are darker extract beers. Is it possible that it takes this long for some of the “unfermentable” sugars to start to do something?[/quote]
In that case, you can be all but certain that it’s a contamination or stalled fermentation.

You could be seeing a wild yeast strain getting started on the longer sugars that aren’t fermentable by the Saccharomyces. It would make sense that the Brettanomyces or whatever it is would have more to work with given all the long-chain sugars in the dark extract.[/quote]

So is this a problem? Is a contamination an infection, per se? Should I let it go or cold crash and keg? Or should I let the Brettanomyces do their thing?

#7

Beer isn’t alive, so it can’t be infected (nit-picking, I know). Contamination is really only a problem if it tastes bad. This might be a good excuse to replace any plastics that contact the wort/beer. Making sure you’re cleaning and sanitizing everything thoroughly. Maybe switch sanitizers for a few batches.

A stalled fermentation is easy to fix. Make sure you’re pitching enough healthy yeast and not fermenting too cool and/or dropping the temperature during fermentation. And verify that gravity readings are stable for a few days before racking to the bright tank.

#8

Thanks.

I am going to temporarily hold on to the theory that it is a dark extract related issue and that the Brettanomyces (not sure what they really are) have woken up and are doing their thing on the wort that normally does not ferment. Or at least, most people don’t have the patience to let it go this far.

I will mark this better bottle carboy and keep an eye on it and I will also monitor if this happens again now that I am going to all grain. Brewing first all grain batch this weekend

#9

hi 560, i just ordered the partial mash of the midnight beatdown also. :cheers: . i know im new to this and dont have much credibility, but what yeast did you use. i got the kit with the us 05 dry yeast, and i used this same yeast on my rye ale. i noticed while reading the packet that it contains ~1% wild yeast. could it be possible that once the dominant yeast recede, once they complete fermentation, that the wild yeast might start to eat some of the carbohydrates that the other yeast could not? maybe not just a thought. anyway glad your beer is coming out tasting fine, and good luck.

#10

LOL me too.

I think the yeast is just working on the trisaccharides and more difficult sugars at the warmer temps. Unless you transferred of something lately it’s probably not Brettanomyces. Brett needs a micro-aerobic environment to thrive and a long time to bring down the sugar levels. The activity you describe sounds like the activity that happens when I take a yeast slurry out of the refrigerator.

#11

Well I checked the gravity after several days of the renewed activity and there was no change in the gravity. So I want ahead and cold crashed and kegged last night. Sample was pretty darn good.

@hr - I used the recommended liquid yeast, I cannot remember the strain at the moment. I am sure it was harvested and plenty of it.

#12

Hello,

Could the difference in gravity be cause by the temperature difference? 60F → 75F would show up as 1 point lower…

#13

[quote=“FredrikHagman”]Hello,

Could the difference in gravity be cause by the temperature difference? 60F → 75F would show up as 1 point lower…[/quote]

I don’t think so. The beer was very stable in secondary for nearly a week before this started and then it continued for several days before I decided to cold crash it and keg. The gravity was stable and did not go down any noticeable amount during the three days the activity occurred. Final Gravity was up around 1.017 but I sort of expected that for a dark extract beer.

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