WATER-VAPOR BARRIER PROPERTIES OF ZEIN FILMS PLASTICIZED WITH OLEIC-ACID

Water sorption, water vapor permeability, and tensile properties were evaluated for zein films plasticized with oleic acid. The effect of re lative humidity on water vapor permeability and tensile properties of films was investigated. Samples were produced by two different methods : casting from a zein solution and stretching from a zein-fatty acid r esin. Films were also coated with linseed oil. Results indicated that preparation method affected water sorption and permeability of zein fi lms. Resin films showed lower water sorption than cast films, especial ly at high A, values. Water vapor permeability was also lower for resi n films. Coating with linseed oil further improved water vapor barrier ability of resin films. Permeability was affected by environmental re lative humidity; higher relative humidity resulted in increased permea bility. Environmental relative humidity also affected tensile properti es of resin films. Toughness and elongation were improved when relativ e humidity increased from 50 to 85% rh. Tensile strength showed a maxi mum at 75% rh. Coating improved elongation and toughness of films. Max imum elongation and toughness were observed for coated samples at 85% rh. Zein resin films showed good tensile and water barrier properties that were maintained through environmental humidity levels from 50 to 98% rh.