Fermentation is still the topic, though we’re moving from the traditional to the innovative. Or is that from good to bad? Obviously all that messing around in lager cellars was time-consuming and expensive. Reason enough for some to looking for a quicker and cheaper method.
“Newer methods of fermentation.—The so-called pressure fermentation had its origin in the production of champagne wheat beer with bottom or top fermentation, where it has been used for 35 years with the best of results. Before the pressure fermentation starts the wort must be cleared of trub. Then follows, with a bottom yeast, a short fermentation (24 hr.) at approximately 15° C, before the wort is pumped to a pressure tank at 17-18° C. This tank should only be filled to two-thirds of its capacity. The fermentation carries on for approximately 4 days to an attenuation degree of 63-67% with all valves open; subsequently this temperature is maintained, the valves are closed and a pressure of 2 atm. is reached. When the beer has been fermented almost to the final attenuation the tanks are cooled, either by jacket coolers or by internal coolers to 12° C, in order to cause the yeast to settle; this takes 1-2 days.
After a settling period, the beer is pumped to a further tank, as a result of which most of the yeast is removed; it is then cooled in several stages to below freezing point. At the same time, the pressure is dropped at intervals to the pressure corresponding with the required CO2 content. This period lasts for 10 to 14 days. The escaping CO2 produces a certain maturation and induces increases in colloid particles as well as in protein deposit.”
Journal of the Institute of Brewing, Volume 72, Issue 1, January-February 1966, page 21.
Surely bottom-fermenting a wheat beer was a no-no under the Reinheitsgebot. By “champagne wheat beer” I’m pretty sure they mean Kristalweizen, or filtered wheat beer. I seems a weird mixture of open and closed fermentation. I’m quite confused by this knowing that today Weissbier is commonly open fermented, even at large producers like Schneider.
The cooling and pressurising process sounds very much like classic lagering, albeit considerably shorter at a maximum of two weeks.
35 years puts the origin of this method back in the early 1930’s. Which I find surprisingly early. The implication is that the technique was developed for Kristalweizen then applied to other types.
It did have some disadvantages:
“Beers produced with this method have a good head and if intensive cooling has been combined with good fermentation they also have good chill stability. Severe variations in output can result in over-aged beer or in insufficient brightness, which makes filter work more difficult.
Poor flavour can result if too much yeast is put into the maturing tank or if the required pressure is not reached or the maturing time is too short or much too long. The yeast should also be examined with regard to its ability to produce by-products of fermentation such as higher alcohols, volatile acids and esters. Our results show that the various yeasts differ clearly in this respect.
A yeast used during warm fermentation can only be used for a limited period; thereafter a fresh yeast from the conventional cold brewery must be obtained."
Journal of the Institute of Brewing, Volume 72, Issue 1, January-February 1966, page 21.
OK, it had a nice head but tasted shit. Or at least did if conditions weren’t optimal. Clearly then yeast wasn’t too happy with this treatment as it couldn’t operate for long under these conditions.
But there was a way around these problems: blending.
“As a result of experience to date, it appears to be essential to blend beers fermented according to the conventional system with beers from the quick maturing system. By this means the output of "cold" fermented beer can be kept constant and the output of other beers can be varied. At the same time, this blending system prevents excessive ageing of beers when output stoppages occur. If pressure tanks are not available then a CO2 rinsing or washing system can have the same effect. In Germany, CO2 from the actual beer fermentation is the only type that can be used.
Journal of the Institute of Brewing, Volume 72, Issue 1, January-February 1966, page 21.
That sounds a right pain in the arse. Because beer from a pressure fermentation couldn’t be left long in the brewery you also need to have beer that could. That is, beer produced the old-fashioned way. And you needed to have two sets of fermentation equipment to produce the two types of beer. Sounds expensive in terms of plant.
Only allowing CO2 produced during a fermentation to be used for artificial carbonation is one of the quirks of the Reinheitsgebot.
“A second method is more complicated. It depends, however, on the existing processes. By increasing the temperature in the fermentation cellar, final attenuation is reached and the yeast is removed by means of a green-beer centrifuge. This yeast-free beer can now be cooled by means of a heat exchanger unit to 4° C. without endangering the yeast. Subsequently it can be pitched with non-flocculating yeast. As the warm fermenter beer contains only small amounts of CO2, the non-flocculating yeast must provide CO2 saturation in 10-14 days, whilst at the same time the beer is cooled to less than 0° C. The combination of the easily fermentable "Krausen" extract with the intensively fermenting yeast completes this process. The resulting beer is well matured and, according to existing observations, good protein stability is obtained.”
Journal of the Institute of Brewing, Volume 72, Issue 1, January-February 1966, page 21.
Let’s get this straight. The beer is fully attenuated during a warm primary fermentation and the yeast removed. It’s then cooled and repitched to carbonate the beer. It sounds like this was all done with the classic fermentation and lagering equipment.
“Beers brewed according to this method have a satisfactory and stable flavour. It is, nevertheless, necessary to reduce the high pressure in the green-beer centrifuge as otherwise severe aeration of the beer occurs, resulting in a detrimental flavour due to diacetyl and other factors. Kieninger has suggested a modified quick-maturing method in which green beer is centrifuged with a low back pressure and cooled to 0° C. before or after centrifuging. By means of corresponding pressure regulation it is possible to introduce CO2 in excess into the centrifuge and the subsequent rest period is utilized for releasing the C02 at intervals, so that the action of the C02 on the large surface area produces a maturing of the beer. This method is still experimental but experiments to date have been giving encouraging results.
These methods have made it possible to produce a satisfactory beer in 10-20 days from the date of brewing by modifications of the existing fermenting and maturing methods.”
Journal of the Institute of Brewing, Volume 72, Issue 1, January-February 1966, pages 21 - 22.
The difference between this and the preceding method appears to be artificial carbonation rather than a secondary fermentation with new yeast.
The time taken to produce beer was about halved using this method. Remember the classic method entailed a least a week in primary and four weeks lagering – 35 days in total.
Filtration next time. That sounds like fun.
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3 comments:
"35 years puts the origin of this method back in the early 1930’s. Which I find surprisingly early. The implication is that the technique was developed for Kristalweizen then applied to other types."
My thought exactly, Ron. Both for pressure fermentation itself, and for Krystalweizen (which I thought was developed much later than the 30's to appeal the people outside Southern Bavaria who didn't want to drink cloudy beer).
Something else seems a bit odd too. One of the things that pressure fermentation does is allow faster/warmer fermentation without the production of esters and phenols - however, when you brew Bavarian-style Weizen, esters are just what you actually want, as this is where the fruity, spicy flavours come from. A standard procedure in German breweries is to over-pitch the yeast and allow fermentation temperature to rise freely for 24 hours, precisely to encourage ester formation.
It seems odd to come up with a different method of fermentation (involving costly additional equipment) just for Krystalweizen, for which there has always been a very limited market anyway.
Weizen isn't a beer that needs as much maturation time as say Pils anyway, in my personal opinion.
Rod,
I think with Kristalweizen they might well have been trying to avoid those flavours. I remember them as being pretty bland - not a patch on the Hefe version.
I've some more stuff on this form of fermentation. Which I'll write about sometime.
So much material, so little time.
"I think with Kristalweizen they might well have been trying to avoid those flavours"
You're right they were bland! However, if you don't want the ester flavours, why not just substitute a neutral yeast and ferment a bit colder?
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