Assessment of Protein Content and Amino Acid Composition in Pharaoh Cuttlefish (Sepia pharaonis) Ehrenberg 1831 from North-Western Arabian Gulf Waters

الملخص

The pharaoh cuttlefish, Sepia pharaonis, is a cephalopod species of economic and nutritional importance in the northwestern Arabian Gulf. However, the information on its protein quality and amino acid composition is still limited, especially in different body tissues and growth stages. The present study was carried out to determine the protein content and amino acid profiles of S. pharaonis collected from the north western Arabian Gulf and to examine the differences between the three weight categories and between the head and mantle tissues. Protein content was determined by the Kjeldahl method and amino acid composition was determined by high-performance liquid chromatography (HPLC). The results showed significant differences in the distribution of proteins in the tissues. In all weight categories the mantle always had higher protein levels than the head. The total protein content ranged from 19.7% to 20.3%, with the highest values observed in medium-sized specimens. Amino acid analysis showed a balanced ratio of essential and non-essential amino acids. Methionine, glycine, lysine, arginine and histidine were among the common amino acids while glutamic and aspartic acids were the predominant non-essential amino acids identified. The total concentrations of non-essential and essential amino acids declined gradually with increasing body weight, but the ratio of essential to non-essential amino acids was relatively stable (0.93-0.95), indicating that protein quality was high throughout growth. Chromatographic analysis also revealed significant quantitative differences between tissues, with mantle samples containing approximately twice the total amino acid concentration recorded in head tissues. The present findings indicate the high nutritional value of S. pharaonis and emphasise its potential as a valuable seafood resource in the Arabian Gulf region. The study adds baseline biochemical information that may aid future investigations on seafood quality, nutritional assessment, and sustainable employment of this commercially important cephalopod species.