Study On The Preparation And Properties Of Protein And Polysaccharide Composite Films

Edible composite film is a kind of biodegradable film that is made by two or more natural edible film-forming materials, but poor mechanical and barrier properties, to some extent, limit its packaging application. To meet packaging materials requirements of foods such as milk powder and instant coffee, The mechanical properties,water vapor permeability and oxygen barrier of Sodium Alginate-Based Composite Films were studied by adding plasticizers and other supporting materials.The conditions of preparing the edible films were optimized as following: sodium alginate (ALG-Na): sodium carboxymethylcellulose (CMC-Na ): gelatin (GLE) was 3:1:0.5. The composite film had a good tensile strength ,a nice breaking elongation .All the composite films showed a wonderful transparency and solubility.The Properties of composite films were studied by adding glycerol, selecting drying temperature, microwave treatment and Homogenization treatment. The results indicated:Glycerol could increase the elongation rate of composite films. The mechanical strength were influenced by drying temperature. Microwave treatment could improve the mechanical properties. Homogenization treatment could improve the Optical transmittance obviously.The Water Vapor Permeability of optimized composite films with various hydrophobic materials were determined. The results suggested that the composite film with sucrose fatty acid ester had good water vapor permeability and gloss because of improving the density and compact. An addition of as little as 0.5%of olive oil in the mixture induced significant improvement in gloss of composite films. However, it was not significant in water vapor permeability (WVP).Composite films have more effective oxygen barrier than plastic films and composite films with 0.2g/ml Whey Protein have the most effective oxygen barrier.The rheological properties of aqueous mixed solutions from sodium alginate ,sodium carboxymethylcellulose and gelatin were investigated at different shear rate and temperature. It is found that the mixed solutions behaved as non-Newtonian shear-thinning fluids . Viscosity and gelation temperature decreased by adding gelatin. Mechanical properties of films from sodium alginate ,sodium carboxymethylcellulose and gelatin were studied. Test results demonstrate composite films showed a low degree of orientation, high chains activity and a unitary structure. The differences of physical performance of composite films could also be interpreted by the structure of amorphous region reflected in dynamic elastic-viscous spectrum.Their structure and properties of films were studied by FT-IR,XRD, SEM, Optical transmittance .The results indicated there were some strong interaction and good compatibility in sodium alginate,sodium carboxymethylcellulose and gelatin. The physical and chemical properties of the blend films were obviously improved.The main influence factors of seal strength of sodium alginate /sodium carboxymethylcellulose/ gelatin composite films were studied. Adhesive concentration ,sealing temperature,sealing pressure were the main influence factors.Taking the seal strength as objective function, the orthogonal rotation experimental design methods based on single quadratic regession were used for investigation and established a quadratic regression model. The results indicated that the optimum preparation parameters were: adhesive concentration 23.50%, sealing pressure0.23MPa, sealing temperature 157.80℃and sealing time 1s.Under these optimal conditions,the seal strength was up to 26.027N/15mm.