Gluconacetobacter xylinum (formerly named Acetobacter xylinum) has been established as a defining microbe in kombucha. It’s also been demonstrated that in a high-glucose environment, Ga. xylinum produces less cellulose (scoby) and more gluconic acid. This prompted me to make a batch of kombucha with twice the usual sugar (2 cups/gallon).
After 23 days it was pH 3.4 and I bottled it. Unfortunately, I discovered after bottling that while it doesn’t have noticeable acidity, it is still quite sweet. I attempted to balance this sweetness by using flavorings that were not. I bottled one quart with Decaf Mountain Chai, one with Lemon Ginger, and one with Roasted Chicory. As usual, the base flavor simplified after refrigeration, but a 1/4 tsp malic acid and a dash of Angostura Bitters made a glass of plain pretty tasty.
After steeping for 1 day, the chai bottle is still too sweet, but it better than plain. The Lemon ginger flavor is subtle but the sweetness has taken on a distinct honeyness. The Chicory is the most balanced of the three, but would probably have been better with less steep time. I’ve left the first two steeping for a another day to see if they improve.
I don’t have the ability to tell how my the production of gluconic acid was in relation to acetic acid, but my little experiment did seem to mirror the study’s depressed cellulose production. This batch grew the thinnest scoby I’ve seen in any of my gallon jars, and the thinnest of any experiment that I actually expected to produce a viable culture. Incidentally, I think this is viable, and probably would have been fine if I had let it ferment even longer. I’m learning that it is hard to get an accurate feel for the sweet/sour balance from the contents of a straw. I may need to find a large bulb syringe or an auto-siphon for pulling larger samples. Anyone have a spare refractometer I could use to actually measure the sugar content? Not that sugar concentration will directly translate to taste (fructose is twice as sweet as glucose, and the sweetness of glucose is reduced by acetic acid), but it would at least give me another data point, and it might give me a ballpark guide that’s close enough.
It only seems fitting to follow this up with a batch of kombucha with half the sugar.