Comparative analysis of different grades of Tieguanyin oolong tea based on metabolomics and sensory evaluation

To develop objective methods of oolong tea grading for importers and customs, metabolomics and sensory evaluation were applied to screen the characteristic compounds associated with Tieguanyin (TGY) tea grades T, 1, 2, and 3, and types (fresh scent flavor and high fragrance). With decreasing TGY grade/quality, the astringency and content of most flavonoid glycosides increased (especially catechin and epicatechin). The floral aroma of fresh scent flavor TGY decreased, and the roasted aroma of high-fragrance TGY increased with decreasing TGY grade. Five non-volatile compounds (epicatechin gallate, quercetin-3-O-galactoside, quercetin-3-O-rutinoside, epicatechin, and gallocatechin) and five volatile compounds (benzyl benzoate, beta-phenylethyl acetate, 6-methyl5-hepten-2-one, heptanal, and (E)-2-hexenal) were identified, which could readily distinguish different grades of fresh scent flavor and high fragrance TGY by quantitative chemical analysis. Lower grades of TGY had inferior flavor, but higher antioxidant capacity.

Automated summary

In order to develop objective methods for grading oolong tea, metabolomics and sensory evaluation were used to identify characteristic compounds associated with different grades and types of Tieguanyin tea. The study found that as the grade/quality of Tieguanyin decreased, the astringency and content of most flavonoid glycosides increased, while the floral aroma of fresh scent flavor decreased and the roasted aroma of high fragrance increased. Through quantitative chemical analysis, five non-volatile compounds and five volatile compounds were identified, which could effectively distinguish different grades and types of Tieguanyin tea. Lower grades of Tieguanyin had inferior flavor but higher antioxidant capacity.