Fish meal with high protein content and low in minerals is in demand for feeding juveniles in aquaculture. Digestible proteins are contained in the soft tissue of the raw material; the minerals come from the bones. All fish meal plants can be equipped to separate the fine fraction of the dried product from the coarse mainstream––the bones––before it is milled, known as Enhancement of the product. The separated fraction can contain up to and over 80% digestible proteins and, since it is comparatively small, the reduction in the protein content of the very much larger volume of standard product is negligible.

Turbo-sieves (picture above) are used for controlled sifting of powdered and grainy materials, such as wheat flour, rye flour, fish meal, blood meal, powdered milk, maize powder, salt, sugar, chalk and other products of similar characteristics. The mainstream is fed through a hopper (top, left) and brought into the sieve by a screw feeder; there it is flung against the screens, where fine dust separates and the coarser particles travel along to the outlet (right, bottom). Turbo-sieves are equipped for self-cleaning and convenient replacement of screens with different mesh size.

Another way of doing this––the do-it-yourself way––is to make a section in the bottom of the mill conveyor replaceable (picture above). Sections with different perforations can be inserted to suit demands from the markets and/or different raw materials, including a solid section if no enhancement is desired.