Thanks to Antonie Van Leewenhoek and later Louis Pasteur, we now know that the reason beer has ethanol in it isn’t because of magic, alchemy, or Odin spilling a few drops of the six-pack he swiped in Asgard. However, on the timeline of beer, the identification, isolation, cultivation, and carefully disciplined use of Sacchromyces Cervisiae, S. Pastorianus, S. Carlbergensis, and Brettanomyces Bruxellensis yeasts occupy a small amount of the far right-hand edge of the line.
There are four thousand years of brewing history to the left of a Dutchman and his microscopes. Beer itself was instrumental in keeping the spark of humanity teetering forward, and that fact wasn’t lost on medieval brewers. They felt it was divine providence that blessed their efforts and allowed them to produce a beverage that was remarkably free of whatever was killing water-drinkers across Europe during the era when water (and the cholera it contained) would just as likely kill you as not.
So how did brewers make beer before anyone had seen a yeast cell? In Northern Europe, when the legends of Loki, Ragnarok, and the Grendel were born, the solution was straightforward, and fit well with the marauders’ culture: You poke it with a stick.
For the most part, craftsmanship and trades during the medieval period were close-knit communities that passed knowledge and techniques from generation to generation through oral histories. Without printing presses (or literacy, for that matter), grandpa’s journal didn’t go much farther than the grandson’s ears.
For brewers, tools were passed down as well. Amongst the kettles, paddles, mills, and other brewer’s kit, there was often found a magic wand. This wand was used to call forth the divine providence that magically transmogrified boiled barley syrup into beer.
Sometimes, the magic wand was the size of a staff and intricately carved. Other times it was a handful of alder sticks tossed into a fermenter. Functionally, the idea was to stir the fermenting beer with the magic wand as soon as it cooled off after the boil, then set it to one side until the active fermentation phase, when it would be stirred again. Then the wand was stored somewhere cool and dry until the next batch needed to be blessed.
What they were doing, without even realizing it, was collecting a dense sample of the yeast at the peak of its activity. Yeast could survive the dry period between batches, and would then be used to inoculate the next batch. The more intricately carved the stick, the more surfaces there were for the yeast to adhere to. In Norway, for instance, the traditional device is called a kveikstokk, and is an interlocking ring of about 70-90 carved wooden keys that gets tossed into the fermenter with the just-cooled wort and is recovered at the peak of fermentation to be air dried for the next use.
There are stories of yeast cultures (called a kveik) from Norwegian farmhouse brewers that date back centuries. Due to some odd liquor laws in Norway, beer made at a family farm wasn’t subject to the same heavy taxation as other alcoholic beverages, so farmhouse brewing has been around for a very long time.
However, as Norway’s commercial breweries grew and consolidated, the products became driven by the bottom line and suffered a fate similar to U.S. brewing. Like much of the rest of the world, there is a strong craft revival in Norwegian brewing. Nøgne Ø, and Haand are examples of Norwegian craft scene. Nøgne Ø is imported into the U.S. by Shelton Brothers.
Despite the open windows, the bulk of the yeast for the batch is derived from the wood planks used in the fermentation vessels.”
Even though the details of the mechanism for fermentation wouldn’t be understood until the middle of the 19th century, early brewers knew in their guts that there was something special about that part of the brewing process that showed up as swirling, foaming life in their fermentation tanks. To them, it was incontrovertible evidence of the hand of the divine in their work. Their grandfathers taught them that you had to have a bit of the old beer to make the new beer work right, and that bit that was saved became the physical manifestation of the divine.
Hence, the yeast starter passed along and recycled from batch to batch became known in English as Godisgood.
While there are still family farms in Norway that use starters with distinctive strains of yeast that have been passed down from generation to generation in an unbroken line spanning centuries, today’s most accessible way to sample the randomness of medieval fermentation is to search for Belgian lambic beers. These beers are exposed to wild yeast in open wooden fermentation tanks that are inoculated with wild yeast by exposure to whatever is blown in through the open brewery windows.
Despite the open windows, the bulk of the yeast for the batch is derived from the wood planks used in the fermentation vessels. It’s the same concept as a kveikstokk, but on a much larger scale. Notable for their strong winelike flavors, lambics are a throwback to thousands of years of brewing history.
A modern brewery’s yeast lab makes the fictional labs of CSI and Bones look like a crappy version of an RV meth lab in the Albuquerque desert. Doctorates are busy the world over, developing new strains of yeast in search of increases in efficiency and improvements in flavor consistency. It’s a long way removed from poking a kettle of beer with a stick and hoping that God would be good, and bless you with a healthy fermentation.