| Shellfish is one of marine products, which is popular with daily food among the people. Because it contains very rich nutrients, such as amino acids, fatty acids and other nutrients. These nutrients are in line with the healthy diet requirements. In addition, with the rapid development of modern, marine heavy metals pollution becomes very bad, with it the growth of various shellfish in the marine pollution. People eat shellfish contaminated by heavy metals, it will lead to a variety of diseases. Therefore, the evaluation of the nutritional value of shellfish is very necessary. The main indicators of evaluation of the nutritional value of foods includes general nutrition content, composition and content of amino acid and fatty acid and cholesterol content. The amino acids (especially the essential amino acids) and unsaturated fatty acids are very important to the growth and health. Therefore, the analysis of these two nutrients is very necessary. Excessive heavy metals in shellfish may reduce its nutritional value. Thus, the analysis of heavy metals in shellfish also has an important meaning. Consequently, for evaluation of the quality of shellfish products, the three aspects have important practical significance.This article is divided into two parts, on the one hand is that the establishment, improvement and evaluation of method; on the other hand is that quality evaluation of shellfish with the established method. Details are as follows:This study established high performance liquid chromatography mothod with pre-column derivatization with 2,4-Dinitrochlorobenzene and determinated 18 kinds of amino acids in shellfish. Sample hydrolysis conditions, such as hydrolysis time, temperature, acidity and amino acid derivatization temperature, time, acidity and concentration of derivatization reagent were optimized. Amino acids chromatographic separation and detection conditions were also optimized. Amino acids by gradient elution, the calibration curves of the 18 amino acids were established. The correlation coefficients of the calibration curves varied in range from 0.9915 to 0.9991; detection limit was 0.24~2.37μg/mL; the recovery was 88.6%~115.7%. I twas showed that the method was no interference, easy operation, high sensitivity, and can be used for detection of amino acids in shellfish.This study also established the analysis method of 7 kinds of unsaturated fatty acids in shellfish by gas chromatography - mass spectrometry. The sample preparation, such as the extraction solvent ratio, extraction time, methylated reagents, time and temperature conditions and derivatization time, temperature, concentration of derivatization reagent were optimized. Also, the separation and testing conditions of unsaturated fatty acids were optimized. The calibration curves of the 7 unsaturated fatty acids were established. The correlation coefficients varied in range from 0.9925 to 0.9953; the detection limit was: 0.36~0.85μg/mL, the recovery rate was: 76.68~106.68%. It was showed that the method was no interference, easy operation, high sensitivity, and can be used for shellfish analysis and detection of unsaturated fatty acids. The test also measured 4 heavy metals, namely, Pb, Cd, As and Hg in shellfish by national standards and my lab conditions.This study focused on amino acids, unsaturated fatty acids and hesvy metals these three aspects to evaluate the nutritional quality of shellfish. Amino acid analysis of shellfish results showed that (1) different species of shellfish samples, the growth shellfish samples in different months and shellfish in different sea areas were not different from amino acids'varieties, but the contents wree different. Clam, Short-necked Clam, Oyster, Razor Clam and Hairy Clam had higher nutritional value in the Bohai area. (2) Principal component analysis of shellfish amino acid data results showed that three principal components were elected and the cumulative contribution rate was 84.16%. It indicated that most information of original data can be explained by the three principal components. These included Asp, Glu, Thr, Val, His, Ile, Leu, Lys, Phe and so on. (3) Essential amino acids of shellfish was greater than 30% in the total amino acids and had high nutritional value. The relatively high contents of glutamic acid and aspartic acid may be connected with the flavor of shellfish itself. (4) Amino acids were different between scallop tissues, adductor muscle were higher than scallop mantle. (5) Amino acid contents of Clam, Short-necked Clam, Oyster, Razor Clam and Hairy Clam were analysed by the Independent-Samples T Test, and the results showd that shellfish samples in the two sea areas contained 17 amino acids, but the composition in amino acids were different (P<0.05).Fatty acid composition analysis of shellfish showed that (1) different species of shellfish samples, the growth shellfish samples in different months and shellfish in different sea areas contained palmitic acid, oleic acid, linoleic acid, linolenic acid, arachidonic Acid, EPA and DHA, but the contents were different. (2) The ratio value of n-3/n-6 were greater than 2, and it indicated that shellfish were good source of n-3 unsaturated acids. (3) The contents of unsaturated acids in shellfish in the two sea areas were analysed by the Independent-Samples T Test, and the results showed that shellfish samples in the two sea areas contained 7 unsaturated fatty acids, but the composition in unsaturated fatty acids were different (P<0.05). (4) Unsaturated fatty acids were different between scallop tissues, scallop mantle were higher than adductor muscle.Pb, Cd, As and Hg contents of the 4 heavy metals analysis showed that (1) the contents of Hg and Pb in the shellfish samples were not out of limits in the two sea ares, and no accumulation effect; the content of Cd were out of limits in some shellfish and had different levels of enrichment; the content of As were out of limits very seriously and the enrichment was the most serious. Scallop heavy metal adsorption were different between tissues; the content of Cd were out of limits in scallop mantle; As exceeded limit in Chlamys farreri, Pb and Hg were not excessive; enrichment ability of Cd and As than were greater than Pb and Hg. (2) Heavy metals contents were different between scallop tissues, adductor muscle were lower than scallop mantle. (3)The level of heavy metals were compared by MPI value of Clam, Short-necked Clam, Oyster, Razor Clam and Mytilus edulis in the two sea ares.
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