Effect of Roasting Process on Volatile Aroma Components of Baiyaqilan Tea

In this study, headspace solid-phase microextraction coupled with gas chromatography-mass spectrometry (SPME-GC-MS) and odor activity value (OAV) analysis were used to investigate the changes in aroma components of Baiyaqilan oolong tea before and after roasting. The results showed large differences in the types and contents of aroma components in Baiyaqilan tea before and after roasting. The major aroma components before roasting included geraniol, dehydrolinalool, cis-bergamotene, phenylethanol, phenylacetaldehyde, cis-jasmone and geranyl acetone. The major aroma components after roasting included geraniol, dehydrolinalool, oxopholone, cis-jasmone, geranylacetone, cis-coumarin, phenylethanol, phenylacetaldehyde, safranal, trans-2-decenal, oxoisophorone, cis-bergamotene, cosmene, cis-linalool oxide, and 2-pentylfuran. The changes in aroma of Baiyaqilan tea after roasting were attributed to mechanisms such as volatilisation of low-boiling substances, conversion of α-lonone, thermal decomposition of glycosides, oxidation of alcohols, peroxidative decomposition of lipids, and conversion of terpenes and alcohols, resulting in the production of oxopholone, cis-linalool oxides, and 2-pentylfuran as well as a substantial increase in the contents of safranal, trans-2-decenal and cosmene. In summary, this study revealed that the roasting process produced aroma components, altering the aroma profile of oolong tea, and for the first time it was found that the roasting process could lead to the production of the key aroma components including oxopholone. These results provide a reference for in-depth understanding of the effect of the roasting process on the aroma components of oolong tea.