Developments in the Science of Zein, Kafirin, and Gluten Protein Bioplastic Materials

Abstract

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 2 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.

Functionality of the storage proteins in gluten-free cereals and pseudocereals in dough systems

“…Also, both zein and kafirin are considerably more hydrophobic than gluten.. Presumably as a consequence of their greater hydrophobicity and different secondary structure, zein and kafirin have a higher glass transition temperature (T g ) than gluten (Taylor et al, 2013a). The prolamins of pearl millet, pennisetin, whilst less studied, are considered to be similar to α-zein in structure (Bugs et al, 2004).…”

Role of γ-Kafirin in the Formation and Organization of Kafirin Microstructures

“…Without this, the structure of the microparticles would be destabilized, as demonstrated. This suggestion is based on a model for kafirin microparticles formation 17 using an analogy of protein body formation but in an isolated and non-cellular system. The model describes that the microparticles form by precipitation of α-and β-kafirin around small particles of undissolved kafirin and then the γ-kafirin forms a stabilizing layer on the surface of the partially formed microparticle.…”

Identification of peanut seed prolamins with an antifungal role by 2D-GE and drought treatment

“…All prolamins are recognized water insoluble in their native conformation in protein bodies within endoplasmic reticulum originated vacuoles, and they are extractable in water/alcohol mixtures. 39) Despite predominant content of hydrophobic amino acid residues, prolamins from different cereal seeds have different hydrophilic characteristic. 39,40) It was evident that a number of prolamins in wheat, barley, and rye could be directly extracted in water or 0.5 M NaCl at room temperature.…”

“…39) Despite predominant content of hydrophobic amino acid residues, prolamins from different cereal seeds have different hydrophilic characteristic. 39,40) It was evident that a number of prolamins in wheat, barley, and rye could be directly extracted in water or 0.5 M NaCl at room temperature. 41) These prolamins probably exhibit their water solubility once vacuolar free.…”