Minced fish products containing bacteria from the Anisakis parasite have a longer shelf life than similar products without these bacteria. The reason could be that increased competition between a number of bacteria slows down their development, according to a new PhD thesis.

In her PhD project, Cecilie Smith Svanevik has studied microorganisms in pelagic fish and how they can improve the shelf life of fish products. The underlying objective is to contribute to the increased utilisation of fish resources and to reduce post harvest loss.

Among other things, Svanevik has studied how the larvae of the parasitic Anisakis nematode affects the shelf life of fish meat. These larvae are parasites that the fish consumes through its feed, and they might migrate from the fish’s intestines and into the muscle tissue. Svanevik studied whether the Anisakis larvae carried bacteria with it from the intestines and, if so, how this affected the muscle tissue. She made mince from fillets with no Anisakis infections and then added bacteria from the Anisakis larvae in different dosages.

Her hypothesis was that fish mince without Anisakis would keep the longest. That was not the case, however. The minced fillets containing Anisakis kept significantly longer than those without the parasite. This result surprised Svanevik, who thinks that more bacteria in the mince leads to increased competition between the bacteria and that they therefore develop more slowly.

Svanevik has also studied how freshly caught mackerel was affected by being transported through the pump system bringing the fish from the purse seine to on-board storage tanks. Bacteria found in the intestines of the fish in the purse seine were later found on the gills and skin of fish in the storage tank. The conclusion is that some of the intestinal content is squeezed out of the fish during transport and can subsequently be found on the gills and skin of surrounding fish. This has little impact on food safety, but lowers the storage quality of the products made from the fish.

Cecilie Smith Svanevik, born in 1984, lives in Bergen, but grew up in Valestrand on Osterøy. She completed her master’s degree in biology at the University of Bergen in 2010.

Today, Svanevik defended her PhD thesis from the University of Bergen entitled ‘Microbiological aspects of fish handling and processing in the Norwegian pelagic sector’.

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