Hard endosperms, composition

Figure 4.3.3, A and B, shows a typical NIR chemical image and a reflectance spectrum acquired in the hard endosperm structure of the kernel. Although each image cube visualizes the biochemical composition of specific morphological structures at each physical depth into the sample, all of the data sets can also be assembled to constmct an image of the three-dimensional distribution of the chemical components of interest. The individual image cubes are first processed, using a commercially available software package (ISys 3.0, Spectral Dimensions, Ine.), by first subtracting...

The subject of the secondary protein structure as a means of defining the performance characteristics ofwheat endosperm-known as hardness-been explored over a seven year period [39, 40]. Another approach, taken by Baron et al., involves the IMS imaging of the endosperm cell walls rather than of the protein found in the endosperm itself [61]. All of these authors performed the imaging in situ, following removal of the protein and starch, in order to study the compositional and architectural heterogeneity and, in relation to this, wheat hardness. In this case, the research was focused on kernel hardness rather than on endosperm hardness, as was the case with our studies. A further study of carbohydrate polymers by the same group involved the investigation of cereal arabinoxylans in relation to their structure and physico-chemical properties. 

Barron, C., Parker, M.L, Mills, E.N.C. and Rouau, X. (2005) FTIR imaging of wheat endosperm cell walls in situ reveals compositional and architectural heterogeneity related to grain hardness. Planta, 220, 557-77. 

RP-HPLC of storage proteins can also predict quality in other cereals. In barley, RP-HPLC of hordeins [112,224] and high-MW glutelins [225] can reveal malting quality. In maize, Paulis et al. [226] showed by RP-HPLC that there are more y-zeins in quality protein maize than in normal maize this relates to lysine content and nutritional quality. RP-HPLC can relate protein composition to kernel hardness, density, and vitreosity of both normal maize and quality protein maize genotypes [227-229]. Differences between alcohol-soluble proteins of hard and soft endosperm of normal and quality protein maize show that the zein distribution influences kernel texture and hardness [230-232]. 

In order to understand the important changes that cereals undergo during processing, it is essential to comprehend the macro and micro structure, physiology, biochemistry, and composition of each anatomical part of the caryopsis. The structure and the appearance of cereals have been modified by breeding. Within each type of cereal, important variations exist in endosperm hardness due to the different proportions of vitreous and floury endosperm types, pericarp color and thickness, type of starch, and kernel size. 

---