Lipid composition and contaminants in farmed and wild salmon

Levels of omega-3 (n-3) and omega-6 (n-6) fatty acids and lipid-adjusted concentrations of polychlorinated biphenyls (PCBs), dioxins, toxaphene, and dieldrin were determined in 459 farmed Atlantic salmon, 135 wild Pacific salmon, and 144 supermarket farmed Atlantic salmon fillets purchased in 16 cities in North America and Europe. These were the same fish previously used for measurement of organohalogen contaminants. Farmed salmon had greater levels of total lipid (average 16.6%) than wild salmon (average 6.4%). The n-3 to n-6 ratio was about 10 in wild salmon and 3-4 in farmed salmon. The supermarket samples were similar to the farmed salmon from the same region. Lipid-adjusted contaminant levels were significantly higher in farmed Atlantic salmon than those in wild Pacific salmon (F = 7.27, P = 0.0089 for toxaphene; F = 15.39, P = 0.0002 for dioxin; F > or = 21.31, P < 0.0001 for dieldrin and PCBs, with df = (1.64) for all). Levels of total lipid were in the range of 30-40% in the fish oil/fish meal that is fed to farmed salmon. Salmon, especially farmed salmon, are a good source of healthy n-3 fatty acids, but they also contain high concentrations of organochlorine compounds such as PCBs, dioxins, and chlorinated pesticides. The presence of these contaminants may reduce the net health benefits derived from the consumption of farmed salmon, despite the presence of the high level of n-3 fatty acids in these fish.     

Use of terrestrial based lipids in aquaculture feeds and the effects on flesh organohalogen and fatty acid concentrations in farmed Atlantic salmon

Consumption of salmon, wild or farmed, has been encouraged by many scientists and by national and international health organizations due to the potential health benefits associated with their high contents of omega-3 (n-3) highly unsaturated fatty acids (n-3 HUFAs). In 2004, there was increased public concern regarding the safety of farmed Atlantic salmon following the publication of several studies that indicated higher levels of organohalogens in their flesh relative to those noted in the flesh of wild Pacific salmon. Farmed salmon obtain most of these contaminants from the consumption of marine fish oil (MFO) present in salmon feed. In both a laboratory feeding trial and an on-farm field study, partial replacement of MFO in aquaculture feeds with economical and abundant lipids of terrestrial origin resulted in farmed Atlantic salmon with reduced flesh polychlorinated biphenyl and polychlorinated dibenzodioxin and furan concentrations. Flesh levels of n-3 HUFAs (g/(100 g serving)) were lower in farmed Atlantic salmon fed diets with alternative lipids relative to farmed salmon fed more traditional MFO-based diets. However, the former salmon were found to have higher flesh levels of n-3 HUFAs and also similar or lower flesh levels of organic contaminants than some species of market-size wild Pacific salmon. These findings showthat consumption of either farmed Atlantic salmon or wild Pacific salmon can meet recommended weekly n-3 HUFA levels with minimal concurrent intake of flesh organohalogens.     

Polychlorinated biphenyls in salmon and salmon feed: global differences and bioaccumulation

Concentrations of 160 polychlorinated biphenyl (PCB) congeners or congener groups were determined in approximately 600 farmed Atlantic salmon from around the world and wild (ocean-caught) Pacific salmon from the Northeast Pacific. Concentrations and PCB congener profiles were analyzed to provide insight into the sources and uptake of PCBs in salmon as well as regional differences. Although total PCB concentrations in wild salmon appeared to be correlated to total lipid content, the increased proportion of total lipids in the farmed salmon could not account for the much greater PCB concentrations. We investigated the PCB congener patterns of hundreds of salmon samples using principal component analysis to further illuminate regional and species differences. Three major PCB patterns were observed, in most wild fish (except British Columbia and Oregon chinook), in farmed fish from the Atlantic, and in most farmed fish from the Pacific. The PCB congener profiles of farmed salmon often closely corresponded to a sample of commercial feed purchased in the same region, indicating that the feed is likely to be the major source of PCBs for farmed salmon. In such cases where PCB profiles in fish and feed were similar, a comparison of congener concentrations in fish and the feed showed that the majority of congeners, with some notable exceptions, were bioaccumulative to the same extent, irrespective of physical properties.     

Characteristics of Color in Raw, Baked and Smoked Wild and Pen-Reared Atlantic Salmon

Color of wild, astaxanthin pigmented, and farmed, canthaxanthin pigmented, Atlantic salmon (Salmon salar) was evaluated by spectroscopy and visual sensory analyses. A more yellow hue in farmed salmon color compared with wild salmon was found in acetone extracts of raw salmon flesh and by visual sensory analyses of raw, baked and smoked salmon flesh. With instrumental color analysis directly on raw flesh, no significant differences in color between wild and farmed salmon were found. The redness and hue in raw and baked salmon flesh and the redness in smoked salmon were correlated to the pigment concentration in raw salmon. The redness and hue in processed salmon were predictable from the redness and hue of raw flesh.     

PCBs, PCDD/Fs, and organochlorine pesticides in farmed Atlantic salmon from Maine, eastern Canada, and Norway, and wild salmon from Alaska

Farmed Atlantic salmon (Salmo salar) from Maine and eastern Canada, wild Alaskan Chinook salmon (Oncorhynchus tshawytscha), and organically farmed Norwegian salmon samples were analyzed for the presence of polychlorinated biphenyls (PCBs), dioxin-like PCBs, polychlorinated dibenzo-p-dioxins (PCDDs), dibenzo-p-furans (PCDFs), and chlorinated pesticides. PCDD and PCDF congeners were not detected in > 80% of the samples analyzed. Total PCB concentrations (7.2-29.5 ng/g, wet weight, ww) in the farmed salmon were significantly higher than those in the wild Alaskan Chinook samples (3.9-8.1 ng/g, ww). Concentrations of PCBs, WHO PCB TEQs, and chlorinated pesticides varied significantly by region. PCB and WHO PCB TEQ concentrations in farmed salmon from eastern Canada were lower than those reported in samples collected two years earlier, possibly reflecting recent industry efforts to lower contaminant concentrations in feed. Organically farmed Norwegian salmon had the highest concentrations of PCBs (mean: 27 ng/g, ww) and WHO PCB TEQs (2.85 pg/g,ww); their TEQ values are in the higher range of those reported in farmed salmon from around the world. Removal of skin from salmon fillets resulted in highly variable reductions of lipids and contaminants, and in some skin-off samples, contaminant levels were higher, suggesting that skin removal does not protect the consumer from health risks associated with consumption of farmed salmon.     

Flesh quality of market-size farmed and wild British Columbia salmon

This study compared the flesh quality of farmed and wild sources of British Columbia (BC) salmon with respect to concentrations of polychlorinated biphenyl compounds, polychlorinated dibenzodioxins/dibenzofurans and their associated toxic equivalents, total mercury (THg), methylmercury (MeHg), and selected fatty acids of known importance for human health viz., omega-3 (n-3) highly unsaturated fatty acids (n-3 HUFAs) and (n-6) fatty acids. Skinned fillets from known sources of farmed Atlantic, coho, and chinook salmon (n = 110) and wild coho, chinook, chum, sockeye, and pink salmon (n = 91) were examined. Atlantic salmon contained higher PCB concentrations (means, 28-38 ng/g) than farmed coho or chinook salmon, and levels in these latter species were similar to those in wild counterparts (means, 2.8-13.7 ng/g). PCB levels in Atlantic salmon flesh were, nevertheless, 53-71-fold less than the level of concern for human consumption of fish, i.e., 2000 ng/g as established by Health Canada and the U.S. Food and Drug Administration (US-FDA). Similarly, THg and MeHg levels in all samples were well below the Health Canada guideline (0.5 microg/g) and the US-FDA action level (1.0 microg/g). On average, THg in farmed salmon (0.021 microg/g) was similar to or lower than wild salmon (0.013-0.077 microg/g). Atlantic salmon were a richer source (mean, 2.34 g/100 g fillet) of n-3 HUFAs than the other farmed and wild sources of salmon examined (means, 0.39-1.17 g/100 g). The present findings support the recommended weekly consumption guidelines for oily fish species (includes all BC salmon sources) for cardio-protective benefits as made by the American Heart Association and the UK Food Standards Agency.     

Levels of synthetic antioxidants (ethoxyquin, butylated hydroxytoluene and butylated hydroxyanisole) in fish feed and commercially farmed fish

Several synthetic antioxidants are authorized for use as feed additives in the European Union. Ethoxyquin (EQ) and butylated hydroxytoluene (BHT) are generally added to fish meal and fish oil, respectively, to limit lipid oxidation. The study was conducted to examine the concentrations of EQ, BHT and butylated hydroxyanisole (BHA) in several commercially important species of farmed fish, namely Atlantic salmon, halibut and cod and rainbow trout, as well as concentrations in fish feed. The highest levels of BHT, EQ and BHA were found in farmed Atlantic salmon fillets, and were 7.60, 0.17 and 0.07 mg kg(-1), respectively. The lowest concentrations of the synthetic antioxidants found were in cod. The concentration of the oxidation product ethoxyquin dimer (EQDM) was more than ten-fold higher than the concentration of parent EQ in Atlantic salmon halibut and rainbow trout, whereas this dimer was not detected in cod fillets. The theoretical consumer exposure to the synthetic antioxidants EQ, BHA and BHT from the consumption of farmed fish was calculated. The contribution of EQ from a single portion (300 g) of skinned fillets of the different species of farmed fish would contribute at most 15% of the acceptable daily intake (ADI) for a 60 kg adult. The consumption of farmed fish would not contribute measurably to the intake of BHA; however, a 300 g portion of farmed Atlantic salmon would contribute up to 75% of the ADI for BHT.     

Levels of synthetic antioxidants (ethoxyquin,butylated hydroxytoluene and butylated hydroxyanisole) in fish feed and commercially farmed fish

Several synthetic antioxidants are authorized for use as feed additives in the European Union. Ethoxyquin (EQ) and butylated hydroxytoluene (BHT) are generally added to fish meal and fish oil, respectively, to limit lipid oxidation. The study was conducted to examine the concentrations of EQ, BHT and butylated hydroxyanisole (BHA) in several commercially important species of farmed fish, namely Atlantic salmon, halibut and cod and rainbow trout, as well as concentrations in fish feed. The highest levels of BHT, EQ and BHA were found in farmed Atlantic salmon fillets, and were 7.60, 0.17 and 0.07?mg?kg^?1, respectively. The lowest concentrations of the synthetic antioxidants found were in cod. The concentration of the oxidation product ethoxyquin dimer (EQDM) was more than ten-fold higher than the concentration of parent EQ in Atlantic salmon halibut and rainbow trout, whereas this dimer was not detected in cod fillets. The theoretical consumer exposure to the synthetic antioxidants EQ, BHA and BHT from the consumption of farmed fish was calculated. The contribution of EQ from a single portion (300?g) of skinned fillets of the different species of farmed fish would contribute at most 15% of the acceptable daily intake (ADI) for a 60?kg adult. The consumption of farmed fish would not contribute measurably to the intake of BHA; however, a 300?g portion of farmed Atlantic salmon would contribute up to 75% of the ADI for BHT.     

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.     

Identification of the farm origin of salmon by fatty acid and HR C NMR profiling

Lipid analyses by gas chromatography (GC) and by high resolution (HR) ¹³C NMR combined with chemometrics were used to identify wild and farmed Atlantic salmon and the farm origin of farmed salmon. Reference samples were 59 specimens from four different farms in the Hardangerfjord (Norway) and the test fish were 17 free-living fish, caught in the same fjord. Four free-living fish were identified as wild by their fatty acids profile, n3/n6 ratio and by principal component analysis. To identify the farm of origin of farmed salmon, Bayesian belief networks (BBN) and support vector machines (SVM) were the best methods classifying correctly 58 (BBN and GC) and 56 (SVM and ¹³C NMR) of the 59 reference samples. Of the 12 free-living fish identified as farmed, four seemed to originate from farm 2 and 3 from farm 4. The rest could not be clearly attributed to any of the four farms and may originate from any of the other 26 farms located in the fjord.     

不同产地三文鱼的稳定同位素指纹特征及原产地溯源

本研究从深圳口岸获取我国三文鱼主要进口国（法罗群岛、挪威、智利、加拿大以及澳大利亚）的三文鱼样品共16?份,并采集中国产三文鱼（虹鳟）样品2?份,分析三文鱼肌肉、表皮、鳞片以及骨骼中的碳、氮、氢、氧、硫稳定同位素比值,比较不同产地以及不同部位同位素分布差异,采用判别分析对不同产地进行判别。三文鱼的碳、硫以及氢、氧稳定同位素具有显著的产地差异。不同组织之间同位素呈现明显的同位素分馏效应。鳞片以及表皮同位素比值对产地的指示效果优于肌肉和骨骼,结果表明采用稳定同位素能完全将以上产地的样品区分开,且还能将中国的虹鳟与进口的三文鱼进行区分。对市场随机购买的6?份三文鱼样品的产地鉴别结果表明,稳定同位素技术能有效鉴别市场中三文鱼的产地造假行为,可用于对市场上三文鱼的产地追溯,以期为我国食品安全提供技术保障。     

Development and validation of protocols to differentiate PCB patterns between farmed and wild salmon

Polychlorinated biphenyl (PCB) congener patterns based on full congener PCB analyses of three farmed and five wild species of salmon from coastal British Columbia, Canada are compared using principal components analysis (PCA) and the best fit linear decomposition of the observed PCB composition in terms of Aroclor 1242, 1254, and 1260 end-members. The two complementary analysis methods are used to investigate congener composition pattern differences between species, trophic levels, feeding preferences, and farmed or wild feeding regimes, with the intent of better understanding PCB processes in both salmon and salmon consumers. PCA supports classification of PCB congeners into nine groups based on a) structure activity groups (SAG) related to the bioaccumulation potential in fish-eating mammals, b) Cl number, and c) the numbers of vicinal meta- and para-H. All three factors are needed to interpret congener distributions since SAGs by themselves do not fully explain PCB distributions. Farmed salmon exhibit very similar congener patterns that overlap the PCA and Aroclor composition of their food, while wild salmon separate into two distinct groups, with chinook and "coastal" coho having higher proportions of the higher chlorinated, Aroclor 1260 type, nonmetabolizable congeners, and chum, pink, sockeye, and "remote" coho having higher proportions of the lower chlorinated, more volatile and metabolizable Aroclor 1242 type, congeners. Wild chinook have the highest PCB and toxic equivalent (TEQ) concentrations, and the highest proportions of A1254 A1260, and PCB congeners in the most refractory SAG. Because both "coastal" and "remote" coho groups are likely to be consuming prey of similar size and trophic level, the PCB delivery mechanism (e.g., atmosphere vs runoff) apparently has more influence on the salmon PCB profile than biotransformation, suggesting that the wild chinook PCB profile is determined by feeding preference. Overall, wild salmon distributions primarily relate to trophic level, feeding preferences, and longevity, while metabolism appears at most a minor factor. The new classification protocol takes better advantage of individual congener PCB analyses and provides a better framework for understanding the PCB distributions in salmon and, potentially, the movement of individual PCB congeners through marine food chains than previous classification schemes.     

Effect of Fish and Oil Nature on Frying Process and Nutritional Product Quality

ABSTRACT: The modifications on a lean fish (cod—Gadus morhua) and a fatty fish (farmed salmon—Salmo salar) after the application of pan-frying using 2 types of oil with different lipid profile (extra virgin olive oil and sunflower oil) was the aim of this study. Fat content and total energetic value increased significantly after the frying process only in the lean fish, without relevant changes in the fatty fish. Extra virgin olive oil led to a higher fat absorption rate than sunflower oil in both fish. Frying hardly affected the lipid profile of farmed salmon regardless the oil used, however it drastically changed in fried cod compared to raw cod. Omega-6/omega-3 ratio increased from 0.08 in raw cod to 1.01 and 6.63 in fried cod with olive oil and sunflower oil, respectively. In farmed salmon, the omega-6/omega-3 ratio was 0.38 (raw), and 0.39 to 0.58 in fried salmon. The amount of EPA + DHA slightly decreased with frying in salmon, and increased in cod. The type of oil has more influence in the nutritional fish quality for the lean fish compared to that of the fatty fish. The use of extra virgin olive oil was efficient to avoid a significant increase of the lipid oxidation intensity during frying in cod but not in salmon. Practical Application: Food modifies its composition and nutritional value with the application of cooking technologies. As most food table composition tables are based on raw food products, this article contributes with interesting data on pan-fried fish composition, which may improve the approach to achieve a real intake of healthy nutrients as omega 3 fatty acids.     

A preliminary comparison of polybrominated diphenyl ether concentrations relative to lipid content and to levels of dioxins and dioxin-like polychlorinated biphenyls in Norwegian farmed Atlantic salmon (Salmo salar)

Polybrominated diphenyl ethers (PBDEs) are environmental contaminants structurally similar to polychlorinated biphenyls (PCBs), and correlations between PBDE concentrations and concentrations of lipid, PCBs, dioxins and furans in feed and farmed Atlantic salmon filet indicate PBDEs may be derived from similar sources. PBDE concentrations (3.9 ± 0.6 ng g^?1 wet wt) in farmed Atlantic salmon correlated well with lipid content and these other halogenated contaminants, however, lower concentrations of PBDEs (1.6 ± 0.3 ng g^?1 wet wt) showed no correlation. Possible explanations for the non‐linear behaviour of PBDE concentrations in Atlantic salmon are discussed.     

Investigation of selected persistent organic pollutants in farmed Atlantic salmon (Salmo salar), salmon aquaculture feed,and fish oil components of the feed

There is extensive literature documenting the bioaccumulation of persistent organic pollutants in the marine environment, but relatively little data are available on contamination pathways in aquaculture systems such as that for farmed salmon. In recent years,the salmon industry has grown significantly in Europe. This study reports on the determination of a wide range of polychlorinated biphenyls (PCBs), organochlorine pesticides, and polybrominated diphenyl ethers (PBDEs) in farmed and wild European Atlantic salmon fish, aquaculture feeds, and fish oils used to supplement the feeds. The study confirms previous reports of relatively high concentrations of PCBs and indicates moderate concentrations of organochlorine pesticides and PBDEs in farmed Scottish and European salmon. Concentrations of the selected persistent organic pollutants varied among the samples: PCBs (salmon, 145-460 ng/g lipid; salmon feeds, 76-1153 ng/g lipid; fish oils, 9-253 ng/g lipid), S DDTs (salmon, 5-250 ng/g lipid; salmon feeds, 34-52 ng/g lipid; fish oils, 11-218 ng/g lipid), and PBDEs (salmon, 1-85 ng/g lipid: salmon feeds, 8-24 ng/g lipid; fish oils, ND-13 ng/g lipid). Comparison of the samples for all groups of contaminants, except for HCHs, showed an increase in concentration in the order fish oil < feed < salmon. Homologue profiles were similar, with an increase in contribution of hepta- and octa-PCBs in the fish, and profiles of DDTs were similar in all three types of samples. With a constant contribution to the total PCB content, the ICES 7 PCBs appear to be reliable predictors of the PCB contamination profile through all the samples. For PBDEs, BDE 47 dominated the profiles, with no significant difference in the PBDE profiles for the three matrixes. Samples with higher PCB contents generally showed higher levels of the pesticide residues, but this was not the case with the PBDEs, indicating the existence of different pollution sources.     

Toxicokinetics and carry-over model of α-hexabromocyclododecane (HBCD) from feed to consumption-sized Atlantic salmon (Salmo salar)

A two-compartmental model for the kinetics of carry-over of the brominated flame retardant α-hexabromocyclododecane (HBCD) from feed to the fillet of farmed harvest-sized Atlantic salmon (Salmo salar L.) was developed. The model is based on a fat compartment for storage of the lipophilic α-HBCD and a central compartment comprising all other tissues. Specific for this model is that the salmon has a continuous growth and that fillet contaminant levels are explained by both the fat and the central compartments. The uptake and elimination kinetics are obtained from experimental data where consumer sized (start weight approximately 1 kg) Atlantic salmon was fed α-HBCD spiked feed (280 ± 11 μg kg(-1)) for 2 months followed by a depuration period of 3 months. The model was used to simulate the HBCD feed-to-fillet transfer in Atlantic salmon under realistic farming conditions such as the seasonal fluctuations in feed intake, growth and fillet fat deposition. The model predictions gave fillet concentrations of 0.2-1.8 μg kg(-1) depending on the level of fish oil inclusion in the salmon diets when using fish oil with high POP background levels. Model simulations show that currently farmed Atlantic salmon can contribute to a maximum of 6% of the estimated provisional food reference dose for HBCD.     

Toxicokinetics and carry-over model of α-hexabromocyclododecane (HBCD) from feed to consumption-sized Atlantic salmon (Salmo salar)

A two-compartmental model for the kinetics of carry-over of the brominated flame retardant α-hexabromocyclododecane (HBCD) from feed to the fillet of farmed harvest-sized Atlantic salmon (Salmo salar L.) was developed. The model is based on a fat compartment for storage of the lipophilic α-HBCD and a central compartment comprising all other tissues. Specific for this model is that the salmon has a continuous growth and that fillet contaminant levels are explained by both the fat and the central compartments. The uptake and elimination kinetics are obtained from experimental data where consumer sized (start weight approximately 1?kg) Atlantic salmon was fed α-HBCD spiked feed (280?±?11?µg?kg^?1) for 2 months followed by a depuration period of 3 months. The model was used to simulate the HBCD feed-to-fillet transfer in Atlantic salmon under realistic farming conditions such as the seasonal fluctuations in feed intake, growth and fillet fat deposition. The model predictions gave fillet concentrations of 0.2–1.8?µg?kg^?1 depending on the level of fish oil inclusion in the salmon diets when using fish oil with high POP background levels. Model simulations show that currently farmed Atlantic salmon can contribute to a maximum of 6% of the estimated provisional food reference dose for HBCD.     

Effects of freezing/thawing on the microstructure and the texture of smoked Atlantic salmon (Salmo salar)

The changes in microstructure and texture during smoking of fresh and frozen/thawed Atlantic salmon was studied in fish from three different origins; ocean-ranched Atlantic salmon (Salmo salar) from Iceland and two groups of farmed Atlantic salmon from northern and western Norway. The muscle fibers from the frozen and thawed fish shrank, and the extracellular space increased compared to the fresh muscle. The muscle fibers from salmon fillets with smaller fiber diameter shrank to a less extent than fibers from salmon material with a larger fiber diameter. After smoking the space between the fibers and the fiber shrinkage increased to a higher extent in the muscle from the salmon that were frozen prior to smoking than muscle smoked from fresh salmon. The initial cross-sectional area of the fibers was not found to be related to the yield during smoking.     

Identification of organically farmed Atlantic salmon by analysis of stable isotopes and fatty acids

Using isotope ratio mass spectrometry (IRMS), the ratios of carbon (δ ¹³C) and nitrogen (δ ¹⁵N) stable isotopes were investigated in raw fillets of differently grown Atlantic salmon (Salmo salar) in order to develop a method for the identification of organically farmed salmon. IRMS allowed to distinguish organically farmed salmon (OS) from wild salmon (WS), with δ ¹⁵N-values being higher in OS, but not from conventionally farmed salmon (CS). The gas chromatographic analysis of fatty acids differentiated WS from CS by stearic acid as well as WS from CS and OS by either linoleic acid or α-linolenic acid, but not OS from CS. The combined data were subjected to analysis using an artificial neural network (ANN). The ANN yielded several combinations of input data that allowed to assign all 100 samples from Ireland and Norway correctly to the three different classes. Although the complete assignment could already be achieved using fatty acid data only, it appeared to be more robust with a combination of fatty acid and IRMS data, i.e. with two independent analytical methods. This is also favourable with respect to a possible manipulation using suitable feed components. A good differentiation was established even without an ANN by the δ ¹⁵N-value and the content of linoleic acid. The general applicability in the context of consumer protection should be checked with further samples, particularly regarding the variability of feed composition and possible changes in smoked salmon.