Tuesday, 17 April 2018

A Modern Lager Brewery - Fermentation

We're looking today at another process very specific to Lager brewing: cold fermentation.

First, the types of fermentation vessels employed in Lager brewing.

"Fermentation.— Fermentation is conducted usually in small oak tuns, the insides of which are either varnished or impregnated with paraffin (the latter being considered by many authorities the better method); this is done to avoid absorption of the beer by the wood and consequent infection. Other materials are making their way for the construction of fermenting vessels; for example, ferro-concrete, lined with a form of asphalt, as constructed by the Swiss firm of Borsari. Again, aluminium in iron casings, with a special insulating mixture between the two metals, has also met with a certain amount of support, but the glass enamelled steel tank appears to be the favourite among those who are not so conservative as to believe that nothing can be as good as the small oak tun. The principal reasons why these glass-lined vessels are making such headway are that the smooth surface favours a somewhat slower fermentation, it conduces also to a better settlement of the yeast (on the bottom of the tun), and a more thorough saturation of the beer with the carbonic acid gas. Further, no periodical scraping and re-varnishing is necessary, while attemperation is also in great measure dispensed with.

Although what is known as the vacuum system of fermentation has met with considerable success in America (where lagers are produced from heavy percentages of substitutes), and, notwithstanding that, it was tried on the Continent, I think that I am correct in saying that it has been practically abandoned in Europe, while the one installation in England did not apparently yield results such as would have justified its further adoption in this country."
Journal of the Institute of Brewing, vol. XVII, 1920, page 494.
It's amazing to think that until a couple of decades ago Pilsner Urquell was fermented in quite small oak tuns. Note that, as was usual on the continent, wooden vessels were lined so that the beer didn't come into direct contact with the timber.

I assume that those glass-lined steel tanks must have been enclosed. Otherwise how could they have increased the amount of CO2 in solution in the beer?

The Pfaudler vaccum system was indeed popular in the USA. I know who used the system in the UK: Allsopp. Though by the time this article was published their Lager brewery had been moved to Alloa. Allsopp, despite a lot of effort and expense, were never able to make a go of Lager brewing.

The need for ice was one of the factors that restricted the spread of Lager brewing until the 1870's, when Van Linde's ice machines made manufactured ice practical. Before then, Lager brewing was mostly limited to Central Europe and Scandinavia where there was plenty of natural ice that could be harvested and stored through the summer.

"As the temperature of fermentation ranges between 40° F. and 50º F., the room or cellar in which it is conducted must obviously stand at not more than the pitching temperature of 40° F. This necessitates either the employment of natural ice or the services of a refrigerating machine; where a plentiful and certain supply of the former can be relied on in the winter; the system is to construct the fermenting and storage cellars round a central ice cellar, provided with suitable air ducts, through which the cold will be transmitted to the various rooms. The ice is collected from the rivers and lakes by means of a combined conveyer and elevator attached to a wagon, and is delivered either direct into the various ice cellars or into a central dump. Obviously, natural ice produces the requisite cold at a much less cost than does refrigerating machinery, but, where any doubt exists as to a regular and ample supply of the natural article being available, then a cooling plant must be installed, if only as a stand-by. Perhaps it is needless to say that, in all lager breweries of any importance, pure yeast is employed exclusively, the pure yeast culture room being as essential a part of such a brewery as the brewhouse. Attemperation is effected in breweries provided with ice machinery by means of flat or tubular attemperators, through which iced water circulates, while, in those depending upon natural ice, floating dishes or cans containing lumps of ice are used."
Journal of the Institute of Brewing, vol. XVII, 1920, page 495.

The system of constructing fermenting and lagering cellars around an ice plant sounds similar to that employed by Carlsberg.

In the UK it was usual to run brine through the attemperators. Floating cans of ice doesn't sound a particularly sophisticated method of cooling.

More on Lager fermentation to come.

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