Effect of glycerol concentration on WPI-okra blended edible films

Abstract

Edible films were prepared by incorporating different levels of glycerol (0,5 % 1% and 2% w/w in the film forming solution) into whey protein isolate (WPI) - okra blend films. The effect of different concentrations of glycerol on water vapor permeability (WVP), moisture uptake, tensile properties (tensile strength and elongation at break) and microstructure were determined. Different glycerol levels did not exhibit a significant effect on WVP and tensile properties. However, by increment of glycerol content and %RH, there was a significant increment in moisture uptake. A small decrease of maximum tensile strength (σ max) accompanied with a modest increase in elongation at break (%EB) was observed by increasing glycerol concentration. Yet, firstly an anti-plasticizing effect of glycerol at low concentration was observed by increment of glycerol content, nevertheless this phenomena was probably influenced also by okra that was not purified prior to use.