FEED TECHNOLOGY UPDATE - AquaFeed.com

DENSITY CONTROL
Density control and process optimization
for extruded aquatic feeds
The effect of formulation and process variables on finished
product density
By Galen J. Rokey and Brian S. Plattner, Wenger Manufacturing, Inc.
A
n aquatic feed’s density
is a critical component
as it impacts
many things including
plant capacity, floating
and sinking properties, product
appearance, and absorption
of external coatings.
However, the pellets’ floating
or sinking properties are often
the most critical functional
characteristics as the
feed buoyancy impacts both
the aquatic animal's nutrition
as well as the aquaculture
environment.
The buoyancy of aquatic feed is easily correlated
with bulk density, as shown in
Table 1.
Controlling the density during extrusion can
often be a challenge due to the many process
variables which can be manipulated.
In an earlier article “Adding Flexibility to
the Extrusion Process” [FTU - January,
Table 1:
Final Product Bulk Density Correlation with
float-sink properties for Aquatic Feeds
Feed
characteristics
Sea water @
20ºC .
(3% salinity)
Fresh water
@ 20ºC
Fast-sinking >640 g/l >600 g/l
Slow-sinking 580-600 g/l 540-560 g/l
Neutral 520-540 g/l 480-500 g/l
buoyancy
Floating