Kombucha is made by fermenting tea and sugar with SCOBY (Symbiotic Culture of Bacteria and Yeast). The FDA Food Code guidelines allow for up to a 10 day fermentation, as continued fermentation beyond that can lead to acidity levels that may be harmful for consumer. In general, the pH levels of kombucha need to be tightly monitored and controlled for safe production. After fermentation, some companies add additional sugar or other flavoring like fruit juice.