The grist is surprisingly complex, including a total of five malts. Two – pilsner and dark Munich malt – form the base. The remaining three are coloured malts: broeimout, caramelmout and kleurmout. The first is a strange type of malt which wasn’t cooled during the germination process which caused it to stew. This is a description from Dutch brewing dictionary (https://www.encyclo.nl/begrip/Broeimout).
“In the case of broeimout, there is no cooling during the germination process, so that the temperature rises quite high and the flour body dissolves a great deal. Due to the higher germination temperature, it is not necessary to kiln at a high temperature.
The colour of the malt darkens due to the germination heat alone to about 30—40 EBC. However, broeimout cannot be 100% of the grist, as many enzymes have been destroyed by the higher temperatures. Amber malt is sometimes also called broeimout, but this does not always necessarily the case.”
The kleurmout wasn’t added at the start of the mashing process with the other grains, but added to the lauter tun just before the third decoction.
The hops were all Leitmeritz I from 1934. That’s the German name of a town in Czechoslovakia and I’ve assumed the hops were something like Saaz.
|1935 Heineken Bok|
|pilsner malt||7.25 lb||44.06%|
|Munich malt 20 L||7.25 lb||44.06%|
|caramel malt 60 L||0.33 lb||2.01%|
|carafa III||0.125 lb||0.76%|
|Hallertau 120 mins||0.33 oz|
|Hallertau 60 mins||0.50 oz|
|Hallertau 30 mins||0.67 oz|
|Mash double decoction|
|Boil time||150 minutes|
|pitching temp||44º F|
|Yeast||WLP830 German Lager|
|Bok 5th Aug 1935|
|Mash in at 36º C (97º F)||20|
|Raise whole mash to 50º C (122º F)||5|
|Draw off first decoction and raise to 70º C (158º F)||30|
|Boil first decoction||30|
|Rest whole mash at 53º C (127º F)||15|
|Draw off second decoction and raise to 70º C (158º F)||20|
|Boil second decoction||20|
|Rest whole mash at 64º C (147º F)||10|
|Draw off third decoction and raise to 100º C (212º F)||5|
|Boil third decoction||20|
|Mash at 74º C and mash out (165º F)||5|
|Sparge at 74º C (165º F) and rest||60|
|Draw off main wort||65|
|Draw off second wort||150|
|Source: Heineken Brouwjournalen van de proefziederij, 1935 - 1957 held at the Amsterdamse Stadtsarchief, document number 1785-1792, page 10.|