Abstract:

Pectinmethylesterase (PME, E.C.1.1.11) isoenzymes from Valencia orange prepns. with different specific activities were used to de-esterify citrus and sugar beet pectins. Enzymic modification offers the opportunity to create pectins of tailored functionality and gelling ability. Based on NMR spectra, catalysis by all PME exts. produced block-wise de-esterification patterns in both citrus and sugar beet pectins. PME activity resulted in increased nos. of contiguous de-esterified groups and decreased nos. of contiguous esterified groups. De-esterification by PMEs increased the elastic property (G') of citrus and sugar beet pectins in the presence of calcium from 10 to 571 and from 0.05 to 201 Pa, resp. The results demonstrate the predilection of citrus PMEs toward block wise de-esterification of pectins and the relationship between calcium binding ability and de-esterification degree and patterning. Within a narrow range of de-esterification (37-48%) and with a narrow distribution of contiguous groups, PME modification did not markedly change gelling ability. At lower or higher de-esterification values, a 2-fold increase or 50-fold decrease, resp. in G' values was obsd. [on SciFinder(R)]