Microstructural analysis of frozen and salted fish and seafood meat

Abstract

To evaluate the quality and safety of fish and seafood meat, along with generally accepted methods, new histological research methods are used, which allow establishing microscopic changes in fresh, spoiled, and canned foods. The purpose of this study is to examine the microscopic structure of salted fish meat (Herring, Pollock) and seafood (squid, mussels) by freezing. It was confirmed that fish meat is composed of skeletal muscle, fibrous connective (endo- , perimysium) tissues with blood, lymphatic vessels, and nerves. Muscle tissue fibres have the appearance of cylindrical formations, with well-defined transverse striation and numerous nuclei. The basis of seafood meat is smooth muscle tissue with layers of loose fibrous connective tissue, blood vessels, and nerve fibres. Smooth muscle cells are fusiform in shape, without transverse striation and with a single nucleus. During freezing of fish meat at a temperature of -18ºС, ice crystals are small and well-defined in the endo- and perimysium, and at a temperature of -23ºС – in muscle fibres. When fish is re-frozen, large ice crystals form in both the muscle fibres and the endomysium and perimysium of the muscles, the muscle fibres are fragmented and have cracks. In frozen seafood meat, there is a deformation of bundles of smooth muscle cells and their fragmentation. During the salting of fish meat, in the dehydration phase, a decrease in the diameter of muscle fibres and the width of the endo- and perimysium is noted, the transverse striation and nuclei of muscle fibres are well expressed, and in the dehydration phase, the reverse processes occur. Meanwhile, the fibres become straight with cracks and crevices, and graininess is noticeable in the endomysium and perimysium. Based on the results obtained, it is possible to evaluate the microstructure of frozen and salted fish and seafood meat, which is important when monitoring the suitability of food products for consumers