A family tree for kveik

<< 2017-10-06 10:02 >>

Richard Preiss talking about his research at the farmhouse ale festival in Hornindal

In 2016 I was contacted by Canadian researcher Richard Preiss. He wanted to do research on the kveik cultures I had collected, and after a while we agreed to set up a collaboration. Since then I've been sending a part of every farmhouse yeast I collect to Richard, and he has been keeping me up to date on his findings. Since this was ongoing research I haven't revealed his findings, but now a paper by Preiss, Tyrawa, and van der Merwe has been submitted to a journal, and everything is out in the open.

This is research that was mostly done last year, so not that many kveiks were included. They looked at the following:

The ID numbers are taken from my kveik registry, and as you can see quite a few kveiks are not included, because they were collected after the work had begun.

One thing we've found is that all of the yeast cultures contain more than one strain of yeast, except #3 Stranda, and that's probably because the yeast was very nearly dead, and only a single strain survived. The paper lists only one strain from #16 Simonaitis and #4 Muri, but NCYC found several. That there is more than one strain is what you would expect with yeast cultures that have not been purified.

Another surprise is that all of these yeasts, with one exception, are Saccharomyces cerevisiae. That is, ordinary top-fermenting beer/bread yeast. That's quite surprising, because there's no reason why they have to be, yet apparently they are. Except for #4 Muri, which was identified as a hybrid. (We'll return to that.)

However, although kveik turns out to be the same species as top-fermenting beer yeast, it doesn't have to be brewer's yeast. That is, it doesn't have to be yeast that has been domesticated, in the sense that humans have bred it to behave well in beer fermentation. It could still be wild yeast, that is, yeast that's basically still the same kind of yeast you find in nature, fermenting tree sap and fruit. The paper has some interesting light to shed on that question, so let's move on.

#3 Stranda as I got it

The researchers looked at what flavours the kveiks produce, using gas chromatography, and this showed that the only ones that were phenolic (POF+) were #16 Simonaitis and #4 Muri. This is significant because while wild yeast is nearly always POF+, domesticated yeasts tend to be POF- (not phenolic). In other words, this is strong evidence that the kveiks are domesticated and not wild.

The temperature tolerance results are interesting: all the strains can grow at 40C, and most even at 42. It's not in the paper, but Richard Preiss found that the #1 Sigmund could also grow at 43. Of the normal lab yeasts, some couldn't even handle 35, and none could handle more than 40. Of course, the biggest difference is that many of the kveiks produce perfectly fine beer at 40. That result is not in the paper, but from personal experience.

This really sets the kveiks, and the Lithuanian yeast, apart from most other yeasts. I searched the Wyeast catalog and found no yeasts that were recommended for use above 30C. Yet I've had beer made with #1 Sigmund where the fermenter was pinned to 40C with a thermostat, and the resulting beer was clean as a bell.

Richard and the team also tested the yeasts for alcohol tolerance and nearly all handled 13%, and quite a few went as high as 16%. If we compare with the results in the Gallone paper we see that that's quite remarkable for beer yeast. Very likely this is because Norwegian farmers usually made quite strong beer.

Phylogenetic tree of kveik strains from the paper (with annotations added by me)

Now we come to the most telling result: the family tree of kveiks, as well as the Lithuanian yeast and some control yeasts. The genetic analysis finds a clean cut, with the foreign yeasts on one side, and the Norwegian ones on the other. (The red/blue split in the tree.) So the kveiks really look like they are a separate branch on the family tree of yeast. It's too early to conclude that Richard et al have found "Beer 3" (see the Gallone paper), but it's definitely interesting.

However, it doesn't end there. This summer, Richard sent me the tree diagram, saying he thought there were two types, which he was tentatively calling Kveik 1 and Kveik 2. I looked at it for a while and then nearly fell off my chair when I realized that these two groups had a nearly perfect correspondence with the local geography. All the Kveik 1 yeasts (except #3 Stranda) were from the boiled ale area south of the glacier, and all the Kveik 2 yeasts from the raw ale area north of the Jostedalen glacier. See the map here. In the tree above, the black arrow shows the point where Kveik 1 and 2 separate. In the map below the black line shows the glacier (and, at the two ends, mountains) separating the two areas.

Yeast strains on the map

Note that the results are better than the map makes them look, because each dot is more than a single strain. "Stordal" is four strains, for example. In total there's 8 Kveik 2 strains and 13 Kveik 1 strains, and only 1 of those 21 strains is in the "wrong" place. We need more data to be absolutely sure of this, but it's remarkable that the tree follows an already known divide. Richard has later added more yeasts to the tree (not published yet) and the results still hold up. So it's very promising.

At this point it's obvious that we are looking at domesticated yeasts, given that they are POF-, highly alcohol tolerant, have good attenuation, and all seem to be related even though they have been collected from many independent sources. Most of the owners mentioned in the table had never met each other when we collected their yeasts.

So have Norwegian farmers successfully managed to maintain and breed yeast cultures for centuries using basically nothing but wooden rings and sticks? We haven't proved it conclusively, but it sure looks that way. I really would love to see an analysis of when Kveik 1 and Kveik 2 split apart, and when they separated from the other yeasts. We'll have to wait a year or two for those results, though, if we ever get them.

These results repeat the findings from Gallone et al in two respects even if the analysis is of a completely different set of yeasts. Firstly, there seems to be a single ancestor, possibly in the near past. Secondly, geography is mirrored in the family tree. In this case fairly local geography, but still. That has to tell us something about the evolution and spread of yeast among brewers, but I'm still not sure what exactly.

CO2 production in 24 hours (from the paper)

Another finding that's interesting is that compared with the control 19 out of 25 kveiks fermented faster than it. That will surprise nobody who's seen these yeasts take off. They really do ferment astonishingly fast (0-7.5% in 33 hours is completely normal), and what's even more surprising is that you can drink the beer once fermentation is finished, or even before.

Further, they find that the kveiks have good attenuation (65-95%), and that they seem to make good use of maltotriose. Maltotriose is a sugar that appears in wort, but is rare in nature, so wild yeasts are not good at making use of it, but domesticated yeasts are. So this once again confirms that the kveiks are domesticated.

But what about Muri? It stands out a mile among the Norwegian yeasts, since it's a hybrid, it's POF+, and it produces a completely different aroma. So what's up with that? We'll look at that in the next posting.

Appendix

Earlier I wrote about another study which found several that kveik seemed to be several different species. The reason for that result seems to be that they used the ITS region of the genome to identify the species, and in this part of the genome the difference between Saccharomyces cerevisiae and Saccharomyces boulardii is just a single base pair. So it takes just a tiny mistake to put the yeast in the wrong species. That accounts for nearly all the differences between the earlier paper and this one, except for #6 Lærdal, and some Lithuanian ones that were not in this paper.

Some of the Lithuanian yeasts really are non-Saccharomyces, but since I don't have permission from the owners to do research on them I didn't send them to Richard. The results from this paper are based on more data, and so seem more likely to be the correct ones. The results in this paper also match the conclusions that NCYC came to, which is another reason to believe that this is the correct answer.

Unlike the Gallone paper this paper did not sequence the entire genome of the strains. So the genetic results in this paper are a bit more uncertain. The researchers have now gotten funding to sequence the whole genome of some strains, so more results will be forthcoming.

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