Looks like fermentation is stuck, what do I do...

[domaso]

Is the fermentation stuck? What do I do?

Hi,

To start I'm newbie here, but I'm not completely new to wine making, made a few pretty good batches last year, I'm always making wine from grapes and berries.

This question is about black currant wine. The starting SG was 1.115. After about 9 days I checked the SG and it was about ~1.040, today, (after 12 days in total) I checked again and it is still 1.038~1.039.
So, after 12 days in the cloth covered primary fermenter bucket I strained the must to a glass carboy and fit an airlock – no visible airlock activity... Shouldn't it bubble pretty fast with SG still at 1.040?

I'm suspecting one bad thing – there was a heat wave in my area the whole last week and the temperature was up to 93'F where the primary fermenter sat. I've just read the yeast packaging and it says: "Temperature range 57-90'F". Could it be that the yeast got overheated and killed? (I've read that the temperature of the must usually is even higher than ambient, so it could've been around 100'F..)

I now placed the carboy to 82'F area. What should I do - wait a day or two and see if there is some activity? Or should I buy another packet of the same yeast and re-pitch hoping it will kick start and eat the sugar that's left?

 

[domaso]

Also, if I try to re-pitch – could I use different red wine yeast? (I've just learned that the yeast I have used has been all sold out a few days ago...)
Any bad things when re-pitching with different yeast?

 

[sour_grapes]

Yes, I would certainly repitch a new batch of yeast. I would probably make a starter.

I don't think you will have any problems due to using different yeast. Some yeast have a "killer factor" that can kill other yeasts, which may be what you are remembering about not mixing yeasts. But if there are no yeast left to kill, it does not matter!

 

[domaso]

I don't know what happened, but this morning, ~12 hours after transferring to secondary the fermentation is going again – airlock bubbling fast and I clearly see the foaming/rolling in the neck. Maybe the yeast got roused when straining the must? Placing carboy in 10'F lower temperature may have also helped..

So I probably won't pitch more yeast just yet.

 

[sour_grapes]

Great news! Glad that worked out.

 

[salcoco]

some yeast nutrient would also help.

 

[domaso]

It kick started and going pretty aggressively now, doesn't seem like stopping soon. From the looks I think they'll eat that leftover 0.038 or more.

It looks like I created the thread a little too soon (probably needs to be deleted)... Anyhow, thanks everyone for suggestions/solutions!

 

[wineinmd]

Which yeast did you use? Perhaps the high heat caused them to floc out once they started getting to their alcohol tolerance and that cooling it down and rousing them got them started back up. I know how sluggish I get when it's hot and I get to my alcohol tolerance.

I wouldn't be terribly surprised if they don't get it all the way dry since it definitely sounds like they've been stressed. If they do give out completely, use a yeast with a high alcohol tolerance with a nice healthy starter.

I'd also be concerned about potential off-flavors considering how hot your must got. Some literature I've read says that if you push the upper limit of the yeast it might lead to "cooked" flavors, though I'm not exactly sure what that would taste like.

 

[domaso]

The yeast I used was "Cabernet Sauvignon Vintage Red" ("Enartis", Italian brand). Alcohol tolerance of 16%. Fermentation temperature up to 90°F.

If they don't get all the way dry, I would be even happier in this case.. I overdosed on sugar and with starting SG 1.115 if it goes completely dry, the alcohol will result in about 16.5%, I would be happier with something like 14.5%...

 

[wineinmd]

It's a bit of a waiting game at this point. Yeast are crazy little things, but I would bet on them conking out early. How early though, I have no idea.