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.