BIAB #3 - Oatmeal Stout

[MrN]

Took the day off work yesterday and decided to tackle my 3rd BIAB and 6th ever homebrew. This time I thought I'd go with an oatmeal stout, using a recipe I based on others I've read:

Boil Size: 15.41 l
Batch Size (fermenter): 16.00 l
Estimated OG: 1.052 SG
Estimated Color: 73.8 EBC
Estimated IBU: 30.1 IBUs
Brewhouse Efficiency: 75.00 %

2.65 kg Pale Malt, Maris Otter (5.5 EBC) - 72.6%
0.34 kg Oats, Flaked (2.0 EBC) - 9.3%
0.16 kg Caramel/Crystal Malt - 60L (130.0 EBC) - 4.4%
0.14 kg Caramel/Crystal Malt -120L (240.0 EBC) - 3.8%
0.20 kg Chocolate Malt (1000.0 EBC) - 5.5%
0.16 kg Roasted Barley (1200.0 EBC) - 4.4%
51.00 g East Kent Goldings (EKG) [5.46 %] - Boil Hop 30.1 IBUs
3.00 g Irish Moss (Boil 15.0 mins)
1.0 pkg West Yorkshire Ale (Wyeast Labs #1469)

Started off by treating 15.5L of water with half a crushed campden tablet and leaving to stand overnight. The next day, I then tested with my salifert kit and acid treated as necessary (I have pretty hard water).

My target mash temp was 66°C so, based on previous experience, I preheated to 68°C. Doughed in and was about 0.5°C under so put the heat on for a bit (nice thing about BIAB!).

After an hour I removed the bag and dunked in about 6L of hot, acid treated water:

I used about 2.5L to top my pot up to about 15.5L again, for the boil.

Now this is where things went a bit wrong... I'd based my efficiency on my previous 2 BIABs, where I was getting around 75% BH efficiency and somewhere around 80% mash efficiency. I had expected my pre-boil SG to be in the region of 1.060/1.062 except I measured it and it was only 1.050, 10 points too low! After a brief panic I had a go at some quick calculations and fortunately had some DME lying around. I added all I had - about 400g, a 50/50 mix of dark and light DME. This was just enough to raise the wort 10 points to 1.060!

Anyway, I completed the boil, with my hop and other additions. I chilled down, strained into my FV and topped up with 3L of Ashbeck bottled water. Through some sort of blind luck I managed to hit my target volume (16L) and OG (1.052)! I pitched my 1469 yeast, which was harvested from my previous brew and put the FV away to do its thing. This morning it's bubbling away nicely, 1469 is certainly an active yeast strain!

Despite the efficiency issue, I'm quite pleased how this went in the end. Can anyone suggest a reason why I might have seen such poor efficiency this time? My first BIAB was a brown ale with similar sized grain bill and similar amounts of specialty grain and that was fine. Only major difference this time was using oats, I just used Sainsbury's own brand porridge oats. Could this have been an issue? Let's hope this ferments down nicely and I get a nice oatmeal stout for the winter months!

[Sadfield]

Nice brew and write up. Re: Efficiency, the mash ph may have been too low, with acid treatment and dark grains.

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[MrN]

Nice brew and write up. Re: Efficiency, the mash ph may have been too low, with acid treatment and dark grains.

Could be this. I calculated my acid additions with the brewers friend mash calculator. My alkalinity is around 265ppm CaCO3 so I used about 12.5ml CRS in 15.5L. Unfortunately I don't have a ph meter, just strips which aren't especially clear. Based on what I measured, the mash ph could have been anything from 5.0 to 5.6... I figure for my next brew I'll predict efficiency to be somewhere between what I got this time and what I have had before. I better make sure I'm also stocked with DME!

EDIT: Just had another thought. I got most my grain from a different place this time (malt miller). Is it possible that they do a coarser grind than some other places? Think I used the homebrew shop and geterbrewed previously.

[MrN]

Just taken a gravity reading, 1 week into fermentation. It's at 1.016 which is higher than I was expecting. I was hoping to get at least down to 1.014, ideally 1.012.

I suppose I had a lot of less fermentable grains in there, not sure whether beersmith takes these into account when estimating FG. Anyway it's at least still in the style guidelines, maybe it'll go down a little more over the next week or so.

[Clobber]

If you put in the the notes when ordering from the MM that it's for BIAB he does send out a slightly different crush specifically for BIAB

[MrN]

If you put in the the notes when ordering from the MM that it's for BIAB he does send out a slightly different crush specifically for BIAB

Ooh, good information, thanks!