An autoclave with 500 mL working volume was used for pectin
extraction by subcritical water, in which a thermocouple and a
pressure gage were used to assay the temperature and pressure
inside the reactor. The raw material and distilled water were added
into the reactor with the solid to liquid ratio of 1:30. The extraction
temperature was set at 130 C, 150 C, 170 C for apple pomace
pectin extraction and 100 C, 120 C, 140 C for citrus peel pectin
extraction according to preliminary experiments. The extraction
time was set for 5 min. All the experiments were performed in
triplicate, with the average value reported.