Rapid HPLC method to screen pectins for heterogeneity in methyl-esterification and amidation

Functionality of pectins as a food ingredient is strongly related to their chemical fine structure. Chemical characteristics of pectins are determined by many different parameters in their manufacture (choice of the raw material and extraction conditions). Pectin companies are thus in need of rapid methods to check the performance of extracted pectins. An important factor in the characterisation is the homogeneity of the pectin preparation, which is usually determined by laborious, time consuming, soft gel based chromatographic procedures. An HPLC method with a weak anion exchange column (WAX column) was found to discriminate between commercial pectins efficiently: pectins with similar DM (degree of methyl-esterification) or similar DS (degree of substitution: methyl-esters and amide groups) having different physical properties showed various populations. Furthermore the pectins with a blockwise or random distribution of the substituents showed different elution profiles. This indicates that the WAX column is sensitive not only to the amount of substituents but also to the distribution of these substituents.