CELL-WALL POLYSACCHARIDES OF KIWIFRUIT (ACTINIDIA-DELICIOSA) - EFFECT OF RIPENING ON THE STRUCTURAL FEATURES OF CELL-WALL MATERIALS

Cell-wall polysaccharides were solubilised from cell-wall materials (CWMs) isolated from kiwifruit at 2 ripening stages, after treatment for 1 and 7 days with ethylene. The fractions soluble in cyclohexane-trans-1, 2-diaminetetra-acetate(CDTA), Na2CO3, guanidinium thiocyanate (GTC), and KOH were purified by ion-exchange and gel-permeation chromatography, and subjected to methylation analysis. The pectic polymers in the 7-day fractions had increased proportions of 4-linked galactosyl, 2- and 2,4-linked rhamnosyl, and terminal arabinosyl, xylosyl, and galactosyl residues, and decreased proportions of 4-linked galacturonosyl residues. In the major Na2CO3-soluble pectic fraction, there was an increase in the proportion of branched polymers of high molecular weight during ripening. Therefore, a large proportion of the polyuronides may have been solubilised without significant structural modification, indicating that the action of endo-polygalacturonase was not involved. There was a decrease in M(w) of the xyloglucan fraction during ripening, but no detectable changes in the primary structure or in the 4-O-methylglucuronoxylan and galactoglucomannan fractions.