| The extraction method of channel catfish skin gelatin and tea polyphenol loaded nanoparticles was developed. The influence of tea polypheno loaded nanoparticles on gelatin film was evaluated. Furthermore, the release kinetics of tea polyphenol from composite films was investigated.Gelatin was extracted from channel catfish skin with a novel method and characterized. The skin was allowed to swell in acetic acid, and then was mashed with triturator, dissolved in dilte acid, precipitated by adding NaOH to obtained collagen fibers. Finnally, the collagen fibers were extracted for gelatin in the water of 45°C,pH7.0 within 6 hours. It was found that the yield of gelatin had exceeded 95%, the gelation temperature of gelatin solution and gelatin gel melting point were 19.6°C,25.2°C, respectively.Tea polyphenols nanoliposomes (TP-L) were prepared with by ethanol injection- sonication method. Higher encapsulating efficiency of 25 mg tea polyphenols was obtained with lecithin concentraction of 1.0 mg/mL, cholesterol to lecithin mass ratio of 1:5, Tween 80 and lipid to the molar ratio of 4:5, hydration temperature of 50°C, hydration time of 30 min and 50 mL of PBS (0.05 mol/L, pH7.0). The particles of nanoliposomes were about 120 nm and zeta potential was in the range of -10 and -20 mV. With the incorporation of TP-L, a kind of composite films (TP-L F) based on channel catfish skin gelatin was obtained. Due to the steric effects from TP-L and the formation of hydrogen between TP-L and gelatin molecules, the hydrogen bonds between the gelatin-gelatin stabilizing the network of gelatin film had been reduced, consequently, the properties of the composite film had been changed. With a respect, antioxidative activity of the film had been enhanced siginficantlly.Technical route of preparation for tea polyphenols loaded chitosan- sodium tripolyphosphate nanoparticles (TP-CTS-TPP) were confirmed. The optimum technical parameters with highest encapsulating efficiency were: chitosan concentraction of 2.0 mg/mL, pH5.5, TPP to chitosan mass ratio of 1:3, TP of 25 mg, time of 30 min. The resulted nanoparticels was about 300 nm and zeta potential was in the range of 40 and 50 mV. The composite gelatin film (TP-CTS-TPP F) incorporated TP-CTS-TPP was prepared and its antioxidative activity and properties were investigated. It showed, the incorporation of TP-CTS-TPP interfered with hydrogen forming between gelatin molecules, owing to the steric effects from TP-CTS-TPP and the formation of hydrogen including interaction of amino-group on chitosan with amino-group on gelatin and interaction of hydroxyl-group on chitosan with amino-group on gelatin. So, the properties of composite film were modified, but its antioxidative ability was improved to a large extent.Finally, the release kinetics of TP-L and TP-CTS-TPP in PBS, the release kinetics of TP-L and TP-CTS-TPP in gelatin films as well as the release kinetics of TP-L F and TP-CTS-TPP F in PBS were characterized. The first, the release kinetics of TP-L and TP-CTS-TPP in PBS fitted the first release kinetic model well; however, the cumulative release rate of TP-L was higher than that of TP-CTS-TPP. The second, the release kinetics of TP-L and TP-CTS-TPP in gelatin films also were consistent with the first release kinetic model; however, the release rate of TP-L and TP-CTS-TPP were lower than their in PBS. The third, the release characteristicas of TP from TP-L F and TP-CTS-TPP F in PBS were related to the swelling ability and dissolutions of the composite films. TP-L F corroded in PBS quickly, and TP was released from TP-L dispersed in PBS. At the first stage, the TP-CTS-TPP F in PBS happened to limited dissolution and to became hydrogel, TP released from TP-CTS-TPP fixed in hydrogel and then diffused from hydrogel to PBS through the channel formed by water in the course of swelling procdure.
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