HARNESSING THE POWER OF SPONTANEOUS FERMENTATION
Yeast is literally everywhere, it’s on the skin of fruits, the petals of flowers, even on your eyelashes. Generally speaking, wherever there is a positive flavour in nature there’s a microbe to explain why it tastes / smells so good. Someone, somewhere, a long time ago, left the beginnings of bread out overnight and these yeasts fermented it into something that resembles beer. Not very good beer, but it was a primordial start!
At its core, OverWorks is all about spontaneous fermentation. To harness the power of these incredible airborne yeasts that are all around us we designed a custom copper vessel to catch them, a ‘coolship’. In its own dedicated room, we fill this copper tub with wort, throw open the windows on dry windy nights and allow whatever the wind carries in to get settled.
The process starts with a full turbid mash – an intensive mashing regime that requires a heavy proportion of unmodified wheat in the grist and several temperature rests achieved by removing portions of wort, heating and reintroducing to step the mash temperature up. Hardly an ideal brewday on the super-efficient BrewDog Rolec brew kit. The result is a wort so cloudy it’s described as milky, which is sent via pipeline from the BrewDog Brewhouse to Overworks’ cellar into the coolship overnight.
The next day we move the now cosy wild yeast in the infected wort into a tank and gently recirculate to ensure an even mix of sugar and bugs. The homogenised, spontaneous cultures in the dextrin rich wort is transferred into barrels to ferment happily (an initially messily) away in their new home until the beer is ready to be enjoyed.
Unlike most beers this fermentation process takes years, not days. Complex symbiotic relationships between microbes, at different stages of their metabolic pathways, are always in flux. The time taken for these beers to reach maturity isn’t ageing in the traditional sense, it’s ongoing, active fermentation. The beer will evolve and develop complexity over the course of a few years before they are blended and released.
This is the way beers were made for centuries, wild airborne yeast would spontaneously ferment alcoholic beverages. These yeasts were passed form batch to batch in various ways around the world, from a ‘magic stick’ to Norwegian kviek yeast rings which harboured dormant yeast cells until they were called upon to ferment another batch of beer. Yeast wasn’t understood as a separate, living ingredient in the beer making process until Louis Pasteur’s study in 1857. Then, in 1883 Emil Hansen managed to isolate a pure cell of brewer’s yeast – one of the most influential moments in beer history.
For hundreds of years brewers have been trying to train and curtail yeast to be as efficient and flavourless as possible. The light lager is the pinnacle of human intervention in fermentation. Throwing our doors (and literally windows) open to wild yeasts lets us revisit remarkably expressive and complex character of yeast in our beer.
Modern craft brewers generally focus on the character imparted by exciting, bold new world hops, complex specialty malts and any number of additional ingredients. At OverWorks we showcase expressive yeast strains with complex funkiness and tart acidity imparted by ‘alternative’ fermentation.