Feed additive with triple benefits

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By Rob Fletcher

The additive can contribute to reducing the loss of feed in the aquaculture industry, and make the production of feed more energy-efficient. The process additive is a protein-based solution that can be manufactured from marine raw materials or plant proteins. Approximately 1.5 million tonnes of feed are used for Norwegian farmed salmon every year. All of this feed is blown through long tubes into the fish cages, and it is extremely important, therefore, that the feed is manufactured to withstand the mechanical load it experiences. If this is not the case, the feed breaks up into small particles and dust, which the fish cannot eat, and the dust may also clog the feed-supply system. The loss in such feed delivery systems lies in the range 0.3-1.5%, which corresponds to an additional annual cost of between NOK 40 and 200 million. In order to reduce the loss, the feed must be homogeneous and have good physical properties. PhD student Tor Andreas Samuelsen at the Nofima Feed Technology Centre in Bergen has studied how the loss can be reduced by measures taken during the feed processing. The principal goal of the project has been to divide fishmeal into its components, identify which of these influences the extruder, and determine their significance for the physical properties of the final fish feed. Extrusion is a rapid kneading and cooking process that can be compared to baking bread in the kitchen at home. It is the most commonly used technology for the production of feed for salmon. The physical properties of the fish feed can be controlled and improved by adding starch and other binding agents. However, the proteins in the feed also contribute to how well the pellets maintain their structure. An increasing amount of the proteins in commercial fish feed come from the plant kingdom, and the fraction of proteins from marine raw materials is decreasing. This raises new challenges, and more knowledge about the technical properties of the ingredients used in fish feed manufacturing is required. Samuelsen’s doctoral work has shown that positive properties are associated with water-soluble low-molecular-weight proteins in the fishmeal (small peptides and amino acids). Such proteins are pressed out together with water during the manufacture of fishmeal. The water that is pressed out is called stickwater, and has a positive nutritional value.

“We have shown how such proteins function during the manufacture of fish feed, and we have identified which type of proteins give the desired effect. This means that we can use them better, not only to make the processing from raw material to pellet easier, but also as binding agent and nutritional component,” says Samuelsen.

Component functions Fish feed is manufactured by mixing the ingredients in powder form, extruding the mixture with the addition of water and heat, and drying the pellets. Oil is then added and the product is packed. More water must be added when manufacturing feeds with high contents of vegetable proteins than those with high contents of fishmeal. This means that more water must be subsequently removed when the pellets are dried, which increases the energy consumption by approximately 30% compared with a traditional feed based on fishmeal. The process additive that Nofima has developed has several of the same properties as water. These water-soluble components with low molecular weights can, therefore, replace some of the water that is added during the process, and in this way reduce energy consumption. The knowledge may also contribute to reducing the need for reprocessing of feed and give fewer complaints arising from poor physical properties of feed.

Fishmeal properties Several experiments at Nofima have shown that fishmeal is one of the most variable ingredients used in the production of feed. And Samuelsen’s PhD work documented the properties of fishmeal that makes it unique, and different from plant proteins, something that the industry has acknowledged. This knowledge can be used to improve the properties of plant proteins.

Here he explains to Fish Farming Expert the possible significance of his research:

How revolutionary/ground-breaking is your research? It is the first time that the effect of water-soluble protein has been documented for use as a processing aid in fish feed extrusion and the underlying mechanism explained.

What are the main challenges you’ve encountered? The main challenge has been to establish the experimental and analytical platform that enabled us to document and explain the product properties.

What are the main breakthroughs you’ve made? The main finding is that water-soluble proteins have several of the same properties as water. Low molecular weight water-soluble proteins can replace some of the water that is added during feed processing. This will reduce energy consumption during drying of the feed pellets.

What are the marine raw materials that you’ve been using? In principal any fish raw materials can be used. What percentage of the feed is the additive likely to make up? This will strongly depend on the feed formulation but we expect practical inclusion levels lower than 10%.

Is the additive expensive to produce? The research activity has mainly focused on the explaining of the underlying mechanism behind the processing aid and binding agent. Estimation of the production costs has not been a part of the project.

How much energy could it save (in terms of reducing drying costs for plant-based feeds)? This will depend on the feed formulation and inclusion level.

Has your work generated interest from feed or salmon producers in Norway? The work has generated interest from fish feed producers but also from the industry that supply ingredients to the feed industry.

Does the greatest promise for your new substance relate to its role as a binding agent, for its nutritional value, or for its ability to produce feed ‘with good physical properties’? As other binders have zero to low nutritional value I think the concept “with triple benefits” is the best answer.

The research project has been carried out as a doctoral degree project in collaboration with the Department of Chemistry at the University of Bergen. Åge Oterhals (Nofima) has been principal supervisor, and Svein Are Mjøs (Department of Chemistry) co-supervisor. The project has been supported by the fishmeal industry in Norway and the Norwegian Seafood Research Fund (FHF).