Abstract
Fu brick tea is a unique post-fermented tea product which is fermented with microorganism during the manufacturing process. Metabolic analysis showed that most metabolites content were decreased during the manufacturing process of Fu brick tea, except GA (gallic acid). Illumina MiSeq sequencing of ITS gene amplicons was applied to analyze the fungal community succession. The genera Aspergillus, Cyberlindnera and Candida were predominant at the early stage of manufacturing process (from “primary dark tea” to “fermentation for 3 days”), but after the stage of “fermentation for 3 days” only Aspergillus was still dominated, and maintain a relatively constant until to the end of manufacturing process. The effects of metabolites on the structure of the fungal community were analyzed by redundancy analysis (RDA) and variation partitioning analysis (VPA). The results indicated that GCG (gallocatechin gallate), EGCG (epigallocatechin gallate) and GA as well as the interactions among them were the most probably ones to influence, or be influenced by the fungal communities during the fermentation process of Fu brick tea. This study revealed fungal succession, metabolite changes and their relationships, provided new insights into the mechanisms for manufacturing process of Fu brick tea.
Highlights
Chinese teas are divided into six categories according to the processing technology and oxidation degree: green tea, white tea, yellow tea, oolong tea, black tea, dark tea[1]
The level of FLA and organic acid (OA) ranged from 0.86 ± 0.01% to 1.05 ± 0.03% and 1.34 ± 0.20% to 1.65 ± 0.02%, but no significant difference were observed during the manufacturing process of Fu brick tea (Fig. 1A)
Our metabolic analysis showed that water extract (WE), soluble sugar (SS), tea polyphenol (TP) and catehins were significantly decreased, but gallic acid (GA) was significantly increased during the manufacturing process of Fu brick tea
Summary
Chinese teas are divided into six categories according to the processing technology and oxidation degree: green tea (no oxidization), white tea (slightly oxidized), yellow tea (lightly oxidized), oolong tea (partially oxidized), black tea (fully oxidized), dark tea (post-fermented)[1]. A recent studies using PCR-DGGE analysis revealed that the microorganisms found in Fu brick tea were from or closely related to the genera Aspergillus, Beauveria, Debaryomyces, Eurotium, Pestalotiopsis, Pichia, Rhizomucor, and Verticillium[10], while other studies found that Aspergillus niger, Blastobotrys adeninivorans and Bacillus, Enterobacteriaceae were the major fungal and bacterial communities involved in Pu-erh tea, another kind of post-fermentation tea[11, 12]. These techniques provide limited information on community information, because only a few sequences can be separated and analyzed. This knowledge could give new insight into the manufacturing process and provide valuable knowledge to improve the quality of Fu brick tea
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