Strange Attenuation problem...lower OG beer attentuated less than higher OG beer

[ChuckieG]

So I'm brewing a London Bitter in two strengths using a parti-gyle method. This was supposed to be a Fullers ESB and Fullers London Pride, 10 gallons of ESB and 20 gallons of Pride. Targeted OGs were 1.058 and 1.047. This is an all grain brew, mashed at 149F. I didn't sparge enough and ended up with lower than anticipated volume after boil, and higher than targeted OGs, 1.08 and 1.056. I had prepared a 2 gallon starter from a fresh smack pack of Wyeast W1968 and pitched a little over a quart into each carboy containing about 4.5 gallons of wort, cooled to about 65F. Six days later, the strong brew is at 1.024, which equals 70% attenuation, which is normal for W1968. I'd like to get it down lower, towards 1.016-1.018 if possible, but for a 7.35% abv brew, 1.02ish will be ok. The lower OG brew, however has only attenuated 40%, to 1.034, or 2.89% ABV. This is problematic, unless it just takes longer and keeps coming down. Fermentation peaked after 4 days, and was never super vigorous. The starter was never super vigorous either. In previous similar brews, I've had this yeast blowing off like crazy but not so this time. Fermentation temperature has been steady at 66F. The only thing I did very differently this time from previous times is where I usually shake the carboys vigorously to oxygenate, this time I used a air pump and stone and bubbled each carboy for about 5 minutes. (I'm getting pure oxygen soon. I got a tank and aeration stones but still need to fill it and to get a regulator.) Any ideas or suggestions on what to do from here? I just added some yeast nutrient to the four carboys that are at 1.034 and shook them, hoping to crank up the yeast a bit. Just waiting another week I'm sure the FG will be lower, but I worry when I see the gravity remaining so high after the fermentation has slowed. Strangest to me is why would the 1.056 OG beer attenuate so much less than a 1.08 OG beer? I would have expected the opposite... Perhaps I should make up another fresh starter and add it and see if that helps? If oxygen is low that might not help. If I had my oxygen set up ready I'd jack that up but I don't. For my strong beer I'm thinking that I could select another higher attenuating yeast to attack the remaining sugars further in a secondary fermentation but I don't want to change the character of the beer a whole lot. Any ideas???

 

[ChuckieG]

I guess that post was too long and rambling for anyone to bother reading and replying. Oh Well I guess I'll keep them shorter in future.

Anyway, I still don't understand why the lower gravity brew fermented more slowly than the high OG beer. After adding nutrient and shaking, activity did pick up and has kept on going.

One other odd thing, I had some leftover from the starter, but it had slowed down. I added it to one of the carboys. That carboy more or less stopped fermenting while the others kept going. Go figure.

So I'm brewing a London Bitter in two strengths using a parti-gyle method. This was supposed to be a Fullers ESB and Fullers London Pride, 10 gallons of ESB and 20 gallons of Pride. Targeted OGs were 1.058 and 1.047. This is an all grain brew, mashed at 149F. I didn't sparge enough and ended up with lower than anticipated volume after boil, and higher than targeted OGs, 1.08 and 1.056. I had prepared a 2 gallon starter from a fresh smack pack of Wyeast W1968 and pitched a little over a quart into each carboy containing about 4.5 gallons of wort, cooled to about 65F. Six days later, the strong brew is at 1.024, which equals 70% attenuation, which is normal for W1968. I'd like to get it down lower, towards 1.016-1.018 if possible, but for a 7.35% abv brew, 1.02ish will be ok. The lower OG brew, however has only attenuated 40%, to 1.034, or 2.89% ABV. This is problematic, unless it just takes longer and keeps coming down. Fermentation peaked after 4 days, and was never super vigorous. The starter was never super vigorous either. In previous similar brews, I've had this yeast blowing off like crazy but not so this time. Fermentation temperature has been steady at 66F. The only thing I did very differently this time from previous times is where I usually shake the carboys vigorously to oxygenate, this time I used a air pump and stone and bubbled each carboy for about 5 minutes. (I'm getting pure oxygen soon. I got a tank and aeration stones but still need to fill it and to get a regulator.) Any ideas or suggestions on what to do from here? I just added some yeast nutrient to the four carboys that are at 1.034 and shook them, hoping to crank up the yeast a bit. Just waiting another week I'm sure the FG will be lower, but I worry when I see the gravity remaining so high after the fermentation has slowed. Strangest to me is why would the 1.056 OG beer attenuate so much less than a 1.08 OG beer? I would have expected the opposite... Perhaps I should make up another fresh starter and add it and see if that helps? If oxygen is low that might not help. If I had my oxygen set up ready I'd jack that up but I don't. For my strong beer I'm thinking that I could select another higher attenuating yeast to attack the remaining sugars further in a secondary fermentation but I don't want to change the character of the beer a whole lot. Any ideas???

 

[AnchorBock]

People don't generally like to read a wall of text so that may be why you didn't get any replies yet.

Am I reading this wrong or did you really only end up with 9 gallons of wort when you were aiming for 30 gallons? Maybe some process issue is coming into play during fermentation. Even if you did have your O2 setup you wouldn't want to add it this late in the game.

When I did the Fullers beers my ESB went from 1.060 to 1.012 and the London Pride went from 1.045 to 1.012 so I also got less attenuation with the LP. I'm not sure why either, the only thing that I can think of is that the LP was made up of more sparge wort (although I did some blending of worts).

 

[ChuckieG]

No, I ended up with about 25 gallons. In the end both beers fermented down to a FG of about 1.02. The high gravity beer just got there a lot quicker. I've read yeasts don't usually do as well starting out in higher gravity beers, but maybe with a nice big starter cranking along at full krausen, the yeast just just says yum to the higher gravity and chows it down even faster than the thinner grist.

It turns out the beer I added extra yeast ended at the same gravity as well, I think it sped through when I wasnt looking and I just thought it stopped early.

The remaining mystery is why the FG is 1.02 instead of 1.012-1.015. On that I am stumped. Maybe too high a strike temp increased unfermentable sugar levels. I struck a bit high and adjusted temp down in the mash tun. I think I'm going to switch to putting grain into liquor rather than vice versa.

People don't generally like to read a wall of text so that may be why you didn't get any replies yet.

Am I reading this wrong or did you really only end up with 9 gallons of wort when you were aiming for 30 gallons? Maybe some process issue is coming into play during fermentation. Even if you did have your O2 setup you wouldn't want to add it this late in the game.

When I did the Fullers beers my ESB went from 1.060 to 1.012 and the London Pride went from 1.045 to 1.012 so I also got less attenuation with the LP. I'm not sure why either, the only thing that I can think of is that the LP was made up of more sparge wort (although I did some blending of worts).