Preparation And Properties Of Chitosan/Gelatin Composite Films

Chitosan is a natural polymer polysaccharide produced by the deacetylation ofchitin. It has good film-forming and biodegradable properties, and is widely used infood, pharmaceutical and chemical industry and so on. Gelatin, is a kind ofpolypeptide mixture extracted from animal skin, bones and other knot hoof tissues ofcollagen-rich organization. It’s polymer peptide mixture upon degradation of purified,with full of nutrient, rich sources and excellent film-forming properties. In this article,chitosan and gelatin were selected as major film-forming components, then glycerolwas added as plasticizer, and chitosan/gelatin composite films were prepared viasolution blending. At first, tensile strength and elongation at break were selected asindicators for single factors experiment, and the response the surface method tooptimize the formula of film was used by tensile strength for indicators. Then the lighttransmittance, water solubility and the swelling ratio were determined on differentgelatin contents of composite films. The relationship between microstructure andproperties was known by the way of the fourier transform infraredspectroscopy(FTIR), X ray diffraction analysis (XRD) and the scan electricmicroscope (SEM). The thermal stability and the degradation kinetics of compositefilm were systematically studied by TG. Finally, the resulted composite membraneswere applied as seasoning packet materials for instant noodles, and the watersolubility, oxygen permeability and transmission rate of water vapour were performedto evaluate the properties of chitosan/gelatin composite films. Specific contents andresults are as follows:(1) Preparation and process optimization of chitosan/gelatin composite films:The influences of glycerol volume, molecular weight of chitosan, gel strength ofgelatin and ratio of chitosan/gelatin on the tensile strength and elongation at break ofchitosan/gelatin composite films were investigated. Based on molecular weight ofchitosan, gel strength of gelatin and ratio of chitosan/gelatin, thereafter, optimizationof the preparation of chitosan/gelatin composite films was calculated via responsesurface method, and the optimal technological condition was as followed: weight ofchitosan400000, freezing strength of gelatin200Bloom and ratio of chitosan/gelatin 15%. At this condition, the stretch strength of chitosan/gelatin composite filmsreached (35.76±0.97)MPa.(2) Characterization of composite membrane: Transmittance, water-dispersibility,the swollen rate, transform infrared spectrum (FTIR), X-ray diffraction (XRD) andscanning electron microscope (SEM) were carried to reveal the properties andmicrostructure of chitosan/gelatin composite film. The results demonstrate thatswollen rate, transmittance, and water-dispersibility increase with the growingaddition of gelation. FTIR and XRD results indicates that there are strong hydrogenbond interactions between chitosan and gelatin, which destroy the crystal structure.When the ratio of15%chitosan/gelatin used, high quality compatibility wasachieved in the resulted composite film.(3) Thermal degradation study of chitosan/gelatin composite films: The thermalstability and degradation kinetics of composite films were systematically investigatedby TG. Under the different heating rate conditions, the results indicate that the thermaldegradation of composite films in the nitrogen is a two-steps reaction. Thedegradation temperature and Rpof DTA increase with the elevating heating rate(B).Cpand Cfare the degradation rates, and they are not affected by B. The activationenergy (E) and frequency factor (A) of the thermal degradation of composite filmschange with a trend of increase first, then decrease during the three reaction processes.(4) Applications of chitosan/gelatin films: When the ratio of gelatin is90%incomposite film, the edible composite film for the seasoning packet of instant noodlesis with the property of good water solubility, better oxygen barrier property and asmaller rate of water vapour transmission. It can basically meet the requirement ofcondiment packages in instant noodle.