Live, Probiotic, or Neither? Microbial Composition of Retail-Available Kombucha and “Hard” Kombucha in the Pacific Northwest of the United States

Abstract

Kombucha is an acidic non-alcoholic fermented tea beverage that has surged in popularity over the past decade. A key driver of this popularity is the perception that kombucha contains microbes that contribute to gut health, a perception that is reinforced by package claims such as “live” and “probiotic”. We surveyed retail-available non-alcoholic (soft) and alcoholic (hard) kombucha and selected 39 products, of which 74.4% included at least one of these claims. Based upon Nuclear Magnetic Resonance (NMR) evaluation of the chemical composition, approximately one-third of soft kombucha products were re-categorized as “soft-aberrant” on the basis of their alcohol by volume (ABV) exceeding 0.5%. Across all three categories, the majority (82.1%) of products were “live”, containing culturable yeast and/or bacteria. However, there were no significant differences in median maximum colony-forming unit (CFU) counts between these categories, nor was there a difference according to package claims. Interestingly, only 6.3% of soft and 10% of soft-aberrant kombucha products exceeded 106 CFU/mL, the threshold that would deliver at least one billion cells in one package. None of the sampled hard kombucha exceeded this threshold. Metabarcoding analyses of microbial communities revealed differences in composition between categories and according to package claims. Notably, the subset of products with “probiotic” claims that listed Bacillus coagulans as an ingredient were enriched in read counts for Bacillus.

Keywords

• kombucha
• fermentation
• fermented beverages
• brewing
• NMR
• chemical composition