Structural characterization of aroid starches by means of chromatographic techniques

Abstract

Starch functional properties are largely determined by the molecular structure. The weight average molar mass and radius of gyration can be calculated by the analysis of solubilized polymers using AF4-MALLS-DRI systems. The chain length distribution can be determined by analysing debranched starches by gel permeation chromatography (GPC) and high performance anion exchange chromatography (HPAEC-PAD). Aroid starches were used as study case for structure analysis with the abovementioned chromatographic techniques. Amylose and amylopectin chains from aroid starches exhibited weight-average molar mass (Mw) higher than 2.5 × 107 g mol−1 and 5.7 to 13 × 108 g mol−1, respectively. The relatively high values of Mw are correlated to high radius of gyration to both amylose and amylopectin molecules (253–291 nm and 311–410 nm, respectively). The hydrodynamic coefficient (υG) of amylose and amylopectin was 0.6–0.7 and 0.28–0.35, respectively, suggesting random coil conformation for amylose and spherical conformation for amylopectin. The conformation of amylopectin was confirmed by GPC and HPAEC-PAD with the presence of high population of short amylopectin chains (DP 6–12–30% and DP 13–24–50%).