My first... stuck fermentation!

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My first... stuck fermentation!

Postby Changnoi » Fri Mar 15, 2019 11:44 am

Ok so I started a 25#, ~15gal sugar wash based on the Gerber technique, but I think I didn't sanitize well enough, and didn't pitch enough yeast. It went from 1.070 down to 1.032 and stopped. Smells a bit like vinegar, tastes a bit acidic. I don't have litmus paper or pH meter. I tried adding some baking soda and well-hydrated yeast, but after a couple days still no improvement.

Is there anything else I can try to mitigate? Should I pour it out? Or should I run it through the pot still for a stripping run, and then try to use the now sterilized sugar wash for another ferment?

Thanks in advance guys.
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Re: My first... stuck fermentation!

Postby OtisT » Fri Mar 15, 2019 1:38 pm

How have temperatures been for that ferment? Where did you start, has it held steady or were there big swings, where is it now, etc.? What is your yeast’s desired temp range?

How long did it take from 10 70 to when it stopped at 10 30? Do you use a bubble cap to see activity?

Underpitching yeast in a healthy ferment will still work, only it will take a little longer for the yeasties to multiply and do their thing. If your gear is dirty, I guess this would give nasties more time to grow. You saw a good drop in sugar, so they did multiple some and worked for a while. I don’t think underpitching is your problem.

If your temp is too low it may help to warm up the ferment and repitch.

I hate blaming this on Ph, but you could also just assume the Ph is low and bump it up also before attempting to restart. Having a pH meter is invaluable in troubleshooting stuck ferments. Put one on your wish list.

If you give up on this ferment I see no problem stripping it as is to see what you get. It will either turn out well or it won’t. There is a lot of sugar still in there, so it’s likely to foam/puke and it has the low potential to scorch.

I don’t think I would try to reuse the backset for its sugar content. I would dump it and start a fresh ferment.

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Re: My first... stuck fermentation!

Postby Changnoi » Fri Mar 15, 2019 2:00 pm

Thanks Otis, I'm leaning toward just cutting my losses but I want to get what little I can out of it, at least. Even if it's just cleaning supplies lol.

The fermenter has been on a crate next to a heater and maintained a steady 75-82F. We had a really cold snap and the floor isn't insulated but the temp of the fermenter didn't appear to change. It took about 2 weeks to get from 70 down to 30 gravity points.

I pulled some of the wash out, diluted it, added some yeast. It immediately sank to the bottom. I added some baking soda to that, shook it up, watched it for about 1.5 days. It seemed to perk up a little.

I was thinking if I run the pot still at low capacity to prevent puking, then the backset would have a bunch of dead yeast in it for nutrients for the new yeast?
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Re: My first... stuck fermentation!

Postby OtisT » Fri Mar 15, 2019 2:42 pm

You should be able to get something drinkable out of what you have. Stay positive my friend. :D

I would be worried that using this backset in your next basic sugar wash would introduce a bad taste/smell to that new ferment. You said this one did not smell right, so why risk it? Also, backset will increase acidity, and since you don’t have a PH meter that’s just asking for trouble. You are making a neutral, so stay a pure as possible and remember “happy yeast make a good neutral”. Read “Shady’s Sugar Shine” recipe for info on happy yeast.

I wish you good fortune in the cuts to come.

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Re: My first... stuck fermentation!

Postby still_stirrin » Fri Mar 15, 2019 4:17 pm

My thoughts...it’s too cold. 82*F is a little cold for bakers yeast unless it is vigorously fermenting, which you said it wasn’t.

Did you aerate the wash before pitching the yeast? It is very important to introduce oxygen prior to the start to give the yeast the metabolism to reproduce and populate adequately, especially if underpitching.

But, I think temperature is your problem...even more likely than pH crash.

And if you try to raise pH with baking soda (sodium bicarbonate), you’ll need a lot because sodium bicarbonate is a very weak base...meaning it doesn’t react strong enough with strong acids. In addition, when, or if you add enough bicarbonate to affect the pH, you’ve already added too much sodium, which can be harmfull for the yeast.

Calcium carbonate or calcium hydroxide are much stronger bases. I like to use pickling lime to raise the pH when needed. It gives the yeast calcium, which is a good nutrient for metabolism, and it is a much stronger base so you won’t need near as much. You can find pickling lime in the canning goods section at your local grocery store. It’s common.

But the thing that concerns me is the note that you said it smells like vinegar and tastes acidic (like vinegar?) If you’ve got a vinegar souring occuring because the yeast didn’t start properly or on time, the souring won’t give you much alcohol. You can try to run it, but it won’t produce much product...proof or volume. So good luck it that is the case.

Hopefully warming it up to the mid to upper 80’s will get the yeast going again. Hopefully.
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