Variation of taste and odor compounds in tea beverage after microbial fermentation by HPLC-MS, GCxGC-O-MS, GC-MS, and sensory evaluation

Tea beverages are widely welcomed by consumers, and their flavor quality is particularly important. In this study, different tea extracts were fermented by Trichoderma reesei (TR), Aspergillus niger (AN), and lactic acid bacteria (LAB) to obtain the tea beverages, which were characterized by sensory evaluation as well as instrumental analysis. Nonvolatile compounds in tea beverages were determined by high-performance liquid chromatography-mass spectrometry (HPLC-MS), and volatile compounds were determined by solid-phase microextraction (SPME) combined with comprehensive two-dimensional gas chromatography-olfactory-mass spectrometry (GCxGC-O-MS) and gas chromatography-mass spectrometry (GC-MS). The data were analyzed by both principal component analysis (PCA) and orthogonal partial least squares discriminant analysis (OPLS-DA). The bitter and astringent galloylated catechins in tea beverages were hydrolyzed after TR and AN fermentation. Then after fermentation with LAB, some organic acid and phenolic compounds were decarboxylated, and some saccharides were also metabolized. Meanwhile, the increased content of alcohols and ketones in tea beverages affected the overall aroma. These results demonstrate the positive effects of microbial fermentation on the processing of tea beverages and provide technique support for comprehensive flavor quality control.