Veterynarna biotehnologija – Veterinary biotechnology, 2020, 36, 93-100 [in Ukrainian]. https://doi.org/10.31073/vet_biotech36-09
State Scientific and Research Institute of Laboratory Diagnostics and Veterinary and Sanitary Expertise
RESEARCH OF CHANGE OF ACID FAT AND PROTEIN CONTENT IN SAMPLES OF FROZEN FISH OF DIFFERENT SPECIES DEPENDING ON THE CHANGE OF ORGANOLEPTIC PROPERTIES
Introduction. The source of the human body's essential fatty acids is a variety of marine fish with a high fat content: mackerel, herring, baltic herring etc. At the same time, due to the high content of unsaturated fatty acids, fish fat is unstable and under poor storage conditions easily susceptible to oxidative deterioration, thus decreasing the quality of the product particularly organoleptic properties and, consequently, change in its chemical characteristics.
The goal of the work was to investigate the change of chemical parameters of frozen fish of different species depending on the degree of change of its organoleptic quality properties.
Materials and methods. The studies were conducted on the basis of the laboratory of organoleptic and physicochemical studies of the Research Chemical and Toxicology Department of the State Research Institute for Laboratory Diagnostics and Veterinary and Sanitary Expertise. Samples of frozen fish of three species with a high fat content were selected as the material for the study: mackerel, herring, and sprat. Investigation of organoleptic and chemical parameters of fish quality was carried out in accordance with the requirements of current national standards.
Results of research and discussion. The results of organoleptic studies of fish of doubtful freshness indicate on a violation of the temperature regime and long-term storage of frozen fish, which is more pronounced in mackerel and herring samples, in which significant subcutaneous yellowing and odor change were found.
Although the results of the organoleptic study showed the weakening of the consistency of fish meat of doubtful freshness, the results of chemical analysis indicated a change in the protein content, compared with parameters of fresh frozen fish. At the same time in mackerel with significant changes in organoleptic quality parameters (appearance and smell), the change in number of acid fats was higher by 86%, compared to mackerel, which met the requirements of the current (SSTC)DSTU 4868. The same tendency was found in herring and sprat samples: parameters increased by 94% and 87% respectively. This indicated on a significant level of oxidation of fats.
Conclusions and prospects of further research:
1. Under the current regulations of Ukraine, it is necessary to clearly state that the study of frozen fish by chemical, microbiological, toxicological, radiological and other methods should be carried out after organoleptic studies, which indicate on the freshness of the product.
2. The weakening of the frozen fish consistency of doubtful freshness does not always indicate on a significant decrease in the protein content in muscle tissue, as evidenced by the chemical study.
3. The change in odor and the presence of subcutaneous yellowing, which has penetrated into the meat, indicated on a significant oxidation of fat in all tested species of frozen fish. This was confirmed by an increase in acidic fat by 86%, 94% and 87%, respectively, compared to fresh frozen fish.
4. An objective assessment of changes occurring in frozen fish during storage requires the implementation of comprehensive studies that characterize the quality and safety of the product.
Keywords: fish, organoleptic studies, chemical studies.