Properties of zein films coated with drying oils.
Zein films prepared by resin were coated with either flax oil or tung oil and cured by UV- or gamma-radiation. Coated zein films were then evaluated for tensile and water barrier properties. Film microstructure was examined by transmitted light microscope. Tensile strength, elongation, and toughness of oil-coated samples increased substantially with respect to uncoated films. Flax oil coated samples showed an increase in elongation of 300%. It was suggested that oil coatings fill in pinholes and cracks existing in zein films, affecting their mechanical properties. Water vapor permeability also decreased statistically for coated film (except for tung oil coated-UV treated films), suggesting water vapor transfer was controlled by film hydrophobicity and microstructure. Moreover, the liquid water transmission rate of coated films was at least 10 times slower than for control films. Examination of film microstructure revealed that flax oil coatings had uniform coverage and smooth finish, which explained their high elongation, low water vapor permeability. Tung oil coatings cured under UV light showed patterns of intertwined dark and light regions, which may be caused by cross-linking and drying at different times. The oriented structures were found when tung oil coatings were cured by gamma-radiation.
Wang
Qin
Q
Department of Food Science and Human Nutrition, University of Illinois, 382/D AESB, 1304 West Pennsylvania Avenue, Urbana, Illinois 61801, USA.
Padua
Graciela W
GW
D055598:Chemical Phenomena; D002627:Chemistry, Physical; D018857:Food Packaging / Q000295:instrumentation*; D008043:Linseed Oil / Q000737:chemistry; D010539:Permeability; D010938:Plant Oils / Q000737:chemistry*; D013718:Tensile Strength; D014867:Water; D015028:Zein / Q000737:chemistry*
D010938:Plant Oils; D014867:Water; C009612:tung oil; D008043:Linseed Oil; D015028:Zein