sts 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 that started up quickly, and finished speedily would be optimally selected for.
Rather harder to explain is the alcohol tolerance of kveik strains. According to Preiss, “in terms of alcohol production from the wort, some were pretty efficient, but there was a big range of attenuation, from 66 per cent to 95 per cent, and in alcohol production, from 4.4 per cent to 6.4 per cent.” However, when Escarpment tested for how much alcohol kveik strains could cope with, “we were pretty stunned. We tested eight kveik yeasts for ethanol tolerance, and they were all growing in up to 12 per cent alcohol, which is not normal: conventional ale yeasts exhibit a spectrum, some that are not very good at surviving in high alcohol and some that do survive. It’s very rare to screen eight strains and find all of them growing like that. We found that even if we went up to 16 per cent alcohol, a third of the kveik strains will still grow, which is pretty remarkable.
“We also looked at the flocculation and we found that two thirds were very flocculent, many very, very flocculent. But even in one kveik sample there might be a huge variability in the flocculence between the different yeasts in the strain. Some are not very flocculent at all, some are dropping crystal clear in ten minutes. It’s again interesting to see that kind of variability in a single yeast community.
“We also tested the flavours they produce, using gas chromatography. We picked up a few pretty consistently with the kveik strains, fatty acid esters such as ethyl caproate, giving pineapple flavours, ethyl caprylate, giving pineapple, waxy and cognac flavours, ethyl decanoate, which is red apple, phenethyl acetate, which is floral and honey. Only two of the strains were phenolic, meaning [the rest] were likely picked at some point by humans because they were not phenol-producing, making for a taste that is very typical of ale yeasts, clean but with some fruitiness as well. The isobutenol, or fusel, levels were only around 50 per cent of US-05 [a common American homebrew yea