Sunday, 1 March 2015

German brewing in the 1970’s – fermentation (part two)

What’s the best fermentation system? Who hasn’t asked themselves that while soaking in the bath or bobbing along to work on the bus, some grey winters day?

You’re in luck, because Kieninger is going to tell us. Or at least give us his opinion. He worked at Weihenstephan, so he must be right, musn’t he?

“Table XII also shows the most simple and effective method for the fermentation and maturation of lager beers of high quality in the light of modern knowledge. Primary fermentation is carried out in closed vessels, so that it is possible to collect the carbon dioxide and any required temperature may be applied. After reduction of diacetyl the green beer is cooled by plate coolers to a temperature of 0°C and after remaining at this temperature for 2-3 weeks for stabilization it is carbonated and filtered. The only analytical controls required are diacetyl and carbon dioxide and the carbon dioxide content may be controlled by in-line instrumentation.”
Journal of the Institute of Brewing, Volume 83, Issue 1, March-April 1977, page 76.

Lager in just 28 days. I’m not sure he’s convinced me about that. I’m sure it’s a cost-efficient way of brewing. But what about the flavour of the beer? That doesn’t get a look in. Notice that it’s not even taken into consideration.

The best Lagers I’ve had I mostly knew were open-fermented, lagered for months rather than weeks and were naturally carbonated.

I’m going to repeat that table, because it’s a while since the last post in this series:

TABLE XII. Comparison of Fermentation and Maturation Systems.
Method Primary fermentation Transfer Lagering
Classical 7 days at 9°C Beer with 3-5% residual extract cooled to 4°C 35-50 days with temperature reducing from 3° to 0°C
Using Kräusen 7 days at 9º-10°C Beer with 2% residual extract cooled to 4°C. 10-12% Krausen with 8% residual extract added 14-28 days with temperature reducing from 4° to 0°C
Under pressure at high temperature (Champagne Wheat Beer) 3 days at 16°C or 4 days at 14°C under pressure Beer with 2% residual extract 2.0 bar pressure cooled to 0°C 7-14 days stabilization at 0°C 
Modern development 7 days at 12-14°C with CO2 collection Attenuated beer carbonated and cooled to 0°C 14-21 days stabilisation at 0°C and final carbonation

This next bit is interesting, even though it slightly baffles me:

“Fig. 2 illustrates the relationship between the time necessary to reduce diacetyl content to a value of 0.1 mg/litre and maturation temperature. At a temperature of 30°C, 48 hours are sufficient to reduce the diacetyl content to <0.1 mg/litre without addition of Kräusen but, at 8.5°C, eighteen days are necessary to reduce the diacetyl content to the same value. The addition of Kräusen also allows a reduction of diacetyl at higher temperatures, but additional 2-acetolactate is formed during secondary fermentation, so that a new time-consuming reduction phase is necessary.”

Fig. 2. Behaviour of 2-acetolactate (as diacetyl) during different maturation conditions following primary fermentation at 8.5°C. Curve A = maturation at 8.5°C with kräusen, B = 85°C without kräusen, C = 15°C with kräusen, D = 20°C with kräusen, E = 30°C with kräusen, F = 30°C without kräusen.
Journal of the Institute of Brewing, Volume 83, Issue 1, March-April 1977, page 76.

Oh, I get it. You can break down diacetyl at a higher temperature if you kräusen, the fermentation of the kräusen creates more diacetyl. And that also needs to be broken down. Sounds like you need to add more kräusen then. Only joking. But what is he recommending ? I’m confused.

“The development of isoamyl alcohol during primary fermentation at different temperatures with and without pressure is shown in Fig. 3. Isoamyl alcohol content increases

Fig. 3. Iso-amyl alcohol content during primary fermentation in relation to temperature and pressure. Curve A = fermentation at 20ºC, B = 20°C with pressure, C = 16°C, D= 16°C with pressure, E = 12°C. F = 12°C with pressure, G = classical fermentation at 8-S°C.

with increasing temperature but the use of pressure results in a decrease of about 5 % at any given temperature.”
Journal of the Institute of Brewing, Volume 83, Issue 1, March-April 1977, page 77.

This one has totally lost me. Be glad for an explanation by any brewing technicians out there.

Just looked up isoamyl alcohol on this wonderful new thing they have called the internet. A higher alcohol . . . . that tastes like banana. I get why Kieninger is so interested in it, being a brewer of Weissbier.

Still one more bit to go. Where fermentation systems are compared.


Rod said...

He's making it all sound a bit more complicated that it seems on the brewery floor, in my opinion.

A 2 or 3 day rest at slightly above primary fermentation temperature is normally sufficient to deal with diacetyl in practice.

Iso-amylacetate production can be encouraged by using a yeast strain that is prone to producing it (a wheat yeast strain), over-pitching and allowing the fermentation temperature to rise freely after pitching for 24 hours.

Gary Gillman said...

Isoamyl is one of the components of Jack Daniels whisky, the warm, open tank fermentation of the corn mash produces it as a secondary (to ethyl alcohol) constituent of fermentation. Some non weizen ales have it too including some many Belgian ales which favour rather warm ferments. Interesting that pressure seems to fall off in influence as fermenting temperature declines.


jdswainson said...

Hi there, iso-amylacetate is used (at least by germans) as an indicator for the quality of a fermentation. While a banana flavour may be nice in a weizen it's probably not what you're looking for in a helles. That's why this is interesting for a lager brewing country. Brewers can raise fermentation temps, shortening the time needed to reduce the diacetyl, and by adding pressure they can keep the fermentation character subdued.

Love the blog by the way, cheers!