Pectins differing in their degree and pattern of methylesterification are important in diverse aspects of plant physiology and also in many industrial applications. Determination of methylesterification fine structure and knowledge of enzyme specificities in modification and fragmentation of pectin are key to understanding the relationship between structure and function. The development of methodologies for the detection, separation and sequencing of different partially methylesterified oligogalacturonides (Me-OGAs) is consequently very important. Polysaccharide analysis using carbohydrate gel electrophoresis (PACE) has been shown to be powerful for the quantitative resolution of species different in degree of polymerization (DP) and/or degree of methylesterification (DM). Mass spectrometry (MS) has, to date, been the only tool with which to obtain isomeric information. However, it is not quantitative, and the presence of isobaric species makes the interpretation of the fragmentation patterns complicated. Here, we present evidence that Me-OGAs with the same DP and DM but different patterns of methylesterification (structural isomers) can easily be separated and quantified using PACE.

Current interest in replacing fossil-fuel-derived polymers and materials in favor of renewable materials is high. An inherent difficulty with the use of biomass-derived polysaccharides and hemicelluloses in this context, however, is their stiffness and lack of flowability at temperatures relevant for thermal processing, which severely limits their capacity for thermal processing. Here, we present a modification that enables a heat-processable arabinoxylan (AX). The modification involves a ring-opening oxidation to a dialdehyde with subsequent reduction of the aldehydes to alcohol, to increase the number of OH groups, followed by an etherification with hydrophobic alkyl chains. The modified AX was successfully compression molded with heat into filmswhich become thermoplastic in behavior and highly flexibleand flows at temperatures above 130 °C. The films are stretchable up to 200%, and their strength and strain deformation are controlled by the degree of oxidation and substitution of the AX polymer. These findings are highly encouraging and open up the potential use of modified AX alone or as a composite in applications that include films, food packaging, and barriers via hot-melt processing techniques.

The in vitro and in vivo functionality of the anionic plant polysaccharide pectin depends not only on the amount of ion-binding groups attached to the polymer but also on the distribution of such groups along the backbone. It has been proposed recently that information regarding this intramolecular distribution can be quantified by defining a degree of blockiness (DB or DB(abs)), and the usefulness of such measures in discriminating qualitatively between pectins originating from different sources has been demonstrated. Despite this, the value of these parameters in predicting the pseudoequilibrium elastic modulus of gels remains untested. This study seeks to address this problem through the sourcing and in-house modification of a variety of pectins in order to produce a library of distinct representative fine structures. These were subsequently characterized in terms of their relevant properties, including the determination of the proposed DB and DB(abs), and the formation of gels of these samples was monitored using small deformation mechanical spectroscopy. In addition to ionotropic calcium gels the effect of the fine structure on acid gelation was also studied.