Formation mechanism analysis of bitterness and astringency during Enshi Yulu green tea processing by metabolomics and...

This research aimed to explore the bitterness and astringency formation mechanism of Enshi Yulu green tea (ESYL) by analyzing its sensory quality and taste component changes in each traditional manufacturing process. Sensory evaluation revealed rolling and shaping as key processes for bitterness and astringency intensification. Metabolomics analysis identified 166 non-volatile components from the samples, with VIP > 1 and p < 0.01 for 22 differential metabolites (including 6 catechins, 11 flavonoids, 1 alkaloid, etc.). Six key taste contributors (Epigallocatechin gallate, (-)-Epicatechin gallate (ECG), caffeine, quercetin 3-O-rutinoside (Que-rut), quercetin 3-O-galactoside (Que-gal), and glutamic acid) were further screened by dose-over-threshold value analysis, taste recombination and omission experiments. Content changes in ECG, Que-rut, and Que-gal were identified as key factors for bitterness and astringency aggravation in the two processes. By process optimization, a new technology of time-controlled rolling (100 min) and pressure-optimized shaping (20 min) was established, effectively reducing ESYL bitterness and astringency.