What is Kombucha, Really?

Before becoming a staple of Belgian fridges, kombucha travelled far. Across centuries, continents, and questionable marketing claims. Today, the market is booming and while we love seeing our favourite drink gain ground, there is a downside: the shortcuts.

Some brands have quietly reinvented kombucha. Sometimes to cut costs. Sometimes to extend shelf life. Sometimes both. The result? A shelf full of bottles that call themselves kombucha, with very little in common.

So let's be clear about what it actually is.

At its core: fermented tea

Kombucha starts with sweetened tea to which a SCOBY is added. SCOBY stands for symbiotic culture of bacteria and yeast: a small living ecosystem that gradually consumes the sugar, fermenting the drink over one to two weeks, sometimes longer.¹

During fermentation, something genuinely interesting happens. The process produces:

• Organic acids (acetic, lactic, glucuronic): useful for digestion.
• Vitamins B and C: for energy and antioxidants.
• Polyphenols: fermentation actually amplifies the antioxidant power of the tea.²

It is this natural synergy that turns a simple infusion into something worth drinking for reasons beyond thirst.

The problem: no rulebook

If you look for an official legal definition of kombucha, you will not find one. Unlike wine or cheese, the word carries no protected status in Europe.³ Anyone can label their drink kombucha. Which means, in practice, that not everything on the shelf deserves the name.

Pasteurised, filtered, zero-sugar: a quick guide

Because clarity matters, here is what those terms actually mean.

• Living Kombucha: It still contains all its bacteria (acetic, glucuronic, lactic, etc.) and yeasts that are essential for your microbiota. You can also use a bottle of raw kombucha to restart a kombucha culture.
• Pasteurised Kombucha: It has been heated (usually between 60°C and 80°C) to kill all microorganisms. Pasteurisation kills the yeasts and bacteria present in the drink and can alter the taste by slightly cooking the remaining sugars and compounds.
• Filtered Kombucha: In order to make kombucha more appealing to the market, it can be filtered to produce a perfectly clear liquid with no sediment. Various techniques can be used, such as centrifugation or plate filtration. Filtration involves passing the liquid through ultra-fine membranes (0.2 to 5 microns) to separate the components. This removes varying amounts of yeast and bacteria, depending on the filters chosen, thereby slowing down fermentation for greater stability.⁴
• Zero-sugar Kombucha: This is a recent innovation that allows a live drink to be stored outside the refrigerator. Here, the culture is allowed to consume almost all of the sugar. The result is very acidic, and to make it more drinkable, producers often add natural sweeteners (stevia, erythritol). As there is no longer enough real sugar to consume, the yeast and bacteria can no longer work, and fermentation stops. This allows the drink to be stored at room temperature for more than 12 months, making it easier to store on standard shelves.

How to spot the real thing

Since the law does not require pasteurisation to be declared, here is what to look for on the label:

• Sold refrigerated: If it sits on a standard shelf at room temperature, it is almost certainly pasteurised or heavily filtered. Living kombucha needs to be kept cold.
• Explicitly labelled unpasteurised (or: live/active cultures): Brands that do the real work tend to say so clearly. It is something to be proud of.
• “SCOBY” or “kombucha culture” listed in the ingredients: This confirms the drink went through actual biological fermentation. Some products marketed as kombucha are little more than tea extract, acetic acid, flavourings, and additives. The mention of a culture is your guarantee that fermentation happened.

What we stand for

At Smile, kombucha is unpasteurised, unfiltered, free of artificial flavours and additives. That is not a marketing position. It is simply what kombucha has always been, for the past 2,000 years, before the shelf-life optimisations got involved.

Other brands share this commitment, and they deserve support. Not out of nostalgia, but because the drink that actually does something for you is the one that is still alive when you drink it.

We cannot promise you the immortality of Chinese emperors. But we can promise your gut flora will be pleased.

Disclaimer :

‍This article is for informational purposes only and does not constitute medical advice. Kombucha is a fermented drink, not a treatment. If your microbiome has concerns, it should consult a professional, not a blog post.

Sources

¹ Timo. (2025, 23 septembre). Kombucha : tout savoir sur cette boisson fermentée et ses bonnes bactéries. CheckFood. https://check-food.fr/abecedaire-de-lalimentation/kombucha-tout-savoir-boisson-fermentee-ses-bonnes-bacteries/

² Viera de Oliveira, P., et al. (2023). Kombucha benefits, risks and regulatory frameworks: A review. Food Chemistry Advances, 2, 100288. https://doi.org/10.1016/j.focha.2023.100288

³ Règlement (UE) n° 1169/2011. Journal officiel de l'Union européenne. http://data.europa.eu/eli/reg/2011/1169/oj

⁴ Boonsupa, W., & Insumran, Y. (2025). Comparison of Chemical Properties, Antioxidant Activity and Microbial Count in Filtered and Non-Filtered Dry Wolffia arrhiza Kombucha. Pakistan Journal Of Biological Sciences, 28(4), 229-235. https://pubmed.ncbi.nlm.nih.gov/40329752/

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