How Czech Brewers Make Low-Alcohol Lagers With Big Flavor

Beer fans who make it to Prague before the weather turns will find exactly what they’ve been told to expect: a beautiful Old World city where classic Pilsner-style beers are everywhere, with hundreds of pubs serving excellent, easy-drinking lagers with 4 to 5 percent ABV.

But in a few spots, thirsty travelers might come across something unusual, and which is largely unknown outside the country: a growing array of compelling, low-alcohol beers that are generally only available during the summer months. With only about 2.8 to 3.8 percent ABV, these lagers are slightly weaker than most American light beers. But in terms of taste, they’re much burlier, packed with so much noble hop bitterness and aroma that they appear to violate basic brewing guidelines.

For example, take the Letní 8º beer from Únětický Pivovar, just north of Prague, which clocks in at 3.4 percent ABV. According to the brewery’s general manager Jan Fišera, a recent lab analysis found that this limited-run “summer” lager contains a palate-smacking 45 IBUs — well over the minimum bitterness level of a classic West Coast IPA, though with about half as much alcohol.

“It’s very bitter, but light in taste, and you can smell citrus fruits,” he says. “This beer is very popular among people who are riding bicycles.”

Far more than a mere refresher for cyclists arriving on the nearby riverside bike trail, Únětický Pivovar’s summer lager and other examples show how Czech brewers are making low-alcohol beers that are complex, rich, and truly fun to drink. More broadly, they offer a blueprint for brewers elsewhere who’d like to pull off the same trick.

Both Traditional and Modern Techniques

The Czech approach is not as straightforward as simply making a weak lager with tons of hops. To start, there’s the very character of the Bohemian hops they’re using, which have long been described as very gentle, delicate, and “noble” in terms of aroma and bitterness. Typically, they are low in cohumulone, a naturally occurring alpha acid compound that can result in harsh, unpleasant bitterness.

For Únětický Pivovar’s Letní 8º, brewer Jan Lumbert uses two less common Czech hops, Sládek and Kazbek, as well a portion of Citra — a craft beer favorite that is also relatively low in cohumulone — which adds a bit of New World fruitiness.

At Pivovar Hostomice, brewer Štěpán Kříž uses an aromatic but undersung modern Czech variety, Vital, for the first two additions in his 2.9 percent-ABV summer special, Fabián 7º, before finishing with whole cones of classic Saaz hops for aroma. In his eyes, when it comes to making a compelling low-alcohol beer, bitterness is just one piece of the puzzle.

“The body and the bitterness are absolutely complementary,” he says. To get a rich, full body in a relatively weak beer, it helps to use the traditional Czech method of decoction mashing, in which a portion of the mash is moved to a separate vessel and raised to a full boil for about 20 minutes before being returned to the main mash. That process results in more unfermentable sugars and thus a greater impression of fullness, compared to the simpler and more widespread technique of infusion mashing. “Infusion really won’t produce enough body for a beer like that.”

“At some point, we’re inside our own heads looking out at these flavors that are coming in, and it creates a certain impact on us. Bitter definitely adds impact.”

Kříž brews his Fabián 7º with 100 percent Pilsner malt, using a double-decoction mash, the same approach used at Únětický Pivovar and most Czech breweries. But not all producers make their low-alcohol lagers with only Pilsner malt. At Pivovar Bubeneč in Prague, the 3.8 percent-ABV summer Osmička (meaning “No. 8”) also includes Munich malt, which adds a bit of heft. To boost the fullness of Únětický Pivovar’s summer beer, Lumbert uses both Munich and melanoidin malt in the mash — a trick that could easily be pulled off by breweries that are not set up for decoction.

While full-strength Czech beers are famous for long lagering times, like the 90 days of cold conditioning used for the flagship lager at nationally owned brewery Budweiser Budvar, the low-alcohol summer brews need much less time to condition. Únětický Pivovar’s Letní 8º gets about 16 days of lagering. Kříž says Fabián 7º gets about two weeks of cold conditioning.

While bitterness is important, he says, brewers shouldn’t only focus on the IBUs.

“Use hops for bittering, sure, but also add something for aroma,” he says.

Why and How It Works

Czech beer culture has a bunch of unique quirks, including the widespread naming of beers by their original gravity on the Plato brewing scale. Like Fabián 7º and Letní 8°, these special low-alcohol summer lagers are brewed around 7º and 8º on the Plato scale, while the country’s most commonly consumed beers with 4.5 to 5 percent ABV are brewed at 11º and 12º.

Those numbers show how strange these beers really are, at least once you translate their numbers into their North American equivalents. Letní 8º is brewed at 8º, which comes out to 1.032 on the “specific gravity” scale commonly used by homebrewers and brewers outside continental Europe. That scale led to the so-called “brewing unit to gravity unit,” or BU:GU ratio, a guideline introduced in the book “Designing Great Beers” by Ray Daniels and widely cited ever since as a way to think about bitterness and the concept of “balance” in beer styles. A beer with an original gravity of 1.032 on the specific gravity scale would have 32 “gravity units.” Therefore, with 45 IBUs, the 45:32 BU:GU ratio for Letní 8º comes out to 1.406 — higher than many old-school Imperial IPAs, which often top out around 1.15, and wildly higher than the .65 or .75 ratios of even very bitter lagers, to say nothing of most low-alcohol and “light” versions.

“The perceived character is bitterness, but it isn’t really just bitterness. It’s bitter combined with mouthfeel.”

(In fact, it’s not just the ratio of the low-alcohol summer specials that is higher than many lagers: In absolute terms, the 45 IBUs of Únětický Pivovar’s Letní 8º is more bitter than the flagship Czech lager Pilsner Urquell, which has 37 IBUs, while Fabián 7º — technically brewed at 7.3º Plato — has 33 IBUs, the same amount as the full-strength Budvar 33.)

Gordon Strong, author of “Modern Homebrew Recipes: Exploring Styles and Contemporary Techniques” and the principal author of the Beer Judge Certification Program (BJCP) Style Guidelines, points out that while the BU:GU ratio can be helpful for thinking about beer in the big picture, there’s a lot more going on in the glass. A big part of that is not the beer’s starting gravity before fermentation, but the gravity of the final product after the yeast has finished its work.

“I think the final gravity has more say in determining the perceived bitterness than the starting gravity,” he says. Another factor could be diacetyl, a byproduct of fermentation that is characteristic of many Czech lagers at a limited level, and which adds increased mouthfeel and body. “All of these factors that, to me, separate Czech beer from German beer, this fullness, all that tends to offset that the impact of bitterness,” he says.

In fact, how we taste might have a lot to do with what makes the Czech Republic’s low-alcohol lagers work. For his upcoming book, “Your Tasting Brain,” beer writer and brewer Randy Mosher has spent years researching and writing about how the senses function. Hop bitterness itself can create the impression of fullness, he says, making a weak beer seem less watery and thin.

“Those humulones are bitter compounds — they tend to be fatty, greasy, oily, waxy, and they stick to the skin in your mouth,” he says. “The perceived character is bitterness, but it isn’t really just bitterness. It’s bitter combined with mouthfeel.” Psychology also plays a role, since we only have one brain to process all of our senses, which are constantly sending impressions, all at the same time. “At some point, we’re inside our own heads looking out at these flavors that are coming in, and it creates a certain impact on us. Bitter definitely adds impact,” Mosher says.

For brewers who want to emulate the taste profile of Czech lagers, a slightly higher mash temperature can also lead to a bit more residual sugar after fermentation finishes.

“You can brew them with more residual carbohydrates,” Mosher says. “You can load up the grain bill a bit and mash it a little hotter. Your attenuation is going to be less.”

That’s one way to get the taste of a Czech low-alcohol summer lager. The other is to hop on a plane to Prague. Letní 8º will be available at Únětický Pivovar and a limited number of local pubs until about mid-September, Fišera says.

Other low-alcohol lagers are likely to disappear around the same time. Currently, Pivovar Hostomice’s Prague taproom is down to its last two kegs of Fabián 7º, which Kříž brewed for the first time this year. Kříž says he mostly expected to serve it to the cyclists who visit the brewery’s village location in the foothills outside Prague, but it proved remarkably popular at the city outlet.

“When it’s hot, this beer is really great,” he says. “I think this type of weak beer is ideal for the summer.”

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