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I did an all-grain rye for a mash and pitched with Premier Cuvee yeast (tolerant to 18% abv), 5 grams to 4 gal wort. Repitched it again and the forced fermentation test indicates that the mash is done at 1.030. Any ideas/suggestions? Should I check and adjust the pH if it is below 4?

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What was the original gravity? –  Tobias Patton Feb 16 '12 at 19:12
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Champagne yeast in an all-rye beer? This sounds a bit weird. –  Graham Feb 16 '12 at 21:24
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I am not surprised it stalled out if you used champagne yeast. Champagne yeast doesn't handle maltose very well. –  brewchez Feb 17 '12 at 0:00
    
Starting gravity was 1.030 before I raised the SG to 1.070 before pitching. I used champagne yeast because of the high sugar content and high desired ending abv. Thanks to all that comment as I am learning this process. –  drj Feb 17 '12 at 3:12
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The champage yeast went to town on the simple sugar, and then when it was left with the maltose it quit likely due to ABV content and being worn out from processing all the sugar. Any yeast will go after simple sugars first then more complex sugars later. Champagne yeast has a poor reputation of being able to work on wort sugars, it can to an extent but its evolutionary path is simple sugars like fructose and glucose found in grapes. –  brewchez Feb 17 '12 at 22:44
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2 Answers 2

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Wow, this brew is really giving you trouble! The high FG is most likely a problem with the mash, that it was too warm, producing a lot of unfermentable sugars, or that conversion was not complete, resulting in a lot of starch and cloudiness. Both will give you a high finishing gravity.

To try to fix this, you can add additional enzymes to break down the unfermentables into fermentables. One common source of enzymes is the dietry suppliment Beano. Another is the product known as Dry Beer Enzyme. The one time I used it, gravity fell from 1.015 to 1.002 - I don't recall the timescales, but at room temperature the enzyme needs a few days or more to break down the sugars.

One downside with adding enzymes to the fermentor is that it's difficult to control the final gravity. With hungry champagne yeast, you may end up consuming all the sugars, leading to a very dry and bitter beer.

EDIT: Regarding pH, I'd be surprised if your pH is below 4, unless there were lots of highly kilned malts and your water is soft. The optimal pH for fermentation is pH 4.6, although yeast will ferment below pH 4, just slower. In this paper, yeast continue fermenting down to pH 2.8.

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I wanted a very dry, almost rye whiskey taste, without distilling (illegal for me here in the US). I'll try the Beano. This is turning into a biochemistry experiment (not that I mind as a chemist :-)) Thanks mdma, you are contributing to my education on all-grain brewing. –  drj Feb 17 '12 at 3:17
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You're welcome. As brewchez mentions, you may want to review your brewlogs to see if there is anything in the process you can fix, so this problem doesn't repeat. I'd overlooked champagne yeast - it only ferments simple sugars, and not maltose and related sugars, which is normally a fermentable sugar with brewer's yeast. So the problem of unfermentability is just compounded and most of the sugars from the mash will be non-fermentable regardless of your temperature. The Beano will fix that, as it will break down maltose into simple sugars which the champagne yeast can ferment. –  mdma Feb 17 '12 at 9:13
    
Looked up the Beano deal and tried it. Happily, the grav is down to 1.010 and lowering after 3 days. Another tool in the kit. Thanks, mdma. –  drj Feb 22 '12 at 6:11
    
Great to hear!! –  mdma Feb 22 '12 at 11:27
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If you did a forced fermentation and it went down to 1.030, then that's it...its over. You have a process problem and pH or other things aren't the solution.

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