Evaluating chromatographic techniques for the aroma profiling of kombucha

Kombucha is a fermented beverage made from the addition of a symbiotic community of bacteria and yeast (SCOBY) to a sugary base tea. Despite the odors associated with kombucha, few studies have examined its chemical aroma profile. The mixture of volatile organic compounds (VOCs) from tea and its fermentation is typically examined using one-dimensional gas chromatography with time-of-flight mass spectrometry (GC-TOFMS). More complex samples benefit from the higher resolution and separation capacity of comprehensive two-dimensional gas chromatography with time-of-flight mass spectrometry (GC×GC-TOFMS), which separates analytes based on their affinity for two distinct stationary phases. This study aimed to compare the efficacy of GC-TOFMS to GC×GC-TOFMS, to use VOC data to differentiate between kombucha products, and to establish an understanding of the VOCs originating from tea versus microorganisms. Samples were taken from 12 sources including two SCOBYs, one starter tea, and eight kombucha teas and analyzed using GC-TOFMS and GC×GC-TOFMS. GC-TOFMS detected 127 analytes across 15 compound classes while GC×GC-TOFMS detected 182 analytes across 17 compound classes. The enhanced separation power of GC×GC-TOFMS allowed for the resolution of coelutions that occurred in GC-TOFMS data. Statistical techniques including principal component analysis (PCA), principal coordinate analysis (PCoA), hierarchical cluster analysis (HCA), Fisher ratio, and fold change were applied to the VOC data. Locally produced products contained simple esters and acids while commercial brands contained terpenes and aromatic compounds. This work builds on the overall aim of linking VOC data from microbes and tea with the flavor profile of fermented foods as examined by advanced analytical techniques.