# Formation Mechanisms and Kinetic Modeling of Key Aroma Compounds During Qidan Tea Roasting
## 3 Results and Discussion
### Establishment of Maillard Reaction Model and Kinetic Equation
The above results suggest that the generation of pyrazines is not only controlled by the temperature threshold, but also requires sufficient thermal interaction time to complete the conversion of precursor substances and molecular rearrangement process. Higher temperatures (\(\geq\)120 \({}^{\circ}\)C) can effectively reduce the activation energy of the reaction and induce the formation of key intermediates from aminocarbonyl compounds via the Strecker degradation pathway, which can then be used to generate pyrazine derivatives with different substituents via free radical coupling reaction [30]. The study of the mechanism of furan production based on the kinetic modeling of the Melad reaction revealed the regulation of 2-methylfuran formation by roasting conditions (Figure 2, Table 4). The experimental data showed that the presence of 2-methylfuran was not detected at the initial stage of the reaction (0-4 h), a latent period characterized by a close correlation with the process of accumulation of the intermediates of the Maillar reaction. When the thermal processing time exceeded 4 h, the compound began to form significantly and showed a time-dependent accumulation trend at all three temperature  
Figure 2: Changes in concentration of major aroma-active compounds ((**A**)\(-\)benzaldehyde, (**B**)\(-\)2-methylpyrazine, (**C**)\(-\)2,6-dimethylpyrazine, (**D**)\(-\)2-methylfuran) at different combinations of temperature and time. The results of the kinetic model fitting showed that the temperature had a significant regulatory effect on the reaction level: under the condition of 100 \({}^{\circ}\)C, the generation of 2-methylfuran conformed to the zero-level kinetic characteristics, which indicated that the reaction rate was mainly controlled by the thermal decomposition energy barriers at this temperature; when the temperature was raised to 120 \({}^{\circ}\)C, the system showed an obvious accelerated generation phenomenon after 8 h. At this time, the kinetic process was more consistent with the first-level reaction model, which implied that the concentration of intermediate or products had become the rate-limiting factor. Further analysis revealed that there was a significant temperature-time synergistic effect in the reaction system: the final concentration of 2-methylfuran increased with every 10 \({}^{\circ}\)C increase in temperature for the same thermal processing time, while the extension of the time to 12 h at a constant temperature resulted in the increase of the high concentration of the product. This nonlinear growth characteristic is directly related to the cascade effect of the successive reactions of reducing sugar degradation and amino acid decarboxylation in the Maillard reaction, indicating that the generation of furans is a combined result of the multi-step transformation of multiple precursor substances. The exponential kinetic equations developed in the study provided a quantitative model for predicting the furanoid production under different roasting parameters.