Tuesday, 3 March 2015

German brewing in the 1970’s – fermentation vessels

Kieninger ends with an overview of the different German fermentation systems in use at the time.

It’s pretty clear where his preferences lie. Again there’s not a single mention of beer flavour in his discussion.

“Finally, I wish to discuss the types of fermentation vessels which may be used in breweries in the future. There are three main combinations of fermentation and maturation vessels in use at present.

(a) The green beer may be fermented in cylindro-conical vessels and then matured in horizontal tanks. This method has the disadvantage that the yeast must be removed from the lager tank manually and is likely to be avoided in future developments.”
Journal of the Institute of Brewing, Volume 83, Issue 1, March-April 1977, page 77.

Even in the most old-fashioned method he describes the primary fermentation is performed in conicals. He only really traditional bit is lagering in horizontal tanks. His dislike of them seems purely based on having to clean them out by hand.

This sounds even worse:

“(b) A second possibility is to use cylindro-conical vessels for main fermentation and then to pump the beer into vertical outdoor tanks, using a plate cooler to lower the temperature.

The removal of yeast from the outdoor tank is also difficult, especially if the vessel has a diameter greater than 6 m. The vessels are cheap, however, and as a result they are found in many breweries, usually with centrifuges before the plate cooler.”
Journal of the Institute of Brewing, Volume 83, Issue 1, March-April 1977, page 77.

It’s huge tanks like these that make some modern breweries look like a chemical works. Or some post-modernist building where all the guts are on the outside.

Finally, Kieninger’s favourite:

“(c) The problems of handling yeast in large tanks has led to a consideration of fermentation and maturation in a single vessel. One brewery in Italy uses this so-called 'unitank method". This brewery is not using flotation but filters the wort before fermentation by use of a kteselguhr filter. The primary fermentation is completed after 7 days at a temperature of 9°C, 7 days are needed to reduce the content of the a-acetolactate formed and after a further 7 days stabilization at 0°C the beer is filtered and bottled. The average yeast concentration before filtration is 4 million cells per ml compared to a concentration of only 0.5 million cells per ml for the classical procedure of stabilization in horizontal cylindrical vessels. Since one brew occupies a vessel for 3 weeks one must ask if the financial burden which arises from the high costs of cylindro-conical tanks compared to separate fermentation and lagering vessels is justified. The fact that removal of yeast from the cylindro-conical tanks is much easier than from horizontal or vertical lager tanks with a flat bottom is a major reason for the method being adopted.

Extensive trials in our Institute showed that fermentation at temperatures of 15-18°C altered the original character of the lager beer, even after addition of Krausen during secondary fermentation and only at temperatures of 12°C and below was no distinct effect found. We think it advisable, therefore, that the temperature of primary fermentation should not exceed 9°C during the first 3 days but during the last stages of primary fermentation the temperatures may rise to 14-I6°C to reduce the content of diketones and precursors. After this time the yeast is removed and the beer is carbonated and stabilized at 0°C in the same vessel. The procedure described requires 3 weeks production time which can be carried out on a weekly programme. A better foam stability has been found with longer maturation time.”
Journal of the Institute of Brewing, Volume 83, Issue 1, March-April 1977, page 77.

I believe the unitank system is what industrial Lager breweries use today. And I think the temperature of primary fermentation isn’t kept below 9º C, but is more like the 15-18°C than damages the character of Lager. Oh look, there’s a sort of mention of beer flavour. At just three weeks from mash to bottling, there’s not really any lagering going on.

Kieninger does have reservations about conicals:

“Summarizing these points the question arises whether the cylindro-conical tank can really be the universal vessel for beer production in the future. It is certainly possible to separate the cold break by filling the vessels at such a speed that the sludge sediments before the yeast has overcome its 8 hour lag-phase. This allows sufficient separation of cold sludge for the fermentative activity of the yeast not to be affected. Collection of carbon dioxide and removal of yeast is possible without manual work and there are no problems with stabilization and carbonation. The only disadvantage is the larger volume required for the foam head when using higher temperatures. Our experience has shown that a vessel with a height of 25 m needs 5-6 m for the foam head and this means that a vessel, depending on the temperature of fermentation, may be filled only to two-thirds of its volume. It seems that in the future, therefore, there will be a trend in many continental breweries to ferment and mature the beer in one vessel by a batch procedure.”
Journal of the Institute of Brewing, Volume 83, Issue 1, March-April 1977, page 77.

Though the ease of removing yeast and collecting CO2 outweigh not being able to fill the conicals to the top when fermenting Lager warmer than was traditional.

His prediction about single-vessel fermentation systems did indeed become true. In fact I think that’s also the way most new small breweries operate in the US.

And that's us done. At least with this article.


Barm said...

Another advantage of unitanks is that you don’t have to chill the entire lagering room. Which to me was the most fun bit of visiting a lager brewery. Yeah, I'm weird.

Gary Gillman said...

The development of the unitank/CC is one of those landmark moments in brewing technology history. It's akin in importance to the systematic aging in the 1700's of London Porter or development of pure culture yeasts. Yet it's a story little known, relatively. Few technological innovations have endured as long as the CC tank, it's lasted almost 100 years now with no sign of abating.

It started with the Cascade and other breweries in Australia (1920's-30's) and then elsewhere outside Europe but only really took off when Whitbread installed these tanks in the 1960's. By then, metals could be used which were cost-effective and easy to clean in place.

The real question for the consumer beer fan though is impact on flavour, especially for top-fermented beers. (But also bottom-fermented ones especially as regards the need to wash out sulphur and other green flavours). Here, the story needs to be explicated, IMO. There has been speculation some of the Belgian breweries which switched to CCs don't get the same complexity. It is very hard to say though over the long period over which these changes occur.

I believe Sierra Nevada Pale Ale is made today in CCs and yet to me it tastes the same as it always did. So...


Rod said...

Barm -

modern flat bottomed maturation vessels have cooling jackets too, so no need to chill the lagering hall anyway.