Effect of methoxy-esters distribution pattern on the rheological properties of pectin-calcium gels: Toward understanding pectin structure-function relations

The extensive use of pectin as a multi-functional ingredient in food, nutraceutical and pharmaceutical industries prompts the necessity for gaining insight on the polymer structure-function relations. Accordingly, this work aims at relating the changes in rheological characteristics of pectin-calcium gels to detailed pectin structural features. Consequently, highly methoxylated citrus pectin was subjected to controlled de-methoxylation, using Daucus carota pectin methylesterase (PME), Aspergillus aculeatus PME or sodium hydroxide saponification yielding P-, F- and C-pectins. These partially de-methoxylated pectins (PDMPs) of varying degree and pattern of methoxylation were characterised in terms of degree of methoxylation (DM) and distribution pattern of methoxy-esters. The latter characteristic was quantified based on the absolute degree of blockiness (DBabs) and the proportions of non-methoxylated mono- di- and tri-galacturonic acid (NM-MDT-GalA) liberated after an endo-polygalacturonase depolymerisation of PDMPs. Upon pectin characterisation, pectin-calcium gels were prepared and gel strength assessed by means of small deformation oscillatory measurements.status: publishe