I know many people are wondering about this, because they want to limit their sugar intake and think this may be a way to do it. The big question is whether the yeast and bacteria in kombucha can actually use the erythritol or stevia as a carbon source. Everything I’ve read says that they won’t, but there are yeast and bacteria that will ferment stevia, and I’ve found one reference to a bacteria that will ferment erythritol. The big question is whether any of those yeast or bacteria are in the kombucha culture. I used 1/2 cup of stevia-blend sweetener in place of the usual sugar in a 1 quart micro-batch of my usual kombucha to find out.
- 6 days: pH 4.4. There is thin scoby, but it doesn’t really look like there’s much happening.
- 13 days: pH increased somewhere over 4.4, and it tasted obnoxiously sweet. No real change in the scoby.
In short: it doesn’t work.
Everybody’s kombucha culture is a little different, but mine doesn’t appear to be able to use erythritol or stevia. If you think your might contain just the right microbes for this to work, give it a try with a spare scoby. If you really need to limit your sugar consumption, I’d suggest reducing the amount of sugar you start with. Your kombucha really only needs to start with enough sugar to allow the microbes to continue working until it’s reached the level of acidity that you want. I’d suggest starting at half-sugar, and if that gets sour enough, try quartering the sugar. I’ve determined that zero-sugar won’t work, so you just need to keep tweaking the sugar content until you eventually reach the goldilocks zone and it’s just right. Too little and it won’t get sour enough, but with too much it can get too sour (and have excess sugar).