Two commercially extracted pectins having different physical properties but similar chemical characteristics were fractionated into sub-populations using ion exchange chromatography. Individual sub-populations were characterised using established strategies (galacturonic acid and neutral sugar content, degree of methyl-esterification) including the use of enzymes (endo- and exo-polygalacturonases) as analytical tool. Some purified populations showed similar degree of methyl-esterification whereas they were eluting at different ionic strength. It was shown that these populations mainly differed in the number of galacturonic acid moieties in 'endo-polygalacturonase degradable blocks' and in the location of these blocks within the molecule. The size of the blocks present at the non-reducing end of the pectin was also different within the molecules. The separation of pectins on anion exchanger combined with the use of enzymes allowed us to differentiate pectic sub-populations. Commercial pectins appear to be a mixture of several polymers differing in total charge as well as in the distribution of the charges.
- galacturonic acid distribution
- size-exclusion chromatography
- intermolecular distribution
- exchange chromatography
- industrial pectins