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2006 IFT Poster Presentation (PDF)

Whey protein – hydroxypropyl methylcellulose blended film: mechanical, barrier, thermal and structural properties

L.A. PALLAS, J.M. Krochta, Dept of Food Science, Davis, The Univ. of California Davis, One Shields Ave., Davis, CA 95616

With potential to generate alternatives and improvements in packaging design, blending has much promise in edible films and coatings.  Blending has been employed to create new materials with improved mechanical properties by combining the advantages of individual components while diminishing or improving inferior properties. To assess the potential of a whey protein isolate (WPI)-hydroxypropyl methylcellulose (HPMC) blended edible film with glycerol (Gly), it is necessary to study the interaction between these components through blend analysis.  We hypothesize that the films will exhibit properties proportional to the amounts of each polymer and that blending HPMC with denatured WPI will produce films with properties different from blending HPMC with native WPI.  Solubility and thermal analysis are predicted to show domains of varying concentrations between the film components.

The main objectives were to develop WPI films incorporating HPMC as well as investigate film formation, mechanical properties, oxygen permeability (OP), thermal properties, and solubility of films blended in different combinations and at different conditions. 

WPI:Gly-HPMC films were analyzed using an Instron Universal Testing Machine for mechanical properties, an Oxtran 2/20 modular system for OP, and a Differential Scanning Calorimeter for thermal properties. Differences due to HPMC quantity and blend method were determined via SAS software.

While WPI:Gly or HPMC films were transparent, blended films were translucent, indicating aggregated domains in the latter films.  WPI:Gly-HPMC films became stiffer, stronger and less stretchable as the concentration of HPMC increased.  However, WPI:Gly-HPMC blended films up to a WPI-HPMC ratio of 1:3 maintained the same low OP of WPI:Gly films, significantly lower than the OP of HPMC films.  Crosslinking WPI after blending with HPMC did not produce mechanical properties different from crosslinking WPI before blending with HPMC, while solubility data indicated otherwise.

While adding HPMC to WPI:Gly films has a large effect on the rigidity and strength of the film polymeric network, results suggest HPMC has no effect on the product of the oxygen solubility and diffusivity in the network.