Innovation in aquafeed processing technology and Extruded feed for warm water finfish and shrimp

1. INNOVATION
IN AQUAFEED
PROCESSING
TECHNOLOGY
Clextral new
Preconditioner +
and twin screw
extruder EVOLUM+
by Clextral
W
orld leading aquafeed
technology expert
Clextral has played
a pioneering role in
the innovation and development of
twin-screw extrusion for aquafeed
since the 1970s. To respond to new
challenges and increase the capacity of
existing systems, Clextral is introducing
two innovations this year: a new
preconditioner and a new range of twin-
screw extruders with advanced control.
Process flexibility and
improved efficiency
In twin-screw extrusion of fish-
feed pellets, preconditioners are
recognised by industry experts for their
production benefits. The new Clextral
Preconditioner+ integrates two horizontal,
intermeshing, counter-rotating shafts that
provide tangible production benefits:
improving the overall process and the
quality of the finished food products and
enabling energy savings, while providing
greater flexibility and more precise control
over the operating parameters, whatever
the recipe.
The key innovation of Clextral’s
Preconditioner that improves heat and
mass transfer to the product is the
Energy) required in the extruder –
an average of 3 percent with equal
extrusion parameters – mainly due to
the increase in preconditioning time, and
largely compensating for the additional
consumption of the Preconditioner+.
As mentioned previously, this efficient
pre-cooking reduces the shear and the
torque requirements in the extruder,
which results in less wear of the screws
and barrels.
By focusing exclusively on the
Preconditioner+, the experiment also
demonstrated that the new filling ratio (up
to 75 percent) achieved with AFC made
it possible to increase residence time by
60 percent for an equivalent fish-feed
flow and therefore to exceed the average
of three minutes. At the same time, the
combination filling/steam distribution
made it possible to increase the product
temperature by 3-4°C at the outlet of the
Preconditioner+, using comparable steam
injection.
It is even possible to achieve a product
temperature of over 96°C with optimised
steam injection, while limiting energy loss
due to the new design. Following the
improvements on the pre-cooking stage, a
significant increase in starch gelatinisation
before product feed into the extruder was
witnessed and measured.
Finally, on the finished product after
extrusion, granulation and drying, these
upstream modifications resulted in an
increased hardness of the pellets of at
least 10 to 15 percent, an essential quality
criterion required for their use in fish
farms.
Beyond the process benefits on
product quality, it is important to note
that this equipment is designed to facilitate
Advanced Filling Control
device (AFC) which interacts
directly with the material inside the mixing
chamber and enables the filling ratio to
be adjusted. The AFC system uses an
exclusive conveying screw inside the tank
and adjusts the flow by enabling a partial
and controlled recycling of the material
being processed, from the outlet to the
entry point, thus intensifying the specific
preconditioning functions.
In addition to increasing the filling ratio,
the AFC system also generates better
product distribution, in particular in the
first third of the mixing chamber which is
the preferential zone for steam injection.
The adjustable water and steam injection
ports have been optimally positioned to
enhance absorption and product exposure
time during the mixing stage.
Extensive experimental trials have
been carried out on the Preconditioner+
to verify the processing improvements
generated by its AFC system on the
twin-screw extrusion process. In this case
a standard fish-feed recipe (basic salmon
feed) was used, not to gauge optimal
performance but to set an objective
benchmark compared to traditional
preconditioning systems.
The first significant observation was a
lowering of the SME (Specific Mechanical
Advanced Filling
Control (AFC)
system: key
innovation of
Clextral new
preconditioning
system
16 | INTERNATIONAL AQUAFEED | January-February 2015
EXTRUSION

2. industrial applications, in particular because
of the increased flexibility provided by
the AFC. This variable speed device
enables adjustments of the residence time
as required to adapt the equipment to
different types of recipes and to respond
to the needs of multi-product extrusion
lines. Moreover, this convenient design
allows the system to start up when fully
charged, even after prolonged downtime
with a full tank, thanks to the new
kinematic feature.
In terms of hygiene and food safety,
the Preconditioner+ is designed with
minimal retention areas to facilitate
cleaning. This feature is further enhanced
by an integrated ‘quick recipe change-
over’ function through the reversible
AFC system, used here as a conveying
screw that enables the entire tank to
be emptied. These improvements in
equipment cleaning capabilities and
hygienic design are important advantages
for food processing applications.
Finally, the intensification of Clextral’s
Preconditioner + offers improvement in
the overall process, energy savings and
enhanced quality of finished products,
as well as greater flexibility and better
control of operating parameters, whatever
the recipe.
Clextral continues to innovate
with twin-screw extrusion systems
that produce aquatic feed with a
precise balance of proteins, oils and
carbohydrates, processed for optimum
digestibility with reduced waste. Clextral’s
systems process a wide selection of
recipes and raw materials and accurately
control pellet density for specific product
attributes, such as sinking and floating
properties. With these innovations in
preconditioner and extruder technologies,
Clextral is helping aquafeed processors
meet the process challenges of today and
the future.
ANDRITZ Feed & Biofuel A/S
Europe, Asia, and South America: andritz-fb@andritz.com
USA and Canada: andritz-fb.us@andritz.com www.andritz.com
Your global technology process supplier
for the aqua feed industry
ANDRITZ is one of the world’s
leading suppliers of techno­
logies, systems, and services
relating to advanced indu­
strial equipment for the aqua
feed industry. With an in-depth
knowledge of each key pro-
cess, we can supply a compa-
tible and homogeneous solution
from raw material intake to finis­
hed feed bagging.
Improved response time and stability
thanks to Advanced Thermal Control
(ATC) proprietary innovation.
New range of twin-
screw extruders
A daily task of aquafeed processors is
ensuring the perfectly stable quality of the
finished product despite daily variation in
the characteristics of the raw materials.
Clextral’s new EVOLUM + twin-screw
extruders offer advanced technology that
gives processors new levels of throughput,
flexibility, and control while ensuring
maximum product quality and process
stability.
A major innovation, the Advanced
Thermal Control (ATC) is a self-learning,
proprietary software solution to ensure
absolute precision in temperature control.
ATC continuously monitors production
and adjusts to changes in parameters
(characteristics of raw materials, recipes,
throughput, etc.) to ensure process and
product consistency. ATC is proven
to enhance process stability up to 70
percent, with energy savings averaging
20 percent by eliminating excess heating/
cooling to maintain process temperature
set points in any circumstances.
The EVOLUM+ range has also
been specifically built for more hygienic
processing and food safety with
ergonomic designs and open profiles that
allow full machine access.
January-February 2015 | INTERNATIONAL AQUAFEED | 17
EXTRUSION

3. Extrusion is a cooking process that typically uses high
temperature and high pressure for a short period of time. The first
extruder was developed in the 1930s for pasta; extrusion was later
modified for the production of pet food and fish feeds as well as
human foods like snacks, breakfast cereals and sweets. The extru-
sion process begins with preconditioning the meal using steam and
water to form a hot, moist mash. The process has the flexibility to
produce diets with a wide range of fat levels, densities, shapes and
sizes. It also has the capability to produce floating, semi-sinking
and sinking pellets for shrimp and pelagic fish. Extrusion has been
used to manufacture shrimp feed since the early 1970s, but not
widely adopted due to a persistent tendency for expansion in
extruded feeds, which leads to undesirable flotation.
Expansion is exacerbated by the use of smaller die open-
ings. To minimise flotation, feed manufacturers were forced to
limit inclusion levels of starch, which tended to increase raw mate-
rial costs. These constraints have been virtually eliminated through
recent advances in extrusion technology, such as adjustments in
screw design and speed, changes in die configuration and vacuum
venting of the extruder barrel. It is now possible to produce 100
percent sinking extruded shrimp feeds with densities equivalent to
those of pelleted feeds.
E
xtruded feed has the advantage of reducing raw material
expenses, achieved by the substitution of high levels of
wheat flour with lower levels of less expensive starch.
This is possible due to the high moisture, temperature
and pressure within extruders, which lead to nearly complete
gelatinisation of a wide range of starches. Extruded feeds utilise
relatively high levels of moisture, which can be added in the form
of flavors and palatability enhancers such as fish, dried solubles
and flavorful enzymatic digests of seafood waste. This offers the
potential to produce a new generation of highly palatable shrimp
feeds without reliance on expensive marine protein such as
squid meal and krill meal. The rate of swelling of extruded feeds
can also be manipulated to deliver feeds of varying ‘softness’.
The swelling is a function of starch fragmentation, also known
as dextrinisaton, which can be controlled by the degree of shear
exerted by the extruder screw. The 1995 study Physiochemical
properties of extruded pelleted shrimp feeds with various
wheat flours conducted by GH Ryu and coauthors at Kansas
state university in Kansas, USA showed an 89 percent correla-
tion between the extent of starch gelatinisation and the water
stability of 10 Asian shrimp feeds. Other studies on conventional
single-pelleted feeds for terrestrial animals reported that only
about 20 percent of the starch is gelatinised. This explains why
typical poultry feed disintegrates in water within minutes of
immersion.
In addition, pelleting systems for shrimp feed use advanced
manufacturing techniques such as fine grinding of raw materials,
multiple steam conditioners, higher moisture levels, pelleting dies
with higher compression ratios, post-pelleted conditioning and
drying. These techniques increase the starch gelatinisation levels
of extruded shrimp feeds to 80 – 95 percent compared with
conventional pelleted shrimp feeds.
In a 12-week study in 2000, Albert Tacon and co-workers
at the Oceanic Institute in Hawaii, USA compared single feed
formulation in pelleted or extruded forms and two different sizes;
results reported in February 2003 showed higher shrimp survival
and weight gain and greater feed efficiency from extruded feed.
These results are being validated on a commercial scale in Korea,
Malaysia and Brazil. Compensation for the vitamin losses thought
to be slightly higher in extrusion than in pelleting can be easily
accomplished by slight fortification of premixes.
Finally, recent developments in extrusion processing allow the
production of sophisticated 100 percent sinking diets with lower
cost and better performance than conventional pelleted feeds.
Its advantages are expected to become more apparent, since
the additional benefits of higher liquid addition, greater control
of swelling and greater pasteurisation further contribute to higher
performance.
Extruded feed
for warm water finfish and shrimp
by Prof Mohammed Y Al-Saiady
18 | INTERNATIONAL AQUAFEED | January-February 2015
EXTRUSION

4. January-February 2015 | INTERNATIONAL AQUAFEED | 19
EXTRUSION
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