Thermal Properties, Heat Sealability and Seal Attributes of Whey Protein Isolate/ Lipid Emulsion Edible Films

From 5% w/v whey protein isolate (WPI), whey protein/lipid emulsion edible films were produced that were sorbitol‐ or glycerol‐plasticized, containing butterfat (0.2% w/v) or candelilla wax (0.8% w/v). Thermal properties of the films determined by Differential Scanning Calorimetry (DSC) showed onset temperatures (To) of 126 to 127 °C for sorbitol‐ and 108 to 122 °C for glycerol‐plasticized films. To values were used as the basis for heat sealing temperatures. Temperature (110, 120, 130 °C), pressure (296,445 kPa), and dwell time (1,3 s) affected seal strength. Optimum heat sealing temperature was 130 °C for sorbitol‐ and 110 °C for glycerol‐plasticized films. All films were heat sealable with an impulse heat‐sealer. Electron Spectroscopy for Chemical Analysis (ESCA) of the surfaces of both sealed and unsealed films showed increase in hydrogen and covalent bonds involving C‐O‐H and N‐C, which may be the main forces responsible for the sealed joint formation of the films.