Two Dunkelweizens, both stuck fermentation

[Dulwich North]

Is there an obvious reason why two Dunkelweizen fermentations might stop early, at 1.022 in one case and now 1.027 in another?

The respective OGs were 1.056 and 1.060, and in each case the fermentation appeared to bubble away normally for a couple of days, but hadn't progressed fully when I checked gravity on days 7 and 14. Temperature has been in the 22-25C range. I tried adding more yeast to the first one, but FG only went to 1.022.

While I bottled the first one in February, the bottles haven't improved with age - too thick, too sweet - and I don't know why I don't just pour the rest away. I'm not sure it's even worth bottling the current one and am not sure it could be rescued. Are Dunkelweizens particularly prone to this problem? Or should I just go back to the GH book recipe which turned out perfect last year?

This was the grain used for both failed efforts:
43% German - Dark Wheat
16% Munich Dark 20L
25% German - Bohemian Pilsner
5% German - CaraMunich I
5% Belgian - Special B
5% United Kingdom - Chocolate

 

[HarryFlatters]

What kind of yeast are you using? I've just kegged a very similar beer to your recipe above, fermented with CML Gretel yeast and it got down to 1.010.

I fermented mines under pressure in a Fermzilla Allrounder at about 22C, not sure if that makes a difference.

 

[Tess Tickle's Brewery]

Perhaps there wasn't enough base malt to fully convert all the grains? Just a thought.

 

[Dulwich North]

What kind of yeast are you using? I've just kegged a very similar beer to your recipe above, fermented with CML Gretel yeast and it got down to 1.010.
I fermented mines under pressure in a Fermzilla Allrounder at about 22C, not sure if that makes a difference.

Sorry, I should have added it was Lallemand Munich Classic German Wheat-Style Yeast. It's the same as I used last year when I did the GH Dunkelweizen which was successfully bottled at 1.012.

Fermenting was in a 10L plastic fermentation bucket which I've used 20+ times over the last year. But the only time I've had this problem has been with this Dunkelweizen.

 

[HarryFlatters]

Perhaps there wasn't enough base malt to fully convert all the grains? Just a thought.

I've plugged the recipe into Brewer's Friend and the diastatic power is 38, which is kinda low so you could be onto something.

I'm sure that you can buy enzymes that you can add to the fermenter to break down starches into simpler sugars that your yeast can munch through. I haven't used these before but I'm sure that someone that has experience will come along soon.

 

[thegrantickle]

I've plugged the recipe into Brewer's Friend and the diastatic power is 38, which is kinda low so you could be onto something.

I'm sure that you can buy enzymes that you can add to the fermenter to break down starches into simpler sugars that your yeast can munch through. I haven't used these before but I'm sure that someone that has experience will come along soon.

Careful with that, though - you may end up with a VERY dry beer.

 

[MartinF]

What was your mash schedule?

I had a problem with a Dunkelweizen stuck at 1.021 earlier this year, using Mangrove Jack M20 Bavarian Wheat yeast. I added some Safale US-05 to try to ferment it out further, but to no avail.

I just repeated the same recipe but used Safale wheat yeast WB-06 + 2g CML yeast nutrient and it went down to 1.010, which may be a little too dry. But my recipe is very different to yours ( for 22L into FV)...

50% Weyermann wheat malt
22% Crisp Europils
20% Weyermann Vienna
4.5% Weyermann Caraaroma
2.5% Crisp Roast Barley

Mash schedule...
Mash-in/protein rest — 55 °C — 10 min
Maltose rest — 63 °C — 35 min
Saccharification rest — 72 °C — 30 min
Mashout — 75 °C — 8 min

I know I changed too many variables between the two batches to be able to pin down the reason for improvement, but I suspect the yeast type + nutrients may be the main reason.

Also, with this latest batch, it was so hot in the garage (aka fermenting hall!) during this last hot spell, the fermenting temp was going between 20° & 23°. My previous batch was fairly well pinned to 20°.

Not sure that helps but there may be something in there to chew over.