Tomorrow is the first ever National Sour Beer Day here in the US. Why and how to celebrate it?
First off, the why.
Sour beer was what all beer was like before our good friend Louis Pasteur developed pasteurization. Before pasteurization, people thought making beer was partly magical because it was the only way they could explain why their pot of boiled grain would eventually ferment and turn into beer. Turns out it wasn’t magical, just a process that we now call spontaneous fermentation.
Spontaneous fermentation is a brewing process that encourages contact with bacteria and other airborne microorganisms. Brewers will leave their wort exposed to the air overnight, which encourages airborne yeast and bacteria to find their way to the cooling boiled grain. As the yeast and bacteria feast on the exposed starch, they produce a highly acidic fermentation process that is completely different from your everyday brewing yeast. The product of spontaneous fermentation, sour beer, gets its distinct flavor from this interaction between wild yeast and wort.
Pasteur changed this when he discovered that heat killed off unwanted microorganisms, or what we now call the process of pasteurization. Pasteurization revolutionized many things, including brewing. It was his discovery that led to the realization that brewing was not partly magical, but a result of yeast converting starch into sugar. This allowed people to identify which strains of yeast were good for brewing and which were not. It meant that brewers could consistently make drinkable beer because before, with spontaneous fermentation, it was always sort of gamble. Sometimes just the good yeast and bacteria would find its way to the wort, and sometimes, the bad kinds found their way in too, spoiling the beer or worse, making people sick. The discovery of pasteurization and its consequent stabilizing force on brewing made it inevitable that producing sour beers would fall out of style.
Sour beers are still produced today though, mainly in the Senne river valley of Belgium. Until very recently, the only way to try a sour beer was to find a bottle from one of the few Belgian breweries still in production. Only a handful are left because the wild yeast necessary to make sour beer has all but died off. With the dropping number of breweries making sour beer, there were fewer sources of food for the yeast. Without food, the yeast couldn’t survive, and now it’s only in the breweries where production has been continual where you can find these partly magical air borne yeast strains.
Then another magical thing happened a few years ago – breweries in the US were able to start making sour beers. Allagash, a Maine-based brewery, discovered a strain of the special wild yeast in one of their beers and decided to do some experimental trials with spontaneous fermentation. From there, they were able to produce their Coolship series – sour beers named after the critically important shallow vessel that the wort cools in as it attracts the wild yeast.
Fast forward to tomorrow and the US’ first National Sour Beer Day. There are now enough American-produced sour beer options that a themed day celebrating this almost extinct way of brewing is actually feasible.
And luckily for Michigan, Jolly Pumpkin produces one of the better American sour beers: La Roja. Its sour flavor is a combination of the wild yeast’s acidic nature and the tart earthiness of cherries and stone fruit, creating a Michigan version of Belgium’s storied kriek, or cherry, beer.
Jolly Pumpkin can be hard to find anywhere, so your best bet is to head over to their Ann Arbor or Traverse City restaurants to imbibe in a glass or two of this magically brewed beer.
Cheers and happy Sour Beer Day!