by hoochlover » Fri Oct 16, 2015 5:52 pm
I'm running a 16% brew atm using the same thing I used for my 8% brew, except just doubling the sugar. Some interesting things to take out of this so far.
1) At about 10-12% ABV the solution started to dissolve all the foamy shit on top. This amount of ethanol seems the right amount to quickly break down the E491 emulsifier which lingers on the surface of the brew, along with some dead yeast.
2) It was about 12% concentration when the yeast started powering down and the rate of CO2 release became slower and slower. Likely due to this increased dissolving. I think it got to 12% in 10 hours or so. And it needed another ~8 hours to get to 16%.
3) It finished consuming all the sugar in about 18 hours. So yes, 16% abv in ~18 hours at 30 degrees.
4) After finishing consuming the sugar the yeast are still going! How? Likely by eating themselves. The higher ethanol of the brew seems to be breaking down some of the yeast cell walls . This has kept the CO2 coming at a much lower rate now for an extra 6 hours, and doesn't seem like it's going to stop for at least another couple.
So the takeaway from just this one experiment proves a lot of what most distillers already know. Going to a higher ABV results in more fusels/esters because more yeast is destroyed which releases their unwanted contents in your brew. It also helps the fermentation linger longer than it needs to because the yeast are in this cycle of eating each other, increasing abv, more yeast die, they eat them, and so on. Which means it takes longer to settle, longer to settle also increases the chance of more yeast death and more unwanted crap in the brew.
At least for this bakers yeast you don't want to be going over 12% in my opinion, or even near 12%. This likely applies to all dried yeast in general because that E491 is going to get dissolved into your brew instead of just floating there, along with a bunch of other crap you likely don't want in there. Like most people on this site have already said many times it seems 10% is your safest top limit if you don't want so much extra crap dissolved. Even 10 may be too high. More investigation needed.