Thursday, 2 January 2020

Fermentation after WW II

In the immediate aftermath of WW II, most breweries still employed open fermenters. Either round or rectangular in shape. By this time they were usually constructed of metal or were at least metal lined.

Fermenters were fitted with attemperators – a series of metal pipes through which cold brine was passed. This was one of the huge innovations of the late 18th-century, allowing brewers to precisely control the fermentation temperature. It led to improved beer quality and the possibility to brew year round.

Many of the older systems of fermentation/cleansing were still in use.

Dropping System
Common in the South of England, in the dropping system two vessels were employed. The wort started fermentation in a tall, round fermenter and after a certain length of time – which could vary between 12 hours and 2 or 3 days, depending on the brewery – was dropped into a lower, shallow, square vessel.

The idea was to remove much of the yeast, which was either left in the upper round or quickly settled out in the lower square. This vessel was often called a “settling square”. The transfer between the two vessels also aerated the wort and reinvigorated the fermentation.

Yorkshire Square
As the name implies, this was popular in Yorkshire, but it was also extensively employed in the Midlands. There was a main square, usually made from slate but sometimes of metal, above which there was a second chamber. The fermenting wort was pumped to the upper chamber and then allowed to drain back down, leaving most of the yeast behind.

As with the dropping system, main purposes were to remove surplus yeast and to aerate the wort. Yeast used to operating in a Yorkshire square often struggles in a standard fermenter due to not being sufficiently roused.

There are still several breweries in the UK that employ this sort of fermenter.

Burton Union
This system was once common across the UK for brewing Pale Ales and wasn’t just limited to Burton. It is not, as people today seem to think, a fermentation vessel, but a cleansing vessel. Fermentation began in a conventional open round or square and the wort was only transferred to a union after a couple of days.

A union set is a series of linked casks. In the bung-hole of each cask there’s a swan-necked pipe through which yeast-laden wort rises and spills into a trough. The trough channels the wort back into the casks leaving the yeast behind. As with the other systems described above, it’s mostly about cleansing, that is removing yeast.

The above is an excerpt from my overly detailed look at post-war UK brewing, Austerity!

Which is now also available in Kindle format.

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