Characterization of primary aroma compounds in Pu-erh raw tea sourced from various regions using gas chromatography-mass spectrometry and headspace solid-phase microextraction.

The assessment of aroma plays a crucial role in determining the characteristics and quality of Pu-erh tea. The volatile compounds present in Pu-erh raw tea sourced from five regions in Yunnan Province have been studied using gas chromatography-mass spectrometry (GC-MS) in conjunction with headspace solid phase microextraction (HS-SPME). A total of 69 aroma-active compounds were identified, with alcohols, ketones, and aldehydes being the predominant component types. Furthermore, notable variations were observed among four pairs of volatile terpenoid enantiomers. Significant discrimination was achieved using orthogonal partial least squares discrimination analysis (R(x) = 0.926, R(y) = 0.843, Q= 0.501). Moreover, 33 important differential compounds were identified based on variable importance in the projection values (VIP > 1.0) and one-way ANOVA analysis (p < 0.05). Subsequently, a KEGG pathway analysis was conducted, revealing enrichment pathways primarily focused on the mevalonate pathway, steroid biosynthesis, and fatty acid biosynthesis. Ultimately, the key volatile compounds and major aroma-contributing compounds were successfully identified.