Aquaculture: Producing aqua feed pellets

March | April 2011
Feature title: Aquaculture - Producing aqua feed pellets

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The International magazine for the aquaculture feed industry

F: Feed pellets F: Feed pellets Extruder_90x270_Kopie von 90 X 270 10.02.2011 16:18 Seite 1

endless screw or oil expeller that presses blood and bones,
it and squeezes out most of the remaining etc which are
water and oils. often difficult to
Pressed fish coming out of the press commercialize.
(press cakes) then cut into smaller portions Nowadays,
and placed into a dryer on a steam heated however, these by-
surface. During the drying period, the mash products constitute
is in constant motion and subject to an the basic raw mate-
air jet that removes all the steam emitted. rial of the bone and
The dried mash obtained is now called 'fish blood meals widely
meal' and contains from 8 to 10 percent used in industry for
of water. animal feeding.
However, if the moisture level is more Considerable

Aquaculture:
than 11 -12 percent, there is a risk of the amounts of blood Find us on
fish meal developing moulds. Generally, are produced by
antioxidants are added when fish meal is abattoirs, and this
booth no. G 061

Producing aqua feed pellets
introduced and taken out of the dryer, and product is usu-
by so doing ensuring the stability of the oils ally transported
remaining within the fish meal. to drying ovens
and converted
Soy protein into blood meal.
Not all fish species have easy digestibility Blood from differ-
by R V Malik, CEO, Malik Engineers, Mumbai, India of soy protein, primarily due to increased ent origins such
carbohydrate content fraction. It is usually as, sheep, goat, and

A
used as supportive additive with other eas- poultry are usually
s more of world’s natural proteins which is strongly demanded by then cooked in a continuous heating oven ily digestible protein like fish meal which is stored and proc-
fisheries are depleted and the animal feeds industry. This is due to its at 90-95 percent, which in-turn coagulates rich in fish proteins. essed separately.
demand of fish continues balanced amino acid content, which makes proteins and lose their water-holding capac- Bean processing consists essentially of However, so as to
to rise, aquaculture will it an ideal feed for many domestic animals. ity. The hot mash is then transported to an extracting the oil so as to concentrate comply with basic
continue to grow, thus raising demand Moreover, its use to adjust the proteins. This process provides a very sanitary measures,
for healthy, commercially prepared (improve) the amino acid con- important by-product, namely soya oil, it is generally com-
fish tent of other dietary protein which is widely used as a raw material pulsory to store Laboratory Extruder
sources also contributes to and oil for human consumption. This proc- blood within cool-
Mostly, aquaculture relies upon extrusion increase demand for fishmeal. ess also contributes to the elimination of ing chambers and for Food and Feed
cooking to produce feeds that are good mix As its name points out, fishmeal certain anti-nutritional factors present in to ensure that the
and nutritionally available, but also in a form is derived from captured fish, the raw bean. level of bacteria is
that is capable of moving through water including whole fish, fish scraps The first step in processing involves kept within pre-
column very slowly (floating) to be ingested. from fillets, and preserves of the removal of the shell (cellulose) from scribed maximum
Thus, the big dependency in aquaculture is industries. the grain. The ‘bare’ beans are then limits.
selecting ingredients that when extruded Most of the main capture heated, on the one hand to reduce the
will possess just right buoyancy, not migrate fishery producers devote the activity of certain enzymes, and on the The
nutrients into water, with high palatability main part of this activity to fish other to break the cellulose strands and manufacture
for specific fish species. meal production. The raw mate- facilitate the following steps. The heated of
Fishfeed pellets are prepared either rials used in fish meal manufac- beans are then mashed to form thin bloodmeal
by pressed cut sheets or by Extrusion ture come almost entirely from paste-like slices, which further facilitates Fresh blood
methods. This article will discuss about species which are not often used the destruction of the cellulose structure is kept cool at
Ingredients and Extrusion process for pro- for human consumption (either and oil extraction. the factory, and
ducing the pellets. due their size, or because they The product, now termed ‘whole soya sizeable particles
Main ingredients include: are very abundant). cake’, still contains its oil and has around 40 filtered and the
1) Fish & Bone Meal The fishmeal processing percent protein, and as such is sold directly blood mass stirred Quality control and testing of
2) Soy protein (though it is not preferred system consists of preserving for animal feeding. so as to separate raw materials
by farmers being not easily digestible initial fish proteins by means of Next, the oil can be extracted from the the fibrillar phase
by many fish species) a controlled dehydration, which whole cake by means of a solvent (such from the liquid Product development and
3) Wheat extracts around 80 percent of as hexane). After total evaporation of the mass. The fibrin is recipe optimization
4) Starch the water and oils contained solvent, there remains the solvent extracted then heated up to
5) Blood Meal when fresh from fish. soya cake, which in turn is widely used for coagulation and the Small-scale production
Other ingredients like Vitamins, Minerals This leads to the produc- animal feeding, and contains 45 - 50 percent coagulated mass Quick change of test conditions
and Lipids (Fat Oil) are also added in tion of a dry product, easy to protein. divided and dried
producing pellets. preserve and easier to transport through a hot air
than the initial product. Bloodmeal stream (that is by
Fishmeal Fresh fish entering the manu- Abattoirs or slaughterhouses produce spray drying). This Brabender® GmbH & Co. KG
Fishmeal is a well-known source of facturing plant is first ground and many important by-products, such as method is particu- E-Mail: food-sales@brabender.com • www.brabender.com

10 | InternatIonal AquAFeed | March-april 2011 March-april 2011 | InternatIonal AquAFeed | 11

F: Feed pellets F: Feed pellets
larly gentle (spraying a product in a hot air- Lipids Formulation of fishfeed force, position as ‘expanded feed’, is also marketed by
stream) and does not denature the proteins Fish oils are co-products of the fish- As we have seen, feed formulators can themselves form- some manufacturers.
because the water evaporation cools down meal industry. Their nutritional charac- resort to a wide assortment of raw materi- ing a star on The main difference between a pressed
the hot air very quickly, thereby preventing teristics regarding fatty acids make them als to make up a food mixture so as to the rotor and and an extruded feed is the cooking of the
overheating. indispensable for fish feed manufacture, meet the nutritional requirements of the split the incom- feedstuff in the case of extrusion, with the
and in particular their characteristic fish for energy, amino acids, fatty acids, ing feedstuff added mechanical and biological advantages
Wheat flour high content of n-3 unsaturated fatty carbohydrates, vitamins and minerals. apar t, which previously described, especially with regard
Wheat is one of the most important acids (first double bond linkage in posi- These raw materials are generally used is then forced to starch gelatinization
cereals worldwide, and is used for making tion 3), which are essential for a well in flour or liquid form, and will have to by depression
bread and for many other produces. It is balanced food formula for carnivorous undergo binding by means of a technologi- through a metal Extruded Feeds:
also an essential raw material for livestock fish species. cal process to obtain a food mixture in the grid composed The Extruder can be described as a
feeding, including fish. A large amount of fish oil arising from form of dry pellets, which are easy to use of appropriately Bio-Reactor with (mostly) a single, multiple-
fish meal manufactures is re-processed in and preserve. sized meshes. flighted screw (rotor) rotating at high speed
Wheat in fish feeding specialized facilities for diverse purposes; As a guide, salt water marine aquaculture inside a stationery hollow tube (stator).
Starch products, especially wheat, are fre- part of it being hydrogenated and mixed is dependant upon high levels of proteins - Mixing The raw materials fall from top at
quently used as binders for the manufacture of with other lipids, and transformed into mar- with high digestibility. The fresh water aqua- The ground one end on the rotating screw which has
pellets; the gelatinizing property of starch when garine, mayonnaise and bakery compounds, culture relies upon more carbohydrates, ingredients must multiple flights and varying pitches along
water-heated being useful for this purpose as and the other part used directly by the feed that is high levels of grains coupled with be mixed accord- its length. The barrel (tube) is externally
the starch absorbs water and forms a gel. industry. modest to high quality proteins, minerals, ing to the desired heated/cooled by steam and cold water
vitamins with little or no fiber. proportions to externally around. Due to this arrangement,
The first factor to be considered for obtain a homoge- a high pressure of around 40-70 bars
feed formulation is the total energy and wide variety of ingredients that can have neous mixture. If the grinding process (Kg/cm2) is developed on the ingredients,
protein/energy ratio of the final product. varying particle sizes. It is desirable, but not is correctly developed, the particles are temperature of ingredients varies from 110
After this, the protein content must be cal- necessary that all ingredients be of uniform homogeneous in size and the mixture C to 160 C, which ensures cooking of ingre-
culated according to the amino acid balance particle sizes, to prevent segregation during produces pellets which statistically have the dients into plastic mass which is extruded
desired, and the lipids included to satisfy mixing and transport prior to extrusion. same formulation. out of multiple die openings/orifices and
the best fatty acid profile for the species Uniform particle size of ingredients pro- Generally, the dry ingredients (flours) cut to produce porous pellets for fish feed.
concerned and the energy level desired. All motes better mixing and uniform moisture are first mixed, followed by the liquid Pre-Extrusion: Dry ingredients after
this must be considered taking into account uptake by all particles during the precondi- components. Continuous mixers are having been mixed & ground thoroughly in
the vitamin and mineral requirements of the tioning step. designed so that the feedstuff moves desired proportions, are usually transport-
cultured species. If the particle size of raw ingredients along the mixer as it mixes. There are ed to the Single screw Extruder (Cooker)
This formulation is not easily reached is too large, the final product may contain many different types of mixers, including provided with a Pre-conditioner at top.
Moreover, when starch is gelatinized its Minerals and so computerised linear programming particles which are improperly cooked, horizontal band-mixers, vertical mixers, The Feed Delivery System: It consists of
digestibility improves considerably. Various Minerals are measured as ash in the techniques must be used. Furthermore, which degrade product appearance and conical screw-mixers, and turbine mixers, a “Live Hopper” or Bin with a horizontal
starch types (wheat, barley, rice, maize or recipe. Though they serve no functionality it is also necessary, after covering all the palatability. etc. conveying screw to convey dry ingredients
potatoes) can gelatinize but each one will in extrusion (on the contrary their abrasive nutritional requirements of the species Also, if particle size is larger than die During this mixing process, the vitamin to the Preconditioner from above. The Bin
have its own characteristics. nature will accelerate wear and tear of within the formula to also produce a range orifice used at extruder discharge, it may ‘premix’, the binding agents and other is provided with device which avoids bridg-
In addition, all three starch types gener- working parts in extruder), these are usu- of tasty feeds of different pellet sizes for the cause plugging of some orifices affecting additives are added; they must in turn con- ing of material (since raw ingredients have
ally have the capacity to form a stable ally added in proportions < 5 percent. They different age classes. capacity and appearance. As rule of thumb, tribute to one or other particular desired low bulk density and poor flow through a
structure when subjected from high to low include phosphorous, calcium (from calcium it is necessary to maintain size of raw quality of the pellets during the pelleting normal Hopper) and ensures continuous
pressure during the extrusion process. carbonate or ground lime stone), sodium Manufacturing stages ingredients one third of the die opening die. process. flow of materials to the Preconditioner
It is this property that is used for chloride (salt), magnesium, potassium, etc. Hence the need of size reduction equip- below, hence the name “live” bottom bin.
feeds that must have a high lipid content, - Storage ment and sifting. - Pelleting It should hold adequate volume to support
during the extrusion process the starch Vitamins: The raw materials coming into the feed In hammer-mills, the grinding chamber Two different types of pellets are gener- the extruder operation for minimum 5-8
forms a cell structure with alveoli that They can be water soluble or soil solu- manufacturing plant are generally stored in consists of a series of mobile hammers ally prepared for aquafeeds, namely pressed minutes, as a buffer time for the operator
can then be filled with oil instead of air ble. Vitamin B and C are water soluble, A, D, silos with an ideal height calculated so as to on a rotor. The hammers, by centrifugal and extruded pellets. A third type, designed and auto control network to respond
and/or steam. E, and K are fat soluble. They are added in allow the raw material flow to be conveyed
For carnivorous fish feeding purposes proportions < 0.5-0.6 percent in diet, but downwards, during the manufacturing proc-
the starch must be considered as a sup- due to harsh processing conditions inside ess, until the final product is produced. This COMPLETE PLANTS AND MACHINES FOR THE FISH FEED INDUSTRY

porting structure that gives the pellets the extruder, these get destroyed, hence is in order to avoid having to pull the prod-
their texture and together with the other they are added well in excess of minimum ucts up by vertical conveyors that usually
dietary ingredients allows the formation of requirements. cause breaks and dust in the final product.
a binded diet. Apart from above, the feed may
However, since the natural feeding habits contain, flavors/aromas, antioxidant - Grinding
and foods of seabass and/or seabream (preservative) and antimicrobials, dyes Grinding raw materials reduces particle Fabric Belt
usually contain very small proportions of & pigments (for human appeal and dis- size and increases ingredient surface area, Driers/Coolers
carbohydrates (ca. three percent glyco- tinction, rather than for fish itself), etc. thus facilitating mixing, pelleting and digest- AMANDUS KAHL GmbH & Co. KG
gen, animal starch - glucose polymer). If It is important to use certified ingredi- ibility. The most commonly used grinders Dieselstrasse 5-9, D-21465 Reinbek / Germany
Phone: +49 40 727 71 0, Fax: +49 40 727 71 100
excessive quantities of digestible starch are ents that does not affect health of fish. are hammer-mills, for fish feed manufacture, info@amandus-kahl-group.de
provided in the feed this may result in the Pigments are usually added as a coating as plate-grinders do not generally produce www.akahl.de
accumulation of excess liver glycogen, which step, to minimize losses during harsh fine enough ground materials.
MIXING CONDITIONING PELLETING EXTRUSION COATING COOLING
in turn may trigger a liver dysfunction. extrusion processing conditions. The Extrusion cooking process utilizes


F: Feed pellets

"As more of world’s natural fisheries are
depleted and demand of fish continues
to rise, aquaculture will continue to
grow, thus raising demand for healthy,
commercially prepared fish"

and allow recharging the bin from top. “Wet Extruder” since feed materials con-
The screw is provided with variable speed - Extrusion tain around 25 to 30 percent moisture
motor to properly adjust the flow as per Usually single screw Extruders with sin- (water). Both screw and the barrel are
production capacity of the Extruder. gle barrel and screw is used for cooking the made up as separate segments so that
Preconditioning: This step ensures the preconditioned ingredients, but twin screw individual components could be replaced
dry ingredients are constantly added with extruders are also used. The latter have when worn. Multiple flighted, varying pitch
moisture (water) in desired proportions limited use because of high initial capital screw elements are usually employed to
(25-30%) and steam is also added, at 5-6 bar, costs compared to single screw extruder. provide cooking and forward convey-
for pre-cooking the wet ing of feed materials.
ingredients. As the ingre- Table 1: The Volumetric capacity
dients move forward of screw is highest at
FEED A FEED B Difference
towards the Extruder Feed zone to account
feed opening, they are of low bulk density of
held at temperature of (1) Growth 1 1.1 10% ingredients. However, it
approximately 100 C reduces (lower pitch)
2) Conversion rate 2 2 0%
and atmospheric pres- towards the die, which
(3) Feed price / kg 5 6 +20%
sure. Preconditioning causes compression and
makes the ingredients (4) Selling price of fish 50 50 0% cooking of feed mate-
soft by precooking and it (5) Feed expenditure for 1 kg of fish rial. The final discharge
10 12 +20%
reduces energy require- produced (2) X (3) end of screw is usu-
ment in the Extruder. If (6) Profit from fish sales (1) X (4) 50 55 +l 0% ally Conical to generate
Lipids are to be added, high pressure and attain
(7) Gross margin for feed item (6) - (5) 40 43 +7.5%
their proportion is lim- maximum expansion of
ited from 5-7 percent in pellet when emerging
this stage. The action of the Extruder allows the from die opening. The barrel heads are
Conventional Preconditioners had only free flowing ingredients to bond to each provided with Steam Heating and water
one tank and single agitator, but modern other and remain in pellet form after exiting cooling Jackets around, for heating or
preconditioners have special oval tanks with from shaping (pelleting) die. It does this cooling, as per process demand. The proc-
two agitating shafts with adjustable beaters by the action of rotating screw or spiral ess temperature is held from 110 C to
to control residence time inside the tank. inside a stationery barrel by generating high 160 C gradient from Feeding Zone to
Two agitators result in the better mixing of mechanical shear and raised temperature Final Cooking Zone. Maximum convey-
dry and liquid ingredients. Longer retention on feed materials. ance & mechanical shear of material is
time approximately 2-2 ½ minutes are Extruders for Fish Feed production have ensured by action of multiple flighted
desirable before feeding into the Extruder. Mechanical Energy Input levels between screw elements and spirally grooved bar-
Usually lipids are added not more than 20-40 Kw-hr/ton of produce. Their screws rel segments. Water present inside the
5-7 percent by weight here, since it leads run between 400-1000 RPM depending on mixture is held as steam at high tem-
to excessive slippages inside the Extruder sizes. Output capacities range between 1 t perature and pressure. However, as soon
and poor mixing & expansion/texture of to 20 t per hour. as the cooked mass emerges out of die
final pellets. The Extruder usually employed is openings pressure drops to atmospheric


F: Feed pellets
and the product expands or “puffs”, being time of products should be carefully applied through bed of pellets to lower the
cut continuously by Rotating Die Knives adjusted to attain properly dried product temperature.
working against the die Face, giving the that can absorb maximum fats and coat- Cooling is important, since if packed in Improvement
pellet the specific rounded shape for ings in the Coating step. hot state, moisture will condense in the
by nature
extruded pellets.
Retention time inside Extruder is from - Sifting
packing, wetting the outer surface of the
pellets, allowing mold growth. It is desir-
Natural ingredients for aqua feed
100-180 seconds, which ensures 70-85 per- The mechanical manufacturing processes able to cool down within 10 C of ambient
cent starch gelatinization and production of inevitably results in shocks and scorching air tempt. So that problem of condensation Whether you’re looking for a natural EU and USDA approved pellet binder for your
good shape and density. that partially crumble the pellets at their in packing doesn’t occur. production of stable pellets or nature’s best alternatives for fish meal, you can contact Sonac.
The above Extruder produces Floating surface and cause various breaks and dust Sonac produces valuable and essential ingredients for the production of aqua feed.
Pellets with low bulk density, e.g 350-450g/l that must be eliminated. This is achieved by - Bagging
that are classified as “Floating” and sink very sifting, a process that is generally applied Bagging usually produces different
• Pro-Bind Plus a nutritional, gelatin based pellet binder, especially for pelleted (shrimp) feed.
slowly into water column. Most Extruders at least twice before the final condition- types of feed presentations within the
have an arrangement, whereby the water ing (sifting after drying and after coating/ same factory, namely either small bags • Hydrolyzed feather protein a fish meal alternative, especially for carnivorous fish species.
vapour present in the mix is released by a cooling). (20 or 25 kg) on pallets covered with • Muco-Pro® high contents of natural proteins, amino acids and peptides.
vent opening on the barrel so that high den- a plastic film, or big-bags (500 or 1000 • Blood meal and Hemoglobin Powder high protein content and good digestibility, for better
sity pellets or sinking pellets are produced - Coating kg) in bulk.
feed conversion.
for certain species of fish. The pellets emerging from the pel-
The following parameters will con- leting presses or extruders do not Viability of Extrusion
trol the final pellet density: 1. Initial generally contain more than 7 to 10 process
moisture content (usually 25-30 percent percent lipid. To achieve higher dietary It follows from the higher tempera-
on wet basis). 2. Process temperature. lipid levels (20-27%), coating is neces- tures and pressures used during extrusion
3. Extruder back pressure. 4. Extruder sary with the appropriate oils, generally processing that investment and energy
RPM (residence time). 4. Drying condi- using heat. In the same manner, certain costs will be higher than those of conven-
tions and temperature. 5. Quantity of heat sensitive vitamins and/or drugs tional pressed feeds. Despite this however,
Fats, vitamins & minerals applied post that would not normally withstand the the use of extruded feeds may be more
extrusion. harsh extrusion processes (thermo profitable.
labile products) can also be added Following Table (illustration) summa-
Visit us at: Stand B069, Victam International
- Drying later during the coating process. These rizes the theoretical results obtained with
When added to Extruder, the ingre- ingredients are usually added through fish fed a pressed (A) or extruded (B) feed.
dients contain around 25-30 percent spray nozzles fed through dosing pumps Table showing Justification for Extrusion SON0296_AD_AquaFeed_180X118_W2.indd 1 16/02/2011 14:35
moisture (wet basis). Extrusion process which accurately control the weights Over Press Feed production method for
evaporates approx. 4-7 percent moisture deposited. They can be vacuum assisted Fish Feed.
thus still retaining considerable moisture for still more good results. It is clear from the example given DP

inside the pellets. After the pelleting The Expansion that occurs as a result that despite the fact that the price of the
LS LS

M
4
LS

process, the pellets usually have a high of extrusion processing makes the product extruded feed is 20 percent higher, the
moisture content (17 to 22%) that must porous with low bulk density and air feed which provides 10 percent additional LS

be quickly reduced to avoid spoilage. pockets, so that more oil is absorbed during growth provides a 7.5 percent additional
This is usually achieved by using a hot-air the spray coating process. Fats could be gross margin.
LS

5

drier, which lowers the moisture level added in the form of Animal fats, Fish Oil or
to between 8 and 10 percent depending Vegetable Oil.
M M
6 6 6

L
LS

upon the manufacturing process. DP

- Cooling Note:
MCC 2

Continuous Belt Dryers are com- LS
L 10

MCC 1

monly employed that provide heated air On completion of the coating process
The author is CEO Malik Engineers,
LS

to remove excess moisture from wet (generally undertaken with heated mate- Mumbai, which manufactures a wide range
product, as it travels on multiple decks rial) the pellets are then cooled and sieved of extruders for food processing and aqua/
of perforated steel belting. Since the before the final conditioning; cooling occur- animal feed. He can be reached on info@
Drying process is critical and determines ring in a cool-air flow generated by a malikengg.com Tel: +919821676012, +91 22
the quality of pellets, it needs to be cooling-machine. Again, this machine usually 28830751, +91 250 2390839
carefully monitored and controlled. The provides continuous flow of product on
Air Temperature, Humidity and Residence perforated steel belts, while cooling air is

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Aquaculture: Producing aqua feed pellets

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