Differential Analysis of Flavor Compounds in Junlian Black Tea from Different Geographical Origins

The sensory and physicochemical properties of Junlian black tea samples produced in the three villages of Yinxing, Yinjiang, and Maogu in Junlian county, Sichuan province were evaluated, and their non-volatile and volatile components were identified by ultra-high performance liquid chromatography-quadrupole time-of-flight-mass spectrometry (UPLC-QTOF-MS) and solid phase microextraction-gas chromatography-mass spectrometry (SPME-GC-MS), respectively. Multivariate analyses including heatmap, principal component analysis (PCA), and partial least squares-discriminant analysis (PLS-DA) were combined to distinguish the key compounds of Junlian black tea from different geographical origins. The results showed that the Yinxing sample had the highest sensory evaluation score, lowest water content and tea polyphenol levels and highest water extract levels, which were primarily characterized by a red and bright infusion color, sweet, floral and fruity aromas, a fresh, sweat and mellow taste, and tender leaf bottom with multiple buds. A total of 50 differential metabolites were selected by UPLC-QTOF-MS, which could serve as potential marker compounds for distinguishing Junlian black tea from the three different regions, and most glycosides, some amino acids and organic acids were significantly accumulated in the Yinxing sample, whereas most flavonoids and catechins were predominantly richer in the Maogu sample. The results of SPME-GC-MS showed that linalool, geraniol and β-ionone were abundant in Junlian black tea, and all of them contributed to floral, fruity, and sweet aromas, which could be regarded as the characteristic aroma components. A total of 17 differential compounds were selected, which could be used as potential volatile markers for distinguishing Junlian black tea from different geographical origins. Most of the differential volatile metabolites were the most abundant in the Yinxing sample, showing a significant floral and fruity aroma. This study provides a theoretical basis for the quality control of Junlian black tea, and lays a foundation for understanding the formation mechanism of key chemical components and aroma components in Junlian black tea.