Location: Plant Polymer Research
2007 Annual Report
At present there are few applications for corn germ proteins. This is mainly due to a lack of inexpensive raw material. Research has been conducted to determine if the addition of reducing agents and denaturants (sodium dodecyl sulfate, urea, Beta-mercaptoethanol) in the extracting solvent (0.1N NaC1) improved the amount of protein removed from corn germ. For the variables tested, improved yields were not obtained relative to the incumbent technologies. Future efforts will utilize proteases (papain, bromelain) during extraction to increase protein yield.
The cost of commercial zein is too high to replace incumbent bulk synthetic polymers. The use of acetic acid to extract zein from corn gluten meal, distillers dry grains and corn meal was evaluated in order to determine if it would be more effective than incumbent technologies. Acetic acid was found to be more effective than aqueous ethanol or high-temperature ethanol extraction providing zein of good quality.
An improved understanding of the molecular structure of zein and of zein aggregates will be of use for the development of new products. Near and far-UV (ultra-violet light) CD (circular dichroism) experiments were carried out on zein solutions to determine how the secondary and tertiary structure of zein changes with either changes in solvent or in temperature. Both the secondary and tertiary structure of zein was found to undergo reversible changes with heat when performed in 80% ethanol/water. The structure of zein was found to change with the use of alternative solvents. A fluorscent probe, diphenylhexatriene, which attaches to the hydrophobic sites on zein microspheres was used to demonstrate the tightness of probe binding at various temperatures by using anisotropy measurements.
The physical properties of zein are deficient relative to certain synthetic alternatives. In order to develop new applications for zein, cross-linking reagents were used to improve the physical properties of zein. It was determined that treatment of zein with either glutaraldehyde or glyoxal can provide zein with improved tensile strength. The magnitude of the improvements was equivalent to or greater than the historical zein cross-linking reagent formaldehyde. Each reagent also provided increased resistance to solvents as well. The elongation of the modified zein is still deficient relative to synthetics. The rheological properties of these modified zeins were also studied.
A provisional patent, No. 11/728700, entitled "Decolorization/Deodorization of Corn Zein Products" was filed 03/27/2007. The research described in the application addressed the high color and off-taste of zein. A pilot plant batch process is in construction.
Production of zein fiber using acetic acid as solvent. Techniques need to be developed to produce fabric samples easily in a lab setting. Acetic acid provided fibers with a round cross-section and or smaller diameter than previous solvent systems. Non-woven mats obtained can be used to develop information that will be of use in re-introducing zein into the fiber market.
This work was performed under NP 306, Quality and Utilization of Agricultrual Products and addresses Problem Statement 2c, New and Improved Processes and Feedstocks.
Hojillaevangelist, M.P., Evangelista, R.L. 2006. Effects of cooking and screw-pressing on functional properties of Cuphea PSR23 seed proteins. Journal of the American Oil Chemists' Society. 83:(8):713-718.
Lawton Jr, J.W. 2006. Isolation of zein using 100% ethanol. Cereal Chemistry. 83(5):565-568.
Selling, G.W., Sessa, D.J. 2006. Multivalent carboxylic acids to modify the properties of zein. Industrial Crops and Products. 25:(1)63-69.
Selling, G.W., Biswas, A., Patel, A., Walls, D.J., Dunlap, C.A., Wei, Y. 2007. Impact of solvent on electrospinning of zein and analysis of resulting fibers. Biomacromolecules. 208:(9)1002-1010.
Selling, G.W., Hamaker, S.A., Sessa, D.J. 2007. Effect of solvent and temperature on secondary and tertiary structure of zein by circular dichroism. Cereal Chemistry. 84:(3)265-270.
Sessa, D.J., Mohamed, A., Byars, J.A., Hamaker, S., Selling, G.W. 2007. Properties of films from corn zein reacted with glutaraldehyde. Journal of Applied Polymer Science. 105:2877-2883.
Mohamed, A., Hojilla-Evangelista, M.P., Peterson, S.C., Biresaw, G. 2007. Barley protein isolate: thermal, functional, rheological and surface properties. Journal of the American Oil Chemists' Society. 84(3):281-288.