Populations having different GalA blocks characteristics are present in commercial pectins which are chemically similar but have different functionalities

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.