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Oregano essential oil is predominantly utilized in the application of food preservation. However, the antimicrobial activity of oregano essential oil on the Atlantic cod is still unclear. In the present study, we evaluated the antimicrobial effect of oregano essential oil on the shelf-life of Atlantic cod and sensory properties under different treatments. The study showed that the shelf life of the thawed cod loins with oregano essential oil decreased by two days compared to the untreated group. The finding of the antimicrobial activity of oregano essential oil was in agreement with previous studies, but it does not prolong the shelf life of cod loins significantly.

Total content of arsenic in muscles and liver of the main commercial fish species landed in the Barents Sea, as atlantic cod Gadus morhua, haddock Melanogrammus aeglefinus, long rough dab (american plaice) Hippoglossoides platessoides, greenland halibut Reinhardtius hipoglossoides, and european plaice Pleuronectes platessa is considered on the data collected in 2009–2020. The average As content in the muscles of examined fish met hygienic standards for the permissible concentration, i.e. 5 μg/g of wet weight, but the content in liver was about twice higher. High variability of the total As content in muscles of juveniles and adult fish was observed that imposed excessive restrictions on their sales as food products. Taking into account that the increased content of arsenic in tissues of fish in the Barents Sea has natural origin, these restrictions are not directly related to actual quality of the fish raw materials. There is recommended to account the natural background of As and establish a regional criterion for the allowable concentration of total arsenic in the muscles of fish landed in the Barents Sea as 12 μg/g WW. For principal decision on the safe level of arsenic content in fish products, introduction of a new standard for the level of inorganic arsenic content is recommended, that is more reliable and representative indicator.

Infectious diseases are one of the main factors having a negative influence on the Atlantic cod aquaculture. Fish epidermis is a barrier which provides primary interaction between the host and pathogenic organisms. The study of the epidermis of the Atlantic cod Gadus morhua L. has been carried out on the experimental base of the Nord University of Bodo (Norway). Ultrathin sectioning of cod epidermis has been carried out with the help of the Department of Electronic Microscopy of the University of Tromso (Norway). Embryos, pre-larvae from the moment of hatching and larvae up to 3 weeks after hatching, as well as juvenile cod at the age of 5 months, 1 year and 1.5 years have been selected for light-optical and electronic microscope examination. The material for optical studies is fixed with 10 % neutral formalin. The fixation of the material for electronic microscope studies has been made with 25 % glutaraldehyde (sodium cacodylate, pH 7.2). Saccular cells have been found in the cod epidermis of all investigated age groups. The cells have a round or predominantly oval shape and also vacuoles. Vacuoles are filled with an electron-transparent material, but most cells do not have secretory content. It has been found out that secretory material in most cases was absent in the vacuoles of opened cells, where vesicles and tubules, however, remained. During the research, morphological and functional features of these cells are first identified on the basis of studying their distribution, quantity and chemical composition depending on the age of the fish. New data on the spatial distribution of Atlantic cod saccular cells at different stages of ontogenesis have been presented. The results indicate the secretory, bactericidal and protective functions of the saccular cells in the epidermis of Atlantic cod and reflect the ecological features of cod as an epibenthic-pelagic species.

The technology of producing a new type of boiled sausage products from pork with the addition of microwave blanched cod liver or semifinished cod liver oil, fish protein isolate from blue whiting or minced blue whiting has been developed to increase the biological value of lipids and to increase the product safety. Sensory characteristics and structural parameter (penetration force with a spherical indentor) have been chosen for optimal level estimation. The optimal level of the penetration value has been found using non-linear pair regression of it on the texture value. The common optimization parameter has been developed according to both characteristics using the significance coefficients obtained by the expert method. The optimal formulation for the preparation of this type of sausage products has been determined using experimental design theory; the biological value of the product has been calculated; the general chemical composition, physical, chemical and structural and mechanical parameters (penetration value) of finished products have been determined. Microbiological characteristics of the sausages have been controlled during storage, the recommended shelf life of 5 days at 4...5 °C has been established. The effect of storage conditions on the quality of the fat fraction of sausages has been noted. Special attention has been paid to color formation (it has been decided to abandon the traditional sodium nitrite in favour of tomato paste in slightly acidic medium) and emulsion stabilization. The project of the technical documentation has been developed: it includes technical conditions and technological instructions.