Chocolate Stout Fermentation Stuck

[matt76]

Thanks for the suggestions @Sadfield , they're appreciated

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.

Apologies, I should have been more specific. That particular recipe has a relatively small amount of dark malt so the effect isn't so pronounced. Nevertheless, using my method I'd confidently expect to see about FG 1.016 for 69% AA and 4.76% ABV.

Better examples are my Porter and Stout which both have much higher proportions of dark malts, thus the tendency to under attenuate is much more noticeable.

At the last attempt my Porter for example ended up:
OG = 1.057 (Tilt)
FG = 1.023 (Tilt)
Apparent Attenuation = 60%
ABV = 4.5%

And I would add that that was pretty much as predicted according to my method/arguments. I've made it many times with different strains that attenuate a bit more/or less, but the general behaviour is always the same in both the Porter and Stout.

The only uncertainty in that case was I'm still getting a feel for how that particular strain (LVIPA) behaves. The same yeast attenuated much more "normally" in 2 pale beers (a bitter and an AIPA) I also used it in.

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.

Not impossible, but why should that be the case when, and only when, I open a bag of dark malt?

Aeration is the same across all my beers - kettle on the kitchen island with about a 1m drop to the bucket on the floor. The FV always ends up with 5-10cm froth on top whatever the beer so I'm pretty confident aeration isn't an issue.

Pitch rate is the same across all my beers - usually half a pack of dry yeast for ales (5.0 or 5.5g) in 11L or so unless I'm re-pitching.

Nutrient? Ok, not impossible, but like I say I can't see why it should occur only in dark beers when every other aspect of my brewing is unchanged.

For me it's a more parsimonious explanation simply that x-grams of a dark malt simply is not going to contain anywhere near as much fermentable "stuff" as pale malt.

 

[foxy]

Agreed


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


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:

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

I don't mash any of my speciality grains, from light crystal to roast, I first started doing this with just roast but include now anything that doesn't need to be mashed including dextrin malt. I do a 20 minute mash out at 77 C. So I tick the box 'Late Addition' then tick the box 'Mash' Two reasons for doing this it makes the water additions so simple, the only thing I adjust on my water is the pH to go up and down depending on what beer I am making.
Try ticking the late addition box and see what you get.

 

[matt76]

I don't mash any of my speciality grains, from light crystal to roast, I first started doing this with just roast but include now anything that doesn't need to be mashed including dextrin malt. I do a 20 minute mash out at 77 C. So I tick the box 'Late Addition' then tick the box 'Mash' Two reasons for doing this it makes the water additions so simple, the only thing I adjust on my water is the pH to go up and down depending on what beer I am making.
Try ticking the late addition box and see what you get.

Thanks for the tip @foxy , I will take a look into that feature in BF

But we're still left with the issue that to get the right answer you need to know what the answer should be. Which I can't help but feel kinda defeats the object of a calculator!

 

[Sadfield]

The only uncertainty in that case was I'm still getting a feel for how that particular strain (LVIPA) behaves. The same yeast attenuated much more "normally" in 2 pale beers (a bitter and an AIPA) I also used it in.

LVIPA - Lallemand Verdant?

If so, according to their technical data sheet they only list Sweet Stout in the appropriate styles and state attenuation as being medium to high, hinting at a yeast that attenuates better in pale wort. Perhaps, it just doesn't like the complex sugars resulting from reduced diastatic power in the grist and your high-ish mash temp. Plus, there's also evidence that highly kilned grains have less nutrients, and maillard reaction products that can inhibit yeast. I also note that 5.5g in 11L is the bottom end of Lallemands recommended pitch rate of 50-100g a hectolitre. So, it could be a compounding of the following factors amplifying the issue with highly kilned grains being less fermentable than pale. A more dextinous wort with less nutrients combined with using a yeast that doesn't perform as well in dark wort. Which is also being pitched at the lowest recommended level, which would further require more nutrients from the wort to grow. Making the job hard work for your yeast, causing it to stall at 60% attenuation.

 

[matt76]

@Sadfield , yep Lallemand Verdant IPA.

But what do the spec sheets have to say, I wonder, about Imperial A-09 Pub, MJ M36, Wyeast 1318 and BRY-97?

That doesn't make you wrong, but I think my argument is simpler. Nevertheless, I'll take a look into it

 

[foxy]

This is mine on Brewers Friend, no problem hitting final gravity even with S04, the none fermentables do what they are supposed to do, add flavour and colour, in this case the roast. To target the pH is no different than if I was brewing an English IPA, As I do mostly English beers the salt additions remain a constant. If I want my pH to go to 5.3 I will just add 3 g of lactic acid.
The late additions keep everything just so simple, 20 minutes at mash out 77 C

 

[matt76]

This is mine on Brewers Friend, no problem hitting final gravity even with S04, the none fermentables do what they are supposed to do, add flavour and colour, in this case the roast. To target the pH is no different than if I was brewing an English IPA, As I do mostly English beers the salt additions remain a constant. If I want my pH to go to 5.3 I will just add 3 g of lactic acid.
The late additions keep everything just so simple, 20 minutes at mash out 77 C

View attachment 62705

I was just looking into this @foxy - if I select Late Addition => Mash Tun for the dark malt I can see it changes the predicted mash pH but had no effect on the predicted OG, FG or ABV. Am I missing something?

(Also your dark malt addition in your recipe is pretty modest so any impact on FG is going to be small anyway)

Again I would stress, I have a method that allows me to accurately predict FG so in that sense in not worried.

But the issue still remains that as far as I can see the calculators do seem to make some pretty unrealistic predictions about the fermentability of dark malts, which seems to defeat the object of having a calculator.

 

[foxy]

I was just looking into this @foxy - if I select Late Addition => Mash Tun for the dark malt I can see it changes the predicted mash pH but had no effect on the predicted OG, FG or ABV. Am I missing something?

(Also your dark malt addition in your recipe is pretty modest so any impact on FG is going to be small anyway)

Again I would stress, I have a method that allows me to accurately predict FG so in that sense in not worried.

But the issue still remains that as far as I can see the calculators do seem to make some pretty unrealistic predictions about the fermentability of dark malts, which seems to defeat the object of having a calculator.

When the malts which are classed as none fermentable are kilned they kill the enzymes to convert the starch into sugar, What they don't do is eliminate the starch. So the diastatic power of the base malt can still convert the starch in the none fermentables. Chucking the none fermentables in at 77 C mash out one is getting the desired colour and flavour without increasing the fermentable wort, the enzymes in the base malt has denatured with the increase in temperature, so can't convert the starches left in the unfermentable grains. This is the way I interpret it, I could add more roast, even chocolate. It isn't going to make any difference to the outcome.
Maybe this table will help.
http://www.brewunited.com/grain_database.php#key

 

[Sadfield]

But the issue still remains that as far as I can see the calculators do seem to make some pretty unrealistic predictions about the fermentability of dark malts, which seems to defeat the object of having a calculator.

I rarely, if at all see others making this observation, which suggests the calculators work relatively well for most. Even the OP got close to the predicted FG after restarting a stalled fermentation.

It's a big ask, given the range of different systems and setups we all use, for a single piece of software to accurately predict FG for every user given the massive range of variables in process, ingredients and equipment. Also, as with any software, its only as good as the data it is provided.

 

[foxy]

It's a big ask, given the range of different systems and setups we all use, for a single piece of software to accurately predict FG for every user given the massive range of variables in process, ingredients and equipment. Also, as with any software, its only as good as the data it is provided.

Even with the same equipment brewers will tend to come up with different results. There are just as many variables between the individual brewers themselves.

 

[matt76]

@Sadfield @foxy I've been mulling this over some more for the last few days.

First up, let me say I put the OP's recipe through Brewer's Friend and applied my own method to it and came up with an FG of between 1.016-1.019. So my original assertion that 1.026 was "done" was incorrect (TBH even from my own experiece I knew in the back of my mind that was high!)

Plus, there's also evidence that highly kilned grains have less nutrients, and maillard reaction products that can inhibit yeast. I also note that 5.5g in 11L is the bottom end of Lallemands recommended pitch rate of 50-100g a hectolitre.

OK, this is interesting. Like all good theories it makes a predicition - if I was to double my pitch rate and/or add some yeast nutrient then I should see a lower FG in my dark beers, right? Unfortunately I don't plan to make anything dark now probably until later in the year. But I'm open to the possibility so come the time then I may well put this theory to the test

So, it could be a compounding of the following factors amplifying the issue with highly kilned grains being less fermentable than pale. A more dextinous wort with less nutrients combined with using a yeast that doesn't perform as well in dark wort. Which is also being pitched at the lowest recommended level, which would further require more nutrients from the wort to grow.

amplifying the issue with highly kilned grains being less fermentable than pale.

OK, so you agree then that higly kilned grains are less fermentable than pale? Which comes back to one of my earlier points - if you make a test recipe in a calculator and switch the dark malt for a pale malt then we should expect the calculator to predict a different FG. But they don't.

When the malts which are classed as none fermentable are kilned they kill the enzymes to convert the starch into sugar, What they don't do is eliminate the starch.

This is a good point - I guess I kinda knew it implicitly but good to ram the point home, the distinction between effect of heat on the enzymes and the starch My question here is does the kilning also impact the starch and hence the fermentability of the grains? My experience/my theory suggests yes it does, and more highly kilned grains (i.e. darker) become progressively less fermentable. But I acknowledge @Sadfield 's alternative explanation about pitch rate and yeast nutrient is also a well reasoned alternative explanation.

I rarely, if at all see others making this observation, which suggests the calculators work relatively well for most.

I disagree - you may not have seen them but in the last 6-12 months I've commented on a number of threads with similar symptoms to my own and put forward my theory. They often appear as either poor attenuation in dark beers, or particularly low attenuation from an already low attenuating strain (which then turns out to have been used in a dark beer!).

It's a big ask, given the range of different systems and setups we all use, for a single piece of software to accurately predict FG for every user given the massive range of variables in process, ingredients and equipment. Also, as with any software, its only as good as the data it is provided.

Even with the same equipment brewers will tend to come up with different results. There are just as many variables between the individual brewers themselves.

These are fair points, there's lot's of variability between equipment and brewers. With regard to software only being as good as the data it's provided - sure, part of the problem may at times be between chair and keyboard But a good portion of the data (i.e. the malts used and their properties) are usually provided by the software. So if it really is the case that highly kilned grains are less fermentable than pale it still surpises me that this isn't better accounted for in the calculators (and I would be genuinely interested to know if that is or isn't the case).

 

[Sadfield]

disagree - you may not have seen them but in the last 6-12 months I've commented on a number of threads with similar symptoms to my own and put forward my theory. They often appear as either poor attenuation in dark beers, or particularly low attenuation from an already low attenuating strain (which then turns out to have been used in a dark beer!).

But were you doing the same in those threads as you did in this, and attaching your own theory to a stalled fermentation issue?

Have you tried beersmith? I find it works for me.

Another thought, are you observing OG? In that the software is assuming good fermentation conditions and calculates that the dark grains will add less fermentables by weight to the OG rather than cause the yeast to attenuate less, raising the FG.

 

[matt76]

But were you doing the same in those threads as you did in this, and attaching your own theory to a stalled fermentation issue?

From memory, no - I'd have to go back and check each case but I've a vague memory that in at least one case I checked the brewer's observations using my own theory and it tied up.

Have you tried beersmith? I find it works for me.

That's the one I haven't tried yet, but I'd like to.

Another thought, are you observing OG? In that the software is assuming good fermentation conditions and calculates that the dark grains will add less fermentables by weight to the OG rather than cause the yeast to attenuate less, raising the FG.

I'm not quite following you here. But the software calculates my OG correctly regardless whether I'm brewing a pale beer or dark.

I don't have to fiddle anything to achieve this and my brewing these days is consistent enough that I usually hit my OG +/- 1 point, or 2 at the worst.

My observation is that all grains add to the OG regardless of colour, but my suggestion is that dark grains contribute less fermentable "stuff" per unit weight.

 

[Sadfield]

My observation is that all grains add to the OG regardless of colour, but my suggestion is that dark grains contribute less fermentable "stuff" per unit weight.

Yes, but have you compared OGs? 500g of Roasted Barley will add less fermentables to the OG, but those fermentables should still ferment out, not ferment less. If you swapped it to Maris Otter, the OG will go up, but the yeast will still ferment to roughly the same FG, if the fermentation is healthy in both cases.

 

[matt76]

Yes, but have you compared OGs? 500g of Roasted Barley will add less fermentables to the OG, but those fermentables should still ferment out, not ferment less. If you swapped it to Maris Otter, the OG will go up, but the yeast will still ferment to roughly the same FG, if the fermentation is healthy in both cases.

Ah, ok, got you now

Yeah, for sure it makes sense to me that 500g roasted barley might only yield, say, 100g (complete guess!) fermentable stuff, whereas 500g Maris Otter might yield 350g (another guess!) fermentable stuff.

So for a given weight of grain we expect to get more fermentable stuff from pale malt - agreed

So to put this to the test I refer you back to the test recipe I suggested before.

If we swap out the dark malt for a pale malt (I tried RB & CM for dark, then MO, Vienna & Lager for pale) then in Brewer's Friend at least the OG/FG changes by no more than 1 point.

So to answer your question, in BF at least, no the OG does not change depending on dark or pale malt - certainly not by enough to explain the difference I see in FG.

To some degree this makes sense - when we use dark malts we are unquestionably adding "stuff" e.g. colour, flavour, mouthfeel etc. I can easily believe this "stuff" adds to the OG.

But the same "stuff" may not be fermentable hence it seems reasonable to me to expect the FG to be higher, reflecting the continued presence of this unfermentable "stuff".