St. Louis Beer Blog: Brewing Czech Pilsner

Brewing Czech Pilsner  

By Nate Brinson

As I have mentioned in a previous post, a large portion of portfolio is classic European style beers (aka our Reverence Series). We source ingredients either directly from Europe or failing that, find domestic ingredients which mirror their Europeans counterparts as closely as possible. For example, when historically, culturally and/or stylistically appropriate, we use decoction mashing to brew these beers despite the extra effort, energy, and know-how required to conduct these mashes.

Czech Pilsner is one of those beers in which we use decoction mashing as it is de rigueur in Czechia*. While we’re known for German roots, we also honor Czech brewing traditions, especially since arguably now brewing culture holds as close to its traditions like the Czechs. Part of Czech beer character is a substance called diacetyl.  

For the chemists out there, diacetyl is a compound in the family of vicinal diketones, and it forms during fermentation when alpha acetolactate leaks from the yeast cell during fermentation. When it oxidizes in the beer**, it forms diacetyl.  

Diacetyl has a very low flavor threshold***, meaning that even at relatively low amounts, its flavor can be detected, even as low as 100 parts per billion. At the low end of the flavor threshold, diacetyl doesn’t add much to the flavor per se, but it will contribute a greater mouthfeel to the beer as well as a hint on slickness on the tongue. As its levels in beer increase, it will lend a taste similar to butter or butterscotch; it happens to be the exact substance used in making fake butter for movie popcorn!  

It is generally considered an undesired flavor in beer, but fortunately, given the proper conditions, yeast re-consumes diacetyl into flavorless compounds, reducing its residual amount in beer to a level under the flavor threshold. In fact, we go to great lengths during the fermentation and maturation process to ensure that diacetyl is not perceptible in our beers.

However, many beers in Czechia DO have perceptible levels of diacetyl in the many of their beers****. As an homage to this tradition, we make efforts to keep a slightly perceptible level of diacetyl in the finished beer. To do this, we monitor the fermentation, but unlike our other beers, we separate the beer from the yeast before it has a chance to reduce diacetyl below the flavor threshold. This will give the beer a little extra body and perhaps a slight butter-like note*****.

This is just one more way that Czech Pilsner distinguishes itself from Stammtisch, our German Pilsner. Personally, I recommend having a glass of each back-to-back for the best comparison and to help determine which you prefer!

* Decoction is a labor/time intensive mashing method which involves removing a portion or the mash, boiling it, and adding the boiled mash back to increase the main mash’s temperature. For Czech breweries to receive a European Union PGI (Protected Geographical Indication) of “České pivo” (Czech beer), the beer must be double or triple decocted. Even if a PGI weren’t on the line almost every Czech brewer swears by the advantages of decoction, namely richer malt flavor and greater “drinkability”

** Oxygen in wort (the malty sweet liquid made by brewers before fermentation) is necessary for healthy yeast growth/fermentation

*** About a quarter of the population cannot taste diacetyl at all, including a few UCBC employees! It is possible for such people to train themselves to detect it, but they have to use different taste/mouthfeel sensations in order to perceive it. (It’s similar to learning a second language as an adult.)

**** I have been fortunate enough to visit Prague twice, and I had several beers there in which diacetyl was certainly present! Most famously, Pilsner Urquell, the original Pilsner which I described in this blog post, has a low level of diacetyl in the beer. I’m not sure the reason for this. Czech brewers will debate how vital it is to Czech lager, but some level is usually present.

***** Subtlety is the key word here. We’re not trying to recreate a vat of fake movie butter popcorn!

‍