Oxidative cross-linking of three beet pectin extracts with hydrogen peroxid
e/peroxidase resulted in an increase in viscosity at low concentrations and
in the formation of a gel at higher concentrations. Gels were formed using
concentrations of 1.5% for an autoclave preparation and one obtained by an
acid extraction and of 3% for a second autoclaved extract. It was shown th
at in the autoclave extracts only rhamnogalacturonans and possibly the arab
inans participated in the cross-linking reaction. Cross-linking of the auto
clave extracts with ammonium persulfate resulted in a decrease in reduced v
iscosity and molecular weight, although ferulic acid dehydrodimers were for
med. Treatment of the acid extracted pectin with ammonium persulfate gave a
slow increase in viscosity and the formation of a high-molecular-weight po
pulation was observed. For both oxidative systems, the 8-5 dehydrodimer was
predominant after cross-linking. (C) 2000 Elsevier Science Ltd. All rights
reserved.