WO2022136562A1

WO2022136562A1 - Method of preparing cheese curds

Info

Publication number: WO2022136562A1
Application number: PCT/EP2021/087321
Authority: WO
Inventors: Saeed Rahimi YAZDI; Søren K. Lillevang; Bhavin PARMAR
Original assignee: Arla Foods Amba
Priority date: 2020-12-22
Filing date: 2021-12-22
Publication date: 2022-06-30

Abstract

The present invention relates to a method of preparing cheese curds without any pH adjustment and wherein the calcium content in the cheese curds is controlled. In particular, the present invention relates to a method of preparing cheese curds using ultra filtration and optionally diafiltration to reduce the calcium content. The cheese curds obtained can be used for preparing various cheeses, for example pasta filata cheeses, such as mozzarella or mozzarella-like cheeses.

Description

Method of preparing cheese curds

Technical field of the invention

The present invention relates to a method of preparing cheese curds without any pH adjustment, but wherein the calcium content is still controlled. In particular, the present invention relates to a method of preparing cheese curds using ultrafiltration, and optionally in combination with diafiltration, to reduce the calcium content. The cheese curds obtained can be used for preparing various cheeses, for example pasta filata cheeses such as mozzarella or mozzarella-like cheeses.

Background of the invention

Pasta filata cheeses, such as for example mozzarella, are widely used in many food applications such as topping on pizza.

Calcium plays an important role during manufacturing of the pasta filata cheese and also in deciding functionality of the cheese. The calcium content, for example, is known to have an influence on the melting and stretching properties. The lower the calcium/protein ratio is in the pasta filata cheese, the more melt and stretch can be obtained. However, a certain calcium content is also necessary because calcium provides linkages within and among casein micelles and therefore helps with forming a network structure of caseins during the coagulation process of milk proteins.

Methods of reducing calcium content in a pasta filata cheese is known, for example by a pre-acidification of the milk used for preparing the curds, addition of lactic acid bacteria and/or acids during the coagulation step. The acidifying agents will both solubilize and remove calcium but also work as a coagulation agent. However, when using acidifying agents for removing calcium, it is very difficult to control the removal of calcium and hence the level of calcium removed/maintained. Further, using acidifying agents will initiate the coagulation of the casein proteins when pH is below 6.2. Some manufacturers only use acidifying agents for coagulation while other manufacturers use coagulation enzymes for the the coagulation. When using acidifying agents (chemical acids and/or acid producing cultures) in preparing cheese curds, it will result in a whey product comprising the acidifying agents and having a low pH (typically called acid whey) which decreases the useability of the whey.

Further, traditional cheese making involves a vat process that is time-consuming. Besides from being time-consuming, a vat process requires that all ingredients are added to the vat and all process steps are performed in the vat. This makes the process more difficult to control. For example, addition of starter cultures will continue to work in a vat process leading to a lower pH and a very soft product. A cheese prepared using a vat process will also have a variation from vat to vat, and will need advanced and expert control since the vat process is complex and not straightforward. The vat process is difficult to control since many process parameters may vary, and it is only possible to see product changes after the entire process is completed and not after the individual process steps. Further, the single steps in a vat process can affect the final quality of the product heavily. For example, after precipitation of casein (coagulation step), the obtained cheese curds and liquid whey are both present in the vat. To continue processing of the curds, the whey is drained in a draining step. However, when both curds and whey is present in the vat, further processing of the cheese curds may be difficult, for example, if the drainage is stopped or delayed. The vat process also requires frequent cleaning.

WO 2008/063 084 Al discloses a continuous process of preparing cheese or cheese curds involving acidifying a starting milk having a temperature of 5°C to 25°C to a pH level of 4.6 to 6.2, adding an enzyme capable of converting kappa casein into para-kappa casein and mixing rapidly, passing the mixture through a flow device for about 1 to 1000 seconds to allow the enzyme to react with the milk protein, before heating the enzyme-reacted mixture to a temperature from 30°C to 55°C to initiate coagulation and produce curd particles within the flow device. However, an improved method of preparing cheese curds with an improved control of calcium removal would be advantageous, and, in particular, a more efficient method of preparing cheese curds without the use of acidifying agents would be advantageous. Further, a method of preparing cheese curds with improved calcium control that can be processed into various types of cheeses such as pasta filata cheeses having good functionalities would be advantageous.

Summary of the invention

Thus, an object of the present invention relates to providing a method of preparing cheese curds with an improved control of the calcium level.

In particular, it is an object of the present invention to provide a method of preparing cheese curds that solves the above mentioned problems of the prior art with the use of acidifying agents for calcium removal.

Thus, one aspect of the invention relates to a method of preparing cheese curds wherein no acidifying agents or acid producing microorganisms are added during the method, and wherein the method comprises the following steps: i) providing a milk derived feed that has not been subjected to any pH adjustment; ii) subjecting the milk derived feed to ultrafiltration (UF) with an ultrafiltration membrane to provide a UF permeate and a UF retentate and to obtain a protein content in the UF retentate of at least 10% by weight; iii) optionally subjecting the UF retentate to diafiltration (DF) with an ultrafiltration membrane to obtain a DF permeate and a DF retentate; iv) optionally diluting the UF retentate obtained in step ii) or the DF retentate obtained in step iii) with a liquid to obtain a protein content in the diluted UF retentate or the diluted DF retentate in an amount of 5-18 % by weight; v) adjusting the temperature of the UF or DF retentate or diluted UF or DF retentate to a temperature of 4 to 15°C; vi) adding one or more coagulating enzyme(s) to the temperature adjusted UF retentate or DF retentate of step v) and storing for at least 30 minutes; vii) heating the mixture of step vi) to a temperature in the range of 25°C to 60°C for a time period sufficient to coagulate the mixture and obtain cheese curds and whey; viii) optionally separating the cheese curds from the whey.

A further aspect of the invention relates to providing a method of preparing a cheese product comprising the steps of: a) providing cheese curds obtained by the method according to any of the claims 1 to 10; b) optionally adding fat to the cheese curds to obtain fattened cheese curds; c) subjecting the cheese curds of step a) or b) to further processing to obtain a cheese product.

The cheese product is preferably a pasta filata cheese obtained by heating and stretching the cheese curds.

Brief description of the figures

Figure 1 shows a flow sheet of a process where a milk derived feed has been subjected to ultrafiltration before it being processed into cheese curds.

Figure 2 shows a flow sheet of a process where a milk derived feed has been subjected to ultrafiltration and diafiltration before it being processed into cheese curds.

Figure 3 shows a flow sheet of a process where a milk derived feed has been subjected to ultrafiltration, dilution and diafiltration before it being processed into cheese curds.

Figure 4 shows the blister color of cheeses prepared by using a milk derived feed subjected to A) no membrane filtration, B) ultrafiltration, and C) ultrafiltration and diafiltration.

Figure 5 shows the browning area of cheeses prepared by using a milk derived feed subjected to A) no membrane filtration, B) ultrafiltration, and C) ultrafiltration and diafiltration. Figure 6 shows a spiderweb diagram showing the sensoric parameters of a mozzarella made from cheese curds with a low calcium content compared to a mozzarella made with cheese curds having a high calcium content.

The present invention will now be described in more detail in the following.

Detailed description of the invention

Definitions:

Prior to discussing the present invention in further details, the following terms and conventions will first be defined:

All references to singular characteristics or limitations of the present invention shall include the corresponding plural characteristics or limitations, and vice versa, unless otherwise specified or clearly implied to the contrary by the context in which the reference is made.

All percentages referred to herein are percentages by weight unless otherwise stated. The term "w/w" also refers to weight percentage. For example, 1% w/w refers to a composition comprising 1% by weight of a compound.

Milk derived feed:

The milk derived feed may be based on milk from mammals such as cows, buffalos, goats, sheep, yaks, pigs, horses, ewes, mares, or mixtures thereof. In a preferred embodiment of the present invention, the milk derived feed is from cows, i.e. bovine milk. The terms bovine milk and cow's milk refer to the same.

The milk derived feed used may for example be whole milk, low-fat milk, reduced fat milk, fat-free milk, reconstituted milk powder, heat treated milk (e.g. pasteurized milk, and UHT milk), raw unfiltered milk, homogenized milk, mineral reduced milk, whey protein reduced milk, micellar casein isolate, micellar casein concentrate, and combinations thereof. In a preferred embodiment of the invention, the milk derived feed is pasteurized milk, and especially pasteurized bovine milk. When referring to pasteurized milk, it may in principle be any type of the above mentioned milk products that have been pasteurized, such as pasteurized whole milk, low-fat milk, reduced fat milk, fat-free milk, raw unfiltered milk, homogenized milk, mineral reduced milk, whey protein reduced milk, micellar casein isolate, and micellar casein concentrate.

Further, in a preferred embodiment, the milk derived feed is a milk feed where fat is partly or fully removed, such as low-fat milk, reduced fat milk, or fat-free milk. It is preferred that the fat content of the milk derived feed has been removed or at least partly removed from milk before further processing since fat in the milk derived feed will lower the filtration capacity during the ultrafiltration and diafiltration at cold temperatures. In the method of the present invention, it is preferred to avoid loss of fat during the membrane filtration steps. Hence, the fat is typically fully or partly removed before the ultrafiltration step. In the process of preparing the cheese curds of the invention, fat removed can be added later in the process after the membrane process to obtain cheese curds with a desired fat content.

In a preferred embodiment of the invention, the milk derived feed is a combination of two or more of whole milk, low-fat milk, reduced fat milk, fat-free milk, reconstituted milk powder, heat treated milk, raw unfiltered milk, homogenized milk, mineral reduced milk, whey protein reduced milk, micellar casein isolate, micellar casein concentrate, such as for example a combination of fat-free milk and a micellar casein isolate.

The fat in a starting milk (in the milk derived feed) may be removed by a process known as fat standardization. Traditionally, standardization of milk has been achieved by removing nearly all the fat (cream) from the starting milk (by separation technique) and adding back a known amount of cream thereto to achieve a predetermined protein/fat ratio in the milk. Fat standardization is typically performed by subjecting the milk to centrifugation which separates the cream fraction from the skim milk fraction (reduced fat milk fraction).

In a preferred embodiment of the present invention, the milk derived feed comprises fat in an amount of 0.1% by weight or less. Preferably, the milk derived feed comprises fat in an amount of 0.05% by weight or less. The milk derived feed comprises milk proteins including both casein and milk serum protein.

The casein in the milk derived feed is primarily present in the form of casein micelles, similar or even identical to the casein micelles found in e.g. skimmed milk.

The term "milk serum" refers to the liquid phase of milk in which casein micelles and milk fat globules are dispersed.

In the context of the present invention, the terms "milk serum protein" or "serum protein" refer to the protein found in the milk serum. The milk serum proteins typically include beta-lactoglobulin, alpha-lactalbumin, bovine serum albumin, immunoglobulin and osteopontin as well as lactoferrin and lactoperoxidase. The milk serum protein may furthermore contain a significant amount of beta-casein when the milk feed has been stored at low temperature without it being subsequently heat treated.

The term "protein" refers in the context of the present invention to polypeptides containing at least 10 amino acids and encompasses both single polypeptides and aggregates of polypeptides.

The term "non-protein nitrogen" (NPN) refers to nitrogen found in molecules that are not protein. In milk, a significant portion of the NPN contains urea, ammonium salts and small peptides containing less than 10 amino acids.

The term "whey" refers to the liquid obtained after casein is precipitated in milk. In the present invention, precipitation of casein is obtained by using a coagulation enzyme, for example rennet. In other methods known in the art, the coagulation is due to acidification or a combination of acidification and addition of coagulation enzymes. The whey obtained from precipitation of casein by use of a coagulation enzyme is typically referred to as sweet whey, and the whey obtained from acid precipitation of casein micelles is typically referred to as acid whey or sour whey. Where acid whey has limited use, the sweet whey can be further processed into various products, e.g. whey protein products or lactose products.

The term "cheese curd" refers to cheese particles obtained after coagulation of caseins in a milk derived feed.

In some embodiments of the invention, the milk serum protein of the milk derived feed is present in undenatured, native form, i.e. the same form as in raw milk, which has not been subjected to a denaturing heat treatment. It is therefore also preferred that the milk derived feed and the product stream from which the milk feed has been derived have not been subjected to conditions that have resulted in significant protein denaturation, such as e.g. high temperature for prolonged durations. However, the milk derived feed may be pasteurized. Pasteurization of the milk derived feed may take place under standard conditions, namely, heat treatment of the milk derived feed at a temperature and time sufficient to kill pathogens, typically at 72°C for 15 seconds.

In an embodiment of the invention, the milk derived feed comprises a total amount of protein in the range of 1-10% (w/w). Preferably, the milk derived feed comprises a total amount of protein in the range of 2-8% (w/w), and, even more preferably, the milk derived feed comprises a total amount of protein in the range of 3-5% (w/w), such as 3.0-4.6.

The milk derived feed typically has a ratio by weight between caseins and milk serum protein in the range of 70: 30 to 90: 10, such as for example in the range of 75:25 to 85: 15, and typically in the range of 77:23 to 83: 17.

The solid content of the milk derived feed may vary depending on the used feed, but it is typically in the range of 1-30% (w/w). Preferably, the solid content of the milk derived feed is in the range of 4-25% (w/w). Even more preferably, the solid content of the milk derived feed is in the range of 5-15% (w/w).

In an aspect of the present invention, the milk derived feed has not been subjected to any pH adjustment and the method excludes addition of acidifying agents and/or acid producing microorganisms. Hence, no acidifying agents have been added to the milk derived feed or during the method, including both chemical acids and acid producing bacterias, and the pH of the milk derived feed corresponds to the pH of natural fresh milk. Hence, the pH of the milk derived feed is in the range of 6.5 to 7.2, in particular in the range of 6.7 to 6.9. It has surprisingly been found by the inventors of the present invention that it is possible to prepare cheese curds with efficient and controlled removal of calcium and without any acidification step both of the milk derived feed and during the hydrolysis and coagulation step. In prior art, the preparation of cheese curds typically involves an acidification step, i.e. either adding chemical acids or adding lactic acid producing bacterias or both. However, in the method of the present invention, the inventors have surprisingly found that a controlled removal of the calcium content from the milk derived feed can be obtained by subjecting the milk derived feed to ultrafiltration without adding any acidifying agents. In a preferred embodiment of the present invention, ultrafiltration of the milk derived feed is in combination with diafiltration. The inventors of the present invention have found out that with the present invention, it is possible to prepare cheese curds with an appropriate level of calcium removal from the starting milk (milk derived feed) without any pH adjustment. Hence, besides from the method of the present invention providing a controlled removal of calcium, the method also provides a method where the whey obtained comprises no acidifying agents.

It is important that the pH of the milk derived feed corresponds to the pH of fresh milk and that no acidifying agents have been added. Hence, in the method of the present invention, no acidifying agents or acid producing cultures are added. A pH adjustment of the milk derived feed to a pH below 6.5 results in intitiation of unwanted gelation and precipitation in the milk derived feed. Gelation and precipitation of the milk derived feed before or during ultrafiltration are wished avoided as it will clog the membrane such that calcium cannot efficiently be removed. Further, an acidic environment will soften the hair of casein micelles such that the casein micelles will stick together and prevent calcium to leach out. In addition, a high degree of acidification can lead to excess calcium removal that could result in some deficiencies in the cheese obtained. In a preferred embodiment, no pH adjusting agents have been added during the entire method of preparing the cheese curds, i.e. no acids or acid producing bacterias have been added.

In an embodiment of the present invention, the milk derived feed is an organic milk derived feed derived from an organic milk source. In a preferred embodiment of the invention, the milk derived feed is an organic skimmed milk.

In the context of the present invention, the term "organic milk" refers to milk produced by mammals, such as cattle, raised according to the following : the cattle must have free access to certified organic pasture for the entire grazing season. This period is specific to the farm's geographical climate but must be at least 120 days per year and preferably at least 150 days. Due to the weather, season, or climate, the grazing season may or may not be continuous. Organic cattle diets must contain at least 30 percent dry matter (on average) from certified organic pasture. Dry matter intake (DMI) is the amount of feed an animal consumes per day on moisture-free basis. The rest of its diet must also be certified organic, including hay, grain, and other agricultural products. The livestock should be managed without antibiotics, added growth hormones, mammalian or avian byproducts, or other prohibited feed ingredients (e.g. urea or arsenic compounds).

In an embodiment of the invention, the temperature of the milk derive feed is, or is adjusted to be, in the range of 2°C to 15°C, preferably 4°C to 10°C. At temperatures in this range, the calcium removal and mineral balance change during ultrafiltration and optionally diafiltration is better. At temperatures in the range of 2°C to 15°C, preferably 4°C to 10°C, beta-casein in casein micelles is dissolved and the casein micelles are disturbed such that calcium will leach out.

Ultrafiltration and diafiltration:

The milk derived feed is, in the method of preparing cheese curds of the present invention, subjected to ultrafiltration (UF) with an ultrafiltration membrane to provide a UF permeate and a UF retentate and to obtain a protein content in the UF retentate of at least 10% by weight. In a preferred embodiment of the invention, the UF retentate is subjected to a diafiltration step (DF) with an ultrafiltration membrane to obtain a DF retentate and DF permeate.

The ultrafiltration step will concentrate proteins in the UF retentate but reduce the calcium content in the retentate, since some calcium will be lost in the UF permeate. It is important with the ultrafiltration step to increase the protein to calcium ratio in the feed used for preparing cheese curds.

Ultrafiltration of the milk derived feed reduces the calcium content and in the method of the present invention it is necessary to perform ultrafiltration such that the protein content is concentrated to a level of at least 10% by weight.

Further, the combination of ultrafiltration and diafiltration reduces the calcium level in the milk derived feed even further. The ultrafiltration step will remove some calcium, but the combination of ultrafiltration and diafiltration will remove more calcium and hence have an increased effect on calcium removal. The combination of ultrafiltration and diafiltration will therefore increase the protein to calcium ratio further as compared to when using ultrafiltration alone. A reduced calcium content leads to cheese curds that when processed into cheese will have good functional properties. For example, the stretching and melting properties of mozzarella are improved while less browning is obtained of the product during baking. Hence, with the method of the present invention, cheese curds can be obtained without adding any pH adjusting agents, while at the same time the calcium content is significantly reduced such that cheeses with good functionalities, and functionalities matching those of cheese curds obtained by known processes, are obtained.

In an embodiment of the invention, the ultrafiltration is performed such that the total protein content in the UF retentate is at least 12% by weight, such as at least 15% by weight, and even further at least 18% by weight.

In another preferred embodiment of the invention, the ultrafiltration is performed such that the protein content in the UF retentate is in the range of 10 to 25% by weight, more preferably 10 to 23% by weight, and even more preferably in the range of 10 to 21% by weight. In the diafiltration step, the protein content is preferably maintained constant but the calcium content is reduced.

Hence, if diafiltration is performed on the UF retentate, the diafiltration retentate obtained will comprise a total amount of protein of at least 10% by weight.

Preferably, the amount of total protein in the DF retentate will be in the range of 10 to 25 % by weight, such as 10 to 18% by weight, more preferably 10 to 15% by weight. Most preferably, the amount of total protein in the DF retentate is in the range of 10 to 12% by weight.

In prior art, calcium has been removed from a milk feed by addition of acidifying agents, for example addition of acids in combination with ultrafiltration. However, in the present invention, it is wished to reduce the calcium content at neutral pH without addition of acidifying agents since it will lead to a whey comprising no acids and hence being more suitable for further use. The inventors of the present invention have surprisingly found out that it is possible to prepare cheese curds for use in cheese making that have good functional properties, but where the calcium content is reduced without adding any pH adjusting agents. Cheese curds having a reduced calcium content as compared to naturally milk will lead to cheese having a good elasticity and good melting properties. A high calcium content, on the contrary, results in cheeses that cannot melt properly and hence match the standard functionality. Such cheeses are rubbery in consistence.

Further, if the milk derived feed has a pH below 6.1 during ultrafiltration and optionally diafiltration, gelation and precipitation will occur. Gelation and precipitation is wished avoided since it will clog the UF membrane and hence impair the method.

The ultrafiltration membrane used for ultrafiltration and diafiltration may be the same or different membranes. The membrane used for ultrafiltration and diafiltration is typically the same. The UF membrane allows passage of small peptides, minerals and some lactose into the permeate while retaining the milk serum protein, micellar casein, dissolved beta-casein and some lactose. Approximately, 50% of the lactose in the milk derived feed will be retained in the retentate while approximately 50% penetrates the UF membrane and is present in the permeate.

In fresh milk, the lactose content is about 4.5% by weight. After the ultrafiltration step in the method of the present invention, the lactose content is about 2 to 3% by weight in the UF retentate. Further, after the diafiltration step, the content of lactose in the DF retentate is about 1-1.5% by weight. The content of lactose in the UF retentate and DF retentate is dependent of the concentration factor. Further, a reduced lactose content is relevant for obtaining a golden cheese surface when baked/melted instead of a brown surface.

According to an embodiment, the cut-off of the ultrafiltration membrane used for the ultrafiltration and optionally diafiltration is in the range of 2000 Da - 50000 Da, preferably 2500 - 30000 Da, more preferred about 20000 Da. In a preferred embodiment of the invention, a polymeric membrane is used having a molecular weight cut-off of 20000 Da.

The ratio between the casein and milk serum protein will after ultrafiltration and optionally diafiltration be the same as for the milk derived feed used

The concentration factor (CF) of the ultrafiltration step may for example be in the range of 2.85 to 7.5. Preferably, the concentration factor is in the range of 3 to 6, and even more preferably in the range of 3.0 to 5.1. A concentration factor in the range of 2.85 to 7.5 corresponds to obtaining a protein content in the ultrafiltration retentate in the range of 10% to 26% by weight. Further, a concentration factor in the range of 3 to 5.1 corresponds to obtaining a protein content in the ultrafiltration retentate in the range of 10.5% to 18% by weight.

The concentration factor of the diafiltration step is in an embodiment of the invention in the range of 1.1 to 7.5.

The concentration factor is defined as the weight ratio between the protein content in the liquid milk derived feed to the protein content in the retentate obtained. Hence, if the concentration factor is 3, the protein content in the UF retentate has been concentrated 3 times as compared to the protein content in the milk derived feed. Hence, if the milk derived feed has a protein content of 3.5% by weight and a CF of 3, the protein content in the UF retentate is (3.5x3) 10.5% by weight.

The calcium content in the UF or DF retentate is reduced up to 50% by weight as compared to the calcium content in the milk derived feed. The amount of calcium removed is dependent on the concentration factor. The amount of calcium removed during the ultrafiltration and optionally diafiltration step as compared to the calcium content in the milk derived feed is in the range of 30 to 50% by weight. As mentioned earlier, it is important for the present invention that a substantial amount of calcium is removed and this can be obtained with ultrafiltration with a high concentration factor, such as a concentration factor in the range of 2.85 to 7.5 or with the combination of ultrafiltration and diafiltration. On the contrary, it is also important that calcium is not totally removed since if more than 50% by weight calcium is removed no gelation occur and cheese curd cannot be formed. If too much calcium is removed, the casein micelles are turned to soluble caseins having no functionality. With the present invention, the removal of calcium can be controlled much better than compared to removing calcium by addition of acidifying agents. The calcium content is measured using X-ray flourescence spectroscopy from Rigaku Ltd.

In a preferred embodiment of the invention, calcium is not added before or after the ultrafiltration and optionally diafiltration step.

If a fat-free milk (skim milk) is used as the milk derived feed, the calcium content will typically be about 1000-1400 mg/kg and the protein content 35g/kg. This corresponds to a calcium content of 1-1.4g per 35 g protein (in 1 kg milk) which is equal to 0.028-0.040g calcium per g protein. After ultrafiltration to a 10% protein content in the UF retentate, i.e. a concentration factor of 2.85 (10/3.5), the calcium content in the UF retentate will be about 2138 to 2992 mg/kg. This corresponds to a calcium content of 0.021 to 0.030g calcium per gram protein. After ultrafiltration and diafiltration, the calcium content is reduced to 1600-2250 mg/kg. This corresponds to 0.0160 to 0.0225 g calcium per g protein. Hence, after both ultrafiltration and diafiltration (to a 10% protein content), the calcium content per gram protein is reduced with about 40-43% as compared to skim milk.

The UF retentate or DF retentate obtained may in an embodiment of the invention be diluted with a liquid to obtain a diluted UF retentate or diluted DF retentate having a protein content of 5-18% by weight. The protein content is measured using the FoodScan™ Dairy analyser using near infrared transmission technology (NIT).

In a preferred embodiment of the invention, the milk derived feed is subjected to ultrafiltration to obtain a protein content in the retentate of at least 18% by weight and the UF retentate is subjected to dilution to a protein content of 5-18% by weight before further processing.

Useful, but not limiting, examples of diluents which can be used for diluting of the UF retentate or the DF retentate are demineralized water or reverse osmosis (RO) water. The demineralized water may also be referred to as destilled water. The RO water refers in the context of the present invention to any permeate from membrane filtration of milk and tap water that has been subjected to reverse osmosis. Hence, RO water may be a permeate obtained by reverse osmosis of a permeate from ultrafiltration of milk, reverse osmosis of a permeate from nanofiltration of milk, or reverse osmosis of tap water.

In a preferred embodiment of the invention, the UF retentate or DF retentate is diluted with RO water to obtain a content of total protein of 5 to 18% by weight, preferably 8 to 12%.

In an embodiment of the invention, the temperature during the ultrafiltration and optionally diafiltration step is in the range of 2°C to 15°C, preferably 4°C to 10°C.

Temperature adjustment:

The temperature of the UF retentate, diluted UF retentate, DF retentate or diluted DF retentate is adjusted to a temperature of 4 to 15°C. The temperature should be adjusted to 4°C to 15°C before adding the coagulating enzyme. At temperatures below 4°C, the coagulating enzyme will not work efficiently and provide proper hydrolysis. Furthermore, at temperatures above 15°C, the coagulation will initiate. This should be avoided at this stage. The warmer the mixture/solution is, the faster the coagulation is. Preferably, the temperature is adjusted to a temperature of 5°C to 10°C to avoid spontaneous coagulation. If the temperature is in the range of more than 10°C and up to 15°C, the coagulation enzyme is slightly active and there is a risk of coagulation being initiated which is wished avoided. However, at temperatures of more than 10°C and up to 15°C, the activity of the coagulation enzyme is still very low. Hence, even though temperatures of more than 10°C and up to 15°C are not optimal, the method can be carried out by adjusting to the temperature range of 4°C to 15°C before adding the coagulation enzyme.

Hydrolysis with coagulating enzyme:

One or more coagulating enzyme(s) is/are added to the temperature adjusted UF retentate, diluted UF retentate, DF retentate or diluted DF retentate and the mixture is stored at the mentioned temperature (4-15°C) for at least 30 minutes, preferably at least 1 hour, to allow hydrolysis of proteins. The hydrolysis should be for at least 30 minutes because hydrolysis below 30 minutes will increase the loss of protein in whey. In an embodiment of the invention, the temperature adjusted UF retentate, diluted UF retentate, DF retentate or diluted DF retentate mixed with coagulating enzyme(s) is stored cold for 30 minutes to 48 hours before further processing. Preferably, the DF retentate or diluted DF retentate with coagulating enzyme(s) added is stored cold for 1 hour to 40 hours, such as 2 hours to 35 hours.

The coagulating enzyme(s) is/are added at cold temperatures, i.e. 4-15°C, to control the clotting of the curd (coagulation) and to improve the control of starting/stopping the curd formation process. By adding the coagulating enzyme(s) at cold temperatures, the enzymatic hydrolysis with the coagulating enzyme(s) can occur while no coagulation occurs. The coagulating enzyme(s) cuts caseinomacropeptide (CMP) from casein such that casein becomes more hydrophobic and can adhere (stick together) to each other. The coagulating enzyme(s) is/are preferably added under stirring or mixing to distribute the enzyme(s) evenly throughout the UF retentate, diluted UF retentate, DF retentate or diluted DF retentate.

The UF retentate, diluted UF retentate, DF retentate or diluted DF retentate with added coagulating enzyme should be stored for a minimum period of time of 30 minutes for the coagulating enzymes to cut CMP from casein. In principle, there is no upper time limit for the cold storing of the UF retentate, diluted UF retentate, DF retentate or diluted DF retentate mixed with coagulating enzyme(s) because the temperature is so low that coagulation does not occur and there is no culture or acidifying agents present. However, for time efficiency, the cold storing is up to 48 hours.

The coagulating enzyme may be any enzyme that has (kappa)-caseinolytic activity and that when used in an effective amount is capable of coagulating milk derived feeds such that curds are obtained. For example, the coagulating enzyme may be rennet, chymosin, pepsin, microbial rennets, recombined rennets, any other suitable microbial or vegetable derived protease with caseinolytic activity or a combination thereof. A bacterially derived proteolytic enzyme (fermentation produced enzyme) may be Fromase® XL750 (DMS Food Specialities, Herten, Netherlands) or ChyMax® (Christian Hansen A/S, Horsholm, Denmark). Naturen® (Christian Hansen A/S, Horsholm, Denmark) is an example of an animal rennet. One example of a suitable beneficial kappa-caseinolysis enzyme is an enzyme of vegetable origin, namely that obtained from the Card Cardosin. In a preferred embodiment of the invention, the coagulating enzyme(s) is any type of rennet and may therefore be selected from the group of rennet, microbial rennets and recombined rennets. In another preferred embodiment of the invention, the coagulating enzyme(s) comprises chymosin.

Rennet is a complex set of enzymes (when describing commercial products) produced in the stomach of ruminant mammals or produced by microorganisms. In the context of the present invention, the term "rennet" refers to rennet obtained from an animal stomach. Microbial rennet is obtained by fermentation by exposing certain microorganisms to rennet-producing genes from animals. Microbial rennet may also be referred to as vegetable rennet. The main enzyme in rennet is chymosin which is a protease enzyme cleaving the kappa casein chain. Cleavage causes casein to stick to other cleaved casein molecules and form a network, and hence curdles the casein in milk. The clustering of casein proteins is improved in the presence of calcium and phosphate, and therefore it is beneficial that some calcium is remained during production of the cheese curds. In addition to chymosin, rennet contains other enzymes such as pepsin and a lipase.

The coagulating enzyme, such as rennet, is typically added to the DF retentater or diluted DF retentate in an amount from 5 ml/100 kg liquid (DF retentate or diluted DF retentate) to 50 ml/100 kg liquid when having an activity of 200-600 IMCU /ml. IMCU stands for International Milk Clotting Unit as defined in International Standard ISO 11815 (2007).

Coagulation and formation of cheese curds:

The UF retentate, diluted UF retentate, DF retentate or diluted DF retentate is, after adding the coagulating enzyme(s) and after cold storage, heated to a temperature in the range of 25°C to 60°C for a time period sufficient to coagulate the mixture and obtain cheese curds and whey.

Preferably, the heating during the coagulating step is at a temperature of 35°C to 55°C and most preferably at a temperature of 40°C to 50°C. As mentioned earlier, coagulation is initiated when the temperature is above 15°C. However, at 15°C, the speed of coagulation is very low. Hence, the temperature during the coagulation step should be above 25°C for efficient coagulation. At temperatures above 40°C, coagulation proceeds very rapidly within seconds and almost instantly. A temperature above 40°C is therefore preferred.

Further, the temperature during the coagulation step should not exceed 60°C since at a temperature above 60°C unwanted sticking of the obtained cheese curds occurs. Furthermore, the cheese curds begin to stretch at high temperatures which is wished avoided at this point in the process.

The time period of the coagulation step may vary a lot since the time required for coagulation is dependent on the temperature. Hence, at a temperature of 25°C, coagulation takes some time and the time period may therefore be several minutes and up to 60 minutes for efficient coagulation. However, if the temperature is 40°C to 60°C, the time period for coagulation is within seconds (0.1-10 seconds) and may be instantly. At temperatures above 40°C, the coagulation starts instantly. The coagulation continues and complete coagulation is probably after 10-30 seconds. Hence, the time period for the coagulation step should not be seen as any limitation of the present invention. However, typically the time period for the coagulation is 0.1 second to 60 minutes.

Preferably, the mixture of UF retentate, diluted UF retentate, DF retentate or diluted DF retentate mixed with the coagulating enzyme(s) is stirred during the coagulation step to induce controlled turbulence in the solution to cause coagulation of the protein into small curd particles within the solution. The liquid obtained after obtaining the curd particles is called whey. In embodiments of the invention, the curd is separated from the whey.

The heating is typically by using direct or indirect heating means to coagulate the protein and form the coagulated curd particles. In the case of direct heating, steam can be injected into the flow of the liquid UF retentate, diluted UF retentate, DF retentate or diluted DF retentate. In the case of indirect heating, a jacketed heater or heat exchanger is associated with the flowpath along which the liquid is being pumped. The temperature is increased to an upper limit which will be consistent with the parameters of the process, for example up to 55°C and the flow rate is high causing controlled substantial turbulence into the liquid being passed therealong. This prevents any large build up of curd and means that the protein coagulates into small curd particles.

The coagulated cheese curd (curd particles) can be separated from the whey by use of a separator, such as for example a decanter, a sieve, a filter or other means suitable for separating curds from whey. The whey will comprise most of the calcium that has not been removed earlier during the UF/DF step. However, some calcium is also present in the cheese curds.

The dry matter content of the cheese curds obtained is comparable to standard cheese curds, i.e. cheese curds obtained by known processes. The dry matter content in the cheese curds obtained is in the range of 35 to 50% by weight. A high dry matter content in the cheese curds is preferred such that it is possible to produce high dry matter cheeses. If more moisture is needed in the preparation of a specific cheese, it can be added later on.

The cheese curd may be stored before further processing but may also be processed immediately while still fresh into cheeses, for example pasta filata cheeses. The cheese curds could for example be frozen and/or dried, and subsequently thawed and/or reconstituted before further processing into cheese.

Continuous process:

According to an embodiment, the method of preparing cheese curds is conducted as a continuous process.

By the term "continuous" is meant what is normally understood by the skilled person, namely a method/process where cheese curds are continuously made instead of in batches.

Typically, cheese curds have been processed in a vat but the inventors of the present invention have found out that it is possible to prepare the cheese curds in a continuous process and that this gives advantages.

In the continuous method of the present invention, the milk derived feed is continuously flowed in pipes or tubes, continuously passed through an ultrafiltration membrane and optionally a diafiltration membrane and temperature adjusted. Coagulating enzyme(s) is/are continuously added and the temperature is adjusted again after a holding time. When the curds are formed, they can be collected on a conveyor belt and the conveyor belt can transport the curds to an optional washing step (if needed) before being conveyed to further steps of processing into cheese, for example to a coo ker/st retch er for preparing a pasta filata cheese.

The continuous process of preparing cheese curds as compared to a vat process provides the advantage that the time for preparing cheese curds is reduced, and it is possible to have a better control of the composition of the curds with regard to the calcium content and the dry matter. Besides, with a continuous process, it is more easy to start and stop the process with a minimum of production waste.

For example, with the continuous process of the present invention, it is possible to prepare cheese curds, and also a cheese like mozzarella, in one day. On the contrary, processes for preparing cheese curds that uses a vat process take 10-14 days. For example, preparation of a mozzarella in a traditional process with traditional acidification, vat process and traditional block formation typically takes two weeks.

Further processing of the cheese curds into cheeses:

The cheese curds obtained may be stored before further processing, but may also be processed immediately while still fresh into cheese products. The cheese curds could for example be frozen and/or dried, and subsequently thawed and/or reconstituted before further processing into cheese products.

The cheese product prepared from the cheese curds obtained may for example be pasta filata cheeses, such as for example mozzarella cheese. However, the cheese curds may also be used for the preparation of other types of cheese products, such as soft cheeses, semi-soft cheeses, hard cheeses, extra hard cheeses and processed cheeses. In an embodiment, the cheese product obtained may be any of pasta filata cheeses, white cheeses, yellow cheeses, Cheddar, cheddar-like cheeses, halloumni, paneer, queso Fresco, cream cheeses, processed cheeses, gouda, gouda-like cheeses, and parmesan.

Hence, in an aspect the present invention relates to a method of preparing a cheese product comprising the steps of: a) providing cheese curds obtained by the method of preparing cheese curds according to the present invention b) optionally adding fat to the cheese curs to obtain fattened cheese curds; c) subjecting the cheese curds of step a) or b) to further processing to obtain a cheese product. Further processing of the cheese curds in step c) into for example a pasta filata cheese, e.g. mozzarella or mozzarella like cheeses, involves heating and stretching of the cheese curds obtained by the present invention.

The cheese curds may also be used for preparing other types of food products comprising cheese.

In an embodiment, the present invention relates to a method of preparing a pasta filata cheese, wherein the cheese curds obtained by the method of the invention is subjected to heating and stretching to obtain a pasta filata cheese. Preferably, the pasta filata cheese is mozzarella or a mozzarella like cheese.

Preferably the cheese curds used for preparing the pasta filata cheese comprises a fat content of 0.1% by weight or below, such that cheese curds with a low fat content is prepared. Preferably, the fat content is 0.05% by weight or below.

After separation of curds, but before heating and stretching, the cheese curds are mixed with fat to obtain fattened cheese curds having a fat content of 5-30% by weight.

Hence, in a preferred embodiment, the milk derived feed used to prepare the cheese curds of the invention comprises a fat content of 0.1% by weight or below, and the cheese curds obtained are in step b) mixed with fat to obtain fattened cheese curds having a fat content of 5-30% by weight before subjecting the curds to heating and stretching.

In a particular preferred embodiment, the present invention relates to a method of preparing pasta filata cheese wherein no acidifying agents or acid producing microorganisms are added during the method, and wherein the method comprises the steps of: i) providing a milk derived feed that has not been subjected to any pH adjustment and has a fat content of 0.1% by weight; ii) subjecting the milk derived feed to ultrafiltration (UF) with an ultrafiltration membrane to provide a UF permeate and a UF retentate, and to obtain a protein content in the UF retentate of at least 10% by weight; iii) optionally subjecting the UF retentate to diafiltration (DF) with an ultrafiltration membrane to obtain a DF permeate and a DF retentate; iv) optionally diluting the UF retentate obtained in step ii) or the DF retentate obtained in step iii) with a liquid to obtain a protein content in the diluted UF retentate or the diluted DF retentate in the amount of 5- 18 % by weight; v) adjusting the temperature of the UF or DF retentate or diluted UF or DF retentate to a temperature of 4 to 15°C; vi) adding one or more coagulating enzyme(s) to the temperature adjusted UF retentate or DF retentate of step v) and storing for at least 30 minutes; vii) heating the mixture of step vi) to at temperature in the range of 25°C to 60°C for a time period sufficient to coagulate the mixture and obtain cheese curds and whey; viii) separating the cheese curds from whey; ix) mixing the cheese curds with fat to obtain fattened cheese curds having a fat content of 5 to 30% by weight; x) subjecting the fattened cheese curds to heating and stretching to obtain a pasta filata cheese.

The fat added in step ix) may for example be a cream comprising 40% to 85% fat or may be a vegetable fat. Preferably, cream is added. The fat is typically added to obtain a fat content in the range of 5 to 30% by weight.

Suitable vegetable fats are rape seed oil, palm oil, coconut oil, sunflower oil and other neutral flavoured vegetable oils.

In an embodiment, minerals, lactose, acid and moisture may also be added in step ix) together with fat. Minerals, including sodium chloride, may be added in an amount of 0.1-2.5% by weight of the cheese curds, preferably 1-1.5% by weight. Lactose may also be added during step ix). Lactose added may for example be 0.1-1.5% by weight of the cheese curds, such as 0.3-0.8% by weight. Dependent on the functional properties wanted in the cheese obtained from the curds, lactose and/or minerals may be added since lactose and minerals control functionalities such as browning, stretching and melting. Moisture may for example be added in an amount of 0-10% by weight dependent on the product wished obtained, such as 3-6% by weight. Acids may for example be added in an amount of 0.5 to 3% by weight.

When the curd particles in step x) is heated and stretched, the curds are heated to a temperature of 55°C to 90°C, preferably 60 to 75°C, and mechanically stretched into a homogenous plastic mass. The equipment for heating/stretching is equipment common in the art, such as single or twin screw stretcher/extruder type device or steam jacketed and/or infused vessels equipped with mechanical agitation. The heating is performed either by use of direct heating or indirect heating by steam.

The heated and stretched cheese is transferred into moulds for forming and shaping the cheese obtained. The form may be any shape, such as sheets, shreds, blocks, dices, or any other shapes. Afterwards, the cheese is cooled by a rapid cooling step. The cooling can be done by various cooling methods and the present invention should not be limited to the cooling method. The cooling may for example be by rapid brine solution, cold water, ice water or cold air.

In a further embodiment, the present invention provides a mozzarella or mozzarella-like cheese product produced by the method of preparing a cheese product according to the invention.

Also, an embodiment of the invention provides a soft cheese, semi-soft cheese, hard cheese, extra hard cheese product or processed cheese produced by the method of preparing a cheese product according to the invention.

It should be noted that embodiments and features described in the context of one of the aspects of the present invention also apply to the other aspects of the invention.

All patent and non-patent references cited in the present application are hereby incorporated by reference in their entirety. The invention will now be described in further details in the following non-limiting examples.

Examples

Example 1: Calcium removal after ultrafiltration

An example was made to show that the calcium content in a milk derived feed is reduced by subjecting the milk derived feed to i) ultrafiltration and subsequent dilution to a targeted protein concentration.

Skim milk (fat-free milk) having a fat content of 0.05-0.08% by weight, calcium content of 1100-1400 mg/kg and protein content of 3.5-3.7% by weight was subjected to ultrafiltration (UF) with the ultrafiltration UFPHT spiral wound membrane (DA60PP) supplied by Alfa Laval AB. The membrane has a cut-off value of 20.000 Da.

The calcium content is measured using X-ray flourescence spectroscopy from Rigaku Ltd. The protein content, dry matter, fat content and moisture content are measured using the FoodScan™ Dairy analyser using near infrared transmission technology (NIT).

In this example, the initial milk derived feed (skim milk) was concentrated 6 times (CF=6). In the next step, RO water (RO processed UF permeate) was used to dilute the obtained UF retentate having a protein content of 21-23% by weight to a protein content of 10% by weight. The temperature of the skim milk was 8°C and this temperature was maintained during the ultrafiltration step. The UF retentate is cooled to a temperature of 5 to 10°C and chymosin (ChyMax® from Christian Hansen A/S, Horsholm, Denmark) was added (5-50 ml coagulating enzyme per 100 kg milk) to the cooled UF retentate and the mixture stored at the cooling temperature (5-10°C) for 180 minutes.

The UF retentate after adding chymosin and after cold storage was heated to a temperature of 45°C for a period of time of around 0.1 seconds to coagulate the mixture and obtain cheese curds and whey. The coagulated cheese curds (curd particles) were separated from the whey by use of a continuous separator in the form of a decanter. The dry matter content in the cheese curds obtained was around 42% by weight.

The cheese curds were further processed into a pasta filata cheese, e.g. mozzarella or mozzarella-like cheese involving mixing the obtained curds with other required ingredients (23% fat, 1.3% NaCL, 1% acid and 4-5% water), heating, stretching of the cheese and finally cooling and forming the cheese obtained. Figure 1 shows a flow sheet of the method of preparing a pasta filata cheese where the milk derived feed has been subjected to ultrafiltration according to example 1.

The mozzarella produced in this example has approximately 48% by weight moisture, 20-30% by weight fat and about 5000 mg calcium per kg cheese. The protein content is 21-23% by weight and therefore the calcium content is about 0.021- 0.023 g per g protein.

In figure 4, the browning/blister color of a cheese after exposure to heat treatment is shown, i.e. browning during melting.

Figure 4C shows a cheese with golden blister color, where figure 4B shows a dark brown blister color and figure 4A shows a black blister color. The blister color of a cheese made according to example 1, i.e. where the cheese has been obtained using a milk derived feed that has been subjected to ultrafiltration (UF) and dilution of the UF retentate to a 10% protein content, is the blister color shown in figure 4B, i.e a dark brown blister color. Figure 4A shows the browning of a heat treated cheese that has not been subjected to ultrafiltration, but otherwise the process parameters of example 1 are the same. The color of the blisters of a cheese where the milk feed has not been subjected to ultrafiltration is black.

Hence, the blister color when using a UF retentate as compared to using skim milk for preparing cheese curds results in an improvement in blister color. The most optimal blister color is golden (shown in figure 4C).

The blister size obtained with the method shown in example 1 (UF only) is 6-12 mm, while the blister size obtained without UF is larger than 12 mm. Hence, the blister size is reduced using UF as compared to using skim milk for preparing a cheese. The optimal blister size is 1.5-3 mm.

The functional properties of a cheese can also be measured by the browning area after heat treatment. This is shown in figure 5.

In figure 5, the browning area of figure 5C is 20-30%, the browning area of figure 5B is 50-60%, while the browning area of figure 5A is more than 60%. The browning area of a cheese obtained as in example 1 is shown in figure 5B and is 50-60%, while a cheese obtained without UF is shown in figure 5A and is more than 60%.

Example 2 - Calcium removal after ultrafiltration and diafiltration

This example was made to show that the calcium content in a milk derived feed is reduced by subjecting the milk derived feed to i) ultrafiltration and ii) diafiltration.

Skim milk (fat-free milk) having a fat content of 0.05-0.08% by weight, calcium content of 1100-1400 mg/kg and protein content of 3.5-3.7% by weight was subjected to ultrafiltration (UF) and then diafiltration (DF) both with the ultrafiltration UFPHT spiral wound membrane (DA60PP) supplied by Alfa Laval. The membrane has a cut-off value of 20.000 Da. The calcium content is measured using X-ray flourescence spectroscopy from Rigaku Ltd. The protein content, dry matter, fat content and moisture is measured using the FoodScan™ Dairy analyser using near infrared transmission technology (NIT).

In this example, the initial milk derived feed was concentrated 3 times (CF=3) with ultrafiltration, i.e. to a protein content of 10.5-11.1% by weight. In the next step, the UF retentate was diafiltered using RO water (RO processed UF permeate) keeping the protein concentration constant at 10% by weight.

The temperature of the skim milk was, and also during ultrafiltration/diafiltration, 8°C. The DF retentate is cooled to a temperature of 5 to 10°C and chymosin (ChyMax® from Christian Hansen A/S, Horsholm, Denmark) is added (5-50 ml coagulating enzyme per 100 kg milk) to the cooled DF retentate and is stored at the cooling temperature (5-10°C) for 180 minutes. The DF retentate after adding chymosin and after cold storage is heated to a temperature of 45°C for a period of time of around 0.1 seconds to coagulate the mixture and obtain cheese curds and whey.

The coagulated cheese curds (curd particles) were separated from the whey by use of a continuous separator in the form of a decanter. The dry matter content in the cheese curds obtained was around 42% by weight.

The cheese curds were further processed into a pasta filata cheese, e.g. mozzarella or mozzarella-like cheese involving mixing the obtained curds with other required ingredients (as in example 1), heating, stretching of the cheese and finally cooling and forming the cheese obtained. Figure 2 shows a flow sheet of the method of preparing a pasta filata cheese where the milk derived feed has been subjected to ultrafiltration and diafiltration to a protein content of 10% by weight according to example 2.

The mozzarella produced in this example has approximately 45% by weight moisture, 25-30% by weight fat and about 4000 mg calcium per kg cheese. The protein content is 21-23% by weight and therefore the calcium content is 0.017- 0.019 g per g protein.

The browning/blister color of a cheese made according to example 2 is shown in figure 4C as golden which is the blister color wished obtained. Hence, a cheese made from cheese curds prepared from using a UF and DF treated milk derived feed has improved functional properties in the form of blister color as compared to when the milk derived feed has only been UF treated.

The blister size obtained with the method shown in example 2 is 1.5-3 mm, i.e. within the desired range. Hence, the blister size is reduced using UF and DF as compared to using skim milk and UF alone for preparing a cheese.

In figure 5, the browning area after heat treatment is shown. A cheese obtained according to example 2 has a browning area of 20-30% (figure 5C) which is the browning area wished to be obtained. Further, the process applied to make cheese in example 2 also results in improved functionalities as compared to the process applied to make cheese in example 1 (according to the consumer acceptance panel tests) in terms of meltability, stretchability, browning and mouthfeel.

Example 3 - Calcium removal after ultrafiltration, dilution and diafiltration

This example was made to show that the calcium content in a milk derived feed is reduced by subjecting the milk derived feed to i) ultrafiltration and ii) diafiltration with varied protein concentration in the UF step.

Skim milk (fat-free milk) having a fat content of 0.05-0.08% by weight, calcium content of 1100-1400 mg/kg and protein content of 3.5-3.7% by weight was subjected to first ultrafiltration (UF) and then diafiltration (DF) both with the ultrafiltration UFPHT spiral wound membrane (DA60PP) supplied by Alfa Laval. The membrane has a cut-off value of 20.000 Da. The calcium content is measured using X-ray flourescence spectroscopy from Rigaku Ltd. The protein content, dry matter, fat content and moisture is measured using the FoodScan™ Dairy analyser using near infrared transmission technology (NIT).

In this example, the initial milk derived feed was concentrated 6 times (CF=6) with ultrafiltration to a protein content of 21-23% by weight. In the next step, the UF retentate was diluted with RO water (RO processed UF permeate) to a protein content of 10% by weight. Subsequently, the diluted UF retentate was diafiltered using RO water while keeping the protein concentration constant at 10%.

The temperature of the skim milk was, and also during ultrafiltration/diafiltration, 8°C. The DF retentate is cooled to a temperature of 5 to 10°C and chymosin (ChyMax® from Christian Hansen A/S, Horsholm, Denmark) is added (5-50 ml coagulating enzyme per 100 kg milk) to the cooled DF retentate and is stored at the cooling temperature (5-10°C) for 180 minutes.

The DF retentate after adding chymosin and after cold storage is heated to a temperature of 45°C for a period of time of around 0.1 seconds to coagulate the mixture and obtain cheese curds and whey. The coagulated cheese curds (curd particles) were separated from the whey by use of a continuous separator in the form of a decanter. The dry matter content in the cheese curds obtained was around 42% by weight.

The cheese curds were further processed into a pasta filata cheese, e.g. mozzarella or mozzarella-like cheese involving mixing the obtained curds with other required ingredients (as in example 1), heating, stretching of the cheese and finally cooling and forming the cheese obtained. Figure 3 shows a flow sheet of the method of preparing a pasta filata cheese where the milk derived feed has been subjected to ultrafiltration, dilution of the UF retentate and diafiltration to a protein content of 10% by weight according to example 3.

The mozzarella produced in this example has approximately 45% by weight moisture, about 15% by weight fat and about 4000 mg calcium per kg cheese. The protein content is 21-23% by weight and therefore the calcium content is 0.017-0.019 g per g protein.

The browning/blister color of cheeses made according to example 3 is shown in figure 4C and is as the cheese applied with the method of example 2 golden. Golden is the blister color wished obtained. Hence, a cheese made from cheese curds prepared from using a UF and DF treated milk derived feed has improved functional properties in the form of blister color as compared to when the milk derived feed has only been UF treated.

The blister size obtained with the method shown in example 3 is 1.5-3 mm, i.e. within the desired range. Hence, the blister size is reduced using UF and DF as compared to using skim milk and UF alone for preparing a cheese.

In figure 5, the browning area after heat treatment is shown. A cheese obtained according to example 3 has a browning area of 20-30% (figure 5C). A browning area wished to be obtained is about 20-30%.

Further, the process applied to make cheese in example 3 also results in improved functionalities as compared to the process applied to make cheese in example 1 (according to the consumer acceptance panel tests), in terms of meltability, stretchability, browning and mouthfeel.

Example 4: Sensoric evaluation of cheese made from curds having low calcium content versus a high calcium content.

An example was made to show the sensoric parameters of a mozzarella cheese made from curds having a low calcium content and from curds having a high calcium content.

Curds having a low calcium content is obtained by subjecting a milk derived feed to ultrafiltration and diafiltration before curd making according to example 2 or 3. The curds having a high calcium content is curds that have not been ultrafiltration or diafiltration.

The sensoric evaluation was made with a panel of 8 trained panelists. The sensory panel was trained to evaulating apperance and functional properties of a cheese. The following parameters of the mozzarella made with curds comprising a low and high calcium content was evaluated:

Appearance - colour (scale 1-5). A score of 1-2.5 is considered good, while a higher scope is considered not good.

Appearance - size (scale 1-5). A score of 1-2.5 is considered good, while a higher scope is considered not good.

Appearance - brown area (scale 1-5). A score of 1-2.5 is considered good, while a higher scope is considered not good.

Melting - (scale 0-15). Better the higher the score.

Oiling - (scale 0-15). A score of 5-10 is good.

Stretch - (scale 0-30). Better the higher the score.

Smooth - (scale 0-15). Better the higher the score.

Elasticity - (scale 0-15). A score of 7.5-12.5 is good.

Firm - (scale 0-15). Better the lower the score.

Crumbliness - (scale 0-15). Better the lower the score.

Off-flavour - (scale 0-15). Better the lower the score.

The result of the sensoric evaluation is showed in figure 6. Lca_MS refers to a mozzarella prepared from a curd having low calcium content and prepared using medium speed during the stretching. Hca_MS refers to a mozzarella prepared from a curd having a high calcium content using medium speed during the stretching. The medium speed refers to a speed of the stretcher being 50 rpm of the auger whereas low speed would be 20 rpm and high speed would be 80 rpm.

Claims

33 Claims

1. A method of preparing cheese curds wherein no acidifying agents or acid producing microorganisms are added during the method, and wherein the method comprises the following steps: i) providing a milk derived feed that has not been subjected to any pH adjustment; ii) subjecting the milk derived feed to ultrafiltration (UF) with an ultrafiltration membrane to provide a UF permeate and a UF retentate and to obtain a protein content in the UF retentate of at least 10% by weight; iii) optionally subjecting the UF retentate to diafiltration (DF) with an ultrafiltration membrane to obtain a DF permeate and a DF retentate; iv) optionally diluting the UF retentate obtained in step ii) or the DF retentate obtained in step iii) with a liquid to obtain a protein content in the diluted UF retentate or the diluted DF retentate in the amount of 5-18 % by weight; v) adjusting the temperature of the UF or DF retentate or diluted UF or DF retentate to a temperature of 4 to 15°C; vi) adding one or more coagulating enzyme(s) to the temperature adjusted UF retentate or DF retentate of step v) and storing for at least 30 minutes; vii) heating the mixture of step vi) to at temperature in the range of 25°C to 60°C for a time period sufficient to coagulate the mixture and obtain cheese curds and whey; viii) optionally separating the cheese curds from the whey.

2. The method according to claim 1, wherein the milk derived product in step i) is adjusted to a temperature of 2 to 15°C.

3. The method according to any of the claims 1 to 2, wherein the milk derived feed is selected from the group consisting of whole milk, low-fat milk, reduced fat milk, fat-free milk, reconstituted milk powder, heat treated milk, raw unfiltered milk, homogenized milk, mineral reduced milk, whey protein reduced milk, micellar casein isolate, micellar casein concentrate, and combinations thereof. 34

4. The method according to any of claims 1 to 3, wherein the milk derived feed is milk from mammals, such as cows, buffalos, goats, sheep, yaks, pigs, horses, ewes, mares, or mixtures thereof.

5. The method according to any of the claims 1 to 4, wherein the milk derived feed comprises fat in an amount of 0.1% by weight or less.

6. The method according to any of the claims 1 to 5, wherein the method comprises subjecting the UF retentate to diafiltration (DF) with an ultrafiltration membrane to obtain a DF permeate and a DF retentate.

7. The method according to any of the claims 1 to 6, wherein the calcium content in the UF retentate of step ii) or DF retentate of step iii) has been reduced by 30- 50% by weight as compared to the calcium content in the milk derived feed.

8. The method according to any of the claims 1 to 7, wherein the calcium content in the UF retentate of step ii) is 0.030g calcium per gram protein or less.

9. The method according to any of claims 1 to 8, wherein the cheese curds and whey obtained in step vii) are separated.

10. A method of preparing a cheese product comprising the steps of: a) providing cheese curds obtained by the method according to any of the claims 1 to 9; b) optionally adding fat to the cheese curds to obtain fattened cheese curds; c) subjecting the cheese curds of step a) or b) to further processing to obtain a cheese product.

11. The method according to claim 10, wherein the cheese product obtained is selected from the group consisting of soft cheeses, semi-soft cheeses, hard cheeses, extra hard cheeses and processed cheeses.

12. The method according to any of the claims 10 and 11, wherein the further processing of the cheese curds in step c) is heating and stretching to obtain a pasta filata cheese.

13. The method according to claim 123, wherein

- the milk derived feed used in the method of preparing cheese curds according to any of claims 1 to 9 comprises a fat content of 0.1% by weight or below; and - the cheese curds provided in step a) are in step b) mixed with fat to obtain fattened cheese curds having a fat content of 5-30% by weight before subjecting the curds to heating and stretching in step c).