How to improve efficiency

[LesTom]

I brewed a (in my opinion) a very good stout. It was a 4 litre BIAB batch and the only problem was I was looking to make RIS at about 9 - 11% ABV.
Please don't misunderstand, it wasn't the ABV that was the most important aspect of my finished stout, it was more to do with the fact that it finshed at 1.020 from a starting gravity of 1.078.
I'll attach a photo of my ingredients and hope that some of you knowledgeable folks can point me in the direction of how to improve the efficiency if I make another batch. I'm thinking that some if the grains maybe aren't as fermentable or I need to mash at a higher temperature than 66°C?

 

[RichardM]

What yeast did you use? What OG and FG were you expecting?
A higher mash temperature would have resulted in more sugars that are unfermentable (or slow to ferment), so wouldn't have helped to get the FG lower.

 

[foxy]

Temperature wasn't the problem, unless you mashed in at a too higher temperature. What jumps out at me is your grain bill, you have far to much chocolate, and roast barley.

 

[Buffers brewery]

Plugging your numbers into the Brewhouse efficiency calculator (top of the page) looks like your Brewhouse efficiency is around the 50% mark. At an efficiency of 70% you should get an OG of around 1.11 which with a FG of 1.020 would give you an ABV of 12%
What method do you use? Sparge or No Sparge? How long is your mash?

 

[LesTom]

Plugging your numbers into the Brewhouse efficiency calculator (top of the page) looks like your Brewhouse efficiency is around the 50% mark. At an efficiency of 70% you should get an OG of around 1.11 which with a FG of 1.020 would give you an ABV of 12%
What method do you use? Sparge or No Sparge? How long is your mash?

I rinsed the grains with 500ml of water after a 60 minute mash at 66°C

 

[LesTom]

Temperature wasn't the problem, unless you mashed in at a too higher temperature. What jumps out at me is your grain bill, you have far to much chocolate, and roast barley.

OK, thanks for that. What would you dial the chocolate malt and roast barley back to?

 

[foxy]

OK, thanks for that. What would you dial the chocolate malt and roast barley back to?

For me a good figure for chocolate would be 6-7% that is enough to give a nice chocolate flavour, if I used the roast barley about 3% I prefer Brown malt. Both going in at mash out for the last 15 mins. (mash out) or hot or cold steep and add to the boil.

 

[The Baron]

As Foxy says if you are using High roasted grain it is best to put it in late in the mash so as to not bring out too astringent/harsh flavours from them or you could do a steep and add the liquor from that to again save on harsh flavours, you will still get the colour in your beer by doing this

 

[zeptobrewer]

For a 4l batch, how much water did you mash with, how much did you sparge with and how much was left after the boil off?

Did you take a pre boil gravity reading?

 

[LesTom]

For a 4l batch, how much water did you mash with, how much did you sparge with and how much was left after the boil off?

Did you take a pre boil gravity reading?

Mashed with 6 litres, sparged with 500ml and just over 4 litres was left after the boil. I didn't take a pre boil gravity reading.

 

[chrisb8]

I would think that a FG of 1.020 is good for a stout, I have had them finish higher. The issue may be as @Buffers brewery says that you haven't got as high OG as you could have had with higher efficiency. I know it's only a small batch but a sparge of just 0.5L surely can't wash as much sugars from the grains as possible.

 

[Buffers brewery]

I think I agree with @chrisb8 . Don’t think think 500 mls is enough sparge water to wash the sugar out of 2 kg of grain. Also, do you stir the mash at intervals? And a good squeeze at the end?

 

[foxy]

I think I agree with @chrisb8 . Don’t think think 500 mls is enough sparge water to wash the sugar out of 2 kg of grain. Also, do you stir the mash at intervals? And a good squeeze at the end?

I disagree with that, 1.020 FG is pointing directly at the high level of unfermentabe sugars in the grain bill. More sparge water may get a couple of points but that's all. He re-pitched more yeast, no matter how much yeast you throw at it doesn't make a non fermentable sugar ferment.
Also we don't know what the dough in temperature was, that could have had an adverse effect on the beta amylase if it was to high.

 

[Buffers brewery]

Yes, I agree with you @foxy . That’s the problem with these kind of problems, there are too many variables to pin down an exact cause. You can just suggest the possible culprits. I would’ve expected the OG to be higher than the 1.078 recorded. Not knowing the temperature profile of the mash is a problem, as you say, as this can influence un-fermentables. It would be interesting to know the volume of wort at the beginning of the boil. The total quantity of water used was 6.5 litres, some of which would be retained by the grain and some lost in the boil leaving 4 litres. I still think the OG is a bit light.

 

[Gerryjo]

I also agree with @foxy as there is 600g of unfermentable grains in that bill which is over a quarter of the total grainbill and I wouldn't use that in a 23l batch.
If I was brewing that and as others have mentioned reduce the dark grains and add at the end of the mash or do a cold steep the night before and add to the boil,leave out the wheat and increase your oats to between 5 or 10% for mouth feel and texture,base malt to 85% but when looking for a high ABV stout use your base malt only in your calculator to get the desired ABV then use this number as your 85% then add your oats, chocolate,roasted malts to make the rest.
If you were to use oats @10% leaving 5% for dark malts I would be tempted to give it a 3 way split of chocolate,roasted and carafa 3 as this will add to your colour but reducing the astringency of the roast and boosting the rich chocolatey flavour.

 

[foxy]

We see so many "stuck ferments" what beer is the usual suspect "stout" usually the yeast is the one to carry the can. Though the sugars in the dark grain are soluble they are not fermentable. The mash temperature that the OP used was fine, it was just the ratio of the dark grain to the rest of the grain bill. In fact I would say it was a wonder it got down to 1,020.
I think now the OP should read up about what medium crystal through to roasted barley are actually bringing to the table, while there is evidence of some crystals actually lowering the FG it isn't really a great deal.
While the mash temperature was fine if the dough in occurred at a higher temperature then the beta amylase could be denatured very rapidly. That is a theory which prompts me to dough in below my target temperature and bring it up to my mash temperature. (not below 60 C but)
As the beta amylase is the main contributor to a fermentable wort, and stops working at 65 C, for the next stout Les Tom, mash for one hour at 64 C and 30 mins at 68 C. If you don't do a mash out, steep the non fermentable grains in cold water overnight or 77 C water for twenty minutes or so. (read up on cold and hot steeping) this will reduce the risk of astringency associated with dark grains. Also read up on ratios of non fermentable grains to the base malts in the grain bill.
https://byo.com/article/understanding-enzymes-homebrew-science/

 

[LesTom]

We see so many "stuck ferments" what beer is the usual suspect "stout" usually the yeast is the one to carry the can. Though the sugars in the dark grain are soluble they are not fermentable. The mash temperature that the OP used was fine, it was just the ratio of the dark grain to the rest of the grain bill. In fact I would say it was a wonder it got down to 1,020.
I think now the OP should read up about what medium crystal through to roasted barley are actually bringing to the table, while there is evidence of some crystals actually lowering the FG it isn't really a great deal.
While the mash temperature was fine if the dough in occurred at a higher temperature then the beta amylase could be denatured very rapidly. That is a theory which prompts me to dough in below my target temperature and bring it up to my mash temperature. (not below 60 C but)
As the beta amylase is the main contributor to a fermentable wort, and stops working at 65 C, for the next stout Les Tom, mash for one hour at 64 C and 30 mins at 68 C. If you don't do a mash out, steep the non fermentable grains in cold water overnight or 77 C water for twenty minutes or so. (read up on cold and hot steeping) this will reduce the risk of astringency associated with dark grains. Also read up on ratios of non fermentable grains to the base malts in the grain bill.
https://byo.com/article/understanding-enzymes-homebrew-science/

Thanks @foxy plenty for me to think about there for my next stout.
I will definitely cut back the chocolate malt and roasted barley and I'll do the stepped mash as you say.
Thanks to everyone who has contributed with their ideas this place always impresses me with the helpful information that are given by the forum members

 

[Covrich]

I would also suggest a cold steep of the roasted and chocolate malts.. the one time I did that, the stout was very smooth and had the falvours..

One thing to note it can be a little more cola coloured than jet black

 

[Northern_Brewer]

It was a 4 litre BIAB batch and the only problem was I was looking to make RIS at about 9 - 11% ABV...it was more to do with the fact that it finshed at 1.020 from a starting gravity of 1.078.

That implies an attenuation of 74% which is fine - you still haven't said what yeast you are using but you can expect yeast to struggle a bit in such a strong wort. This is a good guide to fermenting big worts : https://t.co/XYm3z97Z5V

But that doesn't seem to be the problem - you might get a point or three below 1.020 but it's very much part of the style to have a reasonable FG - indeed the BJCP guidelines are :
OG: 1.075 – 1.115
FG: 1.018 – 1.030
ABV: 8.0 – 12.0%
IBUs: 50 – 90
SRM: 30 – 40

So you're already at the lower end of the target FG. So the problem is in your mash not the fermentation. Again you need to be realistic - the efficiency will always be lower for these kinds of big worts. If your efficiency for session beers is 75%, then you should probably expect no more than 65% for this kind of beer, maybe less. And just doing such a small batch will probably hit efficiency too.

Reduced mash efficiency is one reason that few commercial breweries will ever go all-grain for these kinds of beers, once you're going above 1.075 or so they will almost always be adding sugar in some form, so that's one thing to think about.

And it might be worth thinking about doing a partigyle next time. Rather than diluting your imperial stout wort with spargings, just design a recipe for say 10 litres, mash with 7 litres for the first runnings, take 5 for the RIS and then use 2 litres of first runnings and 3 litres of sparge for a smaller beer.

This also has the advantage of giving you something to drink whilst you're waiting for the RIS to mature!