The “sugar post”. I should really have more references, even it’s just a URL where I read about different things, but I wasn’t taking notes. Sorry.
Virtually all kombucha recipes call for sucrose (table sugar), though some call for brown sugar, sucanat, or other things that are still basically sucrose. Some even call for maple syrup, honey, molasses, etc. Chemically, sucrose is almost a 50/50 split between fructose and glucose, and the same is pretty much true for most natural sweeteners, including more exotic things like date sugar or coconut sugar (though not stevia, which is magically sweet without sugar). This means that, chemically, the difference these things will make in the final brewed kombucha will primarily come from whatever additional things (impurities) happen to be flavoring the sugar you use.
However, there are some exceptions to the typical fructose/glucose mix. Malt syrup is made of maltose and similar saccharides that break down into glucose. Brown rice syrup and malt extract are composed of glucose. Agave syrup is mostly fructose. Why does this matter? Well, apparently different saccharides are consumed by different yeast/bacteria, and those organisms have different byproducts. I don’t know if the information all comes from the same source, but I’ve read in a few places about the effects of different saccharides on the kombucha fermentation process. The theory is that fructose turns into acetic acid, and that glucose turns into gluconic acid and other acids that are more desirable (search for “glucose” here), or at least less vinegar-like and more generally palatable.
So the take-away is that If you want your kombucha to resemble vinegar, make it with Agave syrup (or pure fructose). If you want to minimize your kombucha’s resemblance to vinegar, make it with glucose. This might make it less complex due to the lack acetic acid, but it seems plausible that the flavor could become more complex due to the fact that acetic acid isn’t drowning out flavors that are more subtle or found in lower concentrations. In particular, I’ve read that there’s no direct correlation between sourness and acidity or acid concentration. People will find acetic acid more sour, and usually more disagreeable, than many other acids, so reducing acetic acid is an interesting goal when experimenting with taste.
To this end, I made a batch of kombucha using brown rice syrup as the sugar. If you’ve ever used brown rice syrup, you know that it’s very thick, sticky, and opaque. I hadn’t really appreciated that this means the syrup contains a lot of solids. Unfortunately, the yeast and bacteria didn’t break down the rice solids, at least not enough to keep the final product from being rather cloudy with a lot of fine sediment. There was a lot “gunk” in the jar too, but that was easily filtered out. I may try to rig up a paper filter to see if that’s effective. I also wonder if there are any relevant wine/beer techniques for clarifying this that wouldn’t counteract the healthful qualities of the kombucha. This calls for more research!
Some future batch will use dextrose for the sugar. It’s still glucose, but without all of the extra non-sugar solids of the brown rice syrup. Theoretically, pure corn syrup could work, as it is mostly glucose, but most modern corn syrup has fructose added, and I’m not sure there’s a reliable way to tell which is which.
The brown rice kombucha did produce a nice, thick scoby. However, since I haven’t had any problem with this, it doesn’t make for much of a selling point. Also, I’m not a big fan of the flavor. It seems a little salty, and maybe more bitter? Incidentally, I’m lacking two of the three genes associated with the sensation of bitterness, so it’s probably worse than I realize. Since I’m starting from such a questionable base flavor, I bottled one quart with a peach tea bag and another with a pomegranate.
This leads me to a mention of the flavors I used last time. Peach has been my favorite, with pomegranate a close second. I underestimated how much SPICE I’d get from “orange spice”, and while it was drinkable, I didn’t really enjoy it.
With the bottling of the brown rice batch, I started my next. This is a standard long-steep and white sugar brew, but with an unusual tweak I’ll detail later. The temperature is dropping at night, so I may need to pull out a heating pad to keep fermentation moving along. I got four new gallon jars, and I have at least four viable scobys, so the pace of experimentation may pick up.
This is probably my most-read post on Kombucha. I’d really like to know if you’re here by looking for kombucha made with brown rice, kombucha made with brown rice syrup, or just the commentary on sugars. I would appreciate it if you would leave a comment letting me know. Thanks!