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Is my Kombucha MOULDY? 5 top tips to prevent mould in your brew!

One of the most frequently asked questions amongst kombucha homebrewers when they are just starting out is: IS THAT MOULD!?

We get it!  It's scary! In reality this very very rarely happens as Kombucha cultures naturally have antimicrobial properties.  However, in some circumstances where the kombucha culture has not been given a chance to grow and thrive, for example if you are just starting out your homebrew with nothing apart from a blob of SCOBY (symbiotic culture of bacteria & yeast)...then it can happen :( 

First things first - if you DO find mould growing in your kombucha jar - THROW IT OUT and thoroughly clean and sterilise all of your equipment! Do not risk further cross-contamination - or worse - health risks by trying to salvage the SCOBY.  It's simply not worth it!

How can you tell if it's mould? The SCOBY is a funny looking thing, and the yeast underneath it in particular can look a bit scary.  But one thing is certain: it's not mould unless it is DRY.  If you shine a light on it and it's glossy/wet - it's not mould. Mould is always dry (therefore it has to be at the top not underneath the starter liquid), and most of the time it's a bit furry and almost always grow in circular clusters.  
Healthy SCOBY can have holes in it, and have green bits in it (often it's bits of tea or yeast), and grow in lumps.  Unless it's dry - it's not mould!
So Good Kombucha UK - not mouldy kombucha
Occasionally though, you can have a pot of kombucha contaminated with Kahm yeast. It's got a matte finish and smells very yeasty (google it!) - it's not unsafe to consume but unfortunately it will mess with the taste of the kombucha so you are better off throwing that out and starting again as well :(. 
SO...what are the 5 top tips to ensure that you won't get any mould in your kombucha?!
1. Make sure there's enough starter liquid in your tea + sugar + starter blend so that the PH level of the blend is below 4.  If you don't have a PH meter you can buy some PH testing strips online for a few quid - worth investing in for your peace of mind!  As a rule of thumb your starter volume should be at least 10% of the volume of your final blend to ensure that the PH level is low enough such that it creates an environment where no mould could grow! As your SCOBY grows it's a good idea to "wet" the top surface every now and then with a sterilised spoon to ensure that it doesn't dry out. 
2. Check that there is sufficient airflow!  The fermentation process requires oxygen so to ensure that your SCOBY is happy and healthy it's best to put it somewhere where there is good airflow.  However, do not put your kombucha brew near house plants to avoid airborne contamination! 
3. Keep your brew warm in the winter - good temperature to aim for is around 25-26 C (degrees Celsius). This keeps your SCOBY nice and happy :)
4. Ensure that your equipment, kitchen environment, and hands are thoroughly clean and sterile through the brewing process!  Distilled vinegar is a good cleaning agent - but please do not use raw vinegar or your brew can get contaminated with vinegar eels (!!!) 
5. Scale up SLOWLY !  If you don't have enough starter, then start with a smaller jar to ensure that your PH level is low.  A SCOBY will form and you can use that (and the starter) to brew a bigger jar of kombucha.  

So there it is - happy brewing! I hope that helps.

A reminder - if you have followed all these advice and still find that pesky mould in your kombucha - do NOT try to salvage your brew!  Throw it out and start's certainly not worth getting ill over! 

Please also be aware that under the homebrew environment kombucha can contain quite high levels of alcohol so please be careful and consult with your GP before consuming if you are pregnant, breast-feeding, or alcohol intolerant in any way.

Finally, if you have any questions about whether or not your brew is mouldy - feel free to email and send us some pictures at  we'd love to hear from you!

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