Aroma-active compounds related to Maillard reaction during roasting in Wuyi Rock tea

Maillard reaction could be a breakthrough in standardizing the roasting process, which is a pivotal procedure in refining Wuyi Rock tea (WRT). This study aimed to find indicators to instruct the roasting process scientifically trying to provide theoretical support for actual production. A total of 86 volatile compounds were detected by solid-phase microextraction (SPME) coupled with gas chromatography–olfactometry–mass spectrometry (GC–O–MS) and GC×GC–O–MS in three rough WRTs leaves (RL) Dahonpao, Shuixian, and Rougui and three roasting degrees, light fire (LF), moderate fire (MF), and high fire (HF). Among them, 45 key aroma-active compounds with r-OAV> 1. Significant differences existed between RL/LF and MF/HF. The Maillard reaction primarily strengthened the roasted attributes but eliminated the individual characteristics through 1-ethyl-1H-pyrrole, 2-ethyl-5-methylpyrazine, 2-ethyl-6-methylpyrazine, 2-ethyl-3-methylpyrazine, furfural, and 5-methyl-2-furancarboxaldehyde. If combined with the analysis of amino acids, sugars, and polyphenols, eight aroma-active compounds relating to the Maillard reaction, furfural, 5-methyl-2-furancarboxaldehyde, 1-ethyl-1H-pyrrole-2-carboxaldehyde, 2-ethyl-5-methylpyrazine, 2-ethyl-6-methylpyrazine, 2,5-dimethyl-3-ethylpyrazine, 1-ethyl-1H-pyrrole, and methylpyrazine, could be considered as indicators to monitor the roasting process. The novelty of this result was that it provides the practical knowledge for further deep investigation from the perspective of the Maillard reaction and makes it possible to industrialize WRT manufacturing, rather than only relying on empiricism.