Aroma formation mechanism by the drying step during Congou black tea processing: Analyses by HP-SPME and SAFE with GC-MS

Abstract

Drying plays a key role in the formation of the final aroma of black tea. However, the contribution to its aroma remains unclear. Herein, headspace solid-phase microextraction (HP-SPME) and solvent-assisted flavor evaporation (SAFE) coupled with GC-MS were used to detect the volatiles of tea samples (before or after drying) from three cultivars. We found that the drying step caused increase in sweet and fruity aromas and decrease in mint-like and green aromas. 89 Differential volatiles were identified with variable importance in projection (VIP) over 1. Furthermore, 25 decreased aroma-active volatiles were obtained with relative odor activity values (rOAVs) over 1, showing that green, flowery fruity, sweet, and mint-like decreased significantly by 62.27%, 64.88%, 67.56%, 58.26%, and 69.72% after drying step. (Z)-3-hexen-1-ol (rOAV = 36.93), linalool (rOAV = 301.56) and methyl salicylate (rOAV = 5.50) were the odorants for the green, flowery, fruity, and mint-like odor. Moreover, other 3 increased aroma-active volatiles showed that flowery, fruity, and sweet volatiles increased significantly after drying step. β-Damascenone (rOAV = 43.49) was the main odorant for fruity and sweet aroma. The 28 differential volatiles were associated with carotenoid degradation, lipid degradation, and glycoside hydrolysis. This study reveals the contribution of drying to the aroma formation of black tea.