Manufacturing Process Analysis and Tea Chemical Component Characterization on Ann Tea Quality Formation

Ann tea is a traditional Chinese dark tea produced in Anhui Province, and it is beloved by consumers for its pleasant flavor and health attribute. Here, the detailed manufacturing process was investigated, and samples from key processing steps were chemical characterized. During the manufacturing process, about 15% of catechins and monosaccharide were significantly reduced and transformed to polymers, such as theanine-glucose, procyanidin dimer, and theasinensins. Theaflavins were mainly produced in steps of fixing, pile-fermentation, and final processing; thearubigins and theabrownins were improved slightly in fixing and rolling but not produced from pile-fermentation, which was different from other dark teas. Metabolomic profiling revealed that pile-fermentation plays an important role in chemical transformation, and principal components showed significant changes pre- and post-pile-fermentation. Compared to pile-fermented dark tea at high temperature (e.g., Puerh tea), catechin reduction during Ann tea processing is relatively low, which might be ascribed to the pile-fermentation process under room temperature.