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.

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.

Improved detection of added water in orange juice by simultaneous determination of the oxygen-18/oxygen-16 isotope ratios of water and ethanol derived from sugars.

A procedure for the analysis of the oxygen-18/oxygen-16 isotope ratio of ethanol derived from the sugars of orange juice using the preparation steps of the SNIF-NMR method followed by pyrolysis-isotope ratio mass spectrometry is presented. The isotopic fractionation induced by the isotope effects of fermentation and distillation have been investigated, and it is shown that reproducible results can be obtained when appropriate analytical conditions are used. It is also shown that the oxygen isotope distribution in the water and organic matter pools of fruits remains quite stable during the harvest period and is not altered by the precipitation rate within the last few days before the fruits are picked. Due to the robustness of the method and the fact that most of the oxygen-18 enrichment from the initial sugars is still present in the end-product, ethanol appears as a convenient internal reference to circumvent the spatial and temporal variability observed for the oxygen-18/oxygen-16 isotope ratio of water. A very strong correlation is observed between the isotopic deviations of ethanol and water, which is altered in the event of a water addition, even at a low level. Combining the information brought by these two parameters leads to a more efficient authenticity testing tool, which avoids false positive cases and provides a lower detection limit for added water in juices not made from concentrate, whatever the origin of the sample tested.