Formation of ferulic acid dehydrodimers through oxidative cross-linking of sugar beet pectin

Pectins isolated from sugar beet pulp by autoclaving contained significant amounts of ferulates, 8.8% of which were ferulate dehydrodimers. The 8-8 and 8-O-4 dehydrodimers were predominant. Oxidative cross-linking with hydrogen peroxide/peroxidase lowered the amount of ferulic acid by 78%, while an increase in ferulate dehydrodimers by a factor of 4.9 was observed. The highest increase was seen for the 8-5 and 8-O-4 dehydrodimers. The concentration of total ferulates decreased by 36% after cross-linking, indicating that a part of the ferulates were converted to unidentified oxidation products, It was concluded that ferulic acid in beet pulp pectin is coupled into a variety of dehydrodimers by treatments that mediate oxidative cross-linking reactions. (C) 1997 Elsevier Science Ltd.