Kveik is a collective term for a family of strains of brewing yeast that has been used in Norwegian farmhouse brewing for generations. Genetic analysis shows that kveik belongs to the large category of brewing yeast called "Beer 1", which includes much of the yeast strains from Germany, Belgium, Great Britain, and the USA. Kveik seems to be a hybrid of a progenitor from this known family in addition to an unknown yeast, most likely a wild yeast. Although kveik is a domesticated brewer's yeast it differs from most modern brewer's yeast in several ways: It can ferment at much higher temperatures without causing off-flavors. Ordinary brewer's yeast will usually produce off-flavors above 25C (77F), but kveik can go as high as 43C (109F) without ill effects. It completes fermentation of the beer faster than other yeasts, and the beer can be drunk earlier with less time to mature. It can be dried and stored dry. It produces other aromas, often reminiscent of tropical fruits. Chemically it produces more fatty esters than ordinary yeast.
