Aroma effects of critical volatile compounds during thermophilic bacteria pile-fermentation in dark tea using gas chromatography mass spectrometry and odor activity value

Abstract

Thermophilic bacteria play an important role in aroma formation during pile-fermentation process of dark tea. With the aim to reveal the impact of thermophilic bacteria on volatile compounds in dark tea, Bacillus licheniformis (thermophilic bacteria) were inoculated into sun-dried green tea for spontaneous fermentation. In this study, headspace solid phase microextraction combined to gas chromatography mass spectrometry (HS-SPME-GC-MS), odor activity value (OAV), principal component analysis (PCA) and orthogonal partial least squares discrimination analysis (OPLS-DA) were employed to investigated the characteristics of volatile compounds during thermophilic bacteria pile-fermentation. According to HS-SPME-GC-MS, a total of 64 volatile compounds were identified. PCA revealed that tea samples could be clearly discriminated from each other. Furthermore, sulcatone, hexanoic acid, linalool, 2-methyl-trans-decalin, myrtenal, and α-ionone were found to play an important role in discrimination of tea samples, based on OPLS-DA. In addition, the OAV could effectively characterize the aroma contribution of volatile compounds during thermophilic bacteria pile-fermentation, and (Z)-linalool oxide (furanoid), α-ionone, (E)-2-nonenal, and linalool were the critical volatile compounds of aroma quality in dark tea. This study provides insight into volatile compounds characteristics during thermophilic bacteria pile-fermentation in dark tea.

A Rising Star in Dark Teas: The Processing, Microorganisms, Chemicals, Bioactivities, and Safety of Qingzhuan Tea

“…Thermophilic strains can produce cellulase and amylase to increase the content of soluble sugar. 58,59 Among them, cellulase can degrade cellulose to produce glucose, and amylase can hydrolyze starch to produce oligosaccharides. Yeast can secrete enzymes that degrade phenol and produce a sweet xylitol substance.…”

“…Qingzhuan tea polysaccharides are acid polysaccharide or acidic glycoprotein binding to protein, mainly composed of arabinose, rhamnose, ribose, fucose, galactose, glucose, xylose, mannose, and galacturonic acid. , During the process of fermentation, the tea polysaccharides showed a trend of first rising and then decreasing due to the change in microbial population. Thermophilic strains can produce cellulase and amylase to increase the content of soluble sugar. , Among them, cellulase can degrade cellulose to produce glucose, and amylase can hydrolyze starch to produce oligosaccharides. Yeast can secrete enzymes that degrade phenol and produce a sweet xylitol substance .…”

Comprehensive applications of metabolomics on tea science and technology: Opportunities, hurdles, and perspectives

“…and Xia et al (2022) reported that bacteria were able to consume some watersoluble saccharides (e.g., fructose and xylose), proteins, amino acids, and purine alkaloids. Besides, HS-SPME-GC-MS analysis revealed that some bacteria could also contribute to the formation of some characteristic aroma compounds during pile fermentation (Table 2) (Zhu et al, 2022).…”

Effects of solid-state fermentation with Bacillus subtilis LK-1 on the volatile profile, catechins composition and antioxidant activity of dark teas

“…Bacillus has been found to promote the metabolism of tea polyphenols and the transformation of caffeine, which is associated with the production of 44 metabolites in FBT ( Li et al, 2019 , Xia et al, 2022 ). Furthermore, earlier research has demonstrated that Bacillus species contribute to the formation of aroma characteristics in tea ( Pripdeevech et al, 2014 , Zhu et al, 2022 ). Therefore, Bacillus species play a crucial role in the formation of metabolites during the manufacturing of FBT.…”