A method of producing a micro-foamed cheese product

Abstract

The present invention relates to a micro-foamed cheese product and a method of producing a micro-foamed cheese product comprising providing an extruder having a gas loading zone applying a milk protein coagulate comprising milk protein, water and at least 0.8% (w / w) fat relative to the wet weight of the milk protein coagulate into the inlet of the extruder; rotating the longitudinally arranged screw to create a flow of the milk protein coagulate from the inlet to the outlet; heating the milk protein coagulate to 60°C to 140°C to melt the milk protein coagulate; dispersing a gas in the molten milk protein coagulate in the gas loading zone; and cooling the molten milk protein coagulate to obtain the micro-foamed foamed cheese product.

Description

[0001] Title

[0002] A METHOD OF PRODUCING A MICRO-FOAMED CHEESE PRODUCT

[0003] Technical Field

[0004] The present invention relates to a method of producing a cheese product and to the cheese product. In the method, a curd is extruded to provide a porous micro-foamed cheese product.

[0005] Background Art

[0006] Cheese has been a staple product in the food industry for centuries. By 2026, the global cheese market size is projected to reach US$ 106 billion due to an increased demand for protein-rich food products Heightened consumer concerns about the environment and health have sparked a wave of innovative products comprising unique textures and structures, which allows cheese manufacturers to explore new technologies to meet these product demands.

[0007] Today, high-moisture extrusion cooking (HMEC) is the most common technology used to texturize protein-based raw materials in the food industry. The texturization of milk proteins by extrusion has a large potential to be processed into new innovative food concepts. However, relatively little attention has been paid in the literature to the texturization of milk proteins, especially caseins. Recently, extrusion technology has successfully been used to extrude renneted casein gel particles (cheese curd) into hierarchically fibrous structures that mimic the texture of meat and customized cheese products..

[0008] For example, AU 2010 201 423 B2 provides a process for the manufacture of a multiple texture food product, e.g. an aerated dairy material. The process includes providing a dairy material, freezing the dairy material, aerating the frozen dairy material, shaping the aerated, frozen dairy material, wherein the aerated dairy material has a Stevens firmness of 20 or more at a temperature from 5 to 100°C and a water activity of 0.9 or more.

[0009] WO 2021 / 032866 Al discloses a method for the production of protein-containing foamed food product. In the method, a raw protein material is metered into an extruder, and pores are formed in the extruder by introducing a gas into the extruder. The rawmaterial may be vegetable protein, insect protein, cell protein, in particular of yeast, bacteria, microalgae, or mould.

[0010] US 5 194 283 A presents a process for the continuous production of composite cheese. The process comprises co-extruding materials consisting essentially of two differing unripened drained curds at a temperature of from 0 - 30°C into a form of a strand such that one extruded curd forms a core of the strand and such that one extruded curd forms a layer about the core. The curds may be aerated to lighten their texture.

[0011] Zink et al. (Current Research in Food Science, 7, 2023) disclose a micro-foaming process for texturized High-Moisture Meat Analogues. A soy protein concentrate powder was dosed into a first extruder segment, before injecting canola oil in a second extruder barrel segment followed by N₂ gas injection.

[0012] There is presently a need to provide cheese-based products having improved mechanical properties, and the present invention aims to address this need.

[0013] Summary

[0014] The present invention relates to a method of producing a micro-foamed cheese product. The method comprises the steps of:

[0015] -providing an extruder having an extruder barrel with an inlet, and an outlet with a cooling die, at least one longitudinally arranged screw in the extruder barrel, a heating arrangement configured to heat a content in the extruder barrel, and a gas loading zone between the inlet and the outlet;

[0016] -providing a milk protein coagulate comprising milk protein, water and at least 0.8% (w / w) fat relative to the wet weight of the milk protein coagulate and applying the milk protein coagulate into the inlet of the extruder;

[0017] -rotating the longitudinally arranged screw to create a flow of the milk protein coagulate from the inlet to the outlet;

[0018] -heating the milk protein coagulate to a temperature in the range of 60°C to 140°C to melt the milk protein coagulate;

[0019] -dispersing a gas in the molten milk protein coagulate in the gas loading zone; and -cooling the molten milk protein coagulate in the cooling die to obtain the microfoamed foamed cheese product.In another aspect, the invention relates to a micro-foamed cheese product. The micro-foamed cheese product is obtainable in the method of the invention. The microfoamed cheese product comprises an extrudate matrix having milk protein in the range of 30% (w / w) to 98% (w / w), e.g. 30% (w / w) to 90% (w / w), and lipid in the range of 0.8% (w / w) to 70% (w / w), e.g. 2% (w / w) to 60% (w / w), based on the dry weight of micro-foamed cheese product, and water in the range of 35% (w / w) to 60% (w / w) relative to the wet weight of the micro-foamed cheese product, gas bubbles dispersed in the extrudate matrix to provide a porosity in the range of 5% to 50%, which porosity is defined as the ratio of the volume of the gas bubbles in the extrudate matrix to the total volume of the extrudate matrix.

[0020] The dispersion of the gas into the milk protein coagulate combined with the extrusion induce an elongated or stretched orientation of structural components in the milk protein coagulate, such as gas bubbles, fat droplets and watery milk serum. In particular, the gas bubbles may be elongated near the entrance zone or at the entrance zone when the gas is dispersed into the milk protein coagulate. Upon cooling in the cooling die, the molten milk protein coagulate and also the structural components, especially gas bubbles, fat droplets and watery milk serum pockets, embedded in the milk protein coagulate are stabilised and fixed, so that a micro-foamed cheese product having elongated structural components, especially gas bubbles, is obtained.

[0021] The gas is dispersed under pressure and a porous foam structure is generated upon pressure release and superimposed cooling, such that the micro-foam bubbles are elongated and fixed upon cooling in their elongated shape state, thus forming an anisotropically stranded cheese protein network structure of adjustable anisotropy degree.

[0022] A milk protein coagulate is used in the present method, and any kind of milk protein coagulate may be used in the method. In general terms, a milk protein coagulate is obtained by treatment of milkwith a protease enzyme to coagulate the protein ofthe milk, or the milk protein can be coagulated by lowering the pH. Both of these coagulation methods can be supported by heat treatment, e.g. to a temperature in the range of 30°C to 60°C. Following coagulation, whether by a protease enzyme or acidification, the liquid, e.g. the whey, may be separated, e.g. fully or partially separated, from the coagulated protein. The milk may be from any mammal, especially from a cow, a water buffalo, a Mediterranean buffalo, a sheep, a goat, a camel, etc. The protease enzyme may be anyprotease enzyme, such as a rennet, e.g. a rennet obtained from the stomach of a ruminant mammal, e.g. a cow, a sheep, a goat, a camel, etc., or a rennet produced recombinantly in a microorganism or otherwise obtained from a microorganism. The milk protein coagulate may also be referred to as a "curd", and in the present context, the two terms may be used interchangeably.

[0023] The milk protein coagulate is obtained from milk, and the milk may be from any mammal. Milk has a natural content of protein, lipids, and other components, and the content of lipids and / or protein may be reduced or increased before coagulating the milk to the milk protein coagulate. For example, the naturally present lipid may be removed. In the present context, "full milk" represents the milk obtained from the mammal, and the lipids may be partially removed, or "skimmed", to provide a lipid-reduced milk. It is also possible to add a lipid component, e.g. a vegetable oil or butter. However, in an example, no lipid is added to the milk or the milk protein coagulate, e.g. after coagulation of the milk protein coagulate. It is especially preferred that a lipid is not added to the milk protein coagulate after introducing the milk protein coagulate into the extruder, e.g. it is preferred that no lipid is added to the extruder downstream of the inlet. Injection of a lipid, especially a vegetable oil, during the extrusion has been found to prevent formation of gas bubbles in the extrudate. Without being bound by theory, the present inventors believe that milk protein coagulates exist in an emulsified form and that when a lipid, especially a vegetable oil, is added during extrusion, the added lipid cannot form part of the emulsion, which further prevents micro-foaming of the milk protein coagulate.

[0024] The milk protein coagulate contains protein from the milk, or a milk or casein-based ingredient, and in addition to milk proteins, especially caseins, fat from the milk is typically bound to or otherwise entrapped with the milk proteins during the enzymatic treatment, so that the curd contains proteins and fat from the milk. In the present context, protein and fat in the milk protein coagulate may be referred to collectively as "components"; although the components include any constituent obtained from the milk, including water. Thus, the components may include protein, fat and water. In general terms, it is mainly the fat contained in the milk protein coagulate that allows the milk protein coagulate to melt, however the fat / moisture ratio as well as the protein structure play a complementary role. The content of fat, especially milk fat, in the curd is at least 0.8% (w / w), e.g. at least 2% (w / w), for example at least 5% (w / w), e.g. the curd has a fat content in the range of 10%(w / w) to 40% (w / w), e.g.15% (w / w) to 35% (w / w), or 20% (w / w) to 30% (w / w). If melting properties of the micro-foamed cheese product are important, e.g. if proper melting is intended, the lipid content should be at least 25% (w / w), e.g. at least 30% (w / w). The components of the milk protein coagulate may be referred to as a percentage of the milk protein coagulate. In the present context, percentages are by weight, e.g. as "% (w / w)", unless noted otherwise. The content of protein, especially milk protein, e.g. casein, may be in the range of 20% (w / w) to 50% (w / w), e.g. 20% (w / w) to 40% (w / w). The water content may be in the range of 35% (w / w) to 60% (w / w). The percentages for the milk protein coagulate may especially be provided on a wet basis of the milk protein coagulate, as the milk protein coagulate also contains water. Correspondingly, the amount of gas may also be provided as a percentage by weight, i.e. % (w / w), relative to the milk protein coagulate being processed. Likewise, the micro-foamed cheese product is also appropriately described in terms of the contents of fat and protein, and also water. Based on a wet weight, the composition of the micro-foamed cheese product may have the same composition as the milk protein coagulate, although the added gas may be considered. In particular, the micro-foamed cheese product may be described in terms of a composition on a dry weight basis, and the micro-foamed cheese product has milk protein in the range of 30% (w / w) to 90% (w / w), e.g. 30% (w / w) to 70% (w / w), 35% (w / w) to 60% (w / w) or 40% (w / w) to 50% (w / w), and lipid in the range of 2% (w / w) to 70% (w / w) e.g. 20% (w / w) to 70% (w / w), 30% (w / w) to 70% (w / w), 35% (w / w) to 60% (w / w) or 40% (w / w) to 50% (w / w), based on the dry weight of the micro-foamed cheese product. The water content is in the range of 35% (w / w) to 60% (w / w) relative to the wet weight of the micro-foamed cheese product. In general, as only the gas needs to be added during the extrusion, the dry weight composition of the milk protein coagulate is generally the same as of the dry weight composition of the micro-foamed cheese product.

[0025] The milk protein coagulate typically contains further components, e.g. salts, that may be referred to as an ash content. The salts generally include a metal ion, e.g. Na+, K+, or Ca2+, and a counterion, e.g. phosphate. The salt content of the milk protein coagulate may be adjusted as desired. For example, the milk protein coagulate may have a content of Ca2+in the range of 0.1% (w / w) to 2% (w / w), e.g. 0.5% (w / w) to 1% (w / w).

[0026] The milk protein coagulate has a pH, which can reflect how the milk protein coagulate was prepared, e.g. whether by a protease enzyme or acidification. It is also possible toadjust the pH. For example, the pH may be or be adjusted to be in the range of 5 to 7. e.g.

[0027] 5 to 6.5, or 5.2 to 6.3.

[0028] In an example, the milk protein coagulate is a curd. In a specific example, the milk protein coagulate is a curd commonly referred to as Cagliata. The term " Cagliata" is often used to describe a curd for manufacture of a Mozzarella-type cheese, and as such, the Cagliata is prepared from milk from a cow or a Mediterranean buffalo.

[0029] An extruder is used in the method of the disclosure, and the extruder has an inlet and an outlet, and a longitudinally arranged screw in the extruder barrel. The extruder barrel thus has a longitudinal dimension. The micro-foamed cheese product exits the extruder via the cooling die at the outlet, and therefore the micro-foamed cheese product, and also the extrudate matrix of the micro-foamed cheese product, can be said to have a direction parallel to the screw. The direction of the micro-foamed cheese product parallel to the screw may also be described as a dominant flow direction parallel to the screw. In the present context, the direction parallel to the screw, including the cooling die according to the design of the extruder, is generally referred to as the parallel direction of the extrudate matrix or the micro-foamed cheese product. The parallel direction may also be referred to as the longitudinal direction or longitudinal dimension, e.g. the extrudate matrix or the micro-foamed cheese product can be said to have a longitudinal direction or a longitudinal dimension. Correspondingly, the micro-foamed cheese product, and the extrudate matrix of the micro-foamed cheese product, also have a perpendicular direction. In general, the perpendicular direction may be any direction normal to the longitudinal direction. In the present context, the perpendicular direction may also be referred to as the transverse direction, and the two terms may be used interchangeably.

[0030] The inlet and the outlet of the extruder define a flow direction, i.e. from the inlet to the outlet, in the extruder and thereby also in the extruder barrel. The relative position of features and function of the extruder may be defined relative to each other with respect to the flow direction from the inlet to the outlet. Thus, features and functions of the extruder may be upstream ordownstream from each other, where "upstream" is closer to the inlet than the feature or function and "downstream" is closer to the outlet than the feature or function.

[0031] The extruder has a heating arrangement configured to heat a content in the extruder barrel. The heating arrangement may employ any appropriate technology to increase thetemperature. The extruder barrel may define sections along the barrel, where the heating arrangement is configured to provide each section with a defined temperature, including one or more sections that are not heated. For example, the extruder barrel may have a first section upstream of a second section, which in turn is upstream of a third section, and so forth. Any number of sections may be defined for the extruder barrel. For example, the extruder barrel may have a first section near or at the inlet, which first section is not heated, and second, third and fourth sections defined by gradually increasing temperatures from the heating arrangement. The extruder barrel may further be considered to define a number of zones, and a zone of the extruder barrel may be subjected to different parameters than a neighbouring zone, e.g. an upstream or a downstream zone.

[0032] The extruder has a gas loading zone between the inlet and the outlet. The gas loading zone defines the location where a gas is dispersed in the molten milk protein coagulate and the gas loading zone is part of a gas loading system. The gas loading system at least comprises a gas supply and a nozzle or the like for dispersing or injecting the gas into the molten milk protein coagulate and piping providing fluid communication between the gas supply and the nozzle. The gas loading zone may be at any section of the extruder barrel where the milk protein coagulate has been heated to melt the milk protein coagulate. The gas dispersed in the molten milk protein coagulate should be inert to the milk protein coagulate, and the gas should especially not contain components that can react chemically with components, e.g. protein or fat, of the milk protein coagulate, e.g. the gas may be selected from N₂, N₂O, CO₂, or combinations of these, although SO₂ is also contemplated.

[0033] In an example of the method, a single-screw extruder is used, and in another example a twin-screw extruder is used. The screw is arranged longitudinally and has a diameter appropriate for the extruder barrel, and the extruder barrel correspondingly also has a diameter. The diameter of the extruder barrel can be selected based on the intended scale of operation. Rotation of the longitudinally arranged screw creates a movement of the content of the extruder barrel from the inlet to the outlet and in addition subjects the content of the extruder barrel to shear. The shear rate in the extruder barrel determines the degree of dispersing of the gas bubbles, e.g. for foam generation, as well as of the fat droplets, e.g. for forming an emulsion, in the watery protein-matrix phase. The shear rate in the extruder barrel can also be considered to determine the degree of the extruded mass transport. The approximate calculation of the shear rate is done by dividing the localcircumferential velocity of an extrusion screw element (1) relative to the extrusion housing (2) and / or relative to a screw element of the second screw (3), divided by the gap size between (1) and (2) or (1) and (3), respectively. In an example, the longitudinally arranged screw is rotated to provide a shear rate in the range of 50 1 / s to 1000 1 / s, e.g. 200 1 / s to 500 1 / s, or 3001 / s to 400 1 / s. The related shear stress of relevance for micro-structuring the milk protein coagulate melt may be calculated from the shear rate with due consideration of the parameters, especially the viscosity, of the content, i.e. the milk protein coagulate in the present method. In an example, the longitudinally arranged screw has a diameter in the range of 20 mm to 60 mm, and the longitudinally arranged screw is rotated at a rotation rate in the rate of 100 rpm to 400 rpm, e.g. 150 rpm to 300 rpm, or 200 rpm to 300 rpm. Accordingly, the related shear rate range in case of a screw channel height of 2 millimeters is between 52.36 and 628.32 1 / s, which in case of a (nonNewtonian) viscosity of 10 Pas (at 52.36 1 / s) and 2 Pas (at 628.32 1 / s) led to acting shear stresses of 523.6 Pa or 1256.64 Pa, respectively.

[0034] The molten milk protein coagulate is cooled in a cooling die to obtain the microfoamed foamed cheese product. The cooling die can be said to be at an outlet end of the extruder barrel. The temperature of the cooling die, including the extruder connection interface and the cooling die connection interface, may be selected freely, e.g. depending on the milk protein coagulate used and the temperature to which the milk protein coagulate has been heated. In particular, the molten milk protein coagulate may be cooled in the cooling die to a temperature below 60°C. For example, the milk protein coagulate may be cooled to a temperature in the range of ambient temperature, e.g. about 20°C or about 25°C, to 60°C. For example, the milk protein coagulate may be cooled to a temperature in the range of 20°C to 50°C. In a specific example, the cooling temperature is adjusted to the temperature dependent viscosity of the molten milk protein coagulate in such a way that the solidification of the structure enables reaching entrapment and fixation of flow-induced structural component shapes like ellipsoidal to filamentous gas bubbles and fat drops as well as serum pockets and protein strands. This leads to desirable textural or sensorial product characteristics which can be adjusted by the degree of the deformation-induced anisotropy.

[0035] The cooling die may have any design and it may be configured to provide specific functions appropriate for the micro-foamed cheese product to be produced in the methodof producing a micro-foamed cheese product. For example, the cooling die may comprise an entrance section wherein the cross-sectional area between an extruder connection interface and a cooling die connection interface is reduced to accelerate the average mass flow velocity, thus generating an elongational flow field. For example, the cooling die may comprise an entrance section wherein the cross-sectional area between an extruder connection interface and a cooling die connection interface is reduced to accelerate the flow velocity in the cooling die relative to the flow at the extruder connection interface by a factor in the range of 2 to 10, e.g. 2 to 5. This may be complemented by a flexible volume flow rate adjustment in the range of a factor of 1 to 5. This leads to stretching the structural components in the extruded cheese coagulate melt such as protein bundles, gas bubbles, fat droplets and serum pockets. In a specific example, the cross-sectional area between the extruder connection interface and the cooling die connection interface may be reduced by a factor in the range of 2.5 to 5 to thereby generate an average elongation rate in the range of ε̇ = 0.05 to 3.0 1 / s by volume flow rate adjustment. With these designs of the cooling die, the structural components in the micro-foamed cheese product, especially protein molecules and / or protein bundles, gas bubbles, fat droplets and milk serum pockets are stretched and / or elongated while cooling in the cooling die, e.g. the die entrance section and also in the cooling die, and thereby the elongated structural components are fixed upon cooling.

[0036] The micro-foamed cheese product can be described in terms of the porosity provided by the gas bubbles of the gas dispersed during the extrusion. The present inventors have found that dispersing gas into the molten milk protein coagulate provides a number of advantages for the micro-foamed cheese product produced in the method. In particular, the gas bubbles in the micro-foamed cheese product open a new horizon for textural / sensorial and also techno-functional properties of consumer relevance. The volume extension of the micro-foamed cheese reduces volumetric calorie density and is expected to contribute to accelerated satiation and thus to a reduced tendency of overeating being of relevance for human nutrition optimisation in the context of obesity risk reduction. The textural impression of a foamed cheese is dominated by reduced hardness and increased softness and creaminess depending on the cheese type. Moreover, for the typical application of Mozzarella-type cheese as pizza topping the melting of the cheese without fat separation is supported by the micro-foamed structure and in addition the foambubbles can act as nucleators for blister formation and support a desirable narrow blister size distribution and even distribution across the pizza. Such characteristics are equally interesting for other food / meal preparations where the product is consumed in a molten state like potato gratin, Swiss Raclette and fillings or coatings of bakery products. Thus, the micro-foamed cheese product is especially useful in any context where the micro-foamed cheese product is to be molten in the preparation of a food to be eaten by a consumer. The shear applied during the extrusion combined with the dispersion of a gas provides that the gas bubbles are at least relatively homogeneously distributed in the micro-foamed cheese product, and therefore the micro-foamed cheese product has a homogeneous appearance where the effects of the gas bubbles apply, e.g. apply equally, throughout the mass of the micro-foamed cheese product. The micro-foamed cheese product of the invention behaves more predictable, especially with respect to fat separation, when exposed to heat, i.e. to melt the micro-foamed cheese product, compared to a conventional cheese product, and thereby the micro-foamed cheese product in turn improves the manufacture of a cheesecontaining food product where it is intended to melt the cheese. Moreover, the distributed, especially the homogeneously distributed gas bubbles, allow that the consumer achieves the impression of a food product where the micro-foamed cheese product is added contains a larger amount of cheese, e.g. compared to a similar food product with a conventional cheese, and thereby the amount of cheese in a cheese-containing food product can be reduced compared to a food product with a conventional cheese product. Besides the before-mentioned health benefits to the consumer, this can also contribute to making manufacture of the food product cheaper and correspondingly also for a food product containing such cheese product. It is especially preferred that the milk protein coagulate is a milk protein coagulate commonly used for making cheeses intended to be molten before eating. For example, the milk protein coagulate may be a milk protein coagulate or curd used for the manufacture of a Mozzarella-type cheese, e.g. the milk protein coagulate may be a Cagliata curd.

[0037] The porosity of the micro-foamed cheese product is broadly defined as the ratio of the volume of the gas bubbles in the extrudate matrix to the total volume of the extrudate matrix. The volume of the gas bubbles in the extrudate matrix is generally correlated with the number and size of the bubbles in the extrudate matrix, and thereby the porosity can be measured by measuring the number distribution of the gas bubble diameters in a cross-sectional view of the extrudate matrix. As the gas bubbles in the extrudate matrix are generally homogeneously distributed in the extrudate matrix independently of their size, the gas bubbles can be recorded in a cross-sectional view of an image, e.g. a microscopy image, of an extrudate matrix, with the gas bubbles in the cross-sectional view being representative of the gas bubbles in the extrudate matrix, e.g. in the entire extrudate matrix. Thus, the porosity of the extrudate matrix may be determined in a cross-sectional view of the extrudate matrix. The cross-sectional view may be in any direction of the extrudate matrix. For example, the cross-sectional view may be in a plane normal to the longitudinal direction, i.e. the flow direction, of the extrudate matrix. For example, a cross-sectional view of the extrudate matrix may be prepared, and the cross-sectional view depicted, e.g. using a microscope at an appropriate magnification, and the bubbles may be recorded. In particular, the bubble diameter (x) distribution or mean bubble diameter in the cross-sectional view of the extrudate matrix, e.g. in a cutting plane, may be determined by image analysis as number distribution qo(x) and the integral mean value of the sum of bubble volumes may be determined as ∫x3q0(x) dx for the bubbles with bubble diameter Xmin to Xmax (lower and upper limits of the integral). This corresponds to the total bubble volume Vbubblein the measured extrudate matrix under the assumption that the cut plane is representative for the total volume Vtotalof the extrudate matrix considered. The porosity, e.g. the cutting plane-related porosity, Ec is then received as the ratio of the bubble cross sectional area FBC in the cutting plane to the area of the total cutting plane Fc (£FC = FBC / FC). For homogeneously distributed gas bubbles in the micro-foamed cheese product volume, the thereby determined "cutting plane porosity" EFC equals the real porosity in the sample volume, £FC = £V = Vbubble / Vtotai. In particular, the extrudate matrix comprises gas bubbles to provide a porosity in the range of 5% to 50%. The porosity may for example be in the range of 5% to 45%, or 5% to 40%. In demonstrated examples of the invention, the porosity is in the range of 10% to 35% as illustrated in Figure 5.

[0038] Gas bubbles in the extrudate matrix are provided by dispersing a gas in the molten milk protein coagulate in the gas loading zone. Specifically, the milk protein coagulate is heated in the extruder to melt the milk protein coagulate. Thus, the milk protein coagulate may be heated to any temperature sufficient to melt the milk protein coagulate, although it is preferred that the milk protein coagulate is heated to at least 60°C. In general terms, the milk protein coagulate should not be heated to excessive temperatures, and the milkprotein coagulate should therefore be heated to a temperature in the range of 60°C to 140°C to melt the milk protein coagulate. Other temperatures may be at least 80°C, at least 85°C, or at least 90°C. In any case, the milk protein coagulate should not reach temperatures beyond 140°C, e.g. up to 120°C or 100°C at the extruder outlet or the cooling die entrance.

[0039] The sizes and shapes of the gas bubbles generally reflect the processing parameters during the production. For example, the shear provided by the screw in the extruder can distort the bubbles from a spherical shape, and individual gas bubbles may coalesce to form larger gas bubbles. The likelihood of coalescence is increased especially by the amount of gas dispersed in the milk protein coagulate. The gas bubbles may be described to have a diameter, but the gas bubbles are not limited to have a spherical shape, and in the present context, the "diameter" more generally refers to an equivalent diameter dimension, e.g. to the largest dimension, of a gas bubble, e.g. as recorded in a cross-sectional view of the extrudate matrix, especially in a cross-sectional view of the extrudate matrix parallel to the flow direction. The diameters may for example be in the range of 10 pm to 5 mm, e.g. in the range of 20 pm to 500 pm, or 30 pm to 100 pm. An exemplary gas bubble of an extrudate matrix is illustrated in the microscopic image in panel B of Figure 2, where it is compared to the milk protein coagulate in panel A that does not have a gas bubble included, and in Figure 3, panel C shows macroscopic cross-sections of micro-foamed cheese products of the invention compared to an extruded cheese product where no gas was injected. Gas bubbles are also seen in both panels A and B of Figure 4.

[0040] The gas bubbles may be defined in terms of their size distribution. The size distribution, e.g. the size distribution width, may for example be defined in terms of a Span value determined as Span = (X90.3 - x10.3) / x50.3, with X90.3, X10.3, and X50.3 denoting the respective 10%, 50% and 90% percentile related diameters of the volume distribution of the bubble diameters. The Span value should be <2. Thus, a Span value <2 represents a narrow distribution of the gas bubble diameters in the extrudate matrix, and thereby a Span value <2, preferably <1.5, <1.4, or <1.3, is especially useful for the micro-foamed cheese product to reflect the advantages for an evenly structured, or homogeneous, microfoamed cheese product. A particularly preferred Span value is <1.1.

[0041] The structural components and the gas bubbles generally have a parallel dimension and a perpendicular dimension. Due to the design of the process, any structure or structuralcomponent, including the gas bubbles, in the micro-foamed cheese product is generally stretched or elongated in the parallel dimension. The present inventors believe that the stretching or elongation is especially caused by the combination of (i) dispersing a gas into the molten milk protein coagulate and (ii) cooling of the molten milk protein coagulate in the cooling die to fix such anisotropically deformed foam structure. In particular, a bubble diameter range of 5 pm to 2 mm, preferably 50 pm to 0.5 mm and most preferably 100 pm and 200 pm, support an evenly elongationally deformed or stretched structure into the extrudate flow direction as a main consequence of the elongational flow conditions in the die entrance domain and the shear flow conditions in the cooling die. Thereby, the gas bubbles generally have a parallel dimension and a perpendicular dimension and an aspect ratio of the parallel dimension to the perpendicular dimension of at least 1.2. The present inventors believe that the aspect ratio of the parallel dimension to the perpendicular dimension of at least 1.2 reflects that desirable anisotropy of the micro-foamed cheese product, and it is preferred that the aspect ratio of the parallel dimension to the perpendicular dimension is at least 1.3, at least 1.4, at least 1.5, at least 2, at least 2.5 or at least 3. However, the aspect ratio typically does not exceed 20. The aspect ratio of the gas bubbles may in particular be controlled either by (a) the configuration of the cooling die, for example when the cooling die comprises an entrance section wherein the cross-sectional area between the extruder connection interface and the cooling die connection interface is reduced by a factor in the range of 2.5 to 5, or (b) by the volume flow rate which if increased will generate larger elongation and shear stresses in the die entrance and die flow, thus leading to an increase in the stretching of the foam bubbles as well as of fat droplets, serum pockets and the protein matrix in the neighbourhood of these and consequently forming also a strand-like protein matrix structure most desirable for the mozzarella cheese type. The aspect ratio of the gas bubbles may also be controlled by a combination of (a) and (b).

[0042] The porosity of the extrudate matrix of the micro-foamed cheese product is generally reflected by the amount of gas dispersed in the molten milk protein coagulate, but the amount of gas is provided relative to the milk protein coagulate provided to the extruder, e.g. as a percentage by weight especially relative to the wet weight of the milk protein coagulate. For example, up to 0.4% (w / w) gas may be dispersed in the milk protein coagulate. It is preferred that the gas is dispersed in an amount of 0.01% (w / w) to0.5% (w / w), e.g. in the range of 0.02% (w / w) to 0.3% (w / w), 0.05% (w / w) to 0.2% (w / w), or 0.1% (w / w) to 0.15% (w / w). The relation between the porosity of the extrudate matrix and the amount of gas dispersed in the molten milk protein coagulate is illustrated in Figure 5.

[0043] The micro-foamed cheese product is produced in an extrusion process, and the micro-foamed cheese product therefore comprises an extrudate matrix. The extrudate matrix has a composition, especially a composition of protein and fat, but also water, reflected by the milk protein coagulate used in the method of producing the micro-foamed cheese product. In addition to the extrudate matrix, the micro-foamed cheese product comprises gas bubbles dispersed in the extrudate matrix. The gas bubbles thus make the cheese product of the invention "micro-foamed". In the context of the present disclosure, comparisons are made with extruded milk protein coagulates where no gas has been dispersed but where parameters for the extrusion may otherwise be as for the present invention. When no gas has been dispersed during the extrusion, the corresponding product may be referred to as "non-foamed", although the non-foamed product may also be said to comprise an extrudate matrix. However, in the present context, the terms microfoamed cheese product and extrudate matrix may be used interchangeably, when the extrudate matrix refers to the extrudate matrix of the micro-foamed cheese product. Thus, extrudates are referred to as micro-foamed (MF) extrudates, where a gas has been dispersed in the extrudate and non-foamed (NF) extrudates, in which the extrudate has not been injected with a gas.

[0044] The micro-foamed cheese product, and also the extrudate matrix of the microfoamed cheese product, especially the properties of the micro-foamed cheese product and the extrudate matrix of the micro-foamed cheese product, may be described in terms of parameters that can be measured for the micro-foamed cheese product. In particular, properties that are relevant for product properties from the consumer perspective. For example, the micro-foamed cheese product may be described with a tensile strength, or an extensibility, and the micro-foamed cheese product may further be described with parameters derived from the tensile strength and the extensibility. For example, a tensile test may be used to quantify the extensibility of the extrudate matrix or the micro-foamed cheese product. Specifically, a tensile parameter may be recorded by fixing two opposite ends of a sample and then subjecting the sample to deformation at a pre-defined speed and recording the force and deformation length or stretch length to breakage. The tensileforce may be recorded until the breaking point of the extrudate sample to obtain the extensibility of the extrudate sample. Thus, the extensibility denotes the maximum uniaxial extension of a body, e.g. a gas bubble, a foam bubble, an oil drop, a protein strand, or the extrudate matrix, e.g. the integral extrudate matrix, before break-up.

[0045] The micro-foamed cheese product of the present disclosure typically has a reduced tensile strength of up to 80% compared to a non-foamed pendant, e.g. at ambient or room temperature, prepared with the same extrusion parameters but without dispersing gas into the molten milk protein coagulate, e.g. in the range of 30% to 80%, or 30% to 60%. For example, the micro-foamed cheese product produced in the present method of producing a micro-foamed cheese product may have a tensile strength of up to 80%, e.g. in the range of 30% to 80%, of a cheese product subjected to the steps of rotating the longitudinally arranged screw, heating the milk protein coagulate and cooling the molten milk protein coagulate as are also used to produce the relevant micro-foamed cheese product, but without the step of dispersing a gas in the molten milk protein coagulate. Exemplary tensile strengths of micro-foamed cheese products of the present disclosure and cheese products produced without dispersing a gas into the molten milk protein coagulate are shown in the panels D, E and F of Figure 7.

[0046] The micro-foamed cheese product of the present disclosure typically has a reduced hardness of up to 60% compared to a non-foamed pendant prepared with the same extrusion parameters but without dispersing gas into the molten milk protein coagulate, e.g. in the range of 10% to 60%, or 30% to 60%. For example, the micro-foamed cheese product produced in the present method of producing a micro-foamed cheese product may have a hardness of up to 60%, e.g. in the range of 10% to 60%, of a cheese product subjected to the steps of rotating the longitudinally arranged screw, heating the milk protein coagulate and cooling the molten milk protein coagulate, but without the step of dispersing a gas in the molten milk protein coagulate. Exemplary hardness values of microfoamed cheese products of the present disclosure and cheese products produced without dispersing a gas into the molten milk protein coagulate are shown in Figure 8.

[0047] The present inventors have surprisingly observed that the micro-foamed cheese product, and also the extrudate matrix of the micro-foamed cheese product behaves anisotropically, especially with respect to the parallel direction and the perpendicular direction of the micro-foamed cheese product. Thereby, the micro-foamed cheese product,and the extrudate matrix of the micro-foamed cheese may be described in terms of an anisotropic structure index, A, which is generally defined as the structure parameter x recorded for the parallel direction relative to the same structure parameter x recorded for the perpendicular direction. The anisotropic structure index, A, may also be referred to as the anisotropic index, A, and the two terms may be used interchangeably. The structure parameter x may be any structure parameter, although particularly relevant structure parameters are extensibility, compressibility, tensile strength, compression strength and cutting strength of the extrudate matrix in the respective direction. However, the structure parameterx may also be related to structure parameters detected by vision (e.g. the aspect ratio of stretched gas bubbles). The anisotropic structure index, A, is generally defined in Equation 1:

[0048] „vStructure parameter x in parallel directionr_.

[0049] A = - - - - - Equation 1 Structure parameter x in perpendicular direction

[0050] For the micro-foamed cheese product and the extrudate matrix of the micro-foamed cheese, the anisotropic structure index ASxis ≠ 1, thus reflecting the processing-induced anisotropy. The anisotropic structure index A should be at least 1.2, or 1.3. For example, anisotropic structure index A may be in the range of 1.5 to 3.0. In an example, the anisotropic structure index A may be related to the tensile strength (o) parameter and denoted A, as defined in Equation 2, or the anisotropic index A may be related to the extensibility parameter E as defined in Equation 3 and denoted ASE. The anisotropic structure index A may also be related to the ellipsoidal to filamentous deformation of gas bubbles, fat droplets, serum pockets or protein strands detected by vision and characterized by a mean aspect ratio L / D and thus being denoted as AL Ddefined in Equation 4

[0051] Thus, the anisotropic indices may be:

[0052] Tensile parameter a parallel to shear directionr_. _nA° = - - - - - Equation 2

[0053] Tensile parameter a perpendicular to shear direction

[0054] _ Extensibility parallel to shear direction at On 3]

[0055]

[0056] sExtensibility perpendicular to shear directionAspect ratio L / D parallel to shear direction

[0057] A [Equation 4]

[0058]

[0059] Aspect ratio L / D perpendicular to shear direction

[0060] In an example, ASEis in the range of 1.5 to 3.0, see Figure 6, and the extensibility is the maximum stretch length measured at rupture of the extrudate matrix in the respective direction. Figure 6 also demonstrates clearly the influence of the rotational screw speed on the achieved anisotropy structure index. Lower rpm (250) lead to the gas bubble dispersion under lower shear stresses thus resulting in larger gas bubbles. The latter are more easily deformable under the acting stresses in the die entrance / die flow than smaller bubbles generated at higher rpm. Accordingly, the larger gas bubbles generated at 250 rpm at a mass flow rate of 20 kg / h in the applied extruder lead to a more strongly pronounced stranding of the protein matrix and thus higher anisotropy index values compared to higher rpm-based runs with smaller diameter gas bubbles of reduced deformability. The increase in injected gas fraction typically assists the trend of generating larger, more deformable bubbles. Only in case of larger gas fractions (here 0.15% (w / w)) a limit of dispersible gas fraction under the given processing conditions may be exceeded, meaning that the gas is no longer fully dispersed but drained to the extrudate surface and the environment.

[0061] A special feature of the present method and the resulting micro-foamed cheese product concerns the adjustability of the structural anisotropy by generating gas bubbles, fat droplet and serum pocket shapes which are elongated (stretched) into the flow direction, thus also supporting protein strand formation between such stretched bubbles and droplets. Figure 9 demonstrates a comparison between cutting planes of an extrudate into the flow direction (= parallel cut, symbol: II, panel B in Fig. 9) and perpendicular to the flow direction (= transversal cut, symbol +, panel A in Fig. 9) for a micro-foamed milk protein coagulate. This enables clear differentiation between the elongationally stretched gas bubbles, fat droplets and serum pockets in the parallel cut and the expected spherical cross sections of these structure elements in the transversal cut.

[0062] Without being bound by any theory, the present inventors believe that the combination of using extrusion and dispersing gas in the molten milk protein coagulate arrange the fibres, especially protein fibres, in the milk protein coagulate to be generally parallel with the flow direction in the extruder thereby creating the anisotropy of major influence on the mechanical / textural characteristics of the resulting micro-foamedextrudates. Further without being bound by any theory, the present inventors consider the observation supported by how (a) modifying, e.g. increasing, the shear rate in the extruder which determines the gas dispersing degree and the related gas bubble size, by the rotational speed of the screw in the extruder barrel and (b) adjusting the elongation and shear rates and the structure fixation conditions in the cooling die entrance and cooling die, by adjusting the geometrical flow conditions and the cooling rate in these sections provides adjustability of a maximum anisotropic index > 1.5 to 2, preferably > 2 to 3, enabling new mechanical / textural product structure generation of added value for product developers and consumers.

[0063] In a specific example, the longitudinally arranged extruder screw, e.g. the longitudinally arranged extruder screws, has a diameter in the range of 20 mm to 60 mm, and the longitudinally arranged screw is rotated at a rotation rate in the rate of 100 rpm to 300 rpm, to provide an ASEin the range of 1.5 to 3.0. This example is especially relevant when a twin-screw extruder is used at 250 rpm, as demonstrated in Figure 6, and respective average shear average rates about 55 1 / s in the extrusion screw channel for gas dispersion as well as of elongation rates of ca. 0.05 to 0.1 1 / s and average wall shear rates of ca. 2.3 to 3.0 1 / s in the die entrance and die section, respectively. Figure 6 shows exemplary anisotropic indices obtained in the method of the invention compared to anisotropic indices obtained for a cheese product extruded without injection of gas. Thus, the method of the invention allows an improved control of the texture of extruded micro-foamed cheese products.

[0064] In other aspects, the invention relates to various uses of the micro-foamed cheese product of the disclosure. For example, the micro-foamed cheese product may be used, e.g. in a particulated or shredded format, as a component fortopping a food item. Relevant food items are all food items that are subjected to heating in an oven, e.g. a pizza or the like. The micro-foamed cheese product may also be used, e.g. in a particulated or shredded format, as a component for inclusion in a food product matrix. In general, the microfoamed cheese product may be included in any food product, e.g. a food product matrix where it is intended to melt the micro-foamed cheese product at any stage in making the food product ready for consumption. For example, the micro-foamed cheese product may be used as a food product for direct consumption or as a component mixed into another food intended for direct consumption, e.g. a salad. The micro-foamed cheese product mayalso be used as a food product for cooking in case of non-melting properties are achieved, e.g. when the lipid content is low.

[0065] Any embodiment of the invention may be used in any aspect of the invention, and any advantage for a specific embodiment applies equally when an embodiment is used in a specific aspect.

[0066] Brief Description of Drawings

[0067] In the following the invention will be explained in greater detail with the aid of an example and with reference to the schematic drawings, in which

[0068] Figure 1 shows a schematic view of an extruder for use in the method of the invention;

[0069] Figure 2 shows microstructure images of a milk protein coagulate and a microfoamed cheese product of the invention;

[0070] Figure 3 shows Videometer macrostructure images of a milk protein coagulate extrudate and a micro-foamed cheese product of the invention and of non-micro foamed cheese products of the prior art;

[0071] Figure 4 shows cross-sectional X-ray microcomputed tomography images of microfoamed cheese products of the invention;

[0072] Figure 5 shows porosities of micro-foamed cheese products of the invention;

[0073] Figure 6 shows anisotropic structure indices of micro-foamed cheese products of the invention and of non-micro foamed cheese products of the prior art;

[0074] Figure 7 shows extensibilities and tensile strengths of micro-foamed cheese products of the invention and of non-micro foamed cheese products of the prior art;

[0075] Figure 8 shows hardness values of micro-foamed cheese products of the invention and of non-micro foamed cheese products of the prior art;

[0076] Figure 9 demonstrates structural anisotropy detected by image analysis in a sample cross sections;

[0077] Figure 10 demonstrates the visual appearance of micro foamed cheese products of the invention and non-micro foamed cheese products of the prior art.The invention is not limited to the embodiment / s illustrated in the drawings. Accordingly, it should be understood that where features mentioned in the appended claims are followed by reference signs, such signs are included solely for the purpose of enhancing the intelligibility of the claims and are in no way limiting on the scope of the claims.

[0078] The term "comprising" as used in this specification and claims means "consisting at least in part of". When interpreting statements in this specification and claims which include the term "comprising", other features besides the features prefaced by this term in each statement can also be present. Related terms such as "comprise" and "comprised" are to be interpreted in a similar manner.

[0079] Description of Embodiments

[0080] The present invention relates to a method of producing a micro-foamed cheese product and to a micro-foamed cheese product. The micro-foamed cheese product is obtainable in the method of producing a micro-foamed cheese product. The invention further relates to specific uses of the micro-foamed cheese product.

[0081] An extruder 2 for use in the method of producing the micro-foamed cheese product 1 is illustrated in Figure 1, which shows the extruder barrel 21 with an inlet 22, and an outlet 23 with a cooling die 24. The inlet 22 can be considered to be at an inlet end 221, and the outlet 23 at an outlet end 231. The extruder 2 has at least one longitudinally arranged screw 25 in the extruder barrel 21, but as illustrated in Figure 1, the extruder has two longitudinally arranged screws 25. A heating arrangement 26 is configured to heat a content 3 in the extruder barrel 21, and a gas loading zone 27 is located between the inlet 22 and the outlet 23. A gas 28 is provided from a gas supply 271 to enter the extruder barrel 21 at the gas loading zone 27. As illustrated in Figure 1, the cooling die 24 comprises an entrance section 241 at an extruder connection interface 2411 in fluid communication with a cooling die connection interface 2412.

[0082] An example of the extruder 2 is a co-rotating twin-screw extruder 2 (PolyTwin™, BCTL 42 / 32D, Buhler AG, Switzerland @ ETH-SFP Extrusion Platform) with a screw diameter of 42 mm and a length-to-diameter ratio of L / D= 32, and this can be used for a shearing process to cut or break a curd so that parts of it becomes separate. The screws 25 may beoperated by an attached motor 4, which provide a rotatable movement of the screw 25. The screw speed levels may be in the range 200-400 rpm.

[0083] The extruder in Figure 1 includes multiple zones, where, beginning from the inlet end 221, the extruder 2 has a feeding zone Zl, a transition zone Z2, a metering zone Z3 and a texturization zone Z4. The extruder has eight individual barrel segments S, partitioned into three heating sections i.e., S2-S3, S4-S5, and S6-S7-S8, each with the option of temperature set-point regulations, except for the first section SI in the feeding zone. The extruder's individual sections SI to S8 may have a temperature profile in the range of 80°C to 100°C, for example the temperature profile may be set to 80°C at S2, 80°C at S3, 85°C at S4, 85°C at S5, 85°C at S6, 85°C at S7, 85°C at S8.

[0084] The extruder 2, furthermore, may be provided with a flat sheet cooling die 24 (PolyCool 50, Buhler AG, Switzerland), which may be attached to the end of an extruder barrel 21, where a fibrous structure in the material may be formed. The flow domain of the sheet die may have a length of L=1550 mm, width of W=60 mm, and height of 1-1=10 mm. The cooling die 24 in Figure 1 consists of five individual die sections, in which each may have a temperature sensor and a pressure probe attached; the sensors are not shown in Figure 1. The die section closest to the extruder barrel 21 is kept at 48°C and the rest are kept at 45°C.

[0085] The extruder 2 is further provided with a gas supply 271 that is positioned to provide a gas 28 to the gas loading zone 27 between the inlet 22 and the outlet 23 of the extruder barrel 21. The gas loading zone 27 is defined as a zone in which gas is injected or dispersed into the curd 31 that is present in the extruder barrel 21. The gas 28 may be any type of gas, especially O2, N2, and CO2. In an example nitrogen (N2) (Carbagas AG, Switzerland) was applied in mass fractions of 0, 0.05, 0.10, and 0.15% w / w, which is injected into the curd 31 through the barrel segment S7 of the extruder 2. The gas inlet 27 may then be connected to a gas flow meter (not shown), e.g. a Coriolis (CORI-FLOW™ M13, Bronkhorst), which may ensure a steady gas flow with an injection pressure of 10-16 bar.

[0086] An extruder apparatus 2 is applied in the present method, where the extruder 2 is used to create a micro-foamed cheese product 1 by high moisture extrusion cooking. High moisture extrusion cooking is a technology for texturizing various proteins into a product with fibrous texture like e.g. animal meat or meat analogues.Example 1

[0087] To further illustrate the operation of the invention described above, an example is provided. Several Figures show various types of cross-sectional images of the microfoamed cheese product 1 and show the extrudate matrix 11 and the gas bubbles 12. Certain of the Figures indicate the parallel direction α and the perpendicular direction β. Moreover, the Figures also show a non-foamed cheese product 10 that has been made using extrusion but without dispersing of gas in the molten milk protein coagulate 31.

[0088] Renneted and cultured Cagliata curd was used as a milk protein coagulate 31. Cagliata curd is commonly known as an intermediate product for other cheeses, such as Mozzarella, and was manufactured and provided by Taulov Cheese Dairy (Aria Foods, Frederica, Denmark) and used as casein-based material (milk protein coagulate 31) in this study. Raw milk was standardized to a fat-to-protein ratio of 1.2:1, pasteurised for 15 sec at 72 °C, and cooled to 32 °C. Rennet (15 mL per 100 kg cheese milk) and mesophilic starter culture (0.02% w / w) were then added to the cheese milk and set for 35 min. After the setting time, the coagulum was gently stirred for 20 min until pH 6.3 and the whey was drained. The cheese was pre-pressed for 30 min followed by a 4-hour press until pH 5.2. According to the manufacturer, the Cagliata curd contained 47.7% w / w moisture, 27.05% w / w fat, 24.0% w / w protein, and 0.82% w / w calcium. Before extrusion, the curd was stored for 45 days in a refrigerator (3 °C).

[0089] The chemical components of the extrudates 11 were analysed regarding fat, protein, and moisture content. Moisture and fat content were determined by pairing a SMART 6 Moisture & Solids Analyzer (CEM Corporation, United States) with an ORACLE Rapid NMR Fat Analyzer (CEM Corporation, United States). Approximately 2 g of extrudate mass 11 was loaded onto the SMART 6 device. An inbuilt cheese program was selected with a mag power percent of 100, a run time of 10 min, and a temperature of 100 °C. Within 20 seconds after moisture content measurement, the samples were placed in a sealed NMR tube and transferred to the ORACLE device. The Dumas method was used to determine the protein content (ISO 14891; IDF, 2002). The nitrogen content was first determined by weighting 0.250 g of sample into small tubes and then analysed by a Dumas protein analyser (rapid MAX N exceed, Serial no. 19, Elementar Analysensysteme Gmbh, Langenselbold, Germany). Finally, the protein content was estimated by multiplying the total nitrogen content by a factor of 6.38.A pilot-scale intermeshing co-rotating twin-screw extruder 2 (PolyTwin™, BCTL 42 / 32D, Buhler AG, Switzerland @ ETH-SFP Extrusion Platform) with a screw diameter of 42 mm and a length-to-diameter ratio of L / D= 32 was used for the shearing process.

[0090] Nitrogen (N2) (Carbagas AG, Switzerland) in mass fractions of 0, 0.05, 0.10, and 0.15% w / w was injected into the molten milk protein coagulate at the gas loading zone 27 located at barrel section S7. The gas inlet 27 was connected to a Coriolis gas flow meter (CORI -FLOW™ M13, Bronkhorst) to ensure a steady gas flow with an injection pressure of 10-16 bar. Lastly, three different screw speed levels (250, 300, and 350 rpm) were selected for each N2level.

[0091] Ground curd, i.e. the milk protein coagulate 31, was fed into the extruder 2 by a gravimetric twin-screw feeder (K2-ML-D5-KT35, Coperion K-Tron GmbH) at a 20 kg / h feeding rate. The system 2 achieved a steady state after torque levels remained at a plateau from which samples were taken. Each extrusion run was performed in duplicate. Extrudates 11 were vacuum-packed and stored in a refrigerator (3 °C) for 14 days before analysis. The N2-injected extrudates 11 will be referred to as micro-foamed (MF) extrudates and the control (without N2) will be referred to as non-foamed (NF) extrudates. Table 1 shows the composition of the feed material 31 (Cagliata), non-foamed extrudates 10 and microfoamed extrudates 11 (MF005, MF010, and MF015), which comprise four different N2 gas levels (0, 0.05, 0.10, 0.15% w / w) at three different screw speeds (250, 300, and 350 rpm), equivalent to an average shear rate range in the extruder screw channel segments S4-S6 of ca. 80 - 110 1 / s and in the segment S7 (dispersing zone) of ca. 520 - 730 1 / s). Protein, fat, and moisture contents of non-foamed extrudates 10 and micro-foamed extrudates 11were not significantly influenced by the injection of N2 gas (Table 1).Table 1. Composition of the Cagliata feed and extrudates (components are given in percent w / w).

[0092] Screw Sample Protein (% w / w) Fat (% w / w) Moisture (% speed w / w)

[0093] (rpm)

[0094] Cagliata 23.90 ± 0.10 26.69 ± 0.31 45.80 ± 0.01

[0095] 250 NF 23.75a± 0.14 26.35a± 0.27 43.95a± 0.00

[0096] MF005 23.79a± 0.04 26.19a± 0.20 44.66a± 0.00 MF010 23.51a± 0.09 26.28a± 0.12 44.41a± 0.01 MF015 23.69a± 0.12 26.40a± 0.09 44.97a± 0.01 300 NF 23.63a± 0.42 26.66a± 0.12 45.75a± 0.00

[0097] MF005 23.42a± 0.10 26.50a± 0.16 44.41a± 0.00 MF010 23.62a± 0.39 26.35a± 0.21 43.55a± 0.00 MF015 23.52a± 0.11 26.36a± 0.08 43.75a± 0.01 350 NF 23.80a± 0.08 26.25a± 0.11 45.29a± 0.03

[0098] MF005 23.92a± 0.23 26.61a± 0.15 43.23a± 0.00 MF010 23.99a± 0.11 26.57a± 0.09 44.18a± 0.01 MF015 23.67a± 0.04 26.45a± 0.20 43.23a± 0.00a-dEntries marked with different superscripts are significantly different (P <0.05).

[0099] System parameters, such as mass flow rate (mF), specific mechanical energy input (SME), net torque (τnet), the material temperature at the extruder endplate (TEP), and the pressure at the endplate (PEP) were measured as average values over 2 minutes at each sample collection time. The product temperature at the die exit 23 (TeXit) was not measured but estimated based on the setpoint temperature of 45 ± 2 °C.

[0100] Measured extrusion parameters obtained during the extrusion of non-foamed and micro-foamed extrudates are shown in Table 2. The values presented in Table 2 represent average values over a 2-minute collection time of extrudates. The average residence time (RT) varied between 245, 235, and 225 s for 250, 300, and 350 rpm, respectively.Table 2. Recorded system parameters

[0101] Screw Extrudate PEP mFτnetSME TEP Speed (bar) (kg h-1) (Nm) (kJ kg-1) (°C) (rpm)

[0102] 250 NF 15.9 20.0 37.7 177.6 77.4

[0103] MF005 11.1 19.7 32.5 155.6 76.4 MF010 12.0 20.4 33.1 152.4 75.9 MF015 11.5 20.0 32.3 152.7 76.2 300 NF 12.4 19.6 39.6 228.1 68.5

[0104] MF005 16.7 19.7 39.5 227.0 73.5 MF010 15.8 20.0 39.4 223.9 73.6 MF015 11.1 20.3 37.0 206.0 75.8 350 NF 11.9 20.7 37.8 241.3 70.1

[0105] MF005 16.4 19.9 40.0 264.7 73.8 MF010 15.8 20.0 40.2 263.8 76.9 MF015 10.8 19.9 38.9 258.1 72.4

[0106] In Table 2, τnetdenotes the net torque; SME is the specific mechanical energy input; PEP is the pressure at the end-plate; TEP is the temperature at the end-plate, and mFis the mass flow rate of non-foamed and micro-foamed cheese-based extrudates.

[0107] The microstructure of the non-foamed and micro-foamed extrudates were analyzed by confocal laser scanning microscopy (CLSM), as described by Lorenzen et al. 2024, Food Hydrocolloids, 146. https: / / doi.org / 10.1016 / j.foodhyd.2023.109243. A representative image is shown in Figure 2, where panel A shows the Cagliata feed 31 and panel B shows a micro-foamed extrudate 11, MF015 at 300 rpm. Images are taken in the perpendicular direction (+) to the flow with an x63 lens. Fat (red), protein (green), and serum / air pockets (black) are well differentiated. Scale bars are 100 μm. Thin segments of the extrudates 11 with dimensions of approximately 5x5x2 mm were cut parallel and perpendicular to the shear flow direction. Both segments were taken from the interior of the extrudates using a sharp razor blade. The protein phase was stained by 0.01% Fast Green (Sigma-Aldrich) and the fat phase was stained by 0.01% Nile Red (Sigma-Aldrich). The CLSM images were attained with a Leica TCS SP5-X microscope (Leica Microsystems Gmbh, Wetzlar, Germany)at an excitation at 488 nm and 633 nm and emission at 555 to 629 nm and 660 to 710 to directly compare the distributions and microstructures of the fat and protein phases. The microscopy images were investigated in a 1024 x 1024 format under a 63x water immersion objective. The image analyses were performed with Lecia LAS AF software.

[0108] Cheese meltability was accessed by heating the cheese extrudate specimen (diameter = 25 mm; height = 15 mm) on a glass Petri dish with (mass = 34.66 ± 0.26 g; diameter = 80 mm; height = 14 mm) in an oven at 200 °C for 5 minutes. After 5 minutes the melted cheese extrudates were removed from the oven and cooled at room temperature for 30 minutes. A Videometer system analysed images of the melted extrudate samples.

[0109] Meltability is one of the most important functional properties of cheese, especially when cheese is used as a topping ingredient. The meltability of cheese is usually described as the ease and extent to which it flows when heated. When assessing the effect of cooking and meltability of non-foamed 10 and micro-foamed extrudates 11, samples with higher N2 content and sheared at higher screw speeds showed a higher degree of meltability compared to low N2 content and screw speed. Each extrudate was stored for 3 weeks before being heated for 5 min at 200 °C. Upon heating, the non-foamed extrudates maintained their initial circular shape and no crust formation was seen. The micro-foamed extrudates exhibited a more mobile matrix once exposed to heat as seen in the irregular shape of the cheese spread. In addition, a dry, crusty, and brown surface was prominent in extrudates with high N2 content.

[0110] Figure 3 shows macrostructure of non-foamed extrudate (panel A) and micro-foamed extrudate (panel B). Perpendicular cross-sectional view of non-foamed and micro-foamed extrudates are shown in panel C (0, 0.05, 0.10, and 0.15% w / w N2) visualized by a Videometer system. The arrows indicate larger deformed gas bubbles 12 due to bubble coalescence. It can be observed that non-foamed extrudates 10 yielded a darker more yellowish color, whereas the surface texture of micro-foamed extrudates 11 appeared pale and white. The correlation between N2 gas injection and an increase in lightness agrees with those previously reported in the literature for N2-assisted extrusion cooking of pea snacks and extruded micro-foamed soy-based meat analogs. The lighter color observed for micro-foamed extrudates 11 is likely caused by a diffused reflection in the presence of N2 bubbles and micro-pores located at the surface of the extrudates 11. When comparing the fibrous structure between the non-foamed extrudates 10 (Figure 3, panel A) and the micro-foamed extrudates 11 (Figure 3, panel B), it can be observed that the protein strands in the non-foamed extrudates 10 appear denser and are more aligned. The protein strands appear soft, brittle, and porous in the micro-foamed extrudates 11. This softer texture is likely due to the inclusion of gas bubbles 12 acting as voids / holes in the compact casein network structure.

[0111] The cross-sectional view in the perpendicular direction of non-foamed extrudates 10 and micro-foamed extrudates 11 is shown in Figure 3 panel C. As expected, the incorporation of N2 had a distinct influence on the structure of micro-foamed extrudates 11. As seen in Figure 3, panel C, the non-foamed extrudates 10 appear smooth and dense, with no visible disruption in the protein matrix. At a concentration of 0.05% w / w N2, small gaseous entities 12 can be seen in the protein matrix 11. At higher concentrations (> 0.10% w / w N2) larger gas bubble 121 entrapped in the protein matrix 11 starts to appear and a spongier structure can be observed.

[0112] When comparing micro-foamed extrudates 11 at lower N2 gas content (MF005), the formation of larger gas bubbles 12 was to some degree influenced by the screw speed (Figure 3, panel C). However, this trend is not significant and has to be evaluated in the context of porosity development which can also be increased at higher screw speed (rpm). At higher gas concentrations (MF010 and MF015), the formation of larger gas bubbles 12 appears across all screw speed levels but is most prominent at higher screw speeds of 350 rpm (Figure 3, panel C). The growth and coalescence of gas bubbles 12 are likely caused by a combination of increased shear forces acting on the bubble interface due to higher screw speeds and an increase in the injected gas fraction. The latter is not a decisive factor in the gas loading and dispersing zone, because under the locally acting elevated pressure of up to ca. 30 bar in this zone, the gas volume to be dispersed is strongly reduced. However, upon the pressure drop in the die 24, the dispersed gas bubble volume expands about reverse proportional to the decreasing pressure which leads to a thermodynamic instability causing gas bubble coalescence and at the die exit 23 also to some gas loss. This was further confirmed by X-ray microcomputed tomography (X-ray μCT) images of MF005 and MF015 taken at 350 rpm (Figure 4).

[0113] X-ray microcomputed tomography (μCT) was used to evaluate the structural profile of the extrudates. The 3D microstructure images of extrudates 11 were recorded with a μCT scanner (EMPA, Dubendorf, Switzerland) equipped with a 3D cone beam detector with2048 x 2048 pixels (pixel size 0.2 x 0.2 mm). The detector is located 815 mm from the X-ray source. The object was placed 78.1 mm from the X-ray source. Each measurement of a sample consisted of 1500 projections over a 360° rotation. Figure 4 shows representative cross-sectional X-ray microcomputed tomography images of micro-foamed extrudates 11; in panel A 0.05% w / w N2 and panel B 0.15% w / w N2. The light grey area corresponds to the gel network 11 and the dark grey voids correspond to N2 bubbles 12 or pores. Images are taken perpendicular to the flow direction at 350 rpm. Image width: 70 mm.

[0114] The increased fraction of larger pores 12 for micro-foamed extrudates 11 sheared at 300 and 350 rpm containing 0.15% w / w N2 is also reflected in the recorded tendency of lowered PEP and SME.

[0115] In the present study, micro-foamed extrudates 11 with low N2 gas concentration (MF005) displayed a rather uniform dispersion of both small and large gas bubbles 12. Conversely, micro-foamed extrudates 11 with higher concentrations of N2 gas exhibited a more pronounced prevalence of bigger bubbles 12 towards the centre of the extrudates (Figure 4). For micro-foamed extrudates 11, a smooth, non-porous surface was observed (Figure 3, panel B). Rapid loss of N2 to the atmosphere and the formation of a wall slip layer at the extrudate surface in the die likely prevented the accumulation of gas pores at the surface. Hence a smooth surface area can be seen at a macroscopic level.

[0116] The porosity of the micro-foamed extrudates 11 is shown as a function of the N2 dosage in Figure 5, which shows the porosity (%) of micro-foamed (MF005, MF010, and MF015) extrudates 11, which comprise three different N2 gas levels (0.05, 0.10, 0.15% w / w) at three different screw speeds: 250, 300 and 350 rpm. Values obtained for porosity were analyzed based on representative cross-sectional views of each extrudate 11. For microfoamed extrudates 11, the porosity increased with N2 injection (from 8.52 to 43.28%). Similarly, porosity increased with increasing screw speed except for micro-foamed extrudates injected with 0.10% w / w N2. The overall increase in porosity aligns with the observation of a less dense and more open network structure at higher N2 concentrations, as demonstrated in the macroscopic images.

[0117] The mechanical properties of the extrudates 11 were determined with a tensile and a cutting force test in both parallel (II) and perpendicular (+) directions to the shear flow. The anisotropic structure index (As) was determined based on the maximum stretch length(extensibility) measured at rupture to estimate the degree of texturization (anisotropic fiber formation).

[0118] The anisotropic structure indices ASErelated to the extensibility parameter E as defined in Equation 3 of the micro-foamed extrudates 11 are shown as a function of the N2 dosage in Figure 6, which shows ASEof micro-foamed (MF005, MF010, and MF015) extrudates 11, which comprise three different N2 gas levels (0.05, 0.10, 0.15% w / w) at three different screw speeds: 250, 300 and 350 rpm. The extrudates feature a higher extensibility in the parallel direction compared to the perpendicular direction, which suggests that the material has an alignment or orientation along the parallel direction. This is most pronounced at low screw speed of 250 rpm.

[0119] A tensile test was used to quantify the extensibility of the extruded cheese curd 1. The tensile strength test was conducted on a Z010 Zwick universal testing machine (ZwickRoell GmbH & CO. KG, Ulm, Germany) with a load cell of 100 N. For measurements, dog-bone-shaped pieces were cut from the extrudate 11 samples with a length of 50 mm and a width of 6 mm using a tensile bar. The thickness of the samples was 10 mm. The specimen was fixed between two tensile grips at a fixed gap of 20 mm. The samples were taken parallel and perpendicular to the shear flow. The tensile test was conducted at a constant deformation rate with a speed of 1 mm s’1. The tensile force was recorded until the breaking point of the extrudate, and the maximum force (N) and stretch length (mm) were used to evaluate the tensile strength and extensibility of the extrudates, respectively. The maximum length recorded at the maximum tensile strength reflects the extrudate's ability to extend upon deformation until rupture. Results on the extensibility (E) in the unit of millimeters (mm) for extruded cheese 1 samples (NF, MF005, MF010, and MF015) sheared at 250, 300, and 350 rpm are shown in panels A to C, respectively, of Figure 7 as a function of the amount of gas dispersed in the molten milk protein coagulates 31, and panels D to F of Figure 7 show the tensile strengths in the unit of Newton (N) as a function of the amount of gas dispersed in the molten milk protein coagulates 31. For both, the extensibility (E) and the tensile strength (o) there are similar trends of reduction from nonfoamed (NF) to foamed at 0.05% (w / w) N2 (MF005) and foamed at 0.1% (w / w) N2 (MF01) and with increase in the screw speed (rpm) from 250 to 300 to 350 rpm. This is expected to go along with the increase in porosity weakening the extrudate structure under tensile stress.For an increase in screw speed from 250 to 300 to 350 rpm anisotropy for the extensibility (E) between parallel and perpendicular sample cuts are approximately constant for the non-foamed (NF) samples (attention to be taken to the different y-axes scales in Figure 7). This can be interpreted as similar degree of protein strand orientation into the flow direction within the 250 to 350 rpm range.

[0120] As soon as bubbles appear E-anisotropy decreases significantly with rpm at least for the MF005 and MF01 micro-aerated extrudate samples. This is interpreted based on the physically sound effect of smaller disperse gas bubbles generation at higher shear rates (higher rpm). Such smaller bubbles which get less deformed by the acting flow fields acting in die entrance and die, force less protein orientation and stranding in the solidifying extrudate and hence reduced E-anisotropy.

[0121] The o-anisotropy is less to not appearing in the non-foamed samples, however, shows up in the micro-foamed samples, again with some reduction tendency upon screw speed (rpm) increase. The structure-related reasoning is similar to the rpm-dependency of the E-anisotropy used before.

[0122] For highly micro-foamed samples (MF015) trends for screw speed (rpm) impact on (a) extensibility (E) and E-anisotropy as well as tendentially on (b) the tensile strength (s) are changing. It is expected that the increase in porosity (up to 45%) makes the effect of densification of the protein matrix between the gas bubbles dominating the structure weakening effect of the gas bubbles acting as structural interrupts. Consequently, for MF015 the absolute E-values, particularly for the transversally cut extrudate samples recover (increase compared to the MF005 and MF010 samples) and the E-anisotropy stabilizes at a value of about 1.25 to 1.5. A respective influence is also seen for the tensile strength (o) related values of the MF015 samples at the various screw speeds (250-350 rpm), however much less pronounced.

[0123] The cutting force of the extrudate 11 was studied using a Z010 Zwick universal testing machine (ZwickRoell GmbH & CO. KG, Ulm, Germany) equipped with a Warner-Bratzler blade on a 100 N load cell. The cut force measurements were performed at a test speed of 1 mm s’1. Each sample was cut into 22 x 22 mm squares.

[0124] The maximum penetrating force FP (N) required to cut through the samples was used to describe the extrudate's hardness (firmness). For each extrudate 11, at least 6 parallel and perpendicular cuts were measured. All samples were measured at room temperature.Hardness is defined as the resistance of a material to permanent deformation during the application of a load, and higher hardness describes a stronger material that is not easily cut or broken having a "tough" texture. The results of the measured hardness (FP values) can be found in Figure 8, which shows measured hardness in (O) perpendicular direction and (•) parallel direction to the flow direction as a function of the N2 dosage in the unit N for non- (NF) and micro-foamed (MF005, MF010, and MF015) extrudates 11, which comprise four different N2 gas levels (0, 0.05, 0.10, 0.15% w / w) containing three fractions of liquid nitrogen (0.05, 0.10, and 0.15% (w / w)) at three different extruder screw speeds: 250 (A), 300 (B), and 350 (C) rpm. Values represent the mean of six replicates. The higher values for hardness obtained in the parallel cut direction compared to the perpendicular direction correlate with the other measured mechanical properties (extensibility and tensile strength) resulting in similar trends for non- and micro-foamed extrudates.

[0125] The addition of the N2 content significantly decreased the hardness of the extrudates for all extruder screw rpm levels (Figure 8). For non-foamed extrudates (NF) 10, higher screw speed / shear (> 300 rpm) led to increased hardness for transversal cuts. Low N2 extrudates (MF005) exhibited the highest hardness at a screw speed of 350 rpm, while the effect of shear became less prominent at higher N2 concentrations where hardness (FP) approached a force level around 4 (Figure 8).

[0126] At 250 rpm, the hardness continued to decrease significantly from a concentration of 0 to 0.10% w / w N2 (NF < MF005 < MF010), whereas no significant difference was observed between a concentration of 0.10 and 0.15% w / w N2 (MF010 ~ MF015). A similar trend was observed between extrudates 11 sheared at 350 rpm, whereas no significant difference was observed between micro-foamed extrudates 11 sheared at 300 rpm (MF005 ~ MF010 ~ MF015).

[0127] Concerning hardness (FP) anisotropy, the tendency of higher trans-versal cut samples compared with parallel cut ones in hardness was measured for extrudates processed at screw speeds of 250 rpm. With increase in rpm to 300 and 350 the parallel cut samples became equally hard (300 rpm) or tendentially even harder (350 rpm) compared to their transversally cut pendants. A structural effect which would support this trend is the generation of bigger gas bubbles at lower rpm / shear forces. Since bigger bubbles deform more ellipsoidally in the parallel direction than smaller bubbles under similar acting flowstresses, it can be assumed that the cross-sectional areas of bigger gas bubbles in the parallel cut direction are larger than in the transversal cut direction. Accordingly, cutting in the parallel direction would lead to lower hardness. In case this situation reverses tendentially as measured (Figure 8, panel C) for the extrudates processed at 350 rpm, the effect of protein strand formation in the parallel direction between the gas bubbles may overcompensate the "structural interrupt effect" caused by the bubble cross sections.

[0128] Fat droplets / globules and serum pockets may fulfil a similar size-dependent function as "structure break supports" like described before for the gas bubbles.

[0129] Example 2

[0130] This example is meant to demonstrate experimentally the ellipsoidal deformation and orientation of fat droplets, gas bubbles and serum pockets, applying Confocal Laser Scanning Microscopy (CLSM). Images were taken from an emulsion gel sample containing such disperse inclusions and analyse the structural differences in parallel and transversal cut samples in further detail. Related extrusion trials were carried out in a smaller twin screw extruder with 16 mm screw diameter at a screw speed of 300 rpm. The included gas fraction in the investigated curd emulsion gel batch was low and not controlled (gas inclusions by external curd / fat mixing preparation). Serum pockets forming in the emulsion gel were also not controlled but developed by local phase separation. The addition of fat was fixed at ca. 19.1 % (w / w). The anisotropic orientation of the fat droplets, serum pockets, and gas bubbles was visualized from the extruded samples as demonstrated in Figure 9. In the Confocal Laser Scanning Microscope (CLSM) image color differences between stained fat droplets (red), protein matrix (green) and gas bubble / serum pocket inclusions (black) facilitate differentiation of the phases. However even in the grey-level image represented in Figure 9, the significant anisotropically pronounced deformation and orientation of all disperse phases into the parallel (P -) direction compared to the isotropic structure within sample cuts in the perpendicular (a-) direction can be taken (white scale bar length at the lower right corners indicates 50 microns).

[0131] Example 3

[0132] For further comparison of the present method with an extrudate prepared without the injection of a gas a non-micro foamed extrudate 10 was processed at 250 rpm (Trial#1), and two micro-foamed extrudates 11 equally processed at 250 rpm (Trials #2 and #3). Trial #2 was prepared using 0.05% (w / w) island Trial #3 was prepared using 0.1% (w / w) N2 carried out in a the test run series with the 42 mm twin screw extruder system described in Example 1.

[0133] Figure 10 demonstrates the different visual appearance of the extrudate microstructure resulting from cross sectional extrudate cuts in perpendicular direction. Specifically, the bottom panel in Figure 10 shows the visual appearance of non-micro foamed extrudate 10 Trial #1, and the middle and top panels of Figure 10 shows microfoamed cheese products 1 from Trial #2 and Trial #3, respectively, provided using different amounts of gas.

[0134] The extraction of this Example 3 from the mentioned test run series of micro-foamed cheese systems should demonstrate the correlations between (i) the processed gas fractions of 0, 0.05 and 0.1% (w / w) N2, (ii) the resulting porosity of the products, (iii) received mechanical / textural characteristics for hardness (H) and extensibility (E), (iv) the related anisotropy Index / i (for extensibility) and (v) related estimates of consumer relevant sensory characteristics expected, contributing to the biting and chewing experience of the products.

[0135] Table 3: Extrudate properties resulting from exemplary production Trials #1-3

[0136] Trial porosity hardness extensibility anisotropy sensory attributes* Nr. e [%] H [N] (+ / H) E [mm] (+ / H) [ ] H E

[0137] 1 0 6.3 / 5.3 31.2 / 38.1 1.24 0

[0138] 2 10.1 5.5 / 4.3 15.9 / 36.3 2.22 + + ++

[0139] 3 33.2 4.45 / 3.25 10.2 / 27.1 2.51 ++ + ++

[0140]

[0141] (* qualitative, relative sensory characteristics estimates)

[0142] In Table 3, + is the test in perpendicular direction; II is the test in parallel direction; relative sensory scale (hypothetical): -- negative, - semi-negative, o neutral, + semi-positive, ++ positive.

[0143] The physical test parameters and the sensory attributes scaling indicate that with increased degree of micro-foaming (0 to 0.05 to 0.1% w / w N2 dosage) hardness and extensibility are significantly reduced while anisotropy of texture ("fibrousness" in flowdirection) is increased. This would qualitatively describe approaching a softer and fibrous Mozzarella type of cheese.

[0144] Reference signs list

[0145] 1 Micro-foamed foamed cheese product

[0146] 10 Non-foamed foamed cheese product

[0147] 11 Extrudate matrix

[0148] 12 Gas bubbles

[0149] 2 Extruder

[0150] 21 Extruder barrel

[0151] 22 Inlet

[0152] 221 Inlet end

[0153] 23 Outlet

[0154] 231 Outlet end

[0155] 24 Cooling die

[0156] 2411 Extruder connection interface

[0157] 2412 Cooling die connection interface

[0158] 25 Screw

[0159] 26 Heating arrangement

[0160] 27 Gas loading zone

[0161] 271 Gas supply

[0162] 28 Gas

[0163] 3 Content

[0164] 31 Milk protein coagulate

[0165] a Parallel direction

[0166] 6 Perpendicular direction

[0167] S Sections

[0168] Z Zones

Claims

Claims1. A method of producing a micro-foamed cheese product (1), the method comprising the steps of:-providing an extruder (2) having an extruder barrel (21) with an inlet (22), and an outlet (23) with a cooling die (24), at least one longitudinally arranged screw (25) in the extruder barrel (21), a heating arrangement (26) configured to heat a content (3) in the extruder barrel (21), and a gas loading zone (27) between the inlet (22) and the outlet (23);-providing a milk protein coagulate (31) comprising milk protein, water and at least 0.8% (w / w) fat relative to the wet weight of the milk protein coagulate (31) and applying the milk protein coagulate (31) into the inlet (22) of the extruder (2);-rotating the longitudinally arranged screw (25) to create a flow of the milk protein coagulate (31) from the inlet (22) to the outlet (23);-heating the milk protein coagulate (31) to a temperature in the range of 60°C to 140°C to melt the milk protein coagulate (31);-dispersing a gas (28) in the molten milk protein coagulate (31) in the gas loading zone (27); and-cooling the molten milk protein coagulate (31) in the cooling die (24) to obtain the micro-foamed foamed cheese product.

2. The method of producing a micro-foamed cheese product (1) according to claim 1, wherein the gas (28) is selected from N2, N2O, CO2, and SO2.

3. The method of producing a micro-foamed cheese product (1) according to claim 1 or 2, wherein the gas (28) is dispersed in an amount of 0.01% (w / w) to 0.5% (w / w).

4. The method of producing a micro-foamed cheese product (1) according to any one of claims 1 to 3, wherein the longitudinally arranged screw (25) is rotated to provide a shear rate in the range of 501 / s to 1000 1 / s.

5. The method of producing a micro-foamed cheese product (1) according to any one of claims 1 to 4, wherein the cooling die (24) comprises an entrance section (241)wherein the cross-sectional area between an extruder connection interface (2411) and a cooling die connection interface (2412) is reduced to accelerate the flow velocity in the cooling die (24) relative to the flow at the extruder connection interface (2411) by a factor in the range of 2 to 10.

6. The method of producing a micro-foamed cheese product (1) according to any one of claims 1 to 5, wherein the micro-foamed cheese product (1) has a tensile strength of up to 80% of a cheese product subjected to the steps of rotating the longitudinally arranged screw (25), heating the milk protein coagulate (31) and cooling the molten milk protein coagulate (31), but without the step of dispersing a gas (28) in the molten milk protein coagulate (31).

7. The method of producing a micro-foamed cheese product (1) according to any one of claims 1 to 6, wherein the micro-foamed cheese product (1) has a hardness of upto 60% of a cheese product subjected to the steps of rotating the longitudinally arranged screw (25), heating the milk protein coagulate (31) and cooling the molten milk protein coagulate (31), but without the step of dispersing a gas (28) in the molten milk protein coagulate (31).

8. The method of producing a micro-foamed cheese product (1) according to anyone of claims Ito 7, wherein the milk protein coagulate (31) is heated to a temperature in the range of 60°C to 80°C.

9. The method of producing a micro-foamed cheese product (1) according to any one of claims 1 to 8, wherein the molten milk protein coagulate (31) is cooled in the cooling die (24) to a temperature below 60°C.

10. A micro-foamed cheese product (1) comprising an extrudate matrix (11) having milk protein in the range of 30% (w / w) to 98% (w / w) and lipid in the range of 0.8% (w / w) to 70% (w / w) based on the dry weight of micro-foamed cheese product (1), and water in the range of 35% (w / w) to 60% (w / w) relative to the wet weight of the microfoamed cheese product (1), gas bubbles (12) dispersed in the extrudate matrix (11) toprovide a porosity in the range of 5% to 50%, which porosity is defined as the ratio of the volume of the gas bubbles (12) in the extrudate matrix (11) to the total volume of the extrudate matrix (11).

11. The micro-foamed cheese product (1) according to claim 10, wherein the gas bubbles (12) have diameters in the range of 10 pm to 5 mm.

12. The micro-foamed cheese product (1) according to claim 10 or 11 wherein the gas bubbles (12) have a size distribution defined by a Span value determined as Span = (X90.3 - xio.3) / x5o.3 of <2, with X90.3, X10.3, and X50.3 denoting the respective 10%, 50% and 90% percentile related diameters of the volume distribution of the bubble diameters.

13. The micro-foamed cheese product (1) according to any one of claims 10 to 12, wherein the gas bubbles (12) have a parallel dimension and a perpendicular dimension and an aspect ratio of the parallel dimension to the perpendicular dimension of at least 1.2.

14. The micro-foamed cheese product (1) according to any one of claims 10 to 13, wherein the extrudate matrix (11) has a parallel direction (a) and a perpendicular direction (0) and an anisotropic index A of at least 1.5, which anisotropic index A is defined as:xStructure parameter x in parallel directionsStructure parameter x in perpendicular directionwhich Structure parameter is selected from extensibility, compressibility, tensile strength, compression strength and cutting strength of the extrudate matrix (11) in the respective direction.

15. The micro-foamed cheese product (1) according to any one of claims 13 or 14, wherein the aspect ratio of the parallel dimension to the perpendicular dimension is in the range of 1.2 to 3.

16. The micro-foamed cheese product (1) according to any one of claims 14 or 15, wherein the anisotropic index A is in the range of 1.5 to 3.0.

17. The use of a micro-foamed cheese product (1) according to any one of claims 10 to 16 as a component for topping a food item.

18. The use of a micro-foamed cheese product (1) according to any one of claims 10 to 16 as a component for inclusion in a food product matrix.

19. The use of a micro-foamed cheese product (1) according to any one of claims 10 to 16 as a food product for direct consumption or as a component mixed into a salad.

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