PCR-RFLP of the mitochondrial cytochrome oxidase gene: a simple method for discrimination between Atlantic salmon (Salmo salar) and rainbow trout (Oncorhynchus mykiss)

A DNA-based method (PCR-RFLP) has been developed for discrimination between Atlantic salmon (Salmo salar) and rainbow trout (Oncorhynchus mykiss). The polymerase chain reaction (PCR) was used for amplification of a 464 bp fragment of the mitochondrial cytochrome oxidase subunit II (COII) gene. Digestion of the products with endonucleases Nci I and Sau 3AI, followed by agarose gel electrophoresis of the digested products, yielded specific restriction profiles that enabled direct visual identification of the species analysed. This PCR-RFLP methodology allowed clear discrimination of Atlantic salmon and rainbow trout samples both in raw and smoked products. © 1999 Society of Chemical Industry     

Proteolytic Activity in Muscle from Atlantic Salmon (Salmo salar)

The maximum proteolytic activity appeared in the neutral to slightly alkaline pH range. Heat-stable alkaline proteases were detected. Optimal activity was found at pH 8 and 65°C. The activity dropped off markedly below 60°C and above 70°C. Preincubation of the muscle-extract for about 10 min at 65°C stimulated the activity. Salmon muscle was especially susceptible to proteolytic degradation at elevated temperatures. No notable differences were detected in proteolytic activities of Atlantic salmon in the feeding stage (superior quality) and in the sexually mature stage.     

The effects of natural antioxidants and lighting conditions on the quality of salmon (Salmo salar) fillets packaged in modified atmosphere

The effect of lighting conditions (darkness, a low‐UV colour‐balanced lamp and supermarket fluorescents), along with the application of natural antioxidants (rosemary extract and ascorbic acid) on shelf‐life of salmon (Salmo salar) fillets packaged in modified atmosphere and stored at 1 ± 1 °C was studied. Darkness and lighting with low‐UV colour‐balanced lamps led to an extension of shelf‐life compared with conventional light, as assessed by a* values, lipid oxidation (TBARS value) and sensory evaluation. The application of natural antioxidants on the surface of MAP salmon fillets gave rise to a delay of lipid oxidation as well as an improvement of the sensory quality, mainly in the case of conventional lighting conditions. Copyright © 2005 Society of Chemical Industry     

大西洋三文鱼和虹鳟鱼双重PCR检测方法的建立及应用

为了实现大西洋三文鱼和虹鳟鱼的物种掺假快速检测,本研究建立了一种基于双重PCR（普通和荧光）的物种鉴定方法。通过序列分析,分别基于线粒体COⅠ和Cyt b基因设计大西洋三文鱼和虹鳟鱼特异性引物,验证引物的特异性并对双重PCR反应体系进行优化,建立大西洋三文鱼和虹鳟鱼的双重PCR快速鉴定方法。利用本研究设计的引物,仅大西洋三文鱼和虹鳟鱼可以分别扩增出108 bp和207 bp的特异性条带,而其他23种非目标物种均未有扩增条带。经验证,在双重PCR反应体系中,大西洋三文鱼和虹鳟鱼引物的最佳添加量分别为0.1和0.4 μmol/L,熔解温度分别约为81.5 ℃和85 ℃。利用该方法从29份市售“三文鱼”样品中检测到6份大西洋三文鱼和3份虹鳟鱼,且与DNA条形码比对结果一致。本研究建立的大西洋三文鱼和虹鳟鱼双重PCR（普通和荧光）鉴定方法具有良好的特异性和适用性,为大西洋三文鱼和虹鳟鱼物种鉴定提供了可靠的技术手段。     

Fatty acid composition in ocean-ranched Atlantic salmon (Salmo salar)

Summary  The difference in fat content and fatty acid composition in the muscle of one-and two-year-old ocean-ranched Atlantic salmon ( Salmo salar ) was studied and compared using spot samples. The fat content in the muscle of 1-year-old salmon was 4.8% of wet weight, and 5.0% in 2-year-old salmon. The effect was not statistically significant. The main constituents of the fat were palmitic acid (16:0), oleic acid (18:1,n-9), gadoleic acid (20:1,n-9) and erucic acid (22:1,n-9). Eicosapentaenoic (EPA) and docosahexaenoic acid (DHA) were predominant among the polyunsaturated fatty acids (PUFAs). There was a significant difference between the groups in relation to the content of stearic acid (18:0), palmitoleic acid (16:1,n-9) and oleic acid (18:1,n-9).     

双重实时荧光PCR法鉴别大西洋鲑鱼和虹鳟鱼

目的建立双重实时荧光PCR法同时鉴别大西洋鲑鱼和虹鳟鱼的检测方法。方法在现有单一物种检测方法的基础上,应用多重实时荧光PCR检测技术对大西洋鲑鱼和虹鳟鱼同时进行检测,并对PCR反应时间和反应温度进行优化。结果该方法通过1管PCR反应实现对大西洋鲑鱼和虹鳟鱼的同时鉴别,反应时间缩短至1 h以内,方法的特异性好,灵敏度可达到0.1%(DNA质量分数)。结论该方法检测效果好、时间短、成本低,可为监管部门解决三文鱼市场监管问题提供技术手段。     

Listeria monocytogenes in an Atlantic salmon (Salmo salar) processing environment

The behavior of two strains of Listeria monocytogenes (147 and ATCC 19111) was evaluated at different stages of salmon processing. At lower temperatures of 2, 7, and 11 degrees C, L. monocytogenes survived on dry wood surfaces for at least 3 days without added nutrients but was unrecoverable after 2 days at 22 degrees C. Moisture or minimal nutrients on the wood surface increased viability of L. monocytogenes at all incubation temperatures. When large amounts of nutrients were provided, the recoveries of L. monocytogenes at low temperatures (< or = 11 degrees C) were essentially unchanged over the 3-day holding period, and rapid growth was observed at room temperature. In the presence of natural microflora, L. monocytogenes died off rapidly in seawater within 36 h at room temperature. When held at < or = 11 degrees C, L. monocytogenes lost viability throughout storage but was still detectable after more than 6 days of incubation. In the absence of natural microflora, both strains of L. monocytogenes were static during the holding period at all temperatures. At 2, 7, and 11 degrees C, L. monocytogenes in nonsterile salmon blood-water remained viable even after 6 days of incubation, whereas in sterile blood-water, growth of L. monocytogenes was observed at 7 and 11 degrees C. In the absence of natural microflora, L. monocytogenes grew better than it did in the presence of natural microflora. L. monocytogenes 147 was more competitive with background organisms than was L. monocytogenes ATCC 19111. No L. monocytogenes could be detected in the digestive tract of salmon 3 days after its introduction. The survival pattern of L. monocytogenes in fish digestive tracts was similar, regardless of whether the fish were feeding or not. A noticeable decline in the pathogen was observed as early as 3 h after introduction.     

Quality grading of Atlantic salmon (Salmo salar) by computer vision

ABSTRACT:  In this study, we present a promising method of computer vision-based quality grading of whole Atlantic salmon ( Salmo salar ). Using computer vision, it was possible to differentiate among different quality grades of Atlantic salmon based on the external geometrical information contained in the fish images. Initially, before the image acquisition, the fish were subjectively graded and labeled into grading classes by a qualified human inspector in the processing plant. Prior to classification, the salmon images were segmented into binary images, and then feature extraction was performed on the geometrical parameters of the fish from the grading classes. The classification algorithm was a threshold-based classifier, which was designed using linear discriminant analysis. The performance of the classifier was tested by using the leave-one-out cross-validation method, and the classification results showed a good agreement between the classification done by human inspectors and by the computer vision. The computer vision-based method classified correctly 90% of the salmon from the data set as compared with the classification by human inspector. Overall, it was shown that computer vision can be used as a powerful tool to grade Atlantic salmon into quality grades in a fast and nondestructive manner by a relatively simple classifier algorithm. The low cost of implementation of today's advanced computer vision solutions makes this method feasible for industrial purposes in fish plants as it can replace manual labor, on which grading tasks still rely.     

Injection-salting of pre rigor fillets of Atlantic salmon (Salmo salar)

ABSTRACT:  The effects of temperature (−1, 4, and 10 °C), brine concentration (12% and 25% NaCl), injection volumes, and needle densities were investigated on fillet weight gain (%), salt content (%), fillet contraction (%), and muscle gaping in pre rigor brine-injected fillets of Atlantic salmon ( Salmo salar ). Increased brine concentration (12% to 25%) significantly increased the initial (< 5 min after injection) and final contraction (24 h after injection) of pre rigor fillets. Increased brine concentration significantly reduced weight gain and increased salt content but had no significant effect on muscle gaping. The temperatures tested did not significantly affect weight gain, fillet contraction, or gaping score. Significant regressions ( P < 0.01) between the injection volume and weight gain (range: 2.5% to 15.5%) and salt content (range: 1.7% to 6.5%) were observed for injections of pre rigor fillets. Double injections significantly increased the weight gain and salt content compared to single injections. Initial fillet contraction measured 30 min after brine injection increased significantly ( P < 0.01) with increasing brine injection volume but no significant difference in the fillet contraction was observed 12 h after brine injection (range: 7.9% to 8.9%). Brine-injected post rigor control fillets obtained higher weight gain, higher salt content, more muscle gaping, and significantly lower fillet contraction compared to the pre rigor injected fillets.
Injection-salting is an applicable technology as a means to obtain satisfactory salt contents and homogenously distribute the salt into the muscle of pre rigor fillets of Atlantic salmon before further processing steps such as drying and smoking.     

Lipid distribution and composition of commercially farmed atlantic salmon (salmosalar)

Skin, red and white muscle, belly flap, dorsal fat depot, backbone, head, visceral tissue and liver of commercially farmed Atlantic salmon (Salmo salar) were analysed for total lipid content, lipid classes and fatty acid composition. The fat is deposited in a number of tissues and organs with the highest level in the dorsal fat depot (38.4% of wet weight), red muscle (27.2%) and belly flap (28.1%). The fat content in white muscle is 9.6% of wet weight. The lipid class distribution is nearly uniform throughout the fish body. The belly flap contains the highest amount of triacylglycerols (98.8% of total lipid) and white muscle and visceral tissue have the lowest levels, 93.3% and 93.1%, respectively. The variation in total saturates, monoenes, polyenes, n-6 and n-3 fatty acids was much less between tissues than the variation in total lipid content. In the edible part, the belly flap (16.7%) contained significantly lower levels of n-3 fatty acids than red (18.4%) and white muscle (19.7%) mainly due to lower level of 22: 6n-3 and 20: 5n-3 fatty acids.     

Persistence and distribution of intravenously injected DNA in blood and organs of Atlantic salmon (Salmo salar L.)

In a recent study it was reported that DNA could be taken up from the feed and transferred to the blood of Atlantic salmon (Nielsen CR, Berdal KG, Bakke-McKellep AM, Holst-Jensen A, Eur Food Res Tech, 2005). In the present study the transport in blood and accumulation in some organs of intravenously injected DNA was studied. Intravenous injection was used as an alternative to feeding to ensure that the quantity of target DNA would permit a quantitative study of the distribution and degradation of the DNA in the fish. Three DNA fragments of different length were administered by injection to 40 salmon, each in a copy number of 10¹⁰. Blood and tissues were sampled at different time intervals after injection. To ensure the use of a sensitive and reliable detection system, real-time PCR methods with TaqMan chemistry were applied in this study. Target DNA was observed in blood and all investigated tissues, with peak levels observed at 0.5–1 h after injection. Some tissue samples were positive for the target DNA up to 24 h after injection. Results of the present study indicate that dietary DNA taken up in the blood may be transported to organs like liver and kidney, as well as muscle and gonads.     

Dietary DNA in blood and organs of Atlantic salmon (Salmo salar L.)

The objective of this study was to investigate the uptake of dietary DNA into blood, kidney, and liver of salmon, and to determine the DNA fragment size if dietary DNA was detected. Salmon in groups of five fish were force-fed a feed containing a high copy number of three polymerase chain reaction (PCR) amplified DNA fragments. Tissue samples were dissected from the fish at time intervals starting at 1 h after force-feeding (AFF) and ending at 64 h AFF. Real-time PCR analyses were used to determine the presence or absence of DNA targets. Sensitive methods amplifying small fragments were used to minimise the impact of fragmentation on the detectability of DNA targets. Uptake of dietary DNA was observed and the highest concentrations of dietary DNA in liver and kidney were found 8 h AFF. The results correspond to data published for similar trials performed on other animal species. An additional experiment showed that decontamination of the liver surface by flaming has the potential to decrease DNA contamination from, for example, feed remnants by up to 90%.     

Absence of nematodes in farmed Atlantic salmon (Salmo salar L.) in Norway

In the present study, a total of 1,180 samples of muscle or viscera from Norwegian-farmed salmon (Salmo salar L.) were examined for the presence of nematode larvae. The samples represented all salmon-producing counties in Norway. The method applied was based on the degradation of fish soft tissue in an acidified pepsin enzyme solution. None of the samples examined in this study contained nematodes.     

Gelatinolytic activities in muscle of Atlantic cod (Gadus morhua), spotted wolffish (Anarhichas minor) and Atlantic salmon (Salmo salar)

The gelatinolytic activity in muscle from Atlantic cod (Gadus morhua), spotted wolffish (Anarhichas minor) and Atlantic salmon (Salmo salar) was studied using gelatin SDS‐PAGE, gelatin affinity chromatography and enzyme inhibitors. These fish species are known to differ markedly in fillet softening and gaping post mortem. Atlantic cod, which is a promising species for cold water marine aquaculture, often shows such negative properties, particularly after being well fed. Gelatinolytic activity bands were present in all three species. Using gelatin chromatography and enzyme inhibitors, both serine proteinases and metalloproteinases were detected in wolffish and cod muscle, while only the latter were found in salmon muscle. Activation of the metalloproteinases by p‐aminophenylmercuric acetate (APMA) resulted in a shift in activity from higher to lower molecular weight, as is known for mammalian matrix metalloproteinases. In all three species the molecular weight of the metalloproteinases was lowered from approximately 80 to about 70 kDa by activating with APMA. Copyright © 2003 Society of Chemical Industry     

Effects of freezing and thawing processes on the quality of Atlantic salmon (Salmo salar) fillets

ABSTRACT:  High-pressure processing is finding a growing interest in the food industry. Among the advantages of this emerging process is the ability to favorably freeze and thaw food. This study aims at comparing the effect of different freezing and thawing processes on the quality of Atlantic salmon fillets. Atlantic salmon ( Salmo salar ) samples were frozen by Pressure-Shift Freezing (PSF, 200 MPa, −18 °C) and Air-Blast Freezing (ABF, −30 °C, 4 m/s). Samples were stored 1 mo at −20 °C and then subjected to different thawing treatments: Air-Blast Thawing (ABT, 4 °C, 4 m/s), Immersion Thawing (IMT, 20 °C), and Pressure-Assisted Thawing (PAT, 200 MPa, 20 °C). Changes in texture, color, and drip loss were investigated. The toughness of the PSF samples was higher than that of the ABF sample. The modification of color was more important during high-pressure process than during the conventional process. The PSF process reduced thawing drip compared with ABF. The presence of small ice crystals in the pressure-shift frozen sample is probably the major reason leading to the reduced drip volumes. The freezing process was generally much more influent on quality parameters than the thawing process. These results show the interaction between freezing and thawing processes on selected quality parameters.     

Computer vision-based sorting of Atlantic salmon (Salmo salar) fillets according to their color level

ABSTRACT:  Computer vision method was used to evaluate the color of Atlantic salmon ( Salmo salar ) fillets. Computer vision-based sorting of fillets according to their color was studied on 2 separate groups of salmon fillets. The images of fillets were captured using a digital camera of high resolution. Images of salmon fillets were then segmented in the regions of interest and analyzed in red, green, and blue (RGB) and CIE Lightness, redness, and yellowness (Lab) color spaces, and classified according to the Roche color card industrial standard. Comparisons of fillet color between visual evaluations were made by a panel of human inspectors, according to the Roche Salmo Fan™ lineal standard, and the color scores generated from computer vision algorithm showed that there were no significant differences between the methods. Overall, computer vision can be used as a powerful tool to sort fillets by color in a fast and nondestructive manner. The low cost of implementing computer vision solutions creates the potential to replace manual labor in fish processing plants with automation.     

State diagram of salmon (Salmo salar) gelatin films

BACKGROUND: A state diagram presents different physical states of a biomaterial as a function of solid content and temperature. Despite their technological interest, little information is available on protein systems such as gelatin/water mixtures. The objective of this work was to develop state diagrams of salmon gelatin (SG) and bovine gelatin (BG) in order to determine maximal freeze concentration parameters (T′_g, T′_m and X_s′) and to relate possible differences to their biochemical characteristics. RESULTS: Biochemical characterisation of SG showed lower molecular weight and iminoacid concentration compared with BG. Likewise, the glass transition temperature (T_g) was lower for SG at X_s > 0.8, which was associated with its lower molecular weight. Unexpectedly, the depression of freezing temperature (T_f) was greater for SG at X_s > 0.1, which was associated with its higher ash content. Isothermal annealing produced effective values of T′_g ≈ ? 52 °C, T′_m ≈ ? 46 °C and X′_s ≈ 0.6 for both gelatins. Interestingly, the enthalpy change associated with T′_m (ΔH) was significantly higher for SG than for BG after annealing, indicating a higher proportion of ice present at about ? 50 °C. CONCLUSION: Maximal freeze concentration parameters were similar between the two gelatins, though differences in biochemical properties were evident. The results show that there are likely different ways of interaction of SG and BG with water. Copyright © 2011 Society of Chemical Industry     

冰温保鲜和冷藏保鲜对生食大西洋鲑品质影响的比较研究

目的探讨冰温保鲜和冷藏保鲜对生食大西洋鲑品质变化的影响。方法将大西洋鲑分别置于-1.8℃冰温条件和4.0℃冷藏条件下贮藏,测定菌落总数、pH值、挥发性盐基氮(total volatile basic nitrogen,TVB-N)值、色差值、K值和感官评分,通过这一系列评价指标,综合分析大西洋鲑在冰温保鲜条件和冷藏保鲜条件下品质变化的不同。结果随着贮藏时间的延长, 2组的菌落总数值、TVB-N值、K值均呈上升趋势, pH值在冰温保鲜条件和冷藏保鲜条件下变化趋势相近,色差值在2个保鲜条件下波动变化没有明显差异,感官评分在2个不同温度条件下总体均呈现下降趋势。在冷藏保鲜条件下,生食大西洋鲑的货架期为2 d;在冰温保鲜条件下,生食大西洋鲑的货架期为5d。结论冰温保鲜方式可将生食大西洋鲑的货架期延长3d,与冷藏保鲜方式相比,冰温保鲜方式在大西洋鲑的贮藏过程中体现了良好的保鲜效果。