Insight into effects of isolated Eurotium cristatum from Pingwu Fuzhuan brick tea on the fermentation process and quality characteristics of Fuzhuan brick tea

Abstract

Background: Pingwu Fuzhuan brick tea is a type of post-fermented tea manufactured from leaves of the tea plant, Camellia sinensis var. sinensis, the quality of which is influenced by numerous factors, especially microorganisms. Currently, there is little research on the effect of microorganisms on the fermentation and quality characteristics of Pingwu Fuzhuan brick tea. Investigation of the main fungus in this tea and its effect on the fermentation process and tea quality can provide insights into the manufacturing of 'western road' border-selling tea and could lay the foundation for the popularization of Pingwu Fuzhuan brick tea.

Results: The main 'golden flower fungus' in Pingwu Fuzhuan brick tea was isolated and identified as Eurotium cristatum (GenBank accession number: MF800948.1; strain PW-1). Compared with natural fermentation, PW-1 inoculated fermentation accelerated biotransformation of phenolic compounds, which provided tea samples with better taste and tea infusion color. The proportions of velvety and sweet-tasting amino acids increased after 16-day fermentation with PW-1. Alcohols were the most abundant volatiles, with 40.13% and 39.43% content in NF16d and IF16d tea samples, respectively. Orthogonal partial least-squares discriminant analysis (OPLS-DA) and hierarchical clustering analysis (HCA) further revealed that naturally fermented and PW-1 fermented teas were significantly different.

Conclusion: Strain PW-1 plays an important role in the fermentation process of Fuzhuan brick tea. Considering fermentation efficiency and tea quality, fermentation inoculated with E. cristatum PW-1 can be applied in the manufacturing of 'western road' border-selling tea. © 2020 Society of Chemical Industry.

Keywords: Eurotium cristatum; Pingwu Fuzhuan brick tea; biochemical transformation; chemical compositions; fermentation.