27-4 |
Blown extrusion of zein films |
Y. WANG and G. W. Padua. Dept. of Food Science & Human Nutrition, Univ. of Illinois, Urbana-Champaign, 1304 W. Pennsylvania Ave., 382-D AESB, Urbana, IL 61801 Justification Extrusion of protein films for edible wrappings or packaging materials remains a challenge to researchers and product development technologists. Extrusion blowing has been used for decades to produce commodity plastic films such as LDPE plastic bags. The application of this process to protein film production would greatly improve their outlook as industrial polymeric materials. Zein, the alcohol-soluble protein of corn is recognized for its film-forming ability. It has been proposed for development into biodegradable and edible packaging materials. In this study we investigated the application of extrusion blowing to forming of zein films. Objectives Our objective was to determine optimal processing conditions of feed moisture content and barrel temperatures for extrusion blowing of zein films. Method Zein and oleic acid, used as plasticizer, were dissolved in ethanol-water and later precipitated in excess cold water. The precipitate was kneaded until a consistent resin was achieved. The resin was blown into cylindrical films with a single-screw extruder. Films were allowed to dry in ambient conditions. Results Extrudate moisture content, barrel temperatures, and air inlet speed were critical parameters in the extrusion blowing process. The combined effect of moisture and temperature determined the rheological properties of the extrudate. Experiments suggested that the optimal moisture content for extrudates was 15%, temperatures at the four extruder barrel zones were 25, 25, 35 and 45 ºC, respectively, with the last one being the condition of the blowing head. Blown films showed reasonable tensile properties, with tensile strength, elongation-at-break, and Young’s modulus of 3.2 MPa, 90%, and 93MPa, respectively. Significance Zein films were formed by extrusion blowing in the laboratory. These experiments demonstrated the feasibility of extrusion blowing for forming of protein films, paving the way for scaling-up development. We believe this processes could be also applicable to other kinds of protein films.
Session 27, Food Packaging: General
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