Formation conditions, water-vapor permeability, and solubility of compression-molded whey protein films

Films based on whey protein isolate (WPI) were formed using compression molding. Compression molded films could be formed using 30% to 50% moisture content or glycerol content WPI at 104 degreesC to 160 degreesC for 2 min. Films made from water-WPI mixtures were brittle and insoluble and had water-vapor permeability values independent of starting water-WPI mixture moisture content, molding temperature, or molding pressure. Gly-WPI films produced at 104 degreesC were flexible and partially soluble. Gly-WPI films produced at 140 degreesC were also flexible but nearly insoluble. Glycerol content and molding temperature and pressure had little effect on water-vapor permeability values of Gly-WPI films over the range of conditions studied.