Kombucha is a fermented beverage enjoyed for its unique flavor and powerful health benefits.

Though it’s widely available at grocery stores and health food shops, you can make your own using tea, sugar and a SCOBY.

A SCOBY is a thick, rubbery and cloudy mass that aids the fermentation process.

This article explains what a kombucha SCOBY is and how to make your own.

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A SCOBY, which stands for “symbiotic culture of bacteria and yeast,” is an ingredient used in the fermentation and production of kombucha.

Fermentation is a chemical process in which carbohydrates like sugar or starch turn into alcohol or acid (1).

The appearance of the SCOBY can vary, but it’s typically dense, round, rubbery and opaque with a mild, vinegar-like smell.

Look out for mold or a strong cheese-like odor, which may indicate that the SCOBY is decaying and needs to be discarded.

The dish-like structure of the SCOBY is comprised mostly of a type of insoluble fiber known as cellulose.

It also hosts a variety of yeast and bacteria species that aid the fermentation process (2).

Other fermented foods and beverages — such as kefir, sourdough bread and ginger beer — require similar symbiotic cultures.

Summary A symbiotic culture of bacteria and yeast, or SCOBY, aids the fermentation process of kombucha.

Kombucha is produced by adding a SCOBY into sweetened black or green tea, then letting it ferment for 1–4 weeks.

The bacteria and yeast in the SCOBY break down the tea’s sugars and convert them into alcohol, carbon dioxide and acids (3).

The result is a fizzy product with a tangy, sweet and vinegar-like taste. Its specific flavors depend on how long it’s left to ferment, the type of tea used and the addition of other ingredients like fruit, juice or herbs.

Fermentation also increases the concentration of probiotics — a type of beneficial bacteria in your gut with many positive health effects.

In fact, studies have linked probiotic consumption to reduced cholesterol levels, improved immunity and enhanced weight loss, among other benefits (4, 5, 6).

Summary A SCOBY, when added to sweetened tea, turns the sugars into alcohol, carbon dioxide and acids. The resultant kombucha contains numerous probiotics.

If you’re interested in brewing your own kombucha, obtaining a SCOBY is the first step.

You can purchase starter kits or cultures online or in certain health food stores.

Be sure to look for an organic SCOBY from a reputable retailer to reduce the risk of pesticide exposure and ensure product quality (7).

You can also borrow a SCOBY from a friend who makes homemade kombucha or join an online community to find a local with a SCOBY to spare.

Because the SCOBY continues to grow with each batch of kombucha, it can be divided and shared by simply cutting off a 1-inch (2.5-cm) piece from the top and passing it on.

Although the risk of contamination is low when properly handled, be sure to discard your SCOBY immediately if you notice mold, an unpleasant smell or any signs of decay.

Summary You can purchase a SCOBY online, find one at a health food store or borrow one from a friend. Though the risk of contamination is low, discard the SCOBY if you notice mold, unpleasant smell or other signs of decay.

It is also possible to grow your own SCOBY.

You can do so by using raw, unflavored kombucha and 1 cup (250 ml) of green or black tea sweetened with 1–2 tablespoons (14–28 grams) of sugar.

Simply combine the kombucha and cooled tea in a jar and cover it tightly with a coffee filter or dishrag.

Place the jar in a warm spot — around 68–80°F (20–30°C) — and let it ferment for up to 30 days. As the SCOBY begins to form, it will gradually become thicker and less translucent.

Once the SCOBY is about 1/4-inch (2/3-cm) thick, you can use it to brew a new batch of kombucha using green or black tea and sugar.

Summary Growing your own SCOBY is a simple process — you only need raw kombucha, sweetened tea and time to spare.

A SCOBY is a symbiotic culture of bacteria and yeast used in the production of kombucha.

You can buy one from local or online retailers or make it at home using raw, unflavored kombucha and sweetened green or black tea.

The risk of contamination is low when properly handled. Still, discard your SCOBY if you notice mold, an unpleasant smell or other signs of decay.

Making or buying your own SCOBY allows you to brew your own kombucha, giving you constant access to a probiotic-rich, refreshing treat.