From Biology to Quality (BQ): – creating the linkage between live fish and fish products

“Quality is never an accident; it is always the result of high intention, sincere effort, intelligent direction and skilful execution; it represents the wise choice of many alternatives.” (William A. Foster) The quality of fish meat is dependent upon a wide range of biological and non-biological factors. The idea that pre-harvest have an impact on the post-harvest quality is a research field, which are gaining more and more focus in livestock production. Investigating biological markers in live fish will make prediction of a quality parameter in the finale product possible. The basis for the presented work was to investigate, if previous disease history can be directly linked to known quality parameters in fish. Controlled in vivo experimental laboratory setups and field trails were conducted using both a mechanical damage and a bacterial infection model. From field trails a certified sensory panel examined the quality of fish with focus on textural parameters. Furthermore in vitro experiments were conducted with a rainbow trout fibroblast cell line (Rainbow trout hypodermal fibroblasts, RTHDF) to investigate the biochemical aspects of the question raised. Experimental results have clearly established, that the immunological reactions following damage or infection are local and dependent on reaction of local placed cells. Furthermore, also systemic reactions following damage or infection have been investigated and compared with the local reactions. Following the immunoreaction consequent damage or infection the tissue regeneration also implied, that the local responses are of immense importance for these immune processes. Using a challenge method with Vibrio anguillarum it was established that textual chances in the fish meat occur in rainbow trout as a result of prior bacterial infections. The changes found in the fish meat indicated formation of scars in affected tissue during the processes of tissue repair, which gave rise to a more fibrous, tougher and flaky texture of the fillets. The textural changes could be adverted by cold smoking of the fillets. Investigation of biochemical parameters showed changes between local areas of a damaged/infected and undamaged/uninfected fish with respect to gen expression of genes involved in tissue healing as collagen-1α. In conclusion the immune reactions and tissue regeneration processes have a clear impact on product quality measured as texture. Furthermore, it was demonstrated that processing such as cold smoking could advert the negative effects of previous infection or damage history on the final meat quality. Thus, implying the importance of knowledge of the biological quality for an optimal utilization of the end product.