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Stuck fermentation... I think

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Chemistry

NewBee
Registered Member
Dec 10, 2010
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I'm making a chocolate mead, I got the recipe off of another forum where the person did 6 different experiments with chocolate and I chose the one he said tasted best.

Here is the recipe for 5 gallons:
Nesquick chocolate powder - 32oz
yeast nutrient - 5 tsp
yeast energizer - 2 1/2 tsp
acid blend - a little less than 5 tsp
Clover honey - 15 lbs
spring water - filled to 5 gallons
Lalvin 71B - 10g, I let it rehydrate for 15 minutes using the instructions on the back of the yeast packet.
Fermenting in my basement at around 61-64 degrees Fahrenheit (probably closer to 61).

I mixed everything together 12/21/10 and the S.G is 1.131
I went downstairs to check on it and noticed it didn't bubble for over a minute. So I took a gravity reading and got 1.008.

I used a temperature correction program to convert my S.G from whatever it was at 72 degrees Fahrenheit. Since the mead is fermenting at around 61 degrees and I took it upstairs to do a gravity reading, the temperature couldn't have gone up more than a couple degrees so I think 1.008 is accurate enough (correct me if I'm wrong here).

The alcohol content right now is ( 1.131 - 1.008 ) * 131 = 16.1% alcohol.

The yeast is rated for 14% alcohol and my mead has an estimated 16.1% alcohol content after fermenting for only a week. I'm not sure if it is done fermenting or not. When the mead was in my hydrometer test tube I could see a couple bubbles coming to the top; I didn't know if that was just some CO2 coming out of solution or CO2 being formed by fermenting yeast.

I also made a 5 gallon traditional mead using roughly the same recipe minus the Nesquick chocolate powder and it is still bubbling away (maybe once every 5-10 seconds). Throughout the last week the chocolate mead has been bubbling more vigorously than the traditional up until today.

Any thoughts?
 
It's probably not stuck, it's probably closer to done. A week is far too soon to tell either way, but if you're at 16% abv with the 71B yeast, you probably would do well to not hold your breath for it to go much further.

If you wanted to see if you can eke out a little more activity from your yeast, moving it to warmer place is your best bet at this point. Otherwise, let it settle out a bit and rack it off the lees within a month or two. Congrats, sounds like a success!
 
Without seeming to cast aspersions on your figures, I'd say let it be.

As akueck points out, they indicate about 16% ABV, 71B is rated as having a tolerance of 14%, and while it's not a finicky yeast per se, it does seem that it sometimes has problems if used on a must of quite that higher gravity reading.

So I'd say that your efforts have been brilliant. It must have just balanced perfectly, so as to not only keep the yeast happy, but ecstatic.

I'd suggest that you leave it as it is, give it a week or so taking a measurement every second or third day. Then if you have 3 identical readings, you can presume it finished.

Then it's just a case of the finishing processes of clearing/ageing/bottling etc.

I don't think, from the figures that you'd be able to do much else with it, as the yeast cells would probably be pooped out, so there'd be little chance of carbonation, unless you can force carbonate it........

Well done.

regards

fatbloke

p.s. Oh and from the table I use, the drop from 1.131 to 1.008 is 123 points or about 16.7% ABV so I wouldn't be surprised to hear that it's a little "alcohol hot" to taste and would need some ageing i.e. 12 months plus.......
 
Thanks for the replies. I'm going to keep it in the cold basement until its finished because I don't want the alcohol content to go up any higher. I'm just surprised it has fermented this much in only a week.

How do you guys calculate alchohol content? One thread on GotMead? says to multiply the difference in gravity readings by 131. Stormthecastle suggests to divide the difference by .00736, which would give me 16.7% as fatbloke calculated. I'm just wondering which is more accurate.
 
Both methods are about equally (in)accurate, IMO. Those numbers you get are only good to within about half a percent. To get a more accurate number you need to send it in to be tested. Safe to say you've got somewhere around 16-17% alcohol.

[In case you're wondering why those calculations aren't very accurate, all you are measuring is change in density. You don't know how much sugar was used to create biomass (more yeast) and compounds that are not ethanol. Yeast drops out and contributes nothing to density, other compounds could be lighter or heavier than ethanol. Some non-sugar chemicals could have been changed or dropped out of solution too. But you can guess the ABV and be fairly close.]

[Bonus tidbit. Ever see labels that say "6.99% ABV"? The labels on commercial products also have a margin of error, and often you'll see them come close to some legal definition (e.g. cider is defined in the US as less than 7% abv). By no means does that label mean there is exactly 6.99% alcohol, but this way it (technically) comes in under the cap and still is within the allowable range even if a particular batch tests at 7.1%. Believers in significant digits, you can blame Congress.]
 
Chemistry said:
How do you guys calculate alchohol content? One thread on GotMead? says to multiply the difference in gravity readings by 131. Stormthecastle suggests to divide the difference by .00736, which would give me 16.7% as fatbloke calculated. I'm just wondering which is more accurate.
Click to expand...

The constant ranges from 128 to 136. So it's really not a constant!
The constant gets higher with the higher the ABV.
For low alcohol beers, it's 128
For high alcohol Meads it's 135
and lots of values in between.

So it really is just an estimate.
As most meads I brew are >12% I tend to use 133 (which is half way between the two constants you quoted)
(also 1 / 0.00736 = 135.9)

I hope this helps... I saw on here once somewhere, that there was a table of empirical data showing the correlation between the constant and the ABV.
 
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