Preperation Of Novel Starch Films And Study On Their Structure And Performance

Starch is a natural polymer material with widespread source, lower price and renewable performance. The packaging films with starch as the main material can be prepared to replace the traditional food packaging film from petroleum products. Moreover, they are considered to be the most promising one of biodegradable packaging materials. However, due to poor mechanical properties and easy-to-aging, the application of starch based packaging films in the food industry is limited.The influence of the concentration of starch paste, the content of glycerol, the stirring rate and the drying temperature to the mechanical properties of starch based films were studied in the text. Moreover, the relationship between the set back performance of the different starches (potato starch, corn starch and pea starch) paste and the structure and properties of starches films was studied. A simple and rapid method of the material selection for films was gained.Guided by the relation between set back performance of material paste and the structure and properties of film, agar was selected as the enhanced agent to starch films in this text because of its stronger set back performance and its polysaccharide structure which was similar to starch. Proved by the experiments, agar had good compatibility to starch. The addition of agar inhibited the crystallization of amylose and delayed the aging of the starch films, increased the density and reduced water vapor permeation of the starch films, and raised tensile strength, elongation at break and thermal stability of the starch films.In order to increase the interface between starch and esterification agent, succinic anhydride was dissolved and dispersed on the surface of starches in this text. Esterafication took place by the green and highly efficient method of solid-state reaction. Take corn starch as example, by comparing the different degreees of substitution of products in different reaction conditions, response surface methodology was used to optimize reaction conditions. The best reaction conditions were: the water content was 12%, the reaction temperature was 100℃, and the reaction time was 4 h. At these conditions, the reaction efficiency was up to 68%. Potato, corn and pea starch succinates with different degrees of substitution were prepared to films. Proved by the experiments, esterafication inhibited the crystallization and slowed the aging of starch films, reduced the thermal stability of starch films, and improved the water absorption, the elongation at break and water vapor permeation of starch films.With a large number of aldehyde groups, dialdehyde starch could cross-link with starch chains. Therefore, dialdehyde starch was used as crosslinker in starch films in this text. Proved by the experiments, the addition of dialdehyde starch slowed the crystalline formation in starch films and delayed the films' aging, improved the morphology of the starch films, reduced the water absorption and water vapor permeation of the starch films, increased the tensile strength of the starch films, and improved the elongation at break of the starch films at certain content.