Evaluation of the Nutritional Composition and Quality of Muscles in Two Cuttlefish Species

Sepiella japonica is widely distributed on Zhejiang and Fujian coasts and is one of the four major fishery products in the East China Sea. Its meat is delicious, has high nutritional value, and is loved by consumers. Sepia esculenta is widely distributed on the Japanese coasts and South and East China Sea waters, with the advantages of fast growth and development, short life cycle. Hence, it is an important economic cephalopod in China's northern fisheries. With the improvement of people's living standards, there is a higher demand for food quality. Red meat contains high levels of saturated fatty acids and cholesterol, which increase the risk of cardiovascular disease and colon cancer when consumed for an extended period. Cephalopods are low-fat and high-protein aquatic products, which are easier to digest and absorb than livestock meat and are widely welcomed by consumers. The quality of cuttlefish muscle is an essential factor affecting the value of cuttlefish products. So far, many scholars have studied the nutritional composition of cuttlefish muscle, but few reports have been made on its quality differences. Therefore, this study aimed to investigate the nutritional composition and quality differences of two cuttlefish muscles and evaluate their nutritional value. For that, the conventional nutrient composition, textural characteristics, cooking loss rate, formaldehyde (FA) content, amino acid and fatty acid composition, and mineral elements of S. japonica and S. esculenta were analyzed from specimens caught in large quantities in the Zhoushan area. Ten cuttlefish of each species were collected, each as an independent sample. The average carcass length for S. japonica was (104.00±0.24) mm and the average body weight (134.00±0.11) g, while for S. esculenta specimens, the averages were (162.00±0.17) mm and (356.00±0.09) g. The fresh samples were transported to the laboratory within 30 min. The basic nutrients of cuttlefish muscle were determined by the national standard method, texture characteristics by the TPA model, FA content by HPLC, amino acids content using the amino acid autoanalyzer, fatty acid content by gas chromatography, and mineral content by microwave digestion. The results showed that the crude protein and crude fat contents of S. japonica muscles were not significantly different from those of S. esculenta (P > 0.05). The moisture content was significantly lower in S. japonica than that of S. esculenta (P < 0.05), and the crude ash content was significantly higher than that of S. esculenta (P < 0.05). The hardness, elasticity, adhesive, masticatory, and cohesive properties of S. esculenta muscles were significantly higher than those of S. japonica (P < 0.05). The FA contents of the two cuttlefish muscles were 0.56 mg/kg and 1.18 mg/kg, respectively, following the national health standards. Muscles of both cuttlefish species showed 17 hydrolyzed amino acids, and the first limiting amino acid was tryptophan. Also, for both species, the ratio of essential amino acids to total amino acids was higher than 31%, and the ratio of essential amino acids to non-essential amino acids was higher than 53%. S. esculenta was closer to the ideal protein pattern recommended by the FAO/WHO, and its essential amino acid index (EAAI) was as high as 82.99. Twenty types of fatty acids were detected in the muscles of both cuttlefishes. The total contents of C20:5n-3 (EPA) and C22:6n-3 (DHA) were higher than 40% in S. japonica, which were significantly higher than in S. esculenta (P < 0.05). The muscles of both cuttlefish species were rich in many inorganic elements required by humans. The two cuttlefish muscles were rich in K, P, Mg, and Ca, with the greatest difference observed for P. The P and Zn contents of S. esculenta muscles were significantly higher than those of S. japonica (P < 0.05), while the I content of S. japonica muscles was significantly higher than that of S. esculenta (P < 0.05), reaching 13.6 mg/kg and 9.2 mg/kg, respectively. Macronutrients had the highest content of K and P and the trace elements, Zn and I. Overall, this study showed differences in the nutritional composition and quality of the two cuttlefish muscles, but both were high-quality and low-fat protein sources with good exploitation value. This study provides the scientific basis for utilizing the cephalopod marine resources in the East China Sea.