ly Canadian, speaking at the Norsk Kornøl Festival in Hornindal, Western Norway, last month, revealed that his company had tested 25 different strains from samples of kveik supplied by Garshol, “and all of the ones we tested grew at 40ºC, while two thirds of them were tolerant to 42ºC, which isn’t normal in the larger world of beer: most people are fermenting at 20. This is remarkable. There are prominent yeast scientists that have engineered yeasts to work at 42ºC, and here’s a whole bunch of natural ones from Norway that do it too.
“This means that a home brewer who doesn’t have a lot of equipment, they don’t have a fridge to control the temperature, if it‘s 30ºC in a small city apartment they can still make a clean beer in the summer, and that‘s a little bit revolutionary, because that wasn’t really possible without these yeasts.” There are also, Preiss says, “some real opportunities for using these yeasts elsewhere, such as the ability to make good flavours, good beer at high temperatures. It means that a craft brewery in a tropical climate can maybe reduce their cooling costs and make their beer more energy-efficient.”
How did kveik yeasts evolve to be happy at such high temperatures? Garshol suggests it was due to the pressures the farm brewers were under, which influenced the yeasts they chose to preserve for brewing the next batch of ale: “The fermentation temperatures are crazy. But when you look at the old sources, they say ‘milk-warmÆ pretty much everywhere, in other words around 37ºC. Why is this? Obviously brewers want to add the yeast as quickly as they can. But as the wort cools, it cools more and more slowly. And with old-fashioned cooling methods and 150 litres of wort, that was slow. So there are lots of accounts of brewers having to stay awake until the middle of the night before they can add the yeast. And of course, the longer you wait, the greater the chance that some lactic acid bacteria gets in there. So you really want to ferment warm – the warmer you could ferment, the better.” Those yeasts that survived being thrown into wort at 40ºC to go on and ferment a successful, tasty beer would be the ones that get preserved for use in the future.
The same is true of kveik’s ability to dry out and still come back and thrive when rehydrated. Preiss says that when Escarpment received its initial samples of kveik, “the first thing we found out, and we found it out very quickly, is that this is not normal yeast. We got the dried sample in and rehydrated it, and the cells were looking healthy and plump within five minutes. We put some into some wort, went for lunch and came back 40 minutes later, and it was fermenting. That’s not normal for beer yeast. That was the first sign that this was probably something special.
“We did some fermentation trials of 25 kveik yeasts in comparison with standard Californian ale yeast, WLP001, the commonest yeast in homebrewing, and found they were pretty fast fermenters. Measuring the CO2 release rate 24 hours into the fermentation, some of the kveik yeasts had fermented twice as fast as the California ale yeast, and the majority, 19 out of 25, were outpacing it. This makes sense with what we saw with just rehydrating the yeast: it starts fermenting very fast. This seems to be a fairly common property with the kveik yeasts, and it is fairly unique, this rapid start to the fermentation. Brewers like that – brewers want to know that the fermentation is working. Some of the strains we tested were pretty much finished fermenting within two or three days.”
Again, the explanation for this comes from the pressures the yeast was put under. Norwegian farmhouse brewers did not, and do not, brew regularly: perhaps only two to four times a year. They needed to preserve their yeasts between brewings, and before refrigeration the only way to do this was by drying. Those yeast strains that survived drying were thus selected for. Similarly a farm brewer might have very little notice that a new supply of ale was needed: the arrival of unexpected guests, for example. Once more, those yeasts th