Determining the Relationship between Aroma and Quality of Bao-Chung Tea by Solid-Phase Microextraction (SPME) and Electronic Nose Analyses

Despite extensive studies, the relationship between the quality/quantity of tea odorants and oolong tea quality remains unclear. To investigate the key components affecting Bao-chung tea quality, we collected samples of different grades from a tea-tasting competition and determined the content and composition of volatile components and individual catechins using gas chromatography-mass spectrometry and high-performance liquid chromatography. We used an electronic nose (E-nose) to collect odor component signals and established a quality recognition model. The different tea grades did not significantly differ in catechin content, but their specific odor intensity and proportion of odor components varied significantly. Linear discriminant analysis showed that the intensity and proportion of volatile organic compounds could be used for distinguishing the different grades of Bao-chung tea. By combining different quantities of indole, linalool, and butanoic acid and proportions of p-cymene, cis- fi-ocimene, nonanal, allo-ocimene, cis-jasmone, and ff-farnesene, the ability to distinguish among Bao-chung tea grades was significantly improved. Our results revealed that the quality of Bao-chung tea should be evaluated based on the combined perception of odor component intensity and proportion rather than solely relying on the concentration or composition of specific compounds. Therefore, individuals can judge a Bao-chung tea grade based on the combined perception of odor component intensity and proportion. The E-nose can be used to identify Bao-chung tea grades based on its ability to determine the odorant composition.