Kwas (pronounced KHVAHSS ) is the Polish word for a sour starter made by fermenting bread (when it is known as kwas chlebowy) and/or beets (kwas buraków) or other vegetables or fruits. It is used in soup making, especially barszcz or żurek, and some people chill it and drink it.
Kwas Is Popular Throughout Eastern Europe
Known as kwass in English, it is also enjoyed in Russia, Ukraine, and Belarus where it is known as kvas. Latvians call it kvass and Lithuanians say gira. It exists in former Soviet states like Georgia, Kazakhstan, and Armenia, and is even known in China as géwǎsī/kèwǎsī.
Polish kwas dates to 10th-century Poland. It was a common drink among the peasants but eventually became accepted by the szlachta (Polish aristocracy). After the collapse of Communism, kwas as a drink gave way to Western soft drinks and its popularity has waned over recent years. It remains a main component of staropolskie (Old Polish) cooking.
This Eastern European fermented beverage is typically made with black or other rye bread and is imbibed as a thirst quencher in the summer. Although it is fermented, this slightly sweet beverage is considered nonalcoholic (0.05% to 1%). It can be made with the addition of fruits like strawberries and raisins or herbs like mint.
Bread kvas for cooking is made a little differently than the beverage and is used as an ingredient for soups like Russian botvinia and some versions of okroshka (some recipes call for buttermilk in place of the kvas as a souring agent), and for Polish żurek. Beet kwas is used in Polish Christmas Eve beet soup.
A National Beverage
Throughout the summer in the main market squares of largely Eastern European cities, you will see kiosks with brews from small-batch vendors and homebrewers. Each one tries to outdo the other in terms of their displays, many of them looking like oversized barrels or brightly colored tanks from which they dispense their product.
Increasingly, you will find commercially bottled kvas for sale in grocery stores. Purists consider it to be inferior because it resembles soda pop made with carbonated water, flavorings, and malt extract instead of the naturally fermented beverage it was intended to be.