Quality of rainbow trout farmed at sea – shelf life (QIM), fillet colour and muscle texture

Summary

Today, the production time in the sea, for producing roe from rainbow trout, takes from 1,5 to 2 years. It is useful to investigate new production regimes, trying to reduce the time in the sea. However, before a new production regime is introduced on rainbow trout, it is important to map quality changes during ice-storage. Our output hypothesis is that rainbow trout, kept for approx. 1 year in sea (3 kg), does not distinguish significantly from the larger, roe-carrying trout (>6 kg) who has been kept at sea during 1.5 to 2 years. This applies to its shelf life, muscle texture and flesh colour. The QIM-analysis shows that if the trout is sufficiently chilled (0-1 ⁰C), the shelf life equals approx. 20 days after slaughter. The filet colour (SalmoFan values) in this study is relatively low (28-29), compared to SalmoFan scores from earlier studies (32-33). The results also show that filet pigmentation, during ice-storage, may reduce with a score of 1-2 SalmoFan within two weeks. When investigating the muscle structure, the pull to remove the pin bones from the filet is significantly lower than what has been found earlier regarding larger rainbow trout. However, the result shows that the pull seems to remain stable throughout ice-storage. This is also in accordance with the results form textural analysis. These results indicate that the muscle texture in rainbow trout is relatively stable throughout the 20 days of ice-storage.