Microwave-assisted extraction of lime pectin

Pectin was extracted from lime flavedo, albedo and pulp by employing microwave-assisted extraction (MAE) under pressure. Heating times ranged from 1 to 10 min. Optimal time of heating was 3 min. Molar mass, viscosity, radius of gyration and hydrated radius were found to decrease with heating time. At 3 min heating time, depending on the lime fraction which was extracted, weight average molar mass ranged from about 310,000 to 515,000 Da, and weight average intrinsic viscosities ranged from about 9.5 to 13 dL/g. Pectins dissolved in 0.05 sodium nitrate were characterized by HPSEC with online light scattering, dynamic light scattering and viscosity detection. Molar mass polydispersity passed through maximum at 4 min. Molecules of pectin became less compact with increasing heating time. The results obtained here are consistent with previous evidence that extracted pectins may exist in solution as networks, partially formed networks, i.e. branched molecules or linear molecules depending on extraction conditions and the solvent in which they are dissolved.