Characterization of protein-coated polypropylene films as a novel composite structure for active food packaging application

Plasticized protein coatings on polypropylene (PP) film were prepared and examined for their optical and tensile properties as affected by protein and plasticizer types in order to exploit a novel composite film for food packaging applications. Composite structure of PP film coated with three kinds of proteins (soy protein isolate: SPI, whey protein isolate: WPI, corn zein: CZ) and various plasticizers (propylene glycol, glycerol, polyethylene glycol, sorbitol, sucrose) could be obtained by a simple casting method. High glossy surfaces were observed on the coated films with WPI and CZ, with the sucrose-plasticized WPI coating giving the highest gloss. Proteins as well as plasticizers exerted a noticeable effect on color of the coated films. WPI coated films also showed greater transparency and tensile strength than the other coated films. Nisin-incorporated WPI coatings on PP film exhibited significant bacterial growth inhibition against Lactobacillus plantarum. Results suggest that WPI coatings with a proper plasticizer possess excellent visual and mechanical characteristics and have great potential for application in active packaging systems.