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The temperature has a significant effect on cathepsin activity, but the effect of temperature on the ripening of marinades, and the formation of protein hydrolysis products, is less studied than other technological factors. The results of this study showed that herring marinated at 2 °C showed a higher mass yield, but lower non-protein nitrogen (NPN), peptides, and free amino acid fraction content, than after marinating at 7 and 12 °C. The higher temperature increased the free amino acid content the most, and decreased the hardness, as measured via sensory assessment, of the marinated meat. This was confirmed by the hardness measurement in the texture profile analysis. The highest activity of cathepsins D and B in the meat was found at 7 °C, while cathepsin L was found at 2 °C. Increasing the temperature by 10 °C increased the diffusion/loss of nitrogenous substances from the meat to the brine by 36%. The meat and brine showed high antioxidant activity, which depended on the marinating temperature, and originated mainly from the 5–10 or 4 kDa peptides in the brine.

Capillary zone electrophoresis (CZE) is a good method for separation of small charged molecules like amino acids and small peptides. However, their identification in biological samples is quite difficult. Proteolysis products in salted fish are usually determined by chemical methods and there is no suitable simple and quick direct instrumental method. In this work the identification of compounds in trichloroacetic extracts from salted herring meat separated by CZE with direct UV detection was performed. There were determined theoretical migration time of amino acids and peptides based on the Offord’s model and experimental migration time of 67 standards. Standards were separated individually, in the mixture and with samples (increasing concentration). On the electrophoregram of salted herring meat extract there were noticed 36 peaks, divided into 4 fields A–D. Among them there were identified in sequence: (A) creatinine, Lys, Arg and His, (B) creatine, (C) Trp, Met, Tyr and Phe and (D) cystine. Described method may be suitable for fast monitoring of the salted herring ripening process.

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 food industry is looking for natural additives to improve acid curd cheese (tvarog), while shrimp by-products are being wasted. The concentrated astaxanthin lipid preparation (ALP) was recovered from shrimp shells and added (0%, 0.25%, 0.5% and 1%) to tvarogs stored up to 4 weeks at 5 ± 1 °C. The addition of ALP increased the lipid content and decreased the moisture in cheese. Water activity, acidity and hardness of tvarogs differed significantly between cheese variants. The cheeses with ALP had more stable and lower pH after 4 weeks of storage, and higher titratable acidity immediately after ALP addition. The 0–0.5% ALP samples had the same level and changes in lipid oxidation, while the 1% ALP cheese had more stable thiobarbituric acid values during storage. This may be due to several times greater antioxidant activity (DPPH assay) in the cheese with the highest ALP addition. The addition of astaxanthin had create popular salmon colour and improved objective colour parameters of the cheeses. The best sensory features had 0.5% ALP sample. A higher addition of astaxanthin preparation caused a foreign aftertaste. The use of astaxanthin from shrimp shells to acid curd cheeses enables the creation of new functional properties that are increasingly popular with consumers.

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.

Brines after herring marinating pose a serious financial problem to the industry and natural environment. Paradoxically, the brine waste containing biological active compounds like proteases and peptides being responsible for marinade quality is discarded with sewage. Results show that the reuse of brine without filtration is not possible because of increase in the bacterial count and lipid oxidation in marinated herring. The desired parameters of marinades were achieved using brine permeate-50 µm free of the suspension and lipids. The best quality and sensory parameters of marinated herring meat were obtained using permeate-0.22 brine, which not contain microorganisms and lipids, and also a high activity of proteases. Reuse of brine allows reducing by half the losses of protein hydrolysis products (PHP) from meat to brine and for reverse diffusion of PHP and peptidases to meat. The marinades produced with the newly-developed method had up to 25% more PHP, up to 20% lower hardness, 10-20% higher activity of proteases, 40-97% lower indices of lipid oxidation, and 5% higher scores in sensory assessment, compared to the marinades produced with fresh brine. The inexpensive and easy to perform microfiltration of brine affords the possibility of increasing the quality and nutritional value of marinades and minimizing both waste volume and production costs.

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...

Summary In the fish industry, brine left after herring marinating is discarded to waste. This study presents laboratory-scale findings regarding recovery of aspartyl (D + E) and cysteine cathepsins (B + L) from waste brine. Ultrafiltration enabled cathepsin recovery from both the soluble and lysosomal fraction of the marinating brine. Retentate 10 kDa had the highest cathepsin activity 140% compared to crude brine. The amount of recovered cathepsins using membranes 30 and 100 kDa was less than 10 kDa, because part of cathepsins passes to permeate. In turn, the salting-out with ammonium sulphate enabled activity recovery of only 80%, but ensured over twofold higher purity of the enzymes than ultrafiltration. The highest precipitation of D + E cathepsins was noted at salt concentration of 40–60%, whereas that of B + L cathepsins at 50–80%. It is recommended to dissolve the salted-out aspartyl cathepsins at pH 4.0 or 8.0, whereas the cysteine ones at pH 5.0. The appropriate selection of parameters enables controlling the aspartyl to cysteine cathepsins ratio in the preparation in the range from 1:2 to 2:1. The new cathepsin preparations showed high activity in a wide range of pH values and ionic strength and can be used in food production.

Background: This study analyzes the effect of salt and acetic acid concentration, time, temperature and fish freezing on the activity and losses of cathepsins during the marinating of Atlantic and Baltic herrings.; Results: The highest contribution to meat general proteolytic activity was found for cathepsin D-like activity. This contribution decreased during the marinating process as a result of, among other things, cathepsin losses to brine. The methods of marinating had a significant impact on cathepsin activity losses. The average ratio of cathepsin D-like activity to L and B in brine accounted for 15:3.5:1.5, respectively. Depending on the method of calculation, cathepsin activity in brine was similar (per gram of tissue/milliliter of brine) or multiply higher (per gram protein in tissue/brine) than in the marinated herring meat. Statistical analysis demonstrated that the extent and structure of cathepsin losses were significantly correlated with the quantitative and qualitative composition of protein hydrolysis products in marinades.; Conclusion: The presented results depict new phenomena of cathepsin losses and explain their impact on the process of fish marinating. Results allow better optimization of the process of meat ripening. The high activity of aspartyl and cysteine cathepsins in brine indicates the real feasibility of their application in the food industry for novel food design. © 2016 Society of Chemical Industry.; © 2016 Society of Chemical Industry.

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.

The content of total volatile basic nitrogen (TVB-N) is highly determined by the variety of raw material, freezing, salt, and acetic acid concentrations, and therefore the effect of these factors on marinated herring quality was determined in this study. A higher TVB-N content was determined in marinades from fillets than from carcasses and from frozen than fresh herrings. An increase in salt concentration from 5 to 15% reduced the content of TVB-N to a greater extent than the increase in acid concentration from 3 to 8%. However, the increase in salt concentration above 11–13% or of acid above 5% in brine did not result in any significant decrease of meat TVB-N value. The brine TVB-N content was significantly correlated with meat TVB-N and was higher than in meat. The best freshness indicators were NH3-N and tyrosine in brine, which can be deemed more universal indicators of the freshness of marinated herring meat. The diffusion from meat to brine was found to significantly decrease the meat TVB-N...

This study investigated the effect of acetic acid concentrations from 3 to 8% on the physicochemical and sensory quality of marinated Atlantic and Baltic herring from fresh and frozen-thawed material. The increased concentration of acetic acid was found to exert a strong impact on decreased sensory scores, weight yield, and pH value as well as on an increased brightness parameter of meat. In turn, moisture, protein hydrolysis products (PHB), total volatile bases (TVB) content, and hardness parameter were affected by the higher addition of acid to a lesser extent. Enhanced protein hydrolysis was observed only at acetic acid concentration of 5% or 5–8%, whereas there was a decrease in the content of TVB only at an acid concentration of up to 4–5%. The marinated frozen-thawed fillets, compared to the fresh ones, required a greater addition of acid in the brine, by 1.5%, to reach a similar pH value. The freezing of fish contributed also to a decrease of PHB and free hydroxyproline, along with an increased con...

Effects of vinegar, oil, and sour cream brines on meat quality of 4 popular cold marinades from herring were investigated in the study. Cover brine type affected the composition and nutritive value of meat as well as the sensory and microbiological quality of marinated herring. Qualitative differences resulted from cover brine penetration into meat, and from diffusion of components from meat to vinegar brine. Compared to oil and sour cream, vinegar brine contributed to increased concentrations of salt and acetic acid, hardness, color brightness of marinades meat and to increased microbial contamination of meat. Furthermore, vinegar caused nitrogen losses to 15%, including valuable products of protein hydrolysis, enzymes, and total volatile bases. The rolling up of fillets reduced diffusion even by 50%. In turn, oil and sour cream were causing mainly a higher fat content and overall sensory evaluation of the marinades.

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.

Marinated and salted fish contain considerable quantities of biologically active substances synthesized during proteolytic ripening of fish tissue. The quantitative and qualitative composition of protein hydrolysis products depend on multiple technological factors. This chapter addresses the impact of key technological factors including: raw material processing, freezing, salt and acid concentration in brine, and type of cover brine on the qualitative and quantitative composition of individual nitrogen fractions in flesh and in brine during marinating and salting of herring. Fish are marinated and salted in a salt/acid solution to which valuable nitrogen fractions are penetrating from flesh. Upon diffusion, a comparable number of nitrogen fractions occur in flesh and in brine. Nitrogen losses from flesh to brine not only evoke deterioration of the quality, yield, and nutritive value of a food product but are also a source of contamination to the environment.

Effects of vinegar, oil, and sour cream brines on meat quality of 4 popular cold marinades from herring were investigated in the study. Cover brine type affected the composition and nutritive value of meat as well as the sensory and microbiological quality of marinated herring. Qualitative differences resulted from cover brine penetration into meat, and from diffusion of components from meat to vinegar brine. Compared to oil and sour cream, vinegar brine contributed to increased concentrations of salt and acetic acid, hardness, color brightness of marinades meat and to increased microbial contamination of meat. Furthermore, vinegar caused nitrogen losses to 15%, including valuable products of protein hydrolysis, enzymes, and total volatile bases. The rolling up of fillets reduced diffusion even by 50%. In turn, oil and sour cream were causing mainly a higher fat content and overall sensory evaluation of the marinades.

Fish meat is characterized by a high content of valuable nutrients. During the marinating process, however, the process of proteins diffusion and other nitrogen fractions from fish to the surrounding brine is commonly observed. It was determined that the total nitrogen loss from herring meat of industrial maturity (4-5day) amounted to 6-19% of raw material nitrogen. Extension of the marinating time to 16-18days increases nitrogen losses even to 18-27%. Less loss was observed during marinating of fresh than of frozen herring and during marinating of carcasses, as opposite to fillets. Higher nitrogen content in fish was not proved to influence higher nitrogen losses in a brine. The majority of loss consisted of nitrogen fractions soluble in TCA, of which one third was formed by α-amine nitrogen. Nitrogen contained in brine suspension accounted for only 1.5-4% of total nitrogen losses. With increasing salt or acid concentration the amount of total nitrogen loss was lower from fresh herring and higher from frozen one. Higher salt concentration significantly reduced the amount of non-protein nitrogen and all its fractions during marinating of fresh and frozen herring. In case of acetic acid, the influence of its concentration was diverse and depended on type of herring and its dressing.

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.