Irish Stout stuck fermentation

[Tricky Dicky]

I brewed this partial BIAB 16 days ago:
1.59 kg Pale Ale, Golden Promise®™ (Simpsons) (5.0 EBC) Grain 1 40.7 % 1.04 L
0.91 kg Barley, Flaked (3.3 EBC) Grain 2 23.3 % 0.59 L
0.46 kg Roasted Barley (Bairds) (1182.0 EBC) Grain 3 11.8 % 0.30 L
0.31 kg Chocolate Malt (689.5 EBC) Grain 4 7.9 % 0.20 L
0.64 kg DME Golden Light (Briess) [Boil] (7.9 EBC) Dry Extract 5 16.4 % 0.41 L
55.00 g East Kent Goldings (EKG) [5.00 %] - Boil 60.0 min Hop 6 31.4 IBUs -
1.0 pkg Irish Ale (Wyeast Labs #1084) [124.21 ml] Yeast 7 - -
Mash 67c

I created a 1L starter ( no yeast nutrient) and the flask was on a stir plate for 48 hours.

Wort OG was 1040 ( but of a cock up diluting it down, it was meant to be 1047) after taking 3 readings the last one being on day 12, all were at 1024. FV temp was started at 21c ( temp controlled in a fridge) to begin with and I cranked up to 23c on day 10.On day 13 I added a packet of Nottingham and gave it a stir, 3 days later its still at 1024. It tastes ok but will be weak as piss at 2.1% ABV. Not sure what went wrong any ideas? Anything else I could do to get the SG down a bit more?

 

[MHB]

If you want a bit more detailed answer you need to give volumes as well as masses. The extract you got may have been excellent if you were making 20L or pretty crap in a 30L batch, cant tell from here.

You have a lot of dark/roast grain in there (nearly 20%) not going to provide much in the way of fermentable extract.
Fair wack of Flaked Barley to, the extract from that much Flake from an Isothermal mash isn't going to be all that fermentable either. Personally I would always mash into water at about 50oC so you get some Glucanase activity, some Protease to.

Right now, probably not a lot you can do to get the FG down, you could have added some sugar to bump the alcohol up a bit, or add some "Dry Enzyme" but I have a suspicion that that would change the balance well away from where you want to go.
Mark

 

[hoppy2B]

You might get some more attenuation if you chuck in a packet of Belle Saison yeast Tricky Dicky. Otherwise Mark's suggestion of adding some sugar to bump up the abv is the only other good idea I think any will come up with.

 

[Tricky Dicky]

If you want a bit more detailed answer you need to give volumes as well as masses. The extract you got may have been excellent if you were making 20L or pretty crap in a 30L batch, cant tell from here.

You have a lot of dark/roast grain in there (nearly 20%) not going to provide much in the way of fermentable extract.
Fair wack of Flaked Barley to, the extract from that much Flake from an Isothermal mash isn't going to be all that fermentable either. Personally I would always mash into water at about 50oC so you get some Glucanase activity, some Protease to.

Right now, probably not a lot you can do to get the FG down, you could have added some sugar to bump the alcohol up a bit, or add some "Dry Enzyme" but I have a suspicion that that would change the balance well away from where you want to go.
Mark

Just read up a bit on diastatic power and it indicated that in general to aim for an average of 70 Lintner for your grain bill and to be safe 100 Lintner. I use Beersmith for my recipe design and can't find any field that indicates what your Lintner average is. Beersmith estimates the OG so I wonder is there a direct correlation between diastatic power and the OG estimated in BS? Should I be aiming for a Lintner level or an estimated OG?

 

[MHB]

Cant be any help you there, Lintner is the American non-system and it makes sense (sort of) if all you other units are nonsensical. But working in metric is much easier.
You are clearly light on for fermentable extract, just knowing the Lintner of the base malt wont help you a heap.
Roasted malts wont give much fermentable, un-malted adjunct will also give lots less fermentable extract more glucans, long strand starch.
Generally a decent base malt will have enough enzymes to convert itself and about half as much again in adjunct (some times more but that can cause problems to).
Mark

 

[hoppy2B]

Some time ago I read on a U.S. moonshine forum that you can use as little as say 10% malt and 90% corn grits or similar. You simply need a really long mash time. Supposedly, enzymes don't become denatured as they work. As long as you stick to the enzyme's heat tolerance they can keep on working.

 

[MHB]

Pretty irrelevant unless your wanting to make sour beer.
Yes its true, the cooler enzymes operate the longer they last (obvious tradeoff) at about 20oC an all malt "mash" would fully convert in about two weeks, clearly it wouldn't be much use to a brewer by then. It isn't true that they will last forever, but a long time yes. Might be a bit useful to people doing sour mash bootlegging - just not the beer brewers.
My point is that the recipe above just lacks enough ingredients for enzymes to turn into fermentable sugars under any conditions. Not a matter of Lintner or conversion temperature, just a badly designed recipe that cant deliver what the brewer wanted.
Mark

 

[hoppy2B]

My guess, it's a small volume in something like a 19 litre pot. The Roast Barley and Chocolate wouldn't contribute much to the gravity reading. So at 1040, if it finished at 1024, more than likely Tricky Dicky has mashed at a higher temperature than he thinks he did, resulting in a less fermentable wort.

 

[MHB]

Roast Barley has a yield around 65%, But in the roasting process most of the things that could be turned into fermentable extract are burnt to death (well - combined in milliard processes) to the point where while there is extract, little of the extract will be fermentable. Chocolate malt isn't far behind the Roast in terms of what it yields.
I have to go to work, I'll sit down later and add up all the potentials, just so you can see the bleeding obvious. Mean time have a look at this from Breiss