The Kalevala, the national epic of Finland, explains the origins of beer in a rather lengthy and vivid way. When creating the primal beer, the brewster Osmotar have great difficulties in starting the fermentation, until a bee brings a working ferment. Hence I was delighted to hear that Claus Christensen, founder and brewmaster of Munkebo Mikrobryg had captured wild yeast from bees. This is a story how that yeast ended up fermenting beer.
In nature yeast surrounds us everywhere, especially near sugar sources like fruits, berries and bark of trees. Therefore foraging yeast from bees makes a lot of sense, as they hang around in places where wild yeasts reside.
Capturing wild yeast from nature is not a simple task however. Along with yeasts grows a rich microflora of various bacteria unwanted in brewing. Even if one manages to isolate yeast from bacteria, it becomes a lottery to find strains which perform well in the brewery – the yeast should be able ferment malt sugars well and produce good tasting beer.
Claus is from the island of Funen in Denmark where his grandmother used to brew traditional farmhouse ales. His family used to have own farmhouse ale yeast, but that got lost around 1950s. This motivated Claus to hunt his own local farmhouse ale yeast, and surely his PhD in Health Science with studies in cell and molecular biology helped to start the project.
Claus got few bees from a neighbouring beekeeper. He dropped bees into petri dishes where the bees left the microbes they had been carrying. The dish had a selective growth media favoring yeasts which could tolerate higher alcohol levels and hop bitterness.
After two and half years and tens of experiments, Claus got four pure culture yeast strains ready for brewing. These strains, named Munkebo #001–#004, produce various fruity aromas and flavors. #001 and #003 are inclined for banana while #002 gives raspberries and cherries, and #004 peach and apricot. White Labs laboratories identified their species as Saccharomyces cerevisiae, the same as standard brewer’s and baker’s yeasts. Claus also served an ale made with #004 to the old men of Funen, who said that the taste is similar to Claus’s grandmothers farmhouse ale back in the old days.
Now Munkebo Mikrobryg ferments their Hjemstavn Ale (5 % ABV) and Hjemstavn Stærk Dansk Ale (10 %) with #004. The fruitiness of the bee yeasts is quite delicate and I feel that the ordinary 5 % version expresses the character better. Amber-colored Hjemstavn Ale is an easy going malty ale with subtle yet noticeable apricot note from the yeast, along with toffee, hay, black pepper and sea salt. Hjemstavn Stærk Dansk Ale is an excellent beer, but the yeast character is mostly hidden by the rich maltiness.
Claus gave me samples of #002 and #004, and I tested them in my home brewery. First I fermented Finnish farmhouse kind of ale with them, actually my basic sahti recipe, except for the yeasts (split batch between #002 and #004). These yeasts seem perform well at fairly high temperatures, and hence I fermented the ales at 24°C (75°F), as Munkebo ferments its Hjemstavn Stærk Dansk Ale. They did perform well, and the ales turned smooth, sweet, malty and deceptively drinkable ale with 8–9 percent in alcohol.
As typical for Nordic farmhouse beers, I served these ales very fresh, which in this case was one week after a brew day. I was stunned how soft in alcohol the #004 version was right from the beginning, completely devoid of solvent or sharp alcohol. This yeast seems to be a an exceptionally smooth ferment for strong beers. #002 gave some alcohol sharpness which gradually smoothed out. At first fresh maltiness masked the fruity qualities, but after a month delicate background note of apricot started to appear in #004. In #002 the fruitiness remained hidden. In this test I preferred #004, but #002 had its fans too.
This story is based on an interview Claus gave me in Copenhagen in May 2016, as well as few emails after that. Munkebo sells these four Hjemstavn yeasts in their web shop, but I don’t know if they distribute outside of Denmark.