This study aims to explore the key factors influencing the processing of braised Rehmanniae Radix, optimize the processing, and determine the correlation between the components in different processed products and chroma values, which is expected to add quantitative indexes for the processing of braised Rehmanniae Radix and better control the processing. The weights of the indexes catalpol, rehmannioside D, verbascoside, isoacteoside, 5-hydroxymethylfurfural, reducing sugar, and appearance were calculated based on analytic hierarchy process(AHP) in combination with coefficient of variation, and the overall desirability(OD) was obtained. Box-Behnken design was used to explore the optimal amount of water added, time for soaking with rice wine, and steaming time in the processing of braised Rehmanniae Radix. Colorimeter was employed to determine the chroma of 17 samples and raw samples, and SPSS, Prism, and other software to investigate the correlation between the components in braised Rehmanniae Radix and the chroma values. The results showed that each factor influenced the processing, and the influence followed the order of steaming time>amount of water added>time for soaking with rice wine. The optimal processing process is as below: A total of 100 g medicinal material was added with 7 times of water, followed by soaking with rice wine for 5 h and steaming in a pot for 6 h. The correlation analysis suggested the extremely significantly positive correlation between L~* and content of catalpol, between a~* and 5-hydroxymethylfurfural content, and between b~* and catalpol content, and the extremely significantly negative correlation between L~* and the content of 5-hydroxymethylfurfural and reducing sugar, and between b~* and the content of 5-hydroxymethylfural and reducing sugar. In this experiment, response surface methodology was used to optimize the processing technology of braised Rehmanniae Radix and the optimized process was rational and feasible. The content of chemical components in braised Rehmanniae Radix was significantly correlated with the chroma. This study provided a new method for the quality evaluation of braised Rehmanniae Radix.
Keywords: analytic hierarchy process; braised Rehmanniae Radix; chroma; coefficient of variation; correlation; process optimization; response surface methodology.