Very good fat measurements of live salmon

An instrument for measuring fat and pigment in whole fish-farmed salmon has now been assembled and tested out on live salmon with good results. The instrument is based upon optical spectroscopy and is suitable for measuring both live and dead fish.

Contact person
Portrettbilde av Jens Petter Wold
Jens Petter Wold

Senior Scientist
Phone: +47 959 79 749
jens.petter.wold@nofima.no

The development of such an instrument is the primary goal of an R&D project in which a number of companies, namely Skretting, Nordlaks AS, Aqua Gen AS, Pan Fish and QVision AS, have taken significant stakes. All the companies can clearly see the usefulness of such an instrument. In addition to the portion being financed by the companies, the project is also being financed by both the Research Council of Norway and the Fishery and Aquaculture Industry Research Fund. The Project is being co-ordinated by the Industry and Export Section of the Norwegian Seafood Federation Service Office.

Tolerates tough conditions

Sintef ICT has designed and built this instrument in conjunction with Matforsk. The instrument is based upon optical spectroscopy in the visible and near-infrared range (NIR). Even though the instrument is currently a prototype, it is robust and can easily be shipped around within the industry. It is adapted for use under rough conditions, and if a light bulb in the instrument should go out, it is possible to get a new one at the nearest petrol station.

Extremely precise fat measurements

During the course of last autumn, the instrument was tested out on live, slaughtered pre-rigor and post-rigor salmon. Measurements were also made of filets. The results so far show that it is possible to measure the fat content in a whole live salmon with a precision of approx. ± 1 %, which is quite satisfactory. In fact the results for measurements of fat in whole fish are just as good as what is obtained for filets. This is due to the system measuring 10 to 15 mm into the fish, in other words through the skin. In relation to the physiology of the fish and the distribution of the fat, this is a very good point of departure for obtaining good measurements.

Over in seconds

A measurement takes around a second, something that is acceptable when one is handling live fish. The instrument is also being evaluated measuring fat in mackerel and herring. A number of other interesting application areas, including in the meat industry, have also arisen.

Pigment makes for challenges

With respect to the measurement of pigment, such has turned out to be significantly more difficult than fat. The primary challenge is to get enough visible light back from inside the fish to be able to estimate the pigment concentration. Recent changes to the instrument have however also given very promising results for pigment measurements.

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