R&D applications for aquafeed extrudates: Laboratory scale testing to determine appropriateness for species and sustainability
by Brabender, Germany
Providing a proper supply of protein for the world's continuously increasing population is a tremendous global challenge. Consumption of fish and seafood is traditionally anchored in many dietary cultures and recommended as a significant source of protein for nutritional enhancement.
However, in view of the present situation with overfished oceans around the globe, it is necessary to find alternatives: Here aquaculture provides a solution. Consequentially the global annual yield from aquaculture, amounting to approximately 100 million tonnes since 2015, has outstripped the "wild catch" quantity for human consumption.
Further growth is a foregone conclusion: A 50 percent increase in production is predicted for the next two decades.
Booming aquacultures: Which feed for which species?
We spoke with Julian Foerster (JF) and Michael Landers (ML), the application technicians at Brabender's extrusion laboratory, about using custom tailored extruded products to solve the problems presently faced by the aquafeed industry.
Extruded aquafeed – Where does demand exist?
JF: Whether fish farming with flow-through systems, netcages, or resource-preserving recirculating systems such as aquaponic or offshore farms – all these fish and crustaceans need feed; nearly 40 million tonnes per year worldwide.
70 percent is produced by the leading aquafeed producers in the Asian-Pacific region, particularly in China, 10 percent comes from Latin America, and another 10 percent from Europe. Of course, one has to differentiate among which species should be fed.
Presently 30 percent of production is used for carp breeding, 15 percent is required for crustaceans, followed by tilapia, catfish, salmon, and trout farms.
ML: Extruded products offer trend-setting possibilities promising market success and product innovation in developing the proper feed for each species on a practical basis. There is practically no other process that offers so much potential for entirely reshaping an aquafeed matrix.
For this reason purely mechanical pelleting presses have been increasingly replaced by state-of-the-art extrusion technology for production. Today, laboratory extruders are therefore necessary "tools" for product developers in companies as well as at universities and research institutes. With the TwinLab-F 20/40, Brabender has now introduced its current top model for the R&D laboratory world.
What is the "proper" feed for a species?
JF: First, we need to determine the raw materials and their percentage of protein and carbohydrate that are practical for various product applications. It is first necessary to determine the tendency of the feed to float or sink, depending on the feeding habits of the specific type of fish.
In principle, floating feed tends to be eaten by bottom fish such as carp and catfish, which can also be a matter of training. Salmon and trout prefer feed that sinks slowly, shrimp, by contrast, like food that sinks quickly.
ML: Correspondingly, it is necessary to select different process settings for production. For floating feed, including suspended or slowly sinking feed, we operate with hot extrusion at temperatures over 100°C. This results in good pellet expansion. For sinking feed, i.e. production of quickly sinking pellets with minimum expansion, cold extrusion is the preferable method.
Which challenges need to be solved in the laboratory?
ML: Whether or not a product expands depends, among other things, on the moisture content as well as generally from the recipe, particularly the percentage of protein, carbohydrates, and fat in the initial mixture, which is also varies ichthyologically depending on the species.
As a product developer we can determine this precisely in the laboratory. The TwinLab allows us to put various compositions and recipes on the test bench. The degree of expansion can be adjusted and changed with variable process settings.
Most important is optimal cohesion of the constituents to prevent the pellets from disintegrating. This allows us to test the product characteristics to ensure the recipes are properly adapted to the type of fish and farming method.
For example, some species require a high percentage of fat in the feed, however, too much oil delays expansion - here we can examine possible maximums using the TwinLab. And naturally, the reverse is true, when it is necessary to determine the minimum quantities of ingredients, e.g. for optimisation of the sinking characteristics. This can be regulated by adding water, among other things, whereby the pellets are then dried.
JF: For forward-looking, sustainable product design – keyword: Sustainability – the trend is departing from use of fish meal or byproducts from commercial fishing. Instead, it is necessary to study which sources of protein with which characteristics and percentages are compatible with extrusion.
Which alternative sources of raw materials do you believe have potential for practical application for aquafeed extrusion?
ML: In our applications laboratory we have already gathered a great deal of experience in product development. Particularly with meal and groats from legumes - not just soy, but also peas and lupines, or greater use of classic sources of protein and carbohydrates such as corn, wheat, and rice.
In view of the world nutritional situation, these can be used more efficiently as aquafeed than for feeding domestic animals. And considering the limited amount of acreage available for vegetable raw materials, byproducts from cereal grains should be investigated as ingredients for aquafeed.
For example, I'm thinking here of cereal brans from mills or corn gluten from the starch industry. Other obvious applications are marine plants such as algae or kelp as high protein sources of nutrition for fish farms: Here, it would be possible to clarify on a laboratory scale which percentages in a fish feed mixture are suitable for extrusion or how this can be optimised technologically.
JF: Insect proteins provide one perspective for research and development in the area of aquafeed. At the Brabender applications laboratory, we have conducted our own tests with the objective of replacing fish meal with insect protein consisting of Hermetia illucens (black soldier fly) as a raw material. Initial results are quite promising: In terms of the rheological parameters for extrusion as well as the nutritive feed properties of the extruded products, regardless of whether in pellet or ground form.
Particularly in the East-Asian markets, I see good perspectives for this, because traditional dietary customs do not have reservations regarding use of insects in menus.
What can the new TwinLab do for lab scale extrusion?
ML: Well, I could go on for hours about that. But I want to emphasise two main arguments for practical product development with laboratory extruders such as the TwinLab instead of experimental manipulation of the production process.
For one, you can vary your application ideas in a wide variety of ways with regard to raw material, formulation, extruder configuration, and product. Secondly, you have the option of establishing methods for measuring your quality parameters in advance from the raw material to the final product. With a width of 60 centimeters, our new TwinLab also fits in even the narrowest of laboratories.
JF: The range of applications focuses mainly on recipe and product development or serves for optimisation of production processes. The new TwinLab is a laboratory-sized twin screw extruder.
We have used it to test products with a wide range of shapes, colors, and flavors. During development, it was important to us to be able to adhere to realistic processing conditions. This reduces costs for our customers and is consistently quality-oriented.
You require significantly less time for your tests, save on material, and have almost no product wastage. And last, but not least: In everyday production, you do not need to worry about any negative effects to your ongoing quality management system. This allows a return on investment to be realised easily at the company.
Where do you see application-related advantages for product development?
ML: Along the length of the liner, four heating and cooling zones provide optimisable temperatures in every process area. Screw speeds of up to 1200 revolutions-per-minute offer users great flexibility with regard to specific mechanical energy, called SME for brevity.
As a twin screw extruder, the TwinLab allows processing of a wide variety of raw materials, as well as analysis of their viscosity and plasticity characteristics. This is because all conveying, kneading, and mixing elements can be configured individually depending on the process sequence.
The module design allows variable configuration for product simulation with different shear forces, making the device suitable for highly varying applications. And finally, I would like to mention one more important feature for everyday use in the laboratory: The process unit is separated horizontally and can be folded up vertically – which only few comparable models on the market offer. This not only allows for visual evaluation of individual processing steps, but also provides for convenient screw removal and fast cleaning.
JF: For aquafeed applications, we have produced primarily cylindrical pellets, or expanded products with the round die head – and an additional cutting device. The four upper and two lateral metering openings on the TwinLab also allow liquid or granulated additives such as oils, vitamins, and mineral concentrates or colors to be fed in.
For example, I'm thinking here of omega-3 fatty acids or carotenes, which are of enormous importance for aquafeed producers and their suppliers. In the area of research and development, there are many cooperative projects between science and industry, which Brabender is proud to support the aquafeed of the future with its extrusion-related expertise.
But even more: We would like to invite customers to visit our Customer and Technology Center in Duisburg and see the capabilities of our lab-scale extrusion and experience the new TwinLab in operation for themselves.