Extraction of valuable compounds from the flavedo of Citrus junos using subcritical water

Pectin contained in the flavedo of citrus fruits was sequentially extracted with water, a chelating agent, and hydrochloric acid. The amount of pectin obtained was quantified as the amount of galacturonic acid according to the dimethylphenol method and found to be 21%. Next, pectin was separated from the flavedo of Citrus junos with hot compressed water (HCW) using a semi-continuous flow reactor. HCW was continuously delivered into the reactor while gradually increasing the temperature from 60 to 160 degrees C at 20 MPa with flow rates of 2.1, 3.5, and 7.0 mL/min. The extract from the reactor was cooled and 7-mL fractions were collected. From the analysis of each fraction, it was found that pectin was rapidly extracted when the temperature of the reactor reached 160 degrees C. Yield of the pectin reached as high as 80%. From cation analysis, a large amount of potassium was detected in the leading extraction peak. (c) 2008 Published by Elsevier B.V.