Thermal properties, heat sealability and seal attributes of whey protein isolate/lipid emulsion edible films
2001
Kim, S.J. | Ustunol, Z.
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 (T(o)) of 126 to 127 degrees C for sorbitol- and 108 to 122 degrees C for glycerol-plasticized films. T(o) values were used as the basis for heat sealing temperatures. Temperature (110, 120, 130 degrees C), pressure (296, 445 kPa), and dwell time (1, 3 s) affected seal strength. Optimum heat sealing temperature was 130 degrees C for sorbitol- and 110 degrees 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.
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