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Ferment won't finish

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Dannit

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Hello all, first time here. I'm brewing my fourth batch of about 6 gallons of red wine. The other ones went fine, and soon after pressing (after between 7-9 days) they all finished fermenting right away. Well not this batch. It bubbles like crazy (about one bubble per second in the airlock) for about 6-7 days now, yet the Specific Gravity reading barely changes. From one day to the next--despite all the bubbling--it went from 1.003 only down to 1.002. I have given it some extra nutrients (a very small amount of Fermaid K yesterday, and three days ago a very small amount of DAP). Three days ago it smelled like hydrogen sulfide but that quickly cleared out after adding the DAP. And yet the SG reading barely changes from one day to the next, even though it looks to be fermenting vigorously. I smell and taste no signs of any volatile acids which may indicate bacteria. But I am worried that if it doesn't finish quick, that could become a possibility. And I am stumped trying to understand: If my yeast are not eating the sugars, then what are they eating?

Prefermentation I added 30ppm Potassium Metabisulfite.

I want to add my Malolactic bacteria ASAP to avoid having the wine sit there vulnerable between yeast and malolactic fermentations.

Everything I can find on "slow" and "sluggish" fermentations seems to address a situation that does not apply here: My yeast is obviously fermenting vigorously, yet the sugars don't go down.

Any advice? Thanks!
 

Boatboy24

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The bubbling could simply be the wine degassing. What was your starting SG? What are the ambient temps?
 

Dannit

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Hi, starting SG was 1.104, and the yeast I used is a high alcohol, L2226, which hasn't given me a problem on any other batches at the same starting SG. Temp has been a consistent 70F. It has now been 9 days since I pressed off seeds and skins, with no end in sight--still bubbles once per second through the airlock. I wonder--if it's just degassing--why my other batches didn't behave like this. (Weather is overcast and drizzly, but that's how it was with the other batches)
Anyway, today SG is at about 1.001, so it has gone down ever so slightly. But with as much bubbling as I see, I would have expected it to be done. Maybe it is mostly degassing but with a little fermentation still completing?

I'm just not sure what to do at this point. The smell and taste are perfect--no hints of this being some other microbe. (On the first couple days after pressing, it had a pretty strong hydrogen sulfide smell which went away after adding a very small amount of nutrient.) With all the gas rising, and apparently some very slow yeast activity, I guess it is somewhat protected? I am ready and waiting to pitch my malolactic culture, but wanted to wait until there was less activity before tossing it in--didn't want the MLB eating the remaining sugars. I also worried that the MLB would have a hard time getting started with all that activity. Perhaps I should just go ahead and do it now? Should I finish degassing it myself before adding the MLB? (I didn't on the last batches, but then they did not behave this way). I did treat the original must with 30ppm Potassium Metabisulfite, but as I understand, that should be long gone by now, or at least under the 10ppm threshold which Malolactic bacteria are supposed to be able to handle. (On my last batches I did not treat the must with sulfites before fermenting, so I wonder how that might have something to do with it.)
 

stickman

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I would not recommend adding the ML culture to a sluggish ferment, wait for AF completion before adding. The ML culture will only compete for nutrients and may cause the fermentation to stall completely. Do you have ML nutrients handy?
 

NorCal

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I’d leave it alone and let it finish. If you are getting that much activity, it is still in AF. Agree with @stickman , let it finish before adding mlb nutrients and mlb.
 

Dannit

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Thanks guys, that's what I'll do then. I wish I understood how it could bubble as much as it does yet the drop in sugar is so slight. Would you recommend splash-rack and return to oxygenate it and perhaps help it along? I've been hesitant to try that because when I did it with some cider that was going through the same thing, it completely stopped the ferment altogether.

As far as ML nutrients, I have Acti-ML and Opti Malo.
 

jgmann67

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Your wine has a lot of CO2 in it, apparently. I’m told that CO2 can throw off a hydrometer reading. Probably not a full 0.010, but it might be throwing you off some. Before you splash rack, or anything else, check your SG with a degassed sample (e.g. put your wine sample in a bottle and give it a few shakes, then pour it in your cylinder for testing). See if you get a different reading.

Personally, I’m on the coinoculation bandwagon from now on. Had difficult MLF two years running. But a coinoculation in 2018’s wine went without a hitch.
 

Dannit

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Interesting, I'll try degassing like you said from now on.
 

Dannit

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Sure enough--after degassing, a 1.001 reading went down to about .998. Almost there! (I knew about degassing before taking pH readings, but hadn't thought of how it could impact a hydrometer reading.)
 

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