Studies On Nutritional Components And Autolysis Of Myofibrillar Protein In Stomolophus Meleagris

Stomolophus meleagris is one of the main jellyfishes from the Yellow Sea.Stomolophus meleagris contains many kinds of active ingredients and is of great nutritional and medical value."Stomolophus meleagris Meal"has been proposed in Qingdao which attracted a large number of tourists. The"Stomolophus meleagris Meal"is mainly using different parts of large Stomolophus meleagris as raw materials and so a lot of special meals of characteristics come out , such as the fried oyster stew cabbage, sand and salt could take advantage of his melons on the fried oyster and so on. There are rarely researches about the application of Stomolophus meleagris resource, and the characteristic catering of Qingdao promotes the use of Stomolophus meleagris. The proper time for hunting Stomolophus meleagris is from July to Agust. The autolysisn phenomeno will appear if Stomolophus meleagris are storaged at room temperature, and then spoilage follows. They are hard to preserve, so most of them are processed to ready-to-eat food, such as jellyfish head except a small part are eaten fresh. However, the nutritional ingredient of Stomolophus meleagris is still not clear. Additionally, the autolysis phenomenon of Stomolophus meleagris is an important factor influencing its storage and processing. This dissertation used Somolophus meleagris from the sea area in Qingdao and has conducted comprehensive experiments from the aspects of bascic nutritional ingredients, composition of fatty acid, content of phosphatide, inorganic elements and composition of proteins. Additionally, the paper also explores the characteristics of the autolysis phenomenon of myofibrillar protein. The contents of the paper are as follows:1. From the experiments about the basic nutritional ingredients of different parts of fresh and freeze-dried Stomolophus meleagris, it is found that the nutrition of gonad and inner skin parts are much higher. However, the gonad and inner skin parts of Stomolophus meleagris are usually been discarded during processing and the application of them is rare now. The research reveals that the content of proteins, composition of fatty acid, content of phosphatide and composition of inorganic elements are proper, and even of much more nutrition than the fimbria part which takes the main proportion of Stomolophus meleagris. This is probably one of the important reasons for the popularity of Stomolophus meleagris.2. Biochemical method and electrophoretic technique are applied to analyze the protein contents of different parts of Stomolophus meleagris. It is found that the range of molecular weight of myogen from three parts of Stomolophus meleagris is large, from 200 kDa to 22 kDa, and five bands are the same which are 105 kDa,100 kDa,65 kDa,30 kDa,22 kDa respectively. The bands of myogen from the head parts of Stomolophus meleagris are more than that from fimbria and tentacle, and also gives clear bands at 200 kDa and 150 kDa. There are six clear bands for myofibrillar protein, which are 200 kDa,150 kDa,110 kDa,100 kDa,50 kDa,45 kDa, the bands of protein that can be solved in alkali are few and unclear. The difference between myofibrillar protein and the protein that can be solved in alkali from the three parts of Stomolophus meleagris is insignificant.3. The crude enzyme extracted from myofibrillar protein of Stomolophus meleagris have been characterized by biochemical and Polyacrylamide gel electrophoretic techniques. Effects of various temperature,pH, protease inhibitors and metal ions on myofibrillar protein hydrolyzing activity have been investigated.The assay reveales that there existes myofibril-bound proteinase, with optimum activities at 40℃,with optimal activitiest pH 7.0-8.0. The proteinase is partially inhibited by PMSF and EDTA protease inhibitors,and then it maybe a metalloproteinase or a serine proteinse. Effects of different metal ions for myofibrillar protein degradation are dissimilar.When the concentration of KAl(SO₄)₂ and AlCl₃ is 1 mmol/L, the Al³⁺ can partly restrain the degradation of the myofibrillar protein,especially restraining the protease which can degrade myosin heavy chain. Divalent metal ion 1 mmol/L Mn²⁺ and 5 mmol/L Mg²⁺ also suppress the autolysis of myobifrillar proteins. When the concentration of Cu²⁺ is 0.05 mmol/L,the proteins whose molecular weights are more than 90 kDa disappear absolutely,and significant degradation products are slowly emerging at 80 kDa and 90 kDa. Along with the increasing concentration of Cu²⁺,the degradation is more and more obvious. When final concentration of Ca²⁺ is 0.5 mmol/L,the degradation of myosin heavy chain is completely, and the bandings nearby the 150 kDa begin to degrade.And the it is different from the Cu²⁺ ,there are many degradation products nearby the 20⁶0 kDa,not at the 80 kDa and 90 kDa.As the concentration of Ca²⁺ is increasing, the degradation is also more obvious.There are no obvious effects of 5 mmol/L K⁺ and Na⁺ on the degradation,which are neither inhibitory nor stimulative.