Gelatin (G) was extracted from the skin of Atlantic cod at different pH of the aqueous phase (pH 3, 4, 5, 8 and 9) and at a temperature of 50 ± 1 °C. The yield of gelatin (G3, G4, G5, G8, and G9, respectively) was 49–55% of the dry raw material. The influence of extraction pH on the physicochemical and functional properties of gelatin was studied. Sample G5 was characterized by higher protein content (92.8%) while lower protein content was obtained for sample G3 (86.5%) extracted under more aggressive conditions. Analysis of the molecular weight distribution showed the presence of α- and β-chains as major components; the molecular weight of the samples ranged between 130 and 150 kDa, with sample G5 having the highest molecular weight. IR spectra of all samples had absorption bands characteristic of fish gelatin. The study of the secondary structure demonstrated higher amounts of ordered triple collagen-like helices for G5 extracted under mild conditions. Accordingly, sample G5 formed gels with high values for the storage modulus and gelling and melting temperatures, which decrease as pH changes into acidic or alkaline regions. In addition, the differential scanning calorimetry data showed that G5 had a higher glass transition temperature and melting enthalpy. Thus, cod skin is an excellent source of gelatin with the necessary physicochemical and functional properties, depending on the appropriate choice of aqueous phase pH for the extraction.

Introduction. Near-infrared (NIR) spectroscopy is a modern instrumental method for the quantitative and qualitative analysis of various objects. The method for analyzing the NIR spectra of diffuse reflection was successfully used to identify plant and animal species, drugs, etc. The issue of identifying objects of marine fishery is currently extremely important for modern fisheries, environmental monitoring, and identifying counterfeit products. The research objective was to identify the fish taxa using the discriminant analysis of reflection in the NIR region. Study objects and methods. The research featured 25 dried and defatted muscle tissue samples taken from different species of marine fish caught in the North Fishing Basin. The spectra were measured using a Fourier IR-spectrophotometer Shimadzu IRTracer-100 with a diffuse reflection measuring instrument. Measurements were carried out in the range from 700 to 7,000 cm–1. Mathematical processing of the spectra was performed using the MagicPlot Pro program ver. 2.9 (Magicplot Systems, LLC), while the statistical program IBM SPSS Statistics ver. 25 (IBM Corp., USA) was exploited to perform the linear discriminant analysis. Results and discussion. The spectra of diffuse reflection of NIR radiation were measured for 25 samples of marine fish species of different taxa caught in the North Fishing Basin. The range of 3,700 to 6,700 cm–1 was selected to assess the proximity of spectra in linear discriminant analysis. In this range, the team identified 19 spectral peaks, which made a significant contribution to canonical discriminatory functions. The resulting canonical discriminatory functions made it possible to divide the objects into eight nonoverlapping groups corresponding to each biological group of the fish. The analysis was based on a comparison of Mahalanobis distance between the group centroids and the NIR spectra of each studied fish species. The minimum Mahalanobis distance between the nearest groups was statistically significant. Conclusion. The research proved the possibility of taxonomic identification of marine fish based on measuring the spectral characteristics of their muscle tissue proteins in the range of 3,700 to 6,700 cm–1 of near-infrared region and classification by linear discriminant analysis.

Introduction: Petroleum industry is a fundamental part of the economy of the Russian Federation. One of the approaches to up-to-date assessment of human health effects of subthreshold concentrations of pollutants is to determine changes in the immune and hormonal status in people with non-occupational or occupational exposure to industrial contaminants. Objective: To establish body mass indices, hormonal and immune status in workers of an oil producing enterprise and the population environmentally exposed to low concentrations of airborne pollutants emitted by oil production facilities. Materials and methods: The survey covered the population living in the area affected by oil production facilities and 131 oil extraction workers. We estimated the body mass index (BMI) of the subjects and tested their blood serum for the four main classes of antibodies (immunoglobulins IgA, IgM, IgG, and IgE), circulating immune complexes (CICs), and the levels of thyroid-stimulating hormone (TSH), thyroxine (free T4), and cortisol. Results: We established that all the subjects (in both observation groups (workers (group I) and residents (group II), and the comparison group) were overweight but BMI of the industrial workers was within the normal range. We also found that the hormonal parameters did not differ significantly between the groups but the level of the stress hormone cortisol was lower among the workers. IgA and IgE levels were significantly higher in the exposed residents. A high level of circulating immune complexes in both population groups indicates high prevalence of chronic disorders. Conclusions: The study proves the need for an in-depth study of indices of the endocrine and immune systems and a clinical examination of both the exposed population and industrial workers. It is especially important to study the markers of exposure to oil production emissions in the biological media of the general population.

It is well known that fish belonging to the Salmonidae family differ in their nutritional value. Anatomical and morphological features of different salmon species have a certain similarity; therefore, representatives of this family are most often falsified. Assortment falsification of products from fish of this family is usually carried out by replacing more valuable species with cheaper ones with a reduced nutritional value. Most often, counterfeiting of Atlantic salmon (salmon) by Far Eastern ones (chum salmon, pink salmon, chinook salmon, coho salmon) is found. Near infrared spectroscopy (NIR) is now increasingly used for identification and authentication of closely related organisms, in some cases being a rapid method replacing genetic analysis. We have obtained diffusion reflectance spectra of NIR radiation for three species of fish from the Northern Basin belonging to the salmon family. The best classification by fish species has been obtained by analyzing the NIR spectra of pre-dried fat-free muscle tissue samples. In case of wet samples, the observed differences are less significant, up to insignificant differences in individual values from neighboring clusters. The possibility of using the method of linear discriminant analysis of the NIR reflection spectra of muscle proteins for the species identification of fish has been shown.

The results of the isolation of collagen hydrolysates from tissues of two Arctic marine organisms are presented. Extraction and use of marine organism collagen is a part of complex waste less processing of sea catches. Possible ways of preparing water-soluble collagen hydrolysates from different sources were studied. It is established that for preparing soluble collagen hydrolysate from skin of cod Gadus morhua acid hydrolysis in 0.3% acetic acid is suitable. Purification of solution by means of ultrafiltration gives a pure collagen hydrolysate with mass fraction of the main substance about 98%. Collagen of muscular skin bag of holothuria Molpadia borealis is almost insoluble in acid and alkali solutions. The major mass of collagen remains in an insoluble residue. The analysis of infrared spectrum transmission and chemical analysis of the general carbohydrates and collagen in different fractions showed that as a result of acid and alkaline processing of raw materials the glycosaminoglycans (GAG) and some quantity of collagen are extracted, their main quantity was determined in alkaline extracts. For extraction of soluble collagen from insoluble residue it is required enzymatic by pepsin in acidic medium. Properties of holothurian collagen and fish collagen are different. The preparation of water-soluble collagen derivatives requires using enzymatic hydrolysis.