Chocolate Stout Fermentation Stuck

[Begbie]

Evening everyone. I'm having a bit of a 'mare tonight. It's bottling day and having never had an issue with stuck fermentations, went ahead and prepared my priming solution, sanitised all my equipment,- 5L mini keg, 30 bottles and bottle caps. As you know, that takes quite a while. Then I took a sample from the FV to confirm what I expected to be an FG of 1012 to 1014.......feck, feck, feck, it's 1026. Feck.

Has anyone else had stuck fermentations with CML Four?

So, I've racked it off the lees and cacao nibs, into a secondary FV and plan to leave it a few days in the hope that maybe it's kicked into life again, and check the gravity again in a few days.

FYI - OG was 1046. Batch size was 19L in the FV. Done this recipe before but a scaled down 10L batch, using S-04 without a problem.

PS - Will a bit of tinfoil over each bottle be OK for a few days so that I don't need to do the whole sanitisation palaver again? I've sanitised and screwed the lid on to the mini keg.

 

[RichardM]

The lesson to learn is to check the gravity two days in a row. If it is near the expected and the same both days you can bottle your brew.
You can't choose bottling day, prepare everything then hope the brew is ready.

What temperature is it? May be warming it up a bit will help How long has it been fermenting?

 

[Clint]

Recipe?

 

[Begbie]

Recipe was basically double the recipe in the link below.

https://www.thehomebrewforum.co.uk/threads/secret-santa-recipes-2021.97336/post-1103750
It's been fermenting for two weeks now. My iSpindel (which does need to be calibrated) has been showing a constant gravity for about 8 days. Knowing that the iSpindel needs calibrated, I don't use it to check the gravity reading, but for checking temperature and that gravity has stabilised.

Lesson learned - I'll check the gravity before spending ages sanitising everything!

 

[foxy]

Evening everyone. I'm having a bit of a 'mare tonight. It's bottling day and having never had an issue with stuck fermentations, went ahead and prepared my priming solution, sanitised all my equipment,- 5L mini keg, 30 bottles and bottle caps. As you know, that takes quite a while. Then I took a sample from the FV to confirm what I expected to be an FG of 1012 to 1014.......feck, feck, feck, it's 1026. Feck.

Has anyone else had stuck fermentations with CML Four?

So, I've racked it off the lees and cacao nibs, into a secondary FV and plan to leave it a few days in the hope that maybe it's kicked into life again, and check the gravity again in a few days.

FYI - OG was 1046. Batch size was 19L in the FV. Done this recipe before but a scaled down 10L batch, using S-04 without a problem.

PS - Will a bit of tinfoil over each bottle be OK for a few days so that I don't need to do the whole sanitisation palaver again? I've sanitised and screwed the lid on to the mini keg.

Did you de-gas the sample?

 

[GeorgieV]

I had a similar experience with a choc stout recently. Although it was fermenting with S-04 originally. I had to re-pitch a different yeast (US-05) to get it going again.

 

[Begbie]

Did you de-gas the sample?

I didn't actually, other than spun the hydrometer a few times. Never have properly de-gassed.

The 2FV is now sealed up with a clean airlock and wrapped in an old jumper to help heat it up a bit. The fermentation temp throughout the 2 weeks was between 19 and 22 decC, so within the recommended range. I was actually chuffed that I managed to maintain quite a steady temperature, seeing as I have no temp control. It's just sat in my spare room.

I'll take a reading on Sunday and see if it's fermented more. Fingers crossed!

 

[Begbie]

Update - 4 days of the FV wrapped up in a jumper reduced the SG by about 1 point. So I threw in some Wilko Gervin Ale yeast that I had for another brew. I also decided to add some heat by sitting the FV on a heat pad, which after a further 11 days, has reduced the SG to 1.016, which is only 2 points away from where I wanted it to be. I think I'll leave it another week and see if it reduces any further.

I just hope that I haven't introduced some off flavours by fermenting the Ale yeast at the higher temperatures the heat pad has introduced. Going by the strip thermometer on the FV, it was at 28-30degC. A sip from the sample cylinder doesn't seem to suggest so.

Looking at my recipe in Brewers Friend again seems to point to a reason for the stuck fermentation, but I'm no expert. The Diastatic Power is only 32, where the software says minimum 30+. Could that be my failing? Should I be looking at a way to increase the DP in future brews of this?

 

[DavidDetroit]

I know this is after the fact regarding the bottles but plastic wrap laid across the lined up bottles is cheaper and is effective.

 

[foxy]

I couldn't read your grain, bill but I would be guessing with it being a stout and counting 8 additions to your base malt that you have a lot of un-fermentable sugars in your grain bill. The mash temperatures will also need to be looked at to get the best result from the base malt. The DP of the base malt is going to do nothing if those 8 additions are all speciality grains. If you have a flaked adjunct among the 8 then the DP will come in to play and convert the starch as long as it isn't to much.

 

[MartinF]

Sticking at 1016, I'd say it's done. I just kegged my stout at 1020, where it had "rested" for about 7 days. Dark beers don't ferment out anywhere near the calculated attenuation of most brewing software.

 

[matt76]

Apologies @Begbie , I didn't see your OP when you first posted it, otherwise I could have saved you a lot of aggro...

I would be guessing with it being a stout and counting 8 additions to your base malt that you have a lot of un-fermentable sugars in your grain bill.

Yup, foxy has hit the nail on the head there.....

Your fermentation was not stuck - it was done! You haven't done anything wrong at all - your problem was not a stuck fermentation, but rather your problem was Brewer's Friend gives completely unrealistic expectations for the FG of dark beers. Or more specifically, it massively overestimates the fermentability of dark grains

I've made this point many times before on this forum, take a look at this post for example. If you want to know how to work around it in Brewer's Friend in future take a look at this post

As I've said in one of those posts, I've brewed the same Porter and Stout many times with strains I've also used in pale beers that don't give me any problems with attenuation - the behaviour is predictable and repeatable.

(One of these days I will get round to trying some other brewing software to see if they do the same thing as BF or if they actually give a sensible prediction for FG of dark beers.....)

 

[Begbie]

Thanks for all your replies and advice - much appreciated.

Something to look into for my next Stout brew @matt76

I'll check the FG of my brew tomorrow night to see where it's at now. If it's still 1016, it's getting bottled. Infact, it's getting bottled anyway, as I doubt it'll go much lower, based on what you've all told me.

Cheers!

 

[matt76]

Exactly - some yeasts will attenuate a bit more than others.

All your Gervin is doing is eating up the modest amount of remaining sugars that the original CML Four couldn't ferment.

 

[Begbie]

Ok, so the SG tonight was 1018, which is higher than the previous reading of 1016. However, a temperature correction for the hydrometer confirmed that 1018 is correct (previous reading was at about 28 degrees). So the ABV works out at about 3.7%. Oh well, I'll call it a Chocolate Oatmeal Session Stout!

14x500ml bottles, 13x330ml bottles, 1x200ml bottle and a 5L mini keg. Looking forward to trying this in a few weeks time.

Thanks again for everyone's help and advice - much appreciated.

 

[Sadfield]

Your fermentation was not stuck - it was done! You haven't done anything wrong at all - your problem was not a stuck fermentation, but rather your problem was Brewer's Friend gives completely unrealistic expectations for the FG of dark beers. Or more specifically, it massively overestimates the fermentability of dark grains

Really? 1.046 to 1.026 is only 43% attenuation from a yeast that typically should give 72-75% for standard mash conditions. Brewers friends prediction of 1.014 (69%) looks pretty reasonable. Given that a repitch of yeast shifted it another 8 gravity points confirms that it wasn't done, it was stuck.

 

[matt76]

Really? 1.046 to 1.026 is only 43% attenuation from a yeast that typically should give 72-75% for standard mash conditions. Brewers friends prediction of 1.014 (69%) looks pretty reasonable. Given that a repitch of yeast shifted it another 8 gravity points confirms that it wasn't done, it was stuck.

Ok, that's a fair enough point. I think the answer might be somewhere in the middle...

On the one hand perhaps the original fermentation want quite done, maybe a couple of points short of the terminal gravity.

But wouldn't you also agree that by pitching a different strain to the original one, a strain that is noted as a high attenuator, that the second yeast can now consume more of the sugars that the first one couldn't?

Brewers friends prediction of 1.014 (69%) looks pretty reasonable.

Sorry mate, but on this point I have to disagree with you - the predictions of FG from BF for dark beers are total bobbins (and FWIW I had a play last night with Brewfather which was equally carp).

Consistently, repeatably and predictably I get <60% AA in my dark beers using strains that in my pale beers give me 75% AA or more.

I mash everything at 67degC and use a consistent process, so it's not process related.

It seems reasonable to me that dark malts are produced such that anything fermentable that was there at the start of the process isn't there by the end of roasting/kilning. My argument is they certainly contribute to OG, but contain little or nothing fermentable, which the calculators seem to ignore.

 

[Sadfield]

Consistently, repeatably and predictably I get <60% AA in my dark beers using strains that in my pale beers give me 75% AA or more.

I think we'll have to disagree. Sure, software isn't perfect and reduced attenuation between dark and pale grists is to be expected, but <60% AA is indicative of other issues in my experience.

 

[matt76]

I think we'll have to disagree.

Agreed

<60% AA is indicative of other issues in my experience.

If you ever fancy popping down to Berkshire and joining me on a brewday (seriously!) I would love to know your thoughts about why it goes pear shaped every time I open a bag of dark malt, because something must be going wrong in an otherwise unchanged process

Sure, software isn't perfect and reduced attenuation between dark and pale grists is to be expected

I see your point but if you wouldn't mind indulging me a moment longer.....

As a little experiment I created a test recipe in BF (actually the grist for my Black IPA which I've made a few times) - if any regular Beersmith or Brewfather users fancy trying calculating the same test recipe with your standard settings then I'd be interested to know what you find). I left it at the standard settings for my setup for my usual 11-12L ish brews, and I didn't choose a yeast so it defaults to 75% AA.
8 parts Maris Otter (e.g. 2000g)
1 part Munich (250g)
1 part Carared (250g)
1 part Chocolate malt (250g)

It gives me an OG/FG of 1.053/1.013. Hmm... OK, so far so good...

Now here's the fun bit, swap the Chocolate malt for a pale malt - I tried Vienna first and the Lager malt. Both gave me OG/FG of 1.053/1.013, i.e. the same as with the dark malt.

So here's the question - with all your experience are you (or anyone else) seriously going to tell me that chocolate malt is just as fermentable as a pale malt? Come off it, pull the other one.....

FWIW, I note that you absolutely didn't suggest that, but rather your point was:

software isn't perfect and reduced attenuation between dark and pale grists is to be expected

Which by the way I agree with, I think you are correct on both points. But what's the point of the software (especially for less experienced brewers) if it tells you total nonsense like this?

It's not so much that the software isn't perfect, it's that it's so far from perfect as to be misleading. I think it's reasonable to expect that the software should at least make some attempt to estimate the reduced attenuation you get from different malts but as far as I can see they make zero effort towards this. Which is irksome

(As I said above, if anyone wants to know how I work around it in Brewer's Friend then take a look at this post )

And if you're still not convinced then yeah, we can agree to disagree - and I should probably direct my frustration towards the evil brewing software mega-corporations () than forum members

 

[Sadfield]

Using the above example, and from previous posts, you say you'd consistently get or expect <60% AA if it had Chocolate Malt in it versus Pale malt. That's a +20% drop in attenuation from changing 9% of the grist. An FG of 1.021 vs 1.013. A difference of 8 (15%) of the initial 53 gravity points. Looking from the outside, to me, that suggests that your yeast is giving up early. It might be worthwhile looking a wort aeration, pitch rate and nutrient additions. I'd be expecting it finish lower than 1.021, regardless of what any software predicted.