Avoid Moldy Kombucha
Finding mold on your kombucha brew is always a sad day. The good news is that kombucha mold is rare. In fact, most mold concerns are simply new kombucha brewers mistaking healthy SCOBY formation for mold. If you find yourself looking at your kombucha brew, wondering if what you are looking at is mold, it’s probably not. When you have mold, You WILL KNOW immediately. Kombucha mold is the same mold that grows on bread, so we have all seen it a million times. So If you’re unsure, the odds are in your favor, it is MOST likely not mold, but a pellicle, SCOBY, forming. If the word pellicle is new to you, be sure to check out our post, What is a SCOBY? for clarification. SCOBY or pellicle growth is rarely uniform and can start forming as a paper-thin, possibly a slime-looking layer, or may resemble circular patterns that mold spores make. Every batch will look a little different, so give it some time; the dots will soon begin to look more like the pellicle you’re expecting.
So what are the practices to keep your kombucha brew healthy and mold-free? The good news is it’s relatively easy. Moldy kombucha can be avoided with a little bit of care and prevention.
Picking The Best Spot For Brewing Kombucha
Location, location, location. During fermentation, the best spot for your kombucha brew is a warm place between 75-85F away from direct sunlight and moisture. The number one mistake that new brewers make is brewing kombucha in cold environments, especially under 70F. A cold temperature causes the culture to be less active; less activity slows fermentation and may result in your culture losing its dominance over other organisms. I cannot stress enough the importance of keeping your brew warm; cold temperatures are nearly always the catalyst for unsuccessful brews. If you insist on brewing in cold temperatures, you shouldn’t expect the batch to finish quickly; you should prepare for longer fermentation times, adding days and weeks to the time needed for your batch to complete fermentation. The moisture aspect is also crucial because mold is attracted to moisture and will be more prominent in areas such as under the sink or near the stove. Any spot with plenty of airflows that isn’t too moist will work, and yes, the countertop is fine. If you have a location that checks all these boxes, you are on the road to easy brewing.
Brewing Kombucha in a Clean Environment
Mold spores, just like bacteria and yeast, are omnipresent in our world and are one of the main forces we combat to maintain cleanliness in our lives. It is important NOT to give mold an upper hand and properly sanitize your vessels, tools, and counter space before brewing. You can do this by using soap and hot water, a vinegar and water solution, or Star San, a popular home brewing acid sanitize. Since I do a lot of brewing, I use Star San and keep it readily available in a spray bottle nearby. Even if you don’t do a lot of brewing, it is nice to have around to clean your wooden utensils and cutting boards; anything bacteria can seep into. If you do use soap and water, try a natural product as many soaps leave residue on the surface that can interfere with the health of your SCOBY.
Ensure Proper pH in your Kombucha Brew
A low pH is generally unfavorable for mold. The kombucha brew often starts at or below 4.5, and kombucha is considered finished between 2.5 and 3.5 pH. Britannica’s encyclopedia has an interesting article on fungi that covers the optimum pH range for mold growth which is 3.5-8 pH. So it is difficult for mold to grow on solutions with a pH lower than 3.5. So the more active your culture, the faster the fermentation, and the faster the pH will get below 3.5 pH, another reason why temperature is essential. Ph can easily be determined with kombucha pH test strips. So always ensure your brew starts at the proper pH. You achieve this by adding 10 percent starter tea to your brew, or 12 oz for every 1 gallon. If this concept is new to you, be sure to check out our post here, which goes over the ratios for all kombucha ingredients. Starter tea is simply aged kombucha tea, and our SCOBY comes packaged with enough liquid to brew mold-free safely. If you cannot locate starter tea and all out of options for some reason, you can substitute 2 TBSP of distilled white vinegar that will do the trick- never use raw or live vinegar.
Last, mold will have a tough time taking hold if you disturb the surface. If you periodically give the surface a swirl with a clean spoon of sorts, you will disrupt any mold spores in the brew. This will also disrupt pellicle formation early on in the brew; this isn’t important but just something for new brewers to note. Stirring the brew isn’t necessary if you’re brewing in a warm area, but it may be beneficial if you’re brewing on the cold side. If you follow these guidelines, your success is nearly guaranteed. If you do find mold, always throw it out and start over. If you have one, this is when a backup culture or a SCOBY hotel becomes a clutch addition to your fermenting toolbox. Check out my post on making one if you don’t know what a SCOBY hotel is!
I bought a Scoby from your site, followed directions and at around the 7 day mark noticed a scum forming around the outer edge of my jar. It didn’t look like mold so I left it. At 11 days the scum looking stuff was about 1 1/2 in thick around the edges. I stored the mixture then strained it. I don’t know what it is suppose to taste like but it tasted like my sugar tea used to when I let it sit to long without drinking it. Also it didn’t get a ‘ baby ‘ Scoby. Wasn’t it suppose to ? Wondering what I did wrong.
What is the room temperature that you keep it at? If it is too cold, the fermentation process will be halted. By too cold, I mean below 75. Not sure what the scum would be, other than an odd-looking scoby forming but the scoby should be somewhat uniform and grow on top.
The section about Step 2: Ensure a low pH. You say you can substitute 2 TBSP of distilled white vinegar and that should do the trick. Can I use Bragg’s Apple cider vinegar “With the Mother” instead?
Apple cider vinegar can contain “vinegar eels” that are harmless to humans but over time can harm your SCOBY culture. If you’re pH is not below 4.5 from the beginning, you should use plain distilled white vinegar to lower it. For future brews, you’ll just use more starter tea from your previous batch.
Hey Ruthie~ I an new to Kombucha but have had some recently and love it! Was told how easy it is to make` so I have gallon glass jar for tea and a smaller jar for baby…I have my 16 oz glass beer bottle with snap lids…so I am getting ready…one question I have …after I order a scoby with the starter and put in my tea and let it sit for 7-10 days…if it works…I will end up with 2 scoby s right…(so I put both in the smaller glass jar.. with some of the tea .does it go in the refrig or back in a dark spot??? for tea at a later time??? thank you so much for any help Shelia/VA
Every time the surface of the tea is disturbed, a new SCOBY will begin to form on the new liquid surface. You don’t necessarily have to separate the SCOBYs every time, but once your jar becomes crowded you can move the older SCOBYs to a “hotel” in a separate jar with a little tea in it. If you want to take a break from brewing, keep the jar at room temperature with enough liquid to cover the SCOBYs. Every now and then you will want to swish it around so the liquid makes contact with the top of the SCOBY–otherwise you could run into issues with mold.
I’m new to Kombucha, bought the scoby through y’all (amazon) and I was going to have a taste today (day 9) and think I see mold. I’m so bummed! It’s on top of the newly formed scoby (your scoby is still at the bottom of the container). I have a decently established scoby formed at the top, with an occasional brownish slimy looking thing under the scoby, but the mold looks like a small fuzzy spot, mostly white but with a green center, raised, dry. Room temp is 76 degrees and pH is about 3.5. I read this post and, while I didn’t inspect it thoroughly in the last couple of days I believe this appeared well after day 3. Should I toss it? Give it some more time?? TIA.
Hillary, can you send me a photo to firstname.lastname@example.org so I can take a peek?
I have Heinz pure vinegar. 5% acetic acid by volume. Can I use that to reduce the pH of my kombucha? I live in a rural area and i could not find distilled vinegar in my store.
The best way to lower your pH is to use more starter tea. If you don’t have more starter, then you can simply make a smaller batch so that your ratio is higher. The only reason to use vinegar is if the ph of your water source is particularly high or if you don’t have any starter tea to begin with.