Identification of volatile compounds and metabolic pathway during ultrasound-assisted kombucha fermentation by HS-SPME-GC/MS combined with metabolomic analysis

The current work combines headspace solid phase microextraction-gas chromatography-mass spectrometry (HS- SPME-GC/MS) with multivariate analysis fusion metabonomics for examining metabolite profile changes. The correlation with metabolic pathways during the fermentation of kombucha tea were comprehensively explored. For optimizing the fermentation process, ultrasound-assisted factors were explored. A total of 132 metabolites released by fermented kombucha were detected by HS-SPME-GC/MS. We employed the principal component analysis (PCA) and partial least squares-discriminant analysis (PLS-DA) to present the relationship between aroma components and fermentation time, of which the first two principal components respectively accounted for 60.3% and 6.5% of the total variance. Multivariate statistical analysis showed that during the fermentation of kombucha tea, there were significant differences in the phenotypes of metabolites in the samples, and 25 characteristic metabolites were selected as biomarkers. Leaf alcohol was first proposed as the characteristic volatile in the fermentation process of kombucha. Furthermore, we addressed the generation pathways of characteristic volatiles, their formation mechanisms, and the transformational correlation among them. Our findings provide a roadmap for future kombucha fermentation processing to enhance kombucha flavor and aroma.

Automated summary

This study combined headspace solid phase microextraction-gas chromatography-mass spectrometry (HS-SPME-GC/MS) with multivariate analysis fusion metabonomics to investigate the metabolite profile changes in fermented kombucha tea. The correlation between the metabolites and the fermentation process was comprehensively explored. Ultrasound-assisted factors were also examined for optimizing the fermentation process. A total of 132 metabolites were detected in the fermented kombucha using HS-SPME-GC/MS. Multivariate statistical analysis revealed significant differences in the phenotype of metabolites during the fermentation, and 25 characteristic metabolites were identified as biomarkers. Leaf alcohol was identified as the characteristic volatile during the fermentation process. The findings of this research provide insights for enhancing the flavor and aroma of kombucha in future fermentation processes.