Structural and rheological properties of pectic polysaccharide extracted from Ulmus davidiana esterified by succinic acid

The present study was carried out to investigate the physicochemical and structural properties of pectic polysaccharide extracted from Ulmus davidiana (UDP) and to determine the physicochemical, structural, and rheological properties of esterified UDP with succinic acid (ES-UDP). The results indicated that UDP had high amounts of galacturonic acids and various neutral sugars, such as galactose, rhamnose, and glucose. UDP was identified as a low methoxyl pectin, consisting of 1,4-linked α-d-GalpA (the main backbone chain), supported by the results of Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction, and 1D Nuclear magnetic resonance (NMR) spectroscopy. In the FT-IR and XRD, no difference was detected between UPD and ES-UDPs. However, 1H and 13C NMR spectra revealed that the new ester bonds were formed between a hydroxyl group of UDP and a carboxyl group of succinic acid during esterification. In the steady shear rheological analysis, the consistency index (K) of ES-UDP was significantly higher than that of UDP and increased significantly with increasing concentration of succinic acid. In the dynamic rheological analysis, the tan δ values of all ES-UDP solutions were significantly lower than those of the UDP solution.