Alcohol killing Yeast

[CallmeDave]

Hi,

I'm making some blackberry wine and have a SG of 1.11.
I'm using yeast with alcohol tolerance of 14%.
Can I assume once I get a FG of 1, which would be about 14.5% that all the yeast would be dead, fermentation would end and that it's safe to bottle or backsweeten?
Maybe these numbers are too close, what if the alcohol tolerance is only 10% and I have an FG that would calculate to 11%, can I assume all the yeast is dead and safe to bottle or backsweeten?

 

[BigDaveK]

No.
Yeast can't read. It may stop at 12% or it may stop at 16%. A few days of no SG change is a better indicator with a number closer to .990 being more likely.

First post! Welcome to the forum. I'll be starting a blackberry myself once I'm done harvesting.

 

[Rice_Guy]

welcome to WMT

The ABV specification is an approximation under ideal conditions, when yeast metabolism stops and they settle. (I did not say dead). Wine is a multiple variable preservative system. We do not have modeling which accurately explains how important nitrogen is vs pH vs free SO2 vs yeast strain vs alcohol (osmotic pressure) vs salt (osmotic pressure) vs anaerobic conditions and a dozen other factors.

As home wine makers we are “safe” if we keep the wine dry/ under 0.998 or pasteurize or add sorbate or even sterile filter. We are reasonably safe if the fermentation has held the same gravity reading above 1.000 for a month but I let stuck sit six months. Any time we back sweeten we are introducing some level of risk, and if the flavor is close to target I bottle without changing the sweetness.

 

[winemaker81]

Adding to previous responses, yeast is living organisms and no two colonies are guaranteed to be alike. Very similar yes, but not identical. As David pointed out, each batch is a separate set of intertwined conditions.

You can make a single must, then divide it into 2 buckets. Make a single yeast starter and divide it between the two buckets. Most of the time you will get identical results, but on occasion you'll get divergence. Why? Because unseen differences took the two along different paths.

If you want to backsweeten a wine, the easiest thing for home winemakers to do is ferment dry. Then stabilize with sorbate + K-meta, then backsweeten.

 

[sour_grapes]

Welcome to WMT! (I cannot add to the good advice already offered.)

 

[CallmeDave]

Thanks.... It's not an exact science and results may vary or diverge from expected results.
I guess my other option is to stabilize once wine gets to a flavour I like but in theory I'd get less alcohol and I'd have to take multiple samples of the wine.... which may be easy in primary fermentation but once it's in a carguy, I'm going to set it and forget it.

 

[Jovimaple]

Welcome to WMT!

 

[winemaker81]

Thanks.... It's not an exact science and results may vary or diverge from expected results.

THAT is a perfect summary!

I guess my other option is to stabilize once wine gets to a flavour I like but in theory I'd get less alcohol and I'd have to take multiple samples of the wine.... which may be easy in primary fermentation but once it's in a carguy, I'm going to set it and forget it.

Your choice is the wise choice.

Stabilizing wine (adding sorbate + K-meta) prevents yeast from reproducing. It does NOT stop an active fermentation. If you want to stop an active fermentation?

• Use a yeast with an ABV tolerance below the OG (which is amazingly imprecise, as yeast doesn't read the ABV tolerance chart).
• Add a spirit to jack the ABV well above the yeast's ABV tolerance level.
• Chill the yeast down to near 32 F and stabilize (doesn't always work)
• Bulk age the wine 9+ months to kill the yeast (doesn't always work)
• Sterile filter the wine (which may strip the wine)

The safest choice is to chaptalize to an SG that produces a desired ABV, use a yeast strain that can handle it, and stabilize/backsweeten the finished wine.

 

[CallmeDave]

THAT is a perfect summary!


Your choice is the wise choice.

Stabilizing wine (adding sorbate + K-meta) prevents yeast from reproducing. It does NOT stop an active fermentation. If you want to stop an active fermentation?

• Use a yeast with an ABV tolerance below the OG (which is amazingly imprecise, as yeast doesn't read the ABV tolerance chart).
• Add a spirit to jack the ABV well above the yeast's ABV tolerance level.
• Chill the yeast down to near 32 F and stabilize (doesn't always work)
• Bulk age the wine 9+ months to kill the yeast (doesn't always work)
• Sterile filter the wine (which may strip the wine)

The safest choice is to chaptalize to an SG that produces a desired ABV, use a yeast strain that can handle it, and stabilize/backsweeten the finished wine.

Thanks, I'm going to wait for fermentation to stop and than stabilize. Lets see what happens.

 

[winemaker81]

Thanks, I'm going to wait for fermentation to stop and than stabilize. Lets see what happens.

Bulk age at least 3 months. That gives the wine time to clear. You don't need to stabilize until you're ready to backsweeten.

 

[CallmeDave]

Just moved the blackberry juice from primary to secondary. Much more red and less black than I expected. Also took two SG samples just because I couldn't believe my results. Was at 0.990 after 1 week of primary fermentation which to my knowledge is very dry and "done". By my calculations, it comes out to 15.75% ABV. Is that normal? This was my first batch and I was surprised at 0.990 reading that I took another sample and it was the same thing. was expecting something closer to 1

 

[winemaker81]

Just moved the blackberry juice from primary to secondary. Much more red and less black than I expected. Also took two SG samples just because I couldn't believe my results. Was at 0.990 after 1 week of primary fermentation which to my knowledge is very dry and "done". By my calculations, it comes out to 15.75% ABV. Is that normal? This was my first batch and I was surprised at 0.990 reading that I took another sample and it was the same thing. was expecting something closer to 1

Your results sound normal.

I've had wines go from 1.100 to 0.995 in 4 days -- if the conditions are right and the yeast is hungry, it happens.

A lot of folks misunderstand the FG. Specific Gravity is the ratio of the density of a liquid with respect to distilled water (SG 1.000).

While sugar is initially the major differentiator and later alcohol, there are many other factors, things we don't necessarily understand. IME heavy red wines have a higher FG than much thinner whites and light fruits. Even the higher ABV of heavy reds doesn't push enough against the heaviness of other constituents.

Blackberry is not a heavy wine on it's own. It's got color, but it doesn't have the "gravity". It's not going to be a lightweight wine such as Pear, but it's not going to be an Elderberry, either.

Accept each wine on its own merits and enjoy it. In 10 or 20 years, this will all start to make sense!

The truly funny thing about my last statement is that I'm totally serious.

 

[CallmeDave]

Your results sound normal.

I've had wines go from 1.100 to 0.995 in 4 days -- if the conditions are right and the yeast is hungry, it happens.

A lot of folks misunderstand the FG. Specific Gravity is the ratio of the density of a liquid with respect to distilled water (SG 1.000).

While sugar is initially the major differentiator and later alcohol, there are many other factors, things we don't necessarily understand. IME heavy red wines have a higher FG than much thinner whites and light fruits. Even the higher ABV of heavy reds doesn't push enough against the heaviness of other constituents.

Blackberry is not a heavy wine on it's own. It's got color, but it doesn't have the "gravity". It's not going to be a lightweight wine such as Pear, but it's not going to be an Elderberry, either.

Accept each wine on its own merits and enjoy it. In 10 or 20 years, this will all start to make sense!

The truly funny thing about my last statement is that I'm totally serious.

I get it, I'd imagine a heavy drink like a Guinness would have a much differnt SG than an apple cider or something with same ABV. Now that the blackberry wine is "aging", I think I'm going to start another fermentation soon. I already have 2-3lbs of frozen blackberries, I can get another 1-2lbs in the next week or two... might add in some blueberries and/or strawberries since I have ripe fruit. We'll see what happens.

 

[David Violante]

Welcome to WMT!