Analysis of Volatile Substances of Different Grades of Pu'erh Ripe Tea

In order to explore the influence of different grading treatments of machine collected and sun-dried green tea on the aroma quality of subsequent Pu'erh ripe tea, the raw materials were classified as No.1, No.2 and No.3, and the refined materials were classified as No.4, No.5 and No.6. Finally, different grades of Pu'erh ripe tea were used as experimental materials, which were detected by tea sensory evaluation, electronic nose technology and gas chromatography-mass spectrometry. The results showed that 50 volatile substances were identified in different grades of Pu'erh ripe tea, mainly Methoxybenzene, followed by alcohols and alkenes. The results were basically consistent with that of C6 (be sensitive to methyl) sensor in the second main component, followed by C8 (be sensitive to alcohols, aldehydes and ketones) sensor. The results of LDA analysis of electronic nose were similar to those of GC-MS data tree analysis. The results also showed that methoxybenzene was the main substance determining the aging aroma in Pu'erh ripe tea. The relative content of trans linalool oxide (furan) was positively correlated with the grade of Pu'erh ripe tea, and the relative content of naphthalene was negatively correlated with the grade of Pu'erh ripe tea. In short, there were several differences in the volatile substances of Pu'erh ripe tea after different classification treatment. The research results could provide a scientific method for the quality improvement of machine picked and sun-dried green tea in the subsequent processing of Pu'erh ripe tea.