Kettle Sour at the Eleventh Hour

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People had been asking for a sour beer for a while and, with fall approaching, I decided to go the quicker route to shake things up on our tap list. The Flanders Red is one of my favorite styles, and I wanted to recreate it without the pesky commitment issue of aging it for 18 months. This lead me to attempting my very first kettle sour, a very tumultuous ride.   

A kettle sour primarily differs from a traditional sour in that you are shortening the process of souring. The goal is to pitch your cultures in the kettle before boiling, and then to boil after, killing off the souring “bugs.” Pitching before the boil drops the pH level between 3.3-3.6, depending on what desired sourness level you are aiming for. There are a variety of souring cultures out there, but we went with plain, unpasteurized Nancy’s Yogurt found in any supermarket, which contains Lactobacillus acidophilus, the primary souring culture.

The process begins like any other beer: you mash then transfer the wort into your kettle. Then things take a turn. After the transfer, you allow the wort to cool to between 110-115ºF. If you have access to a heat exchanger, you can run your wort through it to speed up the cooling process. Once the correct temperature is achieved, your equipment can either work for this style, or keep you from doing it at all.

You want to “blanket” your wort under carbon dioxide to keep oxygen out of the souring process (carbon dioxide is heavier than the oxygen and other atmospheric elements, thus oxygen cannot penetrate the layer of carbon dioxide above the wort). Not doing this can result in horrible off-flavors. If your setup allows, use a manifold to inject carbon dioxide from the bottom of the wort so it purges any oxygen that might have gotten in your wort while mashing and transferring. While not totally needed, this can be a very effective way to clean out any oxygen before you sour.  

Over the next 24-48 hours, the pH of the wort will drop. You can monitor this by using pH strips, or by sampling until you have a desired sourness. Once you have reached your ideal sourness, it’s time to boil.

When creating a hop schedule, you want to aim for around 40 IBUs. We opted for Chinook at the start of the boil, and that was the only hop addition. Because of the lowered pH and the overall sour characteristics, you won’t be able to detect any hops. If you want to brew a hoppy kettle sour, your best bet is to dry hop it generously.  

In the fermenter, we pitched a Fermentis SafAle K-97 German Ale Strain for this beer, since we were attempting something near a Flanders. 

Brewing is a comedy of errors; this beer is a great example. Multiple equipment failures, temperature control issues, an oxygen leak during transfer, and running this beer through the heat exchanger twice before transferring made this beer unlikely to reach a pint glass. To boot, this beer refused clarify after it cold crashed. For an entire week, it wasn’t getting any better. The flavor and look didn’t line up.

The worst thing I could have done would be to try and put a beer on draft that I didn’t believe in, and, at the time, it simply wasn’t good enough. One day, I came into the brewery with the intention of declaring it a total loss and pitching it down the drain. I decided to give it one last look and taste. The color turned from a very off-putting black-brown to a deep red and the flavor likened to sour and tart cherry. I couldn’t believe it.

Years ago, I read Tony McGee’s (owner and founder of Lagunitas) book where he recounted the first time they brewed Brown Shugga’ and how it tasted downright awful right up until it didn’t, and a flagship was born. Beer is ready when it is ready, and I am glad I gave this beer enough time to develop into itself. Once it all came together, I had to ask a very simple question: “Is this a good beer?” It can be hard to remember something like this when you want to come as close to perfection as possible, but the answer was yes. This beer took an unlikely path, and ended up in a wonderful place.  

Now recreating it… That’s another story.

Charles Goman