Analysis of total and free amino acid compositions of fishery byproducts from three commonly consumed fish species in South Korea

Largehead hairtail (Trichiurus japonicus), kwangtung skate (Dipturus kwangtungensis), and mottled skate (Raja pulchra) are the most popular aquatic products in Korea. In the present study, total and free amino acid analyses were performed to confirm the usability of byproducts from largehead hairtail (head and fins) and skates (skin and liver). Amino acid contents were determined using specific methods and high-performance liquid chromatography. Notably, 18 types of total amino acids and 19 free amino acids were identified in the byproducts of largehead hairtail, kwangtung skate, and mottled skate. Among the amino acids, the total amino acids glycine and glutamate/glutamine and the free amino acids leucine, alanine, and glycine exhibited the highest contents in the byproducts of the three species, indicating that the byproducts contained high-quality proteins. Conclusively, these results suggest that the byproducts are potential materials for producing nutritious foods, protein supplements, cosmetics, functional materials, and nutraceuticals. Overall, these data indicate that fishery byproducts can be used as recyclable resources.