Fretheim farm, Flåm

If I say "domesticated animals", yeast is perhaps not the first thing that springs to mind, but it was actually one of the first organisms to be domesticated. Evidence of domesticated yeast goes back at least 4000 years. Yeast has been produced commercially since at least the early 19th century, and fairly quickly drove out the private strains that people used to keep at home.

Today, home brewers buy their yeast nearly everywhere. However, in western Norway the traditional yeast lives on in traditional homebrewing. The traditional word for homegrown yeast is "kveik", and not very long ago kveik was found all over the country. Today, very little remains. It exists for certain in Voss, and probably also in Sunnmøre.

Traditionally, bread yeast and beer yeast was the same thing. People would keep yeast from fermentation, and reuse it for baking and later brewing. Many had clear preferences, and would keep only the top yeast or only the bottom yeast, but there seems to be no clear geographic distribution. One farmer would prefer the top, while his neighbour would keep the bottom, and some would do both. Only in Trøndelag does there seem to be a clear preference, in that case for the bottom.

Many different methods for keeping yeast are reported. Bottles were much used, and many stored them in water, such as the well. Some would dry it on straw rings, on linen, or pieces of wood. To make the yeast dry quickly hot ashes were often used. Ashes would absorb water, the heat would contribute to drying, and ash also has the benefit of being sterile.

Kveikstokker (yeast logs)

A traditional piece of equipment is the "yeast log", a wooden pole with holes drilled in it. Many different designs exist, some of them quite ingenious. The log was lowered into the fermentation vessel to catch yeast, then rolled in flour, dried for a few minutes, then dipped again and the process repeated a few times. Finally it would be hung up to dry. The yeast log in the picture below had the year 1621 carved into the bottom.

Kveikstokk (yeast log)

Another method was to mix yeast with flour, and knead it into a kind of flat cake. The cake would then be dried and left until it was time to use it again.

Brewers usually preferred their yeast fresh, and if they didn't have any, would borrow from their neighbours. This was common, and taking payment for yeast was unheard of. Some say well dried yeast could last for more than a year, and, if necessary, it could be revived with sugar and water, then dried again. If mold appeared on the yeast it would be thrown away.

Given how hard it is to keep yeast alive and working well, and how it seems to depend on a community of neighbours all helping one another it's not very surprising that kveik has disappeared in most places. But, as I said, it hasn't disappeared everywhere. Michael Jackson found brewers using kveik in Voss in 1995, and there are still people doing it today. It may exist in Sunnmøre, too.

In fact, a sample from one brewer in Voss was submitted to a British yeast bank in 2009. See numbers 3545 to 3552. It was also analyzed at the yeast bank, and that analysis is interesting in several different ways. For one thing, no sign of bacterial infection was found. The sample was in other words pure yeast, so the brewer must have some degree of control over the yeast quality.

Field, Flåm valley

The researchers wrote that if the yeast had been in use outside a lab for a long time, they would expect it to have diverged genetically into several different closely related strains. And indeed the first analysis found three different strains. A more detailed analysis found another four. All the strains were closely related, with some appearing to be dominant.

DNA sequencing was not done, but the DNA was analyzed with gel electrophoresis and compared with more normal yeast. Analyzed in this way the yeast did not seem "particularly unusual," but the analysis is not nearly as conclusive as full DNA sequencing. No tests have been done on the brewing characteristics of the yeast, so very little is known about that aspect.

One aspect that was unusual was that the yeast produced "moderately well developed pseudomycelia". That is, the yeast cells would cling together in chains. It's not unknown for Saccharomyces to do this, but it is unusual.

Frustratingly, this is where the story ends for now. We know traditional yeast exists. There are indications that it's old and unique, but nothing more is known for certain. Whether it's at all related to the Lithuanian yeast is totally unknown. It's also not clear if anyone is going to do the analysis to find the answers.

Note that it is possible to buy samples of the Norwegian kveik. The prices are fairly stiff, and the procedure around it is not aimed at home brewers, but it is possible to get hold of the yeast if you're sufficiently motivated.

Distant shapes lost in mist, Møre og Romsdal

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