Determination of Origin of Atlantic Salmon (Salmo salar): The Use of Multiprobe and Multielement Isotopic Analyses in Combination with Fatty Acid Composition To Assess Wild or Farmed Origin

Abstract

Variability within the stable isotope ratios in various lipidic fractions and the fatty acid composition of muscle oil has been analyzed for a large sample (171 fish) of wild and farmed Atlantic salmon ( Salmo salar) from 32 origins within Europe, North America, and Tasmania. Sampling was extended over all seasons in 2 consecutive years and included fish raised by different practices, in order to maximize the range of variation present. It is shown that two readily measured parameters, delta 15N measured on choline and delta18 O measured on total oil, can be successfully used to discriminate between fish of authentic wild and farmed origin. However, the certainty of identification of mislabeling in market-derived fish is strengthened by including the percentage of linoleic acid C18:2n-6 in the lipidic fraction. Thus, several apparent misidentifications were found. The combination of these three analytical parameters and the size of the database generated makes the method practical for implementation in official laboratories as a tool of labeling verification.

Identification of the farm origin of salmon by fatty acid and HR 13C NMR profiling

“…Also, the fatty acids C18:1n9 and C18:2n6 can be considered as markers for vegetable oils and the latter seems to be the most persistent after a dietary switch (Bell et al, 2001). This affects the restoration of the n3/n6 ratio which is usually higher in wild than in farmed salmon (Martinez, 2006;Thomas et al, 2008). Thus, the difference in the FA profile of farms 2 and 4 can be explained if fish from farm 4 have been receiving the analyzed feed only for the last period of time so that the washing out period from a hypothetical previous feed richer in vegetable oils, had not been completed.…”

“…2 (middle) shows the results of analysing all the fish, both farmed and the free-living. Four of the free-living fish, specimens 505, 510, 511 and 516 displayed the FA composition (high DHA and EPA and low C18:1n9 and C18:2n6) and high n3/n6 ratio characteristic of wild fish (Aursand et al, 2000;Martinez, 2006;Thomas et al, 2008). Of the rest, individuals 502, 508, 509, 512 and 514 clustered close to fish from farm 2; fish numbers 513, 515 and 517 were close to fish from farm 4; and fish 501 and 507 were also close to farm 4 but scored higher than farm 4 on PC1.…”

“…The discrimination of wild from farmed Atlantic salmon has been successfully achieved by a variety of methods, from genetic analysis, often using microsatellite polymorphisms (Coughlan et al, 1998;Glover, Skilbrei, & Skaala, 2008;Skaala, Taggart, & Gunnes, 2005), to stable isotope ratio analysis (d 13 ;Aursand, Mabon, & Martin, 2000;Thomas et al, 2008), gas chromatography analysis of the fatty acids from the triglyceride fraction and 13 C and 1 H HR NMR spectroscopic analyses (Aursand et al, 2000;Thomas et al, 2008). The assignment of individuals to their population of origin by using multilocus genotyping, in particular using microsatellite data, has been proven possible provided that there are enough genetic markers differing among the potential populations of origin (Skaala, Høyheim, Glover, & Dahle, 2004).…”

“…The assignment of individuals to their population of origin by using multilocus genotyping, in particular using microsatellite data, has been proven possible provided that there are enough genetic markers differing among the potential populations of origin (Skaala, Høyheim, Glover, & Dahle, 2004). The analysis of the fatty acid composition of the triglyceride fraction has often been proven to be sufficient to discriminate farmed from wild salmon (Aursand et al, 2000;Martinez, in press;Molkentin, Meisel, Lehmann, & Rehbein, 2007) due to the fact that this lipid fraction reflects the composition of the diet, and the commercial diets have variableand sometimes high -amounts of vegetable oils which are normally absent from the natural feed of wild salmonids (Martinez, 2006;Thomas et al, 2008). Similarly, the HR NMR spectra contain, in addition to the information regarding the fatty acid composition, other relevant parameters such as the positional distribution of the fatty acids and other biochemical compounds, and it has also been proven suitable to discriminate the production method (Aursand, Jørgensen, & Grasdalen, 1995;Martinez, 2006).…”

Color of Salmon Fillets By Computer Vision and Sensory Panel

“…In fact, various means to discriminate between fish of dissimilar origins have been investigated in several previous studies. These have used a range of intrinsic parameters, notably the compositional analysis of fatty acids and the nature of the xanthin pigments present, among other properties (Rezzi et al 2007;Thomas et al 2008).…”