Effect of plasticizing sugars on rheological and thermal properties of zein resins and mechanical properties of zein films

Zein is the most important protein in corn. Zein has good film forming properties. One of the film forming methods is production of zein resin and then thermomolding by hot press. Pure zein film is very brittle. Plasticizers can improve mechanical and film making properties of zein. In this research, sugars (fructose, galactose and glucose) were used as plasticizers and rheological properties of zein resin were studied by dynamic oscillatory tests for determination of plasticization effectiveness. Effect of plasticizers on thermal properties of resins was investigated by DSC at −100 to 150 °C. No crystallization and melting peaks related to zein and plasticizers were observed. As well as there was not significant difference at glass transition temperature between zein resins containing various sugars. Zein films were prepared from zein resins by rolling and hot press and then mechanical properties of films were measured. Films containing galactose had better tensile properties than other films and showed higher tensile strength, strain at break, and Young modulus than films containing fructose and glucose.