Saturday, 11 May 2013

How to make Groterjan Malzvollbier (bottled and draught) – Dörfel part 2

By OTFW, Berlin (Self-photographed)
[CC-BY-SA-3.0-2.5-2.0-1.0], via Wikimedia Commons
We saw yesterday that Groterjan was a brewery of a special type. It specialised in top-fermenting, mostly very low-alcohol, mostly sweet beers. Here are the beers they brewed:

a) 11.5º Malzvollbier with sugar, bottled
b) 11.0º Malzvollbier with sugar, draught
c) 4º Carameleinfachbier with sweetener, draught
d) 3º Jung- und Braunbier with sweetener
e) 8º Berliner Weissbier
f) 16º Starkbier Feinbitter
g) 18º Porter

All the beers with the exception of Berliner Weisse were made with an infusion mash [by which is meant a German-style step infusion, not a British-style single-temperature infusion].

The first four are a type which has almost died out. Look at the gravities. For comparison, a modern Pils has a gravity of about 11.5 degrees Plato before fermentation. Most are ridiculously weak by modern standards. On the other hand, the 18º Porter would be considered strong today in the German market.

A. Malzvollbier (bottled)

The grist is 5% black malt, 10% caramel malt, 25% “pale” malt and 60% Munich malt.
The hopping is just 75g per hectolitre, i.e. hardly anything. Caramel colour is added in the kettle and a sugar solution is added before bottling.

The mash is started cold with water at 13–15 C and warmed slowly over half an hour to 52º. Half an hour protein rest at 52 C. Over a further half hour the mash is heated further to 75 C and held there until complete conversion is achieved. Then they let it stand for another 40 minutes before lautering. They batch sparge for five hours (!) with water at 85 C. The last sparge water has just 0.1º Plato.

Two thirds of the hops are added to the kettle while the wort is running in, and the rest half an hour before the end of the boil. The boil begins as soon as the second sparge has stopped washing out sugar. The boil lasts 1.25 hours.

The final wort should be 6.4º and be very dark. The 5% black malt used is not enough to achieve this colour, but that quantity cannot be raised without affecting the taste. 400g caramel per hectolitre are added to deepen the colour. Through evaporation and cooling the wort has 6.5º Plato when the yeast is pitched.

The wort is allowed to settle in a settling vessel before being cooled over a Berieselungskühler (one of those things resembling a sheet of corrugated iron) – not an open cooler, Dörfel is keen to point out.

Yeast is pitched at the rate of 1L thick slurry per 8hl wort and fermentation takes place at 10 C. After 12–15 hours there is foam on the beer and the hop resins this brings up must be skimmed off and discarded. The yeast head re-forms and after a total of 40–48 hours the yeast head begins to compact and can be cropped for re-use in the next brew. It is kept in aluminium buckets, mixed with water and chilled. It can be kept for about 8 days at about 3–5 C.

The yeast cropping must take place soon enough that the beer will still throw up another head that will protect it from the air. This is particularly important for beer that will be bottled.

The fermentation is completed after 2.5–3 days at 10 C. The beer stays in the fermenters for another two or three days to drop bright and at this stage has an apparent extract of 4ª Plato.

The yeast head is not removed before bottling, it sinks along with the surface of the beer and ends up together with the sediment at the bottom. This residue is not used in the brewery but sent to the food industry.

The beer flows into mixing tanks one level below. Each holds 68hl and is equipped with mixing rakes and heating coils. Together with the beer a sugar solution of 55% [I don’t know whether here the % means the solution is 55% sugar, or that the solution is 55 degrees Plato. There are enough figures given for someone to do the maths]. 1 hl solution is mixed into every 9 hl of beer. Extra yeast is added in the tank to make sure there is conditioning in the bottle. A bottom-fermenting yeast is used because it compacts better in the bottle. This is the only time bottom-fermenting yeast is used at Groterjan (it is obtained from a lager brewery).

The mix is stirred for a quarter of an hour and heated to 25 C, then immediately filled into bottles. Normal 33cl bottles with swing-tops are used. After labelling the bottles are loaded into the pasteuriser and held there at 25C for 14–16 hours. After this time they have developed enough CO2. Samples are taken to check the beer has conditioned enough. This must be done by pouring bottles into glasses, as the use of measuring equipment has been found wanting. If the conditioning goes too far there is the danger of the bottles exploding during pasteurisation.

For the actual pasteurisation the chamber is heated by steam to 65 C over a period of 40–45 minutes and held there for about an hour, then allowed to cool to 35–30 C.

The bottles are removed and placed by hand in wooden trade crates. The bottled beer is sent out into trade the next day.

The gravity of the bottled Malzvollbier is 11.5º, 6.5º from malt and 5.0º from the added sugar. 2.5º is fermented out during the fermentation and  0.8–1.0º during bottle-conditioning, so that the finished beer still has 8.0º (4.2º from sugar), resulting in a low alcohol but very nutritious beer.

B. Malzvollbier, draught – 11º Plato

The grist, mash and boil are the same as before, but the hopping is slightly higher at 90g/hl. After the yeast is cropped on the 3rd day the young beer is pumped into the lagering cellar where it is conditioned under pressure in aluminium tanks at 5–6 C. After 6–9 days cold conditioning the beer is pumped through a Massefilter [this is basically filtering through cotton wool as far as I can make out] and from there into the mixing tank together with the sugar solution.

The beer is then pumped through a heater which heats it to 60C into the filling equipment which fills it under counter-pressure into trade casks. These are wooden and treated with sulphur dioxide for sterility.

The draught beer is slightly weaker than the bottled version and free of yeast. It has a very balanced sweet, malty taste with a pleasant bitterness. Despite the very similar brewing method there is a slight difference in flavour between the bottled and draught beers.

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