Submitted to: Journal of Food Engineering
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/1/2005
Publication Date: 1/19/2006
Citation: R. Sothornvit, C.W. Olsen, T.H. Mc Hugh, J.M. Krochta. February 2007. Tensile properties of compression-molded whey protein sheets: Determination of molding condition and glycerol-content effects and comparison with solution-cast films. Journal of Food Engineering. 78(3):855-860. Interpretive Summary: This research focused on developing new edible and biodegradable packaging materials to store foods and extend their shelf-life. These products offer environmental advantages over synthetic packaging materials. Whey protein was used as the main film forming ingredient. It is important to the dairy industry to find new uses for whey proteins. A new technology, called compression molding, was used to form whey protein films. Flexible films were produced and their strength and flexibility was tested. These films could be used to form pouches to store dry ingredients, as casings for sausages or vegetarian foods, or as films to cover leftovers.
Technical Abstract: The effects of glycerol content (GC), molding temperature and molding pressure on tensile properties of transparent compression-molded whey protein isolate (WPI) sheets were studied, and the properties were compared to those of films produced using the solution-casting method. Compression-molding temperature and pressure did not significantly affect sheet stiffness (elastic modulus, EM), strength (tensile strength, TS) or extension (% elongation, %E) (p>0.05). Increasing GC of compression-molded sheets decreased EM and TS, but had little effect on %E. The values of TS and %E of compression-molded WPI sheets with 40-50% glycerol (Gly) were greater than those of solution-cast WPI films with 45% Gly. The fact that transparent Gly-plasticized WPI sheets could be formed from Gly-WPI mixtures using compression molding demonstrates that such mixtures display flowability and fusion behavior under certain conditions. These results indicate the possibility that Gly-WPI can be extruded into films for formation of edible or biodegradable pouches for dry food ingredients.