Over attenuation

[ph0ngwh0ng]

Hi!

I seem to be getting constant over attenuation. My thermometer is calibrated. I single infusion mash with a double batch sparge that raises the grain bed to 170F. I use BeerSmith for all my calculations.

I'm pretty disappointed since the last batch was a spotless one, where I hit all my numbers and volume.

Here is the recipe:

Recipe: Unexpected Black IPA
Style: English IPA
TYPE: All Grain

Recipe Specifications
--------------------------
Boil Size: 7,48 gal
Post Boil Volume: 5,98 gal
Batch Size (fermenter): 5,00 gal
Bottling Volume: 4,60 gal
Estimated OG: 1,073 SG
Estimated Color: 32,3 SRM
Estimated IBU: 60,9 IBUs
Brewhouse Efficiency: 72,00 %
Est Mash Efficiency: 82,8 %
Boil Time: 90 Minutes

Ingredients:
------------
Amt Name Type # %/IBU
12 lbs Pale Malt (2 Row) US (2,0 SRM) Grain 1 83,6 %
1 lbs Caramel/Crystal Malt - 60L (60,0 SRM) Grain 2 7,0 %
8,0 oz Black (Patent) Malt (500,0 SRM) Grain 3 3,5 %
8,0 oz Chocolate Malt (350,0 SRM) Grain 4 3,5 %
5,6 oz Carafoam (2,0 SRM) Grain 5 2,4 %
0,75 oz Nugget [13,50 %] - Boil 60,0 min Hop 6 31,5 IBUs
0,50 oz Nugget [13,50 %] - Boil 40,0 min Hop 7 18,4 IBUs
0,50 oz Willamette [4,70 %] - Boil 25,0 min Hop 8 5,1 IBUs
0,50 oz Willamette [4,70 %] - Boil 15,0 min Hop 9 3,6 IBUs
0,75 oz Willamette [4,70 %] - Boil 5,0 min Hop 10 2,2 IBUs
1,0 pkg Nottingham Yeast (Lallemand #-) [23,66 m Yeast 11 -


Mash Schedule: Single Infusion, Medium Body, Batch Sparge
Total Grain Weight: 14 lbs 5,6 oz
----------------------------
Name Description Step Temperat Step Time
Mash In Add 21,53 qt of water at 161,7 F 152,0 F 60 min

Sparge: Batch sparge with 3 steps (Drain mash tun, , 2,04gal, 2,04gal) of 185,0 F water

Dry Hop: 1 oz Willamette

 

[Hammy71]

Your mashing process is the first suspect I would look at. How well does your mash tun hold temperature? Even though you may stick the thermometer in the top and say "I'm good", the bottom of the tun may be as much as 10 degrees off (especially after a 60 minute mash). The difference of a few degrees will have effects on your FG. Just some food for thought.

 

[Yooper]

When you say overattenuated, how much do you mean? I can't see an actual mash temperature or FG on that recipe, and we need to know those figures.

 

[BackAlley]

When you say overattenuated, how much do you mean? I can't see an actual mash temperature or FG on that recipe, and we need to know those figures.

I think it says 152 at the bottom of the recipe.

 

[pondochris]

I think it says 152 at the bottom of the recipe.

But there's still no FG listed. Not even estimated/predicted/desired FG.

 

[ph0ngwh0ng]

Actual mash temp was 153F on mash in, 152F after 60 min. My mash tun is a rectangular cooler, and the grain bed was about 8 inches deep. My thermometer's probe is 4 inches. So maybe the bottom of the grain bed was colder, but I would tend to rule that out, since the bottom of the cooler wasn't hot, so insulation on the bottom seems to be good. But, I'll try to get my hands on a longer probe.

Expected FG was 1.016, I got 1.010 after 2 weeks in primary.

 

[Yooper]

Actual mash temp was 153F on mash in, 152F after 60 min. My mash tun is a rectangular cooler, and the grain bed was about 8 inches deep. My thermometer's probe is 4 inches. So maybe the bottom of the grain bed was colder, but I would tend to rule that out, since the bottom of the cooler wasn't hot, so insulation on the bottom seems to be good. But, I'll try to get my hands on a longer probe.

Expected FG was 1.016, I got 1.010 after 2 weeks in primary.

It's your expected FG that's wrong!

1.010 is a perfectly fine FG for a beer that was mashed at 152/153 with those ingredients (including yeast strain). Nottingham's expected attenuation is often 85% or so- and yours is 86% from my quick guestimate. That's not overattenuation at all, and should be an expected FG for most beers mashed at that temp.

 

[ph0ngwh0ng]

It's your expected FG that's wrong!

1.010 is a perfectly fine FG for a beer that was mashed at 152/153 with those ingredients (including yeast strain). Nottingham's expected attenuation is often 85% or so- and yours is 86% from my quick guestimate. That's not overattenuation at all, and should be an expected FG for most beers mashed at that temp.

Wow, thank you BeerSmith!

How do I know in advance what attenuation to expect, since Beersmith is obviously flawed on that subject? Danstar's website does say this:

High attenuation, reaching a final gravity near 1008 (2°P).

Does a given yeast strain always attenuate towards a given FG, whatever the OG is?

 

[Yooper]

Wow, thank you BeerSmith!

How do I know in advance what attenuation to expect, since Beersmith is obviously flawed on that subject? Danstar's website does say this:



Does a given yeast strain always attenuate towards a given FG, whatever the OG is?

That's a flaw in all calculators, but Beersmith is better now in the newer versions. It used to give you a solid 75% attenuation for a projected FG, no matter the yeast strain or ingredients.

It's one of those things that calculators just have to be limited in, as mash temperature, yeast strain, ingredients, etc, all play a part in apparent attenuation.

For example, if you take:
10 pounds pale malt
2 pounds of corn sugar
and mash it at 147, you probably have an OG of 1.073 and a FG of 1.006 or so.

Using the same yeast strain, and this grainbill:
10 pounds pale malt
2 pounds crystal malt
1.5 pounds Munich malt
mash at 158

You'd have an OG of 1.073 also- but a FG of 1.020-1.026.

Mash temperatures and fermentability of ingredients play a huge part, as does the yeast strain chosen.

When making recipes, Beersmith can be helpful in projecting the FG to an extent but normally it's not all that accurate.

If you feel the beer is too dry, you can make a note of it and mash at a higher temperature in the future for your system to give you the results you want.

 

[ph0ngwh0ng]

Thanks a lot! That was very helpful!

 

[coyote68]

thanks yopper, this helps with some recent problems of too dry beers.
sets me off in the right direction.

 

[ballsy]

Off subject, but impressed that single pitched Notty did the job on a 1.07 + OG beer!! I usually double pitch anything over 1.06.

 

[ph0ngwh0ng]

Off subject, but impressed that single pitched Notty did the job on a 1.07 + OG beer!! I usually double pitch anything over 1.06.

Actually, I used half the washed yeast from a previous batch. I didn't make a starter, since I thought and calculated it was plenty, but fermentation took forever to start (~48 hrs).

 

[broadbill]

After having an Oktoberfest overattenuate, I have begun doing a mash-out to "set" the sugar profile before sparging. I found the although the sparge water would eventually get the mash bed to mash-out temps, that left significant time for the wort fermentibility to increase in the time I had the runnings draining, sitting in the kettle, etc..

What I've done:
Decrease mash time: I'm getting conversion in 30minutes...
Decrase batch sparge time....I increased the ID of my mash tun tubing/plumbing.
Increase mash temp.
Start heating running as soon as I collect them.
Started doing a mash-out before I start the sparge.

I hope this helps!

 

[coyote68]

tomorrow i'm re-brewing a bitter that i expected to finish @1.010 but ended @1.004 (real dry) i usually mash at 152@60MIN. i'm gonna try mashing @160for 30min. check conversion with iodine test mash out @ 170 for 10 min. to see if this helps.

 

[rklinck]

tomorrow i'm re-brewing a bitter that i expected to finish @1.010 but ended @1.004 (real dry) i usually mash at 152@60MIN. i'm gonna try mashing @160for 30min. check conversion with iodine test mash out @ 170 for 10 min. to see if this helps.

160 is really high, and I would bet you will under attenuate. This is above the temp that beta is denatured. I would try going up in temp less than 8 degrees.

 

[phuff7129]

After having an Oktoberfest overattenuate, I have begun doing a mash-out to "set" the sugar profile before sparging. I found the although the sparge water would eventually get the mash bed to mash-out temps, that left significant time for the wort fermentibility to increase in the time I had the runnings draining, sitting in the kettle, etc.. What I've done: Decrease mash time: I'm getting conversion in 30minutes... Decrase batch sparge time....I increased the ID of my mash tun tubing/plumbing. Increase mash temp. Start heating running as soon as I collect them. Started doing a mash-out before I start the sparge. I hope this helps!

This could be part of the issue as well. If you leave your first runnings sit around while you are batch sparging they are still converting at lower temps giving you a highly fermentable wort. I don't mash out, I just get my first runnings on the burner immediately to stop conversion while I batch sparge.

 

[ph0ngwh0ng]

Wow, this thread is so instructive for me. All grain is so complex!

I'm definitely changing my process so that the first runnings are heated and the ~185F batch sparge water is added to the grist ASAP to stop conversion. Also thinking about including the time it takes to drain the mash tun into the kettle in the mash time. No need to mash out then, the sparge water will do the trick.

However, I think that sticking to the recipe for mash times and temps is quintessential to achieving the desired results. It'll definitely help me in designing better recipes, although. Choosing the right yeast and grain also. I think that Notty wasn't the right choice here, since I wasn't shooting for a dry beer. Should've gone with Wyeast Scottish. Also, I'll cut back on the 2row and maybe add some Munich or Victory to the bill. Oh well, I guess I'll have to brew that one again, bummer

 

[coyote68]

Re-brewed the bitter this morning. mashed @ 154 F. I cheched the calibration of my thermometer, it was way off. dug out the old glass lab one checked the mash tun temps and was holding 154 throughout. also mashed out @ 172 F. and started heating the runnings right away.
OG was 1.048 @ 68 F, pitched with west yorkshire yeast.
i'll see if this takes care of my problems as i suspect it will.
thanks to all for the insight, although i should have known better than to trust my thermometer.
great lesson learned.