Spatial Distribution of Protein and Phenolic Constituents in Wheat Grain as Probed by Confocal Raman Microspectroscopy

Abstract

Confocal Raman microspectroscopy is an appropriate method to investigate the microscopic structure of a wheat grain. The technique does not require any destructive preparation of the sample and is rapidly performed. The high spatial resolution reveals molecular and chemical heterogeneity within cellular dimensions. Using specific vibration bands as markers, the technique permits reconstruction of spectral images. The different components of wheat ( Triticum aestivum) were chemically and structurally characterised by Raman microspectroscopy. The work was focused on the protein content and composition of the starchy endosperm and on the composition of the aleurone cells walls in arabinoxylan and ferulic acid derivatives. Particular attention was given to these components because of their role in cohesion of the starch–protein matrix interface and of the endosperm–envelope interface. Confocal Raman microscopy was also used to follow the evolution of protein content and structure during grain development of various wheat varieties selected on the basis of hardness level and aptitude to separation of peripheral layers during milling.