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United States Department of Agriculture

Agricultural Research Service


Location: Plant Polymer Research

2008 Annual Report

1a.Objectives (from AD-416)
The primary goals for this project are to develop new chemistries and processes to enhance the utilization of co-products produced during cereal and soy processing, and bioethanol production thereby generating new markets for these co-products. The physical and chemical properties of the co-products will be characterized and their unique functional properties utilized to develop value added materials.

1b.Approach (from AD-416)
Characterize the structure and properties of zein to identify how zein fractions come together to form gels and aggregates. Characterize non-zein proteins from corn germ by-products of corn milling and identify potential applications. Investigate availability of chemically or enzymically functional groups by spectrofluorometry upon processing zein under heat and pressure as well as proteolyzing zein with enzymes such as trypsin, chymotrypsin and Alcalase.

3.Progress Report
At present there are few applications for corn germ proteins due to a lack of inexpensive raw materials. Work on using enzymes to improve protein extraction yields has been initiated. Studies with a commercial cellulase are still being formed to determine the optimal level of enzyme usage, but slight improvements in protein yields have been noted. Corn germ protein showed excellent foaming capacity, foam stability, emulsifying capacity and emulsion stability. The use of acetic acid to extract zein from distiller’s dry grains was further studied. It was found that as the temperature of the acetic acid was increased up to 145 degrees Celsius, the amount of material extracted increased. In general the quality of zein recovered was not as good as that obtained from corn gluten meal with the main impurity being corn oil. The inherent yellow color and off-odor of corn zein limits its usage in the medical, pharmaceutical, and cosmetic fields and also in applications as a paper coating, packaging material and biodegradable chewing gum base. Activated carbon is one of the best adsorbents of color and odor from zein. However, activated carbon also adsorbs protein. It was shown that treating zein aqueous ethanol solutions at 55 degrees C significantly enhanced the adsorptions of the color/odor components relative to protein. Intrinsic viscosity work was carried out to determine how molecular dimensions change with solvent. 90% Ethanol/water had a radius of gyration (rg) of 49 angstom (A). The biggest differences were observed with 90% methanol/water and acetic acid which had rg of 41 and 59 A respectively. Increased temperatures led to a reduction in rg. These changes in size are indicative of changes in molecular conformation which may alter the reaction of zein with certain reagents. Cross-linking zein with glutaraldehyde (GDA) proved beneficial for producing zein films with enhanced tensile strength and stiffness. A melt process was developed for modification of zein with GDA. The reaction appeared to take place with the N-terminous, the tyrosine, arginine, histidine and cysteine residues with self-oligomerized glutaraldehyde. Properties of melt GDA-zein articles were similar to those from solution processes. Zein fibers were electrospun after reaction with either glyoxal or formaldehyde in acetic acid. The fibrous mats were found to have tensile strengths three times higher than control. Significant changes in spinning conditions were required to obtain a quality mat due to the increased viscosity of the higher molecular weight material. The fibers were resistant to solvent dissolution after a brief thermal treatment. Mixing studies on the soybean meal-based plywood glue recipe using an improved version of the phenol-formaldehyde resin provided by our industry collaborator were undertaken. The soy meal-based formulation with the new resin did not pose any mixing or viscosity problems and was also spread easily on veneers. Bond strength testing is ongoing, but early results are promising. This research addresses NP 306, Component 2.

1. Production of solvent resistant zein fibers. Historically the main use of zein was in the textile market. In order for zein-based products to re-enter this market, articles must be produced that are solvent resistant. It was found that zein could be modified before spinning using glyoxal or formaldehyde to ultimately provide a fiber with improved solvent resistance. This technique avoids complicated downstream processing requiring potentially expensive safety equipment. Historic zein based fiber technologies required post fiber treatments using hazardous reagents to provide suitable fibers. This research demonstrates the ability to produce zein-based fiber that will be easier to transfer to industry. This research addresses NP 306, Component 2, Problem Area 2b.

2. Production of zein with reduced color and odor. The intense yellow color of zein and its odor will limit the penetration of zein into many markets. It is known that treatment of colored solutions, including zein solutions, with activated carbon will reduce color and odor. Unfortunately, this treatment will also reduce the protein content in the zein solution. By modifying processing conditions the amount of protein adsorbed on the charcoal is greatly reduced while still removing most of the color and odor. This technology will allow zein to be used in markets where low color or odor is important; these markets would include coatings and chewing gum. This research addresses NP 306, Component 2, Problem Area 2b.

5.Significant Activities that Support Special Target Populations

6.Technology Transfer

Number of New CRADAS1
Number of Active CRADAs1
Number of the New MTAs (providing only)1
Number of Non-Peer Reviewed Presentations and Proceedings1

Review Publications
Sessa, D.J., Palmquist, D.E. 2008. Effect of heat on the adsorption capacity of an activated carbon for decolorizing/deodorizing yellow zein. Bioresource Technology. 99(14):6360-6364.

Selling, G.W., Woods, K.K. 2008. Improved isolation of zein from corn gluten meal using acetic acid as solvent. Cereal Chemistry. 85(2):202–206.

Selling, G.W., Woods, K.K., Sessa, D.J., Biswas, A. 2008. Electrospun zein fibers using glutaraldehyde as the cross-linking reagent-effect of time and temperature. Macromolecular Chemistry and Physics. 209(10):1003-1011.

Woods, K.K., Selling, G.W. 2008. Melt reaction of zein with glyoxal to improve tensile strength and reduce solubility. Journal of Applied Polymer Science. 109(4):2375-2383.

Xu, J., Mohamed, A., Hojillaevangelist, M.P., Sessa, D.J. 2008. Rheology of defatted ultrafiltration-diafiltration soy proteins. American Journal of Food Technology. 3(5):294-302.

Last Modified: 4/20/2014
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