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

Abstract 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 °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 °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.