Effect Of Transglutaminase On Gel Properties Of Freshwater Fishes

In this study which focuced on Silver Carp, Bighead, Grass Carp and Crucian Carp, meat-obtain ratio, protein and amino acid composition were assayed; effects of transglutaminase(TGase) on surimi gel properties were explored; the reaction condition of TGase was optimized. Regression equation of the reaction conditions and lysine ratio in actomyosin vs gel strength was obtained. The main results summarized as follows:1. Meat-obtain ratios are considerable different because of the size difference of 4 kinds of freshwater fish, Grass Crap highest, which was 34.79%, Silver Carp and Bighead 24.6%, Crucian 15.56%. The composition of those fishes studied had little difference and the contents of the crude protein and lipid were about 18% and 1.6-2.0%, respectively. The soluble protein contents accounted for over 80% of the crude protein. But protein and amino acid composition of them had significant difference.2. Protein composition of suimi and surimi-based products changed obviously during manufacturing. After washing, the content of water soluble protein was decreased while salt soluble protein increased. During stiring, setting and heating, the content of insoluble protein was raised. The gel strength of suimi-based products of Grass Carp was 2643.60g*mm, Silver Carp 2574.1 lg*mm, Bighead 2234.50g*mm and Crucian Carp 1951.31g*mm, all of which were lower than the second standard of frozen surimi quality of Japan. Process of surimi should be adjusted when using Silver Carp and Grass Carp as material.3. The reaction conditions of TGase were optimized. Surimi-based products gel strength was biggest under such conditions as 8-10U/g enzyme dosage, setting 1.5-2hr at 42℃ with natural pH value. By adding TGase, the gel strength of suimi-based products of Grass Carp was 12643.6g*mm which was 4.78 times compared with un-adding transglutaminas, while 5345.47g*mm and 2.08 times of Silver Carp, 7676.86g*mm, 3.44 times of Bighead and 7294.8 g*mm , 3.73 times of Crucian Carp.4. Effect Factors on gel strength such as setting time, TGase dosage, setting temperature, salt soluble protein contents, glutamine and lysine contents in actomyosin etc, were analyzed. TGase and its reaction conditions influenced the gel strength significantly; contents of the salt soluble protein and lysine have positive relation with gel strength. The relation equation described as following:S = -23216 +311 .757 T + 1770 .2931 + 1047 .669 c + 292 .443tIn the equation, S was gel strength(gxmm), c the concentration of TGase(U/g protein), T the reaction temperature(℃), t the reaction time(hr), L the content of lysine in actomyosin(%). Gel strength of surimi-based product could be controlled by every factors in this equation.