Characteristic fingerprints and change of volatile organic compounds of dark teas during solid-state fermentation with Eurotium cristatum by using HS-GC-IMS, HS-SPME-GC-MS, E-nose and sensory evaluation

Eurotium cristatum is the dominant fungus during Fu brick tea (FBT) manufacturing, however, its underlying effects in forming the distinct flavor characteristics of FBT remains unclear. In this work, effect of solid-stage fermentation (SSF) with E. cristatum on the volatile metabolites of dark teas was investigated by various techniques. A total of 54 and 93 volatile organic compounds (VOCs) were identified by HS-GC-IMS and HS-SPME-GC-MS, respectively, which are mainly composed of aldehydes, esters, alcohols and ketones. E. cristatum drastically affected the aroma characteristics of dark teas, and the middle fermentation stage showed the greatest influence. E. cristatum fermentation contributed to increasing the levels of VOCs with stale and flower aromas. Sensory evaluation revealed the intensities of green aroma greatly decreased, and replaced by flower, mint, woody and fungal flower aromas as fermentation progressed. Hydrolytic enzymes were secreted by E. cristatum that catalyze a series of biochemical reactions contributing to the formation of flavor metabolites. Thus, this study indicates that E. cristatum remarkably affected the VOCs of dark teas and improved the stale and flower aromas, which is crucial in forming characteristic volatile metabolites of FBT.