Kinetic of the hydrolysis of pectin galacturonic acid chains and quantification by ionic chromatography

These experiments were designed to develop a rapid, repeatable and accurate analysis method for the quantification of galacturonic acid of pectins. Different pectin hydrolysis procedures (chemical and enzymatic) were carried out with H2SO4, TFA and HCl at different acid concentrations (0.2, 1 and 2 M) and temperatures (80 and 100 °C). Enzymatic and combined chemical and enzymatic hydrolysis of pectin were also studied. A acid hydrolysis under drastic conditions (100 °C) is insufficient for complete hydrolysis and results in low recovery of galacturonic acid residues. Mild chemical hydrolysis (0.2, 1 and 2 M H2SO4 72 h at 80 °C) is also insufficient for complete depolymerization. Its main advantage is cleavage of the galacturonic acid chains into oligomeric forms without any degradation within 72 h of hydrolysis. However, enzymatic hydrolysis with VL9 for 2 h at 50 °C and combined chemical and enzymatic hydrolysis (0.2 M TFA at 80 °C for 72 h and VL9) give high recovery of this acid. Analysis of the liberated sugar residue by HPAEC allows us to determine the galacturonic acid composition of this polysaccharide accurately with high selectivity and sensitivity in one assay without the need for derivatization.