Studies On Texture And Bioactivity Of Shark Fin

Shark fin, which has many medical and nutritional functions, is one of precious seafood in China. In this paper, the shark caudal fin was chosen as the material and the following researches were carried out.Firstly, the basic composition and the changes of the texture of shark fin during processing were studied. The results were shown that the shark fin is composed of 54% water, 45% protein, 41.5% collagen (92% of total protein) and a little fat and ash. Shark fin had abundant of amino acids, especially the necessary amino acids which accounted for 20.5% of total amino acids. When boiled for different time, the structure of the shark fin changed greatly, gel strength, biggest strain, shear and rupture strength of shark fin were decreased with the boiling time. After boiled three hours, such changes became little. Combined with the sensory analysis and rheological results, 3 hours boiling was a practical treatment for a perfect texture of shark fin.Secondly, the antioxidation of shark fin collagen was studied. Denatured temperature of collagen was 66.7℃. The results of UV absorption wave showed that shark sting collagen was 230nm, shark skin collagen was 234nm. Type E ([α₁(E)]₃)of Sting collagen , type I of skin collagen, and typeâ…¡([α₁(â…¡)]₃) of cartilage collagen was demonstrated by SDS-PAGE. The antioxidation abilities of collagen proteinase hydrolysates were investigated and the results were shown as follows:1) Inhibition ability to superoxide radical. There is the highest inhibition ability to superoxide radical of hydrolysates from shark sting by Pepsin, the value of its IC₅₀ is 1.87mg/mL. Low temperature alkaline proteinase is suitable for the hydrolysis for shark skin collagen, and the IC₅₀ was 2.14 mg/mL.2) Inhibition ability to hydroxyl radical. The hydrolysate by low temperature alkaline proteinase has the highest inhibition to hydroxyl radical, and the hydrolysate by pepsin is the lowest. The IC₅₀ of shark sting was 0.67mg/mL, much bigger than that of shark skin(0.35mg/mL). Finally, the antioxidation of mucopolysaccharides extracted from shark fin rays and shark fin cartilage was studied. The mucopolysaccharides contents of hydrolysate were 18.18% and 36.49%, and the sulfuric acid contents were 11.79% and 1.25%. The molecular weights of mucopolysaccharides extracted from shark sting were 67.4kDa22.6kDa,5.2kDa,3.6kDa, while the molecular weights of mucopolysacch -arides extracted from shark cartilage were 60.4kDa,4.6kDa,3.1kDa. Shark fin rays were made of amino sugars and uronic acids, while shark fin cartilage was made of amino sugars, uronic acids and neural sugars.The IC₅₀ of mucopolysaccharides extracted from shark fin cartilage to remove hydroxyl radical was 0.267mg/mL, while it was 1.75 mg/mL to remove superoxide radical. Antioxidation of mucopolysaccharides extracted from shark sting was not as good as that extracted from shark cartilage.