Effects of fermentation duration on the flavour quality of large leaf black tea based on metabolomics.

Fermentation durations are crucial in determining the quality of black tea flavour. The mechanism underlying the degradation of black tea flavour caused by inappropriate fermentation duration remains unclear. In this study, the taste of black teas with different fermentation durations (BTFs) was analysed using sensory evaluation, electronic tongue, and metabolomics. The results revealed significant differences in 46 flavour profile components within the BTFs. Notably, metabolites such as gallocatechin gallate, gallocatechin, and epigallocatechin were found to be primarily reduced during fermentation, leading to a reduction in the astringency of black tea. Conversely, an increase in d-mandelic acid and guanine among others was observed to enhance the bitter flavour of black tea, while 3-Hydroxy-5-methylphenol nucleotides were found to contribute to sweetness. Furthermore, succinic acid and cyclic-3',5'-adenine nucleotides were associated with diminished freshness. This study offers a theoretical foundation for the regulation of flavour quality in large leaf black tea.

Mellow and Thick Taste of Pu-Erh Ripe Tea Based on Chemical Properties by Sensory-Directed Flavor Analysis.

The mellow and thick taste is a unique characteristic of pu-erh ripe tea infusion, and it is closely related to the chemical composition of pu-erh ripe tea, which is less studied. This paper clarifies and compares the chemical composition of pu-erh ripe tea to that of the raw materials of sun-dried green tea, and uses membrane separation technology to separate pu-erh ripe tea into the rejection liquid and the filtration liquid. The results show that microorganisms transformed most physicochemical components, except caffeine, during the pile fermentation. It was found that total tea polyphenols, soluble proteins, total soluble sugars, theabrownin, and galloylated catechins became enriched in the rejection liquid, and the rejection liquid showed a more obvious mellow and thick characteristic. Taste interactions between crude protein, crude polysaccharide, and theabrownin were determined. They illustrated that the mellow and thick taste of pu-erh ripe tea with the addition of theabrownin increased from 4.45 to 5.13. It is of great significance to explore the chemical basis of the mellow and thick taste in pu-erh tea for guiding the pu-erh tea production process and for improving the quality of pu-erh tea.