ABSTRACT
Objective: The moisture absorption of Rhei Radix et Rhizoma (RRR) with different initial moisture content was studied under the conditions of relative humidity of 20%-85% and temperature of 5, 15, 25 and 35 ℃, respectively, so as to provide reference for the control of safe storage moisture and reasonable storage of RRR. Methods: RRR was stored at temperature of 5, 15, 25 and 35 ℃ and humidity of 45%, 60% and 75%, respectively. The samples were taken at different time points to determine its safe water activity with powder color and mildew as indicators. The isotherm adsorption data of RRR at 5, 15, 25 and 35 ℃ and water activity of 0.2-0.8 were obtained by static weighing method and six isotherm adsorption models, GAB, Oswin, Smith, Halsey, Henderso and Peleg, were used for fitting and evaluation. Results: The absolute safe water activity and relative safe water activity of RRR were 0.5 and 0.6, respectively. The adsorption isotherms of RRR at 5, 15, 25 and 35 ℃ were "S" type, which belonged to type II isotherm. Oswin model was the best fitting model and the model expression was: Meq=A[Aw/(1-Aw)B. According to the model, the absolute safe water content of RRR with different initial moisture content at 5 ℃ was 9.00%, 9.59%, 8.00%, 6.71% and relative safe water content was 10.17%, 10.89%, 9.20% and 8.07%, respectively; The absolute safe water content of RRR with different initial moisture content at 15 ℃ was 8.24%, 8.83%, 7.24%, 5.86% and relative safe water content was 9.57%, 10.17%, 8.59% and 7.20%, respectively; The absolute safe water content of that at 25 ℃ was 7.17%, 7.75%, 5.73%, 4.70% and the relative safe water content was 8.72%, 9.26%, 7.26% and 6.25%, respectively; The absolute safe water content of that at 35 ℃ was 8.00%, 8.45%, 6.53%, 5.21% and the relative safe water content was 9.74%, 9.85%, 8.40%, 7.27%, respectively. Conclusion: Oswin model can be used to predict the equilibrium moisture content of RRR in storage, which can provide reference for the control of safe moisture and scientific maintenance of RRR.
ABSTRACT
Objective: To study the correlation between the content changes of main medicinal ingredients and the color values of Rhei Radix et Rhizoma during storage based on the principle of chromaticity analysis,and to provide reference for studying on the mechanism of discoloration and improving the quality evaluation of Rhei Radix et Rhizoma. Method: Simulated accelerated test was adopted in this study, where Rhei Radix et Rhizoma was stored under high temperature(40±5)℃,high humidity RH(92.5±5)%and strong light(4 000±500)Lx conditions to accelerate its discoloration. For the samples taken at different time points,the color value was determined by spectrophotometer and the total contents of anthraquinone and free anthraquinones,sennoside A,B,catechin and gallic acid were determined by high performance liquid chromatography (HPLC). The correlation between the effective components and the color value of rhubarb was analyzed by SPSS software. Result: During the storage process,it was observed by the eye that the color of Rhei Radix et Rhizoma was significantly darker and darker in the simulated acceleration test. According to the analysis of the chromaticity value results,the changes of chromaticity values L*and E*ab of Rhei Radix et Rhizoma were significantly negatively correlated with free strontium content(PPa* was significantly negatively correlated with gallic acid(PPConclusion: There is a certain correlation between the change of color value and the content of six medicinal ingredients during Rhei Radix et Rhizoma storage.