Mechanical properties of whey protein isolate-based edible films as affected by meat processing conditions and optimization of these properties

This study was conducted to test the hypothesis that whey protein isolate (WPI)-based edible films could be used as sausage casings comparable to collagen casings. Heat cured (80°C, 24 h or 90°C, 12 h) WPI-based films containing glycerol and candelilla wax were treated under meat processing conditions; the effects of temperature, time and relative humidity on the tensile strength (TS) and percent elongation (%E) of the films were determined. Tensile strength of WPI-based films was lower while %E was similar to that of collagen films. To optimize the mechanical properties of the WPI-based films, different film forming solutions (5.8% or 6.4% w/v solids content), casting on different surfaces (anodized or non-anodized TeflonRTM), heat curing (90°C, 12 h) and compression molding (single- and double-stage; and varying temperature, pressure and time) were studied. Heat curing and compression molding increased TS and had no effect on %E. In a separate double-stage compression molding experiment, temperature, pressure and time conditions were optimized. No optimum combination of these conditions was obtained. Finally, seal strengths and surface chemistry (using electron spectroscopy for chemical analysis, ESCA) of unsealed and sealed uncured, heat cured and compression molded WPI-based films were studied. Uncured films had the highest seal strengths. Sealed, heat cured and compression molded films had a preponderance of C-O-H and C-O-C bonds, which were not detected in uncured films.