INTRINSIC-VISCOSITY AND MOLECULAR-WEIGHT OF PECTIN COMPONENTS

A variety of fruit and vegetable by-products were extracted to recover and evaluate their pectins. Pectins were studied by high-performance size-exclusion chromatography with differential refractive index (d.r.i.) and differential pressure (d.p.) detection. Computer-aided curve fitting of chromatograms was employed to identify pectic components. For each kind of pectin, the experimental chromatograms from both detectors could be fitted by a linear combination of the same five macromolecular sized species. Combination of data from the d.r.i. and d.p. detectors enabled component and global intrinsic viscosities to be obtained. Universal calibration of the column set with a combination of broad dextran and narrow pullulan standards enabled component and global molecular weights to be obtained. Weight-average intrinsic viscosities, ranged from about 0.75 to 5.9 dL/g, whereas weight-average molecular weights ranged from about 61 to 182 x 10(3) for the various pectins. Polydispersities of the pectins ranged from about 3 to 11. Analysis by combining intrinsic viscosities with molecular weights and previously determined radii of gyration for the components led to the conclusion that the pectin components were aggregates.