Processes affecting the post-harvest spoilage of salmon muscle

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Whereas meat often must be stored for a certain period of time to allow muscle-tissue breakdown (conditioning) to occur, fish meat is already conditioned enough at slaughter. The salmon-processing industry thus faces the challenge of retarding these processes in order to keep the processed fish fresh as long as possible.

Averøy Photo: Akvaforsk

We already know that low temperatures and stress avoidance before slaughtering help to delay the breakdown of salmon muscle, but very little is known about the physiological and biochemical processes resulting from these treatments.

The Department of Animal and Aquacultural Sciences coordinates an extensive strategic university project, in which several research teams from various institutes in Ås (Matforsk, AKVAFORSK and IMT ) are cooperating to: a) learn more about the processes involved in salmon muscle breakdown after slaughtering, b) develop ways to affect these processes and c) use this knowledge in product development.

In September, several of us spent some days at AKVAFORSK’s research station near Kristiansund on Norway’s north-western coast (see photo). There we extensively studied the effect of different stress levels on the onset and duration of rigor mortis in salmon and how this was linked to changes in muscle texture (histological examinations under a microscope), enzymatic activity and changes in a variety of meat quality traits. By optimizing the treatment of salmon prior to slaughter, the time until the onset of rigor mortis can be increased. This allows pre-rigor processing. It has been shown that pre-rigor fillets have a different quality than post-rigor fillets, e.g., pre-rigor fillets have a redder colour. This is important, since red meat colour is an important quality parameter in salmon. Other properties of the pre-rigor fillet are also different, which makes it necessary to adapt further processing, e.g., smoking.

The project will last for several years, and we will thus be able to present results from these and other joint experiments in later issues of this newsletter.

Published: 01.11.08
Updated: 08.01.09
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