Kveik is a Norwegian word that refers to a “family yeast.” In the old days, farmhouse brewers in Norway had their own house yeast culture that was used to brew beer for special occasions on their farm. The yeast was passed down from grandmother to grandson. The cultures were often mixed together with cultures from neighbors and sometimes moved to different villages as people moved around. We brew with a number of kveik that we have obtained from farmhouse brewers in Northern Europe. All of our cultures are the original strains, and not purchased from Yeast Labs. We refer to these yeasts as “landrace,” as they are somewhere in the middle of wild and laboratory isolates.
There are several attractions to brewing with kveik. They produce very unique flavors and flavor combinations that are not possible with other yeast cultures. This is the primary reason we use kveik. Other advantages are that they like heat. We’re able to ferment at high temperatures which do not require refrigeration that many yeast strains require in order to produce good beer. In fact, we have small heaters attached to each of our fermenters to maintain a consistent high temperature. This is very unusual for most commercial breweries. The third main attraction to kveik is that they ferment very fast. We are not as concerned about the fast fermentation as we are in making a high quality beer. We let them ferment and rest until we are happy with the beer.
There are some differences that you need to make in your process when brewing with kveik. The two main considerations when making the wort are: final pH and having enough free amino nitrates (FAN) available.
The pH of the wort and finished beer is very important. You need to get to a particular pH range in each step of the brewing process. This is true, regardless of what you use to ferment with. With Kveik, there is one additional consideration that you must factor in, and that is the final wort pH when it is in the fermenter. When you mash your grain and produce your wort, simply boiling and adding hops as normal is likely to produce a wort that has too low of a pH. This can result in a harshly bitter beer. Kveik lower the pH more than other brewing yeasts and this is the cause of the harshness. We test the pH of the wort at the completion of the boil and add buffer minerals to raise the pH to 5.6 before knocking out to the fermenter. The result is a more pleasing bitterness in the finished beer.
When yeast ferment, they consume FAN, among other things. FAN is naturally occurring in malt. In general, the higher the specific gravity (amount of sugar) in the wort, the more FAN you have, but this is not always the case. Kveik require roughly double the amount of FAN as other brewing yeasts, so it is critical that you add nutrients to the wort in order for the kveik to properly do their job. Surprisingly, the best yeast nutrient is actually dead yeast. You can purchase servomyces yeast nutrient, which is a strain of yeast that produces the exact nutrient mixture that yeast need. If you have other beers fermenting, you can simply pull off some yeast slurry from a fermenter and dump that in the boiling wort.
Brewing with kveik can produce some really interesting and unusual beers. Taking these two steps will greatly improve the quality of your kveik beers. Don’t forget to scream when you pitch your kveik, though. Prost!