Changes in Amino Acids Content in Muscle of European Eel (Anguilla anguilla) in Relation to Body Size
European eels (Anguilla anguilla) belong to Anguilliformes order and Anguillidae family. They are generally classified as warm-water fish. Eels have a great commercial value in Europe and Asian countries. Eels can reach high weights, although their commercial size is relatively low in some countries. The capture of larger eels would facilitate the recovery of the species, as well as having a greater number of either glass eels or elvers for aquaculture. In the last years, the demand and the price of eels have increased significantly. However, European eel is considered critically endangered by the International Union for the Conservation of Nature (IUCN) Red List. The biochemical composition of fishes is an important aspect of quality and affects the nutritional value and consumption quality of fish. In addition, knowing this composition can help predict an individual’s condition for their recovery. Fish is known to be important source of protein rich in essential amino acids. However, there is very little information about changes in amino acids composition of European eels with increase in size. The aim of this study was to evaluate the effect of two different weight categories on the amino acids content in muscle tissue of wild European eels. European eels were caught in River Ulla (Galicia, NW Spain), during winter. The eels were slaughtered in ice water immersion. Then, they were purchased and transferred to the laboratory. The eels were subdivided into two groups, according to the weight. The samples were kept frozen (-20 °C) until their analysis. Frozen eels were defrosted and the white muscle between the head and the anal hole. was extracted, in order to obtain amino acids composition. Thirty eels for each group were used. Liquid chromatography was used for separation and quantification of amino a cids. The results conclude that the eels are rich in glutamic acid, leucine, lysine, threonine, valine, isoleucine and phenylalanine. The analysis showed that there are significant differences (p < 0.05) among the eels with different sizes. Histidine, threonine, lysine, hydroxyproline, serine, glycine, arginine, alanine and proline were higher in small eels. European eels muscle presents between 45 and 46% of essential amino acids in the total amino acids. European eels have a well-balanced and high quality protein source in the respect of E/NE ratio. However, eels with higher weight showed a better ratio of essential and non-essential amino acid.
Digital Object Identifier (DOI): doi.org/10.5281/zenodo.2576930Procedia APA BibTeX Chicago EndNote Harvard JSON MLA RIS XML ISO 690 PDF
 J. Peñalver, P. Muñoz, E. Romero, E. Barcala, and E. Dolores, “First record of the juvenile phase of the European eel Anguilla anguilla in the hypersaline lagoon, Mar Menor, Southeastern Spain,” Revista de Biología Marina y Oceanografía, vol. 50, pp. 391-395, Aug 2015.
 F. Cobo, J. Sánchez, R. Vieira, and J. Servia, “Seasonal downstream movements of the European eel in a Southwestern Europe river (River Ulla, NW Spain)”. Nova Acta Científica Compostelana, vol. 21, pp. 77-84, Jun 2014.
 C. Fonseca, F. Chavarría, and F. Mejía-Arana, “Seasonal variation of the proximal composition in three species of commercial importance of the Gulf of Nicoya, Puntarenas, Costa Rica,” in Revista de Biología Tropical, vol 61, pp. 429-437. Aug 2012.
 H.H. Huss, “Chemical composition. In Fresh fish: its quality and changes in its quality,” in FAO Fishing Technical Document, Rome, Italy, vol. 348, 1998.
 J. Mataix, “Protein foods,” in Nutrition and Human Food. I.” Madrid, Spain, 2015.
 J. Román, C. Gómez, J. Aranceta, A. Villarino, P. Moreno, C. Iglesias, C. Muñoz, I. Ortuño, P. Pons, and M. Cáceres, “Fish and health,“ in Fish in the diet, Health Promotion Service, Public Health Institute, General Directorate of Public Health, Food and Consumption and Health and Consumer Protection, Madrid, Spain, 2005.
 B. Mohanty, A. Mahanty, S. Ganguly, T. Sankar, K. Chakraborty, A. Rangasamy, et al., “Amino Acid Compositions of 27 food fishes and their importance in clinical nutrition,” J. Amino Acids, vol. 2014, pp 1-7. Aug. 2014
 N. Gökoğlu, and P. Yerlikaya, “Chemical composition of fish,” in Seafood Chilling, Refrigeration and Freezing, Science and Technology, John Wiley & Sons, Ltd, Reino Unido, 2015.
 D. Franco, L. Gonzalez, E. Bispo, P. Rodriguez, J. I. Garabal, and T. Moreno, “Study of hydrolyzed protein composition, free amino acid, and taurine content in different muscles of Galician blonde beef,” J. Muscle Foods, vol. 21, pp 769-784. Sept. 2010.
 M. L. Alonso, A. I. Álvarez, and J. Zapico, “Rapid analysis of free amino acids in infant foods,” J. Liquid Chromatogr., vol. 17, pp. 4019-4030. Jun. 1994.
 J. Kolman, and K. Röhm, “Lipids” in Bioquímica humana, Panamericana S.A. Ed., Spain, 2012.
 G. Wu, “Amino acids: metabolism, functions, and nutrition,” in Amino Acids, vol. 37, pp 1-17. May 2009.
 S. Peng, C. Chen, Z. Shi, and L. Wang, “Amino acid and fatty acid composition of the muscle tissue of yellowfin tuna (Thunnus albacares) and bigeye tuna (Thunnus obesus),” J. Food Nutr. Res., vol 1, pp 42-45. Aug. 2013.
 D. Kocatepe, and H. Turan, “Chemical composition of cultured sea bass (Dicentrarchus labrax, Linnaeus 1758) muscle,” J. Food Nutr. Res., vol. 51, 33-39. Jan. 2012.
 Ö. Özkan, and N. Erkan, “A preliminary study of amino acid and mineral profiles of important and estimable 21 seafood species,” Br. Food J., vol. 113, pp 457-469. 2011.
 A. Osibona, K. Kusemiju, and G. Akande, “Fatty acid composition and amino acid profile of two freshwater species, African catfish (Clarias gariepinus) and tilapia (Tilapia zillii),” Afr. J. Food Agric. Nutr. Dev., vol. 9, pp 1-14. Jan. 2009.
 G. Özyurt, and A. Polat, “Amino acid and fatty acid composition of wild sea bass (Dicentrarchus labrax): a seasonal differentiation,” Eur. Food Res. Technol., vol. 222, pp 316-320. Sept. 2006.
 A. Zuraini, M. Somchit, M. Solihah, Y. Goh, A. Arifah, M. Zakaria et al., “Fatty acid and amino acid composition of three local Malaysian Channa spp. Fish,” Food Chem., vol. 97, pp 674-678. Aug. 2005.
 T. Sankar, and A. Ramachandran, “Changes in biochemical composition in Indian mayor carps in relation to size,” Fish. Technol., vol. 38, pp 22-27, 2001.
 W. Ng, and S. S. O. Hung, “Amino acid composition of whole body, egg and selected tissues of white sturgeon (Acipenser transmontanus),” Aquaculture (Amsterdam), vol. 126, pp 329-339. Oct. 1994.
 J. Toppe, S. Albrektsen, B. Hope, and A. Aksnes, “Chemical Composition, mineral content and amino acid and lipid profiles in bones from various fish species. Comp. Biochem. Physiol. B. Biochem. Mol. Biol. vol. 146, pp 395-401. Mar. 2007.
 T. V. Sankar, R. Anandan, S. Mathew, K. K. Asha, P. T. Lakshmanan, J. Varkey, et al., “Chemical composition and nutritional value of anchovy (Stolephorus commersonii) caught from Kerala Coast, India”. Euro. J. Exp. Bio. vol. 3, pp 85-89. Jan. 2013.
 FAO (Food and Agriculture Organization of the United Nations) FishFinder. Species Fact Sheets Anguilla anguilla. (2018). http:// http://www.fao.org/fishery/species/2203/en (Last accesed 26 January, 2019).