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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.

Poland is one of the largest food producers in Europe, and the West Pomeranian region of Poland is a large producer of RTE food. Thus, the objective of this study was to determine the prevalence of Listeria sp. and L. monocytogenes (LM) in RTE foods manufactured by 13 selected Polish food producers whose processing plants are located in this region. In total, 650 samples of RTE foods, and 263 ingredients of salads and desserts were analyzed. Almost 18% of the RTE foods failed to meet the zero tolerance limit for Listeria, which means they should not be allowed for retail. LM was isolated from 13.5% of the samples, with counts of 10–100 CFU/g noted in half of them. Products with meat and dairy ingredients, and fish products, sandwiches, sprouts and sushi, were at the highest statistically significant risk of LM contamination. Four serogroups were identified among the LM isolated from RTE foods, of which the 4b-4d-4e serogroup was predominating. The samples most heavily contaminated with LM contained even 2 serogroups. Results were subjected to the cluster analysis and principal component analysis to determine correlations between food groups, food ingredients, producers, contamination level, and serogroups of LM.

Cold marinades are produced mainly from the Clupeidae fish, because meat of other fish species does not reach a desired level of ripeness in the acid‐salt environment of fresh brine. Hence, this work presents an innovative idea of reusing brine including cathepsins and peptides for marinating cod, salmon, trout, and carp. The extent of marinades ripening improvement depended on fish resistance to the marinating process. The reused brine proved best in improving the ripening of fatty fish (salmon and trout), which were qualified to the first class of resistance to marinating. In the case of cod, the reuse of brine did not elicit a satisfactory improvement in meat ripening. Therefore cod was qualified to the second class of resistance. The reuse of brine resulted in decreased values of lipid oxidation indices (except for cod) and meat hardness, and in increased scores for overall sensory evaluation and total volatile bases nitrogen value.

This study was conducted on fresh and frozen-thawed sprat of the lowest utility, which is not used for consumption. The peptidase activity was measured (i) against acid- and base-hemoglobin (GPA) a...

This paper is the first ever to describe the phenomenon of bimodal distribution of cathepsin D in the lysosomal and soluble fractions of brine left after herring marinating. Up to 2 times higher cathepsin D activity was observed in the lysosome fraction. Activity of cathepsin D in brine increased according to the logarithmic function during low frequency-high power ultrasounds treatment or according to the linear function after multiple freezing-thawing of brine. Activity enhancement was achieved only in the brine devoid of lipids and suspension. Study results show also that measurement of lysosomal cathepsin D activity in the marinating brine requires also determining cathepsin E activity. Decreasing pore size of microfilter from 2.7 to 0.3 μm significantly reduced the lysosome content in the brine. The presence of lysosomes and the possibility of their separation as well as the likely release of cathepsins shall be considered during industrial application of the marinating brine, as new cathepsins preparations in fish and meat technology.

The production of cold fish marinades is characterized by high seasonality, and therefore producers have problems with providing the sufficient supply of marinades. Besides, after the spawning season, herrings do not ripen properly. Therefore, in the present study, marinated Atlantic and Baltic herring fillets were frozen and stored for 2 days up to 5 months using constant and fluctuating temperatures (recrystallization). The freezing-thawing of marinades improves the hardness, color, and overall sensory evaluation of meat. Temperature fluctuations increase the disintegration of the muscle tissue structure and lysosomal membranes, enhancing the activity of aspartyl endopeptidase responsible for improving the texture of meat and increasing the concentration of protein-hydrolyzing products. The highest thaw drip loss and lipid oxidation were observed after 3 months of frozen storage with temperature fluctuation. Frozen storage had a different effect on fatty and thin herrings. Frozen-thawed marinades stored for up to 5 months were of good microbiology quality. Study results show that the freezing of the semi-marinades may be one of the methods for quality improvement and for extending marinades shelf-life before the seasonally increased demand on the market.

Summary Salt concentrations of brine above 10% are still commonly used in fish marinating process. The study has showed an increasing salt concentrations affect to adversely all the properties of marinated herring meat. Increase in salt concentration from 5% to 15% resulted in significantly (P

Herrings are marinated in a brine consisting of salt and acetic acid. During marinating, various nitrogen fractions diffuse from fish flesh to the brine, causing significant nutritional quality losses of the raw material. In this study, it has been demonstrated for the first time that proteases diffuse from the fish to the marinating brine. Using ammonium sulphate precipitation and affinity chromatography on pepstatin-A agarose bed the aspartyl proteases were purified and concentrated over 2600-fold from a marinating brine. Pepstatin-A completely inhibited the activity of the purified preparation. The preparation was active against fluorogenic substrates specific for cathepsin D and E and inactive against substrates specific for cysteine cathepsins. Depending on incubation time, the preparation showed pH-optimum at 2.0 or 4.5. The 2D SDS–PAGE separation demonstrated the presence of a few proteins with molecular weights and pI values typical of cathepsin D, E and pepsin.

BACKGROUND: The influence of freezing on the changes during ripening is better described for salted fish than marinades. Therefore in the present study the effect of preliminary freezing of raw material on the ripening of carcasses and fillets marinated during 18 days at a temperature of 10 °C, in brine with 6% salt and 5% acetic acid was examined. RESULTS: In both cases the marinating of thawed frozen material resulted in larger mass losses and decrease of the value of meat colour parameters. The semi-marinades from raw herring were characterised by higher values of total estimation based on sensory analysis. The statistical analysis showed weak correlation between the discriminants of sensory assessment and the studied physicochemical parameters of semi-marinades. CONCLUSIONS: These results suggest that the semi-marinades from raw fish are characterised by higher sensory quality, better colour parameters and higher yield than those from frozen thawed fish. Copyright © 2010 Society of Chemical Industry

The aim of this study was to determine the prevalence of Listeria sp. and Listeria monocytogenes in soil samples with reference to type of fertilizers (natural and artificial) and distance from places intensively exploited by men, as well as to determine the relationship between the presence of L. monocytogenes in the soil and in fruits and vegetables. The examined 1,000 soil samples originated from 15 different areas, whilst 140 samples of fruits and 210 samples of vegetables were collected from those areas. L. monocytogenes was isolated only from 5.5 % of all soil samples coming exclusively from meadows intensively grazed by cattle (27.8 %) and areas near food processing plants (25 %) and wild animal forests (24 %). Listeria sp. and L. monocytogenes were not present on artificially fertilized areas and wastelands. L. monocytogenes was detected in 10 % of samples of strawberry, 15 % of potato samples, and 5 % of parsley samples. Our data indicate that Listeria spp. and particularly L. monocytogenes were found in the soil from (1) arable lands fertilized with manure, (2) pasture (the land fertilized with feces of domestic animals), and (3) forests (again, the land fertilized with feces of animals, not domestic but wild). The bacteria were not detected in the soil samples collected at (1) artificially fertilized arable lands and (2) wastelands (the lands that were not fertilized with manure or animal feces). Moreover, a correlation was determined in the presence of L. monocytogenes between soil samples and samples of the examined fruits and vegetables.