Mechanical and Water Barrier Properties of Zein-Corn Starch Composite Films as Affected by Gallic Acid Treatment

The effect of gallic acid treatment on mechanical and water barrier properties in zein and zein-corn starch composite films was investigated. Four concentrations of corn starch (5 %, 10 %, 15 %, 20 %) were used in composite films making a final solid concentration of 6% (w/v) in the film forming solution. One composite film containing 10% corn starch was also prepared in absence of gallic acid for comparison purpose. Gallic acid treatment improved tensile strength (TS) and water vapor permeability (WVP) while solubility was increased in control zein films. On the other hand, gallic acid treatment significantly (p < 0.05) reduced TS and increased WVP in zein-corn starch composite films. Interestingly, mechanical and water barrier properties of composite films prepared in absence of gallic acid were comparatively better than gallic acid treated composite films. These findings provided useful insights in how each individual hydrocolloid in the composite film was differently affected by gallic acid treatment.