Stuck Ferment on an Imperial Stout

[Ollie_44]

[SIZE=10.5pt]Hi all, I'm brewing my first all grain imperial stout and I think I've got a stuck fermentation. I hit my target OG of 1070 but I cannot seem to reach my FG target of 1020 and its been in the fermenter soon to be 4 weeks!. It’s been a constant 1030 from the end of the 3rd week and it hasn't budged despite taking it out of the fridge so it gets a bit warmer during the day, and giving it a gentle shake to get some more yeast in solution. Been fermenting between 15-17 degrees in the fridge and now out of the fridge it would be in the range of 12-20 degrees. Do I just bottle it, or keep it in the fermenter and risk autolysis. Also, would i need to re pitch yeast to bottle given the lack of activity. If anyone has some advice that would be awesome. .[/SIZE]

[SIZE=10.5pt]cheers[/SIZE]

 

[Mardoo]

What yeast did you start with and how much did you pitch?

 

[mje1980]

And was it all malt?

 

[Yob]

That's pretty cool ferment temps, get a big old Sanitised spoon and rouse the cake and keep it about 20'c maybe you can Re activate the sleepy little buggers

At 1.070, technically doesn't fit as a RIS but thats neither here nor there

Vital Statistics: OG: 1.075 - 1.115

 

[Ollie_44]

[SIZE=10.5pt]I pitched one packet of an English Ale liquid yeast (wyeat labs) and it was going off for the first 2 weeks. Bit of a newbie mistake though, in hind sight should have made a starter or pitched two packets. What is the normal pitch rate for higher gravity beers?[/SIZE]

[SIZE=10.5pt]Ok will try and stir the yeast up and raise the temp to liven them up. What is the best way to heat the fermenter in a temp controlled fridge arrangement. Can I just chuck a heating pad/belt in there, or is it better to get a heating lamp. Haven't got around to setting up heating yet beacaus in summer I get away with just the fridge.[/SIZE]

[SIZE=10.5pt]PS/FYI my basic recipe is as follows I’m using all malts [/SIZE]

[SIZE=10.5pt]1kg JWM Chocolate Malt[/SIZE]
[SIZE=10.5pt]1kg JWM Roasted Malt[/SIZE]
[SIZE=10.5pt]4kg Glenfield’s Ale Malt [/SIZE]
[SIZE=10.5pt]0.5k Wheat Malt[/SIZE]

[SIZE=medium]Golding’s 30g at 60min 20min and 5min [/SIZE]

[SIZE=medium]Targets [/SIZE]
[SIZE=medium]OG 1070 and FG 1020[/SIZE]

[SIZE=medium]Cheers[/SIZE]

 

[Liam_snorkel]

Phwoar she's gonna be roasty, yum

 

[mje1980]

A single wyeast pack is not enough, normally for 1070 I'd use half the yeast cake from a mild ale or something. I doubt it'll go much more but they to rouse and bring it up to temp.

 

[fcmcg]

Also importantly , what was your mash temp ?

 

[Ollie_44]

Used a 60min single infusion mash at around 70c in an esky that holds the temp pretty well. Mash out at 75c for a boil volume of about 27L. Batch size ended up being 21L.

Ok seems like I under pitched by a lot. If a ferment gets stuck like this from cold temps and under pitching does it mean I’m going to have a hard time bottle carbonating once it’s all fermented?

 

[Liam_snorkel]

Whoa! You mashed pretty high, I wouldn't expect it to drop any further. Next time aim for mid-60's

 

[Ollie_44]

[SIZE=10.5pt]Errr righto bit hot then hehehe. So on that note, do higher mash temps produce less fermentable sugars and result in higher FG readings? i.e. my problem could be a combination of a mashing issues and a fermentation issue then.[/SIZE]

[SIZE=10.5pt]Ok my current plan of attack will be to shakeup the fermenter, put me new heating belt on it to rise the temp to a constant 20 degrees, leave it settle for a few days to finish any brewing it may have left, and bottle on the weekend. [/SIZE]

[SIZE=10.5pt]PS appreciate the advice here. This is only my 4th brew so I'm sorta making it up as I go along by trial and error. A lot of error at the moment hehehe [/SIZE]

 

[stewy]

Errr righto bit hot then hehehe. So on that note, do higher mash temps produce less fermentable sugars and result in higher FG readings? i.e. my problem could be a combination of a mashing issues and a fermentation issue then.

Ok my current plan of attack will be to shakeup the fermenter, put me new heating belt on it to rise the temp to a constant 20 degrees, leave it settle for a few days to finish any brewing it may have left, and bottle on the weekend.

PS appreciate the advice here. This is only my 4th brew so I'm sorta making it up as I go along by trial and error. A lot of error at the moment hehehe

Yes. Higher mash temp = more long chain sugars which won't ferment. Your recipe still looks tasty. To get it to 1020 next time I would aim for around 67

 

[Liam_snorkel]

Errr righto bit hot then hehehe. So on that note, do higher mash temps produce less fermentable sugars and result in higher FG readings?

generally speaking, yes! And conversion happens quicker. It's also a useful tool to use - say you wanted to make a low alcohol beer that didn't taste watery, you could do a short mash at 72 or so. Or if you want to to a high gravity beer with high attenuation, a long mash at 64 followed by a mashout would get you there (yeast dependant of course)

Have a squiz through this: http://braukaiser.com/wiki/index.php?title=The_Theory_of_Mashing

 

[warra48]

Just to add to the good advice you already have, it is very important to properly aerate your wort when pitching your yeast on a high gravity beer.
You need to give the yeast all the help you can give it. That includes using yeast nutrient also.
Just shaking the fermenter isn't going to do the job with a beer like this.

 

[TheWiggman]

There's a good chance the ferment is done with an OG like that in 21l using a single smack pack. Most of the hard work is done, try rousing as suggested above and if that's doesn't work it would be worth pitching more yeast. If nothing else this would help priming for bottling.

 

[citizensnips]

I'm just taking a stab here but sounds like the beers gonna have its share of Diacetyl. The severe lack in pitching rate and aeration coupled with the English yeast strain could mean you're in for a butterscotch delight. With that said your best bet to remove as much as possible is rousing the yeast and raising to 20 degrees or so, as others have already said.

 

[donald_trub]

I once had a busted thermometer which caused me to mash above 70. I too missed FG by a fair amount. I chucked in some 'dry enzyme' from the LHBS and it dropped the gravity to a more respectable level, on the dry side though. I read comments that said dry enzyme makes a poor tasting beer, but I had the opposite experience - I loved that beer.

 

[Ollie_44]

[SIZE=medium]Roused the yeast cake at the bottom and put the heating belt on it after work yesterday. Temp sitting at a good 20 to 22 degrees. There was little to no activity thus far. But I’ll give it a couple of days before bottling. I think the tracks are laid here to a certain extent for this batch. But got some awesome pointers for the next batch which will be soon cause I’m a stout nut. [/SIZE]

[SIZE=medium]PS had a sample of the flavours I’m getting and it’s not bad (not good either hehehe). Up front I’m getting an olive oil type flavour and mouth feel (Diacetyl?), but fortunately the bitterness and roasty malt flavours balance out the after tastes. I’ll leave it a good amount of time to bottle condition (i.e. 5 or 6 months) and that might settle things out too. But hay, I grew up drinking VB so I pride myself on being able to drink anything. Well as long as it fizzy and beery I’m good hehehe [/SIZE]

 

[Judanero]

:icon_offtopic: Kind of.. it is related.

Has anyone used and able to report on the Danstar cask conditioning yeast?

Could that be added in a circumstance like this (stuck ferment not high mash temps)?

 

[HBHB]

:icon_offtopic: Kind of.. it is related.

Has anyone used and able to report on the Danstar cask conditioning yeast?

Could that be added in a circumstance like this (stuck ferment not high mash temps)?

Yep, works a treat.