Submitted to: Phytochemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/4/1996
Publication Date: N/A
Interpretive Summary: Plants have adapted to a harsh terrestrial environment by building cell walls that are strong and supportive. As with building wooden structures, one way to add structural strength is to cross-brace the components. In the case of a building, individual planks of lumber can be cross-braced. With plant cell walls, individual polysaccharide chains can be chemically cross- -linked. We recently discovered a whole new class of compounds that can cross-link plant cell walls. It is increasingly found that these "diferulates" have a remarkable effect on the strength and properties of the wall and on the textures that we come to savor when eating certain plants. For example the crunchiness of water chestnuts, even after cooking, in Chinese cuisine appears to be largely attributable to diferulate cross- links. In a collaborated study with a group from the French National Institute for Agronomic Research, we sought to determine if diferulates were responsible for the difficulty in obtaining all of the polysaccharide and sugar from sugar-beet. Indeed, sugar-beet was found to contain the entire class of diferulates. The amount could be increased by treating the sugar-beet pulp under oxidizing conditions. The cross-links were resistant to enzyme treatments that are commonly used to improve sugar yields from the pulps. Having now identified a significant mechanism for the difficulty of obtaining maximum sugar from sugar-beet pulps, ways to remove diferulates and release more sugars will be examined.
Technical Abstract: The occurrence of diferulic acids in sugar beet pulp and the possibility of releasing them by enzymic treatment has been investigated. Sugar-beet pulp contained dehydrodimers of ferulic acid arising from 8-5', 5-5', 8-8', and 8-O-4' coupling, the 8-5' form being preponderant. No 4-O-5' dimer was detected. Total dehydrodimers represented 0.14% of the pulp dry matter. Their release was attempted by treatment of the pulp with a commercial pectinase. However, diferulates were resistant to the enzymic hydrolysis; free diferulic acids were not released and remained esterified to residual structures in the sugar beet pectins.