Commercial Kombucha vs. Homemade: Can Store-Bought Brands Pass the Fermentation Test?

Jo Webster and Caroline Gilmartin are fermentation experts from England. They are active on Instagram as @jo.webster-health and @every.good.thing. They recently posted the results of a fascinating experiment where they tested a range of commercial brands, as well as home-brew, to see if they could use it to make a new batch (as genuine kombucha should.) They published the results on Substack [subscription required – low £20 annual fee to access]. Once you’ve subscribed, click the link above to see the video of their experiment. The following text accompanies the video.

Is commercially-produced “kombucha” real kombucha? During preparation for last month’s episode of Fermentology For Now, Caroline pointed out that, since traditional kombucha-making involves taking some kombucha and using it to inoculate (or back-slop) a batch of sugar-sweetened tea, we should be able to use commercially-made kombucha to make a new batch. We decided to test the commercial kombuchas we had (as well as my home-brew) against this benchmark; if we back-slopped them in to some sweetened tea, would they make genuine kombucha?  

In real kombucha (a brew humans have been consuming for thousands of years), the symbiotic community of bacteria and yeasts is recognisable as particular to kombucha and it is generally a stable community. So batch after batch after batch, real kombucha can be used as back-slop to make more kombucha. And importantly, the kombucha it makes time and time again consistently looks like kombucha, smells like kombucha and tastes like kombucha.

So, the million dollar question was, which of the commercially-produced kombucha we reviewed in our last episode could we successfully use as back-slop to make more kombucha? And how did Jo’s kombucha perform? But also, how do you pronounce petri?! Listen to the episode to find out.

TL:DL (too long:didn’t listen) Summary

• We mixed 200 ml of tea with 200 ml of each test kombucha. We left them with cloth covers at room temperature for 29 days, assessing pH and taste at the outset, day 17 and day 29 and visually assessing regularly. Lo Bros joined late, so fermented for 13 days. Nania’s Vineyard joined later, so only had 7 days fermentation time. 
• A real kombucha should be able to make a fresh batch of genuine and tasty kombucha when used to inoculate (or back-slop) fresh sugar-sweetened tea.
• In a real kombucha, the pH should fall as the brew progresses because of the organic acids produced by the kombucha microbial community.
• Generally, a healthy kombucha will produce a SCOBY; a cellulose mat containing bacteria and yeast (a process often driven by Komagataeibacter bacteria).
• However, low pH and a SCOBY does not a kombucha make. It still needs to smell and taste like real kombucha.
• We tested Remedy, Equinox, Momo, Cidrani, Pure Earth, Lo Bros (2 flavours), Nania’s Vineyard and Jo’s home-brew.
• The only batches that tasted and looked anything like kombucha was Momo and Jo’s home-brew. Nania’s Vineyard joined the experiment late, but had it been given more time, it likely would have come good.
• Save for Remedy and Lo Bros, the pH in all the commercial samples (and Jo’s home brew) DID fall over time. With Remedy, the pH ROSE between days 1 and 17 and only started dropping after that. With Lo Bros, the pH never fell, it rose.
• Remedy, Equinox, Momo, Cidrani and Jo’s home-brew grew some form of SCOBY but only Momo and Jo’s home-brew grew what looked like true vibrantly healthy kombucha SCOBYs. Momo produces commercial kombucha using traditional methods.
• Equinox, Cidrani, Pure Earth, and Lo Bros all had some form of visible mould growth.
• In descending order of kombucha quality:
  • Momo and Jo’s home-brew (and probably Nania’s vineyard if it had had enough time).
  • Remedy
  • Equinox
  • Cidrani
  • Pure Earth and Lo Bros
• Are Remedy, Equinox, Cidrani, Pure Earth or Lo Bros actually producing real kombucha?
• Should there be a new drink with a new name that encapsulates these drinks? Nombucha?
• Kombucha contains a complex community of bacteria and yeast and traditional methods of making it maintains this community. Commercial methods that alter that process to try to better fit a live fermented product into our modern food transport system disrupt the essence of real kombucha; its microbial community.
• The only commercial kombucha we tested that behaved like a real kombucha was Momo.
• There is limited data on the health effects of kombucha in humans (Mendelson et al 2023) and this study was a pilot study with a number of design issues. There is in vitro and in vivo data (Kapp et al, 2018) and this paper (Dimidi et al 2019) is a good review paper of fermented foods, generally. Despite thousands of years of human consumption suggesting people like it, we need more human research into kombucha’s potential benefits, especially given growing understanding of the importance of gut microbiota in health.
• Kombucha is very easy to make at home. And it tastes delicious in its own unique way.
• If you want to test whether the commercial “kombucha” you are buying is kombucha or nombucha, repeat the experiment we did. Even without the pH testing, you will be able to tell if the end product is kombucha or, well, nombucha!!
• Nombucha still tastes nice and is healthier than alcohol.

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Disclaimer

The views and opinions expressed in this guest posting are solely those of the original authors. These views and opinions do not necessarily represent those of this publication.