Investigation by confocal Raman microspectroscopy of the molecular factorsresponsible for grain cohesion in the Triticum aestivum bread wheat. Role of the cell walls in the starchy endosperm

Confocal Raman microspectroscopy has previously been employed to investigat e the protein content and composition of the starchy endosperm of the wheat grain With the same objective, that is to determine the molecular basis of grain cohesion and more specifically of kernel hardness, the Contribution of endosperm cell walls in the kernel structure and cohesion was explored. The technique showed that endosperm cell walls consist not only of arabinox ylan chains with ramifications of ferulic esters. but also of others compon ents such as proteins and lipids that could play some role in the mechanica l properties of the endosperm cell walls, A new model of interaction betwee n ferulic ramifications and a phospholipid component was proposed. The inve stigation of cell all composition at successive Stages of grain development revealed a decrease in the protein to arabinoxylan ratio and simultaneousl y an increase of the ferulic acid to arabinoxylan ratio that could be assoc iated with a strengthening of the cell wall structure. The study confirms t he effectiveness of confocal Raman microspectroscopy to approach the struct ure of wheat grain at the micrometer scale and to identify specific molecul ar factors responsible for grain cohesion and involved in the fracture mode s generated during the milling process, (C) 2001 Academic Press.