Background : Prepared Rehmanniae root (PRR) has been used as traditional medicine, and is one of the most important oriental herbal medicines. However, physical characteristics of PRR are not suitable for use in industry. This study was performed to suggest preparation method of PRR powder, and determine the physicochemical characteristics of PRR powder with different pre-freezing temperatures. Methods and Results : Moisture content, powder yield, particle size, bulk density, compressive stress, extraction yield, and 5-HMF content of PRR powders with different pre-freezing temperatures (-20℃, -40℃, -60℃, and -80℃) were analyzed, and correlation among these factors was determined. Powder yield increased and particle size decreased in a pre-freezing temperature-dependent manner from -20℃ to -60℃. Hausner ratio increased from 1.186 to 1.225 with decreasing temperature from -20℃ to -80℃, and compressive stress showed the opposite trend. Extraction yield and 5-HMF content were not significantly different between PRR and powder. Significant correlations were observed among pre-freezing temperature and physical characteristics (yield, particle size, hausner ratio, and compressive stress). Conclusion : These results suggest that pre-freezing temperature was important factors affecting physical characteristics of PRR powder, and the results of this study are industrially applicable to production of PRR powder.

Background : Rehmannia glutinosa root (R. root) has been used as traditional medicine, and is important resource for natural medicines and functional foods. However, R. root have catalpol which have bitterness, and undigested sugars, including stachyose, raffinose, and verbascose as main compounds, and these compounds can cause diarrhea and abdominal pain. Therefore, this study was performed to determine the changes in reducing sugar producted from undigested sugars and catalpol contents as a bitter taste compound in R. root with aging treatment conditions. Methods and Results : R. root was treated at 10 - 70℃ for 0 - 48 h, and extracted with 50% ethanol solution. Their catalpol content was analyzed using HPLC-UVD, reducing sugar content generated from undigested sugars was measured by the Nelson-Somogyi methods, and these reaction rates were calculated from their variation according to aging time and temperature. During aging treatment, reducing sugar content increased and catalpol content decreased. Their formation and degradation rates were highest at 50℃ and 30 - 40℃, and their rates were 1.89 ㎎/g·h and 23.09 - 23.33%/h, respectively. Conclusion : These results indicated that aging treatment can positively affect the sweetness and digestibility of R. root slurry. Therefore, aging treatment could be considered for improving the sensory qualities and digestibility of R. root.

Background: Rehmanniae radix preparata (RRP) has been used as a traditional medicine and is one of the most important oriental herbal medicines. However, the physical characteristics of RRP are not suitable for use in industry. The present study was undertaken to determined the preparation method of RRP powder and the physicochemical characteristics of RRP powder by milling under different pre-freezing temperatures. Methods and Results: Moisture content, powder yield, particle size, bulk density, compressive stress, extraction yield, and 5-HMF content of PRR powders by milling with pre-freezing temperatures (−20, −40, −60, and −80℃) were analyzed, and correlation among these factors was determined. Powder yield increased and particle size decreased in a pre-freezing temperature-dependent manner from −20 to −60℃. The Hausner ratio increased from 1.186 to 1.225 with decreasing temperature from −20 to −80℃, whereas compressive stress showed the opposite trend. Extraction yield and 5-HMF content were not significantly different between RRP powder. Significant correlations were observed among pre-freezing temperature and physical characteristics (e.g., yield, particle size, Hausner ratio, and compressive stress). Conclusions: These results suggest that the pre-freezing temperature is an important factor affecting the physical characteristics of PRR powder and applicable to the industrial production of RRP powder