Microstructure and characteristics of high-amylose corn starch−chitosan film as affected by composition

Edible films composed of high-amylose corn starch and chitosan were developed by casting method. The effects of the ratio of high-amylose corn starch to chitosan, concentration of glycerol and methyl cellulose on the oxygen and carbon dioxide permeation, water vapor transmission, tensile strength and percent elongation at break values of edible composite films were investigated. Film microstructure was characterized by scanning electron microscopy. The results showed that the increase of the ratio of chitosan and content of glycerol in the film forming suspensions both made the structure of films flexible, causing the decrease of tensile strength and increase of percent elongation of composite films, while showing poor water vapor barrier properties as the water vapor transmission values increased. The addition of methyl cellulose as to reinforce the structure of matrix improved the water vapor barrier properties of the edible films with the decrease of water vapor transmission from 1946 to 1668 g/(m²·24 h), as well as the mechanical properties were improved as expected, which could be attributed to the differentia of the interaction between methyl cellulose and other components in the film preparation as the concentration ranged from 2% (w/w) to 8% (w/w). Films with different compositions, resulting different microstructures, showed variance in barrier and mechanical properties.