AG attenuation problem?

[Schnitzengiggle]

I brewed a sweet stout on 2/14/2010, the recipe is converted from an extract recipe that has turned out great twice. As an extract brew, this recipe has been well received by all of my friends and family.

Here is the recipe:

Type: All Grain
Date: 2/14/2010
Batch Size: 10.00 gal
Brewer: Broken Glass Brewery
Boil Size: 13.43 gal Asst Brewer: Shawn Dunn
Boil Time: 60 min Equipment: My Equipment - Brew Pot (15 Gal) and Coleman Xtreme Cooler (52 qt)
Brewhouse Efficiency: 80.00

Ingredients

Amount Item Type % or IBU
12 lbs 7.2 oz Pale Malt (2 Row) UK (3.0 SRM) Grain 68.68 %
2 lbs 0.5 oz Chocolate Malt (450.0 SRM) Grain 11.20 %
1 lbs 8.4 oz Roasted Barley (300.0 SRM) Grain 8.40 %
1 lbs 1.8 oz Wheat Malt, Ger (2.0 SRM) Grain 6.12 %
1 lbs 0.2 oz Caramel/Crystal Malt - 60L (60.0 SRM) Grain 5.60 %
3.00 oz Fuggles [4.80 %] (60 min) Hops 26.8 IBU
2.00 oz Goldings, East Kent [4.50 %] (15 min) Hops 8.3 IBU
1.00 oz Fuggles [4.80 %] (15 min) Hops 4.4 IBU
2.00 tsp Brewer's Yeast (yeast hulls) (Boil 5.0 min) Misc
2.00 tsp Irish Moss (Boil 10.0 min) Misc
2.00 Servomyces Capsules (Boil 10.0 min) Misc
2 Pkgs Irish Ale (White Labs #WLP004) [Starter 4000 ml] Yeast-Ale

Beer Profile

Est Original Gravity: 1.050 SG
Measured Original Gravity: 1.055
Est Final Gravity: 1.014 SG
Estimated Alcohol by Vol: 4.77 % Actual Alcohol by Vol: 4.56 %
Bitterness: 39.5 IBU Calories: 250 cal/pint
Est Color: 45.8 SRM

Mash Profile

Mash Name: Single Infusion, Medium Body, Batch Sparge
Total Grain Weight: 18.13 lb
Sparge Water: 10.01 gal
Sparge Temperature: 168.0 F

Single Infusion, Medium Body, Batch Sparge
Add 22.50 qt of water at 172.0 F
Step Time 60 min
Step Temp 155.0 F


Mash Notes: Simple single infusion mash for use with most modern well modified grains (about 95% of the time).

Notes:

1st runnings/3.5 gallons - 1.092 @ 79° = 1.094
2nd runnings/5.0 gallons - 1.039 @ 74.5° = 1.041
3rd runnings/5.0 gallons - 1.014 @ 71.5 = 1.015
Preboil volume = 13.5
94(3.5)+41(5)+15(5) = 329+205+75 = 609 total gravity points
609/13 = 1.047 preboil SG
609/11 = 1.055 OG

I forgot to actually take an OG before I sealed up my fermenters, but I did take my 1st, 2nd and 3rd run-off gravities which I used to estimate my gravity.

These have been in primary for almost 2 weeks (this Sunday 2/28/10 will be exactly 2 weeks). I normally primary for 3 to 4 weeks, so I plan on leaving these in the primary for at least 1 more week. Fermentation seemed to stall due to low temps ~4 days after fermentation beagn. I raised temps to 68-70 swirled fermenters and fermenntation restarted.

Today 2/26/10 (~ 2 weeks primary) I took an SG and it is 1.020 @ 70F= 1.021.

OG 1.055 to 1.021 is only 60.5% apparent attenuation, WLP004 has an attenuation range of 69-74%.

I did mash at 155F, so slightly higher, however, only 60.5% AT seems really low. It is almost 10% under attenuated.

Having said that the two extract versions I brewed had an AT of ~64%. The yeast I used had been in the fridge for almost 6 months, but I made a starter that assploded like a volcano:

This starter was made about 5 days before brewday. It was stepped up from 2 quarts to four, then chilled for 48 hours and decanted before pitching into the wort.

So I am having a hard time understanding why my fermentation/attenuation is suffering so badly.

Is it the age of the yeast?

Is it that the fermentation stalled?

Is it that WLP004 is a temperamental yeast (Again, I have only had as good as 64% AT with this yeast.)?

So, can anyone shed any light on my plight?

If the SG doesn't drop any further I'm going to bottle it next week, what do you think?

 

[Bobby_M]

It could be as simple as an out of calibration thermometer. What you thought was 155 could have been 158. Have you checked the thermometer out in icewater or boiling water?

 

[Grizzlybrew]

Well, not being an expert, I would point out that more than 30% of your grist are grains with fairly unfermentable starches/sugars. In your extract version, ho wmuch of the grist was base extract? (also keep in mind, the extract was probably mashed lower than 155 also.)

Other than that, I'm not sure. Have you roused the carboys/fermentor?

 

[StAnthonyB]

I brewed a sweet stout on 2/14/2010, the recipe is converted from an extract recipe that has turned out great twice. As an extract brew, this recipe has been well received by all of my friends and family.

Single Infusion, Medium Body, Batch Sparge
Add 22.50 qt of water at 172.0 F
Step Time 60 min
Step Temp 155.0 F

Today 2/26/10 (~ 2 weeks primary) I took an SG and it is 1.020 @ 70F= 1.021.

OG 1.055 to 1.021 is only 60.5% apparent attenuation, WLP004 has an attenuation range of 69-74%.

I did mash at 155F, so slightly higher, however, only 60.5% AT seems really low. It is almost 10% under attenuated.

So, can anyone shed any light on my plight?

If the SG doesn't drop any further I'm going to bottle it next week, what do you think?

The final gravity you have achieve is within the typical sweet stout style, but I would mash at a lower temperature. Try mashing at 152F and let the mash go longer (when mash temperature is lowered enzyme activity slows but is more efficient at breaking up various chains of sugars). This lower mash temperature will make your wort just a tad more fermentable.

And, Bobby is right. Check the calibration of your thermometer.

 

[KayaBrew]

FWIW, I have an analog and a digital thermometer that I calibrate every time I brew. Bobby is right...start there since it's the simplest thing, then troubleshoot from there.

 

[Schnitzengiggle]

It could be as simple as an out of calibration thermometer. What you thought was 155 could have been 158. Have you checked the thermometer out in icewater or boiling water?

I have checked my Thermometer, and it is a thermapen. Temps are spot on. I did end up mashing at 155F for 90 minutes due to a trip to the store that took longer than expected.

Well, not being an expert, I would point out that more than 30% of your grist are grains with fairly unfermentable starches/sugars. In your extract version, ho wmuch of the grist was base extract? (also keep in mind, the extract was probably mashed lower than 155 also.)

Other than that, I'm not sure. Have you roused the carboys/fermentor?

There is a considerable amount of unfermentables in there, and with a 155F rest temp, I'll assume that many of the longer chains of sugars were not completely broken down. However it is still only 60% AT, and that seems low.

The final gravity you have achieve is within the typical sweet stout style, but I would mash at a lower temperature. Try mashing at 152F and let the mash go longer (when mash temperature is lowered enzyme activity slows but is more efficient at breaking up various chains of sugars). This lower mash temperature will make your wort just a tad more fermentable.

And, Bobby is right. Check the calibration of your thermometer.

I wanted more body and mouthfeel to this brew, hence the 155Frest temp. Plus I ended up mashing at 155F for 90 minutes, so whatever was going to convert obviouslymust have.

FWIW, I have an analog and a digital thermometer that I calibrate every time I brew. Bobby is right...start there since it's the simplest thing, then troubleshoot from there.

My thermo is not the problem, would anyone have anyother suggestions as to why I have uch a low AT?

Bear in mind the yeast has been in my fridge for a good 6 months could that be an issue, even though I had what appeared to be a good starter?

 

[KayaBrew]

I don't have any new ideas. It sounds like you did everything right.

About 7 months ago, I brewed an AG Oatmeal Stout from Jamil's "Brewing Classic Styles". I did everything spot-on according to his recipe. I even pitched 2 packs of S-05, and after all that my FG was a whopping 1.024. Well, they've been in the bottle for 6 months now, and it's a disgusting beer. Way to sweet (duh!) and very "thick". I gave away 30 bottles and dumped the rest down the drain today. My only failure in hundreds of gallons.

 

[Schnitzengiggle]

I don't have any new ideas. It sounds like you did everything right.

About 7 months ago, I brewed an AG Oatmeal Stout from Jamil's "Brewing Classic Styles". I did everything spot-on according to his recipe. I even pitched 2 packs of S-05, and after all that my FG was a whopping 1.024. Well, they've been in the bottle for 6 months now, and it's a disgusting beer. Way to sweet (duh!) and very "thick". I gave away 30 bottles and dumped the rest down the drain today. My only failure in hundreds of gallons.

This is really weird, my extract version went from OG 1.064 to 1.022, so that was decent, but 1.055 to 1.022 ain't so great, so far this is my only AG fialure. Having said that, it is only my 4th AG brew, and everything else I brewed has been awesome!

I'm thinking maybe it is a yeast issue, WLP004 hasn't seemed to attenuate very well for me.

I have a vial of WLP007 in my fridge, so I'm thinking of trying that for my next stout attempt. Bad thing is I have 10 gallons of this stuff, I'll have to see what it is like after its carbed and conditioned some.

Thanks for your input. If the gravity happens to plummet at all, I'll post an update, but I'm thinking it won't.