Die Herstellung obergäriger Bier und die Malzbierbrauerei Groterjan A. G. in Berlin, and we’ve got to the juiciest bit: how they made their Berliner Weisse. This is not a literal translation but I think all the most salient details are included.
The gravity is 8º Plato and the grist is 1/3 wheat malt and 2/3 barley malt. 100kg grist per 3hl water. 25–30g hops per hl and they are put right in with the mash. A decoction mash is used. The mash starts at 30 C and is raised slowly to 53–54C and held for half an hour (protein rest). Then the mash is raised to 75C and held until conversion is completed, which usually happens by the time the mash has reached that temperature.
[I was surprised the proportion of wheat was so low. And the mash hopping makes sense when you realise there isn’t a separate wort boil. The hops would get isomerised during the boiling of part of the mash during the decoction, adding some bitterness to the beer.]
Then 1/3 of the mash is taken out to the lauter tun and what remains in the kettle is boiled for half an hour. When both parts are combined again it is important to make sure that the saccharification temperature is not exceeded (not over 76 C). The mash is left 40 minutes before beginning to run off the wort.
Läutering is crucial with Weissbier. Both first and subsequent runnings must be absolutely clear. For this it is best to have an unbroken run-off, without disturbing the grain bed, unless necessary to avoid channeling. For the same reason the sparge water can be applied using the Hoffmann’s “floating box” (Schwimmkiste). Using this, the entire sparge water can be applied immediately following the wort, enabling a good extraction from the grain.
After the run-off and gravity correction of the clear wort in the kettle, the wort is heated to about 95 C for 15–20 minutes, pumped out and immediately cooled to 18 C.
It would be better to boil the wort at 100 C in the interest of killing off pediococcus, which cause ropiness, a sickness particularly feared in Berliner Weisse. However, the beer tax law states explicitly (at the request of the Weissbier brewers themselves), that a particular characteristic of Berliner Weisse, distinguishing it from others, is that the wort is not boiled.
Ropiness may appear in the bottle during conditioning. The beer becomes thick and syrupy, forming strands, caused by microorganisms of the sarcina type. The beer is utterly undrinkable in this state. If the beer is stored for several months, the slime usually completely disappears again. The beer is once again clear and fit for consumption. A residual fine aroma and a flavour reminiscent of tartaric acid remain, which are prized by some beer connoisseurs. [I don't know what tartaric acid tastes like, but that's what it says].
The sickness of weissbier, the Langwerden (ropiness), has three causes, the most important of which is Pediococcus viscosus. This sickness can be found sometimes in other types of beer and is not unknown in Belgian and British breweries. Sugar and protein are needed for this infection to take hold and the presence of yeast encourages the development of pediococcus. As a preventative measure (as recommended by Schönfeld in “Obergärige Biere und ihre Herstellung”) souring the wort to 0.1–0.15 acidity, high mash temperature, heating the wort to 80–85C for an hour, or 15 minutes’ boiling, and high attenuation are recommended. A ropy Weissbier must be kept in the brewery for months until the ropiness disappears, which means more work, tying up space and cash and interfering with the production plan. Even worse are the effects on the customers, who complain and return the beer.
A special fermenting room is kept for Weissbier and the yeast is pitched – a top-fermenting yeast which also contains rod-shaped lactic acid bacteria. The bacteria and yeast live in a kind of symbiosis: they grow under the same conditions and are found again in the head on the fermenting beer. 1L Weissbier yeast is pitched into 10hl of wort.
The fermentation is lively at 16C in the cellar. The first yeast head is skimmed off and discarded. The main head that forms afterwards is skimmed and that yeast is kept for re-use. The fermentation lasts four days, during which the temperature of the beer rises to 20C and falls to 16C again.
The beer drops bright [no indication of how long this takes] and is bottled, or sent out to wholesalers who also immediately bottle it. It is very important that the beer in the bottles contains the correct amount of residual extract necessary for the desired secondary fermentation. Weissbier should have lots of CO2, so 1% or 2% residual extract are needed. It is necessary to pay attention to whether the beer is intended to be drunk sooner or after several months.
If the beer has already fermented out too far, fresh beer can be added to bring it to the correct strength. Sugar can be used if fresh beer is not available. But this brings with it the risk of the beer exceeding the legal maximum starting gravity (for Schankbier) of 7–8º Plato.
The souring of the beer by lactic acid bacteria is temperature-dependent. Acidity increases with age. Storing the beer at 5–6 C can prevent the beer getting too sour. If it is needed to be ready quickly, it should be stored at 12–15C for 8–10 days. For the best quality, weissbier should mature for at least six weeks, though three months is preferable. For this reason the weissbier business requires a large stock of bottles, because each returnable bottle would only make it back to the brewery for refilling a few times a year.
[So Berliner Weisse breweries needed a proportionately bigger stock of bottles than others. Time to invent a beer myth: the drive to disposable bottles in the 1960s was spearheaded by Berlin breweries]
The main Weisse business is done in the summer. If there is unexpectedly high demand, the brewery may run out of well-matured beer and have to send younger beer into trade, which can be damaging for the reputation of the brewery.
At Groterjan they took these measures: large quantities of soured fresh beer are chilled and held in tanks at 5–6C, where it can stay for months without damage and clarifies. When needed, the beer is bottled and primed with sugar. The beer is sour enough already and the sugar carbonates it so that it is soon ready to drink.
As a Schankbier, the Weisse has a starting gravity of 8º Plato. As it ferments down to 1–1.2º, the finished beer is relatively strong, often 2.5–3.5% abv.
[I’m not sure that any brewer today would describe a beer of 2.5% as comparatively strong. But look how piss-weak most of Groterjan’s other beers were. It’s all a matter of perspective.]
Small quantities of strong Weisse are made sometimes with a gravity of 16–18º. That is best when matured for a year or more.
As a pale, mild and pleasantly acidic-tasting, well-attenuated beer with a high CO2 content (up to 0.5%) and excellent foam-building qualities, Berliner Weisse is a splendidly refreshing drink, especially on warm days. The beer is drunk from large, bowl-shaped glasses and some consumers love to add a slice of lemon or even some raspberry juice, the so-called Weisse mit Schuss, which is a practice abhorred by beer connoisseurs.
The pitching yeast for Weissbier is a mixture of top-fermenting yeast and lactic acid bacteria. Both multiply at roughly the same rate during the fermentation and so can be kept for the next brew. The most important bacteria (which is responsible for its particular bouquet) is S. pastorianus var. berolinensis. It produces substantial amounts of lactic acid during the main fermentation.
Cropping and storage of the Weissbier yeast is the same as other brewing yeasts but the temperature is slightly higher, 8C. The Weissbier fermentation is kept in a separate cellar to prevent contamination of the other beers with the lacto bacteria. Separate equipment and lines from the cellar to the bottling room are used. Again the bottling room and filling equipment are used exclusively for Weisse.