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Molecular bases of kernel hardness as probed by confocal Raman microspectroscopy: An investigation on
the role of endosperm cell walls. O. PIOT (1), J. C. Autran (2), and M. Manfait (1). (1) Laboratoire de
Spectroscopie Biomoléculaire, Université de Reims; (2) Unité de Technologie des Céréales et des
Agropolymères, INRA Montpellier.
In order to optimize the milling of Triticum aestivum wheat
grains, we have undertaken to study the molecular bases of the grain cohesion. After having characterized
the starch granule - protein matrix interface within the central starchy endosperm, and established a
correlation between the a helical secondary structure of interstitial proteins (protein content between starch
granules) and kernel hardness, we are presently looking more into the role of endosperm cell walls in the
adhesive forces which maintain the kernel structure. To do so, we are employing confocal Raman
microspectroscopy. We have shown that arabinoxylans chains (main component of the cell walls ramified
by esterified ferulic acid) could be linked to proteins and, more surprisingly to lipids (phospholipids), via
ferulic esters. Furthermore, by following the evolution of cell walls at different maturation stages (during
the period of ripening and desiccation of the grain,), we have observed that, within the cell walls, the ferulic
content increases while the protein content decreases when the kernel hardens. The modification of the
molecular organization in the walls would reflect their reinforcement upon ripening. These results show that
Raman microspectroscopy is a very efficient technique in establishing certain bases of the grain cohesion,
implicating the central endosperm cell walls.
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