NONFOOD UTILIZATION OF CEREAL AND SOY BASED CO-PRODUCTS
Location: Plant Polymer Research
Title: PROPERTIES OF FILMS FROM CORN ZEIN REACTED WITH GLUTARALDEHYDE
Submitted to: Journal of Applied Polymer Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: January 10, 2007
Publication Date: May 16, 2007
Citation: 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.
Interpretive Summary: With the production of ethanol approaching 4.5 billion gallons this year from over one billion bushels of corn, the need to utilize the co-products from that production is essential. Zein, the predominant protein in corn, is a valuable co-product that has numerous industrial and food applications because of its ability to form films. To better utilize that ability some of the film's mechanical properties require improvement. The research performed in this investigation demonstrated that the combined role of solvent with chemical modification using a bis-aldehyde can be used to generate films with improved tensile strength, ductility and stiffness, all essential to constructing a bio-based film derived from a renewable resource. The results of this research not only benefits the farmer and producers of ethanol from corn but also industrial markets including the medical industry for developing scaffolds for bone tissue engineering, the pharmaceutical industry for timed-release coatings, food markets including food coatings and biodegradable films for packaging and potential usage as an elastomer for chewing gum manufacture.
To improve the mechanical properties of zein films, a commercial white zein was reacted in glacial acetic acid (HAc) with glutaraldehyde (GDA) from 0.5 to 16% by weight based on the weight of zein. Amounts of 4% or higher GDA-modified zein, when cured in a closed system, generated a gel. That gel was insoluble in organic solvents known to solubilize zein. Zein solutions cast within a silicon rubber gasket sealed onto Teflon coated plates, when air dried, generated 0.7-0.9mm thick films. Those films from 8% GDA modified zein had a water vapor permeability of 5.9x10-8 gcm/Pasm2. Overall results indicate that our thicker films gave a higher water vapor permeability than values reported in the literature. Differential scanning calorimetry and dynamic mechanical analysis demonstrated a biphasic nature for those films that was attributed to HAc entrapped within the film matrix. The presence of residual HAc resulted in a lower glass transition temperature and a greater softening of the film samples. Physical testing of tensile bars cut from GDA-modified zein films showed minor enhancement of tensile strength, percent elongation, and Young's modulus in the 0.5% GDA-modified zein films which increased and leveled off with 4% or higher amounts of GDA for the modifications. When the 4% to 16% GDA results are averaged, the tensile strength for the modified zein films increased 1.8-fold as compared to unmodified zein control films. On the same note, percent elongation showed a 1.8-fold increase, and Young's modulus showed a 1.5-fold increase. GDA reaction with zein generated films with improved tensile strength, ductility and stiffness when compared with respective zein control films.