Short answer: not as your main base, so add it at bottling
Earl Grey is black tea flavored with bergamot oil, and that oil is the main concern. Most guides advise against brewing the first fermentation with Earl Grey. Some experienced brewers report success, but results vary, so the safer approach is to use a plain tea for the main ferment and add Earl Grey at bottling.
What is in Earl Grey
Earl Grey is a black tea flavored with bergamot, a citrus fruit. The flavor comes from bergamot oil. Essential oils like this can have antimicrobial effects, which is one reason brewers are cautious about them around a living culture.
Why brewers worry about it
Oils do not dissolve in water the way tea compounds do. They can collect on the surface of the batch, and they may interfere with how a SCOBY forms and ferments. Some brewers report that a culture grown on oil-flavored tea became weaker or behaved differently over several batches. That is the main reason experienced brewers keep flavored teas out of the first fermentation.
The same concern applies to other oil-flavored teas, such as chai. Plain black, green, white or oolong tea avoids the issue.
What the evidence and experience show
There is little formal research on Earl Grey in kombucha. Most of what we know comes from brewer experience, and that is mixed. Some brewers report batches made with Earl Grey for a long time without problems. Others report a weakened SCOBY, or a culture that ferments more slowly. Because the outcome is uncertain, a backup culture is a sensible precaution.
Safer ways to use Earl Grey
- Brew the main ferment with a plain tea. Use black, green or oolong, as in how to make kombucha tea.
- Add Earl Grey at bottling. Brew a small amount of Earl Grey separately, let it cool, and add a little to each bottle before sealing, as in a normal second fermentation. Keep the tea out of the jar with the SCOBY.
- Or add a citrus note at bottling. A small amount of lemon juice or orange juice gives a similar bright, citrus flavor without oil. Start small and taste as you go.
- Keep a backup culture. If you do try Earl Grey in the main ferment, keep a spare SCOBY and some starter tea that have never been exposed to oil. If the main culture struggles, you can restart from the backup.
Whichever method you use, add the flavor to the bottle, not to the batch that will ferment with the SCOBY.
Warning signs
Discard the batch and do not drink it if you see any of these:
- Fuzzy mold in blue, black, green or white
- A sour or yeasty smell that is off, or a smell like nail polish
- A SCOBY that becomes thin, slimy or breaks apart and does not recover
- Fermentation that stalls for many days
Brown or stringy strands are normal yeast, but fuzzy or colored mold is not. See how to tell mold from a healthy SCOBY.
Bottom line
You can use Earl Grey in kombucha, but it is best added at bottling rather than brewed into the main batch. If you do test it in the first fermentation, keep a backup culture and watch the batch closely. For a fuller set of choices, see the best tea for kombucha.