Did this [decoction] mash profile result in lots of unfermentable sugars?

[funnycreature]

This is the third time I brewed a Kölsch (own recipe) using a double decoction. The first two times were successful but a bit dry and bitter so I tried to modify the recipe and temps to yield a somewhat sweeter beer. Here's the Beersmith recipe (ignore the mash part since it never works for me when doing decoctions; look in the notes for the actual mash data):

BeerSmith 2 Recipe Printout - http://www.beersmith.com
Recipe: Heimat Kölsch (Gute Ryese)
Brewer: Sven
Asst Brewer:
Style: Kölsch
TYPE: All Grain
Taste: (30.0)

Recipe Specifications
--------------------------
Boil Size: 7.83 gal
Post Boil Volume: 7.02 gal
Batch Size (fermenter): 6.00 gal
Bottling Volume: 5.60 gal
Estimated OG: 12.41 Plato
Estimated Color: 5.1 SRM
Estimated IBU: 27.1 IBUs
Brewhouse Efficiency: 72.00 %
Est Mash Efficiency: 81.0 %
Boil Time: 90 Minutes

Ingredients:
------------
Amt Name Type # %/IBU
6 lbs Kolsch malt (4.5 SRM) Grain 1 51.0 %
3 lbs Pilsner (2 Row) Ger (2.0 SRM) Grain 2 25.5 %
2 lbs White Wheat Malt (2.4 SRM) Grain 3 17.0 %
8.0 oz Rye Malt (4.7 SRM) Grain 4 4.3 %
4.1 oz Acid Malt (3.0 SRM) Grain 5 2.2 %
1.50 oz Hallertauer [4.30 %] - Boil 60.0 min Hop 6 19.2 IBUs
0.50 tsp Yeast Nutrient (Boil 15.0 mins) Other 7 -
1.00 tsp Irish Moss (Boil 10.0 mins) Fining 8 -
0.50 oz Tettnang [8.00 %] - Boil 5.0 min Hop 9 2.4 IBUs
0.50 oz Hallertauer [4.30 %] - Steep/Whirlpool Hop 10 1.9 IBUs
0.50 oz Tettnang [8.00 %] - Steep/Whirlpool 20. Hop 11 3.6 IBUs
1.0 pkg German Ale/Kolsch (slurry) (White Labs # Yeast 12 -


Mash Schedule: Decoction Mash, Double
Total Grain Weight: 11 lbs 12.1 oz
----------------------------
Name Description Step Temperat Step Time
Acid rest Add 3.77 gal of water at 114.8 F 107.6 F 40 min
Maltose rest Add 3.24 gal of water at 195.2 F 144.0 F 90 min
Dextrinization Decoct 2.17 gal of mash and boil it 162.0 F 30 min
Mash Out Decoct 1.31 gal of mash and boil it 170.0 F 20 min

Sparge: Batch sparge with 2 steps (Drain mash tun , 2.48gal) of 180.0 F water
Notes:
------
Water (from RO water): added 3.22 g CaCl2 to 7 gal of mash water
added 1.15 g CaCl2 to 2.5 gal of sparge water


Was shooting for acid rest at 100F but landed at 112. Added ~1 liter of ice cubes to get to ~100-102 F. Mash pH between 5.0 and 5.5. Added 3.3 gal of 205 F water to reach 139.5 F. Will let it go and take first decoction after 30 min. Raised temp of decoction to 158-160 for 15 min. Then boil. This step resulted temp of 151.9 F. Let rest for 30 min.

Second decoction was boiled for 10 min and rose temp up to 162.9 F. Letting it settle briefly and then start Vorlauf.

Set fermentation temp to 18 C.

I used a slurry of WLP029 yeast from an Imperial Porter that I allowed to "recover" overnight in a 1.040 starter on a stir plate and cold-crashed the next day. [It is entirely possible that the yeast was exhausted still]. I "oxygenated" as always using the Venturi method.
Fermentation started off OK and gravity went down from 12.0 °B(maybe 12.5) to 9.0 °B after 5 days. After another 4 days it was down to barely below 8.0 °B and has remained there since. I added a half-pack of US-05 because I was afraid that the [WLP029] yeast was just not happy but after 24 h the gravity was still unchanged. My goal is to bring it down to at least 6.5 °B (1.012).

My question is now: What caused the stalled fermentation? Was it the yeast being exhausted or perhaps the mash profile? I've never had any issues before even with 8+% ABV beers.

 

[funnycreature]

Update: Even after almost 72 hours after adding more yeast it's still at 7.5 B... Not sure if I want to ride this one out or simply dump it and start fresh.

 

[rmyurick]

Probably a dumb question, but you're using a hydrometer, right? (refractometer won't read correctly with alcohol present). Also, did you iodine test for conversion?

 

[funnycreature]

Probably a dumb question, but you're using a hydrometer, right? (refractometer won't read correctly with alcohol present). Also, did you iodine test for conversion?

That is a very valid question! No, I am using the refractometer and get the adjusted gravity from this website: www.onebeer.net/refractometer.shtml
Beersmith has a similar tool but I don't trust it as much.

As for the iodine test for conversion, I did it a few times prior but it was nothing worth repeating in my opinion. In this particular case I actually have almost the opposite problem - too much sugar that doesn't want to convert.

 

[rmyurick]

My opinion is that those equations don't really work worth a damn. I would cheek it with a hydrometer or taste it.

 

[funnycreature]

My opinion is that those equations don't really work worth a damn. I would cheek it with a hydrometer or taste it.

I will definitely check with a hydrometer although I can tell by the taste that it's still a bit too sweet... So far the equations worked fine for me.

 

[Yooper]

I will definitely check with a hydrometer although I can tell by the taste that it's still a bit too sweet... So far the equations worked fine for me.

The equations never worked for me, but I did hear that Sean Terrel's is the best of the bunch although not accurate for me.

How big (percentage of the grainbill) was held at 158 during the decoction? That certainly would create a lot of unfermentables. Next time, hold the decoction at the desired saccrification rest, and not so high, before boiling and adding back to the mash. If, say, 30% of your grain was held at 158, that would explain the high FG.

 

[funnycreature]

The equations never worked for me, but I did hear that Sean Terrel's is the best of the bunch although not accurate for me.

How big (percentage of the grainbill) was held at 158 during the decoction? That certainly would create a lot of unfermentables. Next time, hold the decoction at the desired saccrification rest, and not so high, before boiling and adding back to the mash. If, say, 30% of your grain was held at 158, that would explain the high FG.

I must have taken a lot of grain, definitely more than 50%, because otherwise I never hit my temps afterwards. I could also try what Kai did once for his DIPA and add some enzymatically active wort to the beer to convert some more sugars (http://braukaiser.com/blog/blog/2013/02/02/kaipa2/).

 

[rmyurick]

Didn't know about the Sean Terrill calc. Will have to check that out on one or more of my existing brews. (another excuse to drink, as if I needed that!)

 

[funnycreature]

Took a hydrometer reading last night and it was 1.009(ish) while the refractometer showed ~7.0. This means the calculator I linked to was off by 0.004. Since 1.009 is even lower than my expectations I put the fermentor in the fridge for cold crashing. That baby needs to be vacated for next brewday this weekend!