[yso191]

I brewed a chocolate Imperial stout a week and a half ago.  OG was 1.095.  I used Denny's Favorite (#1450).  I have never before used chocolate.  I broke up a 4-Ounce Ghirardelli Chocolate Baking Bar (100% Cacao Unsweetened Chocolate) and put it in the boil with 10 minutes to go.

I have done this recipe before (sans chocolate).  Like last time I fermented at 64* for a week then ramped up to 70*.  Airlock activity stopped long ago. 

I just too a gravity reading.  It is at 1.040  The last time I did this recipe the FG was 1.019, but I also let it sit at 70* for 3 weeks before testing the gravity.

My questions:
Did the chocolate add unfermentable sugars?
Maybe it is just not done fermenting - I have never had a stalled fermentation, so I haven't studied it.  Do you think I have one, and if so, what is to be done?

[pete b]

I brewed a chocolate Imperial stout a week and a half ago.  OG was 1.095.  I used Denny's Favorite (#1450).  I have never before used chocolate.  I broke up a 4-Ounce Ghirardelli Chocolate Baking Bar (100% Cacao Unsweetened Chocolate) and put it in the boil with 10 minutes to go.

I have done this recipe before (sans chocolate).  Like last time I fermented at 64* for a week then ramped up to 70*.  Airlock activity stopped long ago. 

I just too a gravity reading.  It is at 1.040  The last time I did this recipe the FG was 1.019, but I also let it sit at 70* for 3 weeks before testing the gravity.

My questions:
Did the chocolate add unfermentable sugars?
Maybe it is just not done fermenting - I have never had a stalled fermentation, so I haven't studied it.  Do you think I have one, and if so, what is to be done?

Pretty sure there are no unfermentable sugars in unsweetened chocolate and it's a pretty small amount. I didn't catch fermentation temperature but it seems like a time to rouse and warm. Did you use a starter? If warming and rousing doesn't do it you could be stuck but I wouldn't give up yet, a beer with that gravity can take awhile.

[yso191]

I'll shake the fermenter a bit and bump the temp to 73*

[Joe Sr.]

I use baking bars fairly regularly. They ferment out just fine and don't lead to a higher fg IME.


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[blair.streit]

I've had airlocks fool me because the CO2 was leaking out from around the stopper or another seal. If gravity is steady then you'll know for sure.

Raising temp at this point seems like it probably wouldn't hurt.

If you want to go full panic mode you could get a well-aerated starter going at full krausen and then dump the whole thing in there. At 1.040 it seems like there's still plenty for it to chew on.

How much yeast did you pitch originally and was it the same as when you brewed this before?

[yso191]

How much yeast did you pitch originally and was it the same as when you brewed this before?

I made a starter.  According to the calculator about 400 billion cells.  Yes, same as last time.  In fact the only thing different is the chocolate bar - at least that I know of.

The good news is that I sampled it and it tastes good!

[blair.streit]

Seems like plenty of yeast. I'd give it a couple more days and take another gravity. Then you'll know if the yeast has given up or if it's just taking its time.

[yso191]

Well it is my first officially stuck fermentation.  after 3 weeks it still measures 1.040.  It still tastes good so I'm going to keg it and force carbonate it then bottle it. 

Sure wish I knew what prompted it to go to sleep...

[blair.streit]

Well it is my first officially stuck fermentation.  after 3 weeks it still measures 1.040.  It still tastes good so I'm going to keg it and force carbonate it then bottle it. 

Sure wish I knew what prompted it to go to sleep...

Was your starter/oxygenation routine the same? It sounds like you had plenty of cells, so I'd guess something made them unhappy. Usually that's either poor health to begin with, or something like osmotic or temperature shock.

At 1.040 and ~4% ABV it seems like you could still hit this with some yeast at high krausen. There should be plenty for them to eat if they can ease their way in.

Also, do you trust the hydrometer?

[yso191]

According to Beersmith, 1.095 to 1.040 is 7.3%, which is a little low for an imperial, but OK for me as long as it tastes good.  IBU's are calculate at 67, so it should hold up to all the residual sweetness, especially with the roastiness.

Yes my procedures were the same, but even if it was underpitched for some reason, I'd think the yeast would just keep chewing, albeit stressed, rather than stop.

As to the hydrometer, yes it is my most consistent & accurate one (out of 4).

[blair.streit]

According to Beersmith, 1.095 to 1.040 is 7.3%, which is a little low for an imperial, but OK for me as long as it tastes good.  IBU's are calculate at 67, so it should hold up to all the residual sweetness, especially with the roastiness.

Yes my procedures were the same, but even if it was underpitched for some reason, I'd think the yeast would just keep chewing, albeit stressed, rather than stop.

As to the hydrometer, yes it is my most consistent & accurate one (out of 4).

That all sounds right to me. Sorry, I was running to a meeting and just threw out an ABV without thinking. On a beer that big hitting 75% of your attenuation target would clearly yield more than 4% ABV.

It does seem that if you slightly underpitched it would just take longer and maybe show some signs of a stressed fermentation. That's why I was headed more towards oxygenation or some kind of shock. The one time I had something similar, I attributed it to poor oxygenation on a repitch, but I was never really sure.

[yso191]

Yeah every usual cause of a stalled fermentation doesn't seem to be the case.  Just proves I have more to learn or establish in my process.  I don't always oxygenate anymore, but I always do on big beers like this one.  A full minute of pure O2  out of a diffusion stone at the bottom of the conical.

The only thing I can think of is that the yeast didn't have much of a head in the starter.  However the airlock activity started very quickly and kept going strong for 3+ days.

Weird, just weird.

[Saccharomyces]

Did you check the pH?  Many yeast strains will stall if the pH drops too low. 

[yso191]

I did not.  I'm brewing an IPA and kegging that beer tomorrow.  If I remember I will check the pH.  Thanks Mark.

[denny]

Did you check the pH?  Many yeast strains will stall if the pH drops too low.

It would have to hella low.