by
Alain Brisset, Clextral, France
Today’s worldwide consumed sea food can be split between aquaculture production and wild capture: this represents respectively 80 million metric tons (53%) for breaded animals and 71.2 million metric tons (47%) for the captured fishes.
These aquatic animals include finfish, crustacean and mollusks. Among the cultured animals in 2016, some are fed manufactured feed (56.6 million metric tonnes), whilst some are not fed manufactured feed (23.4 million metric tonnes) Finally, it is estimated that 35 to 40 million metric tonnes per year of feed is needed for the aquaculture industry.
Floating and sinking feed
In order to meet this demand, feed may be distributed as food wastes or/and as prepared feed. Different technologies are available to prepare the feed such as mixers, pellet-presses, expanders and extruders.
Extrusion technology is a relatively recent technology used in the aquaculture industry, originating approximately 40 years ago. Extrusion is a thermomechanical process consisting in forcing a product through a small size hole, under pressure and temperature thanks to a mechanical device named an archimede screw. The functions of an extruder are generally considered to be for feeding, conveying, compressing, cooking and shaping continuously. The expansion is due to the water flash off caused by the pressure difference out of the die.
Twin-screw extrusion
A fundamental difference between single and twin-screw technology is the mixing ability of a twin-screw extruder (TSE). This unit operation is generated by the two intermeshing screws co-rotating in a closed cylinder (the barrel) while a single screw extruder (SSE) works with only one archimede- type screw.
Conveying in an SSE relies on friction between the material being processed and the inner surface of the barrel, while a TSE can transfer any mixture from pure water to high viscous doughs even containing high levels of fat, similar to a positive pump.
A TSE is not sensitive to “slip-inducers” such as water and fats. The mixing properties of TSE allows a very homogeneous transfer of mechanical shear and temperature in the processed dough, giving it a homogenous form of cooking and viscosity. It is also possible to mix into a TSE liquid such as water and fat, in order to fine-tune the final expansion degree.
Read more HERE.
Today’s worldwide consumed sea food can be split between aquaculture production and wild capture: this represents respectively 80 million metric tons (53%) for breaded animals and 71.2 million metric tons (47%) for the captured fishes.
These aquatic animals include finfish, crustacean and mollusks. Among the cultured animals in 2016, some are fed manufactured feed (56.6 million metric tonnes), whilst some are not fed manufactured feed (23.4 million metric tonnes) Finally, it is estimated that 35 to 40 million metric tonnes per year of feed is needed for the aquaculture industry.
Floating and sinking feed
In order to meet this demand, feed may be distributed as food wastes or/and as prepared feed. Different technologies are available to prepare the feed such as mixers, pellet-presses, expanders and extruders.
Extrusion technology is a relatively recent technology used in the aquaculture industry, originating approximately 40 years ago. Extrusion is a thermomechanical process consisting in forcing a product through a small size hole, under pressure and temperature thanks to a mechanical device named an archimede screw. The functions of an extruder are generally considered to be for feeding, conveying, compressing, cooking and shaping continuously. The expansion is due to the water flash off caused by the pressure difference out of the die.
Twin-screw extrusion
A fundamental difference between single and twin-screw technology is the mixing ability of a twin-screw extruder (TSE). This unit operation is generated by the two intermeshing screws co-rotating in a closed cylinder (the barrel) while a single screw extruder (SSE) works with only one archimede- type screw.
Conveying in an SSE relies on friction between the material being processed and the inner surface of the barrel, while a TSE can transfer any mixture from pure water to high viscous doughs even containing high levels of fat, similar to a positive pump.
A TSE is not sensitive to “slip-inducers” such as water and fats. The mixing properties of TSE allows a very homogeneous transfer of mechanical shear and temperature in the processed dough, giving it a homogenous form of cooking and viscosity. It is also possible to mix into a TSE liquid such as water and fat, in order to fine-tune the final expansion degree.
Read more HERE.
The Aquaculturists
This blog is maintained by The Aquaculturists staff and is supported by the
magazine International Aquafeed which is published by Perendale Publishers Ltd
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