EDIBLE BILAYER FILMS FROM ZEIN AND GRAIN-SORGHUM WAX OR CARNAUBA WAX

Tensile strength, elongation at break (E), water vapor permeability, a nd Hunter L, a, and b color values of single-layer zein films and bila yer zein/lipid films were determined. Zein films wc re cast from heate d (60 degrees C) aqueous ethanol solutions and were plasticized with g lycerin and polyethylene glycol. Bilayer films,were prepared by coatin g dried zein films with either medium-chain triglyceride (MCT) oil, la boratory-extracted sorghum wax (SW)/MCT oil, or commercially refined c arnauba wax (CW)/MCT oil. SW/oil or CW/oil weight ratio in the lipid l ayer of wax/MCT oil mixtures was 1:25.3, 1:11.5, or 1:7.4. Application of a lipid layer significantly decreased water vapor permeability of zein films from 9.07 to as low as 0.115 g(-1)mm/m(2)/h(-1)/k(-1)Pa. Me an tensile strength values of zein films (1.05 MPa) and zein/lipid fil ms (0.82 to 1.54 MPa) did not differ appreciably. The lipid coating pl asticized zein films as evidenced by greater E values for bilayer film s (153.1-167.9%) than single layer films (130.2%). The lipid layer sig nificantly reduced + b (less yellowness) and L (increased opacity) Hun ter color values of zein films. At 1:11.5 and 1:7.4 wax/oil ratios in the lipid layer; films with sorghum wax were more opaque (lower L valu es) and less yellow (lower + b values) than films with carnauba wan. S orghum and refined carnauba wax appeared equally effective in improvin g water vapor barrier properties of zein films. Use as an ingredient i n edible and/or biodegradable films and coatings can provide an outlet for sorghum wax.