Protein Shifting by Dry Fractionation

Our process involves a combination of fine grinding and subsequent separation by means of sifting with high-performance machines. In this way, the proteins in raw materials such as wheat and legumes can be separated purely mechanically from the starch particles they contain and enriched in the fine fraction. The deciding factor here is the difference in size between the components, with starch granules, at 15 to 40 µm, being significantly larger and, above all, more resistant to grinding than proteins, which have diameters of around 3 µm. The protein-rich special flours and concentrates obtained through the protein shift are then used as the basis for further processing steps such as extrusion into schnitzels, grits and other meat substitute products.

The concentration of the protein concentrates that we obtain is below that of isolates, at over 85 percent. However, our method is purely mechanical and dry. In contrast, isolates are produced in a complex wet-chemical process that consumes large amounts of water, acids and other chemicals. But we not only save resources, our energy consumption has also been reduced by a factor of ten. Another point is flexibility. A variety of different types of impact mills are available, including the space-saving Contraplex CW II pin mill combined with the ATP air classifier or the ZPS classifier mill for the most exacting fineness requirements. Among other things, easy, straightforward maintenance was also designed into both of them. While the door of the CW mill can be opened to the front, the top section of the ZPS is swung open hydraulically. These parts can usually no longer be dismantled by hand due to their weight, especially in the case of large machines.

Above all, the machines can be dynamically adjusted depending on the desired purity and grain size of the end product. The individual motors are equipped with frequency inverters, which makes it easy to adjust the speed via the control system. This way, various finenesses, protein contents or throughputs can be set and adapted to the respective requirements. After all, natural products and non-standardised raw materials are processed. The wide range of settings allows the optimum grinding fineness to be achieved and maintained for each product.

The temperature increase depends on the desired fineness. However, an air stream is simultaneously routed through the system, which promotes the targeted discharge of the particles. At the same time, this ensures that relatively little heat is transferred to the product. At ZPS, for example, temperatures between 10 and 20 degrees Celsius would normally be expected. However, raw materials with a high natural oil content and little starch, such as those found in soy beans, pose a general challenge when it comes to obtaining protein concentrates. Sweet lupins are a borderline case, depending on the variety. Although chickpeas are also legumes, they only contain four to six percent fat and can therefore be processed using our processing method. This also applies to field beans. The centrifugal forces acting on the two pin discs of the mill ensure that even products containing fat can be processed up to a certain level.

It should also be mentioned in this context that our process only uses pre-shelled, low-fibre products. Thanks to our many years of close cooperation with the Bühler technology group as a supplier of shelling machines, extruders and more, this is not a problem. Customers can even buy complete systems, whether it be from Bühler or Hosokawa Alpine.

Of course, our experts from the food department are ready and waiting. Other companies in the Hosokawa Group can also provide support, as can our partners at Bühler. For process development, our Augsburg headquarters also has an extensive technical centre with laboratory-scale machines that can be used to process small quantities in feasibility studies. In addition, we have pilot plants that can process throughputs in the area of 200 kg/h. At the Grain Innovation Center, the new test centre of Bühler AG Uzwil, Switzerland, customers can develop customised processes for the processing of grain, legumes and more. And of course, Hosokawa Alpine machines for dry fractionation are also installed there.

On the one hand, we are seeing great improvements on the raw materials side. For example, we work with specialist breeders who develop higher-performance varieties and validate them on our machines. This enables enormous increases in protein purity and yield. Protein concentrates with over 70 percent have already been produced from yellow peas.

On the mechanical side, we are currently conducting research in an internal development project on a process that leads to a better protein yield than the conventional process described above. If we can succeed in producing improved protein concentrates through a suitable combination of specially cultivated raw materials and mechanical process engineering, the demand for energy-intensive protein isolates can be reduced and a great deal of expense and energy can be saved.