Extraction Of Fish Scale Collagen And Preparation Of Collagen Sponge

In our country, the resources of fresh water fish are abundant. There are approximately 650,000 tons fish scales every year. Most fish scales are wasted except that a few are exported. The fish scale contains abundant collagen which may be used to prepare collagen sponge. However, little knowledge has been accumulated regarding processing technology of sponge from fish scale collagen. In this work, basic components of fresh water fish scale at different time, decalcifying process of fish scale, extraction of fish scale collagen and preparation of collagen sponge were investigated. It was anticipated to offer theoretical foundation for improving products with high additional value, such as collagen sponge.1. Basic components of fresh water fish scale (grass carp, silver carp, crucian carp and bream) were determined in the different time. The basic components depended on fish species. The protein content is approximately 52%～78%, the ash content is 10%～29%, the moisture content is 13%～20%, and the fat content is 1%～6%. Among the four kinds of fish scales, the protein content of silver carp scale is the highest followed by crucian carp and bream scale, whereas, protein content of grass scale is the lowest. The basic components of scale were not obviously correlated with time.2. The decalcifying process of fish scale was optimized. The type and concentration of acid, the temperature and time of processing, and the solid-liquid ratio significantly influenced decalcifying rate of fish scale. Decalcification rate reached 99.85% when 3% hydrochloric acid was used with 1:20 solid-liquid ratio at 15℃for 3h. Similar decalcification rate (99.72%) was obtained when 6% citric acid was used with 1:15 solid-liquid ratio at 15℃for 4 h.3. The extraction technology of scale collagen was studied. The temperature and time of extraction, pepsin dosage, and the solid-liquid ratio significantly influenced extraction rate of fish scale collagen. The optimal extraction technology of scale was that 0.5 mol/L acetic acid was used with 2000U/g _protein pepsin and 1:15 solid-liquid ratio at 15℃for 48 h. The collagen extraction rate reached 63.56% under the optimal condition, and was obviously higher than that without pepsin. The scale collagen was identified as type I collagen by ultraviolet spectrum, infrared spectrum, SDS-PAGE, and with comparison to small beef tendon type I collagen.4. Preparation technology of collagen sponge was studied. The collagen concentration and pH value significantly influenced water absorption and tension strength of scale collagen sponge. When collagen sponge was prepared from 0.5% scale collagen at pH6.0, it could obtain high water absorption capacity and tension strength. Under the processing condition, collagen sponge owned significantly higher water absorption capacity and tension strength than gelatin sponge. Addition of chitosan significantly enhanced water absorption capacity and the tension strength of collagen sponge. The ratio of collagen to chitosan, pH value and total concentration have remarkable influence on water absorption capacity and tension strength of sponge. The collagen/chitosan mixed sponge obtained the highest water absorption capacity (92) and tension strength (40 KPa) when the ratio of collagen to chitosan is 2:8 at pH6.0 with a total concentration of 0.6%.