Attenuation Problems

Hi Everyone!

My roommate and I started brewing about two months ago and just racked our third beer (a kölsch) into a corny for lagering. As we were doing so, we took a gravity reading and lo and behold, we again did not get the attenuation that we were looking for.

All three of our beers (an IPA, a Hefeweizen and the kölsch) have not attenuated as fully as we would have liked. The Hefeweizen and IPA finished at the same time, so we used basically the same procedure for both, before finding out that our attenuation was lacking. We used a starter for both, different yeasts and shook to aerate. We figured that the best thing to do to improve attenuation would be to use a larger starter and aerate better. So we decided to make a larger starter (1 gallon), which we aerated using a diffusion stone and allowed to come to peak activity for pitching. We then pitched the yeast cake (from the starter) and most of the starter and aerated for about an hour.

I'm really not sure what else we can do to improve attenuation, so I'm looking for suggestions. Thanks for the help!

And before you ask, here are the relevant stats on the three beers:

IPA
OG: 1.062
FG: 1.016
Target FG: 1.010
Attenuation: 74.2%
Fermentation Temp: ~68F
Primary: 8 Days
Secondary: 13 Days
Yeast: White Labs English Ale Yeast

Hefeweizen
OG: 1.052
FG: 1.020
Target FG: 1.016
Attenuation: 61.5%
Fermentation Temp: ~68F
Primary: 7 Days
Secondary: None
Yeast: White Labs German Hefeweizen

Kölsch
OG: 1.043
FG: 1.014
Target FG: 1.009
Attenuation: 67.4%
Fermentation Temp: ~60F
Primary: 20 Days
Secondary/Lagering: TBD
Yeast: White Labs German Kölsch

What are your mash temps?

all-grain or extract?

Some extracts don't attenuate very well.

Sorry, I guess I should have mentioned that. All three were extract and the IPA and Hefeweizen included steeping grains. I think it was a pound of crystal (20L) for the IPA and half a pound of chocolate for the (Dunkel) Hefeweizen. All of the extract came from MoreBeer and most of it was liquid, with DME additions to reach gravity.

I have the exact same issue. I just bottled my first batch last night (A Belgian Wit), and it had an OG of 1.043 and an ending of 1.021. Definitely did not get the attenuation the yeast calls for (76%). WLP400. Used extract with grains for steeping, plus a pound of honey.

According to my calculations, I got 46% attenuation. The beer tastes great though. What gives?

How are you aerating? If you are shaking, make sure you do it for a good 5 minutes.

You can get yeast nutrient from most homebrew supply stores. If you have not tried that, I would recommend giving it a shot. Add a little at pitching time.

Some yeast strains can have attenuation problems because they are very flocculant and tend to settle out early. Once the yeast collect on the bottom, they don't do much. If you are using a highly flocculant strain, you can occasionally rouse the yeast by gently swirling the carboy.

Some yeasts just aren't very attenuative in general. So while your recipe might call for a certain FG, you need to consider the actual attenuation capabilities of the strains you use and calculate your expected FG range from that.

I know you said it fermented at 68F, but are you sure it was stable at that temp? If there were overnight swings by a couple of degrees, the yeast can tend to flocculate more quickly and go dormant.

White Labs English Ale Yeast only has an attenuation of 63-70% so getting 74% is damn good.

As for your Hefeweizen and Klösh you did miss the mark.

Are your fermentation temps stable?

Are you certain that fermentation is complete by taking hydrometer reading over the course of 3-4 days to ensure your gravity is not continuing to drop?

Are you racking to a secondary (corny keg)? If so you may be racking too soon.

Are you temperature correcting your hydrometer readings?

Your Hefe, and Kölsh attenuations are about 72% at the low end, Hefe yeast in particular is a low flocculation yeast, so I would think your attenuation for the Hefe at least would be a bit higher.

Proper starter size, aeration, and stable fermentation temps should get your attenuation within the specified range for the yeast.

Some Extracts have alot of unfermentables in them leading to a poorer attenuation %, however, something seems amiss.

For the IPA and Hefeweizen we just shook the carboy, probably for less than five minutes (those things are heavy!!!). But for the Kölsch, we aerated with a diffusion stone for about an hour; it should have been close to the saturation point with oxygen. I will give yeast nutrients a shot on the next beer though (tonight!). Do you think it would help to aerate and/or shake fermenter on like day two or three of the fermentation?

And regarding yeast, the IPA attenuation wasn't bad at 74% and is probably about the max for the yeast, but the Hefeweizen yeast was anything but flocculant and had a pretty poor attenuation at only 61%. As for the Kölsch, that yeast is supposed to go to 80% or 85% attenuation, and we got nowhere near that, even with such a long fermentation.

The temperature was pretty stable, never more than 2F from 68F and probably 95% of the time between 67F and 69F. We used both wet towels and a lamp (beer protected from the light of course) to regulate the temperature.

And the Kölsch was very stable at 60F-61F, as it was in our cellar.

Over pitching the yeast can actually hurt attenuation. This was mentioned in this podcast:
http://www.thebrewingnetwork.com/membersarchive/bs_yeastrepitch03-23-09.mp3


I think most of your limitation is going to come from the extract. There's not much you can do about it. If you do a mash you can make adjustments and get more fermentable sugars. I've done a number of extracts and have seen poor attenuation in a lot of them. So I don't think the numbers your are seeing is out of the ordinary. If this bothers you, you may want to try a partial mash. All grain would give you even more control over this, but a partial mash is easier to do on the stovetop.

jar1087 said:

As for the Kölsch, that yeast is supposed to go to 80% or 85% attenuation,

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White Labs lists 78% for their Kölsch yeast, but if you could get 74% with their English Ale then you could probably swing 80% with the Kölsch.

Yeah your situation definitely seems strange, from what you describe your doing everything right.

Just trying to think of any thing else, what about pitching temps?

I didn't actually write the pitching temps down, but they were all maybe 3-4F higher than the fermentation temps. How would that affect things?

This may be a basic question, but is there any issue with under-attenuating? You get less alcohol...but is there any other real drawback?

muenchk said:

This may be a basic question, but is there any issue with under-attenuating? You get less alcohol...but is there any other real drawback?

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If I'm not mistaken if it doesn't fully attenuate, it could make the beer sweeter because there is excess sugar. Correct me if I'm wrong?

daveooph131 said:

If I'm not mistaken if it doesn't fully attenuate, it could make the beer sweeter because there is excess sugar. Correct me if I'm wrong?

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If you bottle unattenuated beer, the bottles coule explode from over carbonation.


I think the IPA was fine

The Hefe may have been racked too soon

The Kolsch could have come up a few degrees. The 60 was good to start, but you could have brought it up to 64 or so at the end to make sure it is done.

Leave all you beers at least 10 days, if not 2 weeks before doing anything.

Yeah, that's the main problem that I have with the under-attenuation. In the Hefeweizen the extra sweetness wasn't bad, but in the IPA and the Kölsch, it should really be pretty dry; the sweetness just doesn't fit the style very well.

The IPA just may not have enough bitterness. I don't think you are going to get the English yeast to go any lower. Try using a higher attenuating yeast, or more bittering, or both.

Or you could try replacing a little bit of the extract with sugar, maybe a half pound to help dry it out.

Sounds like the most likely cause is that the extract I'm using may not be as fermentable as partial or full mash wort. I'll have to read up on doing partial mashes, as I don't have the equipment for all grain yet...

jar1087 said:

Sounds like the most likely cause is that the extract I'm using may not be as fermentable as partial or full mash wort. I'll have to read up on doing partial mashes, as I don't have the equipment for all grain yet...

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Check out the sticky atop this page...partial mash stove top brewing.

daveooph131 said:

Check out the sticky atop this page...partial mash stove top brewing.

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You can do a partial mash on the stove. I've done it. It works. But if you can spare 20 bucks for a cooler, it will make your life easier. Any time you mash, you want to keep your temperature fairly constant. If you do it on the stove, I've found that you need to keep checking the temperature.