A couple of factors prompted the government to compel brewers to use flaked oats. First, there was a bumper crop of oats in 1942. The second was a rather more threatening development.
"Early in 1943, when the shipping position became difficult owing to the intensified U boat activity, barley was required for use in bread, and brewers were asked to replace flaked barley by flaked oats, but there were some misgivings about its use on account of its high fat content. A series of investigations was carried out to prove its suitability in order to satisfy brewers that they could be used with safety; 10 per cent. was considered a safe maximum. Owing to its huskiness flaked oats had the advantage of improving drainage in the mash tun, although, owing to its bulkiness, those brewers working with a full mash tun found it to be a disadvantage. A bad oat harvest in the following year, however, caused its use in brewing to be discontinued. The Ministry of Food then suggested that flaked oats might be replaced by dried potatoes, the drying plants in beet sugar factories used for drying the exhausted beet slices being utilized for this purpose. Investigations carried out with potatoes dried in this manner, however, proved them to be quite unsuitable for use in brewing owing to the unpleasant flavour imparted to the beer, and as the anticipated surplus of potatoes did not materialize, flaked barley was again used to replace flaked oats, and has continued up to the present time."
Journal of the Institute of Brewing Volume 52, Issue 3, May-June, 1946, page 121.
If you remember, flaked barley was itself a replacement for flaked maize. The use of potatoes in brewing might sound revolting, but I’ve found 19th-century German recipes which included potatoes. No reason why you couldn’t use potatoes in brewing. They are full of starch after all.
No surprise then that this XX, which was brewed in October 1943, contains flaked oats. You’ll note, to just about the maximum safe amount of 10%. But the total percentage of oats was even higher because there was also almost 5% malted oats in the grist. I like to call this Oat Mild. Any chances of that catching on as a style?
The adjuncts are the main difference between this grist and the one from 1942. The percentages of amber and crystal malt, as well as No. 3 invert sugar, remain around the same. What I’ve listed as mild malt was actually partly SA malt. As I don’t think you’ll be able to find that, I’ve upped the mild malt amount.
As usual, it was primed like crazy, raising the OG by 4º to 1035.4º. Which is a bit more reasonable. If you want to simulate this, add some No. 2 invert at the end of primary fermentation.
|1943 Barclay Perkins XX|
|mild malt||4.25 lb||60.89%|
|amber malt||0.67 lb||9.60%|
|crystal malt 60 L||0.50 lb||7.16%|
|flaked oats||0.75 lb||10.74%|
|malted oats||0.25 lb||3.58%|
|No. 3 invert sugar||0.50 lb||7.16%|
|Fuggles 105 mins||0.75 oz|
|Fuggles 60 mins||0.50 oz|
|Goldings 30 mins||0.50 oz|
|Mash at||150º F|
|Sparge at||165º F|
|Boil time||105 minutes|
|pitching temp||61º F|
|Yeast||Wyeast 1099 Whitbread Ale|