extruder and pellet machine in aquatic food making
There are two types of aquatic food pellets commonly sold for farming fish or other aquatic species. The pellets have enough density to allow them to sink into the water, which is necessary for crustaceans or bottom-feeding fish, or they have a reduced density to allow them to float on the surface of the water.
Floating pellets are usually produced by extruder-expansion rather than conventional pelleting because extruders can significantly reduce the bulk density of some starch-protein mixtures caused by starch gelatinization form the presence of moisture, temperature and pressure conditions in extruder. However, conventional pellet mill do not usually reduce the bulk density of these mixtures. So far, all of these floating aquatic food pellets have been made on fish extruder machines.
Although these extrusion products are very satisfactory, they require a large amount of capital input through the feed mill, which is usually used only for pelleting of the feed and not for extrusion. Therefore, it would be advantageous if floating aquatic food pellets could be produced on traditional pellet mills.
Also Read: Extruded Aqua Feeds vs Pelleted Aqua Feeds
The Differences Between Extruder and Pelleting Machine
An extruder is a device for pushing or pulling materials through a forming die to form a product with a predetermined continuous length of cross section.
Pelletizing is the process of compressing or molding material into pellet shapes. Various materials are pelleted, including chemicals, iron ore, animal compound feed, etc.
Extruder does not need the steam boiler.
The feed pelelt made by pelleting machine is more smooth and with better quality.
The capacity of extruder is lower than pelleting machine.
Extrusion has Several Advantages Over Pelleting
Buoyancy can be controlled, so floating and slow sinking feeds can be produced;
Extruded feed is usually capable of carrying higher fat levels than pelleted feed;
For many species extrusion increases carbohydrate availability;
Extruded pellets generally have greater physical integrity and produce less fines;
Wet materials such as fresh minced fish can be readily incorporated into extruded products.