Rooibos Kombucha: Better… Stronger… Faster!

Well, okay, it’s certainly better and stronger than last time, but it took longer to achieve it. When I made rooibos kombucha two months ago, it pretty much tasted like slightly-sour rooibos tea, and the sourness it had wasn’t the usual acetic tang. I wrote that I would try it again, letting it ferment longer.

This time I steeped 2 tablespoons of rooibos in 1 pint of boiling distilled water for three hours (until it was cool). Then I added 1/4 cup white sugar and 1/4 cup strong (pH 2.8) kombucha tea from my scoby hotel. Like last time, the scoby was minimal, growing ~1mm every two weeks. Here’s how it changed over time:

  • 2 weeks: pH 3.6, slightly sweet with a strong rooibos flavor.
  • 4 weeks: pH 3.2, slightly sweet/sour, with a mild rooibos flavor.
  • 6 weeks: pH 3.0, slightly sweet, with a clear fermented sourness, but without any rooibos flavor.
  • 8 weeks: pH 2.8, slightly sweet, strong sourness, and a rooibos odor without any rooibos flavor.

The development pretty clearly followed my first batch. The scoby was minimal, and the acidic flavor was not that of acetic. Rather than vinegar, it reminds me of very strong lemonade with a wee bit of acetic bite in the back of the throat. I like really strong lemonade, and I liked this a lot.

It’s unusual (for me) that this retains the scent of the original tea. I’m guessing that I would also taste it, if it wasn’t for the unusually-high acidity overwhelming the tea flavor. Given the pH of 2.8, it’s surprisingly drinkable. I find it fascinating that the nitrogen source (tea) appears to have had a significant impact on the type of acid that was produced. I wonder if that was a function of the nutrients it contains, or a rooibos-native microbe.

Based on my lemonade impression, I’ll guess it produced citric acid; next time I’ll make a 1 gallon batch and sample it with different diluted acids and try to identify the acid. I’ll probably stop it a little sooner (pH 3.0) and try to confirm my suspicion that the acetic acid develops later when conditions are inhospitable for bacteria other than acetobacter.

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