Process for valorizing insect larvae, composition obtained and use in animal feed

Abstract

Short title: Process for valorizing insect larvae, composition obtained and use in animal feed. Process for preparing an insect larva composition from a medium containing live insect larvae and substrate residue particles, comprising at least one air separation step to obtain said insect larvae on the one hand and substrate residue particles having a density different from the density of the insect larvae on the other hand, and a heat treatment step of said insect larvae at a temperature ranging from 85°C to 105°C for a duration ranging from 1 to 15 minutes, and insect paste obtained by this process. Short figure: None

Description

Title of the invention: Process for valorizing insect larvae, composition obtained and use in animal feed. Technical field of the invention

[0001] The present invention relates to the field of the valorization of insect larvae. More particularly, it relates to a process for preparing a composition from insect larvae, the resulting wet composition, and its use as a product for animal feed, and in particular for aquaculture and pet food. State of the art

[0002] With the increase in the world's population and the resulting strain on natural resources, the recycling of agricultural and agri-food industry residues, as well as the fight against food waste, are more relevant than ever. After decades during which the disposal of these residues (undersized, unsold, or expired products, residues from primary processing industries) essentially consisted of dumping them in landfills, stakeholders in the agricultural sector have gradually become interested in their recovery. In particular, recovery solutions through composting or methanization have been developed. For about ten years, research has focused on a more refined recovery method, making it possible to recycle nutrients, and particularly proteins, for animal feed: the bioconversion of these residues using insect larvae.

[0003] Indeed, the increase in the world's population and its standard of living also puts pressure on global meat and fish consumption. However, one of the factors limiting livestock production is the availability of proteins to be incorporated into their feed, which come mainly from soybean cultivation or fishmeal from ocean fisheries, the sustainability of which is increasingly being questioned.

[0004] Insect farming, both for recycling agricultural and agri-food waste and as a source of protein for animal feed, is a solution recommended by the Food and Agriculture Organization of the United Nations (FAO). The use of Hermetia illucens larvae, in particular, has proven to be a promising technical solution.

[0005] The evolution of European regulations in 2017 (EU Regulation 2017 / 893 followed by others) which authorized the introduction of insect proteins into formulations for animal feed has opened up the possibility of developing a new circular industrial economy on these technical bases.

[0006] Thus, patent application WO2022177422Al already describes a process for preparing insect paste. This process is implemented using washed larvae and includes a step of heating the paste followed by a two-stage cooling; it does not describe the process according to the invention comprising an air separation step followed by heat treatment.

[0007] There remains, however, a need for new processes for preparing compositions for animal feed based on insect larvae, particularly usable in "wet" form in the manufacture of formulations for animals, and especially for pets.

[0008] Regarding the microbiological aspect, manufacturers of finished wet products do not generally require any particular specifications relating to the protein raw material because the production lines of the final product systematically incorporate a sterilization step.

[0009] More generally, category 3 of animal by-products (according to European Regulation (EC) No 1069 / 2009) to which wet compositions based on insect larvae belong is not subject to particular regulatory constraints on the microbiological level.

[0010] Nevertheless, wet compositions based on insect larvae with a "good sanitary condition" and a safety comparable to that of mechanically separated offal or meat available on the market are still sought. Disclosure of the invention

[0011] The solution proposed by the present invention is a method for preparing a composition of insect larvae from a medium containing live insect larvae and substrate residue particles, said method comprising at least the following steps, in this order: - an aerodynamic separation step to obtain said insect larvae on the one hand and substrate residue particles having a different density than the density of insect larvae on the other hand; - a stage of collecting insect larvae; - a heat treatment step of said insect larvae at a temperature ranging from 85°C to 105°C, preferably for a period of 1 to 15 minutes, preferably ranging from 4 to 12 minutes.

[0012] Surprisingly and advantageously, the process according to the invention makes it possible to obtain a composition with a level of safety comparable to that of mechanically separated offal and meat available on the market. However, unlike Of these, the composition obtained according to the invention is made from whole larvae, that is to say, including both the external cuticles and the digestive tract of the larvae with their contents, which gives said composition a higher natural microbial load than conventional meats and offal. However, this microbial load could pose a risk to the stability of their preservation.

[0013] Preferably, the heat treatment step of the process according to the invention is carried out using dry steam.

[0014] The process according to the present invention makes it possible to avoid washing insect larvae with water, which saves water and avoids the need for subsequent drying steps, as well as wastewater treatment.

[0015] More generally, the process according to the invention is relatively economical in terms of energy used and makes it possible to manufacture a good quality composition in a reasonable time.

[0016] The composition obtained after heat treatment can be used directly in the manufacture of animal feed products.

[0017] Advantageously, the heat treatment step is followed by a vigorous grinding step to obtain the insect larvae in paste form. This preferred variant of the process according to the invention makes it possible to offer manufacturers a neutral product in which the presence of insect larvae is not directly detectable. Thus, the insect larvae can be incorporated into ready-to-eat animal feed without instinctive or cultural aversions to insects causing rejection.

[0018] According to a preferred mode, the heat treatment step of the process of the invention is followed by a grinding step so as to obtain a composition comprising more than 85% of particles with a particle size less than 3 10 4m and less than 0.5% of particles with a particle size greater than 2 103 m.

[0019] According to another preferred method, the composition obtained is cooled to a temperature of 4°C in a period less than or equal to 10 hours and then frozen at a temperature below -18°C, preferably ranging from -18°C to -40°C.

[0020] The process according to the present invention, particularly when it includes the two preferred modes described above, makes it possible to obtain a moist composition, in the form of a paste, which does not vary from one production run to another and which is stable for several months until its use. This allows the frozen paste to be used at a later date, several weeks or even months after its preparation.

[0021] The invention also relates to the composition that can be obtained by the process according to the invention.

[0022] The invention further aims at the use of the composition according to the invention for animal feed, preferably for aquaculture or pet food. Detailed description

[0023] The preparation process according to the present invention is carried out using a medium comprising live insect larvae and substrate residue particles.

[0024] Insect larvae are reared in a medium referred to as a "rearing medium" or "feeding substrate"; in this text, these two expressions are used to designate the same medium. At the end of the rearing period, this medium comprises, in addition to the larvae, particles of substrate residue.

[0025] The substrate residue particles consist of digested feeding substrate particles, i.e. larval excrement, also called "frass", as well as non-digestible larval feeding substrate particles such as cellulosic fibers or woody parts.

[0026] The insect larvae used are generally less than 15 days old. The insect larvae are introduced approximately 5 to 7 days after the eggs hatch into the feeding substrate where they are reared for 6 to 10 days. The larvae used in the process of the invention are alive.

[0027] All kinds of insect larvae can be used in the process according to the invention, preferably the insect larvae are those of the species Hermetia illucens (known as black soldier fly).

[0028] Generally, the insect larvae of the species Hermetia illucens have, at the time of implementation of the preparation process according to the invention, a weight between 8 10 2 g and 2.5 10 1 g, a length between 10 103 m and 20 103 m and a width between 3 103 m and 6 103 m.

[0029] As already mentioned, the process according to the invention comprises at least the following two steps: an air separation step and a heat treatment step.

[0030] Depending on the quality of the medium containing the insect larvae, which depends essentially on the initial composition of the rearing medium and the progress of its digestion by the larvae, the air separation stage can be preceded by at least one preliminary separation stage, in particular by sieving. Air separation

[0031] Aerodynamic separation aims to separate insect larvae from substrate residue particles, i.e. the different particles present in the environment according to their density, by means of an airflow.

[0032] At the end of the air separation stage, the insect larvae are substantially free of substrate residue particles, i.e. the rate of substrate residue particles is less than 5% by dry weight of the whole insect larvae and substrate residue particles.

[0033] Naturally, the various operating parameters of the air separator to be applied will depend on the air separator model chosen. It is within the expertise of a person skilled in the art to define the operating parameters of the air separator according to its geometry in order to implement the air separation defined in the present invention.

[0034] Generally the operating parameter is essentially the air velocity, advantageously the aerodynamic separation is carried out by means of an airflow whose velocity ranges from 5 to 8 m / s.

[0035] The air velocity (a function of the air flow rate and the passage cross-section of the device) is the main physical parameter for adjusting the equipment which determines the efficiency of the air separation.

[0036] In addition, air separation is generally carried out on substrate residue particles with a water content of 40 to 60% and insect larvae with a water content of 65 to 75%.

[0037] When the insect larvae are Hermetia illucens fly larvae, then the aerodynamic separation step is carried out in such a way as to separate the insect larvae having a density of 0.6 to 0.8 g / cm3 on the one hand and the substrate residue particles having a density of less than 0.6 g / cm3 on the other hand.

[0038] The treatment of insect larvae generates odors which can be a source of annoyance for operators, therefore, according to a preferred mode of the invention, the air separation is carried out in a device in which the air circulates in a closed circuit.

[0039] This preferred mode has the advantage of reducing odors generated by the treatment of insect larvae and reducing subsequent operations related to air treatment.

[0040] At the end of this step, the insect larvae are collected; this step may consist of a simple conveyance, for example by means of a hopper, from the area where the air separation step is carried out to the area where the heat treatment step is carried out. Thermal treatment

[0041] The air separation step is followed by a heat treatment step. The air separation step and the heat treatment step can be carried out without an intermediate pause step or by carrying out an intermediate pause step of between 1 hour and 24 hours.

[0042] Advantageously, the air separation step and the heat treatment step are carried out without an intermediate pause step.

[0043] The heat treatment step is carried out at a temperature ranging from 85°C to 105°C, preferably 95°C for a duration ranging from 1 to 15 minutes, preferably ranging from 4 to 12 minutes.

[0044] This temperature corresponds to the temperature of the treated larvae.

[0045] This treatment, at this temperature, allows both the instantaneous killing of insect larvae, the inactivation of digestive enzymes present in the digestive tract of the larvae, and their sanitization, i.e. the drastic reduction of the microbial load of the larvae.

[0046] Preferably, this treatment is carried out using dry steam.

[0047] By "dry steam" or "saturated steam" we mean water vapor heated to a high temperature, above 95°C and ideally 135°C, and containing less than 5%, by volume, of water in the liquid state.

[0048] Thus the dry steam used in the heat treatment according to the invention is generally injected at a temperature ranging from 100°C to 135°C.

[0049] The heat treatment step using dry steam has the advantage of preventing the larvae from absorbing water, thus reducing the dry matter content of the product and eliminating the need for a draining or drying step. Furthermore, the injection of dry steam under pressure, generally between 1 and 4 bar, suspends the larvae in the steam stream, ensuring optimal heat exchange. This means that each larva is directly enveloped by the heating fluid, leading first to the instantaneous killing of the larvae and then to their sanitization.

[0050] According to a first particular embodiment, the heat treatment step is carried out as follows. The clean larvae are introduced into a closed metal cylinder having a slope of 10% to 20% via a hopper located at the lower end of said cylinder. The cylinder includes a screw with a diameter only slightly smaller than that of the cylinder, which rotates slowly to gently mix the mass of larvae while directing them towards the upper end of the cylinder. Nozzles are arranged at regular intervals along the lower end of the cylinder to inject dry steam under pressure beneath the mass of larvae, which helps to disperse them. An opening located at the upper end of the cylinder allows the treated larvae to be collected.

[0051] According to a second particular embodiment, the heat treatment step is carried out by means of a horizontal rotating cylinder equipped with a shankless screw and steam injection nozzles located on the wall of said cylinder. According to this second particular embodiment, the larvae are introduced at one end of the cylinder, and the rotational movement of the The cylinder causes the mass of larvae to be mixed within the volume of the cylinder. The larvae are thus mixed and brought into contact with the steam flow as they move towards the opposite end of the cylinder, where they are collected.

[0052] As already mentioned, the process according to the invention comprising at least the following two steps: an air separation step and a heat treatment allows obtaining a composition of insect larvae exhibiting good sanitary condition and a safety identical to that of the cam-treated products available on the market such as offal or mechanically separated meats. Preliminary sieving step(s)

[0053] The air separation step may be preceded by at least one preliminary separation step, in particular by sieving.

[0054] Indeed, the composition of the medium used in the process according to the invention can vary depending on the nature of the organic residues initially present in the rearing medium for the insect larvae. Consequently, depending on the proportion and size of the substrate residue particles in the medium at the end of the larval rearing period, the separation of larvae from substrate residue particles can be carried out by means of a single air separation step or by means of an air separation step preceded by at least one sieving step.

[0055] Advantageously, the air separation step is preceded by at least one sieving step for separating insect larvae, preferably using a sieve, advantageously vibrating, with a mesh size ranging from 10³ m to 10² m and a length ranging from 2.5 x 10² m to 6 x 10² m. This preliminary sieving step allows the air separation step to be carried out under more favorable conditions, on a medium already freed of some of the substrate residue particles, thus improving the performance of the air separation step. The preliminary sieving step also allows the use of a smaller air separator with lower energy consumption, while ensuring the same result and / or better larval cleanliness.

[0056] According to a preferred embodiment of the invention, a two-stage sieving is carried out before the air separation stage.

[0057] In particular, the two-stage sieving is carried out using two sieves: a coarse mesh sieve positioned on the upper stage and a finer mesh sieve positioned on the lower stage.

[0058] During this implementation of the process, the substrate, which includes insect larvae and substrate residue particles, is poured into the inlet of the first vibrating longitudinal sieve, located on the upper level. The vibration of the sieve is configured to allow the medium to be treated to spread across the width of the sieve, to separate / disperse its constituents and then to convey them to the end of the sieve.

[0059] The sieve positioned on the upper level has rectangular meshes slightly larger than the larvae, for example, with a width ranging from 5 x 10³ m to 10² m and a length ranging from 2.5 x 10² m to 6 x 10² m. Thus, substrate residue particles larger than these dimensions, such as pieces of undigested organic residue, clumps of fiber, pits, or fruit peels, remain on the sieve and are discharged at the end of said sieve. The larvae and fine substrate residue particles, such as small grain hulls, gradually pass through the meshes and fall onto the second vibrating sieve with finer meshes positioned on the lower level.

[0060] The second vibrating sieve is placed perpendicular to the first, so that the particles passing through the mesh of the first sieve are immediately distributed over the entire width of the second sieve. The second sieve, positioned on the lower level, has rectangular meshes of a size slightly smaller than that of the larvae, for example, with a width ranging from 1 x 10³ m to 5 x 10³ m and a length ranging from 2.5 x 10² m to 6 x 10² m.

[0061] The vibration frequency and the sieve length are adjusted so that the movement gradually causes the separation of the larvae and substrate residue particles and the conveyance of the larvae and substrate residue particles of a size close to the size of the larvae towards the end of the sieve, while the smaller particles fall through the mesh.

[0062] The larvae and substrate residue particles of a size close to the size of the larvae are recovered at the end of the sieve.

[0063] Advantageously, when the insect larvae are of the species Hermetia illucens, the air separation step is preceded by a sieving separation of the insect larvae comprising at least the following steps, in this order:

[0064] coarse sieving using a rectangular mesh sieve with a width ranging from 5 x 10³ m to 10² m and a length ranging from 2.5 x 10² m to 6 x 10² m,

[0065] fine sieving using a rectangular mesh sieve with a width ranging from 103 m to 5 103 m and a length ranging from 2.5 102 m to 6 102 m. Grinding

[0066] According to a preferred mode, a grinding step is carried out after the heat treatment step.

[0067] The composition used for the grinding step advantageously comprises 65 to 75% by weight of water relative to the total weight of the composition.

[0068] Advantageously, the heat treatment step is followed by a grinding step so as to obtain a composition comprising more than 85% of particles with a particle size less than 3 10 4 m and less than 0.5% of particles with a particle size greater than 2 103 m.

[0069] The grinding step is generally carried out by a high-speed rotary action, in particular by the action of several stages of knives rotating at high speed in front of a succession of screens with decreasing mesh size. Thus, given the water and fat content of the insect larvae, the grinding step leads to the formation of a paste that is a stable emulsion, that is to say, one that does not separate even after more than 48 hours of storage, and even after thawing of the frozen paste.

[0070] When the grinding step is carried out immediately after the heat treatment step, without interruption, the temperature of the emulsion ranges from 85 to 95°C.

[0071] The composition is then cooled or allowed to cool. Advantageously, in order to preserve the good sanitary condition and freshness of the composition, the cooling time until reaching 4°C should be less than 10 hours.

[0072] The composition obtained is a wet composition advantageously comprising 65 to 75% by weight of water relative to the total weight of the composition.

[0073] Freezing

[0074] The resulting paste is preferably stored frozen at a temperature below -18°C and preferably ranging from -18°C to -40°C. Freezing prevents microbial growth and the resumption of all enzymatic and physicochemical reactions.

[0075] The following examples are intended to illustrate the invention without limiting its scope. Examples

[0076] Example 1 - Implementation of the method according to the invention

[0077] Fly larvae of the species Hermetia illucens were introduced at 5 days of age after hatching from eggs into a feeding substrate composed of various finely ground organic residues of plant origin. After 8 days of fattening, these larvae digested all of the substrate and grew to an average weight of 10¹ g.

[0078] 6,106 g (6,000 kg) of the medium comprising the larvae and particles of residue of substrate (substrate digestion residues) were collected.

[0079] These 6,106 g of medium were treated by the process according to the invention in 6 steps presented below.

[0080] The medium was introduced into a two-stage vibrating sieve system.

[0081] Step 1

[0082] The sieving system includes, on the upper stage, a rectangular vibrating sieve with rectangular meshes of size 8 10 3 m X 5 102 m, allowing movement of the larvae in the longitudinal direction of the sieve.

[0083] This first sieving allows the separation and elimination of particles of undigested substrate residue such as crusts, clumps of fibers, pieces of kernels, which are retained above the sieve while the larvae and finer particles of substrate residue such as digested substrate particles pass through the sieve to reach the lower stage.

[0084] Step 2

[0085] The sieving system includes on the lower stage a rectangular vibrating sieve, placed perpendicularly to the sieve of the upper stage and having rectangular meshes of size 1.5 10 3 m X 5.2 102 m allowing movement of the larvae in the longitudinal direction of the sieve.

[0086] The finer particles of digested substrate residue pass through this second sieve, while the larvae and substrate residue particles of a size comparable to the larvae themselves are retained above and directed to a collection hopper. The larvae thus separated remain contaminated by substrate residue particles of a size comparable to the larvae themselves.

[0087] Following these two sievings, 2.9106 g of material consisting mainly of larvae but also particles of substrate residue of dimensions equivalent to those of larvae were recovered.

[0088] Step 3

[0089] These 2.9 106 g of material were introduced into an air separator, marketed by SAS RITEC under the reference separator ZZ 160-500 where the mixture of larvae and residues is poured into an air stream having an air speed of 5 to 8 m / s.

[0090] This air separator uses an upward airflow inside a vertical zigzag duct. The configuration of said duct lengthens the path of the particles and accelerates the air velocity.

[0091] According to this step, the medium containing larvae and substrate residue particles of comparable size to the larvae themselves is introduced at the upper end of the vertical duct and comes into contact with the upward airflow.

[0092] Thus, light particles with a density less than 6105 g / m³ are carried by the upward airflow and collected in a cyclone positioned at a distance. The light particles are collected at the bottom of the cyclone where a sluice gate has been placed.

[0093] The air freed from substrate residue particles, recovered at the top of the cyclone, is returned via a closed circuit to the lower part of the zig-zag duct.

[0094] The cleaned larvae are evacuated via a sluice gate positioned below the zig-zag conduit.

[0095] This aerodynamic separation made it possible to separate the larvae with a density of approximately 6 to 8 105 g / m3 (0.6 to 0.8 tonne / m3) from the particles with a lower density and thus to recover 2.55 106 g of larvae.

[0096] Step 4

[0097] The 2.55 x 10⁶ g of larvae were then subjected to dry steam heat treatment. Dry steam at 135°C was introduced at a flow rate such that the temperature inside the apparatus was maintained at a constant 95°C. The flow rate of larvae fed into the apparatus and the rotational speed of the internal screw that advances the mass of larvae within the apparatus were adjusted so that the residence time of the larvae in the apparatus, which was maintained at 95°C, was 6 minutes.

[0098] Step 5

[0099] The larvae were then ground using a KS FD175 type 112# 35620 KARL SCHNELL refiner at a speed of 2970 rpm and with a set of screens of decreasing size from 102 m to 4 10 3 m. Due to the high rotation speed of the apparatus and the fat content of the larvae, the product obtained is in the form of a thick emulsion, i.e. a paste, with a particle size of 85% less than 3 10 4 m and less than 0.5% greater than 2 10 3 m.

[0100] At the end of this step, it is not possible to recognize the presence of larval fragments with the naked eye. The temperature of the emulsion at the outlet of the apparatus is 90-95°C.

[0101] Step 6

[0102] The emulsion is then preserved by freezing at -18 °C.

[0103] In order to prevent any risk of product degradation or microbial growth, the emulsion is cooled from 90-95°C to 4°C in less than 10 hours. Example 2 - Determination of the microbial load

[0104] The larvae of Hermetia illucens feed on degraded organic matter and are therefore immersed in a vast community of microorganisms. The bacteria present on the outer cuticles and in the digestive tract of the larvae belong to different taxonomic groups, some of which may pose a risk to food safety.

[0105] Table 1 presents the microbiological data in CFU / g measured on samples taken at different stages of the process presented in Example 1.

[0106] Sample A corresponds to a sample of live larvae taken before step 3 (air separation) of example 1.

[0107] Sample B corresponds to a sample taken at the end of step 4 (heat treatment) of example 1.

[0108] [Tables] Average in live larvae A (number of samples) Average of treated larvae B Enterobacteriaceae at 37°C 1,358,238 (42) < 100 Clostridium perfringens 243 (41) < 10 Presumptive Bacillus cereus 2,205 (42) < 100 E. coli B glucuronidase+ 444,195 (41) < 100 Coagulase-positive Staphylococci 24,753 (38) < 10 Yeasts Molds 100,988 (42) < 10

[0109] The results show that the process according to the invention makes it possible to significantly reduce the levels of microorganisms that present health risks.

[0110] Example 3 - Determination of the quantity of biogenic amines in frozen compositions

[0111] The analyses were carried out on samples from different batches taken after step 6 (freezing) of example 1 and for different storage times at -18°C.

[0112] The “freshness” of the samples is conventionally assessed by the determination of biogenic amines.

[0113] Table 2 presents the levels of biogenic amines in mg / kg of the frozen composition samples.

[0114] [Tables2] CDEF Samples Storage Time at -18°C (days) 15 10 7 28 Histamine <5 7.25 2.02 14.5 Cadaverine 7 7.82 2.57 20.3 Putrescine 6 15.8 6.91 32.2 Sperminin 12 11 14.6 15.1 Tyramine <5 2.13 <1 2.19 Tryptamine <5 <5 <5 <5 2 Phenylethylamine <5 <1 <1 <1 Spermidine 52 62.4 49.4 58.5

[0115] It is observed that the concentrations of biogenic amines remain low and in all cases below the thresholds of acceptability for those presenting such thresholds: Histamine <30 ppm, Cadaverine<100 ppm, Putrescine<100 ppm. Example 3 - Visual Aspect

[0116] The evolution of the colour of the compositions according to the invention, not frozen, was compared to that of a control composition, not frozen, which had not undergone the heat treatment step.

[0117] It has been observed that the compositions according to the invention exhibit a light and stable color for a period of at least 6 hours. In contrast, the unheat-treated control composition instantly turns light brown and then darkens to black in less than 15 minutes.

[0118] The process according to the invention makes it possible to avoid a browning of the compositions obtained, indicative of the neutralization of the enzymes responsible for the autolysis of the product.

Claims

Demands

1. A method for preparing a composition of insect larvae from a medium containing live insect larvae and substrate residue particles, said method comprising at least the following steps, in this order: - an aerodynamic separation step to obtain said insect larvae on the one hand and substrate residue particles having a density different from the density of the insect larvae on the other hand; - a step of recovering the insect larvae; - a step of heat-treating said insect larvae at a temperature of 85°C to 105°C, for a period of 1 to 15 minutes, preferably 4 to 12 minutes.

2. A method according to claim 1 wherein the heat treatment step is carried out using dry steam.

3. A method according to claim 1 or 2 wherein the air separation step is preceded by at least one separation step by sieving insect larvae, preferably using a sieve, advantageously vibrating, with mesh sizes ranging from 103 m to 102 m and from 2.5 x 102 m to 6 x 102 m in length.

4. A method according to any one of claims 1 to 3 wherein the insect larvae are those of the species Hermetia illucens.

5. A method according to claim 4 wherein the aerodynamic separation step is carried out so as to separate insect larvae having a density of 0.6 to 0.8 g / cm3 on the one hand and substrate residue particles having a density of less than 0.6 g / cm3 on the other hand.

6. A method according to claim 4 or 5 wherein the air separation step is preceded by a sieving separation of insect larvae comprising at least the following steps, in this order:

7.

8.

9.

10. - coarse sieving using a rectangular mesh sieve with a width ranging from 5 x 10³ m to 10² m and a length ranging from 2.5 x 10² m to 6 x 10² m, - fine sieving using a rectangular mesh sieve with a width ranging from 103 m to 5103 m and a length ranging from 2.5102 m to 6102 m. A process according to any one of the preceding claims, wherein the heat treatment step is followed by a grinding step so as to obtain a composition comprising more than 85% of particles with a particle size less than 3 x 10⁴ m and less than 0.5% of particles with a particle size greater than 2 x 10³ m. A process according to claim 1 wherein the composition obtained is cooled to a temperature of 4°C in a period less than or equal to 10 hours and then frozen at a temperature below -18°C, preferably from -18°C to -40°C. Composition which can be obtained by the process according to any one of claims 1 to 8. Use of the composition according to claim 9 for animal feed, preferably for aquaculture or pet food.