| Summary: | Norway is the world largest producer of Atlantic salmon (Salmo salar). In 2013 the Norwegian aquaculture industry produced 1.2 million metric tons salmon with the use of 1.5 million metric tons of commercial feeds. The feeds are delivered to the farms in big bags or in bulk and are conveyed pneumatically to the sea cages. Such harsh treatments expose pellets to stress that may give product loss due to abrasion and fragmentation. Feed loss in pneumatic feeding systems is estimated to be in the range of 0.3% to 1.5%. This equals a yearly additional expense of around 40 to 200 million NOK for the Norwegian salmon industry. To minimize product loss the feed has to be of a consistent and high physical quality. Extrusion processing is a technology that enables production of such feed quality. Physical pellet quality is normally improved by the addition of starch and other binders, but recent research has shown that the protein ingredients in the feed mix also impact the physical quality of extruded feed products. During the last decade several new plant derived protein ingredients has been introduced and partly replaced fishmeal. This has introduced new challenges in fish feed extrusion and stressed the importance to improve the knowledge related to the technical properties of the individual ingredients. The main objectives of this work have been to quantify fishmeal physicochemical properties with significant effects on the extrusion cooking process and physical pellet quality, and to study the plasticization effect of water solubles in fishmeal. Various multivariate analytical techniques have been applied in the studies, such as principal component analysis, partial least squares -and multiple linear regression. In Paper I and II, the impact of variation in fishmeal physicochemical properties were assessed based on standardized extrusion, drying and coating conditions. In Paper III the effect of water-soluble protein level and moisture content on the extrusion process, extrudate phase transitions and physical ...
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