Analysis of the Changes in Volatile Components During the Processing of Enshi Yulu Tea.

Abstract

Volatile constituents are critical to the flavor of tea, but the changes in Enshi Yulu tea during the processing have not been clearly understood. Using headspace solid phase microextraction combined with gas chromatography-mass spectrometry (HS-SPME/GC-MS) techniques, we analyze the aroma components of Enshi Yulu tea and changes in them during the processing stages. In total, 242 volatile compounds were identified. From fresh leaves to the shaping process in tea production, there are significant decreases in overall aroma substances, followed by increases after drying. Linalool is the dominant aroma component in Enshi Yulu tea, with a proportion of 12.35%, followed by compounds such as geraniol (7.41%), 2,6-dimethyl-5-heptene (6.93%), phenylmethanol (5.98%), isobutyl acetate (4.16%), hexan-1-ol (3.95%), 2-phenylacetaldehyde (3.80%), and oct-1-ene-3-ol (3.34%). The number of differential volatile components varied by production stage, with 20 up- and 139 down-regulated after steaming, 24 down-regulated after rolling, 60 up- and 51 down-regulated after shaping, and 68 up- and 13 down-regulated after drying. Most variation in expression occurred because of steaming, and the least during the rolling stage. PLS-DA analysis revealed significant differences in aroma components throughout processing and the identification of 100 compounds with higher relative contents, with five distinct change trends. Phenylmethanol, phenylacetaldehyde, (2E)-non-2-enal, oct-1-ene-3-ol, and cis-3-hexenyl hexanoate could exert a profound influence on the overall aroma quality of Enshi Yulu tea during processing. The results offer a scientific foundation and valuable insights for understanding the volatile composition of Enshi Yulu tea and its changes during the processing.