Introduction: Kombucha is a fermented tea, where yeast fermentation of sugar to alcohol continues to bacterial fermentation of alcohol to acetic acid. Alcohol content and acetic acid create label inaccuracies, as the conversion rate of sucrose to ethanol has never been studied.
Objective: The objective of this study was to exhibit the need for development of new methods of carbohydrate analysis, and demonstration of the inaccuracy of Kombucha testing in the Food Industry compared to the producer’s label.
Materials and Methods: Common methods of carbohydrate testing were evaluated and compared using standard deviation, coefficient of variation, and variance. Phenol-Sulfuric Acid Method was evaluated and relied on the creation of a standard curve. A glucose stock solution was created, and six data points analyzed along with one Kombucha sample. GT’s Original Kombucha was diluted by 1:2000, then .05 mL of 80% phenol solution added to each tube and vortexed. Sulfuric acid was added to the tubes at 5 mL, and vortexed. This reaction occurred for ten minutes, then placed in a 25 C waterbath for 10 minutes. Samples were read in spectrophotometer at 490 nm, and standard curve analyzed in Excel. Measurement of percent brix was conducted by refractometer, and read on the instruments scale, and multiplied by serving size to determine sugar content. Density measurement was conducted using a graduated cylinder and scale, filled with 100 mL of Kombucha. The density was calculated and compared to values from a Specific Gravity to % Brix table.
Results: The Phenol Sulfuric Acid method relies on the reaction of sulfuric acid with sample, and results in inaccuracies of plotting along the standard curve, as indicated by the R2 value in Graph 1. The density method and percent soluble solids method provides the same estimate of sugar content, the alcohol and acetic acid content are not high enough to effect results.
Conclusions: Density and percent soluble solid methods are not significantly impacted by the effects of alcohol and acetic acid. Further study should be conducted for the conversion of glucose to ethanol, and gas chromatography used to estimate the alcohol content after fermentation
