Sunday, 7 September 2008

Yeast circa 1900

Another short post today. I have to go to the cinema with the kids in 10 minutes. Star Wars Clone Wars is what we're going to see. Exactly the sort of intellectual stimulation I need on a Sunday morning.

Brettanomyces Stock Ale was a strong Beer which was matured for many months or years and then blended with young beers or ales to give them the aged flavour. It was called Stock because a stock of it was kept in the brewery. It was rarely sold just by itself (I've only found a product called Stock Ale or Beer a couple of times in old brewery price lists).

The "aged" taste, as was discoverd when it was isolated in 1903 by the Dane Niels Hjelte Claussen (who worked at the Carlsberg brewery in Copenhagen), came from the action of Brettanomyces. Experiments in Britain the early 1900's showed that when a finished pasteurised beer was innoculated with Brettanomyces it acquired the typical aged taste within 10 to 14 days. The application of this technique would have made the production of Stock Beers much quicker and more reliable. Except that the demand for such beers had all but evaporated by the start of the 20th century.

Pure Yeast Cultures
In "Brewing Science and Practice: Volume II Brewing Processes" (H. Lloyd Hind, London, 1940, pages 800-802) there's another interesting passage about Hansens work with single-cell yeast strains. It discusses experiments at the Worthington brewery in Burton in the 1880's brewing beer with pure strains. The conclusion was that pure strains did not produce better than mixed strains and in fact had some disadvanatges during secondary fermentation, such as conditioning more slowly in the cask and producing beers which did not age well. It was not recommened for use in beers that were to be kept more than 6 weeks after racking. It says that at the time (1940) only a handful of British brewers used pure strains.


Oblivious said...

It would be interesting to know if the pure stains of yeast where grown up in a simple sugar medium or wort?

Anonymous said...

According to the book by Hansen's assistant, Albert Klöcker (the English translation of which is entitled "Fermentation Organisms," from 1902), his experiments were performed in a variety of media: wort, fruit syrups, meat extract, dextrose solutions, and a variety of solid media.

Earlier this year I made a crude attempt to isolate some wild saccharomyces and brettanomyces species from my local environs (West coast North America), and have been brewing (noncommercially) with them for a few months now.

That book in its entirety is available on Google books.

Oblivious said...

Hi mark oliver

Interesting, it’s just that yeast need the selective pressure of maltose to keep expressing the enzymes to metabolise the wort. If the yeast was grown up on a medium of simple sugars I wonder could this in part explain their observations with pure culture yeast.