Thursday, May 8, 2014

Kvass - Liquid Sourdough Beer

Adapted and expanded for American Sour Beers from Kvass Revival - BYO December 2010 written with Nathan Zeender. Originally it was its own chapter, then a part of Adding Spices and Herbs, and finally removed.

Kvass - Liquid Sourdough

In the summer of 2010, Scott Smith invited my friend Nathan Zeender (now head brewer at Right Proper Brewing Company) and me to join him at East End Brewing Co. to brew a batch of kvass. Smith was a longtime homebrewer before opening East End Brewing in 2004 and that spirit still pervades his operation. In addition to year-round beers, he is constantly brewing innovative and experimental beers with abandon, a sense of humor, and not a trace of pretension (which is a perfect match for Pittsburgh). The recipe for the batch we brewed, dubbed Wood St. Kvass, included 60 loaves of stale rye bread, supplemented with a mash of Pilsner malt, brown malt for toasty bread crust flavor, and rye malt to boost the flavor from the bread.

Kvass, from the Russian word meaning to leaven, is a millennium old, low alcohol (generally between .5% and 2.5% ABV) folk beer brewed from stale bread. Whether you bake your own bread or buy it from a bakery, it should not contain added oil or fat, as lipids can disrupt the head retention of the finished beer. Whole grain rye and wheat do add small amounts of oil, but not enough to disrupt head stability or mouthfeel. Avoid bread that tastes especially salty, while a slight salinity can enhance the malt flavor you never want a briny beer.

Our work started the night before brew day, driving to Wood Street Bread Co. to pick up the five dozens loaves of stale rye bread. That night we sliced the bread into large chunks and mixed it with roughly 1 gallon (3.8 l) of 190°F (88°C) water per loaf in a large modified hop-back. Stale bread is not necessary, but it is certainly a way to use food that would otherwise go to waste. After stirring to ensure all of the bread was saturated, it was left undisturbed overnight to give time for the bread to hydrate. An insulated cooler is useful for mimicking this process at home. It is not a major issue if the water cools off overnight because the high initial temperature will kill any lactic acid bacteria present.

The next morning we returned to the brewery for mash-in. After the starches in the mash were converted, we turned our attention back to the bread, which had absorbed the water and disintegrated into a thick doughy mass. We took turns using the mash paddle to encourage the liquefied bread to pass through the metal grate at the bottom of the hop-back where it could be pumped into the boil kettle. Starch is something brewers usually try to avoid getting into their boil, unless they are performing a turbid mash; it was hard not to laugh as we watched as chunks of bread goo shoot through the sight glass. Smith pumped the runnings from the mash into the kettle, mixing with the bread to create a milky-opaque wort.

Kvass wort attempting to leave the kettle.
At home it is much easier to transfer the liquefied bread into the kettle, simply pour it in. If the bread does not breakdown on its own, a mash paddle or immersion blender will finish the job. Getting the bread into the boil kettle is not the end of the challenges. The bits of bread tend to settle as the wort comes to a boil and can scorch if stirring is neglected for even a few minutes. The starch from the bread also makes boil-overs an ever-present danger, from the time the wort comes to a boil until flame-out. Standing next to the kettle was a hose, Smith frequently sprayed back the rising foam.

If the bread was not enough of a clue that we were brewing out of the ordinary, the hop schedule was another hint – 7 ounces (200 g) of low alpha-acid Styrian Goldings in 11 barrels (12.9 hL) – enough for a single IBU in the 341 gallons (1,291 l) of wort. Along with this meager hop addition, we added 1 pound (.45 kg) of caraway seeds, pulverized in a coffee grinder. Caraway is the dominant flavor in so many rye breads that its warm flavor is inextricable from the flavor of the grain in many people’s minds. As with adding any spice to beer, it is a balancing act to get a recognizable flavor to come through without trampling the drinkability of the base beer. After a short 30 minute boil, followed by whirlpool and heat exchange, the wort was ready for fermentation.

Bread yeast is the same species as ale yeast (Saccharomyces cerevisiae) and was historically procured from the town brewery in the days before active dried bread yeast became available at the supermarket. The yeast strains marketed for bread making have been selected for their ability to start fermenting quickly. When pitched into wort, active fermentation occurs as rapidly with a small amount of bread yeast as it would with a standard pitch of ale yeast. Bread yeast, however, is not selected for its flocculation properties, so do not expect to have a crystal clear beer soon after fermentation is complete.

At East End, the majority of wort was transferred into a cylindro-conical tank for fermentation. A modest 2 tablespoons (30 mL) of Red Star active bread yeast was rehydrated in warm water and pitched for the entire batch – about the same number of ale yeast cells suggested for 5 gallons (18.9 l) of barleywine. Despite this minimal pitching rate, Smith typically sees active fermentation begin fewer than 24 hours after pitching.

Dried bread yeast is not produced under the same tightly controlled conditions as dried ale or lager yeast, and as a result often has resident populations of both Lactobacillus and wild yeasts. The additional microflora are not a concern when quickly rising a loaf of bread, but pitched into wort the odds that sour or funky flavors will develop after weeks or months of storage are high. If you want to discourage the formation of lactic acid, aim for at least 10 IBUs and drink the kvass young.

Smith had discovered when he aged a previous batch of kvass the brew took on a complementary lactic sourness. To replicate that character he pumped the remaining 140 gallons (530 l) of the thick wort into two long-used oak barrels located in the brewery’s attic. A warm primary fermentation in porous oak encouraged a mixed fermentation with wild yeast and acid-producing bacteria. One of the barrels eventually tasted off, but last I heard the other barrel was still aging.

With all the valuable knowledge gleaned from our time at East End, along with historical inspiration, Zeender and I returned home with ideas of what kvass could be in our hands.

For our first kvass we scaled the recipe directly from East End's brew sheet and included a loaf of home-baked rye bread. Active fermentation was swift and completed in a few days at a warm enough temperature to encourage lactic acid production, 75°F (24°C). The result was a spritzy, lactic, and thirst quenching beer with a hint of caraway. This combination is reminiscent of a traditional way of enjoying Berliner weisse, with a shot of k├╝mmel (caraway liqueur).

For our second iteration we took inspiration from the folk beers of Scandinavia to create a winter kvass that included smoked malt, fresh spruce clippings, and dried elderberries. Whereas the East End’s kvass is an ideal summer beer, we sought to brew a kvass for the cooler months with referenced images of evergreens and the hearth, more brooding, unhopped, and slightly stronger. As a baseline for this more robust brew we added a loaf of homemade dark pumpernickel bread, and again fermented warm with bread yeast.

We decided on a clean version for our third variation, a hybrid brown porter-kvass. English porters historically got their bread crust character from brown malt. By adding a loaf of pumpernickel bread as well we aimed to enhance this character. We also increased the hopping rate and fermented with ale yeast to prevent souring. I infused half of the batch with a caraway tea at bottling to boost the bready impression.

These three beers are only the beginning of the flavors you can play with in kvass. Let it be an arena of the imagination – think black bread, honey, juniper berries, ferment with a sourdough starter, etc.

Beaver Brewing Kvass

While East End’s beer and our variations were inspired by kvass, they are considerably stronger than any of the traditional versions. Despite being located in the same state as East End, Dan Woodske, who runs the Beaver Falls nano-brewery Beaver Brewing Company and wrote Kvass: History, Health Benefits, & Recipes for the Russian Bread Drink (Volume 1), had not tasted Smith’s kvass before deciding to brew his own. Woodske’s version is more reverent of traditional homebrewed versions, complete with an ever changing recipe.

Beaver Brewing Kvass, and a few of the ingredients.Even though Woodske brews on a 1.5 bbl (1.75 hL) brewing system, he brews his kvass in 15.5 gallon (59 l) batches. Rather than spicing with caraway, he flavors his version with lemon juice and raisins. For each batch he adds four or five loaves of bread, which he slices and then stales for several days, to the boil. Woodske adds the legal minimum amount of barley malt for the brew to be beer under American law. Along with the pale malt he usually adds either wheat or rye malt. Four or fewer IBUs from Hersbrucker, or another low alpha acid variety, are added to the boil.

The juice, about one lemon per gallon (3.8 l), and whole raisins are added to the fermentors along with a small pitch of dried bread yeast. Woodske has tried spontaneous fermentation before, and noted that adding yeast shortens the fermentation considerably. The beer is open fermented in homebrew-sized plastic buckets left near a window to keep them warm. Developing light-struck (skunked) flavors is not a major concern because of the low hopping level.

Woodske’s monthly batches are intentionally variable, including different types of bread (e.g., rye, pumpernickel, and sourdough), and gaining a variable amount of sourness from the open fermentation. He also alters the lemon character by sometimes adding the juiced halves for the last few minutes of the boil, but no more than five minutes because he has found that longer times impart a pithy bitterness.

Beaver Brewing Kvass is only available on draft or in growlers at the brewery because Woodske feels such a low alcohol beer (typically 1.5-2% ABV) requires a level of explanation that a bar would not provide. His proudest moment for the beer was serving it to a man who had lived in Soviet Russia. This man had stopped drinking kvass in the 1990s when the only ones he could find were the overly sweet versions made by soda companies, like Coca-Cola, who have dominated the market since the fall of communism. Beaver Brewing’s version had the taste he remembered.


Just like anything in brewing sour beers, there are many ways that brewers have discovered to get a job done. Even if brewing traditional kvass does not appeal to you, consider a bread yeast fermentation as a good way to produce a low gravity sour ale or adding bread to the boil as an alternative method to introduce starch without a turbid mash (or to an extract beer). When it is baked, bread develops many of the same melanoidins that malt does when toasted, providing more flavor than adding refined flour or starch directly to the boil. These are just some of the tools you can use to brew something inspired by the kvass tradition, or create a beverage of your own design.


Gene said...

I haven't gotten my druthers up enough to head to Beaver Falls and try his kvass....I'm....scared.....but enticed at the same time.

pizzabeerblog said...

I'm really excited to try brewing one of these once I'm back in the States. I've started doing a lot more baking recently and this will add some nice variety from the regular schedule of bread soup and bread pudding in disposing of stale bits.

I'm thinking about using my sourdough starter, but am wondering about the pitch rate. Scaling the bread yeast pitch down to 5 gallons I get ~0.25-0.3 g. For a loaf of bread that uses 3 g of yeast I would use about 60–120 g starter (depending on its activity), giving me 6-12 g starter. This would be comparable in mass to a sachet of dry yeast, but I imagine the sachet has a much higher density of cells than my starter. I can't do a cell count, but do you think this is a reasonable way to scale things (i.e. based on activity in baking)?

. said...

neither look like kvass.

Think coke, but that caramel copper colour. this is what I have had as Kvass in Ukraine.

Sweet, spicy and really really drinkable. Served from large metal tank on the side of the road, for 8krv for half litre.

The Mad Fermentationist (Mike) said...

I think the difference in appearance is part of the point. These breweries are producing kvass that more closely resembles some homebrewed versions, rather than the sugary caramel-colored commercial versions that are more widely available. It would sort of be like saying stout doesn't look like beer because it is so much darker than the widely available macro-lagers.

TheHairyChef said...

How'd you get on with using your sourdough starter?

I was talking to a friend Abt trying something similar only a week b4 finding this article and realizing this is actually a thing.

I'd be keen to know how anyone went using a sourdough starter and how they controlled the lactic qualities sourdough yeasts have.

Id wondered if temp control wd be important if only using sourdough yeast as this certainly has an impact on acid production when used in breads.

The Mad Fermentationist (Mike) said...

Here is the recipe post for the Sourdough Kvass. If you want acidity, either leave the hops out entirely, or else aim for just 1-2 IBUs. If you want a sourdough fermented without acidity, go for 10-15 IBUs at least (20 would be safer still). Best of luck, and report back if you try it!

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