The dynamic changes and mechanisms of Rehmanniae radix processing based on Maillard reaction

Background: Traditional Chinese medicines are usually processed before they are used for clinical treatment. This is done in a way associated with the Maillard reaction. Methods: Based on the Maillard reaction, this paper analyzed the degree of processing of rehmannia root (Rehmanniae radix) relative to the dynamic variation rules of Maillard reaction index parameters, including pH, A420, amino acids, and 5-hydroxymethylfurfural. Furthermore, this study introduced thermal analysis techniques and pyrolysis kinetics to assess the influence of the correlation between processing raw rehmannia root and the Maillard reaction during carbonization. It then went through the whole process of transforming the raw material to end-product in order to explain the scientific connotation of processing it. Results: The results showed that each time rehmannia root was processed, its pH value and amino acid content decreased, while the A420 value and 5-HMF increased. Processing with wine shows a significant difference in these experimental indexes. The position and intensity of the maximum thermal weight loss rate peak of processed rehmannia root at different degrees of processing are different. Comprehensive quantitative 221 ± 0.2 °C for processed rehmannia root carbonization was the processing temperature limit. Moreover, the kinetic solution verified that the activation energy corresponding to the carbonization temperature was close to the maximum value of the activation energy of the whole carbonization process, and the optimal mechanism function was g(α) = ((1 − α) − 1/3 − 1)2. Conclusion: The Maillard reaction occurred during the processing of rehmannia root mixed with carbonization. With each increase of the number of steaming and drying cycles involved in the processing, the level of Maillard reaction increased significantly. The wine-steaming method had a significant effect on the quality of the processed product.