Application of a crude digestive proteases preparation to improve the ripening of marinated fillets from low-technological value Baltic herring (Clupea harengus membras L.).

BACKGROUND: As a result of climate change (reduced the oxygen content and food available in the waters) and overfishing, ever larger batches of the herring catch are classified as low-value fish and used for feedstuff or canned food production. Fast and complete ripening of marinated fillets, especially from low-value Baltic herring, poses a problem because of the low muscle protease activity and changes in muscle tissue proteins. RESULTS: For the first time, a crude digestive proteases preparation (CDPP) was obtained from herring viscera using a two-stage method consisting of ethanol extraction and then salt precipitation. CDPP had a reduced hemoglobin content, with optimum activity at pH 7.5-8.8 or 60-120 g kg-1 NaCl. At pH 4-5, it still exhibited 24-68% of proteolytic activity. CDPP was used for 4-24 h of brining of fresh and frozen-thawed fillets or injection of fresh fillets before marinating. CDPP-brining increased especially cathepsin D and carboxypeptidase A activities, whereas it decreased cathepsin B and L activities in the marinades. CDPP-brining mitigated the negative effect of freezing-thawing on mass-yield, protease activity, protein hydrolysis, texture profile, colour and sensory quality of the marinated fillets. CDPP-injection was found to be the best method because it increased mass-yield and ripeness of the marinated fillets to a greater extent than CDPP-brining did. The marinades from the CDPP-treated fillets had no bitter taste as a result of the presence of hemoglobin or chymotrypsin, and there were no results indicating lipid oxidation. CONCLUSION: The application of CDPP in marinating technology is a viable approach to enable the use of low-value herring in food production, shorten the marinating time, and improve the ripeness and sensory quality of meat. © 2024 Society of Chemical Industry.

Use of Rapid Capillary Zone Electrophoresis to Determine Amino Acids Indicators of Herring Ripening during Salting.

Currently, herring fillets are salted with acetic acid to activate muscle proteases. This causes a change in the composition of free amino acids, compared to salting of whole fish with viscera proteases. Therefore, old indicators of the ripening dynamics of salted fish based on amino acids are not current. Determination of free amino acids can be performed by many methods, but most are labor intensive and expensive. Therefore, a capillary electrophoresis method without derivatization (CZE) was used to determine the actual ripening rates of salted herring fillets. A group of hydrophobic and basic amino acids were determined in trichloroacetic acid (TCA) extracts of meat and brine to develop 16 indicators. Statistical regression analysis of the indicators (R2adj, RMSE, cluster analysis) followed by principal component analysis (PCA) correlation analysis of the indicators vs sensory evaluation parameters of texture and TPA-hardness of salted fillet meat allowed the choice of the most precise indicators. The best indicator in meat was Phe/Tyr-height, which value increased during salting. A more precise indicator of ripening was His/Tyr-height in brine, which value decreased during salting. Sensory evaluation parameters of salted herring texture correlated strongly with TPA-hardness and traditional indicators such as non-protein nitrogen and protein hydrolysis product fraction content. However, the most precise indicators were those obtained from amino acids determined by the CZE method. Results obtained in this study may be suitable for fast monitoring of the salted herring ripening process in industry.

Effect of Protein Denaturation Temperature on Rheological Properties of Baltic Herring (Clupea harengus membras) Muscle Tissue.

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.

Development of Functional Acid Curd Cheese (Tvarog) with Antioxidant Activity Containing Astaxanthin from Shrimp Shells Preliminary Experiment.

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.

Prevalence of Listeria species and L. monocytogenes in ready-to-eat foods in the West Pomeranian region of Poland: Correlations between the contamination level, serogroups, ingredients, and producers.

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.

Characteristics of herring marinated in reused brines after microfiltration.

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.

Effect of technological factors on the activity and losses of cathepsins B, D and L during the marinating of Atlantic and Baltic herrings.

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.

Distribution of Cathepsin D Activity between Lysosomes and a Soluble Fraction of Marinating Brine.

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.

Occurrence of aspartyl proteases in brine after herring marinating.

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.

Anthropogenic impact on the presence of L. monocytogenes in soil, fruits, and vegetables.

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.

Effect of cover brine type on the quality of meat from herring marinades.

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.

Losses of nitrogen fractions from herring to brine during marinating.

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.

Comparison of physicochemical and sensory changes in fresh and frozen herring (Clupea harrengus L.) during marinating.

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.