Low FG's

[Rehlgood]

It seems like every beer I brew ends up having a FG of 1.008-1.010. Most of the time this is lower than the style allows and lower than any brewing software predicts. Even on a stout with a ton of adjunct grain I get a FG that is 2-4 points lower than style. I have tried regulating temps and my typical primary is 3 weeks then straight to a keg (unless dry hopping or using a secondary). Any ideas why my FG always goes so low or how to keep it in a specified range?

 

[fearwig]

Best bet is to add 2F to your mash temp until you find the sweet spot, and mash out if you don't already. I've had this issue too, and I don't think it's just about your thermometer calibration or anything. There are a lot of variables in the mash that determine fermentability, but temp is the one you can control best, so start there.

 

[m1batt1]

I'll also ask the obvious question of have you checked that your hydrometer is measuring correct? And how about OG? Is it always where it should be for the style and software predictions?

 

[Rehlgood]

Yes it is calibrated correctly. I do make the temperature adjustments when needed. My OG is generally within .002 of where it should be.


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[fearwig]

What I mean is that if you are having consistently low FG, you can increase your temps until it's on target and you know the offset you should apply to every recipe. If you're doing that and it works... congrats on finding a solution? Any other advice would probably involve picking apart your mash technique from head to toe. Low FG isn't usually about the fermentation part of the process, in short.

 

[Falcon3]

I was getting consistently low FG for a while and realized I was under pitching. Not rehydrating dry yeast or pitching a single tube of white Labs.


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[kcmobrewer]

I had problems with it in the past before I got good at mashing in. Temp fluctuation definitely seems to do it, for me anyway. Once I got that straightened out it's been fine. I have never mashed out either, not saying it won't help but I don't do it.

 

[beersk]

I was getting consistently low FG for a while and realized I was under pitching. Not rehydrating dry yeast or pitching a single tube of white Labs.


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This, I would think, would give you consistently high final gravities, not low.

 

[fearwig]

I was getting consistently low FG for a while and realized I was under pitching. Not rehydrating dry yeast or pitching a single tube of white Labs.

This can definitely be a factor too, more "daughter" cells can make for higher attenuation. But underpitch usually has other even more noticeable effects, which is why I didn't mention it, that's usually something you can root out with a sniff.

 

[Damoxemus]

I thought under pitching would result in a higher FG as well. What's this "more daughter" cells you refer to?

 

[Rehlgood]

I was getting consistently low FG for a while and realized I was under pitching. Not rehydrating dry yeast or pitching a single tube of white Labs.


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Not to say this isn't correct but wouldn't under pitching result in a high FG?

 

[Rehlgood]

This can definitely be a factor too, more "daughter" cells can make for higher attenuation. But underpitch usually has other even more noticeable effects, which is why I didn't mention it, that's usually something you can root out with a sniff.

Ok. Make sense I guess. I do make starters using a calculator so I think I am pitching the proper amount.

 

[Yooper]

Not to say this isn't correct but wouldn't under pitching result in a high FG?

Sometimes, but not always. Yeast does weird things when it has to work harder to produce enough cells for fermentation. Sometimes an underpitched beer will overattenuate- but not always!

 

[fearwig]

I thought under pitching would result in a higher FG as well. What's this "more daughter" cells you refer to?

Cells born in the wort rather than the veterans. It's not my term or idea, but basically younger cells may be more eager to attenuate away certain sugars, but as they age they are less inclined. So if you have a higher proportion of new cells born in your wort because you underpitched, it might skew the FG.

Here, I found the explanation that turned me on to the idea:
http://sciencebrewer.com/2012/03/02/pitching-rate-experiment-part-deux-results/

“Jason,

It is my suspicion that the overpitch achieves a lower gravity, as expected, because of the high numbers of cells available to do the work. The underpitch, however, eventually has a higher percentage of daughters vs older cells. The daughters have near 100% viability, high sterol levels and are raring to go, while older cells will have various viabilities, membrane condition, etc. Many of them may not be as ready for active fermentation as the daughters. I’d expect, therefore, for the underpitch to have a slower start than the overpitch or the control, but then to catch up pretty suddenly and attenuate well. Of course, all assumes relatively healthy yeasts, etc.”

I then asked if this is something they see in the brewery:

“I’d say yes, but only to a point. I think there is a curve to it. My gut feeling is that for a wort of average strength, you could cut the pitch rate from 30 – 50% and still achieve or exceed final attenuation vs a control. You’d have higher esters, but a revitalized (younger) yeast set afterwards. We will sometimes slightly underpitch when we want to put some more vigor back in a culture that otherwise seems healthy. Conversely, overpitching ages the culture – fewer daughters, over time, leaves you with a lot of battle-weary scarred cells with inflexible membranes that are no longer at their best. And not as many young, scar-free new cells.”

 

[Damoxemus]

Very interesting! Thanks for sharing that. It's amazing how much I need to learn about yeast.