Mould is a tricky one, its hard to spot and comes in many shapes and sizes. However it generally has some very distinctive traits:
• Its furry and dry
• It lives on the pellicle (not in the liquid)
It usually occurs during the early stages of a new batch because this is when the SCOBY is most diluted from the new water/tea/sugar mixture. This dilution raises the pH level to above 4.0 which is the danger zone for mould to start to grow. Generally when Kombucha is finished brewing it is somewhere around the 2.5-3.0 pH range.
Therefore if our pH is in the danger zone for a few days, any impurities from improper cleaning or contamination are going to put the batch at risk of growing mould.
If you suspect you have mould, you should never consume the beverage. If verification of the mould is difficult, the best thing to do is wait and see because mould grows and gets worse with time. As mould gets worse - its usually gets easier to identify.
Once you have identified mould, the entire batch needs to be disposed of and start again (see our Golden Recipe) - making sure to clean everything very well.
Happy brewing
Chris