Isolation And Characterization Of Collagen From Skin Of Channel Catfish And Spotted Mackerel

Aquatic resources are rich in both China and Japan; many of them have been utilized for machining processing. A huge amount of fish tissues is discarded. However, abundant collagen contained in fisheries waste has varied application areas, including food, pharmaceutical, cosmetic, biomedical materials, leather imaging industry and research purposes. Moreover, bovine spongiform encephalopathy and transmissible spongiform encephalopathy have caused security issues about the collagen from mammals. Thus, fish tissues become the promising collagen source. It is also known as a filamentous protein fiber which can keep skin elasticity, existing in the human skin, bones, teeth, tendons and other parts for bonding connective tissue. Collagen is also existed in fish bones and connective tissues, primarily in the dermis, bone, tendon and fish scale. Extraction of collagen from fish skin can facilitate the value-added fish products processing, resulting in more economic benefits to promote the rapid development of fisheries. Internationally, most of collagen extraction is obtained from marine fish, while how to make full use of the abundant domestic freshwater fish resources is still a major issue for researchers.However, limited research has been conducted to compare the differences between the collagen extracted from freshwater fish skin and marine fish skin. The output of channel catfish in China is about 200,000 tons annually and the output of mackerel in Japan is around 400,000 tons. The living condition of freshwater fish is confined in a temperature range from 0 oC to 40 oC. Meanwhile, marine fish which is living in wide space can migrate to the area with suitable temperature. Therefore, the paper chooses channel catfish and spotted mackerel as materials to study about the isolation and characterization of collagen from skin of those two fishes. The results as following:1. This study in Chapter 3 has applied model to optimize the condition for hot water extraction of collagen from channel catfish skin. The result of variance analysis indicated the goodness of fit index is fairly good. The optimum extraction condition was at extraction temperature of 100 oC, p H 6, material/water ratio of 1:10 and collagen yield reached 17.59%. Response surface methodology was effective to optimize the collagen yield and had a reference value to develop large-scale extraction of collagen. Compared with other methods hot water of extraction is low-cost and simple with high value-added. The study provided a theoretical foundation of large-scale extraction of collagen. However, throngh combination with enzymatic and acid extraction method can further optimize collagen yield to maximize efficiency.2. In Chapter 4 the yield of collagen and efficiency of extraction were improved by the adjustment on the frequency of solution change and control of solution p H. In the pre-treatment, the fish skin sample was cut into small pieces possibly to improve the efficiency of soaking. In the extraction step, before salting out of collagen the p H of solution was adjusted to neutral by adding Tris to reduce solubility of collagen. The yield of collagen reached 22.79% of wet weight by modified method and the extraction duration was shortened to 7 day.3. In Chapter 5&6, in the scan of triple-helical structure of collagen, the CD curves showed a maximun at 220 nm and extracted samples were comfired by the characteristic of collagen. The thermal stabilities of collagen from two sources were different. The denaturation temperature of channel catfish was 36.5 oC while the mackerel was 30.5 oC. When the digestion temperature was 35 oC, the collagen from channel catfish and spotted mackerel can be completely digested. And the result of SDS-PAGE of digestion showed the peptide fragments were apparently different. Therefore, the thermal stability of collagen from channel catfish skin was more stable than mackerel.4. In Chapter 7, the denaturation temperature of summer ASC samples of channel catfish skin, channel catfish meat, spotted mackerel skin and spotted mackerel meat were 36.5 oC, 36.5 oC, 30.5 oC, 30.5 oC, while the denaturation temperature of winter ASC samples were 34 oC, 35 oC, 27.5 oC and 29.5 oC. Generally, channel catfish showed higher stability than spotted mackerel. Summer samples are more stable than winter samples. The denaturation temperature of collagen from meat were 1-2 oC higher than that of skin in winter, while the same in summer.