The purpose of this study was to determine the percent of alcohol by volume (ABV) in several commercial kombucha tea beverages and determine whether or not bottle fermentation can lead to significant increases in ABV values. Kombucha is a popular tea to drink. It is reported to contain trace amounts of alcohol because it is produced by fermenting sweet tea with yeast and bacteria cultures. Kombucha tea is often marketed as a health drink rather than an alcoholic beverage because of its low volume percent of alcohol. If kombucha is at or above 0.5% ABV at any time, it is considered an alcoholic beverage and must follow regulations from the Alcohol and Tobacco Tax and Trade Bureau (TTB). In this study, gas chromatography was used to quantify the ABV of several commercially available kombucha teas. Standard solutions were prepared to generate a standard curve correlating ethanol ABVs to chromatographic peak areas. 1-propanol was used as an internal standard in all samples. Of the kombucha samples represented, there were a sample set of unpasteurized bottles where two were fruit-infused and one that was not. These samples were then allowed to bottle ferment at room temperature and analyzed in a weekly study. The fruit-infused samples had initial average ethanol ABVs that were ~1.4-1.8% and at the end of three weeks increased to ~2.6-3.5%. In contrast, the non-infused tea samples ranged from ~0.57-0.90% and after three weeks increased to ~1.0-1.8%. This is not surprising as the fruit-infused kombucha teas most likely had more residual fermentable sugar available for bottle fermentation. This raises a concern over both the distribution and labeling of kombucha teas that are sold as non-alcoholic beverages. These results also agree with another recently published gas chromatographic study on kombucha tea ABVs.

Quantitation of ethanol in kombucha beverages with evidence of bottle fermentation by gas chromatography

Macromolecular Chemistry: The Second Century

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ACS Spring 2020 National Meeting & Expo

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.