The Adhesion And Rheological Properties Of Modified Zein

Large quantities of by-products are produced in corn starch processing plants, such as corn gluten meal, which accounts for 5% to 6% when isolated from the by-products. The protein content of corn gluten meal is about 60%. Zein is the main protein in corn gluten meal. Due to the lack of lysine, tryptophan, and other essential amino acids, the nutrition value of zein is low. Other problems such as color and odor, also limit its direct application. Lots of new bio-materials based on zein are developed, such as zein films. But the physical and mechanical properties are relatively poor compared with traditional petroleum-based products. Untreated zein film materials are brittle, and their performance is affected by environmental conditions, such as temperature and humidity. Therefore, it is urgent to develop effective ways for the utilization of zein. The purposes of this study are to improve the adhesion propoerteis of zein, characterize the rheological properties, provide a theoretical basis for molding processes of zein composites, and to explore its applications. This research showed important research value and application significance for conversion of agricultural by-products such as zein to bio-based materials and petroleum alternative products with high added value. The main research contents and results were summarized as the following.(1) The adhesion properties of modified zeinThe adhesion properties of chemically modified (glycerol, methylene chloride, and oleic acid) and radiation-modified zein were investigated, through measuring the physical and mechanical properties of zein-bamboo composites. With the concentration of chemical modification reagents increase, the adhesion property first increased, and then decreased. With 10% of glycerol concentration, 30% of methylene chloride concentration, 9% of oleic acid concentration, optimum adhesion properties of modified zein were achieved. With the radiation dose increase, the adhesion property of zein solution first increased, and then decreased. With 10KGy of radiation dose, the adhesion properties reached maximum. Based on quadratic orthogonal experimental design, the relationships between the radiation dose, zein solution concentration and adhesion property were analyzed, and the corresponding regression equations were established. Compared with other methods employed, 10% glycerol-modified zein showed the best adhesion properties.(2) The rheological properties of modified zeinThe effects of different modification methods (chemical modification and irradiation modification), temperature, and shear rate on rheological properties of modified zein were investigated. The zein solutions with chemical modification, such as glycerol, methylene chloride and oleic acid, or powder irradiation, showed pseudoplastic fluid characteristic, with shear thinning phenomenon. With the shear rate increase, the viscosity of solution reduced, and reached a plateau when the shear rate was close to 100s^-1. As the glycerol content and oleic acid content increase, the viscosity of solution increased. As the methylene chloride content increase the viscosity of solution decreased. As the radiation dose increase, the viscosity of solution first increased, and then decreased. In the experimental temperature range, as the temperature increase, the viscosity of methylene chloride modified solution reduced, and the viscosity of other methods modified solution first decreased and then increased. Through quadratic orthogonal experimental design, the relationships between the radiation dose, zein solution concentration and the viscosity were analyzed, and the corresponding regression equations were established. In the investigaed range, when radiation dose is constant, with the zein concentration increase, the viscosity increased; when zein concentration is constant, with the radiation dose increase,the viscosity almost did not change.