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Protein hydrolysates were prepared from mechanically separated seal meat (MSSM) using commercially available microbial enzymes Alcalase and Neutrase. The enzyme in each case was inactivated by acidification with 4 N HC1 to pH 4.0. Heme groups were removed, and the hydrolyzed proteins were bleached with charcoal, neutralized to pH 7.0, and dehydrated. The yield of hydrolysate (YH) and the degree of hydrolysis (DH) using Alcalase, under optimum conditions, were 92.75% and 19.5%, respectively. The YH for Neutrase-assisted hydrolysis of MSSM was 72.85%. The dehydrated seal protein hydrolysate (SPH) contained 77.3% crude proteins, 0.74% lipid, and 20.67% minerals, mainly sodium chloride. The amino acid composition of SPH was similar to that of the original MSSM. The product so obtained was bland in taste and off-white in appearance (Hunter L value of 84.6) and had a solubility of >93.5% over the pH range 2.5-10.4.

The technological properties of raw fish are influenced by the changes in protein structure under heating, which determines the texture and quality of the product. The aim of the study was to examine the protein denaturation temperature and the rheological properties of Baltic herring muscle tissue. The thermal properties were determined by the differential scanning calorimetry (DSC) method and the rheological properties were determined using dynamic oscillatory tests. DSC showed four peaks associated with denaturing transformations of myosin (39.59 °C), sarcoplasm (51.67 °C), connective tissue (63.16 °C), and actin (74.40 °C). Analysis showed that not all transformations occurred according to the same kinetic model. The first two and the last peak are described by 1st order kinetics, while peak 3 is described by 2nd order kinetics. Correlating the changes in fish tissue structure during heating with the rheological characteristics provides more information. The obtained kinetics models correlated very strongly with the results of model testing. Rheological changes of the G’ and G” values had two inflexion points and demonstrate a high degree of convergence with the DSC changes of herring muscle tissue from 20 to 85 °C.

The aim of the study was to use 3 monocultures of Bifidobacterium (Bifidobacterium animalis ssp. lactis AD600, Bifidobacterium animalis ssp. lactis BB-12, and Bifidobacterium longum AD50) in fermented goat milk to assess the microbial, physicochemical, rheological, and sensory quality of beverages during a 3-wk storage period at 5°C. The results indicated that selected bifidobacteria may be used for production of fermented goat milk because they comply with the minimum standards specified by the Food and Agriculture Organization of the United Nations and the World Health Organization during the entire period of storage. However, goat milk fermented by Bif. longum AD50 had less than 10 cfu/g after 21 d of storage. The acidity, acetaldehyde content, viscosity, and hardness of fermented goat milk beverages depended on the strain and the storage period. Sensory properties were similar and acceptable, with a tendency for the quality to be reduced with an extended storage time. Depending on the monoculture of bifidobacteria used to manufacture fermented goat milk, the product had a different pH value. Titratable acidity in all fermented goat milk increased significantly along with the time of storage. Our study has shown that monocultures of bifidobacteria had a significant effect on the content of acetaldehyde, but the lowest effect over the entire storage period was observed in goat milk fermented by Bif. animalis ssp. lactis BB-12. This sample also had the lowest viscosity values compared with other samples and the best organoleptic properties during a 3-wk storage period.