73D-17 |
Effect of ionizing radiation on tensile properties of zein films |
Q. WANG, Dept. of Food Science & Human Nutrition, Univ. of Illinois, Urbana-Champaign, 382-D AESB, 1304 W. Pennsylvinia Ave., Urbana, IL 61801 and G. W. Padua. Previous research has indicated the potential of corn zein films for biodegradable food packaging. However, improvements to their physical properties are necessary to increase serviceability. Ionizing radiation, routinely applied for polymer modification, offers the possibility of cross-linking effects without the addition of non food-grade chemicals. Our objective was to investigate the effect of gamma (Cobalt-60) rays on tensile properties of zein films containing 33% or 46% (w/w) oleic acid as plasticizer. Zein resins were prepared by precipitating aqueous ethanol dispersions of zein and oleic acids in cold water. Films were formed by extending the resins over rigid frames and allowing them to dry in air. Laminated zein films were prepared by pressing 3 layers of regular zein films in a Carver press (210°F, 275 tons/in2). Sample films were irradiated under vacuum with a Co-60 source (dose rate 23.4 KGy/hr) to doses ranging from 0 to 60 KGy. Tensile strength (TS), elongation (E), and Young’s Modulus (YM) were measured with an Instron Testing Machine following an ASTM standard method. Irradiation significantly affected tensile properties of zein films. TS of all samples increased to a peak value at a dose of 20 KGy. It then decreased continuously with higher doses. E showed a reverse trend, falling sharply with the first 20 KGy then continue to decline slowly with higher doses. YM was not significantly affected by the radiation doses applied. Irradiated films showed achromatic discoloration. Data suggested that moderate radiation doses resulted in a net cross-linking effect over chain scission. However, at high radiation doses chain scission seemed to be the overriding effect. Careful manipulation of irradiation and plasticizer content may result in improved properties of zein films. More research is needed to investigate radiation mediated modifications to zein films.
Session 73D, Food Packaging
|