The effects of various salt concentrations during brine curing of cod (Gadus morhua)

The method used for salting of cod (Gadus morhua) is believed to influence the quality and characteristics of the final product. In recent years an initial brine salting for 1–4 days has preceded dry salting; this increases both the weight yield and quality of the final product. After removal from the brine, dry salting is followed by packaging and storage. The effect of the salt concentration in the brine has been a matter of controversy, with some indication that higher weight yield and quality may be obtained by using lower salt concentrations than by using a fully saturated brine solution. Therefore to test this hypothesis, the effect of different brine salting methods was studied; traditional brine salting, maintaining a constant brine concentration and increasing the salt concentration gradually during brining. The results indicated that the effect on weight yield, chemical composition and water holding capacity of the salted or rehydrated cod were not significant. Altering salt concentration of the brine, by adding salt during brining, did not result in any significant improvements in weight yield, either after the salting process or after the rehydration. The overall quality was increased by using a lower salt concentration of 16° Bau compared with 20 and 24° Bau.     

Effects of different pre-salting methods on protein aggregation during heavy salting of cod fillets

The use of injection and brining as the first step in heavy salting of cod increases weight yields of the products through both salting and rehydration, compared to other pre-salting methods, like brining only and pickling. This is interesting since salt content of the muscle exceeds 20% NaCl, in all procedures. Therefore, the dissimilarities in yield were presumed to depend on the degree of protein denaturation and aggregation as influenced by the different salting procedures. This hypothesis was studied and confirmed with the aid of SDS–PAGE and DSC-analysis. Higher water retention of injected products was explained by stronger salting-in effects on proteins during pre-salting, reducing aggregation of muscle proteins during the dry salting step. The degree of protein aggregation during salting increased in the following order with regard to the different pre-salting methods: injection and brining < brining < pickling. These effects were still observed after rehydration. Furthermore, differences in denaturation/aggregation were assigned to both myosin and collagen.     

Water properties and salt uptake in Atlantic salmon fillets as affected by ante-mortem stress,rigor mortis,and brine salting: A low-field H NMR and H/Na MRI study

A low-field (LF) ¹H NMR T₂ relaxation and ²³Na/¹H MRI study was performed on Atlantic salmon to study the effect of ante-mortem handling stress and rigor mortis on muscle water properties and subsequent post-rigor salting. Compared to rested fish, exhausted fish exhibited a more rapid and stronger development of rigor mortis. This resulted in significant differences in post-rigor water-holding capacity and salt uptake. By LF NMR T₂ relaxation analysis significant differences in water distribution according to (1) ante-mortem handling, (2) fillet location, and (3) brine salting were detected. Furthermore, ²³Na MRI revealed differences between the two treatments in fillet salt distribution, where the salt penetration in exhausted fillets was more pronounced. By combining ¹H and ²³Na MR images, the salt diffusion and distribution seemed to be highly affected by the distribution of fat.     

Salting and Desalting of Fresh and Frozen-thawed Cod (Gadus morhua) Fillets: A Comparative Study Using 23Na NMR, 23Na MRI, Low-field 1H NMR, and Physicochemical Analytical Methods

ABSTRACT: Fresh and frozen-thawed cod raw materials were subjected to brining, dry salting, and rehydration. The effects of salting and desalting on fillet water-related properties, salt content, and salt distribution were studied using 23Na MRI, 23Na NMR, and low-field (LF) 1H NMR. The results were compared with the Volhard titration method for salt determination, fillet pH, water content, and water-holding capacity. The rehydrated end product showed significant difference only with respect to water-holding capacity (unfrozen raw material higher) when fresh and frozen-thawed raw materials were compared. Excellent correlation was obtained between quantitative salt determinations using 23Na NMR and Volhard titration. When using a typical salting method, it was shown that the salt uptake and salt distribution in the fillets were inhomogeneous. Proton relaxation times, obtained from LF 1H NMR, were processed using either a 2-exponential model or the CONTIN algorithm. In several instances, a clear dependence on fillet pH, water-holding capacity, or salt content during fish processing was observed. Our results indicate that NMR and MRI can be used as useful tools to evaluate and optimize fish processing unit operations and that rapid (LF) NMR methods have the potential for replacing traditional salt and water-related analytical methods.     

Monitoring changes in feta cheese during brining by magnetic resonance imaging and NMR relaxometry

Magnetic resonance imaging (MRI) and NMR relaxometry were used to monitor changes in feta cheese during 169 h of brining at 4.8%, 13.0% and 23.0% salt solutions. Image and relaxation data were acquired to study salt uptake and water loss due to dehydration of cheese during brining. Saturation recovery and Carr-Purcell-Meiboom-Gill (CPMG) sequences were used to determine the longitudinal relaxation (T₁) and the transverse relaxation (T₂) times, respectively. Signal intensities of T₂ weighted images decreased during 169 h of brining. An excellent linear correlation between the average signal intensity and the water content was obtained (R² = 0.984). The T₁ values of cheese brined at 4.8% were almost constant but T₁ values decreased for both 13.0% and 23.0% salt brined cheeses. Analysis of the CPMG decays gave relaxation spectra containing two components which decreased during brining. The short component T_2a was highly correlated with salt content (R² = 0.974). Results showed that NMR and MRI can be used to follow salt uptake and changes in water content in cheese during brining.     

The quality of cold-smoked Atlantic salmon (Salmo salar) as affected by salting method, time and temperature

The effects of temperature (4 and 10–12 °C) and time (6, 12 and 24 h) on colorimetric parameters (Commission International de l'Eclairage (CIE) L*a*b*), carotenoid concentration, salt content and yield were investigated in brine (saturated or 50% saturation) and dry salted fillets of cold‐smoked Atlantic salmon (Salmo salar). Lightness (L*), yellowness (b*), hue (H_ab) and chroma (C*) values were lower at 10 than 4 °C (P < 0.01), whereas redness (a*) was unaffected. L* increased (P < 0.05) and a*, b*, H_ab and C* values dropped when salting time was increased (P < 0.001). Astaxanthin concentration of brine‐salted fillets decreased with increasing salting time (P < 0.05), but was unaffected by salting temperature. Increasing salting time affected colour negatively. The salt content of dry salted fillets increased with temperature and salting time. The process yield was unaffected by temperature and decreased with salting time. In conclusion, the cold smoking process is more important for variation in quality parameters than the salting process.     

Low field Nuclear Magnetic Resonance on the effect of salt and modified atmosphere packaging on cod (Gadus morhua) during superchilled storage

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.     

Effects of Brining Conditions on Weight Gain in Herring (Clupea harengus) Fillets

Salted herring is an important product category in many European countries. Reduced need for salt as a preserving agent and the increased emphasis on less salt in the human diet has changed the basis for the traditional processing of these products. This has led to significant changes in the processing conditions and in the characteristics of the salted products. In this perspective, the effects of different brine concentrations (10.0%, 16.5%, and 25.5%), brining temperatures (3.5 °C and 17.5 °C), the presence of skin or not on the fillets, and brining time (1, 2, 3, 4, and 7 d) were investigated on the weight gain (%) and final salt content (%) of herring (Clupea harengus). A significant (P < 0.001) higher weight gain of the fillets were observed at the lowest brining temperature (3.5 °C) compared with at the higher temperature (17.5 °C), independently of brine concentration and brining time. Increased brine concentration and skinning of the fillets caused the weight gain to significantly decrease (P < 0.001) and increase (P < 0.001), respectively. After 1 d of brining, the weight gain was in the range of 10% to 12% for both brining temperatures, and at the lowest temperature, the weight gain increased significantly (P < 0.001) as a function of brining time. At the higher temperature, no further significant increase in weight was observed from 1 to 7 d of brining. It is concluded that the weight gain in herring fillets brined according to the present commercial practice is significantly affected by temperature, brine concentration, brining time, and the presence or not of skin on the fillets and that the weight gain may be of high magnitude.     

Study of the influence of pulsed electric field pre-treatment on quality parameters of sea bass during brine salting

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.Industrial relevancePEF-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.     

Physicochemical,sensorial and textural characteristics of liquid‐smoked salmon (Salmo salar) as affected by salting treatment and sugar addition

The effect of salting method, dry salting (DS), brine salting (BS), brine salting with sucrose addition (BSS) or dry salting with sucrose addition (DSS) on the quality of Atlantic salmon treated with a liquid smoke flavouring was investigated over a 45‐day storage period. Sugar‐added samples were the ones with the significantly lowest values for TBARS (β₀, DS = 0.09^b; BS = 0.18^a; DSS = 0.07^c; BSS = 0.07^c). BSS and DSS fillets showed faster production rates of trimethylamine (TMA), 0.57 and 1.46, than the DS and BS fillets, 0.81 and 1.19, respectively. The DS and DSS fillets showed long delay periods before the TMA concentration started to increase (16.18; 20.60), and 90% of the panellists preferred these to BS or BSS fillets. In fact, only the BSS fillets were rejected during the storage, after 34 days; and the fillets with the most overall desirable characteristics at the end of the storage period were those of the DSS group.     

The effects of presalting methods from injection to pickling, on the yields of heavily salted cod (Gadus morhua)

The production of heavy-salted cod (Bacalao) has changed from being a single-step process (kench) salting to a multistep procedure varying between producers and countries. Presalting by injection, brining, or pickling is increasingly applied prior to pile (dry) salting. This article describes the effects of different presalting methods (injection and brining, brining only, and pickling) on yield and chemical composition of salted cod fillets, in comparison to a single-kench salting step. The procedures used influenced the weight yields and chemical composition of the products. Injection was significantly different from other methods in increasing weight yields throughout brining, dry salting, and rehydration. The yield of nitrogenous compounds tended to be lower for injected and brine-salted fillets, mainly due to higher losses of nonprotein nitrogen. Practical Application: Salting procedures for cod have changed rapidly in recent years. Injection is increasingly used as a presalting method. It has been suggested to have strong effects on weight yields of salted cod products. This article describes the effects of injection on weight yields on products in salted, rehydrated, and cooked stage.     

NaCl-induced changes in structure and water mobility in potato tissue as determined by CLSM and LF-NMR

This study for the first time reports the combined use of low-field nuclear magnetic resonance (LF-NMR) and confocal laser scanning microscopy (CLSM) in the study of the effects of salting on low and high dry matter (DM) potato tissue. The simultaneous use of CLSM and NMR resulted in important information in relation to the interpretation of the origin of the NMR water populations. Salting caused the raw potato cells to loose weight, which in the microscopic images was observed as loss of turgor pressure still further away from the edges of the samples with increased salting time. The total water loss after salting was lowest for high DM potatoes. The LF-NMR analyses revealed that this could be ascribed to a faster T₂ relaxation time of the cytoplasmatic and extracellular water and thus to water being more restricted in high DM potatoes. In addition, a tendency to a faster T₂ relaxation time was observed for both low and high DM potatoes with increasing salting time, which reveals a salt-induced restriction of the cytoplasmatic and extracellular water population. The paper illustrates the aptitude of NMR and CLSM to determine and elucidate structural changes and associated changes in water mobility in potato tissue.     

Protein denaturation and water-protein interactions as affected by low temperature long time treatment of porcine longissimus dorsi

The relationship between water–protein interactions and heat-induced protein denaturation in low temperature long time (LTLT) treated pork Longissimus dorsi was investigated by combining low-field NMR T₂ relaxometry with DSC measurements and measures of shrinkage of porcine Longissimus dorsi heated to 53 °C, 55 °C, 57 °C and 59 °C for either 3 or 20 h. Water within the myofibrils, measured by NMR T₂₁ relaxation times, was affected by both temperature and holding time during LTLT treatment between 53 °C and 59 °C. The changes in NMR T₂₁ relaxation times were associated with decreased fiber diameter and increased cooking loss, revealing a relationship between transverse shrinkage, water–protein interactions and cooking loss. DSC measurements revealed a concomitant decrease in ΔH_68 °C, which suggests impact of collagen denaturation on the retention of water within the meat during LTLT treatment. Furthermore, a decrease in ΔH_75 °C suggested that prolonged cooking (20 h) resulted in actin denaturation leading to decreased T₂₁ relaxation times and higher cooking loss.     

Pre-rigor filleting and brining of farmed cod: Influence on quality and storage stability

Pre-rigor filleting as well as brining with a mixture of phosphates and salt could influence several quality parameters of cod fillets. The aim of this work was to evaluate which of these processes that affected selected quality parameters of farmed cod the most. The analyses were performed at several points during storage, enabling that the effects of time of filleting, brining and storage could be evaluated simultaneously.Pre- and post-rigor non-brined fillets had similar and significant weight loss during storage. The weight increase of pre- and post-rigor fillets due to brining were 2% and almost 10%, respectively, and brining significantly reduced the weight loss during storage. Liquid loss and total viable count (TVC) were significantly influenced by rigor state at time of filleting, brining and storage time, while water content was influenced significantly by time of filleting and brining. Brining and storage time significantly influenced the whiteness, while time of filleting and storage time had significant influence upon the fillet index. The growth of Photobacterium phosphoreum was affected by storage time only, and the pH of the fillets was not influenced significantly by any of the parameters tested.     

Influence of brine salting prior to pickle salting in the manufacturing of various salted-dried fish species

In Portugal, the production of salted-dried cod and similar species is a relevant fish industry. Pickle salting is the most common salting method in this industry. The objective of this work was to study the influence of brine salting before pickle salting in the characteristics of the final salted-dried product of different fish species. Three salting methods were studied: only pickle salting, brine salting at 16°Baumé followed by pickle salting and brine salting at 25°Baumé followed by pickle salting. Fish species studied were Gadus morhua, Gadus macrocephalus, Theragra chalcogramma. The results showed from 4.7% to 9.2% significant higher yields of salted-dried fish when using the lower salt content brine, but drying time increased from 32 to 45 h (35–65%), depending on size of the fish, and texture became significantly softer, what may imply that salted-dried fish using lower salt content brines may be perceived by consumers as a different product. No significant differences of color were obtained.     

The effects of salt concentration on conformational changes in cod (Gadus morhua) proteins during brine salting

The effects of different salt concentrations (6%, 15%, 18% and 24% NaCl (w/w)) on the conformational changes of cod muscle proteins during brine salting were examined in this study. Proteins were extracted from the brine salted samples with solutions of 1 M (5.9%) and 4 M (23.4%) NaCl and the quantity of salt soluble proteins (SSP), disulfide bond (S–S), total sulfhydryl (SH) and available SH content in the soluble fraction were determined. Increased salt concentration in cod muscle promoted protein denaturation and aggregation. The SSP and total SH content decreased, whereas the S–S bond and available SH content increased with increased salt concentration in cod muscle. Disulfide bond formation correlated (r = −0.6) with a decrease in total SH groups. Higher SSP and available SH groups of the samples at lower brine concentrations was explained by smaller concentration gradients and salt diffusion rates, resulting in stronger salting-in at early stages of the brining process. There was a significant difference in conformational changes in proteins extracted with a salt solution of 1 and 4 M, mainly due to a different degree of protein aggregation.     

Effects of different wet heating methods on the water distribution,microstructure and protein denaturation of pork steaks

This study aimed to investigate the influence of different wet heating methods (SC: steam cooking; BC: boiling cooking) on the water distribution, microstructure and protein denaturation of pork steaks. Results showed that SC increased the proton relaxation intensity (T₁ and T₂) and the amount of immobilized water, but decreased the amount of free water compared with BC treatment. Proton density images showed that the red area was more in SC treatment than BC treatment. Muscle volume contraction and microstructure destruction in SC treatments were lower than that of BC treatments. Meanwhile, SC had higher protein solubility, but lower surface hydrophobicity as compared with BC. Additionally, pork steaks containing salt cooked by the same heating method had higher water mobility than those of without salt. Moreover, salting process aggravated the swelling of muscle fibre structure and protein denaturation.     

Process control of lightly salted wild and farmed Atlantic cod (Gadus morhua) by brine injection, brining, and freezing--a low field NMR study

The aim of this study was to use low-field nuclear magnetic resonance (NMR) and traditional chemical methods to investigate the physical and chemical differences in wild and farmed cod processed pre- and postrigor, and how these properties were affected by brine injection, brining, and freezing. In prerigor processed farmed or wild cod, brine injections followed by brining for 2 d, with brine concentrations up to 5.5% and 4%, respectively, were not sufficient to reach a muscle salt concentration of 2% as aimed for, while wild cod processed postrigor had sufficient salt uptake after the same processing. Low-field NMR gave valuable information about the differences in the muscle structure between wild and farmed cod as well as the state of the water in the muscle during brine injection, brining, and during rigor tension. Low-field NMR is, therefore, a valuable tool that can be used to optimize the salting and storing processes of lightly salted cod products from both wild and farmed cod. For farmed cod to be used in the production of lightly salted products further research is needed. Practical Application: Optimal processing of lightly salted cod products is important to the fish industry, due to an increasing market for this product in southern Europe. Farmed cod, which is seen as a potential steady raw material source for this production, differs considerably from its wild counterparts by having other chemical and physical muscle properties, such as lower water content and lower pH. With the processing procedures used today the farmed cod can, therefore, only be used in some of the products, where wild cod is currently used as raw material. It is, therefore, important that the processing of these products is optimized with regard to these differences in the raw material. This study gives a valuable contribution to further studies about optimal combinations of brine injections, brining, and freezing of pre- and postrigor processed farmed compared to wild cod.     

Effects of salting method and storage time on composition and quality of feta cheese

Feta cheese was manufactured by using five different salting methods (dry salting for one day followed by addition of 6% NaCl brine, dry salting for 1,2 or 3 days followed by addition of 7% NaCl brine and dry salting for 3 days followed by addition of 8% NaCl brine). The effects of salting method and storage time on the composition, physicochemical, organoleptic and rheological properties of feta cheese were studied. It was found that moisture was not affected by salting method or storage time. The salting method but not the storage time had a significant effect on salt content. As the salt content of cheeses increased or the storage time was prolonged the moisture decreased. pH and cheese yield were not influenced by salting method but did decrease with storage time. Protein content was not affected by salting method or storage time, whereas fat content was affected by both factors. Proteolysis, lipolysis, organoleptic and rheological properties of cheeses were not influenced by the salting methods applied. On the other hand, storage time had a significant effect on proteolysis, lipolysis, cheese appearance, fracturability and percentage compression at the yield point. Dry salting of cheese for one day and preservation in 7% NaCl brine was considered as the most appropriate salting method for practical application.