Amino Acid, Fatty Acid, and Metal Compositions in Edible Parts of Three Cultured Economic Crabs: Scylla paramamosain, Portunus trituberculatus, and Eriocheir sinensis

Mud crab, swimming crab, and Chinese mitten crab are the most popular economic crabs cultured in China. However, little knowledge is available about the composition of amino acids, fatty acids, and heavy metals in those cultured crabs, despite the large amounts consumed. Scylla paramamosain, Portunus trituberculatus, and Eriocheir sinensis were, respectively, employed for an investigation of these three crabs. The results on the three representative species revealed that muscle, hepatopancreas, and ovary each had its own compositional pattern. The composition of total amino acids in all the crabs was well balanced. The proportion of flavor amino acid in muscles was higher than that in hepatopancreas and ovary. The composition of total fatty acids showed that two functional unsaturated fatty acids, docosahexaenoic acid (DHA, C22:6n-3) and eicosapentaenoic acid (EPA, C20:5n-3), were both abundant in the three crabs. The ratios of n-3/n-6 polyunsaturated fatty acids (PUFAs) in these crabs also showed that they were rich in n-3 PUFA. Among the seven metals explored, zinc, copper, and chromium were the most abundant. It also deserved attention that these crabs were threatened by high accumulation of cadmium in the edible hepatopancreas, which might arise from the pollution of water used for aquaculture. This data could be used as a reference baseline for monitoring the food properties of the three crabs in levels of amino acids, fatty acids, and metals.