Preparation And Characterization Of Gelation And Chitosan Composite Films

With the faster pace of modern life, quality of supermarket food for people and the need of people for a longer shelf life greatly hastily increased.In the process of production, transportation and storage food is extremely vulnerable to the external environment, such as light, temperature, relative humidity, and other physical factors impact, but also to be threatened by microorganisms. With the concept of sustainable development, functional edible packaging materials become hot. This essay aims to take advantage of two commonly matrix gelatin and chitosan, respectively, to establish an antibacterial films and novel emulsified film,whose mechanical properties e, barrier properties, antibacterial properties, wetting properties we study. By means of the microscopic structure of film, we also study the impact of ingredients(antibacterial agent and Pickering emulsion) on microstructure and the relationship between microstructure and macroscopic properties.The main findings are as follows:(1)The water-soluble gelatin matrix,with the addition of organic lysozyme and inorganic nano-zinc oxide as two different antibacterial mechanism agent, shows better antibacterial effect on E. coli and Bacillus subtilis than the gelatin film with one of lysozyme and nano-zinc. That means there is synergistic anti-bacterial capacity in gelatin film lysozyme and nano-zinc oxide. Compared with the gelatin film with one of lysozyme and nano-zinc, the mechanical resistance of gelatin film with lysozyme and nano-zinc oxide decreases, but the ductility differs depending on different contents of nano-zinc oxide. the exist of two agent make the moisture and oxygen barrier properties of the films rarely decreasing.(2) Based on zein-chitosan particles stabilized Pickering emulsion, in order to be compatible with the particles, we pick up quick-gel gelatin as the film matrix. Via ultrasonic homogeneous dispersion in the film matrix, the average particle diameter of emulsion droplets drop from several tens μm to ones μm compare with the original and the transparent is lowered. corn oil which have a absorption peak at 280 nm make up the drawback of gelatin. The disparity of mechanical resistance is small when the content oil is less than 25%.But when the content is more than 25%, mechanical resistance rapidly decline and also the ductility. With increasing amount of oil, moisture content and swelling ratio decreased,but soluble solids content increased. Adding Pickering emulsion makes gelatin films better performanceof oxygen and moisture barrier performance, respectively, at content of 25%、10% for best.That mans this film based on the Pickering emulsion material has a good barrier properties.(3) Microstructure heterogeneity of emulsion films impaired their physical performances. Thiswork attempted to fabricate novel high-barrier chitosan(CH) emulsion films by manipulatingemulsion’s interface architecture via Pickering stabilization approach. Some selected physicalproperties, including tensile property, water vapor permeability(WVP), and oxygen permeability(OP) as well as the microstructure of the films were evaluated. Film-forming emulsions(FFEs) based on zein/chitosan colloid particles-stabilized Pickering emulsions(ZCCPEs) were extremely stable,evidenced by the similar droplets size and size distribution in the FFEs and film matrix, endowing the films with homogeneous distributions of lipid droplets over their 3D network matrix. Interestingly, emulsion films exhibited excellent oxygen-barrier efficiency, and the OP of the films was decreased by 1-4 orders of magnitude when compared with CH films. This phenomenon may be associated with the novel interfacial architecture of ZCCPEs as well as film microstructure morphology based on ordered assembles of CH matrix and ZCCPEs. A schematic diagram for the formation pathway of ZCCPEs-loaded CH emulsion films was proposed to establish structure-function relationships of the films. This study opens a promising pathway for producing emulsion films with excellent oxygen-barrier capability via Pickering stabilization principle.This study successfully constructed a synergistic antibacterial effect of gelatin and new zein-CH Pickering emulsion of gelatin / chitosan film with good barrier properties, protecting the packaged food from the external environment.