Saturday, 24 May 2014

The Pfaudler vacuum system

Not sure why I never posted this before. I'd used the rest of the article discussing American brewing.

Maybe because this section is about Lager, though it does have a British connection. In fact it's connected to a couple of my obsessions.

First, confirmation that American brewers didn't decoct their Lagers:

"Although the manufacture of lager beer must necessarily be of less interest to the English brewer than that of the high fermentation ale, I may perhaps be permitted to call your attention to a few modifications -which the Americans, with their accustomed originality, have introduced into the time-honoured continental methods. In the first place, one is struck by the almost complete abandonment of the decoction mash. Nearly all the lager in America is brewed by the infusion process, either as we know it, or by a system of gradual elevation of temperature in the mash-tun. The boiling of the "thick mash" is practically unknown.

The method of fermentation of lager, as generally adopted, differs but very little from that of continental breweries. The primary fermentation is carried on at from 40° to 41° F., and lasts from 14 to 20 days. The beer is then passed on to tall vats, which are known as the ruh casks, and here it remains from one to four months. It is then run into the "chips-casks," where it is at once kräusened with fermenting wort, to the extent of from 15 to 20 per cent., and bunged down tight. Finings are sometimes added at this stage, and when the beer is nearly brilliant it is passed through a Stockheim or Enzinger filter, and racked into the trade casks. The primary and complementary fermentations together last from 2 to 5 months, so that the space and plant required for a brewery doing a good trade are very considerable, and of course the working capital is correspondingly large."
Journal of the Federated Institutes of Brewing, Volume 3, Issue 6, November-December 1897, page 475.
That's very much the classic method of fermenting Lager: a slow, cool primary fermentation, a long lagering,  kräusening and bunging to carbonate the beer. Though I'm not sure Continental breweries would have used finings. Two  to five months is a pretty decent lagering time. Interesting that the use the German word "ruh", meaning rest. And, like Budweiser, they were adding wood chips to the lagering vessels.

Obviously that was an expensive and time-consuming process. No surprise that there were attempts to shorten and simplify it.

"An attempt has been made within the last few years to materially lessen the time required for the complete fermentation of lager, and thus to reduce its cost of production.

The process is known as the "F. F." or Pfaudler vacuum system, and as it is one which is attracting a good deal of attention in America and elsewhere at the present time, it will doubtless be of some interest to you to hear something about it.
. . . . .

Briefly stated, the principle of the process depends on three conditions:—(1) The temperature of fermentation is much higher than that-usually employed in lager beer brewing; (2) there is a certain amount of aeration during the process which admits of strict regulation; and (3) the fermentation is carried on under low pressure conditions which admit of the carbonic acid being removed as fast as it is produced. Under these three combined influences the fermentation runs through a very rapid course, and the beer is ready for the chips-casks in from 10 to 11 days. If the process of krausening in the chips-casks is adopted the beer is ready for racking in about three weeks from the time of brewing, a time which may be further reduced to 11 or 12 days if the chips-cask stage is avoided by carbonating the beers."
Journal of the Federated Institutes of Brewing, Volume 3, Issue 6, November-December 1897, pages 475 - 476.
Remember where we've heard of the Pfaudler vacuum system before? It's the system that Allsopp installed in Burton in 1899 when they decided they wanted to brew Lager. And which was taken by Calder up to Alloa.

It's nice to learn exactly what the Pfaudler vacuum system was.

"The following is a brief description of the vacuum process of fermentation :—

The worts are first run into "starting tubs" at about 50—51° F., and the yeast is added at the rate of about 1 lb. per barrel. After 24 hours it is transferred to the vacuum vessels, which are large cylinders, built up of steel sections, rivetted together and coated inside with a special enamel which is burnt on to the cylinders. The bottoms of these cylinders are conical, and they resemble somewhat in general appearance very large pure-yeast cultivators.

The top of the cylinder is closed, and arrangements are made for pumping out the carbonic acid and for reducing the pressure in the apparatus to any desired extent by means of an air-pump. The carbon dioxide can, if desired, be collected and liquefied by pressure in ordinary gas cylinders, and then used directly for carbonating the ale when it is finished. There is an air inlet in the conical bottom, connected inside with a perforated loop of pipe, through which air (previously well filtered through cotton wool) can be passed into the fermenting wort. This air passes through a "sight feeder" on its way to the vacuum vessel, so that the amount which passes can be easily regulated.

During this part of the process the temperature is not allowed to exceed about 49° F., by means of an attemperator in the vacuum vessel, and the fermentation is complete in from five to seven days. The Phoenix Brewery at Pittsburg has 26 of these vacuum vessels, each holding 110 American barrels, and they are sufficient for turning out 100,000 barrels per annum."

After the primary fermentation is over, the beer is of course in an extremely flat state, and is either passed on to chips-casks and kräusened, or is at once filtered and carbonated before being put into the trade casks.
Journal of the Federated Institutes of Brewing, Volume 3, Issue 6, November-December 1897, pages 476 - 477.
So the primary fermentation was around 10º F warmer and one or two weeks quicker than the classic Lager method. I can see how that would save a brewery dosh. It sounds like minimal lagering was taking place. Which would have been an even bigger economy.

The vessels themselves, apart from the vacuum bit, sound very much like conical fermenters. Though much smaller than modern conicals usually are.

The system was quicker, but did the finished beer taste as good as that produced by the classic method?

"The Pfaudler vacuum system is certainly able to produce a lager beer much more rapidly than the old system, but what proportion of capital outlay in required to construct a brewery of given out-turn on the old and the new system respectively I am not at present in a position to say. Assuming, however, that the balance, as regards initial cost, is in favour of the new system, and that the much more rapid turnover is taken into account, the final verdict must after all turn on the relative quality of the beer produced by the two processes. That a perfectly sound and saleable article can be produced by the vacuum system is an undeniable fact, but whether the longer storage and maturation of the beer brewed on the old system does not produce certain high class qualities which are lacking in the more quickly made and loss matured vacuum beers can only be determined by a lengthy trial and by the competition of trade, which can alone decide which of the two is the fitter for survival. At present I hold my judgment on this question in suspense."
Journal of the Federated Institutes of Brewing, Volume 3, Issue 6, November-December 1897, page 478.

I take that as a definite maybe. My personal experience tells me that a couple of months lagering definitely improves a beer. If it didn't why would anyone still bother?

1 comment:

Jeff Renner said...

A little late to the dance on this.

"one is struck by the almost complete abandon ment of the decoction mash. Nearly all the lager in America is brewed by the infusion process, either as we know it, or by a system of gradual elevation of temperature in the mash-tun."

True enough, but if the brewer was using raw maize or rice, a decoction of sorts, the American double mash, was used. A small portion of the malt was added to the raw cereal, rested at mash temperature (~67C) for a short time, boiled (like a decoction), and then added to the main mash, which boosted the mash temperature much like returning a decocted portion of an all malt mash.

The mash was typically started at 40ºC, boosted to 50C and then 60C with steam infusion or direct heat, then the cereal mash was added, which would boost it to 70C or so.

This is described in Wahl and Henius' "American Handy Book of Brewing" starting at p. 730.