Nofima reports

Rapport/Report 24/2015 - English summary

Langsrud, Solveig

Publication details

Publisher: Nofima AS

Issue: 24/2015

Number of pages: 66

International Standard Numbers:
Printed: 978-82-8296-300-8

Open Access: none

Links:
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The aim of the project was to increase the knowledge needed to obtain more stable quality of norwegian ice-stored salmon fillet. Microbiological growth, sensory changes and consumers’ acceptance of salmon fillet added different potential spoilag bacteria was investgated. Pseudomonas, Photobacterium and Shewanella were identified as the most important spoilers. For heat treated salmon, no significant reduction in consumers’ acceptance were found during storage even at high bacterial numbers, ( up to 109 cfu/gram). However, results from sensory descriptive analysis showed increased intensity of negative odor/flavor attributes in corresponding fillet. Changes in sensory attirbutes were more dominating for raw salmon fillet than for heat treated. A higher hygienic quality did not lead to higher growth of Listeria monocytogenes on ice-stored salmon. It is important to point out the fact that the bacterial numbers in fillet with the same treatment showed variation. This wil also influence the relationship between microbiological growth, sensory changes and consumer acceptance.
Two salmon production plants were visited and samples were taken after cleaning to find sources for spoilage bacteria in the production environment. The results showed that Pseudomonas, and partly Shewanella may survive the cleaning process and contaminate the raw materials. Photobacterium was primarily isolated from the raw material.
The maximum shelf life of ice-stored salmon fillet was 18 days even at low bacterial numbers (<100 cfu/gram) and Listeria monocytogenes (8 kde/gram) at the start of the storage period and optimal storage conditions. Increased oxygen availability or temperature increased the bacterial growth and reduced the shelf life. Since important spoilage bacteria and Listeria monocytogenes in the production environment may contaminate the raw materials better hygiene will lead to a more stable and for some producers, longer shelf life.
The knowledge obtained in the project make it easier for producers to predict shelf life of their own products and to improve the microbial quality of salmon.