The last time I tried coffee kombucha, I made coffee and then added sugar and water. This time I used 1 quart of strong coffee, added 1/4 cup sugar, and a scoby. Because coffee is relatively acidic all by itself, I didn’t add any kombucha to inoculate it.
The dark coffee made it difficult to read the pH paper and measure acidity.
- 14 days: pH 4.4? This had a strong coffee flavor, with a very slight tartness. There’s a thin, dark scoby.
- 20 days: pH 3.6? There was a medium to strong sourness and a dense, rich coffee flavor. The scoby was thin and weak.
It’s really unusual for kombucha to have any tartness at pH 4.4, so I have to wonder if it was actually lower. I probably should have stopped this sooner. It’s worth trying this with cold-brew coffee, which should have even less starting acidity. I could also give it a go with espresso or coffee from my moka pot.
In my kombucha nutrient experiments, adding DAP seemed to cause the dominant acid to be lactic, which is much milder than acetic. Perhaps I should duplicate this experiment, but with added DAP. The DAP experiment didn’t produce a scoby, but that’s not really a problem here, since this already didn’t produce a viable scoby.
My first time making coffee kombucha also had a thin scoby, and I listed four possible reasons. With this batch I can rule out three of them, which leaves: coffee doesn’t support a strong, scoby-forming culture. Some people report fast fermentation and a thick scoby from coffee kombucha, so what’s different here? It might still be true for some cultures and not others, depending on the exact microbes present. If you have any other ideas, please leave them in a comment.