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The aim of this study was to investigate endogenous proteolytic activities in a cod product and their impact on muscle proteins and textural properties during fermentation and storage. The result of specific proteolytic activities showed that cathepsins, especially cathepsin B, had the highest activities during fermentation and storage. SDS–PAGE indicated more degradation of myofibrillar proteins by cathepsin L than other proteases and that the hydrolysis by cathepsins was pronounced in the last stage of fermentation. Texture analysis showed that cathepsins had a negative impact on gel strength and this impact increased in the last stage of fermentation. However the product still had a firm texture. During storage (4 °C) for one week, no significant changes were seen in the gel strength. In conclusion, cathepsins had more impact on muscle proteins and textural properties than other proteases during fermentation but had little impact on gel strength during storage at 4 °C. [ABSTRACT FROM AUTHOR]

Abstract: Farmed cod (Gadus morhua) fillets were subjected to a temperature abuse, which caused changes in muscle pH, textural properties and proteolytic pattern early in the post mortem storage period. The temperature abused fillets were less resilient and had lower values of gumminess than those subjected to iced storage throughout the storage period. In addition, the abused fillets were somewhat less cohesive, and had a higher content of small peptides than the iced fillets. From the proteolytic profiles, it is suggested that the textural changes observed after temperature abuse may have been caused by collagenase-like enzymes. [Copyright &y& Elsevier]

Abstract: An average production of 10,000kg cod fillets (gadiform species) will generate by-products with more than 1000kg marine lipids. More than 30% of these lipids are the health beneficial n-3 fatty acids, which have commercial value. To increase the industrial utilization of these lipids different sources of raw material need to be evaluated in respect to available amounts and chemical composition. The present work presents such data on four gadiform species caught in the Barents Sea (Gadus morhua (cod), Pollachius virens (saithe), Melanogrammus aeglefinus (haddock) and Brosme brosme (tusk)) evaluated at three seasons during 1 year. Both seasonal and inter-species differences were found in the amount of by-products and the lipid composition. The levels of polyunsaturated fatty acids were significantly higher in haddock liver and significantly lower in tusk liver compared to saithe and cod. However, regardless of the variations found, the lipids from all samples analysed contained significant quantities of health beneficial fatty acids. Liver was the best lipid source containing between 43 and 69% total lipids. The viscera contained between 2 and 9% lipids and trimmings contained approximately 1% lipids. While the lipids from liver generally contained more than 90% triacylglycerols, the lipids from the other by-products contained higher levels of phospholipids making up more than 60% of the total lipids in muscle and gonads. [Copyright &y& Elsevier]

Abstract: The main products of hydrolysis of fish by-products are hydrolysed protein and oil. The aim of this work was to study the effect of initial heat inactivation of endogenous enzymes, addition of water prior to hydrolysis, use of different commercial enzymes and combination of enzymes on the yield and purity of the protein and oil fractions after enzymatic hydrolysis of cod by-products. This study was designed to examine how all these factors were effective for destroying protein–lipid complexes in order to obtain pure oil and protein fractions and reduce the insoluble fraction. Initial heating of raw material changed both raw material properties and inactivated endogenous enzymes thereby influencing the following hydrolysis. High amount of lipids in raw material combined with initial heating caused formation of protein–lipid complexes which was found in all protein containing fractions. The main constituents of the lipids in the complexes were phospholipids and other polar lipids. Insoluble protein–lipid complexes formed lead to increased amount of sludge, reduced FPH yield and high amount of lipids in FPH. The highest amount of separated oil was obtained in the experiments after initial heating without added water. These treatments also reduce amount of emulsion, which is not a desirable product after hydrolysis. Initial heating caused denaturation of protein, which decreased their emulsifying properties. Results showed that it is not possible to obtain all desirable quality indicators such as: maximum oil and FPH yield, minimum emulsion and sludge yield and the highest protein recovery in FPH with the lowest amount of lipids in FPH fraction by using only one hydrolysis process. Therefore, the aim and requirements for the final products should be prioritised and defined very clearly before the process is designed taking into account the composition of raw material. Hydrolysis of unheated raw material with Alcalase and addition of water was the best compromise taking into account the mentioned quality indicators. [Copyright &y& Elsevier]

Endogenous salmon enzymes and their impact on muscle proteins and texture were studied. To reduce interfering effects of microbial enzymes, the fish were irradiated. Irradiation of salmon fillets resulted in severe inhibition of cathepsin B-like and collagenase-like enzymes. The effect was most pronounced for the cathepsins. The textural properties and amounts of free amino acids and extractable proteins in the irradiated fillets and control group were different after 14 days of iced storage. Even with the increased load of microorganisms seen in the control group, no severe deterioration of fish texture or increase in proteolytic activity was observed during the storage period. It therefore seems that microorganisms are not important for changes in salmon texture. [Copyright &y& Elsevier]

• Protein carbonyls were labelled by coumarin-hydrazide (CHH) dye. • Fluorescence microscopy allowed analyzing carbonylation in both soluble and insoluble proteins. • CHH specificity towards protein-bound carbonyls was validated. • ELISA and CHH-labelling fluorescence assay were compared. Muscle foods, particularly fish products are highly exposed to oxidative stress during processing and storage, resulting in oxidative modification of proteins. Protein carbonyls content has been used as one of the measures of oxidative stress. Generally, the resulting carbonylated proteins (CPs) have so far been labeled with 2,4-dinitrophenyl (DNP) hydrazine and detected with anti-DNP antibody. However, the applicability of this method to food samples is limited by its high price, time-consuming procedure and possibility to perform the measurements just on soluble protein fractions. We developed a simpler, faster and cheaper method to assess CP level in muscle foods, including both soluble and insoluble protein fractions, which is based on a direct reaction of protein carbonyls with 7-(diethylamino)coumarin-3-carbohydrazide (CHH). The paper describes a novel technique to label both soluble and insoluble carbonylated proteins with CHH and determine carbonyl content by fluorescence microscopy assay which correlates (R = 0.911) with conventional ELISA method. [ABSTRACT FROM AUTHOR]

The demand for tasty, convenient, fresh seafood products is continually increasing. This stresses the need for processing methods that can prolong the otherwise short shelf life of seafood. A well-studied method is the use of modified atmosphere packing. However, research into the use of modified atmosphere packaging for seafood with varying lipid composition is limited. Thus, in this experiment the effect of lipid profile, storage temperature, and the gas composition of the modified atmosphere on the solubility of CO 2 in a seafood model product was investigated. The temperature dependent Henry’s constants for the various compositions showed that the physical state of the lipids clearly influenced the solubility of CO 2 in the model products, with liquid fat leading to a similar solubility of CO 2 as water, while CO 2 only being minimally dissolved in solid fats. [ABSTRACT FROM AUTHOR]

Highlights: [•] Influence of authentic human gastric juice on oxidation of marine lipids is evaluated. [•] Marine lipids in emulsion and liposomes oxidised during a modelled digestion period. [•] No difference was found between oxidation in an authentic gastric juice and a hydrochloric acid solution. [•] Gastric juice inhibited pro-oxidative activity of dietary iron ions, but not met-hemoglobin. [•] Beverages may both positively and negatively affect post-prandial oxidation of marine lipids. [Copyright &y& Elsevier]

As part of an extended fish product (mixed salmon spread) value chain involving multiple treatment procedures and mixing processes, oxidation and microbial spoilage can be initiated at any number of steps and go on to accelerate product deterioration. This may occur, for example, when salmon rest raw materials are processed to form mixed emulsion products. To investigate the effect of selected variables in the value chain, a model experiment was designed and implemented, consisting of a chain divided into four steps involving fish feed composition, fish processing, fish spread production and storage. By using this case, the objectives of the paper are to 1) show how a complex split-plot design can be analysed using analysis of variance (ANOVA) and multivariate statistical analyses, 2) show how an interplay of the methodologies can contribute to improvement in the interpretation and validation of results, and 3) identify the quality markers most affected by the design variables, and then use these to optimise response measurements for different raw material properties. We also propose some new monitoring and control strategies based on the PCA and results obtained. The analysis has indicated in this case that it may be beneficial for the long shelf-life of the spread to use fresh and lean salmon cuts, to store the product under superchilled conditions and to avoid the addition of secondary seafood ingredients. Salmon feed variables do not affect the eating quality of the spreads. The early addition of a smoke component and the rigor status of the salmon at the time of processing had little effect on eating quality. The variables that did not affect eating quality or shelf-life can be optimised based on aspects such as nutritional or health benefits, or production costs. This article demonstrates that PCA is a useful method both for the monitoring of eating quality with storage time, the definition of control limits for product acceptability, and the statistical validation of split-plot ANOVA results. • Identification of significant variables along the mixed salmon spread value chain. • Inability to predict eating quality using measurements taken early in the value chain. • PCA identified as a useful tool for monitoring eating quality development. • PCA identified as a useful tool for validating split-plot ANOVA results. [ABSTRACT FROM AUTHOR]

Abstract: The objectives of this work were to compare ice crystal sizes of pre-rigor Atlantic salmon fillets subjected to two processes of superchilling and to assess the size changes during storage of superchilled samples at −1.7 ± 0.3 C. The fillets were superchilled in an impingement freezer at either a slow rate (−20 °C, 153 W/m2 K, 4.2 min) which is referred to as process S or a fast rate (−30 °C, 227 W/m2 K, 2.1 min) which is referred to as process F before storage for 29 days. Significantly smaller (p < 0.05) equivalent diameters of ice crystal occurred at faster superchilling rate when compared to slower superchilling rate. The influence of these processes on the microstructure of pre rigor salmon fillets was studied. The equivalent diameter of the intracellular ice crystals formed were 60 ± 5 and 23 ± 1 μm for the samples subjected to processes S and F, respectively. Significant differences were observed between the size of ice crystals formed during the superchilling process and during storage of superchilled samples. The formation of ice crystals within salmon muscle regardless of the superchilling rates was an important factor in reducing cell structure damage. [Copyright &y& Elsevier]

Abstract: Food preservation is very important for the safety and the reliability of the product. Superchilling as used for preserving foods, has been defined as a process by which the temperature of a food product is lowered to 1–2°C below the initial freezing point. Fresh and high quality food products are in great demand worldwide. Temperature is a major factor determining the shelf life and quality of food products. Fish and meat are perishable food commodities, where better and more advanced preservation technology is needed. Deterioration of these foods mainly occurs as a result of chemical, enzymatic and bacteriological activities leading to loss of quality and subsequent spoilage. Storing food at superchilling temperature has three distinct advantages: maintaining food freshness, retaining high food quality and suppressing growth of harmful microbes. It can reduce the use of freezing/thawing for production and thereby increase yield, reduce energy, labour and transport costs. The study on the growth mechanism of ice crystals, modelling and computer simulation of foods during superchilling and superchilling storage is needed. [Copyright &y& Elsevier]

Abstract: Low field Nuclear Magnetic Resonance (LF-NMR) relaxation time measurements were used to evaluate the effect of different pre-salting methods (brine injection of salt and/or phosphates followed by brining, solely brining, pickling and kench salting) on the protein denaturation and change in muscle properties during the production steps of dry salted cod fillets followed by rehydration. The NMR relaxation curves were affected by the salting method and represented well the structural differences between the salting methods at each processing step. Significant correlations were observed between the NMR relaxation parameters and all physicochemical quality properties measured, except the cooking yield, when samples from all processing stages were analyzed together. The longitudinal relaxation time T 1, and the faster relaxing transverse relaxation time T 21 were shown to be especially sensitive to protein denaturation in the fillets. The water distribution indicated that the salting and rehydration processes changed the cells irreversibly. The study indicated that pre-brining by brine injection followed by brining, with low salt concentrations, led to the least protein denaturation during the dry salting and rehydration process. [ABSTRACT FROM AUTHOR]

Abstract: The objective of the current study was to analyze and develop some important automation steps in a superchilling process line. In order to control the product quality there is a need for online measurements of ice fraction and distribution in inhomogeneous products. Moreover, automatic handling of such superchilled products is currently commercially unavailable. The current study presents a new method for monitoring and handling superchilled product of varying form and consistency. Observation of the shift in the water absorption peak, measured by near-infrared spectroscopy (NIR) transflection mode, was used to determine the ice level in superchilled salmon, scanning approximately 1.5cm into the fillets. The salmon fillets were stored on ice at 0°C for 5–7days before superchilling at −24°C to target ice contents of 10%, 15% and 30%. Online NIR measurements of ice fraction showed promising results, with a low prediction error of 2.5%. The storage study confirmed former quality results with a microbiological shelf life of 15–17days with only minor differences in values for drip loss and water-holding capacity between superchilled and chilled samples. [Copyright &y& Elsevier]

The aim of this study was to assess lipid oxidation development in sous-vide cooked Atlantic mackerel during chilled storage by fluorescence microscopy coupled with chemical, physical and data analysis methods. Sous vide-cooking at 70 °C and 80 °C for 10 and 20 min was performed with and without use of antioxidants. Fluorescence micrographs of lipids extracted from the fish samples on 1st, 3rd, 7th, and 9th day of chilled storage at 4 ± 1 °C, were acquired in the wavelength region of λex 475/40 and λem 530/50 (44 FITC filter). The obtained images were numerically processed and the resulting data correlated with 2-thiobarbituric acid reactive substances (TBARS) determined by conventional chemical method of lipid oxidation analyses. Total lipid content and color characteristics of mackerel fillets were analyzed as well. The yellowness of the fish flesh significantly correlated (p < 0.05, R = 0.859) with conjugated trienes generated from thermal polymerization of lipids during chilled storage of sous-vide cooked mackerel. Results showed that higher temperature and cooking times generally accelerated lipid oxidation in mackerel samples prepared both with and without addition of antioxidants in terms of conjugated trienes and tetraenes. However, the addition of antioxidants enhanced the lipid oxidation stability of cooked mackerel fillets. • Fluorescence correlated with 2-thiobarbituric acid reactive substances. • Yellowness of the fish flesh correlated with conjugated tetraenes. • Conjugated structures increased with increased cooking temperature and time. • Antioxidants enhanced lipid oxidation stability of cooked mackerel fillets. [ABSTRACT FROM AUTHOR]

The aim of this study was to investigate the potential of fluorescence microscopy coupled with chemical, physical and data analysis methods for reliable and non-invasive detection of changes in texture parameters of sous-vide cooked Atlantic mackerel during chilled storage. Fluorescence micrographs of cook loss and connective tissue of the fish samples after sous-vide treatment at 60 °C and 75 °C for 10, 15 and 20 min taken in the 1st, 3rd and 7th day of chilled storage were acquired. The obtained images were numerically processed and the resulting data was directly correlated (R = 0.960) with the total collagen content determined by a chemical method. Partial least squares analysis was applied to derive statistically significant regression models revealing the influence of each of sous-vide regime parameters on changes in total collagen content and texture parameters of Atlantic mackerel during chilled storage. Results showed that both collagen integrity and firmness of mackerel flesh were significantly (p < 0.05) affected by the temperature of sous-vide treatment and duration of chilled storage, leading to gradual softening of the fish tissue due to degradation of collagenous tissue. [ABSTRACT FROM AUTHOR]

[Display omitted] • G. sulphuraria cultivation occurred in a medium made from fish processing streams. • Proteolytic treatment of rainbow trout residues resulted in a superior nitrogen source. • In a non-sterile fed-batch culture a biomass concentration of 80 g L−1 was achieved. • Produced biomass did show littles microbial contaminants. The study aimed at zero-waste utilization of fish processing streams for cultivation of microalgae Galdieria sulphuraria. Wastewater from a fish processing facility, slam (mix of used fish feed and faeces), and dried pellet (sediments after enzymatic hydrolysis of rainbow trout) were investigated as potential sources of carbon, nitrogen, and phosphate for cultivation of G. sulphuraria. The pellet extract was found to support the growth of G. sulphuraria when appropriate diluted, at concentrations below 40 % (v/v). It was revealed that wastewater does not impact the growth negatively, however free amino nitrogen and carbon sources need to be supplied from another source. Therefore, only proteolyzed pellet extract (20 %, v/v) was selected for upscaling and a biomass concentration of 80 g L−1 (growth rate was 0.72 day−1) was achieved in a non-sterile fed-batch culture. Even though biomass was produced under non-sterile conditions no pathogens such as Salmonella sp. could be detected. [ABSTRACT FROM AUTHOR]

High resolution NMR technique has been used to monitor post-mortem changes in salmon ( Salmo salar ) fillets upon storage at 4 and 0 °C. Thirty-one different fish metabolites influencing freshness and taste properties have been unequivocally assigned by NMR using either available standard compounds or ad hoc acquired 2D 1 H– 1 H TOCSY and 1 H– 13 С HSQC spectra. The monitored fish metabolites include amino acids, dipeptides, sugars, vitamins, biogenic amines, as well as different products of the ATP degradation. The detection and monitoring of biogenic amines by NMR, upon fish storage, is information of interest for consumers, since some of these compounds are toxic. The data from this study shows that NMR spectroscopy also provides the amount of all metabolites necessary for the calculation of the K -index used to express fish freshness. A good correlation was found between the K -index increase and the formation of the undesired biogenic amines. The metabolite concentrations and the K -index found in this work were compared and found coherent with literature data. The performed study reveals the strengths and the suitability of the NMR approach to monitor different biochemical processes occurring during fish storage and qualitatively and quantitatively characterise fish metabolites determining fish quality. [ABSTRACT FROM AUTHOR]

Abstract: Farmed Atlantic cod were subjected to a combination of stressors in a holding tank before being killed, pre rigor filleted and stored in ice. At slaughter, a higher level of stress was confirmed by blood physiology analyses. This was further associated with significantly reduced muscle pH and somewhat elevated muscle collagenase-like activity in the stressed fish, whereas no differences in cathepsin-like activities were found. After 5days of iced storage, the stressed fish had significantly lower water holding capacity, reduced hardness and yellowish colour compared to the control group, and no differences in the other parameters investigated. Independent of pre-slaughter stress, the activities of cathepsin B- and B/L-like enzymes increased and activities of cathepsin D/E- and collagenase-like enzymes decreased with storage. [Copyright &y& Elsevier]

Abstract: Calanus finmarchicus is a marine zooplankton of interest for the aquaculture industry, as well as for nutraceuticals and the cosmetic industry. The chemical composition of C. finmarchicus rapidly changes postmortem due to autolytic processes; in particular phospholipids rapidly degrade to give free fatty acids. The aim of this study was to inactivate autolytic enzymes in C. finmarchicus by applying heat (72°C, 5–30min) through mixing with boiling, fresh water, and further to explore the effects of heat (70°C, 15min) combined with long time storage (−20°C, 12months) of treated and untreated material. Heat treatment (5min) inactivated all tested enzymes and maintained the initial amount of phospholipids, total lipids and crude protein. Storage of untreated material led to complete degradation of all phospholipids, whereas heat treatment resulted in a stable product containing the initial amount of phospholipids and astaxanthin. [Copyright &y& Elsevier]

Abstract: Caffeic acid, a hydroxycinnamic acid common in different vegetable sources, has been employed as a natural antioxidant for inhibiting oxidation of fish lipids present in different food matrices. The aim of this review is to discuss the mechanisms involved in the antioxidative and prooxidative effects of caffeic acid found in different model systems containing fish lipids. These model systems include bulk fish oils, liposomes from cod roe phospholipids, fish oil emulsions, washed cod mince, regular horse mackerel mince and a fish oil fortified fitness bar. The data reported show that the antioxidant activity depends on the physical state of the lipids and the composition of the intrinsic matrix in which they are situated. Caffeic acid significantly prevented rancidity in both unwashed and washed fish mince, the latter which was fortified with haemoglobin. In the unwashed mince, the activity was however clearly dependent on the lipid to antioxidant ratio. In these systems, an important redox cycle between caffeic acid and the endogenous reducing agents ascorbic acid and tocopherol were further thought to play an important role for the protective effects. The effect of caffeic acid was also highly dependent on the storage temperature, showing higher effectiveness above than below 0°C. Caffeic acid was not able to inhibit oxidation of bulk fish oils, fish oil in water emulsions and the fish-oil enriched fitness bar. In the liposome system, caffeic acid inhibited haemoglobin (Hb)-promoted oxidation but strongly mediated Fe2+ mediated oxidation. In conclusion, caffeic acid can significantly prevent Hb-mediated oxidation in fish muscle foods but its activity in food emulsions and liposomes is highly dependent on the pH, the emulsifier used and the prooxidants present. [Copyright &y& Elsevier]

Abstract: Low field Nuclear Magnetic Resonance was used to evaluate the effect of salt and modified atmosphere packaging (MAP) on cod loins during superchilled storage. Transversal and longitudinal proton relaxation times of the cod loins were measured with Carr–Purcell–Meiboom–Gill (CPMG) and Inversion Recovery (IR) pulse sequences respectively. The relaxation parameters reflected the observed differences in the muscle caused by variation in salt concentration, the choice of salting method (brining or brine injection) and packaging (air or MAP), as well as superchilled storage temperature and storage time. Significant correlations were found between the NMR parameters and parameters describing the water dynamics of the muscle (moisture and salt content, water holding capacity, drip and cooking yield), as well as muscle pH and counts of H2S-producing bacteria in chosen sample groups. The study showed the possibility of using low field NMR to indicate fish quality deterioration, when the spoilage mechanisms affect the water properties and muscle structure. [ABSTRACT FROM AUTHOR]

Abstract: Fish protein hydrolysates (FPH) have good and well documented functional properties. Peptides obtained from various fish protein hydrolysates have also shown bioactive and antioxidative activities. The aim of this study was to evaluate how storage and preparation of cod (Gadus morhua) backbones influence the yield, functionality, bioactivity (CGRP and gastrin/CCK related molecules) and antioxidative properties of fish protein hydrolysates. A series of hydrolysis trials have been carried out using backbones from cod that were initially fresh or frozen and further hydrolysed for different times (10, 25, 45 and 60min). Use of fresh raw material significantly increased yield of dry FPH, gave lighter and less yellow powders with better emulsification properties. Longer time of hydrolysis gave higher FPH yield, increased degree of hydrolysis and decreased water holding capacity of the powders. Among the hydrolysis times tested, 25 and 45min hydrolysis demonstrated the best emulsification properties. FPH have potential to enhance product stability by preventing oxidative deterioration. The DPPH scavenging activity showed that antioxidative activity of hydrolysates could be due to the ability to scavenge lipid radicals. The ability of hydrolysates to inhibit iron induced lipid oxidation was not influenced by time of hydrolysis. This work also shows that it is possible to obtain bioactive molecules from cod backbones by protein hydrolysis. The content of bioactive peptides (gastrin/CCK- and CGRP-like peptides) could make the cod hydrolysates useful for incorporation in functional foods. [Copyright &y& Elsevier]

Abstract: The acid-induced gelation of natural actomyosin (NAM) from burbot (Lota lota) and Atlantic cod (Gardus morhua) added with d-gluconic acid-δ-lactone (GDL) during incubation at room temperature (22–23°C) for 48h was investigated. During acidification, pH values of both NAMs reached 4.6 within 48h. Both NAMs underwent aggregation during acidification as evidenced by increases in turbidity and particle size, especially after 6h of incubation. The decreases in Ca2+-ATPase activity and salt solubility of both NAMs were observed during incubation. Decreases in total sulphydryl content with the concomitant increases in disulphide bond content of NAM from both species were also noticeable. Additionally, surface hydrophobicity of NAM increased, suggesting the conformational changes in NAM induced by acidification. The storage modulus (G′) values increased with increasing incubation time and G′ development was greater in Atlantic cod NAM, compared with burbot NAM. Differential scanning calorimetry (DSC) revealed that T max and enthalpy of myosin peak shifted to the lower values and endothermic peak of actin completely disappeared. In general, gel development was more pronounced in Atlantic cod NAM, compared with the burbot counterpart. As visualised by transmission electron microscopy, network strands of aggregates from Atlantic cod were finer and more uniform than those of the burbot counterpart. Acid-induced gelation of NAM from both fish species therefore involved both denaturation and aggregation processes. However, gelation varied with fish species and had an impact on the resulting gels. [Copyright &y& Elsevier]

Abstract: Physicochemical and rheological properties of myosin from Atlantic cod and burbot during acid-induced gelation at room temperature (22–23°C) by d-gluconic acid-δ-lactone (GDL) were monitored. Turbidity and particle size of both myosins increased and salt soluble content decreased when pH decreased, suggesting the formation of protein aggregates caused by acidification. The formation of disulphide bonds in myosin gelation was induced by acid. Ca2+-ATPase activity of myosin decreased (p <0.05), while surface hydrophobicity increased during acidification (p <0.05). Furthermore, the decreases in maximum transition temperature (T max) and the denaturation enthalpies (ΔH) were found in both myosins. During acidification, the increases in storage modulus (G′) and loss modulus (G″) of myosin were observed (p <0.05), revealing the formation of elastic gel matrix. Thus, gelation of myosin from Atlantic cod and burbot could take place under acidic pH via denaturation and aggregation. However, myosin from Atlantic cod was generally more favourable to gelation than was burbot myosin. [Copyright &y& Elsevier]

Abstract: Effects of irradiation at different doses (0, 2 and 6kilogray (kGy)) on the microbiological, chemical and physical properties of Som-fug, a Thai fermented fish mince, were investigated. Lactic acid bacteria (LAB), yeast and mould counts in samples irradiated at 6kGy were not detectable throughout the storage of 30days at 4°C, whereas no growth was found in the sample irradiated at 2kGy within the first 10days. Generally, greater carbonyl contents of lipid and protein, as well as thiobarbituric acid-reactive substances (TBARS), were noticeable in the irradiated samples, than in the non-irradiated sample (p <0.05). The carbonyl contents and TBARS increased with increasing storage time and the rate of increase was more pronounced in samples irradiated at higher dose (p <0.05). With increasing storage time, Som-fug irradiated at 6kGy showed greater decreases in hardness, adhesiveness, springiness and cohesiveness, than did non-irradiated samples and those irradiated at 2kGy (p <0.05). L ∗ value of all samples decreased, whereas a ∗ and b ∗ values increased throughout storage (p <0.05). Lower acceptance in all attributes was observed in the samples irradiated at 6kGy, than in other samples, particularly when storage time increased (p <0.05). However, samples irradiated at 2kGy showed no changes in acceptability within 20days. The results revealed that irradiation at high dose (6kGy) might induce lipid and protein oxidation, though the growth of microorganisms was inhibited. Therefore, the irradiation at low dose (2kGy) could be used to control the overfermentation of Som-fug up to 20days at 4°C without adverse effects on quality and acceptability. [Copyright &y& Elsevier]

Abstract: During enzymatic hydrolysis of cod (Gadus morhua) by-products four lipid containing fractions were generated: oil, emulsion, fish protein hydrolysates and sludge. The raw material consisted of combinations of viscera, backbone and digestive tract and was hydrolysed with, respectively, Flavourzyme, Neutrase or without addition of enzyme. The effect of water addition was also studied. The fatty acids and lipid classes were distributed unequally between the fractions and the distribution were influenced by the hydrolysis conditions. Highest yield of oil was obtained with no water added. The triacylglycerols were mainly found in the oil fraction, while the phospholipids were more difficult to extract from the mixtures. The sludge contained up to 50% lipids with a phospholipid content up to 60%. This might be a bulk product for further processing and purification of phospholipids. The highest amounts of eicosapentaenoic and docosahexaenoic acid were found in lipids in the protein containing fractions. [Copyright &y& Elsevier]

Abstract: The aim of this work was to study how raw material mixtures combined from different separated cod (Gadus morhua) by-products influenced the composition of the substrate for hydrolysis. The influence of using an endo-peptidase (Flavourzyme) or exo-peptidase (Neutrase) and the amount of added water on yield, nutritional, physicochemical and functional properties of the hydrolysis products was also studied. All freeze-dried fish protein hydrolysates (FPH) powders had a light yellow colour and contained 75–92% protein. The dried insoluble material, sludge, was a grey, greasy powder containing 55–70% protein. Degree of hydrolysis was 18.5–33.7% for FPH and 4.3–10.9% for sludge. Different ways of combining fish by-products lead to different end products with different properties after hydrolysis. Raw material containing the highest amount of lipids gave the lowest percentage of solubilised proteins. Addition of water before hydrolysis was more important than the type of enzyme used for yield, biochemical and functional properties of FPH and sludge. Protein efficiency ratio (PER) of sludge was generally 1.5 times higher than PER value of FPH. Sludge made up a large part after hydrolysis compared to fish protein hydrolysate, contained a significant part of the total protein and had good functional properties, in some cases even better than the FPH, which is often considered the main product of protein hydrolysis. [Copyright &y& Elsevier]

Abstract: The aim of this work was to study how different raw material mixtures from cod (Gadus morhua) by-products influenced the composition of the substrate for hydrolysis, yield and chemical composition of the different fractions after the enzymatic hydrolysis using endo-peptidase (Flavourzyme) or exo-peptidase (Neutrase). The most important factor influencing the yield of the different fractions was added water rather than type of enzyme used. The highest lipid yield was obtained in samples without addition of water resulting in a decreased yield of fish protein hydrolysates (FPH). Use of Neutrase produced more dry FPH (23–57%) than Flavourzyme. The amount of oil fraction obtained after Neutrase treatment was up to 10% higher compared to Flavourzyme due to 13–60% smaller emulsion layer and higher degree of hydrolysis in sludge liberating more lipids from sludge to oil fraction. Emulsion, which is not a desirable fraction after hydrolysis can also be reduced or avoided by reduction or/and elimination of addition of water into hydrolysis mixture. [Copyright &y& Elsevier]

The effects of smoking temperature and storage period on different properties related to proteins and enzymes in cold-smoked salmon were investigated. The smoking temperature was important for the solubility properties and the composition of myofibrillar proteins in smoked salmon. Increasing the smoking temperature reduced the extractability of myofibrillar proteins, and their composition was greatly affected. SDS-PAGE analysis revealed that the intensity of the myosin heavy chain band was reduced with increasing smoking temperature and with further storage of smoked samples. The content of free amino acids increased with smoking and further storage, but smoking temperature did not affect the total content or the composition of free amino acids. The smoking temperature did not affect cathepsin B-like activity or the general proteolytic activity. Differences caused by different smoking temperatures were reduced by further storage (+7 days). In conclusion, the effect of the processing parameters was most pronounced early in the product''s life. [Copyright &y& Elsevier]

Pulsed electric field (PEF), as an emerging technique, has recently gained increased popularity in food processing and preservation. However, applications in the seafood industry are still scarce. In the present study, sea bass samples were subjected to PEF pre-treatment prior to brine salting to verify the possible acceleration of the brining rate, increasing the salt uptake and ensuring the homogeneous salt distribution in the muscle. The applied intensity of the current was set at 10 and 20 A (corresponding to a field strength of 0.3 and 0.6 kV/cm) prior to sea bass salting in brine with 5 and 10% salt concentration, respectively. The results have shown that PEF pretreatment could effectively shorten the brine salting time compared to control samples (from 5 to 2 days), or increase the salt uptake up to 77%, ensuring at the same time its homogenous distribution in the muscle. However, myofibrillar protein solubility was significantly reduced in PEF pretreated samples. At the same time, no significant differences in water holding capacity and water activity between PEF pre-treated and untreated samples were found during the whole salting period. Freezable water was influenced by PEF application, but the effect was significant only at the lowest salt concentration during the first period of the salting process. PEF-assisted brining appears a promising technology in the fish processing industry due to its efficacy in reducing the salt brining time, increasing the mass transfer and enhancing the diffusion of brine into the muscle to ensure the homogeneous distribution of salt in it. The increased salt uptake of the PEF-treated samples compared to control samples shows future potentiality of using PEF prior to salting in the fish processing industry. • PEF pre-treatment allowed to shorten brining times in sea bass fillets. • NaCl uptake was increased in seabass fillets compared to untreated samples. • Water state and distribution was only slightly affected by PEF treatment. • Reduction of myofibrillar protein solubility during brining was observed. [ABSTRACT FROM AUTHOR]

• Mechanically filleted mackerel was susceptible to lipid oxidation during storage. • Dipping fillets into sodium erythorbate prolonged shelf-life from 2.5 to >15 months. • Results of TBARS did not correlate with sensory evaluation results. • TBARS a questionable method for 2. oxidation assessment in complex muscle systems. This study aimed to evaluate the shelf-life of mechanically filleted well-fed Atlantic mackerel during frozen storage at −25 °C and effect of treatment with antioxidants (sodium erythorbate and a polyphosphate mixture) and different antioxidant application methods (dipping, spraying and glazing). Both physicochemical measurements and sensory analysis were applied. Antioxidant treatments prolonged shelf-life of mackerel. Sensory analysis indicated that untreated fillets had a shelf-life of less than 2.5 months, while all antioxidant treated fillets exceeded that. The most effective treatment, dipping fillets into a sodium erythorbate solution, yielding a shelf-life of 15 months. Physicochemical methods used to evaluate degradation of lipids in the fillets were free fatty acids (FFA), lipid hydroperoxides (PV) and thiobarbituric acid reactive substances (TBARS). They did not correlate with sensory results and might therefore be a questionable choice for evaluation of oxidation and development of rancid flavour and odour in complex matrixes such as Atlantic mackerel. [ABSTRACT FROM AUTHOR]

The study focused on assessing quality parameters of haddock and mackerel minces subjected to a high-pressure treatment (HP) at 200 and 300 MPa and frozen storage at −40 °C. Dry matter, water-holding capacity, protein solubility and oxidation, lipid oxidation, microbiological parameters, low molecular weight metabolites (LMW) and color parameters, were analyzed. The texture of fishcakes prepared on the basis of these fish minces was also studied, showing a decrease in firmness along with an increase in pressure. A marked inhibition of microbial growth was observed in fish minces when increasing the pressure level of HP-treatment. However, no significant effect (p < 0.05) on the content of primary and secondary lipid oxidation products was observed between untreated and 300 MPa-pressurized fish samples. The results suggested that HP-treatment could be successfully applied to both lean and fatty fish samples for reduction of microbial growth with minor changes in product quality. Industrial relevance. The application of high pressure (HP) treatment of 200 and 300 MPa could be successfully applied to both lean and fatty fish species before freezing for reduction of microbial growth. The degree of lipid oxidation is decreasing with an increase in pressure as a result of inactivation of prooxidative endogenous enzymes. Fish minces become slightly lighter and softer after HP-treatment conducted at 200 MPa due to denaturation of proteins, thus enhancing sensory properties of fishcakes prepared thereof. Unlabelled Image • High pressure processing increases protein carbonylation in fish minces. • Protein solubility decreases for pressurized frozen fish minces. • Pressure enhances fluid drain from fish minces. • Improved microbiological profile of pressurized minced fish • Firmness of fishcakes decreased along with a pressure increase. [ABSTRACT FROM AUTHOR]