Preparing bilayer films by whey protein isolate-poly lactic acid and applying on the pork preservation

The bilayer films of whey protein (WPI) and poly (lactic acid) (PLA) were prepared by a simple solvent casting method in this study. The mechanical properties, water-soluble, light transmittance and haze of the films were measured. Moreover, WPI- PLA was applied to preserve the pork. The results showed that the adding of PLA could improve significantly the tensile strength of bilayer films (p<0.05) which could be increased from 2.08 MPa to 12.15 MPa. The films showed strong adhesion between layers without adding any extra component and displayed higher transparency. With the application of PLA, the water soluble, swelling index and elongation at break (EB) were reduced significantly (p<0.05) . Within 10 days storage at 4℃, p H, TBA and total bacterial count in pork packaged with this bilayer films were lower than control pork packaged with PE films significantly. The results suggested that the bilayer films could prolong the shelf life of pork effectively.