Biotechnological potential of fish scales of the Astrakhan region

Recycling of secondary fish resources is an important task for the organization of efficient and environmentally friendly production, taking into account the principle of resource conservation. To develop a comprehensive technology for processing fish scales, an in-depth and complete study of its types, chemical composition and dimensional and mass characteristics is necessary. It has been established that the scales of the fish of the Astrakhan region are represented by two types: ganoid (in sturgeon) and elasmoid (in most commercial and pond fish). Elasmoid scales are divided into cycloid and ctenoid. The ctenoid scales (in walleye, perch and pike) have outgrowths, which give it a roughness. Such scales are usually smaller than cycloid scales. The average size of the scales of fish in the Astrakhan region varies from 6.7 to 20.5 mm, the largest size is noted in white amur (20.5 mm), carp (18.9 mm) and carp (18.8 mm), the smallest in walleye (6.7 mm) and perch (7.1 mm). The average thickness of the scales varies from 79 microns (silver carp) to 942 microns (sturgeon). The mass yield of scales from whole fish ranges from 0.4% (sturgeon) and from 2.4 to 8.0% in representatives of the elasmoid type. The content of nitrogen-containing substances in the scales of the studied fish varies from 43.2% in perch to 68.7% in carp, the alkali-soluble protein fraction was found from 16.7% (sturgeon) to 58.4% (silver carp). In addition to the target component, impurities of water- and salt-soluble proteins, minerals and various pigments (chromatophores) were found in the scales, which must be separated in the technological process. As a result of the research, the classification of fish scales of the Astrakhan region by chemical composition has been compiled, taking into account the prospects for protein extraction. These studies are fundamental for creating integrated technological solutions for processing fish scales to obtain a wide range of food and feed products.