Amount of Eurotium sp. in Chinese Liupao tea and its relationship with tea quality

Eurotium sp. are the sexual states of the genus Aspergillus, and their ascospore is a spherical closed capsule with a golden colour. The growth of Eurotium sp. during tea production is a key step in achieving the unique quality of dark tea. This study aimed to evaluate the relationship between Eurotium sp. amount and Liupao tea quality.The amounts of Eurotium sp. in 26 differently aged Liupao tea samples from several factories were studied. Indicators related to the quality of Liupao tea were investigated. The amounts of Eurotium sp. were divided into 0, 105 and 106 levels, and quantitative real-time polymerase chain reaction (qPCR) was performed. Using ultrahigh-performance liquid chromatography and high-performance liquid chromatography, the amounts of emodin and physcion were determined to be closely related to the amount of Eurotium sp. Emodin was not found or occurred in minimal amounts in all raw Liupao tea samples. By contrast, physcion was found in Liupao tea at the 106 level of Eurotium sp. Liupao tea samples with varying levels of Eurotium sp. also exhibited evident differences in aroma and chromaticity. Result of the Pearson correlation test showed that the amount of Eurotium sp. plays a key role in creating the unique quality of Liupao tea.The amount of Eurotium sp. in dark tea detected via qPCR can be used as a quantitative quality indicator for evaluating dark tea.The present study provides an efficient method for identifying the different qualities of dark tea and addressing quality control issues in fermenting dark tea.