Authors : A. Mateyeva, R. Uazhanova, I. Saranov, S. Shakhov, B. Kutsova, I. Kuznetsova and I. Glotova
Abstract: The goal of this study was to justify and develop a new rapid method for differentiating the frozen-thawed cycles of fish at the stages of the life cycle of fish products based on Differential Scanning Calorimetry (DSC). The object of research was the rainbow trout (Oncorhynchus mykiss) of the genus Oncorhynchus of salmon family (Salmonidae). For the analysis, a sample of muscle tissue was selected from the spinal part of the trout weighing 24 mg. The thermal analysis was started 1 h after the catch. To perform thermal analysis of fish in the heating-cooling process, a synchronous thermal analysis instrument STA 449 F3, Jupter by NETZSCH was used. The device simultaneously captures the Differential Scanning Calorimetry (DSC) curves and the Weight Loss (WL). The analysis of the fish sample was carried out in a copper furnace with the connection of Dewar’s vessel in oxidized aluminum crucibles in helium atmosphere. The accuracy of the temperature measurement was ±0.3°C. A sample of fish (trout) was continuously cooled-heated at a rate of 5 K/min, according to the developed temperature program. The DSC curves show a maximum corresponding to the course of the endothermic process of sample thawing. Melting of the sample water component is observed in a fairly wide temperature range with the presence of large premelting which indicates a high viscosity of the sample. As the number of frozen-thawed cycles increases, the peak area of the DSC curve decreases from 195.9-118.6 kJ/mol, the temperature of the melting peak also decreases, especially between the second and third melting (from 5.12-2.87°C) and the melting interval is shifted to the negative region. The expediency and the development of the DSC temperature program with recommendations for its use have been proved in order to monitor the processing and storage of fish accompanied by phase change of water. For the check samples, it is necessary to fix thermoanalytical curves of successive double freezing-heating in the temperature range from 25-30°C by cooling with nitrogen at a rate of 5 K/min. As a criterion for the thermal state of the trout check sample the exothermic effect of the second freezing serves for the control sample.
A. Mateyeva, R. Uazhanova, I. Saranov, S. Shakhov, B. Kutsova, I. Kuznetsova and I. Glotova, 2017. Justification and Development of the Method for Differentiation of “Frozen-Thawed” Cycles of Fish Based on Differential Scanning Calorimetry. Journal of Engineering and Applied Sciences, 12: 3387-3394.