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mvierth

Stuck Rye Fermentation

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Hey folks! Any insight on a stuck rye fermentation? Some details:
 
264 gallon fermentation. 350 lbs malted rye and 90 malted pounds barley. Mashed in and cooked at 155 F.
 
Usual amount of conversion - 17 Brix/1.0698 SG. Original yeast pitch of 134 grams at 80° F. Agitated for oxygenation. Once rye forms crown on top, added sanitized PVC snorkels to give CO2 release and prevent acidification.
 
This is my standard mashing procedure with no deviations from procedure. Fermentation consistently has taken five days from yeast pitch to full attenuation and into the still. Maybe six with the colder weather.
 
However, after two days this fermentation only dropped 2 brix and then completely stopped. I checked pH and we're sitting at 4.5 (which usually hasn't given me any problems in the past).
 
I re-pitched 100 grams of yeast and re-agitated. No change.
 
I'm now at day 8 and it's still just sitting there. No change in Brix or SG. The pH has dipped down to 4.1. The grain crown has completely collapsed now with the grain settling on the bottom and the wash floating the top.
 
The first photo is of the fermentation's brother - happily bubbling away. The second one is my stubborn fermentation.

 

 

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4 minutes ago, Hudson bay distillers said:

sorry i dont know anything about fermenting rye but im curious about the pvc pipe stuck in the cap . never seen that before what is the science behind them . 

tim

So, because rye loves to ball together so much, it floats to the top and sticks together over the entire fermentation, creating a barrier that the CO2 can't get through. As the yeast starts to produce and release CO2, it starts producing acid that then kills off the yeast. Boom - stuck fermentation. 

By suspending the PVC pipes in the grain crown, it essentially works as a snorkel and gives the fermentation a chance to "breath" Keeps the pH level nice and steady and the yeast healthy enough to complete fermentation! 

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Someone elsewhere had suggested doing a iodine starch test to see if perhaps I had missed conversion during mashing. 

The iodine test was non-reactive, meaning conversion was achieved. 

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Have you considered not using all malted grains? Are you using any enzyme for conversion? We ferment thousands of gallons of rye a week I have never heard of your snorkel issue

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1 hour ago, SlickFloss said:

Have you considered not using all malted grains? Are you using any enzyme for conversion? We ferment thousands of gallons of rye a week I have never heard of your snorkel issue

I second this.  Exogenous enzymes are your friend of conversion consistency.   Did you acquire your malted rye and barley malt from the same place and is it from the same grain batch?

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The iodine test tells you that you have converted starch to sugar, but it doesn't know if they are fermentable sugars or not. So more than likely you have a mass of long chain sugars that haven't broken down because 155 fried the beta. You can throw in some beta as it sits, and it will take a few days to complete the breakout, or warm it up to 120 and it should convert pretty quickly.

add some more yeast after,  if you go the "warm up" route. 

Whats your current SG? I don't care about the brix

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134 grams of yeast in 1000 liters is a pretty light pitch, but if it’s worked for you before.

I second Roger - would dose glucoamylase, heat to 130c, cool and repitch.

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Thanks for the input, everyone. After a weekend of testing I was able to narrow it down to an issue of dying thermometers giving wildly different readings. As such, I failed to convert a large portion of the mash.

Dosed the gluco, heated, cool, repitched and we're back in business!

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