Analysis of aroma-active volatiles in an SDE extract of white tea.

White tea is a famous Chinese tea that is cooked at boiling point before drinking. The simultaneous distillation-extraction (SDE) was used to collect volatile compounds during tea cooking. The SDE extract was dominated with green, floral, roasted and woody notes, and weak sweet note. There were 32 volatile compounds identified via gas chromatography-mass spectrometry analysis, and 19 of them had strong fragrance based on the gas chromatography-olfactometry analyzed results. Hexanal, 2-hexenal, cis-3-hexen-1-ol, and camphene were the main contributors to the green note. The floral note was mainly contributed by 2-hexanone, benzeneacetaldehyde, trans-linalool oxide, and linalool, and the sweet note was induced by trans-β-damascenone. The roasted note was mainly contributed by 2-pentyl-furan. The woody note was mainly contributed by trans-α-ionone and trans-β-ionone. Four putative reaction pathways, including amino acid degradation, carotene degradation, Maillard reaction, and glycosides hydrolysis, were figured out to explain the generation of aromatic-active volatiles at high temperatures. This study added our knowledge on tea aroma under cooking as well as other thermal treatments.