What is slowly "working out" at end of fermentaion?

[Dland]

Normally I'll rack from primary to kegs at about .006-8 left to go, this achieves carbonation though spunding and is also when I do a D rest for cold fermented lagers.

One way to tell yeast is done is the PSI in keg stops rising and is stable pressure for a day or so. Then I know it is a good time to ramp down and cold crash the beer.

I have a batch of a darker lager that keeps attenuating very slowly at D rest temp (around 64F). It is going up at less than 1 PSI per day. This batch does have some more complex sugars as it contains a little Melodian and Special B. Are these sugars still slowly being processed by yeast?

It has been at D rest temp for over a week now, and I would have cooled and crashed, but clearly there is still some yeast action going on.

I'll probably crash soon anyway, but am curious if prolonged D rest condition can achieve fermentation of otherwise less fermentable sugars. There are times when it could be a useful tool, perhaps, like if mash was a little warmer than intended. Or maybe I'm just making my beer stale a bit faster.

 

[RPh_Guy]

Normally I'll rack from primary to kegs at about .006-8 left to go, this achieves carbonation though spunding and is also when I do a D rest for cold fermented lagers.

One way to tell yeast is done is the PSI in keg stops rising and is stable pressure for a day or so.

You should set your spunding valve to the pressure required for full carbonation, which only requires about 3-4 gravity points fermentation. Therefore once the pressure stabilizes (at the level set by the spunding valve), fermentation is NOT complete if you're spunding with 6-8 points remaining.

I have a batch of a darker lager that keeps attenuating very slowly at D rest temp (around 64F). It is going up at less than 1 PSI per day.

Are you confirming with a hydrometer s.g. or is this just speculation?

Are these sugars still slowly being processed by yeast?

It's possible, depending on the strain and fermentation conditions. Any number of stressors can result in under-attenuation and/or sluggish fermentation/finish.
This has little or nothing to do with the malts used from my understanding.

A wild and/or diastaticus strain contamination could also cause a continued slow fermentation.

curious if prolonged D rest condition can achieve fermentation of otherwise less fermentable sugars.

Generally, no.

 

[Dland]

Thanks for the reply. In many cases I do not actually leave my spunding valves on the kegs, but check keg pressures daily to ascertain if yeast activity has completed. This is especially true if a particular batch was racked too late for full or optimal spunding. My reasoning being if keg PSI is still rising, at constant temperature, then yeast is still active.

I have not bothered to take another gravity reading, I could do so, but suspect with PSI rise of less than one pound per day, change in gravity over this period would be hard to detect with a normal home brew hydrometer.

I am not under the impression the fermentation has stalled, nor have I any reason to believe this batch is infected in any way.

I was under the impression that certain malts (the ones added for "body, mouth feel, & head retention"( eg the "caras", etc), add compounds that add to final gravity, and are not easily fermented by yeast. Melodian falls into this category, I believe.

 

[J_Flint]

You are correct in your assumption that the more highly kilned, roasted, and stewed malts contribute less-fermentable/unfermentable sugars to the beer.

I would not rely on pressure either static or otherwise to be indicative of anything. Pressure climbing could simply be due to the temperature inside the keg changing and CO2 that was previously dissolved from fermentation being released. The solubility of CO2 in a liquid changes based on that liquids temperature.

 

[Dland]

The temperature is constant, kegs are well insulated and heat controlled to 1 degree F, yet PSI is slowly climbing up, and not fluctuating within the 1 degree temp swing allowed by temp controller.

 

[RPh_Guy]

You are correct in your assumption that the more highly kilned, roasted, and stewed malts contribute less-fermentable/unfermentable sugars to the beer

However they do not slowly ferment over time. Otherwise beer couldn't be bottled and be shelf stable without pasteurization/sterile filtering.

The temperature is constant, kegs are well insulated and heat controlled to 1 degree F, yet PSI is slowly climbing up, and not fluctuating within the 1 degree temp swing allowed by temp controller.

Are you measuring the actual temperature of the beer?

If it is still fermenting, the s.g. will decrease. That's the only way you're going to know.

 

[J_Flint]

However they do not slowly ferment over time. Otherwise beer couldn't be bottled and be shelf stable without pasteurization/sterile filtering.

I certainly agree with you. I wasn't completely clear on that. Yes when the yeast has completed fermentation...it's basically done. Some strains may respond to rousing by eeking out a tad more attenuation, but generally it's completed its task.

I agree that the only way to know if it's done for sure is a couple hydrometer readings spaced a couple days apart. I'm unsure why some people are so hesitant to do this rather than stress out about airlock activity or in this case a pressure increase.

-EDIT- I hadn't realized OPs concern was the "slowly continuing fermentation. I stick to my assertion that the gravity should be checked to confirm whether or not this is happening. If it is in fact slowly dropping, being that it's been over a week, then my guess would be a diastaticus contamination.

 

[Dland]

Well, gravity is at 1.012, and pressure seems not to have gone up noticeably since yesterday. This is a little higher finish gravity than usual than normal for my brews with this yeast combo, but I usually use only more fermentable malts. (this one is somewhere in the marzen or bock territory, darker and sweeter than I usually like to brew).

But something was working off slowly at the end, my question was what compounds those might be. Esters or whatever? beneficial, detrimental or neutral to flavor?

Maybe 3-5 days not long enough for D rest, (I don't know, but have not tasted any diacetyl lately). If I were just going by hydrometer readings and "common procedure", I likely would have ended "rest" several days sooner, probably at around 1.0125 or 1.013. Small rise in PSI while spunding alerted me some sort of yeast action was still occurring.

All you yeast scientists, seeing infections and diasta-whatevers everywhere! haha some of us brew a lot of good beer with decent procedures and gear, even if our degrees were not in micro biology.

I don't have the ways and means to do the research, was just curious if someone knew what these more durable, yet fermentable compounds are.

There is something that has to be the last thing the yeasts process during fermentation. This batch is not the first I've noticed the "taper off" with, though it is not usually what happens in my brew cellar.

 

[RPh_Guy]

But something was working off slowly at the end,

Again, you don't know this without gravity readings to demonstrate that fermentation is occurring.
Pressure is NOT a reliable indicator.

my question was what compounds those might be. Esters or whatever? beneficial, detrimental or neutral to flavor?

Yeast eat simple sugars, maltose, and maltotriose. Some strains can break down dextrins.
That's it, other than utilizing FAN and trace nutrients during growth.

I likely would have ended "rest" several days sooner, probably at around 1.0125 or 1.013. Small rise in PSI while spunding alerted me some sort of yeast action was still occurring.

Did you measure those values?

 

[J_Flint]

It is quite common for fermentation to slowly wind down. I did not mean to sound like one day things would be hustlin' and the next it's dead. Some yeasts simply take their time near the end. I still want to caution you on pressure being any sort of indicator. IMHO it's just not a reliable indication of anything really.

A diacetyl rest need not be for more than a day or two usually. You're right there are compounds that the yeast work on when all the food sources available to them are gone, but these metabolic processes are different from actual fermentation and would not result in much if any additional CO2 production.

Also, not a scientist, nor do I have any background in microbiology. Just a nerd

As far as your finishing gravity goes, for a Märzen or Bock or other malty dark lager, I'd say anything below 1.015 would be a respectable number to hit. Just because it finishes high does not necessarily mean it will be overly sweet. I had an English mild with like 18% crystal malt finish at 1.015. It was only a 3.5% ABV beer and it tasted quite dry.

 

[ba-brewer]

Thanks for the reply. In many cases I do not actually leave my spunding valves on the kegs, but check keg pressures daily to ascertain if yeast activity has completed. This is especially true if a particular batch was racked too late for full or optimal spunding. My reasoning being if keg PSI is still rising, at constant temperature, then yeast is still active.

What pressure level do you use when don't keep the spunding valve attached all of the time, the pressure to full carbonation level or something below that?

Nothing to do with the continue fermentation issue, but when I have tried doing that it seems those kegs got over carbonated. I had the spunding valve set to the pressure of desired carbonation. Just looking to learn new tricks.

On the continued fermentation issue, I think yeast do use/consume certain sugar in a particular order like simple sugars first. In a none pressure situation I have not noticed any extended fermentation when more crystal or roasted malts where used, normally find it the opposite. Once in a while a fermentation just moves a little slower for no apparent reason.

I have had a diastaticus contamination, it took a couple repitches to get to the point it was obvious. I thought I sensed maybe a slight funk on the earlier pitch but they had normal fermentation/attenuation. The pitch it took over it was phenolic early on in fermentation. Fermentation progressed fairly normal but then kept moving lower. Don't recall the rate of attenuation being exceptionally slow compared to a normal fermentation.

edit: diastaticus yeast can be found in wild yeast, but more of the time it is self inflicted cross contamination. If you don't use known diastaticus yeast it is not usually a problem.

 

[Dland]

Thanks for the replies.

Yeast eat simple sugars, maltose, and maltotriose. Some strains can break down dextrins.
That's it, other than utilizing FAN and trace nutrients during growth.

So the common HBT discussions of yeast "cleaning up" esters and other stuff at end is more gobblety goop? I guess I would not be surprised.

I would assume and any metabolic activity of yeast would produce some gas, but perhaps not.

The gauges on in my spunding valves are far more precise than any hydrometer I'm likely to ever own. Perhaps they are sending me on snipe hunt, but I figure I'm detecting something, and monitoring pressure seems like a good way to avoid crashing too early.

I can easily measure a rough gravity, say at common target of 1.010-1.008 or so, but that does not always assure it has gotten as low as is possible with any particular brew. Some of my lagers I want as attenuated as I can get, within reason and the perimeters of yeasts I use.

 

[Dland]

What pressure level do you use when don't keep the spunding valve attached all of the time, the pressure to full carbonation level or something below that?

Nothing to do with the continue fermentation issue, but when I have tried doing that it seems those kegs got over carbonated. I had the spunding valve set to the pressure of desired carbonation. Just looking to learn new tricks.

If I shoot for 30+ PSI at cellar temp, I'm pretty close to the volumes of CO2 I want at crashed/serving temp of 30-32F.

Once I see I have hit 30 and it still seems to be working, I'll let off some gas. Often I end up under spunding a little because I don't always have time or energy after work to close transfer/rack in time for full spunding level. But I always make time to check pressure (and release as needed), usually twice a day.

When I do use spunding valves attached, I set a little above target PSI, as the ones I have tend to over vent when they release.

 

[J_Flint]

coSo the common HBT discussions of yeast "cleaning up" esters and other stuff at end is more gobblety goop? I guess I would not be surprised.

No. Yeast will break down some compounds after the attenuative phase is complete. They will break down diacetyl into other compounds that have a much higher flavor threshold. It is believed that some esters and phenolics can also be further metabolized but this is much less apparent. Regardless though, the only process during fermentation that generates any significant amount of CO2 is when the yeast are in the attenuative phase and actively consuming sugars. This is why the lag phase is called LAG. There is a lag between pitching and noticing airlock activity, or bubbling, pressure build, etc... There is still plenty of activity happening that we simply can't see.

The gauges on in my spunding valves are far more precise than any hydrometer I'm likely to ever own. Perhaps they are sending me on snipe hunt, but I figure I'm detecting something, and monitoring pressure seems like a good way to avoid crashing too early.

Even if your gauges are precise, it's not a reliable indicator of ongoing fermentation. Even a cheap hydrometer that is not completely accurate will still read a static figure. So you can monitor any change in gravity.

 

[ncbrewer]

I've always had concerns about using the standard hydrometers for reading FG. I like the narrow range bottling hydrometers.

 

[Dland]

I should have an FG hydro.

If anyone knows a good or pro grade hydrometer mfg or source, also would be good to know.

 

[J_Flint]

I should have an FG hydro.

If anyone knows a good or pro grade hydrometer mfg or source, also would be good to know.

I have the one from more beer.com and am happy with it.

 

[Dland]

I get my hydrometers from more beer now, was wondering if there was something more precise and hopefully durable out there.

 

[ba-brewer]

I bought some precision hydrometers from northern brewer and was not happy with them. They were only slightly easier to read but they were calibrated to 60F and most of my beers are finished close to 68F and even at calibration temp they were off by a point and half. To use them I had to consult a temp offset calculator and remember to add 1.5.
Lab Grade Hydrometer .980-1.020
Lab Grade Hydrometer 1.000-1.070

I see Williams brewing has a nice selection of precision hydrometers.

 

[J_Flint]

I get my hydrometers from more beer now, was wondering if there was something more precise and hopefully durable out there.

More beer has a finish-scale precision hydrometer. That's the one I was referencing. I've been happy with it. It reads up to 1.020 I believe. Very easy to read.

 

[RPh_Guy]

https://www.morebeer.com/products/final-gravity-hydrometer.html

I have this too, but I don't use it much. I'm a little afraid to touch it. I find the normal triple scale hydrometer to be adequate.

 

[Dland]

I have to wonder whether the accuracy gained by using a final gravity hydrometer would be offset loss of accuracy by using two different hydrometers on the same brew.

I've had a more than a few hydrometers over the years, and they all generally checked to zero in plain water, but I'm pretty sure they aren't precision instruments.

 

[J_Flint]

I have to wonder whether the accuracy gained by using a final gravity hydrometer would be offset loss of accuracy by using two different hydrometers on the same brew.

I've had a more than a few hydrometers over the years, and they all generally checked to zero in plain water, but I'm pretty sure they aren't precision instruments.

The need for precision is so overblown on the Homebrew scale. We aren't brewing beer that needs to be scientifically identical batch to batch, nor do we report out numbers for taxing purposes. All one needs to brew beer that is reliably enjoyable is CONSISTENCY. Even if they aren't super accurate they are going to yield a consistent reading. It's a very simple piece of equipment.

 

[RPh_Guy]

They are very accurate instruments if you do a 2-point calibration and are mindful of temperature when taking readings.
Precision is defined by the gradation; a normal triple scale is precise to 0.001 since it has markings every 0.002.

The need for precision is so overblown on the Homebrew scale. We aren't brewing beer that needs to be scientifically identical batch to batch, nor do we report out numbers for taxing purposes. All one needs to brew beer that is reliably enjoyable is CONSISTENCY. Even if they aren't super accurate they are going to yield a consistent reading. It's a very simple piece of equipment.

A reasonable degree of precision (not accuracy) is needed when making sure the FG is stable.

I think that's what you're trying to say, so I agree.

 

[ba-brewer]

morebeer has a 15% off sale on test and measurement equipment over the weekend Promo Code: M&TSAVE15

 

[Dland]

I'm mainly interested in making good beer, but sometimes I get curious about how it works and all, trying to keep the ole noggin active.

 

[J_Flint]

.
A reasonable degree of precision (not accuracy) is needed when making sure the FG is stable.

I think that's what you're trying to say, so I agree.

Precisely what I was trying to say. People have different understandings of the term so I was trying to be blunt. Does that make sense? Lol

OP I suggest if you like exercising your noggin to simply concern yourself more with repeatability and consistency between processes and individual batches. Change small variables one at a time. That's the only way you learn something in this hobby. I all too often make the mistake of getting ahead of myself and trying to change too much at one time and the end result is almost always more confusion. Either enjoy what you do and try not to worry about it, or try to keep yourself at a good pace for learning and observing.