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.</p

Wheat gluten in extruded fish feed: Effects on morphology and on physical and functional properties

This article focuses on understanding the role of vital wheat gluten on the structural parameters of extruded fish feed and its correlation to the physical and functional properties. Gluten–soy protein concentrate blends with five gluten concentrations (0–200 g kg-1) were produced. An abrupt reduction in oil uptake was observed with the 200 g gluten kg-1 blend. Inclusion of gluten from 100 to 200 g kg-1 resulted in unacceptable product properties. Sinking of feed pellets with 0 and 50 g gluten kg-1 was 100%, whereas only 36% of pellets with 200 g gluten kg-1 sank. We suspect that this is due to a relationship between morphological structure and oil impregnation during coating of feeds. The addition of gluten at 200 g kg-1 gave a smoother and non-porous outer surface. Pellets without gluten had a larger number of cells that were smaller than 200 µm (P <0.05) compared with pellets with 100 and 200 g gluten kg-1. More spherical cell shapes (P <0.01) and a compact structure were favoured in the presence of gluten. The closed porosity increased (P <0.05), whereas interconnectivity between pores decreased (P <0.01), with increasing gluten content from 0 to 200 g kg-1. The effects of the addition of gluten are probably related to the film-forming properties of gluten

Wheat gluten in extruded fish feed: Effects on morphology and on physical and functional properties

This article focuses on understanding the role of vital wheat gluten on the structural parameters of extruded fish feed and its correlation to the physical and functional properties. Gluten–soy protein concentrate blends with five gluten concentrations (0–200 g kg-1) were produced. An abrupt reduction in oil uptake was observed with the 200 g gluten kg-1 blend. Inclusion of gluten from 100 to 200 g kg-1 resulted in unacceptable product properties. Sinking of feed pellets with 0 and 50 g gluten kg-1 was 100%, whereas only 36% of pellets with 200 g gluten kg-1 sank. We suspect that this is due to a relationship between morphological structure and oil impregnation during coating of feeds. The addition of gluten at 200 g kg-1 gave a smoother and non-porous outer surface. Pellets without gluten had a larger number of cells that were smaller than 200 µm (P <0.05) compared with pellets with 100 and 200 g gluten kg-1. More spherical cell shapes (P <0.01) and a compact structure were favoured in the presence of gluten. The closed porosity increased (P <0.05), whereas interconnectivity between pores decreased (P <0.01), with increasing gluten content from 0 to 200 g kg-1. The effects of the addition of gluten are probably related to the film-forming properties of gluten

Assessment of the effects of fish meal, wheat gluten, soy protein concentrate and feed moisture on extruder system parameters and the technical quality of fish feed

Evaluation of feed ingredient functionality plays a vital role in modern fish feed manufacturing practice. The aim of this study was to examine the extrusion behaviour of blends containing alternative protein sources from plant origin to fish meal (FM), such as wheat gluten (WG) and soy protein concentrate (SPC), and the consequences for the physical attributes of the resulting feed extrudates. A mixture design was applied, varying the levels of protein sources included in the formulation from 50 to 450 g kg-1. Each diet was produced with added feed moisture content of 20, 26 and 32 g/100 g (wet basis). The partial least squares regression models were fitted and their performance was evaluated on the basis of R2 and the root mean squared error of cross-validation over the complete data set. A higher inclusion level of FM in the diet decreased the values of the extruder system parameters, such as torque, pressure at the die and melt temperature. In contrast, inclusion of SPC significantly increased the values of these extruder-related parameters. The viscoelastic properties of WG gave higher radial expansion; FM showed the opposite effect. The results show that the feed moisture was the dominant factor for extrudate density and oil absorption capacity. Products with higher breaking strength were observed with increasing levels of WG and SPC. Combining the product requirements for both extrudate density and hardness showed that the largest optimal compositional range is available at low feed moisture content. However, maximum FM replacement is possible at high feed moisture conten

Lupine and rapeseed protein concentrate in fish feed: a comparative assessment of the techno-functional properties using a shear cell device and an extruder

The techno-functional properties of soy, lupine and rapeseed protein concentrates (SPC, LPC and RPC, respectively) in fish feed were evaluated relative to fish meal (FM). The effects were studied using a shear cell device and an extruder with emphasis on the added moisture content. Six diets were formulated: an SPC-based diet with 300 g SPC kg-1, diets containing 100 and 200 g LPC kg-1 or 100 and 200 g RPC kg-1 and an FM-based diet with 450 g FM kg-1. Each diet was extruded with an added moisture content of 29%, 25% and 22% of the mash feed rate. It was found that the technological properties of LPC closely resemble FM, being high solubility, low water-holding capacity (WHC) and low paste viscosity. The LPC 100 and 200 g kg-1 diets could be extruded at 22% moisture, which gives an extrudate with reduced drying requirements. In addition, less specific mechanical energy was needed for extrusion. In contrast, both SPC and RPC have high WHC and paste viscosity. This explains the higher feed moisture required during extrusion. The properties of the feeds containing RPC could be well within the ranges acceptable for commercial fish feed use at even higher moisture content compared with SPC. The results of the extrusion trials confirmed the observations made from the shear cell device. Thus, the shear cell device can be used to study processing conditions that are close to extrusion conditions

Lupine and rapeseed protein concentrate in fish feed: a comparative assessment of the techno-functional properties using a shear cell device and an extruder

The techno-functional properties of soy, lupine and rapeseed protein concentrates (SPC, LPC and RPC, respectively) in fish feed were evaluated relative to fish meal (FM). The effects were studied using a shear cell device and an extruder with emphasis on the added moisture content. Six diets were formulated: an SPC-based diet with 300 g SPC kg-1, diets containing 100 and 200 g LPC kg-1 or 100 and 200 g RPC kg-1 and an FM-based diet with 450 g FM kg-1. Each diet was extruded with an added moisture content of 29%, 25% and 22% of the mash feed rate. It was found that the technological properties of LPC closely resemble FM, being high solubility, low water-holding capacity (WHC) and low paste viscosity. The LPC 100 and 200 g kg-1 diets could be extruded at 22% moisture, which gives an extrudate with reduced drying requirements. In addition, less specific mechanical energy was needed for extrusion. In contrast, both SPC and RPC have high WHC and paste viscosity. This explains the higher feed moisture required during extrusion. The properties of the feeds containing RPC could be well within the ranges acceptable for commercial fish feed use at even higher moisture content compared with SPC. The results of the extrusion trials confirmed the observations made from the shear cell device. Thus, the shear cell device can be used to study processing conditions that are close to extrusion conditions

Sustainability assessment of salmonid feed using energy, classical exergy and eco-exergy analysis

Reduction of the environmental impact of feed products is of paramount importance for salmon farming. This article explores the potential to compare three thermodynamically based ecological indicators. The environmental impact of partial replacement of fish meal (FM) and fish oil with alternative ingredients was investigated using energy, classical exergy and eco-exergy analysis. Seven hypothetical feeds were formulated: one with high levels of FM and fish oil, four feeds based on plant ingredients, one containing krill meal, and one based on algae-derived products. Analysis included cultivation of crops and algae, fishing for fish and krill, industrial processing of these ingredients and production of complete fish feed. Because most harvested products are refined in multiple product outputs that have good value to society, two scenarios were compared. In the base case scenario, no allocation of co-products was used and all the environmental costs were ascribed to one specific co-product. Co-product allocation by mass was used in the second scenario; this is considered to be the preferred scenario because it accurately reflects the individual contributions of the co-products to the environmental impact of the feed products. For this scenario, the total energy consumption for a fish-based diet was 14,500 MJ, which was similar to a krill diet (15,600 MJ), about 15–31% higher than plant-based diets, and 9% higher than an algae diet. Substituting FM and fish oil with alternative ingredients resulted in minor changes in total classical exergy degradation (2–16% difference). The calculations based on energy only consider the energy conservation based on the First Law of Thermodynamics, whereas those based on classical exergy also takes the Second Law of Thermodynamics into account; energy that can do work is distinguished from energy that is lost as heat to the environment. The calculations based on eco-exergy consider the total loss of work energy in the environment including the work energy associated with the information embodied in the genomes of organisms. The diet based on fishery-derived ingredients was the highest total work energy consumer compared with plant-based diets (24–30% greater), the diet containing krill meal (25% greater), and the algae diet (four times higher). Thus, reducing FM and fish oil levels in fish feed can contribute significantly to more sustainable aquaculture. In particular, algae-derived products in aquafeeds could drastically decrease environmental costs in the future

Sustainability assessment of salmonid feed using energy, classical exergy and eco-exergy analysis

Reduction of the environmental impact of feed products is of paramount importance for salmon farming. This article explores the potential to compare three thermodynamically based ecological indicators. The environmental impact of partial replacement of fish meal (FM) and fish oil with alternative ingredients was investigated using energy, classical exergy and eco-exergy analysis. Seven hypothetical feeds were formulated: one with high levels of FM and fish oil, four feeds based on plant ingredients, one containing krill meal, and one based on algae-derived products. Analysis included cultivation of crops and algae, fishing for fish and krill, industrial processing of these ingredients and production of complete fish feed. Because most harvested products are refined in multiple product outputs that have good value to society, two scenarios were compared. In the base case scenario, no allocation of co-products was used and all the environmental costs were ascribed to one specific co-product. Co-product allocation by mass was used in the second scenario; this is considered to be the preferred scenario because it accurately reflects the individual contributions of the co-products to the environmental impact of the feed products. For this scenario, the total energy consumption for a fish-based diet was 14,500 MJ, which was similar to a krill diet (15,600 MJ), about 15–31% higher than plant-based diets, and 9% higher than an algae diet. Substituting FM and fish oil with alternative ingredients resulted in minor changes in total classical exergy degradation (2–16% difference). The calculations based on energy only consider the energy conservation based on the First Law of Thermodynamics, whereas those based on classical exergy also takes the Second Law of Thermodynamics into account; energy that can do work is distinguished from energy that is lost as heat to the environment. The calculations based on eco-exergy consider the total loss of work energy in the environment including the work energy associated with the information embodied in the genomes of organisms. The diet based on fishery-derived ingredients was the highest total work energy consumer compared with plant-based diets (24–30% greater), the diet containing krill meal (25% greater), and the algae diet (four times higher). Thus, reducing FM and fish oil levels in fish feed can contribute significantly to more sustainable aquaculture. In particular, algae-derived products in aquafeeds could drastically decrease environmental costs in the future