Instead of literally pouring all your hard work down the drain, it’s best to prevent your SCOBY from developing mold in the first place.
According to Preserved Goods, a common mistake among new home brewers that leads to mold is not using enough starter fluid. The starter liquid, he says, is the mature kombucha from your previous batch; the ratio should be two cups of starter liquid per gallon of new tea.
Refrigeration might sound like a good idea for keeping most foods fresh, but with kombucha, the opposite is true. Homebrewer Yea Bucha explains that colder temperatures (especially below 64 degrees Fahrenheit) slow fermentation. Since the fermentation process is what produces the acidic pH that prevents mold from growing, it’s important that your kombucha acidifies quickly enough to stay clean. For best results, keep kombucha at around 70 degrees, via Cultures for Health.
Kombucha’s starting pH should be 4.5 or lower, via Fermentatholics; it will fall between 2.5 and 3.5 after fermentation. For a sweeter taste, it is advisable to aim for a higher pH of 3.5. If you like your kombucha pie, let it ferment longer until the pH hits 2.5 (but not lower). Brew Buch says the mold is most likely on the “early fermentation when the acidity of the kombucha isn’t high enough to repel bad bugs.” If your SCOBY gets moldy, try again!