Sauerkraut

Sauerkraut is finely cut raw cabbage that has been fermented by various lactic acid bacteria. It has a long shelf life and a distinctive sour flavor, both of which result from the lactic acid formed when the bacteria ferment the sugars in the cabbage leaves. Although it is considered a national dish in Germany and is known under its German name in English-speaking countries, it did not originate in Germany and is also a traditional and ubiquitous dish in Central and Eastern Europe.

Source: Wikipedia