What Is That Brown Stuff?
If you’ve made kombucha or bought unfiltered kombucha from a store, you’ll likely notice a build-up of sediment at the bottom. It usually looks brown, may be cloudy, or even slimy. Although it may look sketchy, it’s quite normal. Kombucha is a sweet tea that is fermented with a kombucha culture commonly referred to as the SCOBY. The word S.C.O.B.Y. is an acronym, which stands for “symbiotic culture of bacteria and yeast.” If you would like to learn more, the post here covers in detail, “What’s a SCOBY?”
The build-up you see at the bottom of your kombucha is simply an array of yeast and bacteria cells that have settled to the bottom of your bottle or brewing vessel. If you are here because of dark spots at the surface or brown stuff suspended in your liquid, see our post which covers the brown stuff floating in kombucha. If you’re interested in learning more about the kombucha brewing process, check out our article on how kombucha is made.
During the kombucha fermentation, the yeast in the kombucha culture consumes the sugar suspended in the liquid and converts it to ethanol and carbon dioxide. The bacteria then convert that ethanol to various acids, which is what makes kombucha tart. As fermentation progresses and after it’s bottled, some of the yeast and bacteria suspended in the kombucha will begin to settle at the bottom. This is why the sediment is seen at the bottom of both fermenters and bottled kombucha. As the fermenter or bottles sit, yeast and bacteria fall to the bottom. This is sediment you see – a mixture of this yeast and bacteria.