WATER-VAPOR PERMEABILITY AND MECHANICAL-PROPERTIES OF GRAIN PROTEIN-BASED FILMS AS AFFECTED BY MIXTURES OF POLYETHYLENE-GLYCOL AND GLYCERINPLASTICIZERS

Grain protein-based films containing mixtures of glycerin and polyethy lene glycol (PEG) as plasticizers were prepared and evaluated for wate r vapor permeability (WVP), tensile strength (TS), and elongation (E). Changes in mechanical properties during storage were also studied. Th e PEG produced opposite trends in E of wheat gluten and corn-zein film s. The TS of wheat gluten films increased and E of the films decreased as the ratio of glycerin/PEG decreased. Corn-zein films containing on ly glycerin were very brittle (E of 4%), and E of the films improved t o 94% when the ratio of mL PEG/g protein was 0.39. The WVP of both fil ms decreased as the ratio of glycerin/PEG was decreased. Also, WVP of both films increased as the total amount of plasticizer added to the f ilms increased. Mixtures of glycerin and PEG as plasticizer are less f ugitive than glycerin alone in grain protein-based films and can reduc e the deterioration of mechanical properties during storage.