Kinetic model of pectin demethylation

CONSTENLA, D.; LOZANO, J.E.

LATIN AMERICAN APPLIED RESEARCH

PLAPIQUI(UNS-CONICET)

Lugar: BAHIA BLANCA; Año: 2003 vol. 33 p. 91 - 95

0327-0793

Abstract−− Pectins are polysaccharides that actas a cellular binder in the peel of many differentfruits and vegetables. An important feature ofpectins is the esterification of the galacturonic acidresidues with methanol. The degree of methylationis defined as the number of moles of methanol per100 moles of galacturonic acid. The objective of thepresent work was to study the acid demethylation ofapple pectin at different temperatures, by followingchanges in the degree of methylation. A solution ofhigh methoxyl apple pectin was demethylated withconcentrated HCl (pH = 0.5). The processes werecarried out for 120 min at T = 80°C and 400 min atT = 65°C and T = 50°C. Anhydrogalacturonic acidcontent, degree of methylation and intrinsicviscosity as a function of reaction time weredetermined. Results showed pectin demethylationfollowed a second order kinetics and demethylationrate increased exponentially with temperature.Results also showed pectin ?purity?, asanhydrogalacturonic acid content, increased withdemethylation. However, intrinsic viscosity reducedwith reaction time. This behavior was associatedwith the hydrolysis of non-polyuronic materialduring the acid treatment, lowering in that way theaverage molecular weight.Keywords−− Pectin, Demethylation, Kineticmodel, Bio-polymer, Low methoxyl.