| Summary: | The Norwegian whitefish industry has long traditions and constitutes an important part of both economy and food production. Whitefish is a collective term for several lean fish species, the most important being cod (Gadus morhua) and saithe (Pollachius virens). Processing of whitefish generates substantial amount of rest raw materials (RRM) that are mainly used for animal feed, biofuels or wasted. However, in order to meet the growing demand for nutrition, while simultaneously protecting our environment, we need to change the way we produce food. Whitefish RRM is a source of several nutritional components, including high-quality proteins, that can be used for human consumption as part of a sustainable food production. The aim of this thesis was to present a systemic and innovative approach to the Norwegian whitefish industry and the objective of improving the utilization of whitefish RRM generated during catch, landing, and processing. This approach involved the use of two paths of obtaining knowledge, and the combinations of those, to get a thorough understanding of the current potential for improved utilization of whitefish RRM. The first path involved the use of laboratory experiments to evaluate the effect of spawning on saithe RRM, the potential for upscaling biotechnological processing for bulk production of protein products and the refinement of these to increase bioactive properties. The second path involved a case study within the Norwegian whitefish industry to investigate how experiences, attitudes and practices among fishers, and the circumstances affecting these, could enable or complicate efforts to improve utilization of RRM. The knowledge obtained from the laboratory experiments and the case study were then combined in an overall evaluation. Saithe RRM mainly consist of heads, backbones, and viscera. Spawning did not affect the nutritional composition of heads and backbones. These RRMs are also relatively stable compared to viscera and were selected for further processing. Processing of saithe RRM involved mincing, enzymatic hydrolysis and membrane ultrafiltration. Enzymatic hydrolysis in bioreactors enabled extraction of RRM protein content to a high-quality saithe protein hydrolysate (SPH). Regarding processing equipment, a need for powerful and energy-efficient solutions for mincing, agitation, and dewatering were identified. SPH was further processed by membrane ultrafiltration to concentrate small peptides, which are associated with several health beneficial bioactive properties including the ability to work as antioxidants. Spawning neither affected the quantity and quality, nor the antioxidative activity of SPH. Membrane ultrafiltration enabled a concentration of small peptides but did not increase antioxidative activity compared to SPH. Significant amount of the RRM protein content ends up in the secondary products of processing, which makes it important to find areas of applications for these as well. Eight interviews with fishers of the whitefish industry resulted in the creation of three main themes. These concerned the term sustainability and its interpretation, the fragmented organization of the value chain, the development and implementation of regulations, and how this can affect rationalization, behaviour, and attitudes among fishers. This thesis has identified logistical, technological, and sociocultural factors, in addition to factors concerning the raw material itself, that could affect the potential for improved utilization of whitefish RRM. While the availability and seasonal stability of saithe RRM could positively affect this potential, insufficient processing solutions, communication, management, and organization of the value chain could have a negative effect. This work does not provide a final solution, nor an all-encompassing truth, but can inspire other natural scientists to look beyond the limitation of traditional research methods and see the value in adopting and developing new methods for obtaining knowledge. Knowledge that could contribute to a sustainable development within the Norwegian whitefish industry, but also on a global level.
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