Apparently, agave syrup is 60-90% fructose. I used C&H Organic Blue Agave, but I don't know what the fructose content was. I've read that fructose becomes acetic acid while glucose becomes gluconic acid. Since one of my goals is to produce a probiotic drink that doesn't taste like vinegar, I want to better understand the process by which acetic acid is formed, and see if I can influence it. Thus, I made a batch of agave kombucha expecting it to taste very vinegary. It didn't.
I'm not sure why this didn't have a stronger acetic flavor than my usual sucrose kombucha. Sucrose is composed of fructose and glucose in equal proportions. I now have a batch brewing with corn sugar. Corn sugar is entirely glucose, so I'm expecting the corn-sugar kombucha to have little or no vinegar flavor. I first tried an all-glucose brew with brown rice syrup, and it didn't turn out so well. We'll see if I have more luck this time.
The study linked above also mentions that fructose is poorly metabolized, which concurs with other reports that fructose takes "considerable longer to ferment". That does seem to have happened here, as this batch to 23 days to complete. Incidentally, after 19 days it was pH 3.4 and tasted sweet. At 23 days it was pH 3.2 and tasted tart and much less sweet. It could have gone longer, but I was all out of kombucha to drink!
I tried to be more aware of pairing sweet flavors with a tart kombucha. I drank one quart plain, and made one each with Earl Grey and Sugar Cookie Sleigh Ride. After steeping for 1 day, I pulled out the tea bag. The earl grey is a better flavor. I'm developing a collection of holiday-themed tea bags that are okay, but not great. They've been clearance purchases so I suppose it's no big loss if they get thrown away, but I might as well keep them in case I run out of better options.
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