Pectins from the pulp of gabiroba (Campomanesia xanthocarpa Berg): Structural characterization and rheological behavior

The pulp of gabiroba fruits was submitted to a hot water extraction, giving rise to a crude pectin named GW. GW was shown to be composed mainly of arabinose (54.5%), galacturonic acid (33.5%), galactose (7.6%), and rhamnose (1.6%). GW was characterized by chromatographic and spectroscopic methods indicating the presence of homogalacturonans (HG) with a degree of methyl-esterification (DM) of 60% and rhamnogalacturonans I (RG-I). HG domain represents 31.9% and RG-I domain 65.3%. Furthermore, GW was submitted to sequential fractionation methods, giving rise to GWP-TEP fraction, structurally characterized by the predominance of HG regions, and confirmed by NMR analysis. The rheological behavior of GW was analyzed at 1%, 3%, and 5% (w/v) concentration with 0.1 mol L^-1 NaCl. All samples showed shear thinning behavior. In the oscillatory measurements, the 1% GW showed a liquid-like behavior, while the 3% presented a concentrated solution behavior and the 5% GW a gel behavior.