Enzymatic hydrolysis of animal material

Abstract

The present disclosure relates to rendering of animal material to usable products. Particularly, the disclosure relates to treatment of animal material by wet rendering including enzymatic hydrolysis. Herein, methods and arrangements for treating animal material are disclosed to yield products where distribution of soluble protein, insoluble protein and minerals is controlled.

Description

[0001] ENZYMATIC HYDROLYSIS OF ANIMAL MATERIAL

[0002] FIELD OF THE DISCLOSURE

[0003] The present disclosure relates to rendering of animal material to usable products. Particularly, the disclosure relates to treatment of animal material by wet rendering including enzymatic hydrolysis. Herein, methods and arrangements for treating animal material are disclosed to yield products where distribution of soluble protein, insoluble protein and minerals is controlled.

[0004] BACKGROUND OF THE DISCLOSURE

[0005] Rendering is a process that converts animal by-products, i.e. parts of animals which are not used as food, such as tissues, blood, bones, feathers, internal organs, heads, and even whole carcasses, into stable, usable materials. Dry and wet rendering are conventional methods used in the industry. Dry rendering involves heating of the size- reduced animal by-product while allowing moisture to evaporate. Melted fat is drained off and the protein-rich solids are dried and ground to a so-called meat-and-bone meal.

[0006] Wet rendering is a process which separates fat from the solids while maintaining moisture in the material. In wet rendering, the size-reduced and pre-heated animal by-product is subjected to solid-liquid separation by e.g. pressing and decanting to obtain a solid fraction containing solid protein and bone, and a liquid fraction containing water, fat, and soluble protein. Typically, fat is separated from the water fraction which is then concentrated and combined with the solids. Conventional wet rendering thus yields a fat product and a solid protein product that includes bone and has a high ash content. Some soluble proteins are formed, but protein hydrolysis in wet rendering is incidental and typically very limited.

[0007] More recently, rendering methods involving enzymatic treatment for the hydrolysis of proteins have been adopted in the field. Enzymatic rendering is a multi-step process that includes enzymatic degradation of the animal by-product raw material in wet conditions. Solids, liquid and fat are separated in the process as separate fractions, and thus enzymatic rendering yields in addition to a solid, high-ash protein product a liquid soluble protein fraction which contains water and enzyme-hydrolysed protein. The soluble protein product is versatile and can be utilized in various applications due to its high nutritional value, digestibility, and functional properties.

[0008] In conventional enzymatic rendering, all of the raw material is subjected to enzymatic hydrolysis, which leads to a need for high volume equipment and a requirement for large amounts of water, enzyme, and energy. Another limitation with conventional enzymatic rendering is that soluble proteins are recovered in one step only, and since solubility of proteins limits the amount of protein in the aqueous phase, the yield of soluble protein remains low. A further problem with conventional enzymatic rendering is that fat may interfere with the efficiency of enzyme digestion. Thus, there is an ongoing need for developing more efficient and sustainable methods for enzymatic rendering.

[0009] BRIEF DESCRIPTION OF THE DISCLOSURE

[0010] An object of the present disclosure is to provide a method and an arrangement for treating animal material so as to overcome the above problems.

[0011] The object of the disclosure is achieved by a method and an arrangement which are characterized by what is stated in the independent claims. Some embodiments of the disclosure are disclosed in the dependent claims.

[0012] In an aspect, the disclosure relates to a method for treating animal material, comprising a) heating the animal material, b) solid-liquid separating the heated animal material into a first solid fraction and a first liquid fraction, c) contacting the first solid fraction with at least one protein hydrolysing enzyme to provide an enzyme-treated solid fraction, and d) solid-liquid separating the enzyme-treated solid fraction into a second solid fraction and a second liquid fraction.

[0013] In a further aspect, the disclosure relates to an arrangement for treating animal material, comprising: a) a first vessel and a second vessel, wherein the first vessel is connected to the second vessel with a material transport connection, wherein the first vessel is configured for heating the animal material, b) first separation means for solid-liquid separating the heated animal material into a first solid fraction and a first liquid fraction so that the first solid fraction is transported through the material transport connection to the second vessel, c) the second vessel is configured to contact the first solid fraction with at least one protein hydrolysing enzyme to provide an enzyme-treated solid fraction, and d) second separation means for solid-liquid separating the enzyme-treated solid fraction into a second solid fraction and a second liquid fraction.

[0014] The disclosure is based on the idea of performing the enzymatic hydrolysis only to the treated solid fraction of the material where most of the liquid components have been removed, and thus being able to produce water-soluble proteins in two separate process steps.

[0015] BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In the following the disclosure will be described in greater detail with reference to the accompanying drawing, in which Figure 1 shows an exemplary method of the present disclosure.

[0017] DETAILED DESCRIPTION OF THE DISCLOSURE

[0018] Herein, a method for treating an animal material refers to a rendering method, such as wet rendering method or a dry rendering method, and particularly to an enzymatic rendering method. Rendering is the process of converting animal material such as animal byproducts, including animal carcasses, to a useful treated protein material. It involves exposing animal material to high temperatures using e.g. pressurized steam. This leads to coagulation of protein which reduces the available amount of soluble protein. Wet rendering is a multi-step process that can be adapted depending on the material to be treated. Such adaptations include introduction of an enzymatic treatment to enhance hydrolysis of protein into soluble protein. Enzymatic hydrolysis thus acts to release some of the coagulated or otherwise poorly available protein to soluble protein, which can find many uses in animal feeds and pet foods, as culture media in biotechnology and as fertilizers. However, there are disadvantages in conventional enzymatic rendering that include a requirement for high processing volume, and high amounts of reagents, water and energy.

[0019] As used herein, the terms “soluble protein”, “water-soluble protein” and the like refer to protein that can dissolve in aqueous solutions, typically water or physiological fluids. Soluble protein comprises whole proteins as well as peptides and amino acids. Soluble protein can be present in native or (partly) denatured form.

[0020] As used herein, the terms “solid protein" and "insoluble protein” and the like refer to protein that does not dissolve in water or aqueous solutions. These proteins are present as aggregates or form precipitates instead of remaining dispersed in solution. Solid protein is present in animal material that does not dissolve into an aqueous solution. Insoluble proteins are often structural or storage proteins such as collagen in connective tissues and keratin in hair, nails, and feathers. Protein hydrolysing enzymes may turn insoluble protein into soluble protein by degrading the solid protein aggregates. The degradation into soluble protein may be complete or partial.

[0021] As used herein, the terms “animal material”, “material of animal origin” and the like refer to material derived from animals. Animal material may comprise whole carcasses, any part of carcasses or by-products of animals or seafood including poultry (chicken, turkey, or duck, goose), fish, shellfish, beef, pork, cattle, goat, camel, and sheep. In particular, the by-products can be derived from meat and connecting tissues, trimmings, bones, blood, feathers, hair, digestive tract, internal organs, necks, heads. The animal material may be any combination of the above listed materials. Particularly, the animal material may be a poultry by-product or a combination of different poultry by-products. Alternatively, the animal material may comprise by-product material deriving from different animal species. Animal material is rich in animal protein. Typically, animal material also contains one or more components selected from fat and / or other biological macromolecules such as carbohydrates and nucleic acids, and moisture i.e. water.

[0022] As used herein, the term “or” has the meaning of both “and”’ and “or” (i.e. “and / or”). Furthermore, the meaning of a singular noun includes that of a plural noun and thus a singular term, unless otherwise specified, may also carry the meaning of its plural form. In other words, the term “a” or “an” may mean one or more.

[0023] As used herein, the term “comprising” includes the broader meanings of ’’including”, ’’containing”, and ’’comprehending”, as well as the narrower expressions “consisting of’ and “consisting only of’.

[0024] The disclosure relates to a new method for treating animal material. The method comprises: a) heating the animal material, b) solid-liquid separating the heated animal material into a first solid fraction and a first liquid fraction, c) contacting the first solid fraction with at least one protein hydrolysing enzyme to provide an enzyme-treated solid fraction, and d) solid-liquid separating the enzyme-treated solid fraction into a second solid fraction and a second liquid fraction.

[0025] Additionally, in a), water is optionally not removed from the animal material prior to, during or subsequent to heating.

[0026] Solid-liquid separating the heated animal material into the first solid fraction and the first liquid fraction allows for separating the at least partly insoluble protein material contained in the solid fraction from soluble proteins contained in the liquid fraction. Also, at least a part of fat contained in the animal material is melted and released during the pre-heating a), so it is removed with the first liquid fraction from the first solid fraction. The first solid fraction thus comprises a reduced content of fat, residual moisture, and it is enriched in insoluble protein and ash. The first liquid fraction includes fat, small particles with high ash content, water and water-soluble proteins. In some cases, solid-liquid separation may produce a separate first fat fraction, or the fat may be separated during subsequent steps of the process.

[0027] The first solid fraction may comprise a fat content in dry matter of up to 15% (w / w), preferably in the range of 0.1% to 12%, more preferably 3% to 12%, most preferably 2% to 10%. The fat content may depend one or more of the following: the type of the animal material (animal species, part of carcass etc.), the temperature used for pre-heating, the size distribution of the animal material, the efficiency of fat separation, and fat and / or protein content of the animal material.

[0028] The first solid fraction is contacted with at least one protein hydrolysing enzyme to provide an enzyme-treated solid fraction. As used herein, the terms “protein hydrolysing enzyme”, “protein degrading enzyme” and the like refer to a proteolytic enzyme which is added to the first solid fraction. The contacting results in production of a protein hydrolysate. The “at least one protein hydrolysing enzyme” may comprise one type of proteolytic enzyme or be a mixture of different types of enzymes with differing proteolytic activities. The enzyme or enzyme mixture may be in crude form or in pure form or a mixture of crude and purified enzyme(s). The enzyme may be a protease such as a serine protease, a cysteine protease, a threonine protease, an aspartic protease, a glutamic protease, a metalloprotease, a keratinase or an asparagine peptide lyase or any mixture thereof.

[0029] The duration of enzymatic hydrolysis in c) is at least 15 minutes. Additionally or alternatively, the duration of enzymatic hydrolysis can be from about 15 minutes (min) to 5 hours (h), from about 15 min to about 4 h, 3 h, 2 h or 1 h or from about 15 min to about 45 min. A skilled person can experimentally determine the optimal reaction time for the enzyme(s) used and to carry out the reaction for a desired duration.

[0030] The temperature used for enzymatic hydrolysis in c) can be from about 40°C to about 85°C, from about 50°C to about 80°C or from about 60°C to about 70°C. Alternatively, temperature used for enzymatic hydrolysis in step (c) may be less than 90°C. Generally, a skilled person may experimentally determine the optimal working range of the enzyme used and to carry out the reaction at a desired temperature.

[0031] The enzyme may be inactivated after the enzyme treatment by heating the enzyme-treated solid fraction to a temperature of 90°C or above.

[0032] The method of the disclosure may comprise adding an aqueous solution to the first solid fraction in c). The volume of the aqueous solution is preferably smaller than volume of the first liquid fraction in b). For example, the volume of the aqueous solution may be 20% to 60% of the volume of the first liquid fraction. The aqueous solution may be water, an aqueous buffer solution, a water-solvent mixture or a combination thereof. The aqueous solution is added in an amount which makes the mixture of the first solid fraction and aqueous solution stirrable and / or pumpable.

[0033] The pH of the first solid fraction and optionally aqueous solution may be adjusted to a value between 5.5 and 9.5 to provide favourable conditions for the enzymatic reaction. A skilled person may experimentally determine the optimal working range of the enzyme used and to add buffer, acid or base to adjust the reaction solution to a desired pH value.

[0034] An advantage of the method of the disclosure is that due to treating only the solids separated in b) with the enzyme in c), the enzymatic reaction is carried out in a smaller volume compared to the conventional process where all of the pre-heated animal material is hydrolysed enzymatically. The new process therefore requires smaller-size instrumentation, smaller amounts of reagents for adjusting conditions of the enzymatic reaction, and also less water and energy. The new process also produces water-soluble proteins in two separate ways - soluble protein is present both in the first liquid fraction and the second liquid fraction rather than only in one fraction as in the conventional process, thus increasing the yield of soluble proteins. Also, because enzymatic treatment is performed in a smaller volume and to a solid animal material where fat content is already reduced form original fat content due to removing the first liquid fraction, the enzymatic action may occur in more optimal conditions without e.g. interference from fat. The new process thus yields more water-soluble proteins than traditional wet rendering or conventional enzymatic treatment.

[0035] Typically, the animal material may be selected from food-producing animal by-products comprising one or more selected from tissues, bones, carcasses, blood, feathers, internal organs, necks, and heads.

[0036] The animal material can be used in the method in its original size and shape i.e. without preforming size reduction or comminution prior to heating.

[0037] Additionally or alternatively, the animal material can be reduced in size by milling or crushing to a desired maximum particle size prior to heating. For example, before heating in a), the animal material may be comminuted to a particle size of up to about 50 millimetres, or up to about 40 mm, or up to about 30 mm, or up to about 20 mm, or up to about 10 mm, or up to about 5 mm. Comminuting may be performed for example by grinding, mixing, milling or crushing. Comminuting an animal material can be performed by any suitable method known in the art. For example, bones or internal organs can be minced or crushed, and feathers can be cut, crushed, mixed, or milled. Additionally or alternatively, the animal material may be heated in a) to a temperature in the range of 50°C to 100°C. Heating the animal material is intended to melt and release at least a part of the fat contained in the animal material, to denature proteins and to reduce the microbial load in the animal material. This also reduces the amount of pathogens such as bacteria and viruses in the animal material and extends the shelf life of products derived from the animal material in the process.

[0038] Additionally or alternatively, the heating temperature applied in a) is sufficient to melt at least a part of the fat in the animal material. This also promotes removal of fat with the first liquid fraction in b).

[0039] Additionally or alternatively, the heating temperature in a) can be up to 100°C, or up to 99°C, or from about 40°C to about 100°C, or from about 50°C to about 100°C, or from about 60°C to about 100°C, or from about 70°C to about 100°C, or from about 70°C to about 99°C, from about 85°C to about 98°C or from about 94°C to about 98°C. Alternatively, the heating temperature can be any range between the temperatures 40°C, 41 °C, 42°C, 43°C, 44°C, 45°C, 46°C, 47°C, 48°C, 49°C, 50°C, 51 °C, 52°C, 53°C, 54°C,

[0040] 55°C, 56°C, 57°C, 58°C, 59°C, 60°C, 61 °C, 62°C, 63°C, 64°C, 65°C, 66°C, 67°C, 68°C,

[0041] 69°C, 70°C, 71 °C, 72°C, 73°C, 74°C, 75°C, 76°C, 77°C, 78°C, 79°C, 80°C, 81 °C, 82°C,

[0042] 83°C, 84°C, 85°C, 86°C, 87°C, 88°C, 89°C, 90°C, 91 °C, 92°C, 93°C, 94°C, 95°C, 96°C,

[0043] 97°C, 98°C, 99°C, and 100°C. As will be readily appreciated, the temperature to melt the fat can also be adjusted depending on the pressure applied.

[0044] Additionally or alternatively, the time of heating in a) can be at least 3 minutes, or in the range of about 3 minutes (min) to about 5 hours (h), or about 5 min to about 4 h, or about 10 min to about 3 h, or about 10 min to about 2 h, or about 10 min to about 1 h or about 5 min to about 45 min.

[0045] In d), the enzyme-treated solid fraction is solid-liquid separated into a second solid fraction and a second liquid fraction This can allow for separation of protein material contained in the solid fraction from the water-soluble proteins and optionally also residual fat present in the liquid fraction. Some animal materials such as blood and feathers contain fat in smaller amounts than e.g. bone and internal organs, so little or essentially no fat may be present in the liquid fraction derived from low-fat animal materials.

[0046] It can be envisaged that the contacting with the at least one protein hydrolysing enzyme either increases (soluble) protein content in the second liquid fraction or decreases (soluble) protein content in the second solid fraction or both when compared to a method of treating animal material which involves no contacting with at least one protein hydrolysing enzyme.

[0047] Additionally or alternatively, the second solid fraction may comprise a content (weight / weight, w / w) of ash in dry matter that is higher than the content (w / w) of ash in dry matter in the third solid fraction. This is because solids of the animal material, including the majority of the mineral-rich material such as bone, are directed predominantly to the second solid fraction. The second solid fraction typically includes protein, ash and residual moisture of the enzyme-treated material. The second liquid fraction, wherefrom the third solid fraction is obtained by solid-liquid separation, contains small amounts of solids mainly as small protein-rich particles, and relatively little minerals. The second liquid fraction typically includes water and water-soluble proteins and optionally residual fat present in the enzyme-treated animal material.

[0048] Additionally, the method of the present disclosure may comprise e) separating the second liquid fraction into a third solid fraction and a third liquid fraction. At the same time, it is also possible to separate a third fat fraction, particularly when a decanter is used for solid-liquid separation. The third solid fraction comprises residual material from the second liquid fraction including protein, ash and some residual moisture. The third liquid fraction typically includes water and water-soluble proteins.

[0049] Often, fat is present in the animal material, and fat of the enzyme-treated animal material may be separated in e) as a third fat fraction or fat may be included in the third liquid fraction. Heating the second liquid fraction may promote separation of fat due to melting of fat. Thus, optionally, the second liquid fraction may be heated to a temperature in the range of 50°C to 100°C before separating.

[0050] Additionally or alternatively, the heating temperature in e) can be up to 100°C, or up to 99°C, or from about 40°C to about 100°C, or from about 50°C to about 100°C, or from about 60°C to about 100°C, or from about 70°C to about 100°C, or from about 70°C to about 99°C, from about 85°C to about 98°C or from about 94°C to about 98°C. Alternatively, the heating temperature can be any range between the temperatures 40°C, 41 °C, 42°C, 43°C, 44°C, 45°C, 46°C, 47°C, 48°C, 49°C, 50°C, 51 °C, 52°C, 53°C, 54°C,

[0051] 55°C, 56°C, 57°C, 58°C, 59°C, 60°C, 61 °C, 62°C, 63°C, 64°C, 65°C, 66°C, 67°C, 68°C,

[0052] 69°C, 70°C, 71 °C, 72°C, 73°C, 74°C, 75°C, 76°C, 77°C, 78°C, 79°C, 80°C, 81 °C, 82°C,

[0053] 83°C, 84°C, 85°C, 86°C, 87°C, 88°C, 89°C, 90°C, 91 °C, 92°C, 93°C, 94°C, 95°C, 96°C,

[0054] 97°C, 98°C, 99°C, and 100°C. As will be readily appreciated, the temperature to melt the fat can also be adjusted depending on the pressure applied. Additionally or alternatively, the second solid fraction may comprise an ash to protein weight ratio in dry matter of 2:1 to 1 :2. Moreover, the second solid fraction may additionally or alternatively comprise an ash content in dry matter ranging from 30% to 60% (w / w).

[0055] Additionally or alternatively, the third solid fraction may comprise an ash to protein weight ratio in dry matter of 1 :6 to 1 :15. Moreover, the third solid fraction may additionally or alternatively comprise an ash content in dry matter ranging from 1% to 15% (w / w).

[0056] Additionally, the method of the present disclosure may further comprise f) separating the first liquid fraction into a fourth solid fraction and a fourth liquid fraction. Typically, the fourth solid fraction contains the remaining solids and the fourth liquid fraction contains water, soluble proteins and optionally fat. It is also possible to separate a fourth fat fraction. That is, the fourth liquid fraction can be further treated to separate fat, or, alternatively, the device used for solid-liquid separation of the first liquid fraction, such as a decanter centrifuge, may directly produce a fourth fat fraction in addition to the fourth solid fraction and the fourth liquid fraction.

[0057] The fat fraction(s) separated in the method of the present disclosure can be sold or used as such or further purified for example using a separator. Additionally or alternatively, nonfat constituents obtained from fat purification may be returned back for example to separation b) or mixed with the first solid fraction. Solid non-fat components from fat purification may be recirculated back for example to the enzyme treatment in c) or mixed with the second solid fraction or both.

[0058] Additionally or alternatively, the second solid fraction may comprise a content (w / w) of ash in dry matter that is higher than the content (w / w) of ash in dry matter in the fourth solid fraction. This is because solids of the animal material, including the majority of the mineralrich material such as bone, are directed predominantly to the second solid fraction. The first liquid fraction, wherefrom the fourth solid fraction is obtained by solid-liquid separation, contains solids mainly as small protein-rich particles, and relatively little minerals.

[0059] Additionally or alternatively, the fourth solid fraction may comprise an ash to protein weight ratio in dry matter of 1 :6 to 1 :15. Moreover, the fourth solid fraction may additionally or alternatively comprise an ash content in dry matter ranging from 1% to 15% (w / w).

[0060] Additionally, the method of the disclosure may further comprise one or more of g) to j): g) drying the second solid fraction to provide a dry first solid product comprising ash and protein; h) combining the third solid fraction and fourth solid fraction to provide a second solid product comprising ash and protein, and optionally drying to provide a dry second solid product comprising ash and protein; i) drying the third liquid fraction to provide a dry third solid protein product comprising ash and protein; j) drying the fourth liquid fraction to provide a dry fourth solid protein product comprising ash and protein; or k) combining the third liquid fraction and fourth liquid fraction to provide a fifth liquid fraction comprising ash and protein, and optionally drying to provide a dry fifth solid product comprising ash and protein.

[0061] The method of the present disclosure thus may comprise steps a), b), c), d), and one or more of steps e), f), g), h), i), j) and k). As readily understood by one of ordinary skill in the art, all steps are not necessarily performed in alphabetical order but e.g. step f) may be performed without performing step e) as these steps involve different solid and / or liquid fractions. Particularly, the steps h) to k) are dependent on which steps preceded them: h) requires that step e) is performed, j) requires that step f) is performed and i) and k) require that steps e) and f) are performed.

[0062] The dependent claims present exemplary methods of the present disclosure. Additionally or alternatively, exemplary methods of the present disclosure include those where the following steps are performed:

[0063] - a), b), c), d), optionally g)

[0064] - a), b), c), d), e), optionally g) and / or h)

[0065] - a), b), c), d), f), optionally g) and / or j)

[0066] - a), b), c), d), e), f), optionally one or more of g), h), i), j), k).

[0067] Additionally or alternatively, the first solid product may comprise a content (w / w) of ash in dry matter that is higher than the content (w / w) of ash in dry matter in any one, any two or all of the following: the second solid product, the third solid product and the fourth solid product.

[0068] In g), the second solid fraction is dried. That is, in g) most of the residual moisture of the second solid fraction is evaporated in order to obtain a dry first solid product. The second solid product comprises ash and protein. Additionally or alternatively, g) may be performed under conditions of temperature and pressure that are sufficient to reduce the moisture content from that of the second solid fraction to about 10% by weight or less, preferably about 6% by weight or less, relative to the total weight of the dry first solid product.

[0069] Additionally or alternatively, in g) the dry first solid product comprises a moisture content of about 1 -10% by weight, or more preferably 1-8% by weight relative to the total weight of the dry second solid fraction.

[0070] Additionally or alternatively, drying in g) can be performed at a high temperature. In particular, a suitable temperature to perform the drying in g) can include a temperature ranging from about 65°C to about 180°C under atmospheric or reduced pressure. The temperature can be adapted depending on the pressure applied. Additionally or alternatively, drying in g) may be performed by using a paddle dryer, a disc dryer, a flash dryer, mill dryer, or a rotary hot air dryer.

[0071] In h), the third solid fraction and fourth solid fraction are combined to provide a second solid product. The second solid product comprises ash and protein. The second solid product may optionally be dried to provide a dry second solid product comprising ash and protein. Alternatively, the third solid fraction and fourth solid fraction may not be combined but are processed further separately by e.g. drying similarly as in g) described above.

[0072] During the optional drying in h) the residual moisture of the second solid product is evaporated to obtain a dry second solid product. Drying in h) can be performed in sufficient conditions of temperature and pressure to dry the second solid product to a moisture content of about 10% by weight or less, preferably about 6% by weight or less, relative to the total weight of the dry second solid product.

[0073] Additionally or alternatively, in h) the dry second solid product comprises a moisture content of about 1 -10% by weight, or more preferably 1 -8% by weight relative to the total weight of the dry second solid product.

[0074] Additionally or alternatively, drying in h) can be performed at high temperature. In particular, a suitable temperature to perform the drying in h) can include a temperature ranging from about 65°C to about 180°C under atmospheric or reduced pressure. The temperature can be adapted depending on the pressure applied. Additionally or alternatively, drying in h) may be performed by a paddle dryer, a disc dryer, a flash dryer, mill dryer, or a rotary hot air dryer.

[0075] In i) the third liquid fraction is dried to provide a dry third solid protein product. The third solid protein product comprises ash and protein. Additionally or alternatively, the third liquid fraction may be concentrated, for example by evaporation, before drying in i). The third liquid fraction may be concentrated to reach a moisture content of up to about 70% by weight, up to about 60% by weight, up to about 50% by weight, or up to about 40% by weight relative to the total weight of the third liquid fraction.

[0076] Thus, i) comprises drying the third liquid fraction or its concentrate. In i) the moisture of the third liquid fraction is evaporated to obtain a dry third solid protein product that is a product comprising a significant amount of water-soluble protein hydrolysate. Additionally or alternatively, i) can be performed under conditions of temperature and pressure that are sufficient to reduce the moisture content from that of the third liquid fraction to about 10% by weight or less, preferably about 6% by weight or less, relative to the total weight of the dry third solid protein product.

[0077] Additionally or alternatively, in i) the dry third solid protein product comprises a moisture content of about 1 -10 %, or preferably 2-6% by weight relative to the total weight of the dry third solid protein product.

[0078] Additionally or alternatively, the drying in i) can be performed at high temperature. In particular, a suitable temperature to perform the drying in i) can include a temperature ranging from about 65°C to about 180°C under atmospheric or reduced pressure. The temperature can be adapted depending on the pressure applied. Additionally or alternatively, drying in i) may be performed by a spray dryer, contact drum dryer, beltdryer, or agitated thin-film dryer.

[0079] In j), the fourth liquid fraction is dried to provide a dry fourth solid protein product comprising ash and protein.

[0080] Additionally or alternatively, the fourth liquid fraction can be concentrated, for example by evaporation, before drying in j). The fourth liquid fraction may be concentrated to reach a moisture content of about 70% by weight, up to about 60% by weight, up to about 50% by weight, or up to about 40% by weight relative to the total weight of the fourth liquid fraction.

[0081] Thus, j) comprises drying the fourth liquid fraction or its concentrate. In j) the moisture of the fourth liquid fraction is evaporated to obtain a dry fourth solid protein product that is a product comprising mainly water-soluble protein.

[0082] Additionally or alternatively, j) can be performed under conditions of temperature and pressure that are sufficient to reduce the moisture content from that of the fourth liquid fraction to about 10% by weight or less, preferably about 6% by weight or less, relative to the total weight of the dry fourth solid protein product. Additionally or alternatively, in j) dry fourth solid protein product comprises a moisture content of about 1 -10 %, or preferably 2-6% by weight relative to the total weight of the dry fourth solid protein product.

[0083] Additionally or alternatively, the drying in j) can be performed at high temperature. Particularly, a suitable temperature to perform the drying of in (j) can include a temperature ranging from about 65°C to about 180°C under atmospheric or reduced pressure. The temperature can be adapted depending on the pressure applied.

[0084] Additionally or alternatively, drying in i) may be performed by a spray dryer, contact drum dryer, belt-dryer, or agitated thin-film dryer.

[0085] In k), the third liquid fraction and fourth liquid fraction are combined to provide a fifth liquid product. The fifth liquid product comprises ash and protein. The fifth liquid product may optionally be dried to provide a dry fifth solid product comprising ash and protein. Alternatively or additionally, the third liquid fraction and fourth liquid fraction may not be combined but are processed separately as in i) and j) described above. In other words, a part of the third liquid fraction and of the fourth liquid fraction may be combined as a mixture and then optionally dried, and a part of each liquid fraction may be dried separately.

[0086] Additionally or alternatively, the third liquid fraction and / or the fourth liquid fraction may be concentrated before drying in k), for example by evaporation, either before mixing or after mixing the fractions. The third liquid fraction and / or the fourth liquid fraction or their mixture may be concentrated to reach a moisture content of up to about 70% by weight, up to about 60% by weight, up to about 50% by weight, or up to about 40% by weight relative to the total weight of the third liquid fraction or the fourth liquid fraction or their mixture.

[0087] Thus, k) comprises drying the mixture of the combined third and fourth liquid fractions, optionally as a concentrate of one or both liquid fractions. In k), the moisture of the mixture of the third and fourth liquid fractions is evaporated to obtain a dry fifth solid protein product that is a product comprising a significant amount of water-soluble protein hydrolysate.

[0088] Additionally or alternatively, k) can be performed under conditions of temperature and pressure sufficient to reduce the moisture content from that of the mixture to about 10% by weight or less, preferably about 6% by weight or less, relative to the total weight of the dry fifth solid protein product.

[0089] Additionally or alternatively, in k) the dry fifth solid protein product comprises a moisture content of about 1 -10 %, or preferably 2-6% by weight relative to the total weight of the dry fifth solid protein product. Additionally or alternatively, the drying in k) can be performed at high temperature. In particular, a suitable temperature to perform the drying in k) can include a temperature ranging from about 65°C to about 180°C under atmospheric or reduced pressure. The temperature can be adapted depending on the pressure applied.

[0090] Additionally or alternatively, drying in k) may be performed by a spray dryer, contact drum dryer, belt-dryer, or agitated thin-film dryer.

[0091] In an aspect, the disclosure relates to an arrangement for treating animal material. The arrangement comprises: a) a first vessel and a second vessel, wherein the first vessel is connected to the second vessel with a material transport connection, wherein the first vessel is configured for heating the animal material, optionally to a temperature in the range of 70°C to 100°C; b) first separation means for solid-liquid separating the heated animal material into a first solid fraction and a first liquid fraction so that the first solid fraction is transported through the material transport connection to the second vessel; c) the second vessel is configured to contact the first solid fraction with at least one protein hydrolysing enzyme to provide an enzyme-treated solid fraction; d) second separation means for solid-liquid separating the enzyme-treated solid fraction into a second solid fraction and a second liquid fraction.

[0092] Both the first vessel and the second vessel may be closed or open vessels. In the first vessel, the animal material is heated. Preferably, the heating temperature in the first vessel is sufficient to melt at least a part of the fat in the animal material. Thus, the animal material may be heated in the first vessel to a temperature in the range of about 50°C to about 100°C.

[0093] Additionally or alternatively, the heating temperature in the first vessel can be up to 100°C, or up to 99°C, or from about 40°C to about 100°C, or from about 50°C to about 100°C, or from about 60°C to about 100°C, or from about 70°C to about 100°C, or from about 70°C to about 99°C, from about 85°C to about 98°C or from about 94°C to about 98°C. Alternatively, the heating temperature can be any range between the temperatures 40°C, 41 °C, 42°C, 43°C, 44°C, 45°C, 46°C, 47°C, 48°C, 49°C, 50°C, 51 °C, 52°C, 53°C, 54°C,

[0094] 55°C, 56°C, 57°C, 58°C, 59°C, 60°C, 61 °C, 62°C, 63°C, 64°C, 65°C, 66°C, 67°C, 68°C,

[0095] 69°C, 70°C, 71 °C, 72°C, 73°C, 74°C, 75°C, 76°C, 77°C, 78°C, 79°C, 80°C, 81 °C, 82°C,

[0096] 83°C, 84°C, 85°C, 86°C, 87°C, 88°C, 89°C, 90°C, 91 °C, 92°C, 93°C, 94°C, 95°C, 96°C, 97°C, 98°C, 99°C, and 100°C. As will be readily appreciated, the temperature to melt the fat can also be adjusted depending on the pressure applied.

[0097] Additionally or alternatively, the time of heating in the first vessel can be at least 3 minutes, or in the range of about 3 minutes (min) to about 5 hours (h), or about 5 min to about 4 h, or about 10 min to about 3 h, or about 10 min to about 2 h, or about 10 min to about 1 h or about 5 min to about 45 min.

[0098] Additionally or alternatively, the first solid fraction and the first liquid fraction can be solidliquid separated in the first separation means by pressing the animal material so a liquid containing water, soluble protein and optionally fat is separated from solids. The content of fat in the first liquid fraction depends on for example the type of animal material used - some materials such as feathers contain little or no fat. Optionally, a separate first fat fraction may also be separated by the first separation means in addition to the first solid fraction and the first liquid fraction. The first separation means may comprise a screw press, a double-screw press, a decanter centrifuge, a three-phase decanter centrifuge, a sieve, or any other suitable equipment for separating liquid from solids of an animal material. Preferably, the first separation means is a screw press, double-screw press, a decanter centrifuge, or a three-phase decanter centrifuge.

[0099] Additionally or alternatively, the temperature at separation in the first separation means can be equal or cooler than the temperature used in the first vessel.

[0100] In the second vessel is conducted an enzymatic hydrolysis of the solid-liquid separated animal material. There, the first solid fraction is contacted with at least one protein hydrolysing enzyme to provide an enzyme-treated solid fraction. The contacting results in production of a protein hydrolysate.

[0101] The duration of enzymatic hydrolysis in the second vessel is at least 15 minutes. Additionally or alternatively, the duration of enzymatic hydrolysis can be from about 15 minutes (min) to 5 hours (h), from about 15 min to about 4 h, 3 h, 2 h or 1 h or from about 15 min to about 45 min.

[0102] The temperature used for enzymatic hydrolysis in the second vessel can be from about 40°C to about 85°C, from about 50°C to about 80°C or from about 60°C to about 70°C. Alternatively, temperature used for enzymatic hydrolysis in step (c) may be less than 90°C. Thus, the second vessel may be configured for heating the first solid fraction before, during or subsequent to the contacting with at least one protein hydrolysing enzyme. Additionally, the enzyme may be inactivated after the enzyme treatment in the second vessel by heating the enzyme-treated solid fraction in the second vessel to a temperature of 90°C or above. Additionally or alternatively, the second vessel may comprise a means for adding an aqueous solution to the first solid fraction before or during enzyme hydrolysis in the second vessel. The volume of the aqueous solution is preferably smaller than volume of the first liquid fraction. For example, the volume of the aqueous solution may be 20% to 60% of the volume of the first liquid fraction. The aqueous solution may be water, an aqueous buffer solution, a water-solvent mixture or a combination thereof. The aqueous solution is added in an amount which makes the mixture of the first solid fraction and aqueous solution stirrable and / or pumpable. The means for adding an aqueous solution may comprise an inlet and optionally a conduit for adding the aqueous solution to the second vessel.

[0103] Additionally or alternatively, the second vessel may comprise a means for adjusting the pH of the first solid fraction and optionally aqueous solution to a value between 5.5 and 9.5 to provide favourable conditions for the enzymatic reaction. The means for adjusting the pH may comprise an inlet and optionally a conduit for adding acid or base to the second vessel. The means may further comprise a pH meter for determining pH of the contents of the second vessel.

[0104] Additionally, the arrangement of the disclosure may further comprise: e) third separation means for solid-liquid separating the second liquid fraction into a third solid fraction and a third liquid fraction.

[0105] The second solid fraction and a second liquid fraction can be separated by pressing or sieving the enzyme-treated animal material to separate from the solid fraction the liquid fraction that optionally also contains fat. Optionally, a third fat fraction may also be separated by the third solid-liquid separation means. In other words, a third solid fraction and a third liquid fraction and a third fat fraction are separated. Additionally or alternatively, the third separation means is a screw press, a double-screw press, a decanter centrifuge, a three-phase decanter centrifuge, or a sieve.

[0106] Additionally or alternatively, the arrangement may further comprise a heating means for heating the second liquid fraction to a temperature in the range of 50°C to 100°C. The heating means is arranged to heat the second liquid fraction before the solid-liquid separation by the third separation means. Additionally or alternatively, the heating temperature can be up to 100°C, or up to 99°C, or from about 40°C to about 100°C, or from about 50°C to about 100°C, or from about 60°C to about 100°C, or from about 70°C to about 100°C, or from about 70°C to about 99°C, from about 85°C to about 98°C or from about 94°C to about 98°C. Alternatively, the heating temperature can be any range between the temperatures 40°C, 41 °C, 42°C, 43°C, 44°C, 45°C, 46°C, 47°C, 48°C, 49°C, 50°C, 51 °C, 52°C, 53°C, 54°C, 55°C, 56°C, 57°C, 58°C, 59°C, 60°C, 61 °C, 62°C, 63°C, 64°C, 65°C, 66°C, 67°C, 68°C, 69°C, 70°C, 71 °C, 72°C, 73°C, 74°C, 75°C, 76°C, 77°C, 78°C, 79°C, 80°C, 81 °C, 82°C, 83°C, 84°C, 85°C, 86°C, 87°C, 88°C, 89°C, 90°C, 91 °C, 92°C, 93°C, 94°C, 95°C, 96°C, 97°C, 98°C, 99°C, and 100°C. As will be readily appreciated, the temperature to melt the fat can also be adjusted depending on the pressure applied.

[0107] Additionally, the arrangement of the disclosure may further comprise: f) fourth separation means for separating the first liquid fraction into a fourth solid fraction and a fourth liquid fraction.

[0108] Optionally, a fourth fat fraction may also be separated by the fourth separation means. The fourth separation means may be a screw press, a double-screw press, a decanter centrifuge, a three-phase decanter centrifuge, or a sieve. Preferably, the fourth separation means is a decanter centrifuge or a three-phase decanter centrifuge.

[0109] Additionally, the arrangement of the disclosure may further comprise one or more of g)-j): g) first drying means for drying the second solid fraction to provide a dry first solid product comprising ash and protein; h) second drying means for drying a combined third solid fraction and fourth solid fraction to provide a dry second solid product comprising ash and protein; i) third drying means for drying the third liquid fraction to provide a dry third solid protein product comprising ash and protein; j) fourth drying means for drying the fourth liquid fraction to provide a dry fourth solid protein product comprising ash and protein; or k) fifth drying means for drying a combined third liquid fraction and fourth liquid fraction to provide a dry fifth solid protein product comprising ash and protein.

[0110] The arrangement of the present disclosure thus may comprise a), b), c), d), and one or more of e), f), g), h), i), j) and k). As readily understood by one of ordinary skill in the art, all parts of the arrangement are not necessarily included in alphabetical order but e.g. f) may be included without including e) as e) and f) involve different solid and / or liquid fractions. Particularly, h) to k) are dependent on which parts preceded them: h) requires that e) is included, j) requires that f) is included and i) and k) require that e) and f) are included. The dependent claims present exemplary arrangements of the present disclosure. Additionally or alternatively, exemplary arrangements of the present disclosure include those where the following are included:

[0111] - a), b), c), d), optionally g)

[0112] - a), b), c), d), e), optionally g) and / or h)

[0113] - a), b), c), d), f), optionally g) and / or j)

[0114] - a), b), c), d), e), f), optionally one or more of g), h), i), j), k).

[0115] The first and the second drying means may be a disc dryer, paddle dryer, hot air dryer, or a flash dryer.

[0116] The third, fourth and fifth drying means may be a spray dryer, contact dryer, belt-dryer, or an agitated thin film dryer.

[0117] The combined third solid fraction and fourth solid fraction refers to a mixture of the third solid fraction and the fourth solid fraction. Similarly, the combined third liquid fraction and fourth liquid fraction refers to a mixture of the third liquid fraction and the fourth liquid fraction. For combining the solid fractions, the arrangement may comprise material transport connection(s) that connect the third separation means and the fourth separation means to the second drying means that is arranged to mix the fractions before, after or during drying. For combining the liquid fractions, the arrangement may comprise material transport connection(s) that connect the third separation means and the fourth separation means to the fifth drying means that is arranged to mix the fractions before, after or during drying.

[0118] Additionally or alternatively, the arrangement of the disclosure may comprise a means for comminuting the animal material. Preferably, the animal material is comminuted to a particle size of up to about 50 millimetres, or up to about 40 mm, or up to about 30 mm, or up to about 20 mm, or up to about 10 mm, or up to about 5 mm, before placing the animal material in the first vessel. The means for comminuting may be selected from a grinder, mixer, a mill or a crusher.

[0119] Any aspects and embodiments discussed herein in context of the method also apply to the arrangement in suitable parts as readily understood by the skilled person.

[0120] The arrangement may be configured to perform the method of the disclosure.

[0121] It will be obvious to a person skilled in the art that, as the technology advances, the inventive concept can be implemented in various ways. The method and arrangement of the present disclosure and their embodiments are not limited to the examples described herein but may vary within the scope of the claims.

[0122] EXAMPLES

[0123] Example 1

[0124] Preparation of pressed solids

[0125] Poultry by-product solid material used in enzymatic treatment of the new process was obtained by pre-heating poultry by-product raw material to 90°C and separating liquid material from solids by pressing with a screw press. In Figure 1 , the poultry by-product solid material corresponds to the first solid fraction, and the liquid material separated by pressing corresponds to the first liquid fraction. This way the amount of material treated in the subsequent enzymatic reaction (see below) was reduced by approximately 75 vol-% in comparison to the amount of the original poultry by-product raw material. This volume reduction which is not featured in conventional wet rendering processes is beneficial as smaller equipment, less water, less energy and reagents are required in the subsequent enzymatic treatment step. Properties of the poultry by-product solid material are presented in Table 1.

[0126] Table 1. Properties of poultry by-product solid material.

[0127] End products

[0128] The rendered poultry protein products are prepared from the first solid fraction and the first liquid fraction obtained as described above and according to the exemplary process outlined in Figure 1 . Composition of the obtained poultry protein end products is given in Table 2.

[0129] Conventional Solid Protein in Table 2. is a protein product that is obtained in a conventional wet rendering process and is used here as comparison to the new protein products obtained in the process of the disclosure. In conventional wet rendering, the size- reduced and pre-heated animal by-product is subjected to solid-liquid separation by e.g. pressing and decanting to obtain a solid fraction containing solid protein and bone, and a liquid fraction containing water, fat, and soluble protein. Typically, fat is removed from the water fraction which is then concentrated and may be combined with the solids. Conventional wet rendering thus yields a fat product, a solid protein product and possibly a soluble protein product. Thus, a conventional wet rendering process does not feature for example the steps of Figure 1 where the second solid fraction and third solid fraction are obtained separately. This results in only one solid protein end-product in the conventional process.

[0130] In conventional wet rendering, the water fraction separated from solids (which corresponds to the fourth liquid fraction in Figure 1 ), may be processed separately into a Conventional Soluble Protein product. After concentration of the water fraction in for example a vapor compression evaporator, the resulting concentrate can be dried into a Conventional Soluble Protein which is shown in Table 2.

[0131] As seen from Table 2, the process according to the disclosure provides a new product, Soluble Protein Hydrolysate, with higher protein and lower fat and ash content as compared to Conventional Soluble Protein product and in particular compared to Conventional Solid Protein. Soluble Protein Hydrolysate is produced from preheated, enzyme-treated solids that have preferably undergone two more solid-liquid separations to provide a liquid fraction (corresponds to third liquid fraction of Figure 1 ) with reduced content of solids. Thereafter, the liquid fraction may be concentrated and / or dried to provide the Soluble Protein Hydrolysate seen in Table 2. In some cases in the process according to the disclosure, the third and fourth liquid fractions may be combined and optionally dried into a soluble protein product comprising abundant hydrolysed protein. Also in this case, the total yield of soluble protein is higher than in the conventional process.

[0132] Another new product, Low Ash Solid Protein, is formed alongside the Soluble Protein Hydrolysate. Low Ash Solid Protein corresponds to the combined solid fractions three and four in Figure 1 . As can be seen in Table 2, the new Low Ash Solid Protein product is equal in protein content but has approximately two times lower ash content than the Conventional Solid Protein product.

[0133] Yet another new product, High Ash Solid Protein, is produced from the enzyme-treated solids fraction (corresponds to second solid fraction in Figure 1). Compared to Conventional Solid Protein, the new High Ash Solid Protein product has a reduced protein content and an increased ash content. In conclusion, the process according to the disclosure is efficient in directing protein to the Soluble Protein Hydrolysate fraction to give a high-quality (high protein, low ash) soluble protein hydrolysate product, while also producing a solid product with high protein and low ash content, and a solid protein product with a high content of minerals. Compared to the conventional process, the new process according to the disclosure provides a larger variety of products with potential for higher value and more specified uses.

[0134] Table 2. Compositions of rendered poultry protein products. Amounts of components are given as wt-% (weight / weight). Abbreviation: conv. = conventional; n.d. = not determined.

[0135] Example 2

[0136] Recovery of additional water-soluble protein hydrolysates by the new rendering method

[0137] Starting material was poultry by-product solid material obtained by pre-heating poultry byproduct raw material to 90°C and separating solids from liquid material by pressing with a screw press. The poultry by-product solid material corresponded to that of Example 1 and to the first solid fraction of Figure 1 .

[0138] 1 . A: 800g of poultry by-product solid material was mixed with 800 ml of water. The mixture was incubated at 65°C for 1 h under gentle stirring.

[0139] B: 800g of poultry by-product solid material was mixed with 800 ml of water and 1.6ml of protease enzyme (Tailorzyme Endocut, Denmark). The mixture was incubated at 65°C for 1 h under gentle stirring.

[0140] 2. After the incubation samples A and B were transferred to 400 ml centrifuge tubes and spinned for 15 min at 4700 rpm in a laboratory centrifuge (VWR Mega star 1 .6, Belgium). 3. The top layer in the centrifuge tubes containing liquid fat was discarded. The dry matter content of the liquid water phases A and B was measured with an infrared moisture analyzer (Sartorius MA 160, Germany) as triplicate (samples 1 , 2 and 3).

[0141] The results are given in Table 3. The liquid phase B can be considered to correspond to the third liquid fraction of Figure 1 . This is because centrifugation is a highly efficient solidliquid separation method that may equal the two solid-liquid separation steps presented in Figure 1 that produce the solids-reduced second liquid fraction and the solids- and fat- reduced third liquid fraction. As described above, fat was discarded as the top layer, and therefore samples A and B are fat-reduced liquid phases. In this Example, it is demonstrated that compared to the conventional process (A) without enzymatic hydrolysis, the new method of the disclosure (B) that includes an enzyme treatment provides a liquid fraction with a higher dry matter content. The starting material of both A and B methods contained a similar amount of ash and protein, but the enzyme treatment in method B facilitated recovering an increased amount of soluble protein in B compared to method A. In method A, the starting material is only washed with water, and a much smaller amount of soluble protein was present in the liquid phase A. Thus, the new method is efficient in directing soluble protein into the liquid phase B, whereas the amount of ash present in liquid phases A and B remained essentially same (results not shown). -

[0142] Table 3. Dry matter content (%) in the liquid phase.

Claims

CLAIMS1 . A method for treating animal material, comprising: a) heating the animal material, optionally to a temperature in the range of 50°C to 100°C; b) solid-liquid separating the heated animal material into a first solid fraction and a first liquid fraction; c) contacting the first solid fraction with at least one protein hydrolysing enzyme to provide an enzyme-treated solid fraction; d) solid-liquid separating the enzyme-treated solid fraction into a second solid fraction and a second liquid fraction.

2. The method according to claim 1 , comprising: e) separating the second liquid fraction into a third solid fraction, a third liquid fraction, and optionally a fat fraction, wherein optionally the second solid fraction comprises a content (w / w) of ash in dry matter that is higher than the content (w / w) of ash in dry matter in the third solid fraction, and wherein optionally the second liquid fraction is heated to a temperature in the range of 50°C to 100°C before separating.

3. The method according to claim 1 or 2, comprising: f) separating the first liquid fraction into a fourth solid fraction, a fourth liquid fraction, and optionally a fat fraction, wherein optionally the second solid fraction comprises a content (w / w) of ash in dry matter that is higher than the content (w / w) of ash in dry matter in the fourth solid fraction.

4. The method according to any one of the preceding claims, comprising: g) drying the second solid fraction to provide a dry first solid product comprising ash and protein.

5. The method according to any one of claims 2 to 4, comprising: h) drying the third liquid fraction to provide a dry third solid protein product comprising ash and protein.

6. The method according to any one of claims 3 to 5, comprising one or more of i)-k):i) combining the third solid fraction and fourth solid fraction to provide a second solid product comprising ash and protein, and optionally drying to provide a dry second solid product comprising ash and protein; j) drying the fourth liquid fraction to provide a dry fourth solid protein product comprising ash and protein; k) combining the third liquid fraction and fourth liquid fraction to provide a fifth liquid fraction comprising ash and protein, and optionally drying to provide a dry fifth solid product comprising ash and protein.

7. The method according to any one of claims 5 to 6, wherein the first solid product comprises a content (w / w) of ash in dry matter that is higher than the content (w / w) of ash in dry matter in one or more of: the second solid product, the third solid protein product, the fourth solid protein product and the fifth solid product.

8. The method according to any one of the preceding claims, wherein the second solid fraction comprises one or more of i. to ii.: i. an ash to protein weight ratio in dry matter of 2:1 to 1 :2;II. an ash content in dry matter ranging from 30% to 60% (w / w).

9. The method according to any one of claims 2 to 8, wherein the third solid fraction comprises one or more of i. to ii.: i. an ash to protein weight ratio in dry matter of 1 :6 to 1 :15; ii. an ash content in dry matter ranging from 1% to 15% (w / w).

10. The method according to any one of claims 3 to 9, wherein the fourth solid fraction comprises one or more of i. to ii.: i. an ash to protein weight ratio in dry matter of 1 :6 to 1 :15; ii. an ash content in dry matter ranging from 1% to 15% (w / w).11 . The method according to any one of the preceding claims, wherein the first solid fraction comprises a fat content in dry matter of up to 15% (w / w), preferably in the range of 0.1% to 15%, more preferably 3% to 12%, most preferably 2% to 10%.

12. The method according to any one of the preceding claims, comprising adding an aqueous solution to the first solid fraction in c), wherein volume of the aqueous solution is smaller than volume of the first liquid fraction in b), wherein optionally the volume of the aqueous solution is 20% to 60% of the volume of the first liquid fraction.

13. The method according to any one of the preceding claims, wherein the contacting with at least one protein hydrolysing enzyme either increases protein content in the second liquid fraction or decreases protein content in the second solid fraction or both when compared to a method involving no contacting with at least one protein hydrolysing enzyme.

14. The method according to any one of the preceding claims, wherein the animal material is selected from food-producing animal by-products comprising one or more selected from meat and connecting tissues, trimmings, bones, blood, feathers, hair, internal organs, digestive tract, necks, and heads.

15. The method according to any one of the preceding claims, wherein prior to heating in a), the animal material is comminuted to a particle size of up to about 50 millimetres, or up to about 40 mm, or up to about 30 mm, or up to about 20 mm, or up to about 10 mm, or up to about 5 mm, optionally by grinding, mixing, milling or crushing.

16. An arrangement for treating animal material, comprising: a) a first vessel and a second vessel, wherein the first vessel is connected to the second vessel with a material transport connection, wherein the first vessel is configured for heating the animal material, optionally to a temperature in the range of 50°C to 100°C; b) first separation means for solid-liquid separating the heated animal material into a first solid fraction and a first liquid fraction so that the first solid fraction is transported through the material transport connection to the second vessel; c) the second vessel is configured to contact the first solid fraction with at least one protein hydrolysing enzyme to provide an enzyme-treated solid fraction; d) second separation means for solid-liquid separating the enzyme-treated solid fraction into a second solid fraction and a second liquid fraction.

17. The arrangement according to claim 16, comprising: e) third separation means for solid-liquid separating the second liquid fraction into a third solid fraction, a third liquid fraction, and optionally a fat fraction, optionally wherein the arrangement further comprises a heating means for heating the second liquid fraction to a temperature in the range of 50°C to 100°C, wherein the heating means is arranged to heat the second liquid fraction before the solid-liquid separation.

18. The arrangement according to claim 16 or 17, comprising: f) fourth separation means for separating the first liquid fraction into a fourth solid fraction, a fourth liquid fraction, and optionally a fat fraction.

19. The arrangement according to any one of claims 16 to 18, comprising: g) first drying means for drying the second solid fraction to provide a dry first solid product comprising ash and protein.

20. The arrangement according to any one of claims 17 to 19, comprising: h) third drying means for drying the third liquid fraction to provide a dry third solid protein product comprising ash and protein.21 . The arrangement according to any one of claims 18 to 20, comprising one or more of i)-k): i) second drying means for drying a combined third solid fraction and fourth solid fraction to provide a dry second solid product comprising ash and protein; j) fourth drying means for drying the fourth liquid fraction to provide a dry fourth solid protein product comprising ash and protein; k) fifth drying means for drying a combined third liquid fraction and fourth liquid fraction to provide a dry fifth solid protein product comprising ash and protein.

22. The arrangement according to any one of claims 16 to 21 , comprising means for adding an aqueous solution to the first solid fraction in the second vessel, wherein optionally the volume of the aqueous solution is smaller than volume of the first liquid fraction in b), wherein optionally the volume of the aqueous solution is 20% to 60% of the volume of the first liquid fraction.

23. The arrangement according to any one of claims 16 to 22, wherein the animal material is selected from food-producing animal by-products comprising one or more selected from meat and connecting tissues, trimmings, bones, blood, feathers, hair, internal organs, digestive tract, necks, and heads24. The arrangement according to any one of claims 16 to 23, comprising means for comminuting the animal material to a particle size of up to about 50 millimetres, or up to about 40 mm, or up to about 30 mm, or up to about 20 mm, or up to about 10 mm, or up to about 5 mm, before placing the animal material in the first vessel, optionallywherein the means for comminuting is selected from a grinder, mixer, a mill or a crusher.

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