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.     

Effects of Salt-curing Procedure and Smoking Temperature on Astaxanthin Stability in Smoked Salmon

ABSTRACT: The effects of salting method (injection salting compared with dry salting), smoking temperature (20°C compared with 30°C), and storage (chilled storage compared with no storage) on astaxanthin retention, surface coloration (CIE1994 L * a * b *), and process yields of cold-smoked Atlantic salmon ( Salmo salar ) fillets was investigated. An overall loss of 13% astaxanthin was observed when correcting for weight changes. Astaxanthin retention was 6.0% higher after smoking at 30°C than at 20°C ( P < 0.01). A significant decrease in astaxanthin retention (4%) was observed after chilled storage of vacuum-packaged fillets at 1°C ( P < 0.05). Salt curing was quantitatively more important to astaxanthin loss than smoking temperature and storage. Salting method did not affect astaxanthin retention, but its concentration was reduced significantly more by injection salting than with dry salting ( P < 0.01). A higher overall color change (AE) was observed for dry-salted compared with injection-salted fillets ( P < 0.001) and for fillets smoked at 30°C compared with 20°C ( P < 0.05), and this coincided with a high variability in the colorimetric parameters in these groups. Higher product yields were obtained by injection salting compared with dry salting (10%) and after smoking at 20°C compared with 30°C (2%), P < 0.001. It is concluded that choice of processing technology may have substantial impact on important quality parameters such as color stability and variation in cold-smoked Atlantic salmon.     

The effects of pre-salting methods on water distribution and protein denaturation of dry salted and rehydrated cod - A low-field NMR study

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 T₁, and the faster relaxing transverse relaxation time T₂₁ 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.     

Effects of different salting and smoking processes on the microstructure, the texture and yield of Atlantic salmon (Salmo salar) fillets

The effect of different conditions during the salting and smoking process on the microstructure and the texture of salmon fillets was studied in interaction with different raw salmon material; ocean-ranched Atlantic salmon (Salmo salar) from Iceland and two groups of farmed Atlantic salmon (Salmo salar) from Norway, one from Northern Norway and one from Western Norway. The ocean-ranched salmon was found to have significantly smaller fiber diameters and higher shear force compared to the farmed fish. The cross-sectional area of the muscle fibers decreased during the salting and smoking process. Small differences were noted in the cross-sectional area between smoked fillets processed by different salting and smoking methods. However, the cross-sectional area of fibers in dry salted fish fillets from the farmed groups were significantly smaller than in the brine salted fillets, as the fibers shrunk more during dry salting than brine salting. The force required to shear the smoked fillets was significantly higher than for the unprocessed fillets, but was not found to be related to the different salting and smoking processes. Yield during smoking was not related to the initial cross-sectional area or the shear force of the unprocessed muscle.     

Atlantic salmon (Salmo salar,L.) as raw material for the smoking industry. I: effect of different salting methods on the oxidation of lipids

The changes in total fat content, fatty acid composition, tocopherol, ascorbic acid, pH and oxidation were analysed in response to different salting methods, either dry or brine, in cold-smoked (20 or 30 °C) Atlantic salmon (Salmo salar, L.). The fish were lean ocean-ranched salmon caught at Iceland in June 1998 and farmed Norwegian salmon slaughtered in November 1998 and April 1999, differing in fresh fillet fat content from 84 to 169 g kg⁻¹ wet weight. The total fat content decreased in all groups during processing, whereas the relative fatty acid composition of the fillets was not severely affected during salting and cold-smoking. The most conspicuous process consumption of antioxidants in all the groups was the relative ascorbic acid loss (58–82%). Generally, no clear effect of different salting methods was observed on the tocopherol loss during processing, but brine salting had a stronger effect on both fat and ascorbic acid loss than dry salting. The fattiest fish showed the highest oxidation during processing and they lost more tocopherol, but the final oxidation levels were generally low (thiobarbituric acid reactive substances, TBARS: 6.0–14.7 μmol kg⁻¹), reflecting the antioxidative protection offered by the vitamins during processing.     

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.     

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.     

CHEMICAL AND MICROBIOLOGICAL QUALITIES OF DRY-SALTED (LAKERDA) BONITO (SARDA SARDA, BLOCH 1793)

In this study, changes in the chemical and microbiological properties of bonito (Sarda sarda, Bloch 1793) salted by dry salting (lakerda) and stored for 6 months at 4 ± 1C were investigated. The fresh gutted and sliced bonitos were used as raw material for salting by using the ratio of fish to salt as 5:1 by weight. Salted fish remained in the liquid pickle formed by salt and the liquid extracted from the fish. This solution was not drained during the storage period. The product is described as “lakerda” in Turkey. In the fresh fish, total volatile basic nitrogen (TVB‐N) and trimethylamine nitrogen (TMA‐N) values were 11.21 mg/100 g and 1.19 mg/100 g, respectively. During the storage period, TVB‐N and TMA values increased slowly to 27.67 mg/100 g and 4.99 mg/100 g, respectively, at the end of the storage period. In the first month after salt processing, the total mesophilic bacteria count was 4.6 × 10² cfu/g. In the later months, mesophilic, psychotropic, coliform bacteria and yeast‐mold did not reproduce. According to the results, bonito salted by dry salting and stored at 4 ± 1C was in good quality in terms of chemical and microbiological properties during the storage period of 6 months.     

Sensory,physical, chemical and microbiological changes in aquacultured meagre (Argyrosomus regius) fillets during ice storage

Commercial-sized meagre fillets were stored on ice at 4 °C for 18 days, in order to evaluate the loss of quality and freshness that occurs over this period of time. Physicochemical (pH, thiobarbituric acid (TBA), total volatile basic nitrogen (TVBN), trimethylamine (TMA), water activity, water-holding capacity, colour, texture and fatty acid profile), sensory and microbiological analyses were carried out at 0, 4, 7, 11, 14 and 18 days of storage. As part of the sensory analysis, attributes associated with fillet appearance, odour and texture were examined. Variations in pH, TBA, TVBN and TMA were observed throughout the storage period, although only TBA displayed a significant correlation with time (r = 0.96). L^∗ and b^∗ values increased, and the chroma and hue values decreased, reflecting the colour changes experienced by the fillets over time. With regards to the texture profile, hardness was significantly correlated with time (−0.68). All the sensory analysis attributes exhibited significant variations and correlations close to 1.00 with storage time, which is a reflection of the fillets’ loss of freshness. The correlation coefficients between aerobic mesophilic and psychrophilic bacteria, enterobacteria and coliform counts on the one hand and storage time on the other were also very high (0.99–1.00). A regression analysis using the acceptability limit set by the ICMSF standard (1986) for total aerobic mesophilic counts (7 log cfu/g) yielded a shelf-life for meagre fillets of 9 days. The TBA, sensory and microbiological analyses displayed very strong correlations with storage time, and they may be considered suitable indicators for evaluating meagre fillet spoilage during refrigerated storage.     

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.     

Shelf Life of Fresh Tilapia Fillets Packaged in High Barrier Film with Modified Atmospheres

The effect of modified atmospheres (MAs) (75% CO₂:25% N₂; 50% CO₂: 50% N₂; and 25% CO₂: 75% N₂) and 100% air on shelf life of fresh tilapia fillets packaged in high barrier film bags was evaluated at refrigeration temperature (4.0°). Fillets packaged in 100% air spoiled after 9 days, as indicated by sensory characteristics, and had increased surface pH, TMA content, K-value and high microbial counts. When levels of CO₂ were increased from 25 to 75% in the package atmosphere, the shelf life of MA-packaged tilapia fillets was extended 4–21 days more than that of fillets packaged under 100% air. Although fillets packaged under 75% CO₂:25% N₂ were judged by sensory characteristics to be acceptable for more than 25 days, their K-value was high (93.1%). K-values were independent of spoilage and correlated only with length of storage of the MA-packaged fillets.     

Preservation of Grayfish (Squalus acanthias) by Salting

Grayfish (Squalus acanthias) fillets were preserved by an improved salting technique with pre-brining procedure along with ascorbic acid treatment in order to retard rancidity. The protein loss during salting was 2.4% and more than 2/3 fatty acid content of salted fillets decreased over 8 wk of storage at 20°C. The added ascorbic acid had an antioxidative effect for 2 wk of storage, after which the TBA values rose sharply. The organoleptic evaluation indicated no significant decrease in flavor until after 4 wk of storage. Statistical T-test showed no significant differences for appearance, odor, and texture among salted grayfish and salted cod fillets.     

Chemical quality and sensory attributes of marinated Pacific saury (Cololabis saira) during vacuum-packaged storage at 4 °C

This study was carried out to evaluate the chemical changes and sensory attributes of Pacific saury (Cololabis saira), brined (12% NaCl brine solution) or marinated (12% NaCl + 2% acetic acid; or 12% NaCl + 3% acetic acid solutions) followed by vacuum-packaging and storage at 4 °C for 90 days. The chemical analysis revealed a significant reduction in the pH value, total volatile bases nitrogen (TVBN), and trimethylamine (TMA) contents in marinated versus brined fillets. Lipid oxidation, as indicated by the 2-thiobarbituric acid (TBA) values, was significantly delayed in marinated fillets in comparison with the brined fillets. The growth rate of psychrotrophic bacteria was significantly (P < 0.05) reduced in marinated versus brined fillets. No significant differences were detected for the sensory attributes between the two marinating conditions although the overall acceptability was significantly higher in marinated versus brined fish. Both conditions of the marinating process resulted in an extension of the shelf life of the product to more than 90 days versus only 60 days for the control brined fillets. The study concluded that marination of Pacific saury can delay the undesirable chemical changes, retard lipid oxidation, improve the sensory attributes and extend the shelf life of the product during refrigerated storage.     

The effect of different salting procedures and qualities of raw material on some nutrients during processing and storage of salted-dried mackerel

Salted-dried mackerel ( Scomber scombrus ) was prepared using fresh fish or fish which had been stored in ice for 75h and four methods of salting, namely 15% brine, saturated brine, pickle and dry salting. Samples were analysed for available lysine, thiamine and riboflavin before salting, after salting, after drying and after 1 month's storage at 20°C. Final losses of each of these nutrients were lowest when the fish were pickle cured. Losses were also lower when fresher raw material was used. the use of good quality fish and a pickle salting method is therefore recommended for this type of product.     

Monitoring of microbial changes in salted cabbage (Jeolimbaechu) during recycled brining operation

To investigate possible recycling of a brine solution for the production of salted cabbage (jeolimbaechu), bacterial cell counts in the brine solution and salted cabbages were measured after repeated salting processes. After a salting process with a 13% brine solution for 15 hr at 10°C, the salt concentration in brine and salted cabbage decreased to 9.0–9.9 and 1.5–3.2% (depending on parts), respectively. After 5 repetitions, the total microbial count in the brine solution and salted cabbage gradually increased to 8.9 and 8.7 log CFU/g, respectively. Polymerase chain reaction-denaturing gradient gel electrophoresis (PCRDGGE) showed that the marine bacteria, Pseudoalteromonas sp. and Halomonas sp. appeared from the 3^rd batch; their intensities increased steadily and dominated the recycled brine solution. Meanwhile, Lactobacillus sakei found in the cabbage during the first salting process decreased with successive repetitions. These results show a high risk of marine microbial contamination in salted cabbage when the brine solution is re-used. Therefore, to re-use brine solution, application of proper inhibitory methods to prevent microbial cell growth in the brine solution is required.     

Influence of different storage conditions on production of trimethylamine and microbial spoilage characteristics of mackerel products

Gradual accumulation of the fishy-odor compound trimethylamine (TMA) from bacterial reduction of trimethylamine oxide (TMAO) is one of the characteristic chemical changes attributed to fish spoilage. Changes in TMA values were correlated with sensory testing results, storage temperature, storage time, and viable bacteria counts. TMA contents were determined under different storage conditions. Headspace solid-phase micro extraction analysis with gas chromatography using flame ionization detection was used with different storage times and temperatures. Mackerel samples were inoculated with Pseudomonas fragi to monitor changes in the TMA content and pH. The TMA content increased proportionally with time during storage, and pH values and the microbiological quality were evaluated to analyze correlations with the TMA content in fish products. The TMA content increased with an increasing number of P. fragi with good linearity (R ²=0.997). Basic data are provided for developing a freshness indicator for fish spoilage.     

Effect of ultrafiltration,fat reduction and salting on textural properties of white brined cheese

The influence of ultrafiltration of whole and skim milk on rennetability in the course of white pickled cheese manufacturing was investigated. Concentrating factors of the milk were selected as 3x, 4x, 5x and 5.5x. The renneting properties of the unconcentrated milk and the retentates (skim and whole milk ultrafiltration retentates) were explained. The white cheese produced from unconcentrated whole milk via a traditional industrial method was compared with the white cheese produced by whole milk retentate (5.5-fold). The cheeses manufactured from retentate were salted using different methods, i.e. dry salting, brine salting and salt addition before renneting. The effect of salting method on the texture of UF-cheese was determined after three months storage. It was suggested that producing of white pickled cheese from whole milk retentate (full-concentrated) was more suitable than manufacturing from skim milk retentate and was than better the conventional method which uses unconcentrated milk, actually.     

Shelf Life Assessment of Modified Atmosphere Packaged Turbot (Psetta maxima) Fillets: Evaluation of Microbial, Physical and Chemical Quality Parameters

Quality and safety of turbot fillets under modified atmosphere packaging (MAP) were assessed by microbial (total viable counts), physical (drip loss, pH, colour CIE Lab) and chemical parameters (total volatile basic nitrogen (TVBN), trimethylamine nitrogen (TMAN), biogenic amine contents). Three different atmospheres (MAP 1, 10/40/50 % O₂/CO₂/N₂; MAP 2, 10/60/30 % O₂/CO₂/N₂; MAP 3, 10/80/10 % O₂/CO₂/N₂) were tested. Packaged turbot fillets were stored at 2?±?1 °C and monitored over 30 days, at intervals of 5 days. Fillets from the control group, packaged with air (AIR), were the first to present signs of degradation reaching rejection threshold values for all evaluated parameters. In MAP fillets, total bacterial count was lower than 10⁶ cfu/g for a longer period. After 10 days of storage, MAP and AIR fillets showed significant differences (p?<?0.05) on the values of TVBN, TMAN and biogenic amines. MAP fillets presented a higher drip loss, and fillets in AIR became more yellowish (upper b* values) while those in MAP looked whitish for an increased period (upper L* values). All microbial, chemical and physical traits revealed the protective effect of the different MAP studied, especially those with a higher percentage of CO₂. MAP application added, at least, 5 days to shelf life of turbot fillets.