Comparisons between different techniques for water-based extraction of pectin from orange peels

Microwave and conventional methods have been used to extract pectin from orange peels, with different extraction periods, different solvent pHs and different types of solvent systems. For microwave extraction, the greatest total amount of pectin yield was found to be 5.27% on a dry basis for 15 min of extraction, although the greatest amount of material per unit time (%/min) was obtained after 5 min, which was the same amount as that extracted using Soxhlet extraction for 3 h. The relative extraction rate between microwave and Soxhlet extraction was similar to that in previous work. Microwave treatment was further investigated at pHs of 1.5, 2.0, 5.5 and 10.0 for 15-min extraction periods, with the greatest amount of pectin being extracted at the most strongly acidic condition of pH 1.5. Fifteen-minute extraction periods and a pH of 1.5 were also studied with solvent systems containing ethanol and EDTA (ethylenediamine tetraacetic acid); giving approximately double the amount of pectin extracted using distilled water.