Titration and HPLC Characterization of Kombucha Fermentation: A Laboratory Experiment in Food Analysis

Quantification of the many constituents that make up our food, whether they are desirable (vitamins, antioxidants, nutrients) or undesirable (pesticides, toxins), is one of the most practical applications of chemistry. In this study, kombucha, a popular fermented tea beverage, was analyzed using acid–base titration and high-performance liquid chromatography (HPLC). Kombucha is made via the fermentation of sweetened black tea with a symbiotic culture of bacteria and yeast (SCOBY), which produces acetic acid in addition to a variety of other organic acids and vitamins. The aim of this study was to analyze the acid content of kombucha over a 21-day fermentation period in order to characterize the fermentation kinetics. Titrimetric analysis revealed that the total acidity increased linearly with fermentation time at a rate of 1.5 mM/day. The acetic acid content was also quantified by HPLC at 7-day intervals by standard addition and compared to the total acidity determined by titration. A paired Student's t test was used to validate the methods. In an extension of the lab, HPLC was also used to identify and quantify the caffeine content of kombucha. The experiments utilized in this study provide a means to characterize beverages and fermentation as well as teach important quantitative and statistical skills. This study was implemented as a three-week teaching lab in a quantitative analysis course for undergraduate chemistry majors.