To determine the most appropriate solid to solvent ratio to extract pectin, rind to water ratios of 1:10–1:30 were used in this study and the results were in Fig. 2c, e–f. As shown in figures, the pectin extraction was significantly increased up to the solid-to-liquid ratio of 1:20.3. The pectin content was decreased with the further increase in solid-to-liquid ratio. The solvent (water) can efficiently absorb microwave energy and leads to enhance swelling of plant material, which is favorable to increase the contact surface area between the plant matrix and the solvent, resulting in increases the extraction yield of pectin up to solid–liquid ratio of 1:20.3. But, higher solvent would decrease the microwave adsorption of material, because more energy was absorbed by the solvent.Therefore, the break of material cell wall and mass transmission might be negatively influenced (Li et al., 2010) and decreased the pectin yield.