Towards sustainable fish feed production using novel protein sources

The consumption of fish and fish-related products is increasing. Due to improved welfare and suggested health benefits, consumers are now eating more fish. In 2008, global fisheries supplied the world with about 142 million tons of fish, of which 115 million tons was used as human food, which is an all-time high (FAO, 2010. The State of World Fisheries and Aquaculture. FAO, Rome, Italy). Fish for consumption can be harvested directly from the wild (capture fisheries), but a growing proportion of the fish comes from worldwide aquaculture (FAO, 2010). As a result, there is an increased need for feed for this growing industry. Fish need feed with high levels of protein and energy. Traditionally, for carnivorous or omnivorous fish, these are provided mainly as fish meal and fish oil which are however finite resources and alternative ingredients are needed. Any change in composition is not trivial because fish feed pellets need to fulfil strict technological requirements. When feeding to salmon, the pellet should sink slowly. In addition, the porosity of the pellet directly after extrusion should be such that it can capture sufficient oil. The pellets should not break or produce dust during transport and further handling. This makes the production of feed pellets a delicate process in which the techno-functional properties of the raw materials play an important role. It is not a simple matter to conclude that plant proteins are more sustainable per se if all the renewable and nonrenewable resources and waste emissions related to the production of these ingredients are taken into account. For example, the use of plant-based ingredients might require additional water during extrusion leading to increased drying costs. This thesis describes the relationships between the techno-functional properties of protein-rich ingredients and processing. Criteria have been developed for the use of plant-based materials in existing fish feed processes to allow the production of feed pellets that meet all the product requirements. Feed sustainability is assessed using three different methodologies and sustainable feed compositions are proposed. Future trends in the development of sustainable feeds are described based on the insights obtained from this thesis. These include the use of plant proteins that contribute to a more intensified process with the ultimate goal of no drying and future exploration of the use of algae-derived products with special focus on the replacement of fish oil with algae oil