Research On Preparation And Gel Strength Of Gelatin From Fish Scale

In recent years, the breeding of Chinese freshwater fish presents a good momentum of development, thus yield increases year by year. Especially after 《The planning of Poyang lake ecological economic zone》 being listed as the national development strategy, freshwater fish industry has been further development. According to the statistics, the annual output of freshwater fish was 22.256 million tons in 2010 year, increasing 63.84% than 2000 year. However, the waste which is produced in the production process has caused great environmental pollution. The scale is one of the main wastes in the processing of freshwater fish. It contains rich collagen and is a good source of gelatin. The gelatin from fish scale has many advantages, such as high safety performance, wide applicable people, and so on. Thus gelatin from fish scale is expected to take place of the mammal gelatin. But at present, the fish scale is mostly abandoned, not only causing the pollution of the environment, but also seriously wasting the available resources.According to the above conditions, then taking the aim of transforming the waste into the treasure and being sustainable development, this paper took the waste-fish scale for raw material. Through the tissue mashing machine processing, hydrochloric acid decalcification and hot water preparation, gelatin from fish scale was obtained. Compared with the pigskin gelatin and the cowskin gelatin, the properties of gelatin from fish scale were research. This lay a foundation for the application of gelatin from fish scale. Basing the theory of ammonium sulfate precipitating protein step by step, five kinds of gelatin ingredients from fish scale were preparated. Gel strength and microstructure of gelatin ingredients from fish scale was researched by using some modern instruments, such as SDS-PAGE, nanometer laser particle size analyzer, scanning electron microscopy. The correlation between gel strength and microstructure was established, thus it could give a foundation for further research on gel property of gelatin from fish scale.Based on these ideas, this paper carried out a series of studies, the results were as follows: 1、The hydrochloric acid decalcification process:Through researching the effect of hydrochloric acid concentration, solid-liquid ratio and time on calcium ion concentration and hydroxyproline dissolving amounts in decalcifying solution, the best process of decalcification for the fish scale was determined. That was hydrochloric acid concentration 0.5mol/L, solid-liquid ratio 1:25, decalcifying time 1h.2、The comparative study on the fish scale physical index and the structure before and after decalcification:After using hydrochloric acid to soak decalcification for the fish scales, the ash of the fish scale dropped from 24.110% to 0.305%, and the protein content increased from 57.779% to 80.862%. So not only the production efficiency of the gelatin was improved, but also the purification process of late product was reduced. Before the decalcification, the surface offish scale was white and had a clear scale grain. The gelatin from the material was white. After the decalcification, the fish scale became a transparent shape, also thickness reduced significantly. And the gelatin from the material after decalcification was colorless. Through the observation of biological microscope amplifying 40 and 100 times, we could find that the surface of fish scale presented the rough stripe before the decalcification and the surface of fish scale after the decalcification presented the clear mesh structure.3> the gelatin preparation process by water method:In case of heating and mixing, the effect of solid-liquid ratio, pH, temperature, time on rate and ge strength of gelatin from fish scale was researched. Then the best process was obtained. That was solid-liquid ratio 1:15, pH 5.5, water bath temperature 80℃, heating time 2h. In this case, the rate of gelatin from fish scale was 55.782%, and gel strength was 571g.4、The research of the related properties for gelatin from fish scale:The gel strength, emulsification and emulsion stability, foaming ability and foaming stability, water absorption and water retention were researched among fish scale gelatin, pigskin gelatin and cowskin gelatin. When the concentration was 6.67%(w/v) and the temperature was 4℃, the gel strength offish scale gelatin was higher than two others. The emulsification and emulsion stability of fish scale gelatin were worse than two others, so it needed be further improved. The foaming ability of fish scale gelatin was better than two others, foaming stability was nearly the same with the cowskin gelatin, but was lower than the pigskin gelatin. The water absorption of the scales was obviously superior to two others. The fish scale gelatin losing water in short-term was fast, however its water retention was almost the same with two others when it was in a stabile state.5、The comparative study on gel strength of gelatin ingredients from fish scale: Basing different ammonium sulfate saturation, five kinds of gelatin ingredients from fish scale were preparated, then gel strength of those samples was researched. The gel strength descending order was A ingredient (precipitated by ammonium sulfate in saturation20%), B ingredient (precipitated by ammonium sulfate in saturation25%), C ingredient (precipitated by ammonium sulfate in saturation30%), D ingredient (precipitated by ammonium sulfate in saturation35%), E ingredient (precipitated by ammonium sulfate in saturation40%). The gel strength values of gelatin ingredients were different. It meant that separate effect by ammonium sulfate salting was good, so it could be usd to preparate the fish scale gelatin of high gel strength.6^ The microstructure study of gelatin ingredients from fish scale:Using SDS-PAGE, scanning electron microscopy, infrared spectroscopy and other modern analytical techniques, the correlation between gel strength and microstructure was researched. The results showed that with ammonium sulfate saturation increasing, gel strength of preparated ingredients became lower, then relative molecular mass, average particle diameter, particle concentration extent, hydrogen bonds, three super-helx structure and single-stranded left-handed-helix structure gradually less. However the content of filamentous materials became more.