88C-23 |
Characterization of whey protein-based edible film properties in relation to film microstructure |
N. C. WRIGHT, Nutrition and Food Science, University of Vermont, 305 Terrill Hall, Burlington, VT 05446 and H. Chen. Edible film constituents and processes have significant effects on the film functional properties and microstructure. Invaluable information obtained from microstructual examination will inevitably reveal the film's molecular bonding. The objectives of this study were to determine the effects of applying vacuum to simple protein solutions and composite protein-beeswax emulsions made from whey protein isolate (WPI) and whey protein concentrate (WPC), and correlate the film microstructures to water vapor permeability (WVP), moisture content (MC) and tensile strength (TS). Simple whey protein solutions were prepared for 10% WPI (93%-protein) and 6.5% WPC (76.5%-protein). The protein solutions were denatured @ 90 oC for 30 min. Glycerol was added as a plasticizers @ 2:1 protein:plasticizers ratio. Upon cooling the first set of films were cast without vacuum. After 2, 4, and 8hrs of applied vacuum subsequent films were cast. Beeswax was melted in the heated protein solution @ 4:1 protein:beeswax ratio the mixture was homogenized in three 5 min intervals. Films were cast in the same manner as described above. For each film a total of seven microstructural views were obtained using Transmission Electron Microscopy (TEM) enface and cross-section, Scanning Electron Microscopy (SEM) enface, bottom, and cross-section, and Atomic Force Microscopy (AFM) 2D and 3D view of enface section. Vacuum treatment had no significant effect on WVP, MC, TS and microstructure. WPI-films with lower WVP, MC and TS correlated with microstructure images of lipid particles embedded within the protein matrix. The functional properties for WPC-BX films of high WVP, high MC, and very low TS correlates with microstructures depicting unusual high porosity within the structure. Microstructures that illustrated less porosity and dispersed beeswax throughout the protein matrix associated to films with low functional properties. Microscopy is a useful technique for analyzing whey protein-based edible film in correlation to the film functional properties.
Session 88C, Food Engineering: Physical and Chemical Properties
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