Restarting Fermentation in a Wine that Finished too Sweet

[tomakana]

Hello all!

I've been brewing beer for a number of years now and have only recently begun playing with wine making through kits. I'm anticipating a small problem with my current batch and would love some thoughts. The kit is a 3-gallon Cabernet Sauvignon. In a nutshell, I suspect that my OG was above 1.110, which I realize was higher than it normally should be. Why I 'suspect' this rather than know it is a long and slightly embarrassing tale involving a late-night decision to start the kit, a probably poorly mixed batch of concentrate, and a bad refractometer reading. Regardless, I'm at the 3-week mark, and I think that fermentation has largely slowed if not stopped with SG currently around 1.015-1.017 and ~12-13% alcohol (I've had a pretty steady SG reading for 3-4 days now).

Taste-wise, the wine is definitely sweeter than I prefer, and based on the SG there's still a decent amount of sugars in there - the yeast included in the kit was Lalvin D47, which looks to have an alcohol tolerance around 14% which means I'm likely bumping up against the alcohol tolerance, even if it continues to drop in secondary. Based on the calculators, if I can get it to fully dry, it'll be 15-16%, so at/above the usual alcohol tolerance for the yeast, which I suspect means they'll be pretty stressed, which isn't ideal in my experience.

I think my main question is whether I should expect that SG to drop to dry eventually, and if it does, am I correct to worry about off flavors from the alcohol stress? If the answer to both of those is "yes" then what options do I have to get the fermentation going again?

I was considering either

A) diluting with distilled water to drop the alcohol percentage to something more reasonable (which would also serve to lower the final alcohol level to something more traditional) or

B) adding some higher alcohol tolerant yeast that I have on hand (which would potentially leave me with a 16%+ wine). I have Red Star Pasteur Red that goes to 16% and the Premier Cuvee that goes to 18%.

Thoughts from the group will be much appreciated!

Thanks,
Tom

 

[Maylar]

I'm not sure what a dilution would get you. Try it with a small sample if you choose to go that way. Restarting a stuck fermentation is a bit more involved than just dropping more yeast in there. See page 44 of this document:

Yeast Handbook

 

[keystonehb]

More than likely the D-47 will not continue for much longer unless you gave it a good dose of nutrients earlier in the process. Scott Labs also has this restarter sheet that you can use as well. It talks about using Go Ferm to rehydrate another yeast and slowly adding your current batch to it while tempering. However D47 seems like an odd choice for a cab sauv.

If all else fails and you do not enjot the product you can also try making another batch that is bone dry and see if by blending them you can find something a little more pallatable.

 

[tomakana]

More than likely the D-47 will not continue for much longer unless you gave it a good dose of nutrients earlier in the process. Scott Labs also has this restarter sheet that you can use as well. It talks about using Go Ferm to rehydrate another yeast and slowly adding your current batch to it while tempering. However D47 seems like an odd choice for a cab sauv.

If all else fails and you do not enjot the product you can also try making another batch that is bone dry and see if by blending them you can find something a little more pallatable.

Thanks, that's what I've been figuring based on everything else I'm looking at.

Regarding the D47, I'm 90% sure that's what it was because I remember noting to myself that I had just used D47 on a cider I made earlier this season. I didn't really think about whether it was good for a cab until I was looking up the alcohol tolerance. It was what William's included with the kit. There's a chance I could be wrong, but it was definitely a Lalvin yeast that I've used before for other things.

 

[tomakana]

I'm not sure what a dilution would get you. Try it with a small sample if you choose to go that way. Restarting a stuck fermentation is a bit more involved than just dropping more yeast in there. See page 44 of this document:

Yeast Handbook

Thanks - I was mostly thinking that dilution would lower the alcohol % to allow the remaining yeast to keep going for longer.

Appreciate the heads up that it's not necessarily as easy as just adding more yeast. Skimming the instructions, that makes sense now, but I hadn't thought that far ahead yet.

 

[Raptor99]

Your fermentation is not so much "stuck" as done, based on the alcohol tolerance of D47. Adding a yeast with a higher alcohol tolerance seems like the best solution. That might require some additional yeast nutrient, although I think that yeast have trouble making use of nutrients once the ABV is above 10%.

I would suggest making a vigorous yeast starter with a different yeast, so that you have a robust yeast colony, and then add that to the wine.

 

[tomakana]

Your fermentation is not so much "stuck" as done, based on the alcohol tolerance of D47. Adding a yeast with a higher alcohol tolerance seems like the best solution. That might require some additional yeast nutrient, although I think that yeast have trouble making use of nutrients once the ABV is above 10%.

I would suggest making a vigorous yeast starter with a different yeast, so that you have a robust yeast colony, and then add that to the wine.

FWIW, I ended up going down this path, in a way.

The "paused" batch is a 3-gallon Cab Sauv, so I got 1-gallon Cab kit and got it going with a higher-tolerance yeast (one that should get to 16-17%). Once the new kit was vigorously fermenting, I racked the two of them together and added a dose of yeast energizer. The SG in the new mixture went from ~1.016 to ~1.025 (don't have the specific number handy, but it was mid-1.020s).

Things paused for a bit, but then the whole batch got going again, and I'm now officially below where I was - last reading was around 1.012. I'm guessing I won't get completely dry, but it should end up less sweet than it was, which is what I was hoping for. Taste and smell is still reasonable, so I don't think I've created anything too off-putting in the process.

Once it's done fermenting this time, I'll rack and sulfite then let it bulk age for a while. Be interesting to see how it ends up!

 

[bernardsmith]

For the future, another possible solution might be to hydrate some champagne yeast and treat the problem batch as if it was a stalled batch. In other words, you begin by doubling the volume of the hydrated yeast, and when that begins to show real activity, you again double the doubled volume and you repeat this process until all the wine has been transferred atop the new yeast. The thing is that champagne yeast is designed (OK cultured) to be very active in relatively high ABV wines: it is used AFTER fermentation has ended to carbonate sparkling wines in the bottle, so high ABV and low pH does not bother the yeast.