EXTRACTION AND CHARACTERIZATION OF WATER-SOLUBLE PECTIC SUBSTANCES FROM GUAVA (PSIDIUM-GUAJAVA']JAVA L)

Water-soluble pectic substances (CP-endo and CP-meso) were extracted from the alcohol-insoluble residues of fresh endocarp and mesocarp of white guavas (cv. Supreme) and fractionated by ion-exchange chromatography into minor neutral (NP-endo and NP-meso) and major acidic pectic substances (AP-endo and AP-meso). The neutral fractions contained mainly arabinose, galactose, and glucose, and methylation analysis revealed xyloglucans, highly branched arabinans, and type I arabinogalactans, together with arabino-3,6-galactan-proteins that interacted with the Yariv antigen. The APs contained 72 80% of galacturonic acid together with 16-19% of arabinose, galactose, and rhamnose, were heterogeneous in size-exclusion chromatography, differed greatly in their degrees of methyl esterification (21.9 and 88.0% for AP-endo and AP-meso, respectively) and acetylation (16.0 and 2.0%), and had typical rhamnogalacturonan structures with neutral side chains of densely substituted arabinans and arabinogalactans of both types. Weak intrinsic viscosities [eta] (13 and 26 mL/g for AP-endo and AP-meso. respectively) reflected low hydrodynamic volumes for guava pectins.