Title: COMPOSITION FACTORS AFFECTING THE WATER VAPOR PERMEABILITY AND TENSILE PROPERTIES OF HYDROPHILIC ZEIN FILMS
Submitted to: Journal of Agricultural and Food Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: February 20, 1997
Publication Date: N/A
Full Text Available
Interpretive Summary: Most films used for packaging materials, protect water-sensitive foods and materials. Hence, it is important for such wrappings to be effective barriers against water vapor loss. Zein is an alcohol soluble protein extracted from corn. The most interesting properties of zein as an industrial protein is its ability to form tough films and coatings which resist water vapor penetration. The objective of this work was to study the compositional factors affecting the mechanical and water penetrating properties of zein films. Zein films are generally too brittle for most commercial applications. A plasticizer such as glycerol must be added to give the zein film a flexible texture. Zein films, containing a blend of glycerol and poly (prolpylene glycol) had an elongation almost fifty times greater than with glycerol alone. Zein films crosslinked with 20% polymeric starch showed excellent ability to prevent water loss. Such information will allow preparation of biopolymer films and coatings with desired strength and water vapor barrier properties to extend the shelf life of foods and other water-sensitive materials.
Transparent unplasticized zein films were prepared in aqueous ethanol or acetone. Tensile properties indicated that films prepared in acetone were stronger but less flexible than those prepared in ethanol. Both types of films, however, were too brittle for most applications. Films containing a glycerol:poly (propylene glycol) ratio of 1:3 exhibited elongation values almost fifty times greater than glycerol-plasticized films. Incorporation of crosslinking agents into zein films resulted in approximately a 2-3 fold increase in tensile strength values. Water vapor barrier properties were best for unplasticized zein films crosslinked with 20% polymeric dialdehyde starch. Incorporation of plasticizer into zein films resulted in an almost doubling in water vapor permeability values.