Author Topic: Stalled fermentation?  (Read 354 times)

Offline F16pointy

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Stalled fermentation?
« on: February 19, 2018, 05:09:07 AM »
Hello, newby here. I have been brewing all grain for about a year now. But it seems that most batches I cook up end up not reaching their attenuation. I typically hit the target OG and ferment in a temp controlled freezer in a glass carboy. An example is my last batch was an IPA and it hit about 65% attenuation. I pitched 2 Safale US-05 packets into the 5 gallons of 1.066 wort. I have read I should get about 72-74%. I noticed the gravity wasn't moving at all after about 4 day. So I transferred to a new carboy and pitched another packet of the same yeast. Still came in to low about 1.022 after I let it sit for 2 more weeks. I was fermenting at about 68 F and moved up to 72 F. I am sure its got to be something I am missing? I use yeast starters for liquid yeast & nutrients, I aerate by shaking the carboy. So could this be an issue of not using say a stone and O2? Any help is really appreciated! Thanks!

Offline mainebrewer

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Re: Stalled fermentation?
« Reply #1 on: February 19, 2018, 11:15:59 AM »
More info is needed about your process. Such as, grist components, mash temp, etc.
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Re: Stalled fermentation?
« Reply #2 on: February 20, 2018, 12:30:38 PM »
It sounds like a mash issue, possibly.  Are you getting full conversion?  Is the thermometer reading correctly? Among other things, a single infusion mash on the very high side would likely leave you with unfermentable dextrins in the wort.
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Offline MNWayne

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Re: Stalled fermentation?
« Reply #3 on: February 22, 2018, 09:21:18 PM »
Yeah, I suspect the mash. Test the accuracy of your thermometer. A big yeast starter couldn't hurt either.

Offline Adam

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Re: Stalled fermentation?
« Reply #4 on: February 23, 2018, 07:09:54 PM »
Can you please post your recipe and mash temperature?
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Offline James K

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Re: Stalled fermentation?
« Reply #5 on: February 23, 2018, 07:56:39 PM »
Two packs of US-05 should be plenty of yeast regardless of shaking the carboy or using an air stone to aerate, and you said you pitched more after you put the beer into secondary? I might not have transferred after day 4 I usually wait 10 days.  I am not sure how you raised your temp with the controller but I gradually increase temperature, usually after a few days at the starting temp.

All in all, without knowing your mash schedule and grain build it is hard to say what might be happening. Did you use any ingredients/nonfermentables that typically lead to higher end gravity?
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Re: Stalled fermentation?
« Reply #6 on: February 23, 2018, 08:06:11 PM »
Everything points to wort fermentability. Assuming the mashing period is at least an hour, the culprit is likely temperature being too high. Verify the accuracy of the thermometer. The best way is to compare with a certified lab standard in a water bath around 150F to 160F. The second best way is to check with boiling water. Verify what your boiling point is at your elevation (altitude for flyboys).

Another fermentability reducer is the use of high amounts of crystal malts. Less than 10% of the grist is OK for crystal in order to achieve good fermentability.
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