The Mechanism Of Modori In Fish Myofibril Protein

With the aquiculture and poultry development of freshwater fish many techniques are required to speed the production of fish meat. But in the surimi production, when cooked from 50 to 70℃,the product always gets a lower strength and water-holding capacity ,it is called modori (thermal gel degradation) .So the objective of this paper is to study the mechanism of modori in surimi production. It contains the extraction of myofibril-bond serine proteinase and its effect on biochemical characteristics of actmyosin, and the inhibition of the food grade additives to thermal gel degradation as well. The data and result are listed as below:The average content of protein, lipid and moisture of carp muscle were 18.40%, 2.99%, and 76.39%. The proper concentration of actmyosin to investigate ATPase activity was 3-5mg/mLWhen the pH were between 6.0 and 7.0 and temperature below 40℃,the ATPase activity of carp actmyosin was highst.The total-SH of actmyosin incresed severely and the protein began to denature when in 50℃ above 60 minutes.The optimum temperature and pH of myofibril-bound serine proteinase were 55℃ and 8.0 separately. MBSP was alkaline proteinase. With the increasing of the concentration of NaCI the activity of MBSP decreased. From SDS-PAGE of myofibril hydrolyzed with different concentration of MBSP we can see that with increasing of the concentration ,the myosin heavy chain was denatured gradualy.The apparent hydrolyzatin was happened at 55℃.The ATPase activity of actmyosin was investigated with MBSP and the maximumwas in 25 ℃. MBSP could hydrolyze the fish meat gel protein at 37℃,and the degradation increased linely with time going till 55癈.NaCI had some ihibition towards modori. Folding test with MBSP showed that at 55 癈 reached the minimum folding ratio and the water-holding capacity was only 74.09% .When studying the food grade additives in the fish meat producing we found that 4%potato starch , 1 %corn starch , 4%wheat starch, 1 % xanthan gum and 5%egg white could inhibit the modori to some extent. When fish meat was heated at 37℃ for 60 minutes and then heated to 90℃ with inhibitors the water-holding capacity could reach 94.36%, When fish meat was heated at 55 ℃ for 60 minutes and then heat to 90℃ with inhibitors the water-holding capacity could only reach 86.42%.