Comparison of Analytical Methods for Determining Methylesterification and Acetylation of Pectin

Abstract

The esterification of galacturonic acid with methanol and/or acetic acid is important for the structural analysis of pectin. Although several methods have been reported for determining the degree of methylesterification (DM) and acetylation (DAc), the present study compares and optimizes three methods (titration, FT-IR and HPLC) using commercial citrus pectin (CP). Our results showed that the DM of CP was 47.0%, 47.6% and 48.0% as determined by titration, FT-IR and HPLC, respectively, suggesting that DM determination is nearly identical using any of these methods. However, the titration approach requires more sample than the other two. HPLC showed that the DAc of CP was 1.6%, an approach that can be used to determine the DM and DAc of pectin simultaneously. Here, we simplified and optimized sample treatment for HPLC analysis and compared it with the reported literature. Our results provide useful information for choosing appropriate methods for determining the DM and DAc of pectin based on various sample properties and experimental conditions.