Kveik

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Kveik Ring (gjærkran). Photo by Lars Marius Garshol.
Diagram of types of yeast versus traditional farmhouse styles by Richard Preiss [1].

Kveik (click here for pronunciation) is a dialect word for "yeast" in Norwegian ("gjær" is the common word for "yeast" in Norwegian [2]), and today specifically refers to non-purified yeast that has been reused for generations in traditional Norwegian farmhouse brewing. The term "kveik" does not refer to a style of beer, but only the yeast used in traditional Norwegian farmhouse brewing (Garshol has encouraged brewers brewing non-farmhouse styles with kveik to call them "X Style Beer Brewed with Kveik" or something similar [3]). The word "kveik" is specifically used in the western part of Norway for family-owned, non-purified yeast, while other words such as "gjester" are used by central Norwegians, "gong" is used by locals in eastern Norway, "family yeast" is used by some Lithuanian brewers, and "hemjäst" is used by locals in Gotland. The term "landrace yeast" has been proposed to refer to kveik as well as other non-kveik farmhouse yeast cultures (for example, Simonaitis) [4][1][3]. Kveik yeast are extremely diverse genetically, presenting characteristics that are not typical in other brewing yeasts [5]. Most farmhouse brewers have started buying their yeast, but some kveik cultures have been passed down from generations and inherited by modern farmhouse brewers in Norway who still use this yeast today and brew with traditional farmhouse methods. Much of the knowledge about kveik and historical farmhouse brewing in Norway has been researched and publicized by Lars Marius Garshol on his blog, Larsblog, and in the book Beer and Brewing Traditions in Norway by Odd Nordland (1969). In recent years kveik cultures have been sent to yeast labs for propagation and distribution to brewers around the world [6]. The use of kveik is one of the many traditional methods still used by a few farmhouse brewers and homebrewers in Norway, along with other historical methods such as infusing the mash or boil with juniper (Juniperus communis [7]), not filtering, using short fermentations to achieve low carbonation, the use of wood-fired copper or iron kettles, and sometimes not boiling the wort (Raw Ale) [8].

Farmhouse yeasts from other countries such as Lithuania and Russia have been found to be both genetically different and express different fermentation profiles than the kveik yeasts of Norway, and are therefore not referred to as "kveik". See the Farmhouse Yeasts in Other Countries section below.

For another comprehensive list of kveik and other landrace farmhouse yeasts, see also the Farmhouse Yeast Registry maintained by Lars Garshol.

"I see this is about to become a myth, so just to clear things up: kveik is not a style of beer. It's farmhouse yeast." ~ Lars Marius Garshol, December 29, 2016 [3]

Brief History and Description of Kveik

Brief History

Kveik was passed down from generation to generation within the family, and also shared among fellow brewers in the region. In this way, kveik evolved differently than the two major beer yeast genetic groups that are used in industrialized brewing. While mostly POF-, a trait that is selected for in many beer yeast strains that prevents the yeast from producing 4-vinylguaiacol phenol, other traits are reflective of how this yeast was used by traditional farmhouse brewers of the region. For example, as far back as 1621 (and probably prior), kveik was often stored dry on wooden logs called "kveikstokker" for up to a year or longer. Kveik was typically inoculated directly into the wort by submerging the kveikstokker into the wort at 30-40°C. The wort was often high gravity of around 1.080 SG, and the beer was served just after 1-2 days of fermentation beginning at this hot inoculation temperature. The kveik was then taken from the fermenter and dried until its next use. If the kveik went sour or died, brewers would borrow kveik from their neighbors, which was another way of preserving kveik through the centuries. Kveik was sometimes also used to ferment bread. It has been proposed by Preiss et al. (2018) that this treatment has produced yeast strains that are genetically distinct phenotypically from other domesticated yeast strains used in industrial brewing in Europe [9].

Farmers seemed to have different preferences for top or bottom collecting their kveik for storage [6]. Kveik was stored in many ways. It was often stored in bottles with water or in a well. It was also dried on straw rings, on linen, or pieces of wood with holes drilled through them called "yeast logs". Often ashes were used to help dry the kveik quickly, or in the case of yeast logs, were lowered into the fermentation vessel to collect the yeast and then rolled in flour and allowed to dry for a few minutes, then dipped again to repeat the process. The log was then hung to dry. Although dried kveik was said to last for months or maybe longer, fresh kveik was always preferred and often given away to those who needed new kveik (moldy kveik was thrown away) [6].

At one time kveik was the only available form of yeast in Norway (and, of course, similar methods for reusing yeast were used all over the world prior to Emil Chr. Hansen's introduction of the pure-yeast system in 1883). However, the existence of kveik has mostly disappeared in recent times. Today kveik remains in the districts of Hardanger, Voss, Sogn, Nordfjord, and Sunnmøre, at least. Kveik is only used by homebrewers who still brew in the traditional methods of Norwegian farmhouse brewing, although the recent spreading of kveik throughout the world has led to a resurgence in its usage to make various types of beer, including non-farmhouse style beers [10].

Terminology

Sensory and Fermentation Profile

Kveik is not a single type of yeast. In fact, very likely the different kveik cultures don't even belong to the same species. So the term "kveik" means "ancestral non-lab yeast" rather than any specific strain of yeast or any specific characteristic of the yeast itself. Further, only a small fraction of the kveik cultures that exist have been sampled so far, so what is described here applies only to the cultures explored so far. The ones that still exist only "in the wild" may not fit this description.

The general flavor profile of kveik yeast is ester-driven, although a wide range of differences exist between strains. Kveik in its traditional form is usually a blend of closely related strains. The "Stranda" kveik was described as "lemon, nuts, grain, and straw" by Lars Marius Garshol. The "Hornindal kveik" with bacteria was described as "fruity, milky caramel, honey, and mushroom with a very unique aroma". The "Muri kveik" was described as "earthy on the nose, and fruity tasting with hints of rubber and sulfur and a thinner mouthfeel than the others" [12].

Omega Yeast Labs describes their two isolates as being non-phenolic and fruity, and complimenting of American citrus hops. They also note that the yeast has a very high temperature range (~68-98°F or ~20-37°C), attenuates high, tends to flocculate well, and also tends to ferment faster at the mid to high temperature ranges, while producing similar ester profiles throughout the entire temperature range.

Richard Preiss from Escarpment Laboratories shared his sensory notes after doing trial fermentations with various kveik strains/cultures. Fermentations were at 30°C in standard wort (1.050, 20IBU) with single strains, not the mixed cultures. 2/3 tasters were blind to the beers and order prior to tasting. This is a single data point on sensory information [13]:

  • Sykkylven 1 - clean, fruity, malty, rum-like. big, round, malty, slightly hot
  • Sykkylven 2 - subtle fruit, malt accented, slightly lagery-sulfury, lightly floral. medium body
  • Laerdal 2 (Laerdal 1 - data not available) - Lightly fruity, slight rubber, floral, sweet taste
  • Stranda 1 - citrus, red apple, very clean and dry, balanced
  • Stordal (framgarden) 1 - big citrus ester, slightly hot, red apple, floral, malty
  • Stordal (framgarden) 2 - red apple, slight crisp/sulfury (pleasant) lagery character, floral, slight tropical fruit, slight tartness
  • Stordal (ebbegarden) 1 - rum-like, slightly hot, medium mixed esters, round and malty
  • Stordal (ebbegarden) 2 - Christmasy, citrus, red apple, floral, clean and balanced flavour
  • Muri 1 - Earthy, herbal, sulfury, apple, pear, very slight clove, not super dry despite ridiculous attenuation (~95%)
  • Voss (Gjernes) 1 - Orange, floral, balanced flavour, good body
  • Voss (Gjernes) 2 - Cidery, floral, slight earthiness, slight orange, clean, dry
  • Hornidal 1 - Tropical, pineapple, rum-like, caramel, citrus, balanced malt/hop
  • Hornidal 2 - Floral, rose-like, sulfury, orange, rum-like, very malt accented
  • Hornidal 3 - Orange, red apple, rum-like, caramel, balanced
  • Granvin 1 - Lower intensity orange, red apple, slight pineapple, textbook “Kveiky”, balanced
  • Granvin 2 - Balanced esters, not as intense - citrus, slight (pleasant) sulfur, dry and thin
  • Granvin 3 - very muted aroma, clean flavour
  • Granvin 4 - floral (rose), honey, slight diacetyl, medium-low esters, complex but not necessarily good
  • Granvin 5 - light fruit, light floral, rubber, sweet taste.
  • Granvin 6 - fruity, floral, rum-like, citrus, slight diacetyl, balanced flavour
  • Granvin 7 - Slight fruity, very thin and astringent
  • WLP001 (control) - very fusely/hot, subtle floral note.

Note regarding Granvin strains: Preiss is still trying to sort out which Granvin yeasts are duplicates and which are unique.

See also:

Lactic Acid Bacteria Contaminations

Some of the kveik cultures that are not isolated cultures have reportedly been contaminated with lactic acid bacteria. These contaminations probably occurred during handling of the yeast at some point. See Justin Amaral's statements regarding this issue. The lactic acid bacteria found in contaminated kveik cultures can be inhibited by ~10 IBU [14].

See also:

Recent Yeast Lab Analysis and Commercial Availability

The dried kveik samples (Stordal) showed much better viability/cell health (less granulated/wrinkly appearance) than the liquid samples (eg Hornidal). However, some of the liquid samples were pretty healthy too (Voss). Source Richard Preiss of Escarpment Labs.

Thanks to efforts by Lars Marius Garshol and Håken Hveem, and Norwegian farmhouse brewers Svein Rivenes, Sigmund Gjernes, Bjarne Muri, Terje Raftevold, and others, kveik has been made commercially available to brewers around the world. Much of the analysis has been performed by the National Collection of Yeast Cultures (NCYC). See also the Kveik Registry being maintained by Lars Marius Garshol.

Analysis has also been performed at the Norwegian University of Science and Technology (NTNU) by Truls C Rasmussen, as well as Escarpment Laboratories.

In general, most of the cultures of kveik that have been analyzed contain more than one strain of S. cerevisiae, which was the only species in all of the kveik cultures analyzed by Preiss et al. (2018) except for the Muri kveik. The Muri kveik contains a single isolate of what appears to be a domestic (human produced) hybrid between S. cerevisiae, S. eubayanus, and S. uvarum. Of the 9 kveik cultures analyzed by Preiss et al. (2018), only Muri, Simonaitis, and Stranda contained only one strain of S. cerevisiae, while all of the others contained more than one strain of S. cerevisiae up to 9 strains in the case of Granvin (see this table from the paper). Genetically, kveik yeast strains form their own group of closely related domesticated ale strains that are a subgroup of the "Beer 1" yeasts (Belgian/Germany/UK/US yeast strains) from the Gillons/White Labs (2016) study that sequenced previously known ale strains and found them to make up two genetically related groups called "Beer 1" and "Beer 2" (see Saccharomyces History of Domestication and "A family tree for brewer's yeast" by Lars Marius Garshol). The closest related domesticated strains were 3 German hefeweizen strains, however, this relation is likely just due to both groups being hybrids rather than having any historic relation [9].

Although whole genome sequencing of more kveik strains is needed in order to fully flesh out a family tree of kveik [15], based on the 6 strains that were analyzed, kveik strains seem to be divided into two related genetic groups, with the Muri, the Simonatis Lithuanian strain, and a Norwegian bread yeast falling outside of these two groups completely, which arguably categorizes them to not actually be considered "kveik". The two groups of kveik probably originated from two ancestors that were hybrids between a "Beer 1" yeast and wild yeast. Interestingly, the kveik cultures that have multiple strains have strains from both genetic groups of kveik. For example, Hornindal, Granvin, Laerdal, and Stordal Ebbergarden all contained strains from both genetic groups of kveik. Overall, their genetic diversity is wider than the genetic diversity of other "Beer 1" subgroups [9]. See this updated family diagram of yeast.

Preiss et al. (2018) also measured the fermentation characteristics of individual kveik strains in their study, the first published data in this regard for kveik. At 86°F (30°C) they found that 11 of the 24 pure strains of kveik outperformed the best control strain (WLP002) in fermentation rate. There was still a very wide range of attenuation rates between the kveik strains (60-90%). Of the 6 strains that had their DNA sequenced, all but one of the Granvin strains fermented maltotriose. All of the strains tested were POF- (meaning they did not produce significant 4-vinylguaiacol phenol) except the Muri strain which is not genetically related to kveik. One of these Stordal Ebbegarden strains also contained a unique mutation on the FDC1 gene that results in the inability to produce phenols and has not been reported before in science. They also found that kveik strains tend to produce fatty acid esters at levels that are typical for other domesticated yeast strains, such as ethyl caproate (pineapple, tropical; threshold 0.21 ppm), ethyl caprylate (tropical, apple, cognac; threshold 0.9 ppm), and ethyl decanoate (apple; threshold 0.2 ppm). The kveik strains studied did not produce high levels of the isoamyl acetate ester (banana) and generally lower levels of the fusel alcohol isobutanol compared WLP001 and WLP002. Strangely, 5 of the 6 strains that were analyzed could form spores, which is not typical for brewers yeast [9].

The kveik strains studied by Preiss et al. (2018) displayed unique abilities as far as withstanding stress in their environment. Most of the strains at least doubled their growth at 43°C and grew to their maximum potential at 40°C, while the control strains WLP001, WLP002, and WLP029 showed limited growth at those temperatures. This demonstrates kveik's ability to withstand high-temperature fermentations. All strains tested died at 45°C [9].

Kveik strains were also demonstrated by Preiss et al. (2018) to have a higher tolerance to alcohol than some of the domesticated strains tested (WLP001, WLP002, and WLP029), as well as unique flocculation characteristics. Most of the kveik strains doubled in growth in media with 14% ABV ethanol, and about half of them doubled in growth in 16% ABV ethanol media. Half of the strains of kveik were highly flocculant, but some other strains were very poor flocculators. It is possible that since kveik is a mixed culture of several strains of yeast that the highly flocculant strains assist the others in flocculation thus diminishing for the other strains to evolve flocculation properties [9].

See also:

Sigmund Gjernes's Voss Kveik

The NCYC found that a sample of Sigmund Gjernes's kveik was made up of three strains of S. cerevisiae. No bacterial contamination was found. DNA fingerprinting found the strains to be closely related [16]. See Larsblog Kveik analysis report for more information.

Omega Yeast Labs and The Yeast Bay independently isolated one of the strains from the Voss Kveik. It is not known if these are the same strains, or which NCYC strain they correspond to. However, they are thought to be similar in their flavor profile [17].

The full culture with all strains is available from Mainiacal Yeast.

Tips For Use

Svein Rivenes's Voss Kveik

Brewer Svein Rivenes deposited a sample of kveik in 2009 via Håken Hveem. No bacterial contamination was found [12]. Seven strains were isolated from the blend.

John Nornes's Voss Kveik

Martin Warren collected a sample from brewer John Nornes in Voss in 2015. The kveik has been analyzed by NCYC, but the strains have not been assigned numbers yet.

Stein Langlo's Stranda Kveik

Terje Raftevold's Hornindal Kveik

Terje's kveik was mixed with 2-3 other kveiks. This probably explains the wider variety of isolated strains. It also contains bacteria, and these bacteria seem to be contributing positively to the aroma (and they don't sour the beer). See "Kveik testing" and "Hornindal: interviews and collecting kveik" on Larsblog for more information.

Two strains are packaged together as a blend by Escarpment Laboratories as their Hornindal Kveik Blend. Mainiacal Yeast Labs (contains lactic acid bacteria from the original sample) and Omega Yeast Labs (does not contain lactic acid bacteria) [20] sell the native blend.

Olav Gausemel's Hornindal Kveik

This is the kveik Terje Raftevold's kveik branched off from in the 1990s. Olav says he has mixed it with other kveiks 1-2 times in the meantime. It was collected for comparison purposes. Little is known about this kveik, but it is described in Rasmussen's thesis.

The Lida kveik

From Samuel Lien in Grodås, Hornindal. Collected by William Holden. Samuel got the kveik from Hans Øen, who moved from Hornindal from Faleide in Stryn, so the yeast is originally from Stryn. Øen is dead, but Lien is alive. Pitch temperature 30.

Lars Andreas Tomasgard, Hornindal

Lars Marius Garshol collected this from Lars Andreas at the Kornøl Festival. More information needed.

Dagfinn Wendelbo's Lærdal kveik

Arvid Solheim collected this kveik from Dagfinn Wendelbo at Ljøsne in Lærdal. Wendelbo lost his own kveik a couple of years ago, and got this from Per Gjermann. As far as I understand it originates with Gjermann, from the farm Stødno in Lærdal.

Hans Haugse's Granvin kveik

Originates from Hans Haugse from Granvin, Hardanger, via Einar Vestrheim and Lars Olav Muren. NCYC analysis indicates that it contains both Pichia and Saccharomyces.

Commercially available from Mainiacal Yeast.

Sigurd Johan Saure's Sykkylven kveik

Originates with brewer Sigurd Johan Saure, at Tormodgarden in Aurdal in Sykkylven. Sigurd says the yeast has definitely been reused since his great-great-grandfather's time. His great-grandfather mixed it with another yeast from a friend in the 1950s, after the yeast "got weak". Collected, but not sent to the NCYC yet.

Ebbegarden, Stordal

This kveik comes from Jens Aage Øvrebust, and was collected by William Holden. Jens originally brewed raw ale, but started boiling the wort because his beer became sour now and then. Pitch at 28C, harvest yeast from the top after a couple of days. Prefers not to let the yeast go over 30. Usually ferments 4-6 days. Sent to NCYC and NTNU, but no results yet. Jens usually ferments down to an SG of 1010, because he doesn't want the beer sweet. He says the yeast has always been in the valley as far as he knows.

Appears to have an unusual relationship with hops, so beware that this yeast may accentuate the hop bitterness in your beers. Jens says he only dry-hops himself. Richard Preiss from escarpment Laboratories reported that sensory data on how bitter beer tastes with Ebbegarden kveik versus other yeast strains (Hornindal kveik and Conan strain) is that it produces a slightly more bitter beer, but the effect is not big [21].

One strain from this kveik is available from Sleight Beer Lab. Escparment Laboratories sells the complete blend as sourced by Jens Aage Øvrebust.

Framgarden, Stordal

From Petter B Øvrebust at a neighbouring farm in Stordal. Collected by William Holden. Petter still brews raw ale, pitches at 30C, ferments 2-3 days.

Commercially available from Mainiacal Yeast. One strains is available from Sleight Beer Lab.

Midtbust, Stordal

From Odd H Midtbust at a third farm in Stordal, collected by Lars Marius Garshol. Jens Aage Øvrebust says this yeast is pitched at 33C, and that it should be kept at this temperature during fermentation. Usually ferments about 3 days. Midtbust harvests the yeast from the top.

Commercially available from Mainiacal Yeast.

Jarle Nupen, Eidsdal

Jarle brought this kveik to the Kornøl Festival, where he gave it to Lars Marius Garshol. Jarle originally got the yeast from Tore Hjelle in Eidsdal in 1979-1980, so the yeast comes from Eidsdal. Jarle has kept the yeast ever since, and he says "I've watched it like gold." Jarle pitches at 31 degrees, and doesn't want the fermentation to go above 36 degrees. He ferments roughly 30 hours.

Jakob Torp Årset, Geiranger

Jakob brought this kveik to the Kornøl Festival, where he gave it to Lars Marius Garshol. More information needed.

Eitrheim-kveiken, Hardanger

Jakob Eitrheim, born 1920, has been using this kveik in Bleie since the 1950s. He says he got it from his grandfather, who lived at Eitrheim (now part of the town of Odda), but he doesn't know where it came from before that. So he claims to know the history of the yeast back to the late 19th century. Jacob ran out of yeast in the late 1950s, and got new yeast from his brother, who had the same kveik.

The yeast is pitched at 37C, and harvested from the bottom. The Eitrheim family dry it and keep it in glasses. They usually ferment 3-4 days.

Wollsæter

Jørgen Wollsæter's kveik culture.

Commercially available from Mainiacal Yeast Labs [22].

Årset in Eisdal

Escparment Laboratories sells the complete blend as sourced by Jakob Årset, on the farm Årset in Eidsdal, Norway. The overall flavour profile is similar to the Hornindal Kveik Blend, but this blend exhibits a broad temperature range (we have heard of sub-15ºC) and tolerates acidic wort quite well. Attenuation: 70-80% // Optimum Temp: 20-37ºC // Alcohol tolerance: Very High // Flocculation: High.

Landrace Yeast In Other Countries

There are farmhouse yeasts in other countries that have survived for generations, similar to kveik, but are genetically distinct from kveik. Since the term "kveik" refers to just Norwegian farmhouse yeast, the term "landrace yeast" has been proposed to refer to farmhouse yeasts as a category of yeast. Non-kveik landrace yeast include yeasts from Lithuania and Russia include Simonaitis, Rima, and Jovaru Alus. See Landrace Yeast for more information.

Relevant Larsblog Posts and MTF Content

MTF "The Podcast"

Kveik

Raw Ale

  • Raw ale - Definition of "raw ale", and the methods used to brew it in historical and traditional farmhouse brewing.

Norwegian Farmhouse Ale (Maltøl)

Farmhouse Ale in Other Countries

MTF Threads

Kveik Ring/Kveikstokk and Drying

Kveikstokk with yeast slurry on it. Images provided by Antonio Golia ("Homebrew Condor").

These are wooden carvings used to store dried kveik. Their use is simple: drag the kveik ring/kveikstokk through the krausen of a fermenting beer, and then hang the ring/kveikstokk to dry. On the next batch, the ring/kveikstokk is dunked into wort to reactivate the yeast [23]. Note that not all yeast reacts well to drying. Kveik has this exceptional ability. For example, Brettanomyces is known to not be tolerant of drying/desiccation [24].

Kveik rings for sale:

History/crafting instructions/usage:

Videos

  • Traditional farmhouse malting and brewing, from Aurland, Sogn (audio is in Norwegian, but the imagery is still worthwhile if you do not understand Norwegian):
  • Brewing with the elusive Hornindal-strain, done old school, no boiling, 2 days fermenting:
  • RåØl (Raw Beer) Brewday with John Palmer at EIK og TID:
  • Presentation by Lars Marius Garshol (in Norwegian):

See Also

Additional Articles on MTF Wiki

External Resources

References

  1. ↑ 1.0 1.1 Richard Preiss. Milk The Funk Facebook group thread on kveik. 06/19/2018.
  2. ↑ Bab.la Dictionary. Retrieved 01/21/2016.
  3. ↑ 3.0 3.1 3.2 Lars Marius Garshol. Milk The Funk Facebook group reply on the meaning of the word "kveik". 12/29/2016.
  4. ↑ "Kveik" - what does it mean?. Lars Garshol. Larsblog. 10/29/2017. Retrieved 10/29/2017.
  5. ↑ "Analysis of farmhouse yeast (kveik)." Larsblog. Lars Marius Garshol. 09/06/2016. Retrieved 09/06/2016.
  6. ↑ 6.0 6.1 6.2 Kveik: Norwegian farmhouse yeast. Larsblog. 11/07/2013. Retrieved 01/14/2016.
  7. ↑ Lars Marius Garshol. "The juniper mystery". Larsblog blog. 02/02/2017. Retrieved 12/13/2018.
  8. ↑ Maltøl, or Norwegian farmhouse ale. Larsblog. 10/11/2016. Retrieved 01/14/2016.
  9. ↑ 9.0 9.1 9.2 9.3 9.4 9.5 Traditional Norwegian Kveik Are a Genetically Distinct Group of Domesticated Saccharomyces cerevisiae Brewing Yeasts. Richard Preiss, Caroline Tyrawa, George van der Merwe, Kristoffer Krogerus, Lars Marius Garshol. 2018.
  10. ↑ Norwegian farmhouse ale. Larsblog. 10/27/2013. Retrieved 01/14/2016.
  11. ↑ Lars Marius Garshol. Kveik facebook group thread on kveik terminology. 11/03/2018.
  12. ↑ 12.0 12.1 12.2 "Kveik testing". Larsblog. 05/05/2014. Retrieved 01/20/2016.
  13. ↑ Sensory data on kveik strains shared by Richard Preiss on MTF. 09/15/2016.
  14. ↑ Justin Amaral. Milk The Funk Facebook group thread about lactic acid bacteria in kveik cultures and sensitivity to IBU. 06/05/2018.
  15. ↑ Richard Preiss. Milk The Funk Facebook group comment about the two families of kveik yeast. 09/13/2018.
  16. ↑ Analysis of Sigmund Gjernes Voss yeast sample for Lars Marius Garshol, RÆLINGEN NORWAY. September 2014. Retrieved 01/20/2016.
  17. ↑ Conversation with Lance Shaner and Lars Marius Garshol on MTF. 01/04/2016.
  18. ↑ Lars Marius Garshol. Milk The Funk Facebook group thread on Imperial Organic Loki. 10/31/2018.
  19. ↑ Lars Marius Garshol and Richard Preiss on Voss alcohol tolerance. Milk The Funk Facebook group. 08/04/2017.
  20. ↑ Private correspondence with Adi Hastings of Omega Yeast Labs by Dan Pixley. 03/27/2018.
  21. ↑ [https://www.facebook.com/groups/MilkTheFunk/permalink/2397563676938499/?comment_id=2399642916730575&comment_tracking=%7B%22tn%22%3A%22R%22%7D Richard Preiss. Milk The Funk Facebook group thread on the bitterness produced by Ebbegarden kveik. 12/04/2018.]
  22. ↑ Justin Amaral. Milk The Funk Facebook group post about Mainiacal Yeast kveik. 08/21/2018.
  23. ↑ Lars Marius garshol. Milk The Funk Facebook group post about using a kveik ring. 2017.
  24. ↑ Justin Amaral. Milk The Funk Facebook group post on kveikstokk and drying Brettanomyces. 08/16/2018.
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