Hey! Just thought I would mention that if you are trying to avoid tartness that is vinegary, you should simply try to reduce the amount of oxygen available to your kombucha. Treat it like beer! O2 = good in the beginning, bad in the end. Siphon or use a fill tube to fill your bottles. Purge your bottles with co2! Vinegary taste is produced by acetobacter, which thrive in most kombucha cultures due to the open air nature of the ferment. MOST acetobacter need oxygen to produce acetic acid. A good thick scoby prohibits too much oxygen from getting into the primary ferment and turning it into vinegar. After that, it is up to you to prevent o2 from getting in there! Also, if you have been fermenting at too low of a temperature, you could be lacking a healthy yeast colony in your culture. Acetobacter like lower (sub 70 F) temperatures. If your yeast arent healthy enough to take off during the first couple days of fermentation, lactic acid bacteria (labs) and acetobacter can drop the PH and produce an environment that yeast do not want to ferment in. If you do have a good yeast presence in your culture, they will consume most of the initial o2 in your brew that gets there from pouring into an o2 rich container or cooling with non boiled water. AFter that, the scoby will minimize dissolved oxygen as the brew continues. The scoby is the kombucha's barrier to oxygen, allowing an anaerobic and non vinegary ferment to happen.
Ensure warm temperature ferments (use a seedling heating mat this time of year - 80 degrees is not a bad thing for kombucha)
Minimize your dissolved oxygen! o2 rich ferments that are cold or lacking good healthy yeast colonies will produce vinegar booch due to acetobacter.
edited to add:
been drinking. basically i'm trying to say that specific gravity really has no relation to how sour/vinegary your kombucha is. Sourness has to do with acidity, which does not necessitate much of a gravity drop. It is going to have much more relation to each individual's kombucha culture (call it the scoby if you want but thats really a backup source of yeast and bacteria, the scoby is really a bi-product of a healthy colony of yeast and bacteria that comes from the "starter tea" you move from batch to batch and is the culture's effort to block oxygen from ****ing up its anaerobic fermentation by producing a barrier to o2), how healthy the yeast is in that culture, what PH the yeast in that culture can handle, and how much o2 is dissolving into the solution. specific gravity testing is no bueno for determining how sour something is. You should titrate acidity to know the acid content of a beverage.
