THE SCIENCE BEHIND KOMBUCHA [fermentation, symbiosis, and types of microbes; science of food]

Summary

In this episode of Bite Scized, Kate dives into the world of kombucha, exploring its fermentation process and the key roles bacteria and yeast play in transforming sweet tea into a tangy, fizzy drink. With insights from expert Molly Leavens, the episode highlights the importance of the SCOBY, the microbial community, and how they work symbiotically to create the distinctive flavor of kombucha. Viewers also learn how to brew their own kombucha at home, troubleshoot common issues, and experiment with flavors and carbonation, offering a hands-on approach to this popular fermented beverage.

Takeaways

• 😀 Kombucha is a fermented tea made by adding sugar to brewed tea, which undergoes fermentation to produce a tangy, fizzy drink.
• 😀 The key ingredient for kombucha fermentation is a SCOBY (Symbiotic Culture of Bacteria and Yeast), which supports the fermentation process.
• 😀 A SCOBY is made up of cellulose and grows as the microbial community inside it thrives, playing a central role in the kombucha ecosystem.
• 😀 The fermentation process is driven by the interaction between yeast and bacteria: yeast converts sugar into ethanol, and bacteria use ethanol to produce acetic acid, which gives kombucha its tangy flavor.
• 😀 Bacteria and yeast work together in a symbiotic relationship, where both organisms help each other survive and thrive during fermentation.
• 😀 Acetobacteraceae bacteria produce acetic acid (which gives kombucha its tangy taste), and they require oxygen to function, unlike lactic acid bacteria that ferment anaerobically.
• 😀 Yeast breaks down sucrose into simpler sugars like glucose and fructose, using them to produce energy (ATP) and ethanol, which in turn supports bacterial fermentation.
• 😀 The SCOBY serves as a physical barrier, protecting the kombucha from unwanted microbes and controlling oxygen flow, essential for the fermentation process.
• 😀 The level of acidity in kombucha is determined by how long it ferments—longer fermentation results in a more acidic and tangy flavor.
• 😀 The flavor of kombucha depends on the type of tea used (green or black) and the fermentation process, with green tea often preferred for a healthier SCOBY and lighter flavor.
• 😀 Flavorings can be added after the primary fermentation process, but fermentation with added fruits or herbs can change the flavor profile dramatically, so timing and experimentation are key.

Q & A

What is kombucha and how is it made?

Kombucha is a fermented tea made by adding sugar to brewed tea, which is then fermented by a symbiotic culture of bacteria and yeast (SCOBY). The fermentation process creates the characteristic tangy flavor and carbonation.

What is a SCOBY and why is it important in kombucha brewing?

A SCOBY, or Symbiotic Culture of Bacteria and Yeast, is a gelatinous mass that facilitates fermentation. It is essential because it provides a stable environment for the microbes, allowing them to work together to turn sugar into alcohol and then into acetic acid.

How does the SCOBY function in the fermentation process?

The SCOBY acts as a home for the bacteria and yeast, supporting the fermentation process. It also helps prevent unwanted microbes from contaminating the kombucha and ensures a controlled environment for fermentation.

What role do yeast and bacteria play in kombucha fermentation?

Yeast breaks down sugar into ethanol (alcohol), while bacteria use the ethanol to produce acetic acid. This mutualistic relationship is key to creating the distinctive flavors of kombucha.

Why is oxygen important for acetic acid bacteria in kombucha?

Acetic acid bacteria require oxygen to oxidize ethanol into acetic acid. Unlike lactic acid bacteria, which ferment in an oxygen-free environment, acetic acid bacteria thrive in the presence of oxygen, which is why kombucha is only partially sealed during fermentation.

How do yeast and bacteria help each other during fermentation?

Yeast produce ethanol during fermentation, which acetic acid bacteria then use to produce acetic acid. This symbiotic relationship allows both microorganisms to survive and contribute to the flavor and fizziness of kombucha.

What factors can influence the final flavor of kombucha?

The final flavor of kombucha is influenced by factors such as the type of tea (black or green), the length of fermentation, and any additional flavors (e.g., fruit) added after the primary fermentation. The longer it ferments, the more acidic and tangy it becomes.

Can kombucha be made without a SCOBY?

While it’s possible to brew kombucha without a SCOBY, starting with one will speed up the fermentation process. If a SCOBY is unavailable, using a store-bought kombucha as a starter culture is recommended to introduce the necessary bacteria and yeast.

What should be monitored during kombucha fermentation?

During fermentation, the two main factors to monitor are pH (acidity) and the condition of the SCOBY. These indicators help determine if fermentation is proceeding as expected.

What happens if kombucha is left to ferment too long?

If kombucha ferments too long, the sugar is completely converted into acid, resulting in a very sour, vinegar-like taste. However, the fermentation can be stopped at any point depending on the desired level of acidity.