Kombucha has gone from a weird home-brewed beverage only consumed by health-obsessed hippies (and everyone in Portland, of course) to a popular non-alcoholic alternative to soda. At the heart of this story is the perception of kombucha as healthy, and the relative simplicity of carrying out a kombucha fermentation – make some sweet tea, throw in the “SCOBY” and when it starts to smell vinegary, taste it to see if it’s done. What can go wrong?

As it turns out, the simplicity of the fermentation system relies upon a complex mixture of microbes each needing to do their part. That slimy chunk of cellulose that floats on top of an active kombucha ferment, known as “the SCOBY”, contains bacteria and yeast working together, hence the acronym (Symbiotic Culture of Bacteria and Yeast). The yeast in the SCOBY turns sugar in the sweet tea into alcohol, and the bacteria turn that alcohol into the acid that gives the vinegary flavor. Sometimes these processes are not fully synced-up and kombucha may end up tasting a bit too funky, or may not meet the requirements of a non-alcoholic beverage.

At this Science on Tap, Dr. Chris Curtin will describe his laboratory’s quest to work out which yeast and bacteria are most commonly found in SCOBY and how they cooperate to deliver tasty, non-alcoholic kombucha. He will also discuss the sometimes controversial topic of whether kombucha is a probiotic beverage.

Dr. Chris Curtin is an associate professor of fermentation microbiology at Oregon State University, chairs the Microbiology committee of the American Society for Brewing Chemists, and serves as associate editor for the Journal of the Science of Food and Agriculture. His lab focuses on the role of microbes in beverage fermentation and food stability…and enjoying the consumption of those products!