Chemical properties of water-soluble pectins in hot- and cold-break tomato pastes

Tomato fruit paste prepared by hot-or cold-break processing was extracted with water to obtain a water-soluble pectin (HP or CP) and a water-insoluble matter (HR or CR). HP yield was approximately twice that of CP, while those of the water-insoluble matters were similar. Comparing sugar compositions, HP (GalA-rich) was remarkably different from CP (neutral sugars-rich), although their water-insoluble matters were similar. This result indicates that the solubilizations of cell-wall-associated pectins in HB and CB were similar, but the release of GalA by endogenous pectin-degrading enzymes in CB was remarkable. ons separated by a DEAE–cellulose column from HP (HP3, HP4, HP5) were also rich in GalA, while those from CP (CP2, CP3, CP4) were all rich in neutral sugar. However, the ratios of individual sugars of CP fractions were very different. Unlike the neutral sugar-rich fractions, the GalA-rich ones treated with polygalacturonase were mostly degraded. In addition, the chemical structure of HP5 (homogalacturonan) and CP4 (rhamnogalacturonan) were compared after mild acid hydrolysis.