RU2789483C2 - Improved method for production of high-quality blood meal - Google Patents

Abstract

FIELD: feed industry.

SUBSTANCE: invention relates to a method for the production of coagulated blood meal and to a product of coagulated blood meal. A method for the production of coagulated blood meal is proposed, including subsequent stages of (i) provision of an aqueous mixture containing raw animal blood obtained from a slaughterhouse, and (ii) increase in a content of solid substances in the mixture to obtain a mixture having a content of solid substances of 20% by wt. or higher, and (iii) simultaneous drying and grinding of the resulting mixture in an air turbulent mill to obtain dried blood meal having an average particle size d50 from 20 mcm to 0.7 mm, d90 of less than 1 mm, according to the results of measurement with laser diffraction, using Beckman Coulter analyzer of a dry powder particle size, and intestinal digestibility of 85% or higher. Coagulated blood meal is proposed, obtained by the specified method, having an average particle size d50 from 20 mcm to 0.7 mm, d90 of less than 1 mm, according to the results of measurement with laser diffraction, using Beckman Coulter analyzer of a dry powder particle size, and having intestinal digestibility of 85% or higher and a moisture content of about 10% by wt. or less. The use of this coagulated blood meal as a protein dry filler and a taste booster of feed for pets or for aquacultures is also proposed.

EFFECT: invention is aimed at obtainment of high-quality blood meal with high intestinal digestibility.

42 cl, 1 tbl, 1 ex

Description

FIELD OF TECHNOLOGY

This invention relates to a method for producing high quality blood meal. This invention further relates to blood meal and to the use of blood meal in feed products.

BACKGROUND OF THE INVENTION

Besides food grade blood, which is harvested from the slaughterhouse of pigs and cattle using special tools such as hollow knives with direct anticoagulant injection, blood is usually an underestimated by-product of the slaughter of farm birds, ducks, pigs, cattle, sheep, etc. .p., despite the high content of digestible protein. However, the processing of blood usually reduces its nutritional value and/or such processing is relatively expensive. However, processing is necessary to obtain a storage-stable powdered material. Such a storage-stable material is often referred to as "blood meal".

Several methods for obtaining blood plasma and/or anticoagulated blood are described, for example, the method described in US2015/056363. However, the use of anticoagulated blood requires the addition of anticoagulants at the slaughterhouse immediately after draining the blood from animal carcasses. A method and system for collecting non-coagulated blood, and in particular poultry blood, is described in WO 01/08501 A1.

In addition, for blood intended for use in medicine, spray drying techniques are used, such as those described in US2012/027867.

Another method for drying blood for human consumption is, for example, freeze-drying as described in CN1994319 for deer blood.

The anticoagulated blood is usually separated into a plasma fraction and a hemoglobin fraction and both streams are then spray dried to produce very high nutritional value products. However, the production is complicated due to the need to work in a slaughterhouse, and spray drying is relatively expensive. In addition, the presence of an anticoagulant often results in additional ash or organic materials that reduce the amino acid value of the product.

In the absence of special measures to prevent coagulation, the slaughterhouse produces partially coagulated blood as a by-product. Such a blood by-product is naturally coagulated but still contains dissolved proteins such as plasma proteins. Such a blood by-product is obtained by collecting waste streams of blood, and the resulting side stream is usually diluted with water due to the use of water for washing. Said blood by-product is typically a heterogeneous mixture of coagulated and non-coagulated blood particles, blood compounds, blood proteins, partially hemolyzed blood cells, and additional water, with a solids content of about 5-18% wt.

Said (partially coagulated) blood by-product is usually processed to initially produce fully coagulated blood. Complete coagulation is usually achieved by steaming and this step is usually carried out in a blood meal plant. Typically, the coagulated blood is then subjected to a concentration step and dried in a disk dryer, circulation dryer, or the like.

Continuous production for making blood meal from coagulated blood is described in, for example, US3431118 and US3450537. US4067119 describes the use of a tumble dryer, and GB2303042 describes a new general process for coagulating, decanting (and/or centrifuging), drying on a disk dryer, and grinding to about 1 mm particles. In addition, a method is known for drying coagulated blood in an annular or evaporative dryer, in which blood particles are blown into a drying tube.

Blood meal can be used as a complementary protein material in feed products such as pet food, aquaculture feed, and the like.

Particularly for industrial applications such as aquafeed, it is important that the nutritional value is high. Such products require, for example, a high degree of protein digestibility, which can be achieved by spray drying, but at a relatively high cost. Spray-dried material is now a hallmark of high quality blood meal.

SUMMARY OF THE INVENTION

The object of the present invention is to provide a method for producing blood meal from raw whole blood, crude hemoglobin fractions and/or crude plasma, which has a high nutritional value and can be produced efficiently.

A further object of the present invention is to obtain a blood meal from coagulated blood with a higher degree of digestibility and preferably with improved other properties than hitherto known.

This objective of the present invention is achieved thanks to a method for producing blood meal, including successive steps (i) providing an aqueous mixture containing raw blood, preferably having a solids content of from about 5% wt. up to 18% wt., and (ii) increasing the solids content in the mixture to obtain a mixture having a solids content of about 20% wt. or higher, preferably between about 20-80 wt.%, and (iii) simultaneously drying and grinding the resulting mixture in an air turbulent mill to obtain a dried blood meal having an average particle size (d50) from 20 μm to 0.7 mm, d90 less than 1 mm as measured by laser diffraction using a Beckman Coulter dry powder particle size analyzer, and an intestinal digestibility of about 85% or more, preferably about 87% or more, and more preferably about 90% or more.

In addition, the present invention provides a coagulated blood meal product having an average particle size (d50) of 20 µm to 0.7 mm and a d90 of less than 1 mm as measured by laser diffraction using a Beckman Coulter dry powder particle size analyzer, and having an intestinal digestibility of about 85% or more, preferably about 87% or more, and even more preferably about 90% or more, and having a moisture content of less than 15% wt., preferably less than 10% wt.

The method and product of the present invention provide a number of advantages:

Efficient drying in a short time provides a product with excellent quality parameters, such as, for example, an intestinal digestibility of preferably 85% or higher, or even 87% or higher, for example 90%. Typically, coagulated blood dried on a disk dryer has an intestinal digestibility of 60-75%, and material dried on an evaporative, ring or drum dryer can have an intestinal digestibility of up to 84%.

In addition, such a product may have an apparent digestibility ratio (ADC) in rainbow trout of about 80% or more based on crude protein, preferably about 85% or more, and even more preferably 87% or more.

In addition, the availability of lysine is very high. Lysine is an amino acid that often limits the growth of poultry or pigs. The availability of lysine in the product obtained by the method of this invention is usually about 92% or more, preferably about 95% or more, relative to the total lysine content.

In addition, the product obtained by the method of this invention may have a more uniform, lighter color, with virtually no black inclusions.

In addition, the smell is improved (smell is weaker) compared to regular blood meal.

In addition, the proposed method is effective in the sense that up to five operations can be carried out on one relatively simple installation. In conventional processes, the operations of drying, grinding, micronization, cooling and screening are carried out at different stages, while the proposed method allows the implementation of these 5 stages in one operation. In addition, a short processing time of a few seconds is possible.

The proposed method can be used with anticoagulated blood, crude hemoglobin and/or crude plasma fractions as an alternative to spray drying with the advantage that much less equipment is needed.

The method of this invention has the additional advantage of eliminating the significant risk of microbiological contamination of the dried product with Salmonella and the like. The absence of dead zones in an air turbulent mill due to the turbulence created by the high speed rotation of the rotor and the gas flow, and the easy possibility of increasing the temperature of the gas stream, if necessary, during the process cycle or before or after the process cycle, are important factors to prevent accumulation of product or cold spots and therefore it prevents and eliminates microbiological contamination.

In a further aspect of the present invention, the air turbulent mill feed is treated to pasteurize or even sterilize it. Such treatment preferably includes a sufficiently long heat treatment at a sufficiently high temperature, taking into account the moisture content of the stream, resulting in a pasteurized or sterile product stream. The combination of a sufficiently high temperature for a sufficiently long period of time at a given solids content is known to those skilled in the art. The pasteurization or sterilization step may be carried out in a separate heat exchanger and/or may be combined with an existing process step.

The proposed method does not require any special equipment in the slaughterhouse, which is necessary, for example, to obtain non-coagulated blood, which is used for spray drying, it is possible to use anticoagulated blood, fractions of crude hemoglobin and/or crude plasma mixed with (partially) coagulated blood, or in the form of separate streams of raw materials.

DETAILED DESCRIPTION OF THE INVENTION

The term "about" means plus or minus 20%, preferably plus or minus 10%, more preferably plus or minus 5%, most preferably plus or minus 2%.

Raw materials

Raw blood can be obtained from various animals such as poultry (including chickens, turkeys), ducks, pigs, cattle (including cows, horses, goats), sheep, etc., which are processed in slaughterhouses. You can use mixtures of animal blood.

In the context of this invention, "raw blood" may be a major blood fraction such as hemoglobin, plasma, or mixtures thereof with whole blood.

In a preferred embodiment, the raw blood is from chickens, turkeys, ducks, pigs, sheep or cows, or mixtures thereof.

Raw blood is usually collected from the slaughterhouse as anticoagulated blood or as a mixture of partially coagulated blood (coagulated blood particles), dissolved proteins, in particular hemolyzed blood cells, and water (collectively: partially coagulated blood).

Food grade blood is usually drained from the carcass of an animal (mainly pigs and cows) using a "hollow knife" that is inserted directly into the jugular vein of the animal, and the anticoagulant is injected directly into the knife or a few centimeters after it; in other cases, the blood drains into a collection channel with continuous injection of anticoagulants into the blood stream.

Non-food grade blood is usually not injected with anticoagulants and is drained from the animal carcass directly onto the floor or into a collection pan that is periodically flushed with water to facilitate blood flow to a drain point where the blood is sucked up by a pump and pumped to a storage tank.

Although anticoagulated blood, crude hemoglobin fractions and/or crude plasma fractions are usually food grade, their batches may not be up to standard and such anticoagulated crude blood or fractions thereof may be used as such or may be mixed with partially coagulated crude blood in the method according to this invention for the production of feed additives.

Alternatively, uncoagulated blood, food grade crude hemoglobin and/or crude plasma fractions can be processed in accordance with the method of this invention to produce food grade blood meal.

The amount of solids in raw blood is usually from about 5% wt. up to 18% wt. and usually from 8% wt. up to 12% wt., although this invention can be implemented using a different solids content.

The blood in the body of an animal typically has a solids content of about 17% wt. up to 19% wt. Because non-edible grade raw blood typically becomes diluted with water as a result of washing and cleaning the blood collection and effluent system in the slaughterhouse, the solids content becomes less than 17% wt., typically less than 14% wt., but more likely about 12% wt. or less. In a poultry slaughterhouse, additional dilution with water may occur due to runoff of water from the heads of birds immediately after the water bath of the electrical stunning station.

Raw blood for use in the present invention preferably has a high protein content (typically greater than 80 wt. % dry matter) containing at least 17 amino acids. The protein content is usually determined by measuring the total nitrogen content and multiplying the total nitrogen content by the so-called Jones factor of 6.25. The result is the theoretical amount of protein. Typically, raw blood contains 80 to 95% protein on a solids basis.

Preferably, when processing anticoagulated blood, it can be used as it is, or it can be fractionated. In some processes, plasma is separated from the hemoglobin fraction, such as by centrifugation. The hemoglobin fraction has an increased solids content (due to separation from plasma) compared to raw blood, and it is usually about 30-40% wt. solid. Due to this increase in solids content, the hemoglobin fraction can be used as a raw material for an air turbulent mill, or the solids content can be further increased as described below for other blood fractions.

The plasma fraction of anticoagulated blood after separation of the hemoglobin fraction usually contains 4-8% wt. solids, and the content of solids in it must be increased, which can be achieved, for example, ultrafiltration to a solids content, for example, 25-30% wt. The resulting mixture can then be processed like the other blood mixtures described below.

Preferably, raw blood, in particular raw blood not subject to anticoagulation, is first filtered on a movable or stationary filter device to remove foreign materials such as animal parts (mainly feathers and heads) and trimmings.

The solids content of the raw blood is increased to ensure sufficient drying in the air turbulent mill. Preferably, the solids content is increased by 10% or more, preferably by 20% wt. or more, for example, with a solids content of 18 to 28% wt. (increase by 10% wt.) or 12% wt. up to 32% wt. (increase by 20% wt.). Even more preferably, the increase in solids content is about 30% wt. or more. As is clear from the above, raw blood does not necessarily reflect the composition of whole raw blood, but may be a fraction of it.

In a preferred embodiment, the blood solids content is increased to about 20 to about 60% by weight, preferably from about 40 to about 60% by weight.

In a first preferred embodiment, the raw blood is treated to (further) coagulate the blood and hence increase the solids content.

The resulting coagulated blood is called fully coagulated blood or coagulated blood. In practice, not all protein is coagulated, although the content of coagulated or denatured proteins is significantly higher than in a partially coagulated blood mixture or in anticoagulated blood.

The coagulation treatment can be carried out mechanically, with heat, steam and/or with the use of chemicals. Chemical coagulation of industrial animal blood can be achieved using, for example, aluminum sulfate, zinc sulfate, methanol and acetone (see Andrew L. Ratermann, H. Wayne Burnett, Vaughn Vandegrift; J. Agric. Food Chem., 1980, 28: 438-441).

Preferably, the coagulation is carried out mechanically and/or by heat treatment. Even more preferably, the partially coagulated blood is further coagulated by direct contact with and mixing with live steam.

The additional coagulation also serves to homogenize the partially coagulated blood mixture.

The coagulation treatment is preferably carried out so that the raw blood obtained is well pasteurized or even sterile. The coagulation treatment is preferably carried out at a temperature greater than 80°C, preferably greater than 90°C, and even more preferably greater than 95°C, for a sufficiently long time, commonly referred to as the heat kill time, to achieve a pasteurized or substantially sterile product stream. The temperature is usually around 150°C or less. Sufficient time may range from a few seconds to one hour or more, depending on the temperature at which the product stream is treated. Higher temperatures require shorter processing times, as will be known to those skilled in the art. A time of about half an hour or less is generally preferred, and even more preferably about 10 minutes or less. Often an acceptable time is 1 minute or more, such as two minutes or more, or three minutes or more.

A suitable combination of temperature/time, for example, can be realized with steam treatment in the coagulation step. Such high temperature treatment preferably includes directly applying steam, which increases the temperature of the product stream to about 80°C or higher, or preferably 90°C or higher, or even more preferably about 95°C or higher, and maintaining the coagulated blood stream at a temperature of from about 80°C to 95°C or more for the entire period of time, for example 2-10 minutes.

Preferably, the pasteurization conditions are such that the processing temperature/time is at least equivalent to 85°C, preferably 90°C, or even more preferably 95°C for 2 minutes at a solids content of 10% wt.

More generally, for raw blood, including anticoagulated blood, a defined blood fraction, partially coagulated blood, clotted blood, or mixtures thereof, processing methods known for pasteurizing or sterilizing milk or fruit juices can be used.

Preferably, the flow after the pasteurization/sterilization step complies with the requirements described in the technical regulations for animal by-products (No. 1069/2009 and No. 142/2011) with regard to Salmonella and Enterobacteriaceae, as well as Enteric Clostridia. Preferably, the mixture containing raw blood is treated at a sufficiently high temperature for a sufficiently long time to achieve the heat kill time of Salmonella and Clostridia enteritis, and Salmonella and Clostridial enteritis are not detected in standard assays in accordance with the specified technical standards for animal by-products.

The clotted blood is preferably dehydrated to increase the solids content of the clotted blood to about 20-60% by weight. solids on a dry basis, preferably 40-60% solids on a dry basis. Water can be removed by evaporation or mechanically by pressing the blood clot through a sieve, centrifugation or ultrafiltration. The clotted blood is preferably centrifuged to remove water from the clotted blood. Evaporation can be carried out, for example, under reduced pressure, for example at a temperature of 30-60°C.

In addition, you can further increase the solids content by drying in standard drying equipment, for example, up to 80% wt. solids or more, preferably up to a value after which the digestibility of the semi-dried product begins to decline sharply. This moisture content may vary depending on the type of pre-drying equipment used. In a preferred embodiment, the solids content is increased to about 60%.

Residual water, commonly referred to as blood water, which is obtained, for example, after centrifugation, may contain from 1 to 5% wt. or usually from 1 to 4% wt. solids. Blood water is a waste stream that can be concentrated, for example, up to 15-40% wt. solids by ultrafiltration, among other methods, and the concentrated stream can be subjected to, for example, spray drying, but preferably it is returned to the process for drying in an air turbulent mill. Alternatively, blood water can be considered as a waste stream that can be treated in a water treatment plant.

Preferably, the dried blood meal is again mixed with the concentrated blood water stream, and the resulting mixture can be directly fed into the air turbulent mill, or it can be mixed into the main clotted blood stream before being fed into the air turbulent mill.

When clotted blood is used, it may be appropriate to use back-mixing of the dried blood meal with the air turbulent mill feed stream to (further) increase the solids content of the air turbulent mill feed.

In a second, alternative, preferred embodiment, raw blood as received from the slaughterhouse can be homogenized and increased in solids content without the need for additional coagulation, for example, using live steam.

Homogenization is especially appropriate when processing partially coagulated blood because it is a heterogeneous material. Homogenization can be carried out in a container or by feeding the blood mixture into an air turbulent mill using conventional homogenization equipment available such as a mixer. Preferably, the homogenization step reduces the size of large particles having a size of more than 1 cm.

An increase in the solids content of such raw blood can be achieved, for example, by back-mixing the blood meal with the air turbulent mill feed stream and/or by evaporating the water from said mixture.

The increase in solids content is preferably at least partially carried out by back-mixing the blood meal into the raw blood mixture stream before it is fed into the air turbulent mill. The increase in solids content can be further achieved by evaporating the water under reduced pressure. Preferably, the temperature during these treatments is maintained at or below about 100°C (boiling point of water), preferably 80°C or less, preferably about 70°C or below, and even more preferably about 60°C or below.

Therefore, as a rule, a mixture of raw blood obtained from a slaughterhouse can be homogenized and increase the solids content from less than 14 wt.%, usually less than about 10-12 wt.%, to at least 20 wt.%, and more preferably up to about 40% wt. or more, for example, up to 50% wt. by removing water and/or adding dried blood meal and/or concentrated blood mixture to the air turbulent mill feed stream.

In the case of removal of water from a raw blood mixture, for example by evaporation used as part of the solids raising step, the solids content of the air turbulent mill feed stream prior to the addition of the backmix stream is typically about 20-40%. wt., for example, about 30% wt.

In the case of adding blood meal to the raw blood stream as the only measure to increase the solids content, the solids content of the mixed stream fed to the air turbulent mill is typically about 50% wt. or less.

Then the homogenized, at least partially coagulated blood with a solids content, preferably increased to a value of more than 40 wt.%, can be dried as a mixture in an air turbulent mill.

In one embodiment of the present invention, the clotted blood mixture is fed into an air turbulent mill with a moisture content of preferably 40-60% wt.

In another embodiment, the optionally homogenized raw blood mixture, after increasing the solids content, is fed to the air turbulent mill at a solids content of 20-55% wt., preferably with a solids content of 30-50% wt.

Drying process and air turbulent mill with accessories

The solids-enhanced blood mixture is dried and ground according to step (iii) of the present invention.

Typically, the blood mixture is dried to a moisture content of about 15% wt. or below. In a preferred embodiment of the invention, the blood mixture is dried to a moisture content of about 10% wt. or less, preferably about 8% wt. or less. Drying to a moisture content of less than about 4% by weight is usually not necessary, but will not cause harm. Most preferably, drying is carried out such that the dried blood meal has a moisture content of about 5% to 7% by weight. As a result of drying, a product is obtained that is stable during storage.

In a preferred embodiment, the dried blood meal is divided into a product stream and a recycle stream.

The product leaving the air turbulent mill may contain a relatively small amount of ultrafine product, too large particles that can be ground, or other unsuitable material, which is preferably separated on the classifier. The unusable material is preferably recycled (used for back mixing) into the air turbulent mill feed stream.

Preferably, if more backmix material can be used, then a portion of the suitable product is used as a recycle stream for backmixing with the air turbulent mill feed.

The recycle stream (back-blending dried blood meal) can be used in accordance with the present invention to increase the solids content of the air turbulent mill feed stream.

Drying is an important step for the final quality of blood meal.

Apparently, conventional technologies for drying clotted blood lead to a decrease in digestibility.

In a preferred embodiment of the present invention, the drying in step (iii) is carried out at about atmospheric pressure to produce fine particles, so that the drying is very efficient. Atmospheric pressure includes a low vacuum, which is often used to facilitate gas flow and powder transport. The powder can exit the dry cyclone with an air lock rotary valve. The pressure before the mill can be from -5 to -8 mbar, and after the mill - from -30 to -50 mbar.

For example, drying in a traditional disc dryer typically provides an intestinal digestibility of about 60-75%. Dried in a ring, evaporator, or tumble dryer, blood meal (also referred to as flash dried meal) can have an intestinal digestibility of about 84%.

Preferably, the concentrated blood mixture obtained in step (ii) is dried in a manner providing low heat damage so that the reduction in digestibility during drying is limited and the blood meal has an intestinal digestibility remaining above 85%, preferably about 87-93%. eg 90-92%.

Preferably, the concentrated blood mixture obtained in step (ii) is dried in a low heat damage manner such that the blood meal preferably has an Apparent Digestibility Index (ADC) in rainbow trout of about 85% or higher, based on crude protein.

For example, drying in a conventional disc dryer typically produces a blood meal with an ADC value on rainbow trout of 65% or lower, based on crude protein.

In order to obtain such material with low thermal damage, the authors of the present invention found that drying must be carried out using a gas flow and simultaneous grinding of the material, which provides a very short processing time.

The present inventors have found that a further improvement in the in vitro digestibility and nutritional characteristics of blood meal can be achieved using an air turbulent mill, since the fine particles resulting from grinding contribute to the rapid drying of the concentrated blood mixture and therefore limit the effect of heat on the product.

Thus, in accordance with the present invention, the increased solids blood mixture obtained in step (ii) is subjected to simultaneous drying and grinding using a gas flow, usually air (which may have a reduced oxygen content), in an air turbulent mill. Said gas may also be superheated steam. An air turbulent mill can provide the advantage of fast grinding and drying, and the use of an air turbulent mill according to the present invention results in drying and simultaneous grinding or crushing of the blood mixture by supplying the drying material and a gas flow, usually air, to a high speed rotor in a closed chamber.

An air turbulent mill typically comprises a chamber (stator) with appropriate inlets and outlets for the product and gas stream(s) in which is mounted a rotating element (rotor) with rows of impact devices which the rotating element can rotate at high speed. The inner walls of the stator are preferably lined with impact elements, such as corrugated sheets, to increase the grinding efficiency due to additional frictional and shear forces. The rotor is usually mounted vertically with respect to the outlet.

There are several types of air turbulent mills. They are commonly referred to as turbulent air mills or vortex air mills. The present invention provides for the use of all of them under the description of "air turbulent mill". It is preferable to use vertically arranged rotors because they consume less energy.

Air turbulent mills known in the art from Atritor (Cell Mill), Hosokawa (Drymeister), Larsson (Whirl flash), Jäckering (Ultra Rotor), Rotormill or Görgens Mahltechnik (TurboRotor) can be used for drying and grinding according to the invention. ). Some of these air turbulent mills are described in, for example, US4747550 and WO1995/028513.

The air turbulent mill may include a classifier to separate larger and smaller particles. The use of a classifier allows the larger particles to be returned to the grinder while the smaller particles pass through for further processing. In another embodiment, two or more grades of particulate blood meal, with different particle sizes and bulk properties, are prepared using two orifices at the outlet of the classifier.

Drying is carried out using a gas flow fed into a high-speed rotor. The gas stream is typically air, which may have a low oxygen content, but may also be superheated steam. The inlet temperature is typically from about 20°C to 500°C, preferably from about 20°C to 450°C, and even more preferably from about 20°C to 180°C. When operating at the upper end of the temperature range, careful handling and/or less heated gas may be required. For example, a heated gas at about 450°C and a second room temperature gas stream may be used if high gas velocities are required.

The outlet air temperature is usually below 100°C, preferably below 90°C. The inlet gas temperature may be lower if the raw concentrated blood mixture is at a higher temperature.

The air consumption is usually about 5 m ³ /h per kg of raw material or more, preferably about 7 m ³ /h per kg of raw material. Typically, its consumption is about 50 m ³ /h or less, preferably about 30 m ³ /h per kg of raw material or less. In particular, most preferably, said flow rate is, for example, from 5 to 30 m ³ /h, for example 7-20 m ³ /h per kg of feed product.

The gas stream can be supplied to the mill directly with the feedstock or indirectly where the concentrated blood mixture is supplied at one location and the gas stream is supplied to the air turbulent mill separately at one or more other locations. The product can, for example, be fed directly into the bottom side of the mill or mixed with the air stream just before the mill. Alternatively, the feed product can be directly introduced through the inlet flange on the side of the mill body.

The air turbulent mill used according to the present invention preferably comprises a closed chamber (stator) with appropriate inlets and outlets for product and gas flow, in which a vertically mounted shaft (rotor) mounted with groups of cutting and impact devices such as blades, discs , plates, etc., rotates at high speed. The internal walls of the stator can be lined with corrugated sheets to increase the grinding efficiency due to additional friction and shear forces.

The rotor typically rotates at a tip speed of about 20 m/s or more, more preferably about 35 m/s or more, even more preferably about 50 m/s or more. Typically, said speed is about 250 m/s or less, preferably about 150 m/s or less. A suitable speed is, for example, about 75 m/s. Typically, the tip speed is about 80 m/s or more, preferably about 110 m/s or more.

The grinder can generate a significant amount of heat. In addition, the incoming wet concentrated blood mixture may have a temperature above room temperature. If appropriate, the gas stream can be heated, for example, by direct heating in a gas burner (which also reduces the oxygen content, which reduces the risk of ignition) or by indirect heating through a steam or hot oil heat exchanger. The gas stream may also be superheated steam.

Air turbulent mill contains one or more inlets for gaseous flow. One or more of said gas streams may be heated. If one gas stream is heated, it is preferably heated to a temperature of about 50°C or higher.

The gaseous stream can be introduced in various ways. Typically, the main gas stream is introduced at the bottom of the air turbulent mill. Said inlet may be the same inlet through which the wet product is fed. In such a case, the gas stream is usually used to transport the product. The second gas stream can be used to influence the grinding and flow characteristics of the mill. In particular, if the product is difficult to transport with a gas stream, it can be directly introduced into the mill using a screw or pump.

In order to maintain high digestibility of the blood meal, the average residence time in the air turbulent mill is preferably short, such as less than 10 s, preferably less than 5 s, more preferably less than 2 s, even more preferably less than 1 s. The short average residence time of the material before drying in the mill ensures efficient drying with only a relatively small increase in temperature of the coagulated blood material. If a classifier is used, the average residence time will be longer, but the time that the powder is actually in the grinder preferably remains less than 10 seconds, and even more preferably less than 5 seconds.

Preferably, the temperature of the blood meal leaving the air turbulent mill is in the temperature range from about 30°C to 90°C, more preferably from about 40°C to 80°C, even more preferably from about 45°C to 75°C. .

The gas stream exits the air turbulent mill, optionally through a classifier, with the dried product. The dry product in the form of fine particles is separated from the gas stream, and this separation is usually carried out in one or more cyclones, preferably one or two cyclones, or with a bag filter, or a combination of both.

It is possible to further classify the resulting powder leaving the cyclone, for example, on a horizontal sieve to screen out particles of unsuitable size, large particles and/or to remove dust. In addition, various grades of blood meal can be obtained, with smaller and larger particle sizes.

Screen waste (unsuitable particles and/or dust) is preferably re-introduced into the feedstock for further processing in an air turbulent mill. Mixing waste with wet raw material (also referred to as "back-mixing") can improve loading operation and increase overall drying and grinding efficiency. As described above, said waste can be mixed with a concentrated effluent resulting from an increase in solids, such as blood water, and then mixed with the primary blood stream.

Depending on the feedstock for the air turbulent mill, it may be advantageous to provide significant back-mixing, for example back-mixing 40-80 wt. finished dry product with raw materials to increase the solids content of raw materials, while improving the overall characteristics of the product.

Thus, more generally, it is preferable to back-mix the blood meal with the crude or coagulated blood stream that is fed into the air turbulent mill. The amount of backmix material may depend on the solids content of the air turbulent mill feed stream. Usually the amount of material for back mixing is from 1% wt. up to 90% wt. (dried material), preferably 2-80% wt. A low amount of backmix material is preferably used when only material that is out of specification needs to be backmixed. To provide a significant increase (for example, more than 5%) of the solids content, the proportion of material for backmixing is preferably 5-90%, more preferably 10-80% wt.

In a preferred embodiment, if the solids content of the air turbulent mill feed stream (without backmixing) is about 20 wt. or higher, preferably 30% wt. or higher, the amount of material for back-mixing is preferably such that the stream supplied to the air turbulent mill contains about 40% wt. solids or more. Thus, for example, suitable is the amount of material for back-mixing, comprising from about 40% wt. up to about 90% wt., if the feed stream contains about 20% wt. solids, and from about 10% wt. up to about 70% wt., if the specified stream contains about 30% wt. solids.

The indicated amounts are expressed in % wt. dry product to be back-mixed with the feed stream. The proportion of material to be backmixed can also be determined from the solids content of the feed stream (before backmixing). For a stream containing about 20% wt. solids, the ratio for back mixing can be about 200-400%, preferably 200-300%, and for a stream containing about 30% wt. solids, the backmix ratio can be from about 50% to 200%.

Preferably, the classification is carried out using a sieve (or other classifier) with a cutoff of 1 mm or less, preferably 800 microns or less. Classification can be carried out, for example, using a sieve with a cut-off of 300 µm, 500 µm or 900 µm.

In addition, the flow of air entering the air turbulent mill can be adjusted to change the residence time and/or particle size. For example, the air flow directly affects the residence time in the chamber and the contact time with the grinding device; the higher the flow rate, the shorter the residence time and therefore the larger the particles, and vice versa, the lower the air flow rate, the smaller the particles. The particle size is further influenced by the classifier and/or the appropriate impact and cutting devices, as well as the suitable surface profile of the inner walls. Those skilled in the art can adjust the air turbulent mill to obtain the desired particle size.

Prepared blood meal

The blood meal material is subsequently used as a dry product with a moisture content of about 15% by weight. or less, preferably about 10% wt. or less (i.e. blood meal).

Said material preferably contains less than 8% moisture. Most preferably, the dried material has a moisture content of 5 to 7% by weight.

Blood meal according to this invention usually contains from about 85% wt. up to about 98% wt. protein in terms of dry weight.

Advantageously, the blood meal produced in accordance with the method of this invention can provide a valuable source of protein and/or a source of amino acids in animal feed. For example, blood meal may provide a source of one or more of the following amino acids: methionine, cysteine, lysine, threonine, arginine, isoleucine, leucine, valine, histidine, phenylalanine, glycine, serine, proline, alanine, aspartic acid, tyrosine, tryptophan, and glutamic acid. acid. High digestibility provides a higher efficiency of the specified product as a feed additive, compared with the clotted blood of the prior art.

The intestinal digestibility is about 85% or more, preferably about 87% or more, and even more preferably about 90% or more.

Pepsin digestibility, as measured according to ISO 6655 (August, 1997), of all blood meal grades is relatively high (>95%) and therefore this analytical method does not sufficiently differentiate blood meal of different quality classes. Intestinal digestibility is more sensitive to processing.

The blood meal of the present invention demonstrates high digestibility in in vivo experiments with surgically decapsulated roosters and rainbow trout.

In addition, the bioavailability of lysine is also very high in the products obtained by the method of this invention.

The clotted (or coagulated) blood meal product obtained by the process of the present invention is believed to be a novel product. Clotted blood meal, like other dried fully coagulated blood products, shows precipitation of most of the product within 24 hours of being dispersed in water, while spray-dried, non-coagulated product remains largely dispersed for this period of time and therefore shows no precipitation for the specified time.

The present invention provides a coagulated blood meal product having an average particle size (d50) of 20 µm to 0.7 mm and a d90 of less than 1 mm as measured by laser diffraction using a Beckman Coulter dry powder particle size analyzer, and said product has an intestinal digestibility of about 85% or more, preferably about 87% or more, and even more preferably about 90% or more.

The content of bioavailable lysine in the coagulated blood meal is preferably about 92% or more, even more preferably about 94% or more, relative to the total lysine content.

The apparent digestibility ratio (ADC) of rainbow trout coagulated blood meal is preferably about 80% or more, even more preferably about 85% or more, and most preferably about 87% or more relative to crude protein. The proposed blood meal contains at least 17 amino acids, preferably at least 18 amino acids, such as lysine.

Preferably, the amount of lysine is about 7% wt. or more relative to the total protein content.

The proposed blood meal is rich in heme iron, which is the most bioavailable form of iron.

The properties of the powder described below apply to all products that can be obtained by the method of this invention, and therefore refer to blood meal obtained from coagulated blood, anticoagulated blood and/or a mixture of both. They also refer to whole blood hemoglobin fraction and/or whole blood plasma fraction and/or any mixtures of hemoglobin fraction, plasma fraction, coagulated blood and anticoagulated blood.

The dried and ground material leaving the air turbulent mill is usually in the form of particles, of which more than about 99% wt. are less than a few mm in size, such as less than about 2 mm, preferably less than 1 mm. Typically, more than about 95% wt. the particles are larger than about 8 microns to provide a free flowing powder that can be easily handled and further processed into, for example, formulated pet foods and animal foods.

In a preferred embodiment, the mean particle size of the product after classification (defined as d50; 50% v/v particle coarser and 50% finer), as measured by laser diffraction on a Beckman Coulter particle size analyzer using standard software, is between about 20 µm to about 0.7 mm, preferably about 20 µm to about 500 µm, more preferably about 40 µm or more, and more preferably about 50 µm to about 300 µm. For example, the average particle size is about 75 or about 150 microns.

The d90 value is preferably less than 1 mm, more preferably less than about 0.7 mm. The d10 value is preferably greater than about 10 microns, and more preferably greater than about 15 microns.

The dimensions described above are highly preferred. Steam-coagulated blood dried in a standard disc or tumble dryer, or blood dried by freeze-drying, has a coarse, heterogeneous particle size distribution at the exit of the dryer with a significant number of particles larger than 1.8 mm and very often larger than 2 mm or higher , which necessitates the use of additional crushing and screening equipment and, consequently, additional requirements for the production area and additional problems associated with dust emissions. Therefore, such equipment is a less promising technological installation.

The particle size distribution of the blood meal of the present invention is relatively uniform. For example, d90 divided by d10 is about 12 or less, preferably about 10 or less, with d90 being about 1 mm or less.

The blood meal obtained by the method of the present invention is in the form of a powder, preferably with powder characteristics such that said powder has high flow properties, packaging characteristics, as well as dosing characteristics for formulating pet food and animal food.

The Hausner ratio of the powders of the present invention (shocked bulk density divided by bulk bulk density) is about 1.06-1.18, i.e. preferably less than 1.2, which is considered an indication of good flowability.

In a preferred embodiment of the present invention, the blood meal has a bulk density of about 0.35 g/cm ³ or higher, more preferably about 0.45 g/cm ³ or higher, even more preferably about 0.5 g/cm ³ or higher. Typically, the bulk density is about 0.7 g/cm ³ or less, for example, about 0.6 g/cm ³ or less.

In a further preferred embodiment of the present invention, the blood meal has a tapped bulk density of about 0.4 g/cm ³ or higher, more preferably about 0.5 g/cm ³ or higher, and even more preferably about 0.55 g/cm ³ or higher. Typically, the tapped bulk density is about 0.75 g/cm ³ or less, for example, about 0.65 g/cm ³ or less.

In an additional embodiment, the implementation of the blood meal can be granulated to increase its density in order to optimize the volume and transportation costs.

In addition, blood meal prepared in accordance with the method described herein has a significantly lower odor than conventional disc dryer-dried blood meal. High turbulence, very short residence time, no contact with hot surfaces (unlike a disc dryer) and no deposits on the inner walls (unlike a spray dryer and unlike channels in a ring dryer) prevent the formation of burnt particles and odorous compounds.

Drying and grinding in an air turbulent mill has the additional advantage that the color of the resulting material is lighter and more uniform than classically dried material. In particular, there are practically no black blotches.

The blood meal of the present invention is preferably free of Salmonella found in standard assays.

To improve oxidative stability and flowability, an antioxidant and/or an anti-caking agent can be added to the blood meal, respectively.

In a preferred embodiment, the antioxidant is added as a liquid or solid and mixed with the concentrated blood mixture prior to being fed into the turbulent mill to ensure uniform incorporation and to prevent unwanted inclusions and agglomeration if said incorporation is in the finished powder. When backmixing using dry blood meal and therefore a dry product that already contains an antioxidant, the amount of antioxidant added to the fresh wet stream is adjusted accordingly.

Some amino acids can be added to blood meal before or after drying. In particular, it may be appropriate to add isoleucine, cysteine and/or methionine, or edible proteins containing these amino acids in relatively large amounts, since the amount of these amino acids in blood meal is relatively low. Typically, the added amount is about 20% wt. or less, preferably about 10% wt. or less.

Blood meal can be packaged in small bags, big bags or other bulk containers. Dried blood meal can be packaged and transported in any bulk container, big bag or other container.

Blood meal can be used as a feed, as a feed additive, for example in pet food and/or aquaculture feed. The proposed material can be used in the form of a powder, or it can be used to obtain larger dosage units in the form of granules, flakes, and the like. using traditional manufacturing technologies. Blood meal can be used as a carrier for other ingredients and/or can be used as a dry diluent.

When used to make feed products, the blood meal prepared in accordance with the present invention may be used in combination with one or more of: a nutritionally acceptable carrier or dry diluent, a nutritionally acceptable diluent, a nutritionally acceptable adjuvant, a nutritionally acceptable adjuvant, or a nutritionally active ingredient . The blood meal itself can be a carrier or dry diluent for other functional ingredients such as flavoring agents, palatability agents and attractants.

The method of this invention can be easily applied in standard plants processing at least partially coagulated blood, anticoagulated blood, their fractions and/or mixtures thereof, since the air turbulent mill with an optional classifier, cyclone and air supply device takes up significantly less space, than conventional disc dryer or other conventional dryers with accessories. Thus, the present invention also relates to a method for upgrading a blood meal plant by replacing the conventional drying equipment with an air turbulent mill and a cyclone with auxiliary equipment, or by adding such an air turbulent mill after the conventional drying equipment and operating the conventional equipment to a higher residual content. moisture and final drying in an air turbulent mill.

MEASUREMENT METHODS

The following methods were used in the examples and are suitable as methods for measuring the parameters specified in the description and claims:

Moisture content in mass percent (% wt.): the wet material is dried overnight in a vacuum oven under reduced pressure and with a desiccant. The material is weighed before and after the drying step and the amount of moisture is calculated, taking the initial measured mass as 100% and assuming that all volatile material is water.

The solids content is defined as the amount of solids remaining after removal of water, as described for determining % wt. moisture.

Sedimentation analysis: 3 g of blood meal is added to 100 ml of water in a transparent beaker at room temperature and stirred for 1 minute. The glass is left to stand for 24 hours. Then a photograph is taken and the presence of a visible clear precipitate or a homogeneous dark liquid is determined.

Pepsin digestibility is measured according to ISO 6655 (August 1997) using a concentration of 0.02% pepsin in hydrochloric acid in accordance with the above reference.

Intestinal digestibility (also referred to as Boysen digestibility) is measured according to the methods described by S. Boisen in "Prediction of the apparent ileal digestibility of protein and amino acids in feedstuffs for pigs by in vitro analysis", Animal Feed Science Technology, 51, pp. 29-43 (1995) and further described in "In vitro analysis for determining standardized ileal digestibility of protein and amino acids in actual batches of feedstuffs and diets for pigs"; Livestock Science, 309: ss. 182-185 (2007).

Particle size distribution is measured by laser diffraction on a Beckman Coulter particle size analyzer in a dry powder system. Use the manufacturer's standard software. Results are reported as d10, d50, d90, etc., which refer to volume fractions.

Bulk density and shaken density are measured with a shaking volumemeter type STAVB II manufactured by Engelsmann. According to the manufacturer's brochure, the apparatus is used to determine volumes before and after compaction, compaction and tapping density in accordance with the European Pharmacopoeia, DIN ISO 787 part 11, ISO 3953, ISO 8967 and ASTM B 527-93.

Lysine was measured according to ISO 5510:1984, measuring bioavailable lysine and total lysine to determine their ratio.

Experiments to determine the coefficient of apparent digestibility (ADC) were carried out on rainbow trout using a model test in triplicate (3 tanks of 15 trout). The water in the tanks was regulated at 17°C +/- 0.5°C, the oxygen content was controlled and maintained at 9.5 ppm. at the inlet, nitrogen was removed with a biological filter, and the light period for the fish was set to 12 hours. The fish were fed ad libitum twice a day. Feed was formulated by mixing 20% of the test ingredient with 80% of a reference diet containing fish food (75%), starch, wheat gluten, premix of minerals and vitamins, and yttrium as an inert marker; the mixture was extruded into 4 mm pellets using a Clextral twin screw extruder, and fish oil was introduced into the resulting pellets under vacuum. The initial average weight of trout ranged from 100 to 120 grams. The tanks were equipped with an automatic excrement collection system. Feces were collected only after one week to acclimate the fish to the medium in the tank and to the food to stabilize the ADC values. Feces were collected once a day before morning feeding, frozen and then freeze dried before analysis. ADC values were calculated indirectly according to the Maynard and Loosli formula (Maynard and Loosli, Animal Nutrition, 6th edition, McGraw Hill, New York, 1969).

Analysis in surgically removed cecum roosters: In vivo digestibility analysis of crude protein, dry matter and amino acids was performed at a specialized institute using a duplicate model. Two groups of three cocks with surgically removed caecum were not fed for 24 hours and then force-fed the exact amount of the prescription feed containing the dried blood sample to be analyzed. The total collection of excrement, including endogenous losses, was carried out within 48 hours. The excrement was cleaned to remove foreign matter such as feathers and then frozen, lyophilized and homogenized. Digestibility ratios were then calculated by comparing the content of crude protein, dry matter and total amino acids measured in dry blood samples and in lyophilized feces after adjusting for endogenous losses.

With regard to the materials and methods described in this document, additional modifications can be made in addition to those described above, without departing from the essence and scope of this invention.

Accordingly, while specific embodiments of the invention are described, the following are examples only and do not limit the scope of the present invention.

EXAMPLES

Raw partially coagulated blood was purchased from a slaughterhouse. It contained >90% poultry blood. The solids content was about 10%.

The crude partially coagulated blood was further coagulated with live steam (approximately 150 kg of steam per ton of partially coagulated blood) and the clotted blood was concentrated in a centrifuge to obtain a mixture of clotted blood with a solids content of about 40% wt.

The clotted blood mixture was dried in an air turbulent mill (JÄCKERING, model Ultra Rotor III a), with a feed rate of 200 kg/h of the concentrated blood mixture. The clotted blood mixture was dried and ground in several cycles. The air turbulent mill was operated at an inlet gas (air) temperature of 160°C. The amount of gas was from about 15 to 30 m ³ /h*kg. The speed of the rotor tip was from 80 to 90 m/s.

The average residence time of the product was estimated to be less than about 1 second. During drying and grinding, the blood meal presumably did not reach temperatures above about 80°C, since the air temperature at the outlet of the air turbulent mill was about 90°C. The product was sieved through a 30 µm sieve and further characterization of the fraction with smaller particle size was carried out as described below. The fraction (about 2-5% wt.) with a large particle size in one run was returned to the raw stream for the air turbulent mill; this cycle was completed successfully.

The resulting product was compared with blood meal dried in the traditional way (disk dryer); in a conventional ring dryer and also compared with spray-dried blood meal. It should be understood that the spray-dried material is derived from anticoagulated blood, otherwise clogging of the spray nozzles will occur.

Several characteristics were compared. According to the table, the following conclusions can be drawn:

- Intestinal digestibility (Boisen digestibility) is higher for the product obtained by the method of this invention, compared to conventionally dried blood clot products.

- In vivo digestibility in surgically decolonized roosters is much higher for the product of this invention compared to conventionally dried clotted product, and is nearly equal to spray dried blood meal.

- The apparent digestibility coefficient (ADC) of rainbow trout in terms of crude protein is much higher for the product obtained by the method of this invention, compared to conventionally dried coagulated blood products.

- The bioavailability of lysine, which is an important measure for bioavailable amino acids, is significantly higher for the product of this invention, also compared to the spray-dried product.

- The product obtained by the method according to this invention can have the same fine particle size distribution as in spray drying. Using the process of the invention, a narrower particle size distribution can be achieved. However, it should be noted that a coarser material can be easily obtained by classifying, for example, at 1 mm instead of 300 μm.

- Sedimentation analysis shows that blood meal from clotted blood shows the formation of a clear sediment, in contrast to blood meal dried by spray drying.

In addition (not indicated in the table), the color of the product obtained by the method of this invention is lighter and more uniform than that of clotting products dried by conventional drying methods. In addition, the product obtained by the method of this invention has a significantly lower odor (neutral or low odor) compared to conventionally dried clot products.

The process according to the invention makes it possible to produce an exceptionally high quality blood meal, with a content of bioavailable lysine significantly higher than the best quality blood meal known hitherto (spray dried blood meal).

The air turbulent mill process is substantially less expensive and easier to operate than spray drying, and provides a quality that is substantially comparable, if not superior, to that of the spray dried product, which is of great advantage.

Claims (42)

1. A method for producing coagulated blood meal, comprising the successive steps of (i) providing an aqueous mixture containing raw animal blood obtained from a slaughterhouse, and (ii) increasing the solids content of the mixture to obtain a mixture having a solids content of 20% wt. or higher, and (iii) simultaneously drying and grinding the resulting mixture in an air turbulent mill to obtain a dried blood meal having an average particle size d50 from 20 μm to 0.7 mm, d90 less than 1 mm, as measured by laser diffraction using an analyzer particle size of Beckman Coulter dry powder, and an intestinal digestibility of 85% or greater. 2. The method according to p. 1, characterized in that the aqueous mixture in stage (i) has a solids content of from 5 to 18% wt. 3. The method according to p. 1 or 2, characterized in that in stage (ii) the solids content of the mixture is increased to obtain a mixture having a solids content between 20-80% wt. 4. The method according to any one of the preceding claims, characterized in that the blood meal in step (iii) has an intestinal digestibility of 87% or higher. 5. The method according to any one of the preceding claims, characterized in that the blood meal in step (iii) has an intestinal digestibility of 90% or higher. 6. The method according to any one of the preceding claims, characterized in that the aqueous mixture of step (i) is subjected to a coagulation step, and an increased solids content is subsequently achieved by removing part of the water, obtaining a clotted blood mixture having a solids content of between 30-70% wt. 7. The method according to p. 6, characterized in that the stage of coagulation is carried out using live steam. 8. The method according to p. 6 or 7, characterized in that the mixture of clotted blood has a solids content between 40-60% wt. 9. The method according to p. 1, characterized in that the aqueous mixture containing raw blood has a solids content of less than 18% wt., and the mixture is optionally homogenized and processed to increase the solids content to a solids content of 30% wt. or more by removing water and/or adding dried blood meal and/or concentrated blood in step (ii). 10. The method according to p. 9, characterized in that the aqueous mixture containing raw blood has a solids content of less than 12% wt. 11. The method according to p. 9 or 10, characterized in that at least part of the specified increase in solids content is achieved by back mixing dry blood meal with the specified mixture, while the amount of blood meal for back mixing is from 2 to 90% wt. , and the specified amount is expressed in wt.%. relative to the dry product sent for back-mixing to the feed stream to the air turbulent mill. 12. The method according to p. 11, characterized in that the amount of blood meal for back mixing is from 10 to 80% wt. 13. The method according to any one of the preceding paragraphs, characterized in that the solids content in stage (ii) is increased by 10% wt. or more. 14. The method according to p. 13, characterized in that the solids content in stage (ii) is increased by 20% wt. or more. 15. A method according to any one of the preceding claims, wherein the mixture containing raw blood is treated at a sufficiently high temperature for a sufficiently long time to ensure pasteurization or sterilization of the mixture before it is fed into the air turbulent mill. 16. The method according to p. 15, characterized in that the pasteurization conditions are such that the temperature/processing time is at least equivalent to 85°C for 2 minutes with a solids content of 10% wt. 17. The method according to p. 16, characterized in that the temperature/treatment time is at least equivalent to 90°C for 2 minutes with a solids content of 10% wt. 18. The method according to p. 16 or 17, characterized in that the temperature/treatment time is at least equivalent to 95°C for 2 minutes with a solids content of 10% wt. 19. The method according to any one of paragraphs. 15-18, characterized in that the mixture containing raw blood is treated at a sufficiently high temperature for a sufficiently long period of time to achieve the time of heat death of Salmonella and enteric clostridia. 20. The method according to any of the preceding claims, characterized in that the simultaneous drying and grinding is carried out at such a temperature that the temperature of the dried and ground material is maintained at 90°C or less. 21. The method of claim. 20, characterized in that the temperature of the dried and ground material is maintained at 80°C or less. 22. The method according to claim 20 or 21, characterized in that the temperature of the dried and crushed material is maintained at a level of less than 60°C. 23. Method according to any one of the preceding claims, characterized in that the air turbulent mill comprises a chamber with respective inlets and outlets for product and gas stream(s), in which a rotating element with rows of percussion devices is mounted, and said rotating element can rotate with high speed, and the rotating element rotates with a tip speed of 35-250 m/s. 24. The method according to claim 23, characterized in that the inner walls of the stator are lined with impact elements. 25. The method according to any one of the preceding claims, characterized in that the air turbulent mill contains an internal or external classifying device that allows the coarse material to be returned to the mill. 26. The method according to any one of the preceding claims, characterized in that the air turbulent mill is operated using a gas flow at a temperature of from 20 to 500 ° C, and the speed of said gas flow is from 5 to 50 m ³ /h per kg of raw material , and said flow can be adjusted to change the particle size of the dried blood meal and the residence time is less than 10 seconds. 27. The method according to claim 26, characterized in that the gas stream is air with an optionally reduced oxygen content. 28. The method according to p. 26 or 27, characterized in that the air turbulent mill is operated using a gas flow at a temperature of from 20 to 450°C. 29. Coagulated blood meal obtained by the method according to any one of paragraphs. 1-28 having an average particle size d50 of 20 µm to 0.7 mm, d90 less than 1 mm as measured by laser diffraction using a Beckman Coulter dry powder particle size analyzer, and having an intestinal digestibility of 85% or higher, and a moisture content about 10% wt. or less. 30. Blood meal according to claim 29, characterized in that its intestinal digestibility is 87% or higher. 31. Blood meal according to claim 29 or 30, characterized in that its intestinal digestibility is 90% or higher. 32. Blood meal according to any one of paragraphs. 29-31, characterized in that the moisture content in it is 5-8% wt. 33. Blood meal according to any one of paragraphs. 29-32, characterized in that said blood meal has a bioavailable lysine content of 92% or higher. 34. Blood meal according to claim 33, characterized in that said blood meal has a bioavailable lysine content of 94% or higher. 35. Blood meal according to any one of paragraphs. 29-34, characterized in that the index of apparent digestibility of blood meal in rainbow trout is 80% or higher in terms of crude protein. 36. Blood meal according to claim 35, characterized in that the index of apparent digestibility of blood meal in rainbow trout is 85% or higher in terms of crude protein. 37. Blood meal according to claim 35, characterized in that the index of apparent digestibility of blood meal in rainbow trout is 87% or higher in terms of crude protein. 38. Blood meal according to any one of paragraphs. 29-37, characterized in that the blood meal has an average particle size d50 of 20 µm to 0.5 mm as measured by laser diffraction using a Beckman Coulter dry powder particle size analyzer. 39. Blood meal according to claim 38, characterized in that the blood meal has an average particle size d50 from 50 to 300 microns. 40. Blood meal according to any one of paragraphs. 29-39, characterized in that the blood meal has a d90 particle size of 0.7 mm or less as measured by laser diffraction using a Beckman Coulter dry powder particle size analyzer, and/or that the blood meal has a d10 particle size of 10 µm or greater as measured by laser diffraction using a Beckman Coulter dry powder particle size analyzer. 41. Blood meal according to claim 40, characterized in that the blood meal has a particle size d10 of 15 µm or more. 42. The use of coagulated blood meal according to any one of paragraphs. 29-41 as a protein powder and flavor enhancer in pet food or aquaculture.