Role of roasting in the formation of characteristic aroma of wuyi rock tea

Roasting is one of the most critical manufacturing steps for making Wuyi Rock tea (WRT). The role of roasting in the formation of characteristic aroma of WRT was elucidated in detail in this study. First, the volatiles formed during the roasting process of WRT were investigated by using HS-SPME-GC-MS. Next, 18 volatiles were identified as odor active compounds (flavor dilution factor ≥1) and 5 volatiles were identified as key aromatic compounds (odor activity value ≥ 1) by using HS-SPME-GC-O-MS and aroma recombination tests. Furthermore, model reactions of fructose, amino acids, and epicatechin, mimicking the Maillard reaction occurred during roasting, indicated that roasting temperature, amino acid type, and catechins were critical factors for the formation of the characteristic aroma of WRT. In specific, the temperature above 120 °C facilitated the formation of 2,3-diethyl-5-methylpyrazine, 5-methyl-2-furancarboxaldehyde and 2,6-diethyl pyrazine. And high temperature roasting also facilitated the elimination of off-flavors with grassy odor formed during tea storage. The model reactions of fructose with alanine and lysine at 130 °C formed the highest abundance of characteristic aroma of WRT. Additionally, it was also found that epicatechin inhibited the formation of the characteristic aromatic compounds of WRT. Taken together, this study provides details regarding the dynamics of volatiles during roasting, and elucidates the roles of roasting on the formation of the characteristic aroma of WRT.