In recent years, there has been increased interest in the production of gelatin from alternative sources, such as raw fish materials. Traditionally, gelatin is obtained using an acidic or alkaline treatment. However, these methods have some disadvantages, such as the long times for processing raw materials and the use of large amounts of water and chemicals. Furthermore, milder processing regimes are required for producing fish gelatin. Enzymes could be the solution for improving the technology of fish gelatin production, due to their specificity and ability to increase the rate of collagen digestion. In this work, samples of gelatin from cod skin were obtained using enzymes of bacterial (protosubtilin) and animal (pancreatin) origins. The use of enzymes reduced the duration of extraction by 40%, and the yield of the final product was increased from 51% to 58–60%. The dependence of the contents of the main components of the secondary structure of gelatin and its rheological and thermal properties on molecular weight was also established. In this study, the gelatins obtained without enzymes and with protosubtilin were shown to have the most desirable characteristics, namely of the highest molecular weights and the highest proportion of ordered structures.

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The Atlantic cod (Gadus morhua) and red king crab (Paralithodes camtschaticus) processing wastes are massive and unutilized in the Murmansk region of Russia. The samples of skin-containing waste of Atlantic cod fillets production were hydrolyzed using enzyme preparations derived from red king crab hepatopancreases, porcine pancreases, and Bacillus subtilis bacteria. The activity of enzymes from crab hepatopancreases was significantly higher than the activity of enzymes derived from other sources. The optimal conditions of the hydrolysis process have been figured out. The samples of cod processing waste hydrolysate were analyzed for amino acid composition and molecular weight distribution. The samples of hydrolysate were used as core components for bacterial culture medium samples. The efficiency of the medium samples was tested for Escherichia coli growth rate; the most efficient sample had an efficiency of 95.3% of that of a commercially available medium based on fish meal. Substitution of medium components with those derived from industrial by-products is one of the ways to decrease a cost of a culture medium in biopharmaceutical drug production.

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.

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