| Chinese mitten crab (Eriocherir sinensis H. Milne-Edwards), also called river crab, is one of the specific high economic value aquatic product in china. In this paper, the conventional qualities and meat textural properties were analyzed, some of the taste compounds were determined, the protein fractions from crabmeat were studied, and the differences in crab quality were revealed.River crabs were analyzed for external morphological characters, biological characteristics, biological indices, proximate composition, and also evaluated for the conventional quality by using the method of combination index. The quality indices differences were observed in abdomen color, height/body weight, index of liver/body, index of gonad/liver, leg meat/body, water content (male), crude fat content (male), ash content (female). The sequence of excellence was as following: A, B, C, D (male); B, D, A, C (female).By using histological and chemical methods, the myofibril fragmentation index (MFI), muscle diameter, and collagen content were determined, the meat tenderness was compared by using the method of combination index. The three methods can be used to classify the crabmeat tenderness, but there was disagreement in the orders of crabs from different locations.The muscle fiber diameter was the most effective tenderness evaluation method. The results showed that: myofibril fragmentation index was 50～90, muscle fiber diameter was 350～570μm; total collagen 0.1～0.18 g/100g; heat soluble collagen 0.03～0.12 g/100g, heat insoluble collagen 0.04～0.1 g/100g. Meat tenderness of Chinese mitten crabs by using combination index in order of best to worst was B, C, A, D (male); A, C, B, D (female).According to sensory investigation result, the river crabs, one was scored high and the other one scored low, were compared in this study. The non-volatile taste active compounds, including free amino acids in meat and fatty acids in crab viscera were analyzed. The glutamic acid, glycine, arginine and alanine were the major free amino acids, accounting for about 80%(W/W)of the total free amino acids. The monounsaturated fatty acids were dominating with a percentage of 43, followed by saturated fatty acids 25%(W/W) of the total fatty acids. Oleic acid (C18:1) was the dominant fatty acid, about one third of the total fatty acids, followed by palmitic acid (C16:0) with a percentage of 20(W/W). The differences in free amino acids and fatty acids composition between the crabs from two different locations were obvious. The result showed that taste activity value (TAV) could be used as the flavor evaluation index of river crab.The protein fractions with different solubility were determined and analyzed by sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE). The nitrogen content of water soluble protein and non protein nitrogen of crabmeat were 500 mgN/100g and 1200 mgN/100g respectively, indicated that the content of taste compounds was high and the meat was tenderness and succulent. SDS-PAGE patterns of water soluble protein and salt soluble protein for crabmeat were analyzed by Quantity One electrophoresis software, the results showed that there was a little different in protein banding patterns and the similarities between them were higher than 70%. The quality of river crabs can be evaluated by conventional index, texture index and flavor index. |
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