Valencia orange pectinmethylesterases, charge modification of pectins, and applications to food technology and drug delivery

Fractionation of Valencia orange pulp preparations resulted in PME active fractions containing putative PMEs of 13, 27, and 36 kDa. NMR analysis indicated that pectin desterification by PMEs in these fractions resulted in block wise de-esterification of the substrate. Within the narrow frequency range of 0.57 to 0.76 for the dyad or 0.22-0.55 for the triad, little effect on G' value near 560 Pa is observed. The relative contribution of total charge or distribution of charge cannot be clearly elucidated as the contribution of either depends on achieving a critical limit of de-esterification. The position and shape of this critical limit is influenced by the composition of the dyads and triads of carboxylic acid groups. Applications of charge modified pectins include the ability to interact with proteins, stabilize emulsions for entrapment of addenda and for drug release. Under low pH, cationic milk proteins interact readily with pectins, especially charge modified pectins. At pH 3.8, non fat dry milk, caseinates, αS1,2, β-but not Κ-casein precipitated, especially with modified pectin. Modified pectin apparently increased the solubility of sodium caseinate, suggesting a competition between protein-protein and protein-pectin interactions. Further, charge modified pectins reduced the surface tension and interfacial activity of dispersions and reduced the droplet size of emulsions. Finally, modified pectins showed superior entrapment and less release of indomethacin compared to commercial low methoxyl pectins.