Porter and stout are certainly beer styles that made their way around the world and were transformed over the last 200 years or so into a vast amount of different sub styles, with dry Irish Stout, English Porter, hop-forward American Porter, Imperial Stout just being a few examples. One sub-style of this hasn’t been picked up that much: German Porter. 19th century beer literature is full of evidence that bottled Porter imported from the UK was a very common beer in Germany, with Porter being almost twice as expensive as Munich lager beers. So naturally, by the early 20th century, and probably earlier, it was brewed domestically.
Several sources exist that describe some very general properties of German Porter. In addition to that, I was able to find three sources that document possible grists and hopping rates.
Original gravity: German Porter was generally characterized as Starkbier, a generic designation in Germany for beer with an OG of 16% or more, and at least 6.5% ABV. Kulitzscher, in the book “Handbuch zur Fabrikation obergäriger Biere” from 1930, describes that OG at 16 to 20%. “Handbuch der Ernährungslehre” from 1920, mentions an OG of 18%. The brewmaster of the Groterjan brewery, Dörfel, mentions an OG of 18% for the pre-war Porter that was brewed in small amounts at Groterjan, but describes the general beer type as going up to 22%. The more recent “Abriss der Bierbrauerei” bei Prof. Narziss mentions a lower range of 13 to 16%.
Grists: three sources describe possible grists. The oldest one is is Kulitzscher in 1930, who mentions Munich malt as base malt, 20% (sic!) caramel malt, and 6% debittered roasted malt. Dörfel on the other hand describes the grist as 70% Munich malt, 20% pale malt, 7% caramel malt, and 3% roasted malt, as well as 400 g of caramel colouring per hectolitre. Narziss describes an even simpler grist: about 2/3 pale malt, 1/3 dark malt (presumably Munich malt), and 2 to 2.5% roasted malt.
Hopping rate: Kulitzscher says 1 to 1.5 Pfund (500 to 750g) of hops (of unknown alpha acid content) per Zentner (50kg) of grist. If we assume an alpha acid content of 3 to 4.5%, this means anything between roughly 23 and 50 IBU. Dörfel on the other hand mentions 500g of hops per hectolitre, which, if we assume the same range of alpha acid content, is equivalent to about 30 to 46 IBU. Narziss mentions 30 IBU of bitterness. Since this is a German beer style, we can assume that German hop varieties were used.
Yeast: remarkably, pretty much all sources agree that Porter needs to be fermented with Brettanomyces. Without Brettanomyces, they agree, Porter doesn’t develop its typical aroma and flavour during secondary fermentation. Dörfel mentions the use of “Porterhefe” (porter yeast), which is described as a yeast blend which contains both Saccharomyces and Brettanomyces and seems to get repitched. He also mentions though that Schönfeld of VLB Berlin was able to create pure cultures of both yeast types in the 1920’s, and that Hochschulbrauerei used pure cultures separately for primary and secondary fermentation. Interestingly, there are two sources that mention that German Porter could also be bottom-fermented: “Handbuch der Ernährungslehre” describes it as “either top- or bottom-fermented”, while Narziss says that Porter is “often bottom-fermented”.
With sources on these parameters, I think it’s quite easy to extract how German Porter was typically formulated. Despite the name, it is certainly closer to Stout due to its higher strength. One important element of British Porter and Stout in the 19th century, the matured character coming from a secondary fermentation with Brettanomyces, was certainly recognized and improved on through the use of pure yeast cultures. And it’s definitely a beer style I’d like to try: the use of large amounts of Munich malt and caramel malt to a certain extent, as well as German hop varieties, I wouldn’t be surprised if it has its very own character on top of what I’d expect from a Bretted Porter.