Aroma formation and transformation during production of Fenghuang Dancong oolong tea

Fenghuang Dancong tea is a type of semi-fermented oolong tea with unique floral and fruity flavours. However, little is known about aroma formation in Fenghuang Dancong tea during production. In the present work, headspace solid phase microextraction (HS-SPME) combined with gas chromatography mass spectroscopy (GC-MS) was used to extract, detect, and analyse aroma compounds in Fenghuang Dancong tea during the six stages of its production, namely fresh leaves, withering, rocking, de-enzyming, rolling, and baking. In addition, aroma compound changes were statistically validated, and sensory implications were discussed. In total, 131 aroma compounds were extracted and identified throughout production of Fenghuang Dancong tea. The content of alcohols and esters in fresh leaves, withering, and rocking stages was higher than that in de-enzyming, rolling, and baking stages. The content of aroma compounds such as phenylethanol, nerolidol, β-Ionone, and phenylacetaldehyde increased significantly throughout production of Fenghuang Dancong tea. These aroma compounds were the major contributors to the floral and fruity aroma of Fenghuang Dancong tea, and can be thus used as markers of aroma quality of Fenghuang tea during production. In addition, hierarchical cluster analysis (HCA) and principal component analysis (PCA) indicated that aroma compounds extracted during production of Fenghuang Dancong tea clustered into four distinct categories. The findings highlighted the potential of using aroma compounds as markers for aroma quality control during production of Fenghuang Dancong tea, with rocking and de-enzyming stages being identified as the key steps for aroma formation in Fenghuang Dancong tea.