EMULSIFICATION OF CASEIN

RELATED APPLICATION

[0001] This application claims priority from Australian Provisional Patent Application No. 2021901454, the entire contents of which are incorporated herein by reference.

FIELD OF THE INVENTION

[0002] This invention relates to emulsification of casein and methods of pasteurising cheese in the presence of emulsified casein to produce a pasteurised cheese emulsion with no, or negligible amounts of additives. Cheese products prepared from such pasteurised cheese are also disclosed.

BACKGROUND OF THE INVENTION

[0003] There is presently a worldwide demand for foods that comprise natural ingredients and are low in additives. This forms part of a general movement towards a preference for higher quality, healthier, better tasting and/or higher purity food. In particular, there is a need for pasteurised cheese products that retain the keeping qualities and convenience of processed cheese, but retain a high cheese content and degree of purity. There is also a desire for pasteurised cheese that preserves the characteristics of the originating cheese, such as varietal flavour or texture.

[0004] Methods of processing cheese and processed cheese products obtained from such processes are well known and date back to the early 20 ^th century when James Kraft, working with the technologists of the Chicago-based Phenix Cheese Company, introduced phosphates to facilitate the processing of Cheddar cheese. Processing cheese to about 85 °C was discovered to extend the keeping qualities of the cheese, eliminating or reducing the occurrence of early spoilage due to drying or growth of yeasts or moulds. The liquid emulsion (sol) resulting from such hot processing provided easy access to fixed weight products and a variety of packaging options. Processed cheese products thus provide advantages such as convenience of packaging and extended shelf life.

[0005] Processed cheese is generally described as a stable oil-in-water emulsion. Emulsifying salts, also known as melting salts, are usually added during cheese pasteurisation to stabilize the cheese emulsion and prevent separation, or syneresis, of the cheese components caused by heating. Emulsifiers can be used to regulate the pH of the cheese, its rheology, moisture content, melting characteristics, and the like. The stability of the processed cheese is determined by the processing time and temperature, together with the emulsifiers used.

[0006] Cheese processors have a large range of emulsifiers at their disposal. Typical emulsifying salts include sodium or potassium salts of polyvalent anions, such as phosphate, hexametaphosphate, pyrophosphate, citrate and tartrate. These salts help disrupt the calcium phosphate-linked protein network present in natural cheese and also adjust the pH. This causes hydration of the caseins present in natural cheese facilitating their interaction with the water and fat phases, thereby producing a homogeneous pasteurised cheese emulsion. The amount and type of emulsifying salt will vary in accordance with the requirements of the type of processed cheese product, however emulsifying salts are typically present in amounts totaling about 1-5% w/w.

[0007] However, the presence of these emulsifying salts may be considered to render the processed cheese less desirable from a health perspective due to the increased sodium or potassium content. Emulsifying salts may also impart a discernible taste and may adversely affect the flavour of the cheese product.

[0008] Pasteurised cheese has evolved over time to include ingredients such as lactose, starches, butter, skim milk powder, whey, buttermilk, vegetable fats or oils, preservatives, stabilizers or emulsifying agents, such as emulsifying salts, in addition to cheese and water. These additional ingredients are often included to improve stability or the handling properties of the cheese mass to facilitate economic commercial production of cheese products.

[0009] It may be necessary to incorporate certain additives to modify texture, viscosity or rheology of the cheese emulsion to facilitate ease of processing or prevent the melting cheese from forming an intractable mass in the processing equipment. This problem is typical during pasteurisation of certain cheese varieties, and can lead to processing problems such as placing strain on processing equipment by fouling stirrers or blocking pipework. These additional ingredients can detract from the perceived purity of the product, and can affect the natural cheese flavour and the characteristics of the parent cheese.

[0010] Moreover, components of cheese such as lactose are known to encourage mould growth, making it necessary to add preservatives such as salt or ascorbic acid to the cheese product. The relatively high level of sodium in the emulsifying salts used during emulsification, together with the sodium already present in the cheese from salt (sodium chloride) used during its manufacture has exacerbated the decline in the popularity of processed cheeses due to a perceived link between salt intake and an increase in heart disease and obesity. This has resulted in a decline in consumption of processed cheese in most countries.

[0011] During pasteurisation of cheese using conventional commercial methods, the viscosity of the melting cheese generally decreases with an increase in temperature, making it capable of being readily pumped at the processing temperature. The processing temperature is generally about 95 °C. At this temperature, the hot cheese sol is stable and is usually packaged at this stage. However, if it is retained in the hot processing environment, generally in the hands of an experienced operator, for a further short dwell-time the product will spontaneously increase in viscosity. This process is known in the art as “creaming”. Creaming not only results in an increase in viscosity, but also in the appearance of a finer texture. From observation, this appears to result from the effect of heat and agitation on the structure of the casein micelles causing division of the micelles into smaller particles and thus providing additional surface area for moisture uptake.

[0012] The creaming process is particularly significant as it determines the properties of not only the melted pasteurised cheese emulsion, but also those of the final product. Creaming results in a viscous mixture with a desirable fine texture. However, the creaming step is a critical phase of cheese processing. The creamed batch can suddenly and spontaneously thicken and become an unworkable mass resulting in the need for immediate termination of the process. This is known as “over creaming”, an occurrence resulting in a solid mass of intractable matter incapable of being poured or pumped. It is believed that the observed over creaming phenomenon may be an extension of the internal processes resulting in creaming of the cheese sol. Thus, over creaming is believed to be due to increased, or total, disruption of the structure of the casein micelles thus presenting increased surface area for absorption of moisture. The occurrence of over creaming is very destructive as the product has no further use. Over creamed product has been observed to act as an efficient emulsifier in subsequent batches of cheese processing, but it has uncontrollable and unpredictable casein emulsifying properties and will adversely affect an entire batch of processed cheese by its addition .

[0013] The majority of contemporary high throughput processing and packaging equipment for preparing cheese products rely on the bulk cheese mass to remain substantially fluid for sufficient periods of time to facilitate procedures such as pumping or pouring. In addition to a need for developing a cheese product free of artificial additives that retains varietal flavour of its parent cheese, it is desirable that the cheese product has enhanced handling properties in the molten form during production. There is also a need for cheese products that resist spoilage and have good shelf stability.

[0014] Methods of liquefying cheese in the absence of emulsifying salts or other emulsifying agents have been reported (WO 2008/122094). However, the processes disclosed therein have the potential drawback in that they rely on the use of a carefully controlled heating regime in combination with controlled incorporation of water to prevent separation of the protein, fat and water components of the cheese through the process of syneresis. These methods have the potential restriction of being most effective for use with well matured Cheddar cheese and also require an extended time for the process to be effective.

[0015] Accordingly, there is a need for improved or alternative methods for producing pasteurised cheese products that address one or more of the problems of present cheese products and methods of producing them.

SUMMARY OF THE INVENTION

[0016] The present invention is predicated, at least in part, on the discovery that casein may be emulsified in water in the presence of a hydrocolloid. A further discovery is that the resulting casein emulsion is itself a useful emulsification agent for casein, thereby providing the potential to access casein emulsions that are substantially free of hydrocolloid. Pasteurisation of cheese in the presence of such casein emulsion may form a cheese emulsion of the desired viscosity and solids content, without occurrence of syneresis, and in the absence of additional emulsifying salts.

[0017] Thus, in one aspect, the present invention provides a method for emulsifying casein comprising combining casein, water and a sufficient amount of hydrocolloid to form a casein emulsion, wherein the casein, water and hydrocolloid together form at least 95% w/w of the emulsion.

[0018] In a second aspect, the present invention provides a method for emulsifying casein comprising the steps of: a) providing a casein extract comprising casein and water; b) adding gelatine to the casein extract provided in step a); and c) heating the casein, water and gelatine to form a casein emulsion, wherein the casein, water and hydrocolloid together form at least 95% w/w of the emulsion.

[0019] In a third aspect, the present invention provides a method for emulsifying casein comprising the steps of: a) preparing a first casein emulsion according to the method of the present invention; b) reserving a portion of the first casein emulsion prepared in step a) as casein rework; and c) combining casein, water and a sufficient amount of the casein rework from step b) to form a second casein emulsion, wherein the casein, water and hydrocolloid together form at least 95% w/w of the second casein emulsion.

[0020] The method according to the third aspect may further comprise a step d) wherein a portion of the second casein emulsion of step c) is reserved as casein rework and combined with casein and water in a sufficient amount to form a third casein emulsion, wherein the casein, water and hydrocolloid together form at least 95% w/w of the third casein emulsion. Step d) may be repeated using a portion of the third or a subsequent casein emulsion as rework in a continuous batch process for a sufficient number of batches to form a fourth or subsequent casein emulsion having a desired amount of hydrocolloid.

[0021] In a further aspect, the present invention provides a method for pasteurising cheese comprising: a) combining cheese and a casein emulsion prepared according to the method of the present invention to form a cheese mixture; b) heating the cheese mixture prepared in step a) to at least 85 °C, wherein the casein emulsion is combined with the cheese in step a) in a sufficient amount such that the water is incorporated into the cheese without syneresis to provide pasteurised cheese in a substantially homogeneous form, and wherein the cheese, casein, water and hydrocolloid together form at least 95% w/w of the pasteurised cheese.

[0022] The present invention also provides pasteurised cheese products prepared according to the method of the present invention. DEFINITIONS

[0023] Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the art to which the invention belongs. Although any methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present invention, preferred methods and materials are described. For the purposes of the present invention, the following terms are defined below.

[0024] The articles “a” and “an” are used herein to refer to one or to more than one (i.e. to at least one) of the grammatical object of the article. By way of example, “an element” means one element or more than one element.

[0025] As used herein, the term “about” means ±10% of the recited value.

[0026] Throughout this specification and the claims that follow, unless the context requires otherwise, the word “comprise”, and variations such as “comprises” and “comprising”, will be understood to imply the inclusion of a stated integer or step or group of integers or steps but not the exclusion of any other integer or step or group of integers or steps.

[0027] The term “consisting of’ means “consisting only of’, that is, including and limited to the integer or step or group of integers or steps, and excluding any other integer or step or group of integers or steps.

[0028] The term “consisting essentially of’ means the inclusion of the stated integer or step or group of integers or steps, but other integer or step or group of integers or steps that do not materially alter or contribute to the working of the invention may also be included.

[0029] When used herein, the term “cheese” refers to cheese made from milk, for example from a cow, sheep, goat or buffalo, especially milk from a cow. Cheese typically comprises fat, protein and water in various proportions according to the variety of the cheese and the milk source. Typically cheese also comprises salts, such as sodium chloride, added during the preparation of cheese. Methods of making cheese are well known in the art, and many varieties of cheese are known. Suitable cheese for use in the processes of the present invention are cheeses of the acid or rennet varieties, especially rennet varieties. Preferably, cheese varieties suitable for use in the methods of the present invention are Cheddar; cottage; cream; Swiss cheese, such as Emmentaler or Gruyere; Gouda; Jarlsberg; or Colby. [0030] In some circumstances, commercial cheese manufacturers may incorporate milk protein concentrate (MPC, also known as milk protein isolate) during the production of cheese. MPC is a substance derived from milk, usually by ultrafiltration of skim milk, which contains greater than 40% by weight milk protein comprising casein and lactalbumin. In some preferred embodiments of the present invention, the cheese does not contain added MPC.

[0031] When used herein, the term “varietal cheese” refers to a cheese variety, other than Cheddar, for example, Gruyere, Emmental, Colby, or Gouda.

[0032] When used herein, the term “Cheddar” refers to a cheese variety prepared by a cheddaring process which involves milling and salting the curd followed by allowing the milled chips to pile randomly in such a manner as to impart a crumbly texture to the cheese. Young Cheddar when referred to herein is a cheese prepared by a cheddaring process that has been aged for about 2-4 months, or 2-3 months, for example about 3 months or 13-14 weeks. Cheeses typically prepared by a cheddaring process include the cheese variety known as Cheddar. Other Cheddar-type cheeses prepared using a cheddaring process include, but are not limited to, varieties known as Gloucester, Derby, Cheshire and Leicester.

[0033] When used herein, the term “syneresis” refers to the process whereby less viscous components of the cheese mass drain from the more viscous components. Typically, syneresis refers to the separation within a cheese mass of a substantial proportion of the water and/or fat from the protein components, for example casein. Syneresis may result in pooling of water or fats.

[0034] When used herein, the term “emulsification” refers to the conversion of “substantially solid” material (e.g., casein or cheese) into a “substantially liquid” emulsion comprising the substance and generally involving incorporation of water. A “substantially solid” material will be understood to exhibit the properties of a solid on a macroscopic level. Cheese comprises water, fat and protein (mainly casein). It will be understood that these different components will have different melting points and heat capacities. It will be appreciated that, at room temperature, certain fats present in a cheese mass may be substantially more liquid in character than the protein therein. Nonetheless, the term “substantially solid” is understood to encompass such composite materials wherein certain components may be considered in isolation to be liquid but, as a whole, the composite material displays the properties of a solid. Likewise, a “substantially liquid” material exhibits the properties of a liquid on a macroscopic level. On a macroscopic level, a liquid readily flows. The term “substantially liquid” may be construed to encompass those composite materials wherein certain components may be considered in isolation to be solid or gaseous but, as a whole, the composite material displays the properties of a liquid. It is understood that the viscosity of a material typically varies as a function of temperature, materials typically becoming less viscous as their temperature increases. It is also known that a change in density of a material often makes a significant contribution to the decrease in viscosity observed in the material as it is heated. As used herein, an example of an “emulsification” process is a macroscopic phase transition of a substantially solid cheese to a substantially liquid cheese emulsion, observable through a decrease in viscosity under conditions of constant volume or constant pressure.

[0035] As used herein, the term “homogenous” refers to a property of a material, for example emulsified casein or cheese, wherein the components therein are uniformly distributed throughout to form a uniform emulsion.

[0036] When used herein, unless otherwise indicated, the term “hydrocolloid” refers to a, generally hydrophilic, substance that yields a gel with water. The hydrocolloid may comprise proteinaceous or polysaccharide components. Examples of proteinaceous hydrocolloid substances include gelatine. Polysaccharide hydrocolloids typically used in food manufacture include alginic acids/alginate, agar, arabinoxylan, carrageenans, carboxymethylcellulose, cellulose, curdlan, gellan, b-glucan and polysaccharide gums such as guar gum, gum arabic, locust bean gum and xanthan gum. In the methods described herein, the hydrocolloid may be hydrated with water prior to combining with a casein/water mixture.

[0037] Hydration may be effected by dispersing the hydrocolloid in water, preferably purified or food grade water. The water may be cold, or it may be at ambient temperature. In some preferred embodiments, the water is hot, for example substantially boiling. In some embodiments, the water is at 50-100 °C, for example 60-100 °C, 75-95 °C, 75-100 °C, 80-95 °C or 90-100 °C. In some embodiments, the hydrocolloid is added to water at ambient temperature and the mixture is heated, for example with stirring, to the desired final temperature to effect hydration of the hydrocolloid. In some examples, the hydrocolloid is hydrated by adding to hot water, for example water at about 90-100 °C. Preferably the hydrocolloid and water mixture is subjected to vigorous stirring to avoid agglomeration.

[0038] When used herein the term “hydrated”, “hydration”, and the like refers to the binding or holding of an amount of water by a hydrocolloid. In some circumstances, it will be appreciated that the hydrated hydrocolloid may form a gel. In some embodiments the formation of a gel is preferred. In some embodiments, for example in the case of hydrated gelatine, a gel may be formed by allowing the hydrated gelatine to stand at about 5 °C. A gel has an advantage of ease of handling and may be dispensed using various techniques, such as pumping. A hydrated hydrocolloid or hydrocolloid gel may be diluted with water prior to combining with cheese.

[0039] The ratio of hydrocolloid to water in a hydrated hydrocolloid can vary enormously and the actual amounts and ratios will depend on the nature of the hydrocolloid and the circumstances such as scale, nature of processing equipment, ratio of water to cheese, required consistency of pasteurised cheese product, etc. In some examples of the processes described herein, the hydrated hydrocolloid is added to a cheese and water mixture. However it will be appreciated that, in some examples, the hydrated hydrocolloid may be first added to water and then subsequently combined with the cheese. In some circumstances, it may be desirable to hydrate the hydrocolloid in the entire amount of water required for a particular process to form the hydrated hydrocolloid, preferably a hydrated hydrocolloid gel, and subsequently combine this with the cheese. It will be appreciated that all variations of combining the cheese, hydrated hydrocolloid and water are encompassed herein.

[0040] In other examples, the ratio of hydrocolloid to water in hydrated hydrocolloid is from about 1:5 or 1:10 to about 1:500, for example 1:20 to 1:250; 1:30 to 1:300; 1:30 to 1:150; 1:30 to 1:100; 1:40 to 1:200; 1:50 to 1:200; 1:75 to 1:150, or about 1:100 by weight. In some embodiments, the ratio of hydrocolloid to water in hydrated hydrocolloid is from about 1:100 to about 3:100 by weight. In some preferred embodiments, the ratio of hydrocolloid to water in hydrated hydrocolloid is from about 1:50 to about 1:10 by weight, for example, about 1:40 to 1:10; 1:30 to 1:10; 1:25 to 1:10; 1:25 to 1:15; or about 1:20 by weight. In some examples, the hydrated hydrocolloid comprises about 0.5% to about 5% hydrocolloid by weight, for example about 0.5% w/w to about 2.5 or 3% w/w; about 0.75% w/w to about 2% w/w, or about 0.75% w/w to about 1.5% w/w. In other examples, the hydrated hydrocolloid comprises about 1% to about 10% hydrocolloid by weight, for example about 2.5% w/w to about 7.5% w/w; about 2% w/w to about 6% w/w, or about 3% w/w to about 5% w/w. In some examples, the ratio of hydrocolloid to water in the hydrated hydrocolloid is 1:99 or 1:100 by weight, or about 1% w/w hydrocolloid in water. In other examples, the ratio of hydrocolloid to water in the hydrated hydrocolloid is about 1:10 to 1:20 by weight, or about 5% w/w to about 10% w/w hydrocolloid in water. In some circumstances, it may be desirable to allow the hydrated hydrocolloid to cool prior to use. In some examples, the hydrated hydrocolloid may form a gel on cooling. In a preferred embodiment the hydrated hydrocolloid is cooled to form a gel prior to use.

[0041] In some embodiments, the hydrocolloid may be allowed to hydrate in a larger amount of water, for example about 1:200 to about 1:1000 hydrocolloid to water, for example about 1:200 to 1:700; 1:250 to 1:600; 1:400 to 1:600 or about 1:500 hydrocolloid to water by weight.

[0042] When used herein, the term “gelatine”, also known as gelatin, refers to a substantially tasteless proteinaceous hydrocolloid derived from partially hydrolysed collagen. It will be appreciated that the properties and composition of gelatine will vary depending on the source(s) of collagen and the processing conditions used in its production. Conventionally, gelatine obtained using acid hydrolysis is referred to as type A gelatine; and that produced by alkaline hydrolysis of collagen is referred to as type-B gelatine. Gelatine may also be produced by enzyme catalysed hydrolysis. Both type- A and type-B gelatines are suitable for use in processing cheese in accordance with the processed described herein. However, in some embodiments of the present methods, gelatine of type-B derived from bovine sources is preferred. The physical characteristics of gelatine are characterised by its Bloom strength value (Schreiber, R. et ah, Gelatine Handbook: Theory and Industrial Practice, Wiley). The amount of gelatine required in the methods described herein will depend on factors such as the ratio of water to cheese, and the strength of the gelatine. The higher the Bloom value, the higher the melting and gelling points of a gel, and the shorter its gelling times. The strength of gelatine is typically between 30-300 g Bloom (or Bloom grams), and is dictated by the chain length and distribution of the polypeptides. Although it is envisaged that any strength of gelatine may be used in the methods of the present invention, one example is gelatine of about 150 Bloom grams. Gelatine is preferably pre-treated by hydrating with water to form a gel prior to incorporation in the cheese/water mixture. In some examples, the ratio of gelatine to water in the hydrated hydrocolloid is 1:99 or 1:100 by weight, or 0.9 to 1.1%, or about 1% gelatine in water. In other examples, the ratio of gelatine to water in the hydrated hydrocolloid is about 1:50 to about 1:10 by weight, e.g., about 1:20 by weight, or 2 to 10%, or about 5% gelatine in water. Typically this hydrated hydrocolloid forms a gel on cooling to about 4-10 °C, for example after cooling at about 5 °C for 2-12 hours, or overnight.

[0043] When used herein, the terms “rework” refers to a casein emulsion (“casein rework”) or a cheese emulsion (“cheese rework”) product left over or retained from a previous manufacturing batch which is reused (reprocessed or reworked) as a blend ingredient in the manufacture of later batches of emulsion. The rework may be obtained from, for example, leftovers removed from heating or processing machinery. Typically, if used, the amount of rework added during the manufacture of a batch of casein or cheese emulsion is less than 20% w/w based on the total weight, for example 5-15% w/w or 5-10% w/w, of total emulsion mass. In some examples, the rework is hot, for example greater than 65 °C. In some examples, the casein and/or cheese emulsion manufacture process forms a continuous process and an aliquot of the hot rework is added back into an earlier stage of the process. The rework may also be cooled prior to use in later batches of emulsion. In some examples, the emulsification of casein and/or cheese forms a continuous process and an aliquot of the cooled rework is added back into an earlier stage of the process.

[0044] As used herein, unless otherwise indicated, the term “additional” when used in relation to emulsifying agent(s) refers to any quantity of one or more emulsifying agents not naturally found in the particular cheese variety that is the subject of the method. For example, pasteurised cheese prepared according the present invention comprises additional casein that is not present in the native cheese.

DESCRIPTION OF THE INVENTION

[0045] The present inventor has found that casein may be emulsified in water in the presence of a small amount of hydrocolloid. Further, the present inventor has discovered that the resulting casein emulsion may be used as an emulsifying rework for subsequent batches of casein emulsion, thereby reducing the amount of hydrocolloid in the casein emulsion. Such casein emulsions may themselves be used as emulsifiers in the pasteurisation of cheese. Pasteurised cheese prepared in accordance with the methods described herein has good shelf life and comprises almost exclusively cheese, additional casein and water, with only a small or negligible amount of hydrocolloid. Further, cheese products prepared according to the process of the present invention may have improved flexibility over certain existing pasteurised cheese products, making them particularly suitable for use in individually wrapped cheese slices or sticks.

[0046] Casein is a family of related phosphoproteins (e.g., aSl-, aS2-, b- and K- casein) commonly found in milk from mammals such as cows, buffalo, goats, sheep, yaks and camels. The amount of casein present depends on the source of the milk. For example, casein comprises approximately 80% of the protein in cow's milk, and is a major component of cheese. Casein is generally isolated on a commercial scale from skim milk, which is commonly produced as a by-product of commercial butter manufacture where the milk fat is removed from whole milk for conversion to butter, leaving the skim milk. The skim milk contains mainly water, milk proteins and lactose. The milk proteins comprise approximately 80% casein, the remainder comprising mainly whey proteins.

[0047] Casein in relatively hydrophobic and is therefore poorly water-soluble. However, the present inventor has found that casein may be emulsified in water in the presence of a small amount of hydrocolloid to form a casein emulsion. Thus, the present invention provides a method for emulsifying casein comprising combining casein, water and a sufficient amount of hydrocolloid to form an emulsion. Preferably, the casein, water and hydrocolloid together form at least 95% w/w, more preferably 99.5% w/w of the casein emulsion.

[0048] Casein used in the present invention may be obtained from any suitable source or method. Typical methods of extracting casein from skim milk on a commercial scale include acid precipitation or rennet precipitation. The present inventor has also found that casein may be obtained from skim milk powder according to the process defined in PCT/AU2021/050889, the entire contents of which are incorporated herein by reference. Generally, the process involves raising the temperature of a mixture of skim milk powder and water to temperatures in excess of 93 °C, followed by cooling, so as to separate components of the skim milk powder, including casein. In particular, on raising the temperature of the mixture of skim milk powder and water (“skim milk mixture”) to a temperature of greater than 93 °C, for example approximately 95°C or greater, the skim milk mixture has been found to increase in viscosity. The present inventor discovered that this heated skim milk mixture, on cooling, can separate into two fractions by virtue of the process of syneresis. Thus, a viscous fraction comprising milk protein, hereinafter referred to as the “casein fraction”, can be separated from a less viscous fraction comprising lactose, hereinafter referred to as the “lactose fraction”. The casein fraction may include whey protein in addition to the casein protein. However, casein will generally be present as the major protein component and comprises at least 75% by weight of the protein present in the casein fraction. Non-protein components such as water and impurities including, but not limited to, one or more of lactose, minerals and riboflavin may be substantially removed from the casein fraction by one or more purification steps, such as washing with water. Water washing of the casein fraction may also remove a portion of the whey protein. Casein extracted according to this method comprises mainly casein and minor amounts of whey proteins. In some embodiments, casein comprises at least 80%, at least 85%, at least 90% or at least 95% by weight of the total protein in the casein fraction.

[0049] Emulsification of casein may be achieved by combining casein, water and a hydrocolloid in any order with mixing, preferably to provide a homogenous mixture. The hydrocolloid used in the present invention may comprise proteinaceous or polysaccharide components, or a combination thereof. In preferred embodiments, the hydrocolloid is a proteinaceous hydrocolloid, such as gelatine. In other preferred embodiments, the hydrocolloid is a polysaccharide hydrocolloid. Examples of suitable hydrocolloids include, but are not limited to, alginic acids/alginate, agar, arabinoxylan, carrageenans, carboxymethylcellulose, cellulose, curdlan, gellan, b-glucan and polysaccharide gums such as guar gum, gum arabic, locust bean gum and xanthan gum.

[0050] In accordance with the present invention, the hydrocolloid may be added in solid form (e.g., as a powder) or, more preferably, hydrated form (e.g., as a gel) to a mixture of casein and water. For example, a portion of the water used in the emulsion may be used to hydrate the hydrocolloid prior to addition to a mixture of casein and the remaining water. By way of example, a hydrocolloid such as gelatine may be hydrated with water at a ratio of about 1 part water to 99 parts water by weight, or 1:100 by weight, more preferably about 1:50 to about 1:10 by weight, or about 1:20 to about 1:10 by weight. Preferably, the hydrocolloid is dissolved in water at about 80-100 °C, for example about 90-100 °C, with stirring. The hot hydrocolloid/water mixture may then be allowed to cool to about 5-10 °C form a gel. The resulting gel may be stored at about 5 °C. The hydrocolloid/water mixture or gel may readily combine with the casein/water mixture. The hydrated hydrocolloid may be at elevated temperature (e.g., above 20 °C) ambient temperature (e.g., 15-20 °C) or it may be cold (e.g., 2- 12 °C, 4-10 °C, or about 5 °C) when it is added to the casein/water mixture.

[0051] In some embodiments, the temperature of the casein/water/hydrocolloid mixture (“casein mixture”) may be raised, for example, to about up to 65 °C, 85 °C or 95 °C, for an amount of time sufficient to form an emulsion (e.g., at least 1 minute, 5 minutes, 10 minutes, 20 minutes, 30 minutes, or more). In some embodiments, the heating rate may be changed during the heating process. For example, the rate of heating may be increased after an initial period of slower temperature increase. This may be accompanied by a reduction in the rate of stirring. The resulting casein emulsion may be used hot or it may be cooled, for example, to ambient temperature prior to use, e.g., as casein rework or in the pasteurisation of cheese. [0052] The temperature of the casein mixture may be raised using any suitable heating means known in the art. For example, the vessel containing the casein mixture may be fitted with a heating jacket containing circulating heated fluid, for example water optionally under pressure, to raise the temperature of the mixture. If desired, the casein mixture may be heated under pressure, or under vacuum using suitable processing equipment known in the art. However, in exemplary embodiments the casein mixture is heated at approximately atmospheric pressure.

[0053] The amount of hydrocolloid used in the casein emulsions of the present invention is preferably the minimum amount required to form an emulsion. In some embodiments, the ratio of casein to hydrocolloid in the casein emulsion described herein is in the range of about 80: 1 to about 10: 1 by weight, or about 70: 1 to about 10: 1 by weight, or about 60:1 to about 50:1 by weight, or about 40:1 to about 10:1 by weight, or about 30:1 to about 10:1, or about 20:1 to about 10:1. In some embodiments, the ratio of casein to hydrocolloid in the casein emulsion is about 30:1 to about 10:1 by weight, preferably about 20:1 to about 10:1 by weight. In other preferred embodiments, the ratio of casein to hydrocolloid in the casein emulsion described herein is in the range of about 200: 1 to about 10: 1 by weight, or about 200: 1 to about 20:1 by weight, or about 200:1 to about 50:1 by weight, or about 150:1 to about 50:1 by weight, or about 100: 1 to about 50: 1. The amount of water used in the casein emulsion may vary depending on a number of factors, for example, the nature and quantity of the hydrocolloid and/or the nature of the extraction technique of casein. Exemplary ratios of casein to water used to prepare the casein emulsion may be in the range of about 10:1 to about 1:10 by weight. In some examples, the ratio of water to casein is from about 5:1 to about 1:5 by weight, for example about 4: 1 to about 1 :4 by weight; or about 3 : 1 to 1 :3 by weight, or 2: 1 to 1 :2 by weight. In some embodiments, the ratio of water to casein is about 1.5:1 to about 1:1.5 by weight, preferably about 1.2:1 to 1:1.2 by weight. In other preferred embodiments, the ratio of casein to water about 1:1 to about 1:2 by weight. However, a skilled person will readily be able to adjust the water content in order to produce a suitable emulsion.

[0054] In some embodiments, the present invention provides casein emulsions consisting essentially of casein, hydrocolloid and water. As discussed above, such emulsions may comprise residual impurities arising from the extraction of casein, such as whey protein or lactose. Thus, a casein emulsion consisting essentially of casein, hydrocolloid and water may comprise about 5% by weight (w/w) or less impurities, e.g., 5% w/w or less, 4% w/w or less, 3% w/w or less, 1% w/w or less or 0.5% w/w or less impurities. Preferably, the casein emulsion contains substantially no impurities (e.g., less than 0.1% w/w). The casein emulsion consisting essentially of casein, hydrocolloid and water may be used as an emulsifier in the pasteurisation of cheese.

[0055] The present inventor has also surprisingly found that casein emulsions according to the present invention can be used as an emulsifying rework for subsequent batches of casein emulsion. Hence, a portion of casein emulsion may be incorporated into a subsequent casein emulsification batch to effect emulsification of casein without the requirement to add additional hydrocolloid or other emulsifying agent. It will be appreciated that this procedure dilutes the amount of hydrocolloid present and thus reduces the amount of hydrocolloid present in the subsequent batch of casein emulsion to considerably less than that of the parent batch. Thus, when the casein emulsion is used as casein rework, the small level of hydrocolloid present in the emulsion can be effectively eliminated by progressive dilution in subsequent batches of emulsion, or as part of a continuous process. Thus, a high purity casein emulsion can obtained, consisting essentially of casein and water. Advantageously, preparation of casein emulsion in a continuous batch process effectively allows casein to remain emulsified in water in the absence of hydrocolloid, or trace amounts thereof.

[0056] Thus, the present invention also provides a process for emulsifying casein comprising the steps of: a) preparing a first casein emulsion according to the method described herein; b) reserving a portion of the first casein emulsion prepared in step a) as casein rework; and c) combining casein, water and a sufficient amount of the casein rework from step b) to form a second casein emulsion, wherein the casein, water and hydrocolloid together form at least 95% w/w, preferably 99.5% w/w, of the second casein emulsion.

[0057] Formation of the first casein emulsion may be performed according to the process described herein. Formation of the second casein emulsion may be performed according to a similar process, wherein the hydrocolloid component is replaced with casein rework from the first casein emulsion. For example, a small amount of casein rework (e.g., about 4-10% by weight) may be added to a mixture of casein and water. The rework may be added to the casein/water mixture at ambient temperature or at a raised temperature, for example, up to 65 °C, 85 °C or 95 °C. The casein/water/rework mass may be heated to the desired temperature over a period of time sufficient to form a second casein emulsion (at least 1 minute, 5 minutes, 10 minutes, 20 minutes, 30 minutes, or more).

[0058] Rework obtained from second and subsequent batches of casein emulsion may be used as an emulsifier in further batches of casein emulsion. For example, aliquots of casein emulsion (casein rework) may be used as an emulsifier in a continuous batch process for a sufficient number of batches to form a casein emulsion having the desired amount of hydrocolloid. Thus, it will be understood that the use of casein rework as an emulsifier results in a dilution effect with regard to the amount of hydrocolloid present in subsequent batches of casein emulsion. Using this methodology, the amount of hydrocolloid present in a “second generation” casein emulsion batch may be reduced to, for example, less than 0.05% by weight of total casein emulsion. The second casein emulsion may also be used directly in the pasteurisation of cheese, or it may be used as further casein rework, for example, in a continuous batch process to produce a casein emulsion having substantially no hydrocolloid. For example, a “third generation” casein emulsion may have hydrocolloid present in less than 0.005% by weight. Typically, casein rework emulsions may comprise 4-10% by weight of the total casein emulsion mass at the commencement of the subsequent emulsion batch, for example, in a ratio of casein rework to total casein emulsion of about 1:25 to about 1:10, or about 1:20 to about 1:10. The use of casein rework in accordance with the present invention thus has the effect of reducing even further the amount of hydrocolloid present in the casein emulsion. First, second, third and subsequent batches/generations of casein emulsion may be used as emulsifiers in the pasteurisation of cheese, thus potentially providing access to a pasteurised cheese product consisting essentially of cheese and water.

[0059] Preferably, the casein rework process will be repeated for a suitable number of batches or “generations” such that the amount of hydrocolloid present in cheese pasteurised using the casein emulsion will be below the limit required for detection and or reporting in the final cheese product. A skilled person will readily be able to calculate the amount of hydrocolloid present in a casein emulsion and/or pasteurised cheese emulsion prepared according to the methods described herein based on the quantities of casein, water and hydrocolloid (and cheese, where appropriate) used in each processing step. Preferably, the casein emulsion consists essentially of casein and water, for example, the amount of hydrocolloid present in the emulsion is less than 0.1% weight, preferably less than 0.05% by weight. In particularly preferred embodiments, casein and water make up substantially 100% of the casein emulsion.

[0060] Advantageously, the use of a casein emulsion prepared according to the methods described herein as an emulsifying agent in the pasteurisation of cheese eliminates (or at least ameliorates) the need for addition of emulsifying salts during the pasteurisation process. As casein is already a major component of cheese, use of the casein emulsions described herein result in a pasteurised cheese comprising additional casein, water and only a small or preferably negligible amount of hydrocolloid. Further, the increased casein content of the pasteurised cheese may provide certain health benefits. For example, casein is a nutritional source of amino acids, calcium and phosphorus in the diet. Casein is sensitive to acid conditions and, when consumed, it forms a gel or clot in the stomach which provides a sustained slow release of amino acids into the bloodstream, making it useful as a protein supplement in the diet.

[0061] Further, the casein emulsions described herein may be stored prior to further use without significant spoilage. For example, the casein emulsions may be stable at room temperature or cooler (e.g., 5-10 °C, preferably 5 °C) for greater than one month, and more preferably for greater than 12 months. Preferably the products of the methods described herein are stable for a period of greater than 12 months at a temperature of less than 10 °C, preferably less than 5 °C.

[0062] Cheese may be effectively pasteurised according to the methods described in PCT/AU2020/051386, the entire contents of which are incorporated herein by reference, wherein the emulsifier used therein (a hydrated hydrocolloid) is replaced with the casein emulsions according to the present invention. Accordingly, the present invention also provides a method for pasteurising cheese comprising: a) combining cheese and a casein emulsion prepared according a method described herein to form a cheese mixture; b) heating the cheese mixture prepared in step a) to at least 85 °C, wherein the casein emulsion is combined with the cheese in step a) in a sufficient amount such that the water is incorporated into the cheese without syneresis to provide pasteurised cheese in a substantially homogeneous form, and

[0063] Preferably, the cheese, additional casein, water and hydrocolloid together form at least 95% w/w, more preferably at least 99.5% w/w of the pasteurised cheese prepared according the methods described herein. More preferably, the cheese, additional casein and water together form at least 99.5% w/w of the pasteurised cheese, or substantially 100% w/w of the pasteurised cheese product. The amount of casein emulsion required during the pasteurisation process will depend on several factors, such as the variety of the cheese(s) to be pasteurised and the amount of casein and/or hydrocolloid in the casein emulsion. The skilled person will readily be able to determine the amount of casein emulsion required in accordance with the circumstances. In some embodiments, the ratio of additional casein to (solid) cheese ingredient is from about 1:15 to about 1:30 by weight, for example about 1:20 to about 1:30, or about 1:15 to about 1:20 by weight. Cheese products prepared using the process described herein (i.e., pasteurised using casein emulsion) may be more flexible than a comparable cheese product prepared using a hydrated hydrocolloid emulsifier (which tend to be more brittle).

[0064] Pasteurised cheese prepared according to the present method is a hot, stable emulsion with good handling properties. This hot cheese emulsion is capable of being pumped or poured, and is thus compatible with food processing equipment conventionally used in the preparation of pasteurised cheese products. Furthermore, there is no requirement for additional ingredients. Accordingly, pasteurised cheese products wherein cheese, additional casein, water and hydrocolloid make up at least 95% w/w, and preferably at least 99% w/w, 99.5% w/w, 99.9% w/w, or substantially 100% w/w of the pasteurised cheese product by weight, may be prepared. Furthermore, casein emulsions prepared according to the present invention provide the potential for pasteurised cheese comprising a negligible amount of hydrocolloid to be prepared, i.e., consisting essentially of cheese, additional casein and water. For example cheese, casein and water, may make up at least 95% w/w, and preferably at least 99% w/w, 99.5% w/w, 99.9% w/w, or substantially 100% w/w of the cheese products prepared according the methods described herein.

[0065] The amount of casein added during the pasteurisation process as part of the casein emulsion may affect the rheology and texture of the pasteurised cheese. Thus, the casein content of the emulsion may be adjusted in order to provide the desired properties of the pasteurised cheese product. Additional aliquots of casein may also be added during the pasteurisation process if desired to alter the rheology of the pasteurised cheese.

[0066] It will be appreciated that the casein emulsion may be sufficiently dilute, or may comprise sufficient unbound water, to facilitate the preparation of pasteurised cheese as an emulsion of the required consistency. Thus, depending on the circumstances, additional water may not be necessary in the pasteurisation process. Accordingly, the methods of pasteurising cheese according to the present invention may comprise heating cheese to at least 85 °C in the presence of a sufficient amount of casein emulsion such that water is incorporated into the cheese without syneresis to provide pasteurised cheese in a substantially homogeneous form, the cheese, water and hydrocolloid together forming at least 95% w/w, preferably at least 99.5% w/w, of the pasteurised cheese.

[0067] Pasteurised cheese prepared according the present methods may be subjected to further processing steps to enable its conversion to the desired pasteurised cheese product. For example, it may be subjected to further processing steps including heating to a higher temperature to effect sterilization. The viscosity can be increased by the injection of raw cheese of the same or different variety directly into the hot mass over a period of time that does not allow the temperature of the sol to fall below about 75 °C to about 80 °C. Additional cheese can also be incorporated into the hot emulsified cheese liquid without destabilizing or otherwise adversely affecting the emulsion. This provides access to pasteurised cheese with a high solids content which, on cooling, affords a pasteurised cheese product that may be provided in block form, or may be sliced or otherwise cut into portions.

[0068] Pasteurised cheese prepared according the present methods may be allowed to cool to provide a pasteurised cheese product, for example, a spreadable gel or paste, or a shaped cheese product such as cheese slices or sticks. The resulting pasteurised cheese products comprises cheese, additional casein and water, preferably with the amount of hydrocolloid present comprising less than 0.1% w/w, or less than 0.05% w/w, or less than 0.01% w/w, or less than 0.005% w/w, or less than 0.001% w/w, or less of the total mass of the cheese product. The pasteurised cheese product may be substantially free of any other additives. Such cheese products may have excellent keeping qualities and long shelf life. The very small amount of hydrocolloid present (if any) does not adversely affect the texture or flavour of the pasteurised cheese emulsion. The resulting pasteurised cheese products have no added emulsifying salts, and therefore have a lower salt content than conventionally processed cheese. Furthermore, the products are of high purity with respect to the originating cheese, and substantially retain its characteristic flavour, while also having the desired flexibility to produce products such as individually packages cheese slices or sticks.

[0069] The pasteurised cheese produced by the methods of the invention can itself also act as an emulsifying agent for subsequent batches of cheese pasteurisation. Hence, a portion of the pasteurised cheese may be incorporated into a subsequent cheese pasteurisation batch to effect emulsification of the cheese without the requirement to include additional casein emulsion or other emulsifying agent according to the methods described in PCT/AU2020/051386. In some forms, the pasteurised cheese provides an emulsifying cheese rework with predictable and consistent emulsifying properties. These properties are advantageous when compared to “over-creamed” processed cheese which, although possessing powerful emulsifying properties, its uncontrollable nature makes it impractical to use in a commercial setting It will be appreciated that this procedure also dilutes the amount of hydrocolloid present (if any) in subsequent batches of pasteurised cheese.

[0070] Although rework reserved from a previous batch of cheese pasteurisation may be used to emulsify subsequent batches, it will be understood that production of pasteurised cheese on a commercial scale is frequently carried out using a continuous process. In such circumstances, it will be appreciated that aliquots of pasteurised, emulsified hot cheese (rework) may be withdrawn from a later stage and re-introduced into an earlier stage of the continuous process to assist emulsification during pasteurisation.

[0071] The inventor has discovered that a casein emulsion as described herein may be utilised to aid emulsification or stabilisation of a cheese and water mixture during pasteurisation, thus preventing syneresis. This negates (or at least ameliorates) the need for other emulsifying agents or other additives. It also avoids the need for strict adherence to factors such as temperature and heating rate, amount of water and rate of water addition. Thus, in accordance with the methods described herein, cheese can be pasteurised in the absence of additional emulsifying salts or melting salts to provide a stable, substantially homogeneous cheese emulsion. The pasteurised cheese products have excellent shelf life and their rheology may be controlled to produce flexible cheese products, such as individually packages cheese slices and sticks. Furthermore, there is no requirement for additional ingredients such as lactose, starch, butter, skim milk powder, casein, whey, buttermilk, preservatives, stabilizers, or other emulsifying agents. The pasteurised cheese thus retains the characteristic flavour of the parent cheese.

[0072] Thus the pasteurised cheese products obtained in accordance with the methods described herein comprise cheese, additional casein water and a small (or negligible) amount of hydrocolloid. Typically, in the pasteurised cheese products thus formed, the cheese, additional casein, water and hydrocolloid together comprise at least 95% w/w of the cheese product. In some examples, the cheese, water and hydrocolloid comprise at least 96% w/w, at least 97% w/w, at least 98% w/w, at least 99% w/w, or at least 99.5% w/w or 99.9% w/w, or substantially 100% of the pasteurised cheese product thus formed. In some embodiments, the cheese, additional casein and water together comprise at least 95% w/w of the cheese product. In some examples, the cheese, additional casein and water comprise at least 96% w/w, at least 97% w/w, at least 98% w/w, at least 99% w/w, or at least 99.5% w/w or 99.9% w/w, or substantially 100% of the pasteurised cheese product.

[0073] These pasteurised cheese products have reduced sodium and/or potassium content when compared with conventional processed cheese products, and therefore may be considered as a healthier alternative. Furthermore, the hydrocolloid does not contribute significantly to the overall flavour of the product and, as additional emulsifying salts are not present, there is an absence of the characteristic salty or bitter taste normally associated with the presence of emulsifying salts. The pasteurised cheese thus is considered to have an improved taste, more characteristic of the original cheese variety, and is lower in sodium than conventional processed cheese made using emulsifying salts.

[0074] The general methods described herein are applicable to pasteurisation of many varieties of cheese. It will be appreciated that different varieties of cheese vary in their composition. Characteristics of the cheese variety, such as the moisture content, fat content or the casein content, may have a marked effect on the viscosity and rheology of the cheese during processing and the texture and properties of the final processed cheese product. The skilled artisan will appreciate that adaptation of the processes may be necessary in view of the physical properties of the cheese.

[0075] The inclusion of variable quantities of water into the cheese mass in the methods of the present invention alters the composition and physical characteristics of the final product. In the methods of the present invention, cheese is combined and heated with the required amount of water to produce a pasteurised cheese product of the required viscosity and solids content. Addition of water assists in reducing the viscosity of the hot and/or cooled pasteurised cheese product. Preferably, water is added at the commencement of the pasteurisation process. In some embodiments, the water may be comprised only in the casein emulsion. However, additional water may also be introduced during the heating process, for example to reduce viscosity of the cheese mass. Similarly, cheese may be added during the heating process to increase viscosity and/or solids content of the pasteurised cheese if required. The amount of water required will depend on several factors, for example the composition and nature of the cheese variety, including its water content. It will be appreciated that certain cheese varieties, such as cottage cheese, include additional water which is not incorporated in the cheese mass in its original form. When used in processes herein, it may thus be unnecessary to include additional water as the emulsification process may utilize the unincorporated water from the originating cheese. The temperature to which the cheese is to be heated and the desired final physical properties of the cooled product will also be factors in determining the amount of water to be added.

[0076] In the methods of the present invention, cheese is combined and heated with the required amount of water to produce a pasteurised cheese product of the required viscosity and solids content. Typically, the ratio of water to cheese is between about 10:1 to about 1:10 by weight. In some examples, the ratio of water to cheese is from about 1:1 to about 1:5 by weight, for example about 1:2 to about 1:4, or about 1:2 to about 1:3, or about 1:1.5 to about 1:3 by weight. In some embodiments, the ratio of water to cheese is about 1:2 by weight. In some embodiments, typically the pasteurised cheese has a viscosity of about 5-20 mPa at approximately 80 °C and a solids content of approximately 45% w/w cheese solids.

[0077] The casein emulsion, cheese and, optionally, water may be combined in any order, however it is preferable that the cheese is first added to water and then the casein emulsion is added to the stirred cheese/water mixture. In some embodiments, the cheese is cold, for example about 5-15 °C. Preferably the cheese is finely divided, for example minced or chopped, prior to combining with the water. In some embodiments, the water is suitably cold or ambient, for example 5-15 °C or 15-25 °C.

[0078] It will be understood by those skilled in the art that pasteurisation of cheese occurs by raising the temperature of the cheese. In some embodiments, the cheese/casein emulsion/water mixture (“cheese mixture”) is raised to at least 85 °C, and preferably about 95 °C. Preferably casein emulsion is added to the stirred cheese/water mixture which is suitably at ambient temperature, for example 15-20 °C. The cheese mixture is then raised to a temperature of at least 85 °C or 95 °C with stirring. In some preferred embodiments, and is held for at least 10, 15, 20 or 30 seconds, or more, to effect pasteurisation. In some preferred embodiments, the cheese mixture is heated to the desired temperature over a period of from about 30-120 seconds, for example 45-90 seconds or 60-90 seconds. In some embodiments, the heating rate may be changed during the heating process. For example, the rate of heating may be increased after an initial period of slower temperature increase. This may be accompanied by a reduction in the rate of stirring. In some aspects of the methods of the invention, it may be desirable to raise the temperature of the cheese mixture to a higher temperature, for example, to reduce the viscosity of the cheese mixture for handling purposes, or to prevent it cooling to too low a temperature during handling.

[0079] In some aspects, the cheese mixture may be heated to a temperature from about 85 °C to about 120 °C or about 95 to about 120 °C, for example 85-90 °C, 85-95 °C, 85- 100 °C, 95-100 °C, 85-120 °C, 80-110 °C or 95-100 °C. In some circumstances, it may be desirable to heat the cheese mixture to a temperature of greater than 120 °C, such as about 140 °C or about 145 °C, so as to effect sterilisation of the cheese mass and ensure destruction of certain pathogens such as Clostridium spp.

[0080] In some preferred aspects, the cheese mixture is heated to about 85 °C, about 90 °C or about 95 °C. In some preferred embodiments, the pasteurised cheese emulsion is generally processed to about 95 °C. This processing temperature provides pasteurised cheese with improved keeping qualities and extended lifetime. This processing is generally performed using a combination of heating, mechanical stirring and/or cutting. In some examples, the pasteurised cheese mixture is raised to about 95 °C, where the molten cheese sol is usually packaged immediately. This is common manufacturing practice in some countries.

[0081] It will be appreciated that the viscosity of the melted pasteurised cheese generally decreases with increasing temperature. Casein micelles are believed to control the texture of the cheese mixture by expansion, contraction or dispersion. In some circumstances it is desirable to continue to heat (or cook) the cheese mixture for a period of time at a selected temperature, or temperature range, to effect gelling, or creaming, of the emulsified cheese. The concept of creaming is well known in the art and is commonly used by processed cheese manufacturers. The physical effect of creaming is well recognised. Cooking causes thickening of the pasteurised cheese mixture with increased viscosity. The mixture develops a fine, smooth texture on cooling. This influences the textural properties and firmness of the final cheese product.

[0082] The physicochemical mechanisms of creaming are not clearly understood. The viscosity change in melted processed cheese is believed to be due to changes in the structure of the casein. During emulsification, casein particles, or micelles, are believed to be dispersed as smaller, more soluble casein sub-micelles. The sub-micelles have increased surface area and are more readily hydrated. It is believed that the creaming process affects the casein network structure and the size of the milk fat globules. It is postulated that creaming restructures or converts the sub-micelles into an insoluble casein network which increases the viscosity of the hot, pasteurised cheese with resultant effects on the physical properties of the final cheese product (see, for example, Y. Kawasaki, Milchwissenschaft, 2008, 63(2): 149-152 and references therein).

[0083] Typically, creaming is carried out at temperatures of 80-120 °C, for example 80-110 °C, 85-110 °C, 85-100 °C, 85-95 °C, 90-110 °C, 90-100 °C, 95-105 °C, 95-100 °C or about 85 °C, about 90 °C, about 95 °C or about 100 °C. In some preferred examples, the creaming process is carried out with stirring or mechanical cutting or agitation. In some examples, the pasteurised cheese mixture is creamed for about 10 minutes; about 5, 4, 3, or 2 minutes; or about 1 minute. In some examples, the pasteurised cheese mixture is creamed for about 30-60 seconds, or about 20-30 seconds.

[0084] The phenomenon of over-creaming is well known in the art, and occurs when the pasteurised cheese spontaneously gels and forms an intractable solid, often due to over heating or over-cooking due to extended creaming times or excess heat. A feature of so-called “over-creamed” processed cheese is its powerful, but uncontrollable, casein emulsifying properties. However, while the over-creamed product can act as a powerful emulsifying agent, it cannot be used as rework with any level of success as it can cause sudden gelling or solidification of the pasteurised cheese. This unpredictable nature makes further employment impractical. The solid is deemed unworkable and generally has to be discarded. The pH of the over-creamed pasteurised cheese is not observed to be increased over that of the creamed sol. The major physical change in over-creamed pasteurised cheese is considered to be the uptake of substantially all available moisture. However, when pasteurised emulsified cheese is prepared using a casein emulsion as an emulsifier in accordance with the present invention, the resulting emulsified cheese has a notably fine texture. Moreover, on creaming, the emulsified cheese shows little tendency to over-cream.

[0085] The pasteurised cheese emulsion is typically heated to its desired final temperature and then may be allowed to cool to the required temperature for further processing or packaging. The rate of increase in temperature may remain the same throughout the pasteurisation process, or may be varied. In some embodiments, the mixture is heated initially at a lower rate, and then the rate of heating is increased. For example, the cheese mixture may be initially heated at such a rate so as to increase its temperature from ambient temperature to 50-70 °C, for example approximately 50 °C, over 40-60 seconds to effect emulsification. The heating rate may then be increased to raise the temperature at a more rapid rate to effect pasteurisation or sterilisation, as required, or to improve handling characteristics by reducing viscosity of the emulsified cheese.

[0086] It should be noted that the present methods are not limited in application to only one cheese variety at a time. Under certain circumstances it may be beneficial or convenient to use mixtures of two or more cheese varieties in various proportions. The blending of cheese mixtures or varieties may preferably occur prior to subjecting the mixture to the methods of the present invention, but it may also occur during any one of the methods of the present invention and it may occur after any one of the methods of the present invention.

[0087] It will be appreciated that the amount of cheese solids present in the final product may be increased by removal of water from the cheese mass. Accordingly, in another embodiment, the methods of the present invention may be expanded to include the step of subjecting the liquid emulsified cheese mass to conditions of such temperature, pressure and/or humidity as to effect evaporation of at least a portion of the water in that liquid mass. The cheese mass may also be subjected to separately, sequentially or simultaneously cooling it to near room temperature and evaporating a portion of the water to afford a solid cheese product. Additionally, finely dividing the mass with subsequent evaporation of a substantial proportion of water can afford a solid cheese product in the form of a cheese powder.

[0088] Preferably the process of raising the temperature of the cheese, hydrated hydrocolloid and water mixture to effect emulsification is carried out with mixing. The mixing may be enhanced by fine division of the cheese using, for example, mincing, milling, macerating or grinding. If desired, further aliquots of casein may be added to the cheese at this stage. Suitable vessels and equipment for pasteurisation of cheese are well known in the field of food and cheese processing. In one embodiment, the cheese, water and hydrocolloid are mixed together in a vessel fitted with sharpened rotatable blades. Preferably the blades are adapted to rotate at variable speed. Alternatively, the cheese, casein emulsion and water are brought into contact in a vessel with simultaneous thorough mixing using an impeller. Preferably the impeller can rotate at a variable speed. Preferably the cheese, casein emulsion and water are mixed under conditions such that the water is incorporated completely into the cheese mass. [0089] The temperature of the cheese mixture may be raised using any suitable heating means known in the art. For example, the vessel containing the cheese mixture may be fitted with a heating jacket containing circulating heated fluid, for example water optionally under pressure, to raise the temperature of the mixture. If desired, the cheese mixture may be heated under pressure, or under vacuum using suitable processing equipment known in the art. However, in exemplary embodiments the cheese mixture is heated at approximately atmospheric pressure.

[0090] The methods described herein are predicated in part on the absence or reliance on the use of additional emulsifying agents, for example, emulsifying or melting salts such citrate, tartrate, phosphate or phosphonate salts of sodium or potassium. The skilled person will understand that certain varieties of cheese may naturally comprise small quantities of salts, such as sodium citrate. Accordingly, the pasteurised cheese prepared according to the methods described herein is considered to be free of additional emulsifying salts.

[0091] It will be appreciated that the pasteurised cheese prepared in accordance with the present invention will have a high cheese content and, being substantially free of additives such as emulsifying salts or other ingredients, the cheese product will retain characteristics of the flavour of the original cheese. Added casein does not contribute significantly to the overall flavour of the product. Accordingly, cheese pasteurised in accordance with the present methods will retain much of the varietal flavour of the original cheese and may also have improved flexibility. It is envisaged that the pasteurised cheeses will be readily consumed and enjoyed without the need for any additional ingredients or flavourings. However, the present pasteurisation methods lend themselves to incorporation of flavouring agents, particularly when the cheese is in a less viscous form, for example when it is at an elevated temperature. Examples of flavouring agents include herbs, spices, fruits, berries, nuts and vegetables. Other examples of flavouring agents include meat products.

[0092] Following pasteurisation of the cheese, the resulting cheese mass may be subjected to one or more additional process steps. For example, the hot cheese mass may be heated to a higher temperature, such as 80-90 °C, to allow the cheese to be poured to form a sheet of pasteurised cheese which can then be cut, for example into squares, and wrapped to form individually wrapped cheese slices. In some embodiments, the temperature of the cheese mass may be raised to greater than 100 °C or 120 °C to effect sterilization of the cheese mass. In some embodiments, the methods of the present invention may include a step of cooling the hot liquid cheese mass to approximately room temperature, with or without mixing. The cooled product may take the form of a spreadable gel, or may be in the form of a more viscous paste, depending on the amount of water present in the mixture and the nature and characteristics of the cheese used. A spreadable gel is a semi-liquid product which does not fracture on division but rather may be spread on a surface, such as a paste.

[0093] In another embodiment, the methods of the present invention may be expanded to include a step of subjecting the pasteurised cheese mass to conditions of such temperature, pressure and/or humidity as to effect evaporation of a substantial proportion of the water in that liquid mass. In some embodiments, the pasteurised cheese mass may be subjected to spray drying, for example at about 45% solids.

[0094] Without wishing to be bound by theory it is believed that modifying such conditions provides control over the amount of moisture absorbed by the protein within the cheese mass. The product of such a method may take the form of a block or slice of substantially solid cheese. Further reduction of moisture may be used to form a biscuit. In another embodiment, the method of the present invention may be elaborated by incorporating the steps of finely dividing the hot liquid cheese mass before subjecting it to conditions under which evaporation of some of its moisture may occur. As used herein, the term “finely dividing” refers to methods whereby the mass is divided into particles such as droplets. In particular, the cheese mass may be passed through a nozzle, creating such shear as to separate it into discrete droplets of pre-determined and desired size. The finely divided material may be subjected to conditions of such temperature, pressure and/or humidity as to effect evaporation of a substantial proportion of the water within that finely divided material. This evaporation may occur while the material is in a suspended state and/or following contact with a surface. In any event, the step of evaporation may, or may not, follow a cooling step, whereby the hot liquid mass is cooled to a pre-determined temperature.

[0095] In some embodiments, where the method includes adding additional cheese to the emulsified pasteurised cheese mixture during or after heating to increase the amount of solid present and hence the viscosity, the cooled product will be more solid in form and texture. In these embodiments it will be appreciated that the product may take the form of a block or a slice of substantially solid cheese, or a biscuit or cheese powder. The ability to add cheese to a hot emulsified pasteurised cheese prepared according to methods described herein without any adverse effect on the physical properties of the cheese mass has the advantageous effect of raising the solids content of the pasteurised cheese mass to, for example, greater than 50% w/w cheese solids. Thus, in another aspect, this provides a pasteurised cheese product of greater viscosity and physical properties which, on cooling to room temperature or below, provides a cheese product that is suitable for slicing or otherwise shaping by cutting, or for forming blocks of pasteurised cheese.

[0096] Owing to their improved flexibility, emulsified pasteurised cheese mixtures provided herein may be particularly useful in the preparation of individually packaged cheese slices or sticks. Thus, in some embodiments, the methods of the invention may be elaborated to provide pasteurised cheese slices or sticks, preferably pasteurised cheese slices or sticks that are individually wrapped. Accordingly, the hot pasteurised cheese mass may be manipulated to form a sheet or stick of pasteurised cheese which may then be cut to the desired size and which may then be individually wrapped if so desired. Individual wrapping of cheese slices comprising pasteurised cheese according to the methods described herein provide a product that is nutritious with a high degree of purity and authentic cheese flavour, while also having the desired flexibility of such products. In addition, it is transportable and can if desired be conveniently eaten without the need to touch the cheese by removal of part of the wrapping. Methods of providing cheese in the form of a sheet are well known in the art and include, for example, pouring the hot liquid cheese mass to form a layer, or extruding the cheese mass through a suitably shaped die or slot to form a sheet of pasteurised cheese. In some embodiments, the cheese layer may be formed on a conveyor belt as part of a continuous process.

[0097] In some embodiments, the hot liquid pasteurised cheese may be extruded or poured into a preformed continuous tube of film. This filled tube is then flattened to form a ribbon and formed into slices, usually substantially square, by crimping the ribbon at intervals. The crimped ribbon is then heat sealed and cooled prior to cutting the ribbon at the crimped portions. The required number of individually wrapped slices may then be stacked and packaged. Suitable extruder equipment is known in the art, and is commercially available from, for example, Hart Design and Manufacturing.

[0098] In some examples, it is preferred that the pasteurised cheese is raised to a temperature of 85-90 °C, or more, prior to extrusion thus providing liquid cheese that is of sufficiently low viscosity for ease of filling the tube. Furthermore, this elevated temperature ensures that the cheese temperature remains sufficiently high during the filling and sealing process to allow a vacuum to form within the sealed cheese slice on cooling. This increases the shelf life of the cheese and reduces risk of infection and spoilage.

[0099] The cooled cheese products prepared according to the present invention are typically stable at room temperature (or preferably at cooler temperatures) for greater than one month, and more preferably for greater than twelve months. Preferably the products of the methods described herein are stable for a period of greater than 12 months at a temperature of less than 10 °C, preferably less than 5 °C. The cooled products preferably resist spoilage and are not susceptible to substantial desiccation. The products of the methods described herein, following atmospheric exposure, have been observed to develop a surface layer which is slightly desiccated in character due to evaporation of surface moisture. Without wishing to be bound by theory, this surface layer is believed to discourage spoilage due to growth of microorganisms. When covered, desiccation is slow and the cheese product remains viable as a foodstuff for a substantial period of time.

[00100] The methods as described herein are applicable to a wide range of process scales using suitable apparatus well known in the art. In particular, the method may be applied through the use of, for example, a cheese “kettle” comprising heating means such as a jacket which is capable of circulating a heating/cooling liquid such as water. The vessel is preferably equipped with means for stirring the contents. Furthermore, application of a continuous manufacturing process to the methods of the present invention is anticipated. A vessel, such as a pipe, through which the flow of a material may be regulated, represents a particularly suitable apparatus through which the methods of the present invention may be performed. Vessels consisting of one or more tubes can be used to circulate the cheese mass using a pump with high velocity and with induced turbulent flow to distribute the supplied heat whilst mixing and homogenizing the mass. Such a vessel may also employ an arrangement of rotating cutters through which the cheese mass is directed.

[00101] It will be appreciated that the properties of a cheese will vary in accordance with the cheese variety. For example, Cheddar may sustain a continuous melting process from 50-100 °C without any adverse effects. Some cheese varieties, such as Emmentaler, have a dry, dense texture which benefits from the presence of an increased level of water at the beginning of the process. This may be addressed by retaining a portion of the raw cheese and adding the reserved portion at the end of the process. Preferably, the retained portion is injected into the hot cheese stream during the process. The hot viscosity of the cheese mass in a continuous process is typically below 10 mPa.

[00102] Viscosity measurement is a useful indication of the physical properties of the products of the methods of the present invention. It will be understood that the viscosity will depend on the variety of cheese used, the amount of water present and the temperature of the emulsified cheese. The viscosity of the cheese in the final cooled product can be modified by varying the ratio of casein, water and cheese in the hot product. Viscosities may be obtained at atmospheric pressure at the indicated temperature using an AND sine wave “vibro” SV-10 viscometer (A&D Mercur Pty Ltd) having standard RS-232C connectivity and Win viscometer software. “Hot viscosity” is generally determined when the cheese mass is between 70 °C and 90 °C. “Warm viscosity” is determined when the temperature of the cheese mass is between about 35 °C and 45 °C.

[00103] In order that the invention may be readily understood and put into practical effect, particular preferred embodiments will now be described by way of the following non limiting examples.

EXAMPLES

MATERIALS

[00104] Skim milk powder used in the methods described herein was commercially available medium- or high-heat skim milk powder with a WPN Index of <1.5 mg/g.

[00105] Cheddar Cheese used herein was traditionally manufactured young (14 week old) Cheddar sourced from Maffra Cheese Company, Maffra, Victoria, Australia. Cheeses such as Emmentaler and Gouda, which may also be used in the processes of the present invention, are readily available from commercial sources. Preferably the cheeses do not contain milk protein concentrate.

[00106] Cheese pasteurisation was carried out at atmospheric pressure using a covered and jacketed vessel equipped with a cutter (sharpened knives) and bowl scraper.

EXAMPLE 1: SEPARATION OF CASEIN OF SKIM MILK POWDER

[00107] Skim milk powder (500 g, 32.6% protein, 51.5% lactose, WPN index 1.19 mg/g) was combined with food grade water (500 g) in a batch processor to form skim milk concentrate. The concentrate was heated by water vapour at atmospheric pressure. [00108] The mixture was heated to 95 °C, the source of heat was removed and the mixture was allowed to cool until syneresis occurred (about 80 °C). The mixture was separated by transferring to a rotary centrifuge to separate the saturated lactose concentrate from the viscous casein (protein) fraction. The rotary centrifuge employed had a screen diameter of 185 mm to support a polypropylene filter cloth having apertures of 40 microns and the speed of rotation was approximately 2800 rpm. Alternatively, a horizontal decanter separator may be used. The filtrate comprised mainly lactose at approximately 35% solids. The yield of lactose recovered was calculated to be approximately 70% based on the estimated amount of lactose in the skim milk powder.

[00109] The retained milk protein fraction comprised mainly casein. The protein fraction was then subjected to purification by three phases of washing and centrifugation using fresh water at each stage to remove residual lactose. The resulting casein fraction (45.6% solids; remainder water) was used without further extraction of casein.

[00110] It is well understood that the weight ratio of whey protein to casein in skim milk is about 0.18:1. Compositional analysis (BVAQ Pty Ltd) of a sample prepared according to the above method (prior to washing and centrifugation) showed a weight ratio of whey protein to casein of about 0.021:1. The approximately 10-fold reduction in whey protein is believed to be due to detachment and separation of whey protein from casein micelles using the above method, providing a casein fraction after washing and centrifugation with negligible amounts of whey protein.

EXAMPLE 2: EMULSIFICATION OF CASEIN

[00111] Hydrated gelatine gel was prepared by dissolving gelatine powder (5 g, strength 150 Bloom grams) in water (100 g) at 80 °C and allowing the solution to cool to ambient temperature to form a hydrated gelatine gel.

[00112] Casein emulsion was prepared by combining casein extracted according to the process of Example 1, (1000 g; 45.6% solids) and gelatine gel (100 g water : 5 g gelatine). The resulting mixture was heated to 95 °C over 20 minutes under vigorous stirring to form the casein emulsion. The casein emulsion allowed to cool to ambient temperature before further use (or for storage), or it may be used hot in any subsequent processing steps.

[00113] The casein emulsion produced in Example 2 had a gelatine content of about 0.45% w/w based on the initial amounts of ingredients. EXAMPLE 3: EMULSIFICATION OF CASEIN USING CASEIN REWORK

[00114] Casein extracted according to the process of Example 1 (1000 g; 45.6% solids) was combined with hot emulsion of Example 2 (“casein rework”, 100 g) and the resulting mixture was heated according to the procedure described about for Example 2. The casein emulsion may be allowed to cool to ambient temperature before further use (or for storage), or it may be used hot in any subsequent processing steps.

[00115] The casein emulsion produced in Example 3 was similar to that produced in Example 2, however the emulsion had a gelatine content of about 0.041% w/w based on the initial amounts of ingredients.

EXAMPLE 4: PASTEURISATION OF CHEDDAR USING CASEIN EMULSION

[00116] The hot casein emulsion prepared in Example 3 (100 g) was combined with Cheddar (1000 g) and water (400 g). The mixture was heated by indirect water vapour at atmospheric pressure and raised to 50 °C over 50-60 seconds under vigorous stirring in a jacketed vessel using rotating sharpened knives. The rate of mechanical stirring was reduced, and the vapour temperature was increased rapidly to 95-100 °C allowing the temperature of the cheese mixture to rise to 95 °C or higher. The resulting pasteurised cheese emulsion may be allowed to cool to ambient temperature before further use (or for storage), or it may be used hot in any subsequent processing steps.

[00117] The pasteurised cheese mass produced in Example 4 had a gelatine content of about 0.0027% w/w based on the initial amounts of ingredients.

[00118] The disclosure of every patent, patent application, and publication cited herein is hereby incorporated herein by reference in its entirety.

[00119] The citation of any reference herein should not be construed as an admission that such reference is available as “Prior Art” to the instant application.

[00120] Throughout the specification the aim has been to describe the preferred embodiments of the invention without limiting the invention to any one embodiment or specific collection of features. Those of skill in the art will therefore appreciate that, in light of the instant disclosure, various modifications and changes can be made in the particular embodiments exemplified without departing from the scope of the present invention. All such modifications and changes are intended to be included within the scope of the appended claims. [00121] The reference in this specification to any prior publication (or information derived from it), or to any matter which is known, is not, and should not be taken as an acknowledgment or admission or any form of suggestion that that prior publication (or information derived from it) or known matter forms part of the common general knowledge in the field of endeavour to which this specification relates.