Oatmeal Stout: an experiment on fruit 3 ways.

Last year I brewed an oatmeal stout after visiting Wylam Brewery and their tap room just before they had moved production there.

One of the beers available to try as part of the tour was a NZ oatmeal Pale: All Gone South. This had a massive amount of New Zealand hop aroma and flavour against the mouthfeel of the oats and was really unexpected – a bit like the sensory shock that a Black IPA provides.

What was really surprising was that they used a huge 30% of 2-3 types of oats in their grain bill. Normally this proportion of oats can lead to a stuck mash and lautering problems, but thanks to their then shiny new kit they had a way of using such a high amount of hops in this beer without encountering these problems.

In getting home, I thought I would try a brew day with more than 10% oats in the grain bill. As I’d did not have any New Zealand hops available I thought I would try an oatmeal stout recipe and experiment with adding fruit after primary fermentation.

I was  able to do this in my kitchen / stove top set up to split the finished beer after fermentation between 2 different fruits, and keep 1 as the control.

Oatmeal Stout Recipe:

Type: All Grain
Batch Size: 14.00 l
Boil Size: 16.47 l
Boil Time: 60 min
End of Boil Vol: 14.58 l
Final Bottling Vol: 13.00 l
Fermentation: Ale, Two Stage

Efficiency: 72.00 %
Est Mash Efficiency: 72.0 %

Prepare for Brewing

  • Total Water Needed: 22.63 l

Mash or Steep Grains

Mash Ingredients
Amt Name Type # %/IBU
3.00 kg Pale Malt, Maris Otter (4.5 EBC) Grain 1 69.8 %
0.45 kg Oats, Flaked (2.0 EBC) Grain 2 10.5 %
0.25 kg Roasted Barley (1100.0 EBC) Grain 3 5.8 %
0.15 kg Chocolate Malt (940.0 EBC) Grain 4 3.5 %
0.15 kg Special B Malt (300.0 EBC) Grain 5 3.5 %
0.15 kg Wheat, Torrified (3.3 EBC) Grain 6 3.5 %
Mash Steps
Name Description Step Temp Step Time
Mash In Add 12.82 l of water at 74.6 C 68.9 C 45 min
  • Estimated pre-boil gravity is 1.059 SG
Boil Ingredients
Amt Name Type # %/IBU
0.10 kg Brown Sugar, Dark (98.5 EBC) Sugar 7 2.3 %
0.05 kg Dememera Sugar (3.9 EBC) Sugar 8 1.2 %
15.00 g Target [9.50 %] – Boil 60.0 min Hop 9 21.7 IBUs
0.25 tsp Irish Moss (Boil 15.0 mins) Fining 10
15.00 g Bramling Cross [6.00 %] – Boil 15.0 min Hop 11 6.8 IBUs
15.00 g Fuggles [3.90 %] – Boil 15.0 min Hop 12 4.4 IBUs
Steeped Hops
Amt Name Type # %/IBU
15.00 g Bramling Cross [6.00 %] – Steep/Whirlpool 10.0 min Hop 13 2.5 IBUs
15.00 g Fuggles [3.90 %] – Steep/Whirlpool 10.0 min Hop 14 1.6 IBUs
  • Estimated Post Boil Vol: 14.58 l and Est Post Boil Gravity: 1.069 SG

Cool and Transfer Wort

  • Cool wort to fermentation temperature
  • Transfer wort to fermenter

Pitch Yeast and Measure Gravity and Volume

Fermentation Ingredients
Amt Name Type # %/IBU
1.0 pkg British Ale (White Labs #WLP005) [35.49 ml]


I couldn’t quite bring myself to go the whole 30% with the oats, but the mash tun worked well and I throttled back when draining the wort to prevent a stuck mash.

I also used a half fly / batch sparge method rather than a classic batch sparge. Placing a folded up piece of tin foil on the top of the grain bed stopped it getting disturbed and worked really well as the sparge water was slowly poured onto the top. This might have helped prevent a stuck sparge coupled with the very slow run off rate I adopted.

The boil was fairly uneventful and I used some of the hot wort to dissolve the sugar addition near the end to ensure none was scorched on the bottom of the kettle.

After cooling with the homemade immersion chiller, it was fermented using WLP005 – British Ale yeast and the real fun came after primary fermentation was completed and it was time to split it and put in on fruit.

I decided to split the finished batch into thirds (of roughly 5 litres each), and put 1/3 on  300g cherries, 1/3 on 300g dates and leave the remaining third as the base beer.

The Cherries were fresh which I just halved and left the stones in. The Dates were Medjool Dates but were halved and pitted. In hindsight, I would probably quarter the dates as they were very difficult to extract from the demijohn later.

I calculated the base beer came to 6.69% ABV without the fruit – which might have added a couple of extra gravity points in each case.

After 2 or 3 weeks on the fruit in demijohns, there was very little sign of any secondary formation, and it looked / felt like it was time to bottle the experiment.

Unfortunately I didn’t check the FG for the version racked onto the dates before adding the priming sugar – and those bottles had far too much sugar left in which led to over carbonation. They were the most “lively” of the types of oatmeal stout but this one was the tastiest of the three.

Tasting Notes:

The base Oatmeal stout was good, and had a good well rounded flavour and silky mouthfeel thanks to the oats. There was no astringency and the hops were present in flavour and aroma (a slight blackberry note which I sometimes get from the Bramling Cross) but it was not too bitter. I queried vanilla(?) chocolate(?) and even treacle(?) the last 2 of which I put down to the dark sugars used.

I thought it was slightly oxidised since it was left in the original fermenting bucket with masses of headspace whilst the other two rested on the fruit. If I had a third demijohn to hand I should have put it into secondary to keep the oxygen to a minimum

The Date Oatmeal stout had a rich Christmas / fruit cake quality to them which went really well. The over carbonation caused a lot of yeast to be kicked up when pouring, but didn’t overly harm the flavour.

The Cherry Oatmeal stout had a dry, slightly tart (fruit – rather than sour) flavour which was noticeable as cherry, but not as good as the Date version. I wonder if some chocolate nibs and more cherries might have made it into a better beer (black forest stout anyone)?


Some comments from a comparison taste of the three beers at the Chorlton Homebrewers group were that the version put on Dates was the better version despite the (massive) over carbonation (it may have hit the ceiling).  It had roasty, caramel and fruity flavours – and it would be an ideal after dinner sort of beer given the fruit flavour, mouthfeel and residual sweetness (although that wasn’t planned).

It has put me in mind of making it again but with the addition of some other fruits from fruit cake on a slightly bigger version for Christmas as I find spiced beers to be a taste I haven’t really acquired.

In summary, the demijohns worked really well and it is a great way to experiment with different yeasts using the same worts, or using post fermentation additions for a little extra work.

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