Kvass is the everyday fermented drink of Russia, Ukraine, Belarus, Poland and the Baltic states: dark rye bread (or rye malt) steeped in water, sweetened and fermented by yeast and lactic acid bacteria. It’s brown, lightly sour, slightly sweet and gently fizzy, and it tastes of dark bread – closer to a very light beer than to a soda. It’s also one of the easiest fermented drinks to make: the recipe below takes about an hour of work and two days of waiting.
What Kvass Is
Kvass is one of Europe’s traditional low-alcohol fermented cereal drinks (Baschali et al., 2017). It’s made from dark rye bread, rye flour or malt, water and sugar. When researchers analyzed a commercial kvass, they found three main microbes, each at tens of millions of cells per millilitre: the lactic acid bacteria Lactobacillus casei and Leuconostoc mesenteroides, and the yeast Saccharomyces cerevisiae. Between them they produced ethanol, lactic acid and acetic acid (Dlusskaya et al., 2008). That mix gives kvass its fizz, sourness and small amount of alcohol.
It goes by many names: kvas (Russian and Ukrainian), kwas chlebowy (Polish) and gira (Lithuanian).
Kvass in Eastern European Life
Kvass has been brewed at home in the region for centuries, as a way to use stale bread and as a summer refreshment. In Soviet times, and still in many Russian and Ukrainian cities, it was sold on the street from yellow barrel-shaped tanks (bochki) and poured into cups.
It’s also an ingredient: okroshka is a cold summer soup of chopped cucumber, radish, green onion, boiled potato, egg and dill, with or without meat, in chilled kvass (some families use kefir instead).
Bottled kvass is widely sold, but it’s often filtered or pasteurized; homemade kvass is cloudier, livelier and more sour.
Beet Kvass Is a Different Drink
“Beet kvass” isn’t made from bread at all. It’s beets fermented in salted water, and it’s salty and earthy rather than malty. See our beet kvass recipe. For a thick, sour beer made from lightly baked bread and malt, see Egypt’s bouza.
Tips for Good Kvass
- Toast the bread dark. Very dark toasting (without burning) gives kvass its color and deep, malty flavor.
- Use a little yeast. Toasting and boiling leave few live microbes, so traditional home recipes add a pinch of yeast or a spoon of sourdough starter. Raisins alone are unreliable.
- Keep it short. 1–2 days at room temperature is usually enough. Longer makes it more sour, more alcoholic and more likely to turn vinegary.
- Be careful with sealed bottles. Bottling for extra fizz builds pressure fast. Use bottles made for carbonated drinks, check one daily and refrigerate as soon as it’s fizzy.
- Drink it fresh. Refrigerated kvass keeps changing; it’s best within a few days.
Troubleshooting
- No bubbles after a day: the room is too cool or the yeast was inactive. Move it somewhere warmer (68–75°F / 20–24°C) or add a fresh pinch of yeast.
- Too sweet: ferment a few hours longer, or use less sugar next time.
- Too sour or vinegary: it fermented too long or too warm, or it was left open to the air.
- Bland: toast the bread darker and use a darker, denser rye bread.
- Mold: throw out any batch with fuzzy mold (white, green, black or pink). Stir the bread under daily while it ferments and keep everything clean.
Variations
- Mint or raisin kvass: add a few mint sprigs or raisins when bottling.
- Fruit kvass: add a handful of berries or a little fruit juice at bottling.
- Honey kvass: replace some of the sugar with honey (not for babies under 1).
- White kvass: made with lighter bread or flour for a paler, milder drink.
More fermented drinks: fermented drinks like kombucha, the Balkan millet drink boza and the Andean corn beer chicha de jora.