Improved microbial quality and safety of fish

The main objective of the project is to increase the quality and safety of fish through the value chain from harvest/catch to the consumer. Fresh fish has a short shelf life and this limits both the distribution and international trade. The shelf life of fresh fish is limited by microbial and biochemical processes which depend on temperature and storage conditions. The project has participants from three countries; Norway and Iceland are both important seafood producers while France is an important importer of seafood. The project has focused on the farmed salmon and wild cod since these species are the most important species traded in Europe. The aim of the project was to develop new and innovative preservation methods. These include use of protective cultures combined with chitosan film, superchilling and modified atmosphere. Use of protective cultures / chitosan was studied early in the value chain, respectively directly after slaughter and directly after filleting. Combining use of protective cultures and superchilling has not previously been studied and will give possibilities for increased shelf life and safety of the products. In addition improved handling and processing methods may contribute to better preservation of nutrients and sensory quality as well as increased profitability and competiveness of European seafood. An experiment to find out how superchilling influences uptake of salt and smoke has been carried out. Compared to chilled salmon, superchilling gave small changes in the raw material with regard to suitability for salting and smoking. The French partner (IFREMER) has selected the protective cultures to be tested with regard to superchilling and effect on shelf life. Development of volatiles during storage of salmon (in France) has been carried out. Several tests with application of protective cultures before superchilling showed that these survive the superchilling process. The effect of raw material quality on salt absorption in Atlantic salmon was studied in a bachelor thesis in the spring of 2018. Iced, superchilled and frozen salmon were compared. The superchilled salmon differed from the other two groups in having a higher salt uptake. An experiment where salmon was treated with four different protective cultures delivered by IFREMER in addition to a mixture of these in combination with use of modified atmosphere and chitosan pretreatment of the salmon was performed. Especially the last combination had good effect by delaying development of off-flavour during storage. A lactic acid culture that is a good candidate for the large scale test carried out in September 2018 was identified. Salmon was treated with different preservation methods (dipping in chitosan, superchilling and inoculation with lactic acid bacteria) either alone or in combination. Before this experiment could be carried out, preliminary testing with dipping of salmon in chitosan was carried out. Some of the salmon was inoculated with Listeria. The salmon was sent to France where it was salted and smoked and the bacterial growth ? both total plate count, lactic acid bacteria, Listeria and bacterial composition was determined. In addition the sensory quality of the salmon was determined. For cold smoked salmon, chitosan treatment of whole fish after slaughter in Norway combined with treatment with protective cultures after portioning in France reduced the growth of Listeria while chitosan treatment alone had a positive effect on sensory quality. Treatment of salmon with protective cultures combined with superchilling in Norway increased the quality and safety of cold smoked salmon and the effect was even more pronounced with addition of protective cultures after smoking.

The project has given valuable information on the possibilities of reducing the bacterial load on fish using chitosan and on the use of protective cultures to prolong the shelf life of ready to eat fish products. The project has also given valuable knowledge and increased competence on packaging and superchilling of salmon which will benefit the salmon industry. The partners has cooperated in harmonization of analytical methods for analysis of fish quality and safety. This will enable better and analysis and more reliable analytical results.

Norway and Iceland are among the world's leading seafood nations and this has been achieved by increased value adding and knowledge-based management of resources. France is an important producer but also the major European fish importing country. The main challenge remains though in successfully maintaining freshness, quality and value as well as safety of seafood through handling, processing and distribution. Seafood deterioration is mostly governed by microbial and biochemical activities which are influenced by temperature and storage conditions. The main cause of bacterial contamination of fish processing line is due to rapid bacterial proliferation on the skin during early storage which spreads during filleting and by post-contamination during processing. Reducing the microbiota before process and preventing its development during storage will extend shelf life. The main objective of the SAFEFISHDISH project is to improve the microbial and sensory quality and safety of fish from harvest to consumer. The project will focus on farmed salmon and wild cod, which are the major species traded in Europe. Novel handling techniques and combination of innovative preservation technologies involving biopreservatives (protective cultures and chitosan), superchilling and modified atmosphere will be evaluated. Treatment well ahead of the food chain (on the skin upon harvest and on flesh just after filleting) may maximize its efficiency and will be explored. Combination of these preservation techniques is innovative and needs to be tested. Bacterial ecosystem and their metabolism profile will be explored via modern tools such as new generation sequencing (NGS) and various chromatographic methods. Developed innovative handling and processing technologies will better control safety and deterioration of valuable seafood and, simultaneously, contribute to nutritional quality and consumer health as well as increased sales return and competitiveness of European seafood.