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Author Topic: Fermentation finishing too early, FG still in the 30's  (Read 1131 times)

Offline FMbb

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Fermentation finishing too early, FG still in the 30's
« on: May 29, 2020, 07:15:32 pm »
I have brewed this belgian tripel 4 or 5 times and the past 2 times, fermentation seems to finish too early. The yeast is a WY3522. I used to get a FG of 10 (1.010) but recently, gravity stalls at around 35. I gave it 8 weeks in the secondary but the last 2 weeks stayed at 35. I also frequently brew a dubel with WL545 on a recipe which is supposed to finish around 20 but recently I noticed it stalled at 33 (even after 7 weeks in the secondary). Last week I did an oatmeal stout with OG of 59, but same thing happened: FG stalled at 36. I use a SS cone bottom 6 gal fermenter with fairly tight temperature control. I have a mag stir plate and always do 2L starters for those fairly high gravity brews. I take my readings with a Brix refractometer which I calibrate to 0 with clear water.
Any thoughts on this?

Offline Kevin

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Re: Fermentation finishing too early, FG still in the 30's
« Reply #1 on: May 29, 2020, 07:24:17 pm »
This is just my way of doing things but I stopped using secondary fermentation a long time ago. Aside from the risk of oxidation you may be transferring the beer into secondary and leaving the bulk of the yeast in primary before it has finished doing its job. As for using a refractometer to check fermenting beer I am guessing you are using a conversion chart or tool to account for the presence of alcohol right?
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Offline FMbb

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Re: Fermentation finishing too early, FG still in the 30's
« Reply #2 on: May 29, 2020, 08:08:58 pm »
Thanks Kevin. The FG readings were 'neat' without any adjustments.

Offline FMbb

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Re: Fermentation finishing too early, FG still in the 30's
« Reply #3 on: May 29, 2020, 08:29:07 pm »
You make a good point about leaving most of the yeast behind in the primary, that is a problem. If I still want to continue to transfer my beers to a secondary (mostly because I like to control the first 24 hours in a cylindrical versus a funnel-top glass fermenter), so what if I would shake the primary just prior to transfer?, that should increase the amount of yeast being transferred for sure.

Offline Bob357

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Re: Fermentation finishing too early, FG still in the 30's
« Reply #4 on: May 30, 2020, 03:15:04 am »
Thanks Kevin. The FG readings were 'neat' without any adjustments.

In order to get accurate gravity readings with your refractometer you need to calculate the wort refractive index that is specific to your refractometer. After the onset of fermentation, when alcohol is present, you also need to use a calculator to convert your reading. Alcohol has a different wort refractive index than wort, so the Brix readings will not directly convert to SG.
I've included a link below that will explain how to do all of this. Be sure to read all of the information on the linked page and other pages that are linked from the page.

https://www.brewersfriend.com/refractometer-calculator/

BTW, using your numbers for the Oatmeal Stout, the corrected final gravity is ~1.019, which seems reasonable for the style.
« Last Edit: May 30, 2020, 03:20:11 am by Bob357 »
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Offline KellerBrauer

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Re: Fermentation finishing too early, FG still in the 30's
« Reply #5 on: May 30, 2020, 06:05:22 am »
I agree with all of the above — pulling the beer off the yeast way too early and using the wrong method to measure sugar content with alcohol present.  In my opinion, a calibrated hydrometer is the most accurate means of measuring sugar content before, during and after fermentation.
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Offline Kevin

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Re: Fermentation finishing too early, FG still in the 30's
« Reply #6 on: May 30, 2020, 06:54:46 am »
One last word on secondary fermentation from the guy who is a perpetrator of that myth. His words, not mine (homebrewtalk.com May 7, 2010).

The following exchange came from a section called ask the experts at homebrewersassociation.org March 15, 2013...

Tom from Michigan asks:
I have a few questions about secondary fermentations. I've read both pros and cons for 2nd fermentations and it is driving me crazy what to do. One, are they necessary for lower Gravity beers?

Two, what is the dividing line between low gravity and high gravity beers? Is it 1.060 and higher?

Three, I have an American Brown Ale in the primary right now, a SG of 1.058, Should I secondary ferment this or not?

Your advice is appreciated, thanks for all you do!

Allen from New York asks:
John, please talk about why or why not you would NOT use a secondary fermenter (bright tank?) and why or why not a primary only fermentation is a good idea. In other words, give some clarification or reason why primary only is fine, versus the old theory of primary then secondary normal gravity ale fermentations.

Palmer answers
:
These are good questions – When and why would you need to use a secondary fermenter? First some background – I used to recommend racking a beer to a secondary fermenter. My recommendation was based on the premise that (20 years ago) larger (higher gravity) beers took longer to ferment completely, and that getting the beer off the yeast reduced the risk of yeast autolysis (ie., meaty or rubbery off-flavors) and it allowed more time for flocculation and clarification, reducing the amount of yeast and trub carryover to the bottle. Twenty years ago, a homebrewed beer typically had better flavor, or perhaps less risk of off-flavors, if it was racked off the trub and clarified before bottling. Today that is not the case.

The risk inherent to any beer transfer, whether it is fermenter-to-fermenter or fermenter-to-bottles, is oxidation and staling. Any oxygen exposure after fermentation will lead to staling, and the more exposure, and the warmer the storage temperature, the faster the beer will go stale.

Racking to a secondary fermenter used to be recommended because staling was simply a fact of life – like death and taxes. But the risk of autolysis was real and worth avoiding – like cholera. In other words, you know you are going to die eventually, but death by cholera is worth avoiding.

But then modern medicine appeared, or in our case, better yeast and better yeast-handling information. Suddenly, death by autolysis is rare for a beer because of two factors: the freshness and health of the yeast being pitched has drastically improved, and proper pitching rates are better understood. The yeast no longer drop dead and burst like Mr. Creosote from Monty Python’s The Meaning of Life when fermentation is complete – they are able to hibernate and wait for the next fermentation to come around. The beer has time to clarify in the primary fermenter without generating off-flavors. With autolysis no longer a concern, staling becomes the main problem. The shelf life of a beer can be greatly enhanced by avoiding oxygen exposure and storing the beer cold (after it has had time to carbonate).

Therefore I, and Jamil and White Labs and Wyeast Labs, do not recommend racking to a secondary fermenter for ANY ale, except when conducting an actual second fermentation, such as adding fruit or souring. Racking to prevent autolysis is not necessary, and therefore the risk of oxidation is completely avoidable. Even lagers do not require racking to a second fermenter before lagering. With the right pitching rate, using fresh healthy yeast, and proper aeration of the wort prior to pitching, the fermentation of the beer will be complete within 3-8 days (bigger = longer). This time period includes the secondary or conditioning phase of fermentation when the yeast clean up acetaldehyde and diacetyl. The real purpose of lagering a beer is to use the colder temperatures to encourage the yeast to flocculate and promote the precipitation and sedimentation of microparticles and haze.

So, the new rule of thumb: don’t rack a beer to a secondary, ever, unless you are going to conduct a secondary fermentation.
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Offline spurviance

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Re: Fermentation finishing too early, FG still in the 30's
« Reply #7 on: May 30, 2020, 10:30:07 am »
You make a good point about leaving most of the yeast behind in the primary, that is a problem. If I still want to continue to transfer my beers to a secondary (mostly because I like to control the first 24 hours in a cylindrical versus a funnel-top glass fermenter), so what if I would shake the primary just prior to transfer?, that should increase the amount of yeast being transferred for sure.

Yes, but would also facilitate oxidation
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Offline dmtaylor

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Re: Fermentation finishing too early, FG still in the 30's
« Reply #8 on: May 30, 2020, 01:55:24 pm »
Thanks Kevin. The FG readings were 'neat' without any adjustments.

In order to get accurate gravity readings with your refractometer you need to calculate the wort refractive index that is specific to your refractometer. After the onset of fermentation, when alcohol is present, you also need to use a calculator to convert your reading. Alcohol has a different wort refractive index than wort, so the Brix readings will not directly convert to SG.
I've included a link below that will explain how to do all of this. Be sure to read all of the information on the linked page and other pages that are linked from the page.

https://www.brewersfriend.com/refractometer-calculator/

BTW, using your numbers for the Oatmeal Stout, the corrected final gravity is ~1.019, which seems reasonable for the style.

^^ THIS is the real answer.
« Last Edit: May 30, 2020, 01:58:36 pm by dmtaylor »
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