Kinetic model of pectin demethylation

CONSTENLA, D.; LOZANO, J.E.

Santa fe

Congreso; 3 rd Mercosur Congress on Process Systems Engineering - 1st Mercosur Congress on Chemical Engineering (ENPROMER 2001; 2001

Abstract. Pectin has been used as gelling agents practically since the last two centuries. Pectins are linear polymers consisting almost entirely of D-galacturonic acid and galacturonic acid methyl ester residues. The objective of the present work was to study the acidic demethylation of a commercial apple pectin at different temperatures, by following changes in the degree of methylation (DM). A solution of high methoxyl apple pectin was demethylated with concentrated HCl (pH = 0.5). The processes were carried out for 80 min at T = 80°C; 225 min at T = 65°C and 270 min at T = 50°C. Anhydrogalacturonic acid content (AGA), degree of methylation and intrinsic viscosity [] as a function of reaction time were determined. Results showed pectin demethylation followed a second order kinetics and demethylation rate increased exponentially with temperature. Results also showed pectin ?purity?, as %AGA, increased with demethylation. However, [] reduced with DM. This behavior was associated to the hydrolysis of non-polyuronic material during the acid treatment, lowering in that way the average molecular weight