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Compression-Molded Whey Protein Film Properties
By,
Rungsinee Sothornvit1,
Carl W. Olsen2, Tara H. McHugh2, and John M. Krochta3
(1) Dept. of Food
Engineering, Kasetsart University, Thailand (2)
USDA, ARS, Western Regional Research Center, Albany, CA 94710 (3) Dept. of Food
Science & Technology, Univ. of California, Davis, CA 95616
The compression molding technique is a novel fast method to form whey protein isolate (WPI) film compared to the traditional solvent casting technique. Our objective was to determinate the effect of compression molding conditions (temperature and pressure) and glycerol content on film water vapor permeability (WVP) and mechanical properties.
WPI powder and 30, 40 or 50% (w/w) glycerol content (Gly) were thoroughly mixed. Films were formed by pressing WPI-Gly mixture at a temperature in the range 104-140 oC and pressure in the range 0.81-2.25 MPa for 2 min in a Carver Press. The Modified Cup Method and an Instron machine were used to determine film WVP and mechanical properties, respectively.
WPI-Gly films had WVP similar to films from solvent casting. Molding temperature and pressure did not significantly affect film elastic modulus (EM), tensile strength (TS) and % elongation (% E) (p>0.05). Increasing the Gly content of compression molded films decreased EM, similar to solvent cast WPI films. Compression molded WPI film TS and % E were greater than values from solvent cast films with same amount of Gly.
The compression molding method consumes less time for film formation and produces films with properties similar to solvent cast films. These results indicate the possibility of forming pouches for milk powders and other dry foods and ingredients by the extrusion process.
For more information on Dr. Krochta’s work and the Food Science and Technology Department at UC Davis, please visit Dr. Krochta's Web site - http://foodscience.ucdavis.edu/fst/faculty/KrochtaWeb/index.htm.