Study of mechanical properties, oxygen permeability and AFM topography of zein films plasticized by polyols

The use of plastic for packaging has grown extensively in recent years. In this context, biodegradable films can be a source of energy saving and an important issue for environmental protection. Zein protein (prolamin of corn) is one of the best biopolymers for edible film making and polyols are convenient plasticizers for biopolymers. Polyols (sorbitol, glycerol and mannitol) at three levels (0.5, 0.7 and 1g/g zein) were used as plasticizers and the tensile properties, oxygen permeability (OP) and AFM topography of zein films were studied. Films plasticized by sorbitol had a relatively higher ultimate tensile strength (UTS) than films containing glycerol and mannitol at low levels of plasticizers (0.25, 0.7g/g zein). There was no significant difference between the strain at break values (SB) of films plasticized by sorbitol and glycerol at low levels of plasticizers, while films plasticized by sorbitol had higher SB than the films containing glycerol and mannitol at a high level of plasticizer (1g/g zein). Pure zein films had low oxygen permeability (OP), and increasing the plasticizer level to 0.5g/g zein decreased OP values in films containing sorbitol and glycerol. Films containing sorbitol and mannitol had the lowest and highest OP values, respectively. AFM images were used to evaluate the surface morphology (qualitative parameter) and roughness (quantitative parameter) of zein films. Films plasticized by glycerol had smoother surfaces and a lower roughness parameter (Rq). No relationship between OP values and the roughness of the zein films was observed. Copyright © 2006 John Wiley & Sons, Ltd.

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