Unfiltered and unpasteurized lager beers that originated in the Middle Ages in Germany, kellerbiers ("cellar beers") are incompletely lagered beers that are therefore less carbonated and slightly sweeter than their fully lagered counterparts would be. Kellerbiers can theoretically be produced using any lager-based style, although Helles might be the most common. Their appearance is typically cloudy due to the vitamin rich yeast present in the beer and hopping levels can be fairly significant. These beers are traditionally matured in deep vaults open to the atomosphere (unbunged).
