Structure of Coarse and Fine Fractions of Corn Samples Ground on the Stenvert Hardness Tester

Kernels from a pair of isogenic lines (with regard to hardness) and two commercial hybrids of dent corn (that varied in hardness) were ground on the Stenvert Hardness Tester and separated by sieving into coarse (\u3e0.710 mm) and fine (\u3c0.500 mm) fractions. The corn samples differed little in oil contents. The coarse particles from the hard corn samples were angular and sharp-edged; those from the soft corn samples were rounded. The yield of coarse particles was higher and they contained less oil in hard than in soft corn. Fine particles from all four corn samples had higher oil content than the coarse particles. Visual examination, observation at low magnification under a light microscope, and use of a scanning electron microscope revealed consistent differences in the extent and mode of corn kernel breakdown during grinding. Particles in the coarse fraction from hard kernels were to a large extent intact with little exposure of their contents. In the soft kernels, particles in the coarse fraction were broken extensively and their contents exposed. It is postulated that differences in the extent of mechanical breakdown and oil content are related to differences in shelf life of corn grits

Developments in the science of zein, kafirin, and gluten protein bioplastic materials

Despite much research, there are very few commercial prolamin bio-plastics. The major reason, apart from their high cost, is that they have inferior functional properties compared to synthetic polymer plastics. This is because the prolamins are complex, each consisting of several classes and sub-classes and the functional properties of their bio-plastics are greatly affected by water. Prolamin bio-plastics are produced by protein aggregation from a solvent or by thermoplastic processing. Recent research indicates that protein aggregation occurs by polypeptide self-assembly into nanostructures. Protein secondary structure in terms of α- helical and β-sheet structure seems to play a key, but incompletely understood role in assembly. Also, there is inadequate knowledge as to how these nanostructures further assemble and organize into the various forms of prolamin bio-plastics such as films, fibres, microparticles and scaffolds. Some improvements in bio-plastic functionality have been made by better prolamin solvation, plasticization, physical and chemical cross-linking, derivatization and blending with other polymers. The most promising area of commercialization is the biomedical field where the relative hydrophilicity, compatibility and biodegradability of particularly zein and kafirin are advantageous. With regard to biomedical applications, “supramolecular design” of prolamin bio-plastics through control over interand intramolecular weak interactions and SS/SH interchange between and within polypeptides appears to have considerable potential.University of Pretoria doctoral bursaryhttp://cerealchemistry.aaccnet.org/hb201