Characteristics of Sichuan south-road dark tea fermented by Debaryomyces hansenii Y4 and the microbial role in quality formation

Microbes are crucial for Sichuan south-road dark tea (SSDT) quality formation. Here, SSDT (Y4 20d sample) produced by Debaryomyces hansenii Y4 was comprehensively analyzed by sensory evaluation combined with UHPLC-MS/MS and GC-MS investigation. Finally, a sensory characteristic of traditional SSDT with increased aged, herbal, sweet, and mellow flavors was observed in Y4 20d . D. hansenii Y4 produced dramatic changes in the volatile and non-volatile components of Y4 20d , with 20 volatiles and 16 non-volatiles identified as differential components between Y4 20d and the control (CK 20d ). A lower collective increase in bitter chemicals than that of sweet chemicals was detected in Y4 20d compared to CK 20d . During fermentation, changes in the relative levels of linalool, geraniol, alpha-terpineol, 2-ethylhexanol, 1-octen-3-ol, furfural, benzaldehyde, nonanal and tea pyrrole in tea samples mediated by D. hansenii Y4 may contribute significantly to enriching the aroma and attenuating the green odor in SSDT at the early fermentation stage, forming the distinct aroma of SSDT at the late stage, and intensifying it at the final stage. 1-Octen-3-ol, furfural, tea pyrrole, nonanal, and D-tagatose were the critical flavoring chemicals of SSDT produced in this work. Results will facilitate understanding the mechanism underlying microbial mediation of SSDT quality transformation during fermentation. • D. hansenii Y4 is valuable for Sichuan south-road dark tea (SSDT) production. • D. hansenii Y4 is involved in the formation of SSDT's mellow, herbal, sweet flavor. • 1-Octen-3-ol, tea pyrrole and nonanal are the key volatiles of SSDT produced here. • D. hansenii Y4 may participate in D-tagatose metabolism via beta-galactosidase.