CLAY COUNTY – Kombucha, a fizzy drink made from fermented tea, used to be found only at specialty stores. But today, many grocery stores carry an array of kombucha products.

Both consumers and kombucha brewers are driving this trend, said Katherine Thompson-Witrick, an assistant professor in the UF/IFAS food science and human nutrition department where she studies the complex chemistry of fermented beverages.

“Kombucha contains probiotics and antioxidants, which appeal to consumers looking for a health-promoting product, though it’s worth noting that more research needs to be done to identify how different processing methods impact the health benefits of kombucha,” Thompson-Witrick explained. “At the same time, kombucha brewers have adapted more traditional kombucha formulations to be more approachable in flavor and drinking experience.” Thomspon-Witrick and others recently published a review article in the journal “Food Chemistry Advances” on the history of kombucha and how its ingredients influence the final brew.

Below Thompson-Witrick answers some common questions about kombucha.

What is kombucha?

“Kombucha is a fermented beverage made with water, tea, yeast, bacteria and sugar. Sometimes other ingredients are added, but that’s the basic recipe. Historians think kombucha probably originated in China and has been consumed in various parts of Asia and Europe for centuries.”

What is fermentation?

“Fermentation is a method of preserving food that’s been around for millennia. Many familiar foods are fermented—yogurt, sourdough bread, beer, wine, kimchi and sauerkraut are just a few. Fermentation happens when microbes such as yeast or bacteria break down sugar molecules into acids, alcohols, carbon dioxide and other substances. Fermentation changes pH, making the fermenting food or beverage inhospitable to microbes that might make us sick. The yeast and bacteria will also outcompete potentially harmful microbes. As a result, fermented foods have a longer shelf life, which was very important in times before refrigeration. Today, fermentation is appreciated as a way to develop unique flavors and other properties in food and beverages.”

How do the ingredients in kombucha contribute to its flavor?

“Just as with wine and beer, what goes into kombucha affects the end result. The tea used in kombucha can add bitter flavors, depending on the type of tea. During fermentation, yeast produces acetic acid, which makes kombucha sour. Alcohol is another product of fermentation and contributes to the flavor and aroma of kombucha (note: commercially produced kombucha is capped at .5% alcohol by volume). Fermentation also produces carbon dioxide bubbles (carbonation) and some kombuchas are force carbonated as well. We know from research that carbonation affects how we perceive a beverage’s aromas and flavors.”

What’s that stringy stuff you sometimes see floating in kombucha?

“That stringy stuff is probably from the SCOBY – symbiotic culture of bacteria and yeast – used to brew the kombucha. Most of the SCOBY lives on top of the kombucha as it ferments and looks a little like a mushroom cap, but some of it can end up elsewhere in the batch as those strands. Some kombucha brewers will filter out these bits of SCOBY before bottling, so that’s why you might not see it in all products.”

What future research would you like to do on kombucha?

“My background is in beer making, so I’m excited to diversify my lab’s research by studying kombucha. At the moment we’re interested in how the method used to steep the tea impacts a kombucha’s chemical make-up and flavor characteristics. We are comparing the typical steeping method – using boiling water – with steeping at room temperature.”