Kvass, the sour bread drink handed out at a prince's baptism in 988
Kvass is brewed from rye bread or rye flour and malt, fermented only briefly, and usually carries between 0.5 and 1 percent alcohol. It arose where grain was too scarce for beer to be an everyday drink, and its first written appearance describes it being served to Kyiv's citizens at Vladimir the Great's baptism.
Nobody knows exactly who invented it. Some Polish sources credit the Slavs, and it may have originated in Kievan Rus', where it was known by at least the 10th century and eventually became an emblem of East Slavic cooking. The Primary Chronicle records it alongside mead and food at the celebrations of 988. Linguists link the name to an ancient Proto-Indo-European word for turning sour, and English first recorded it around 1553 as quass. Poles call it bread kvass to tell it apart from the ordinary word for acid.
Home brewing is simple. Dried rye bread is steeped in hot water and left for 12 hours; sugar and yeast are then added and the mixture ferments for another 12 hours at about 20 degrees Celsius. Factories instead dilute a wort concentrate to 5 to 7 percent sugar, pasteurise it, and ferment it with baker's yeast and lactic acid bacteria for 12 to 24 hours. Only around 1 percent of the extract becomes alcohol, carbon dioxide and lactic acid, which keeps the drink mild; strength occasionally climbs to 2 percent.
Commercialisation came in the late 19th century, when armies, industry and projects such as the Trans-Siberian Railway needed to feed huge workforces. Over 150 flavours were recorded, including apple, mint, raspberry and chicory. Street sellers with barrels undercut domestic brewing, and in the year to 30 June 1912 the Governorate of Livonia alone had 17 factories producing 437,255 gallons. Scientists in Kyiv began studying its production in the 1890s, and Moscow chemists refined mass-production methods in the 1960s.
Today most factory kvass is sold in plastic bottles of 1 to 3 litres that keep for 4 to 6 weeks. It is drunk from Estonia to Georgia, with similar drinks popular in Finland, Kazakhstan and parts of China, and Belarus hosts kvass festivals, the biggest in the city of Lida.
Source: Kvass
