Flavor of Wuyi Rock Teas Analyzed by Targeted Metabolomics

Objective Targeted metabolomics was applied to study the differentiated flavor characteristics of variety Wuyi rock teas to aid breeding selection.

Method Sensory evaluation and a targeted metabolomic analysis on the flavor of five Wuyi rock teas made from fresh leaves of the variety tea germplasms including Aijiao Oolong (AJWL), Hongdujuan (HDJ), Honghaitang (HHT), Zuiguifei (ZGF), and Guoshanlong (GSL) were conducted. Correlations between the panel score and identified chemical compounds were statistically determined.

Result The flavor of the five Wuyi rock teas as ranked by the sensory scores were HDJ (93)>HHT (90.5)>AJWL (90)>GSL (88)>ZGF (85). The teas differed significantly on the targeted metabolomics of catechins, alkaloids, amino acids, soluble sugars, and flavonoids (P<0.05). At the Dot value (i.e., taste activity value or dose-over-threshold) greater than 1, 19 of these substances, such as EGCG, caffeine, and kaempferol-3-O-galactoside, were shown to be the pivotal contributors. According to the results obtained from the principal component analysis (PCA) and partial least squares-discriminant analysis (PLS-DA) on the targeted metabolomes of these identified compounds, the five Wuyi rock teas could be distinctively distinguished. And using Dot>1, VIP>1, and P<0.05 as the analysis criteria, EGCG, EGC, ECG, GC, EC, and caffeine were determined to be the crucial chemicals that differentiated the flavor of the teas.

Objective The significantly different flavor of the five Wuyi rock teas were attributed to six chemical compounds. The germplasms, AJWL, HDJ, and HHT appeared most promising for breeding varieties of high-quality rock teas.