Note: Descriptions are shown in the official language in which they were submitted.
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Process for the Production of a Nutritional Composition
The present invention relates to a process for the
preparation of a fish-based fodder and to the fodder so
prepared.
Aquaculture, sometimes referred to as fish farming,
is a rapidly growing industry and provides an increasing
demand for fish-feed, ie. fodder. Currently major
components of fish-feed are marine proteins (in the form
of fish meal) ,and marine oils (in the form of fish
oils) .
The term "feed" is generally used in the art to
describe a product which meets the daily nutritional
needs of the creature being fed with it, ie. it contains
all the essential nutrients. The term "feedstuff" in
comparison is used to refer to a component of the
complete feed, e.g. a protein or fish oil or a component
containing the necessary proteins and oils but without
the proper vitamin content. As used herein, the term
"nutritional composition" includes both complete feeds
and feedstuffs.
In aquaculture, in particular salmon and catfish
farming, fodder pellets are used as feed. These pellets
are usually made from fish meal and fish oil and result
in a more efficient use of the raw material. Thus for
example 10 kg of capelin used directly as food for cod
leads to generation of about 2 kg of cod corresponding
to about 0.7 kg of cod fillets. If instead 10 kg of
capelin is processed to produce fish meal and fish oil
and used as fodder for farmed salmon, the yield is about
4.6 kg salmon or 2.8 kg salmon fillet. The energy yield
moreover is significantly greater: the cod fillet
corresponds to about 3 MJ while the salmon fillet
corresponds to about 28 MJ.
The fish meal and the fish oil are produced by
cooking the raw material (fish), and pressing the cooked
SUBSTITUTE SHEET (RULE 26)
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material to separate it into three fractions: water;
fish oil; and protein. The protein fraction, the dried
solid remnant of the cooking and pressing process, is
about 70o protein, loo fat and 10% water and is milled
to produce fish meal. The oil fraction can be used
directly for animal/fish feed production or
alternatively may be purified and used for human
consumption.
While it is termed fish oil, a more accurate term
is perhaps lipid; both.terms will be used below.
In the production of feed pellets, fish oil,
optionally together with plant oils, is sprayed onto
pellets formed from fish meal, optionally together with
plant carbohydrates. In this way pellets with a lipid
content of up to about 35o by weight can be produced.
Ideally, the lipid content should be higher for optimal
growth promotion in farmed fish such as salmon. However
in warm temperatures, for example those experienced in
summer, there is significant leakage of lipids from the
feed pellets - a 500 kg sack might release as much as 30
to 50 kg of lipids. Not only is this wasteful of fish
oil, since the released oil will not be consumed by the
fish, but it results in the fodder being messy and
difficult to handle, it results in clogging of automatic
feeding systems (which often rely on pneumatic feed
distribution) and it is environmentally undesirable as
it puts oil onto the water surface.
Moreover, processing the raw material (fish) to
separate out fish meal and fish oil and then recombining
these to produce feed pellets involves a considerable
usage of energy and equipment.
An alternative process for fish fodder production
has been described in NO 903175 (Hamre). In this
process the raw material, e.g. whole fish, fish heads,
fish entrails, etc., is ground up, mixed with wheat
meal, pelletized and then cooked in a microwave oven to
produce pellets which float in water and which have a
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moisture content of 10 to 300. The microwave cooking
coagulates the protein and prevents the pellets from
coalescing - however the problem of lipid release is not
overcome and the water content is undesirably high
unless the pellets are to be used immediately. For
storage-stable fish feed pellets, the water content is
desirably below 10% by weight.
We have now found that improved feed and feedstuff,
particularly in the form of pellets, can be produced if,
before heating and/or drying, the raw mixture is
emulsified, e.g. to a mayonnaise-like consistency. If
this is done, the lipid content can be increased without
lipid leakage problems and storage-stable pellets with a
low water content can be produced.
Viewed from one aspect therefore the invention
provides a process for the production of a nutritional
composition, said process comprising emulsifying a
material comprising raw fish and heating and/or drying
the resulting emulsion, preferably heating said emulsion
to coagulate the protein therein.
In the process of the invention, the raw fish used
may be whole fish or parts of fish, e.g. entrails,
heads, tails, etc., for example the waste material from
fish filleting or gutting. Fish of the same species as
the intended consumers of the nutritional composition
are not recommended for use as the raw fish.
Besides the raw fish, other substances may be
included in the material which is emulsified, e.g. fish
meal, fish silage (hydrolysed fish), plant carbohydrate
(e. g. wheat meal, corn meal, etc.), fish oil, plant oil,
colouring agents, vitamins, minerals, pharmaceuticals
(e. g. antibiotics, growth promoters, etc.), and plant
proteins, especially storage proteins and most
particularly gluten.
These additional substances may serve to provide a
balanced diet for the creatures fed with the nutritional
composition, e.g. the vitamins and minerals; they may
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serve to adjust the lipid/protein balance, e.g. where
the raw fish used is low in lipids, fish or plant oils
may be used to increase lipid content; they may, like
the colouring agents, be used to make the flesh of
farmed fish more closely resemble that of wild fish,
which is particularly desirable for farmed salmon; or
they may serve to improve or protect the health of the
creature receiving the feed, e.g. where antibiotics are
used. The use of plant storage proteins, in particular
gluten, however is especially desirable as it
significantly and surprisingly improves the texture,
physical strength and lipid retention ability of the
product.
Thus with such additional substances included, the
product of the process of the invention is in one
preferred embodiment, a complete feed, especially a feed
in pellet form or a feed or feedstuff in granular form
(e. g. in powder, grain or meal form).
The material which is emulsified and heated should
have a sufficiently high protein content to be
coagulatable on heating. Typically the protein content
will be 30 to 60% by weight, e.g. 35 to 550, preferably
38 to 45%, most preferably about 400 on a dry weight
basis. Of this, up to 1000 may be fish protein,
preferably at least 50% deriving from the raw fish.
However up to 50o by weight of the protein may be plant
protein, preferably gluten. Gluten especially
preferably contributes 0 to 40o, e.g 5 to 400, more
preferably 5 to 300, e.g. 10 to 300 or 15 to 250, and
most preferably 10 to 20% by weight of the total
protein. Gluten is preferably used as such, ie. as
gluten rather than only in carbohydrate-containing wheat
flour.
The high protein content of the material to be
emulsified also serves to enhance the formation of the
emulsion by serving as an emulsifying agent. In
addition, this effect may optionally be enhanced by the
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use of at least one specific emulsifier.
The mixture which is emulsified, and preferably
coagulated, will preferably have a lipid content of 15
to 55o by weight on a dry weight basis, more preferably
20 to 400. This may derive completely from the raw
fish; however typically up to 25% of the total lipids
may derive from added plant or fish oils. Suitable
plant and fish oils include oils from cod, capelin,
herring, sprat, blue whiting, sand eel, Norway pout,
soy, oilseed rape, mustard seed, sunflower, safflower,
etc.
Vitamins, colouring agents, pharmaceuticals and
minerals will generally form only a minor portion of the
mixture which is to be emulsified and coagulated, e.g.
up to loo by weight on a dry solids basis. Appropriate
amounts can readily be calculated from the appropriate
dosages and feed consumption rates for the creatures
receiving the feedstuff.
Carbohydrates, e.g. digestible plant starch, for
example wheat starch, will generally constitute up to
20o by weight on a dry weight basis of the mixture which
is emulsified and cooked, preferably 5 to 150.
The water content of the mixture to be emulsified
and cooked will generally be in the range 40 to 75o by
weight, for example 55 to 750 or 60 to 700, but most
preferably 45 to 600. After cooking and drying, this
will preferably be reduced to 0.5 to 700, especially
preferably 2 to 10o and more particularly 3 to 8o where
the feedstuff is to be stored before use.
In the process of the invention, the mixture to be
emulsified is preferably prepared by grinding up,
chopping or mincing the raw fish, for example whole
herring, sprat, mackerel or capelin, and then mixing in
the extra substances, e.g. wheat starch, vitamin mix,
gluten (e. g. from wheat and/or maize) and colouring
agents (e. g. astaxanthin or cantaxanthin for salmon
feed). This coarse mixture is then emulsified, e.g.
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using a microcutter such as the Simo Microcutter
MC250/115 PFVB175SS from Simo Industries A/S of Denmark.
Ir~ the Simo Microcutter, the mixture is fed at up
to 6 tonne/ hour through die plates with 4 and 2.5 mm
apertures and emulsified by rotating knife plates. The
resulting emulsion contains oil droplets of about 1 to
50 ~.m maximum dimension (e.g. diameter) and is
substantially free of larger solid particles, ie.
particles larger than 50 ~,m, other than bone fragments
which typically may be .200-500 ~.m. Typically the
proportion (e. g. by volume) of solid particles (other
than bone fragments) larger than 5 ~,m visible by light
microscopy is less than that of oil droplets of this
size or larger, for example by a factor of at least 10,
more usually at least 100. As mentioned above, the
emulsion typically has a mayonnaise-like consistency.
Viewed by light microscopy this appears to have all or
substantially all of the components of the mixture as a
continuous aqueous phase or a discontinuous oil phase.
This is readily distinguished from the pre-
emulsification mixture produced by chopping and grinding
in which solid particles deriving from the raw fish, in
particular muscle fibres and large bone fragments, are a
prominent feature and lipid droplets are larger than in
the emulsion.
After emulsification, the mixture is preferably
exposed to a partial vacuum (e.g. 0.1 to 0.9 bar) to
reduce the amount of entrained gas. This avoids the
production of a feed which will float in water as
floating feeds are not desired by salt water fish
farmers. Moreover this reduces the oxygen tension (ie.
oxygen content) and thereby reduces oxidation of the
lipids in the composition. For catfish farming however
a floating feed is desirable and degassing may be
omitted or performed less completely. The final
feedstuff desirably has a density in excess of 0.6 g/mL,
preferably in excess of 1 g/mL, more preferably in
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excess of 1.2 g/mL.
In one embodiment of the invention, following
emulsification, and if desired degassing, the emulsion
is heated to coagulate the proteins and generate a
lipid-retaining matrix. This may be done in several
ways, e.g. by passage over a heated surface, by passage
through a hot air dryer, by steam heating, by heating
with electromagnetic radiation, by infra red heating,
etc. However microwave heating is preferred.
In the heating step, the temperature and time of
heating should.be at least sufficient to coagulate the
protein and create a matrix which encapsulates the
lipid. It is not necessary that heating be effected
such as to significantly reduce the water content of the
mixture. In general, the mixture should be brought to a
temperature in the range 50 to 100°C, preferably above
78°C.
The necessary extent of heating is readily
determined in practice - with too little heating pellets
of the emulsion are soft and deformable, and they stick
together and coalesce. With sufficient heating, such
pellets are self-supporting, transportable and non-
coalescing. Too much heating is unproductive as it
destroys protein quality and lowers the nutritional
value of the feedstuff.
The heating step which coagulates the protein is
preferably effected using electromagnetic (e. g.
microwave) irradiation, e.g. at a frequency in the range
to 3000 MHz, preferably in the range 900 to 950 MHz.
The irradiation intensity is preferably in the range
0.025 to 0.5 kW per kg/hour of emulsion throughput,
especially 0.05 to 0.2 kW/kg.h-', more especially 0.075
to 0.15 kW/kg.h-1. The use of microwave frequencies of
900 to 950 MHz, especially about 915 MHz is preferred to
the use of higher frequencies due to the increased
ability to penetrate the emulsion.
Desirably the water content is reduced as little as
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possible during the coagulation step, with further
drying to the desired final moisture content being
carried out in subsequent treatment steps, e.g. using
hot air drying. For dry, storage stable feed, the final
moisture content is preferably less than loo by weight;
however for feed for use without storage, moisture
contents of up to 30o are acceptable. Moisture content
may be determined conventionally, e.g. using an infra-
red moisture analyser such as a Mettler Toledo HR73
Halogen Moisture Analyser.
Before the coagulation step, the emulsion is
preferably extruded or otherwise formed into sheets, or
more preferably "ropes" of 2 to 40 mm thickness,
especially ropes of 3 to 25 mm diameter. If desired the
emulsion may be formed in "pellets"; however it is
generally preferred to cut such ropes into pellets after
coagulation. Such pellet sizes may be for example 2 to
30 mm, preferably 3 to 20 mm.
If extruded or otherwise formed as sheets, the
coagulated emulsion may be broken into flakes, cut into
strips or otherwise transformed into particles of the
desired size.
Particularly desirably, the emulsion is formed,
e.g. into sheets or ropes, before coagulation;
coagulated; cut into pellets or strips or smaller
sheets; dried on a perforated belt in a multi-sector hot
air dryer; and if desired broken into flakes.
Especially preferably the emulsion is extruded into
ropes before coagulation, coagulated, cut into pellets
and then dried on a perforated belt in a multisector hot
air dryer. In one preferred embodiment, in an early
sector of the multi-sector dryer, air flow is through
the belt from below so as to separate the pellets while
in a later sector air flow is through the belt from
above so as to enhance the drying effect. Desirably a
still later sector is arranged to cool the dried
pellets.
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The dryer used in this embodiment of the apparatus
of the invention is conveniently a multi-sector dryer
such as those prcduced by Lindauer Dorm er GmbH, Lindau,
Germany for drying of pelletized sewage sludge.
Where the product of the process of the invention
is a feedstuff, a wide range of dryers may be used, e.g.
multisector dryers as described above, hot air drum
dryers, flash dryers, etc.
In an alternative embodiment of the invention,
following emulsification, and if desired degassing, the
emulsion is passed directly into a drying means, thus
forming a nutritional composition in granular form (e. g.
powder, grain or meal form).
The drying means may optionally be a high
temperature drying means, for example a disc-dryer, or a
lower temperature drying means, for example a vacuum
dryer, spray dryer or flash dryer. For dry, storage
stable feed-meal, the final moisture content is
preferably less than loo by weight; however for feed or
feedstuff for use without storage, moisture contents of
up to 30% are acceptable.
In one particularly preferred embodiment, the
nutritional composition is a feedstuff produced in
relatively fine grained form, e.g. pellets of 2 to 5 mm
size, or in particular meal form, substantially free of
plant carbohydrates and plant oils. This powdered or
granulated feedstuff may then be used as an ingredient
in the preparation of feed pellets by conventional
methods, e.g. by pelletization or extrusion with binders
and plant carbohydrates and addition of fish and/or
plant oils and other substances as discussed above (e. g.
vitamins, pharmaceuticals, colouring agents, etc). The
addition of fish and plant oils may be performed so as
to achieve a desired balance of fatty acid residues
(e. g. of c~-3 and c~-6 acids) in the final product, which
can be used as a human or animal (e. g. mammal, fish,
reptile, etc.) feed or food supplement.
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After drying and cooling, the nutritional
composition may be packaged for storage or transport,
e.g. in water-proof plastics containers such as sacks or
drums.
The nutritional composition produced using the
process of the invention is novel and forms a further
aspect of the present invention. Viewed from this
aspect the invention provides a nutritional composition
produceable by emulsifying and coagulating and/or drying
a mixture containing raw fish.
Viewed frr~m a further aspect the invention provides
a nutritional composition containing fish oil and fish
protein, preferably coagulated fish protein, which is
substantially free of muscle fibre fragments in excess
of 200 ~m in length, preferably a gluten-containing
composition.
The apparatus used in the process of the invention
is also novel and forms a further aspect of the
invention. Viewed from this aspect the invention
provides apparatus for production of a nutritional
composition, one embodiment of said apparatus
comprising:
a grinder arranged to produce a ground raw fish
mixture;
an emulsifier arranged to convert the ground raw
fish mixture into an emulsion;
a heater arranged to coagulate the emulsion; and
a dryer arranged to dry the coagulated emulsion.
Such apparatus preferably also comprises: a mixer
to mix into the ground raw fish mixture other optional
components such as vitamins, oils, minerals, gluten,
starch, etc; a degasser to reduce the gas content of the
emulsion; means for forming the emulsion into a desired
form for coagulation in the heater, e.g. a spreader to
produce sheets or an extruder to produce an emulsion
extrudate; and a cutter to cut the coagulated emulsion
into a desired form, e.g. a pelletizer to pelletize the
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coagulated emulsion.
A further embodiment of the apparatus of the
invention comprises:
a grinder arranged to produce a ground raw fish
mixture;
an emulsifier arranged to convert the ground raw
fish mixture into an emulsion and;
a dryer arranged to dry the emulsion.
Such apparatus preferably also comprises: a mixer
to mix into the ground. raw fish mixture other optional
components sucks as vitamins, oils, minerals, gluten,
starch, etc; a degasser to reduce the gas content of the
emulsion.
Embodiments of the process, apparatus and products
of the invention will now be described further by way of
example and with reference to the following non-limiting
Examples and to the accompanying drawings, in which:
Figure 1 is a schematic layout for an apparatus for
the performance of the process of the invention;
Figures 2 and 3 are photomicrographs of emulsions
used in the process of the invention; and
Figure 4 is a photomicrograph of a raw fish mixture
that has been subjected to grinding and chopping but not
emulsification.
Referring to Figure 1, there is shown an apparatus
1 for the performance of the process of the invention.
Raw fish (e. g. whole herring) is transferred from
receiving hopper 2 to a grinder 4 by screw feed 3. The
ground fish is fed from grinder 4 to screw mixer 6 by
screw feed 5. In screw mixer 6, a carbohydrate (wheat
starch), pigment, gluten and vitamin mixture from hopper
7 is mixed with the ground fish and the resultant
mixture is passed to a buffer mixer tank 8. The mixture
from tank 8 is pumped by pump 9 into an emulsifier 10
where it is emulsified. The emulsion is passed into
suction silo 11 and vacuum tank 12 where it is degassed
at a pressure of 0.7 bar. The degassed emulsion is
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pumped by pump 13 into extruder 14 which extrudes 12 mm
diameter emulsion ropes onto a conveyor belt 15.
Conveyor belt 15 transports the ropes of degassed
emulsion through three heating sectors of a microwave
oven 16 operating at 915 MHz. Water vapour from the
oven is removed and condensed. The coagulated ropes
leaving oven 16 are cut into pellets by cutter 17 and
the pellets are transported into a seven-sector dryer 19
by belt 18. In the first three sectors of dryer 19, hot
air is passed upwards through the perforated belt 20
carrying the pellets, and in the subsequent four sectors
hot air is passed downwardly through the perforated
belt. In a final sector, cool air is passed between the
pellets and the dried and partly cooled pellets are
subsequently sieved, cooled and bagged.
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Example 1 - formation of emulsion
The following materials are used to produce an emulsion
for feeding to a microwave oven in an apparatus
according to Figure 1:
Raw whole herring 100 parts by weight
Gluten 5.13 parts by weight
Wheat starch 4.30 parts by weight
Vitamin mixture 0.08 parts by weight
Colouring agent 0.02 parts by weight
Photomicrographs of an emulsion of raw fish and
carbohydrate produced in this way are shown in Figures 2
and 3. As can be seen, the emulsion contains oil
droplets of 1-50 ~,m size. By way of comparison, from
Figure 4 it may be seen that grinding and chopping raw
fish, as in the procedure of Hamre (supra), does not
produce such an emulsion.
The emulsion flow at 500 kg/hr is subjected to 75 kW
microwave irradiation at 915 MHz, pelletized and dried
to a moisture content of 70. The resulting feed pellets
show negligible lipid leakage.
Example 2 fat leak test
In order to demonstrate the stability of the fat in the
product of the invention, the following pressure test
was carried out.
Samples of crushed feed pellets formed by the process of
the invention and of a well mixed blend of fish meal and
fish oil were compressed in a specially designed test
apparatus. Each sample consisted of 4008 of material,
with a fat content of approximately 430 of the dry mass.
The following results were obtained:
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Pressure
/ Bar
4 8 17
Leakage Crushed 0 0 0
from pellets
sample Fish meal 28 46 58
~g~ /oil mix
The results clearly show that the product of the
invention gave no detectable fat leakage at pressures up
to 17 bar, while the comparative mixture had lost more
than 33% of its original fat content under the same
conditions.
