WO2022136561A1

WO2022136561A1 - Method of treating cheese curds

Info

Publication number: WO2022136561A1
Application number: PCT/EP2021/087319
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 treating cheese curds with increased control of the calcium content. In particular, the present invention relates to a method of treating cheese curds by immersing cheese curds into a liquid selected from one or more food grade acids and one or more food grade calcium chelating agents to reduce the calcium content in the cheese curds. 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 TREATING CHEESE CURDS

Technical field of the invention

The present invention relates to a method of treating cheese curds to obtain increased control of the calcium content. In particular, the present invention relates to a method of treating cheese curds by immersing cheese curds into a liquid selected from one or more food grade acids and one or more food grade calcium chelating agents to reduce the calcium content in the cheese curds. 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. When preparing these types of cheeses, it is desired to obtain a product with good melting and stretching properties.

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 the 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 before or during the coagulation step 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 (acids and acid producing microrganisms) before or during preparation of 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. The cheese prepared using a vat process will also have a variation from vat to vat, and will need advanced and expert control since the 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 where a starting milk having a temperature of 5°C to 25°C is acidified 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° to 55°C to initiate coagulation and produce curd particles within the flow device.

However, an improved method of preparing or treating cheese curds to obtain an improved control of calcium removal would be advantageous, and in particular a more efficient method of treating or preparing cheese curds without the use of acidifying agents to the starting milk or during the coagulation step would be advantageous. Further, a method of preparing or treating 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 treating cheese curds to obtain an improved control of the calcium level.

In particular, it is an object of the present invention to provide a method of treating cheese curds that solves the above mentioned problems of the prior art.

Thus, one aspect of the invention relates to a method of treating cheese curds comprising the following steps: i) providing cheese curds that have been separated from whey; ii) cutting the cheese curds; iii) immersing the cut cheese curds from step ii) into a liquid selected from the group of one or more food grade acids and one or more food grade calcium chelating agents, wherein the liquid if being a food grade acid, is having a pH in the range of 2.0 to 5.0 and wherein food grade calcium chelating agents are non-acidic calcium chelating agents; iv) separating the cheese curds treated in step iii) from the liquid.

A further aspect of the invention relates to providing a method of preparing a cheese product, wherein the cheese curds obtained by the method of treating cheese curds according to invention are subjected to further processing to obtain a cheese product selected from the group consisting of soft cheeses, semi-soft cheeses, hard cheeses, extra hard cheeses and processed cheeses. Brief description of the figures

Figure 1 shows a flow sheet of the process according to the invention after formation of cheese curds.

Figure 2 shows shows the process of immersing cheese curds in a bath of acid or EDTA.

Figure 3 shows the process of continuously immersing cheese curds in a bath of acid or EDTA.

Figure 4 shows the blister color of cheeses. Figur 4A shows the blister color of a cheese prepared from cheese curds that have not been subjected to immersion in a bath of acid or calcium chelating agent. Figure 4B shows the blister color of a cheese prepared from cheese curds that have been subjected to immersion in a bath of acid or calcium chelating agent.

Figure 5 shows the browning area of cheeses. Figur 5A shows the browning area of a cheese prepared from cheese curds that have not been subjected to immersion in a bath of acid or calcium chelating agent. Figure 5B shows the browning area of a cheese prepared from cheese curds that have been subjected to immersion in a bath of acid or calcium chelating agent.

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 haivng 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.

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

Providing cheese curds that have been separated from whey

In step i) of the method of treating cheese curds, cheese curds are provided that has been separated from whey. When preparing cheese curds, a milk feed is subjected to a coagulation step such that curd particles are formed. The curd particles are flowing in liquid whey. It is important for the present method of treating cheese curds that the free flowing liquid whey is removed before further processing.

After the coagulation step to obtain cheese curds and whey, a part of the whey obtained may be bound in the obtained cheese curds as moisture while another part of the whey is free flowing liquid whey. Therefore, it is not possible to remove all whey from the cheese curds since a part of the whey is bound in the curd structure. The whey obtained after curd formation may therefore be divided into whey bound in the curds (15-35% by weight) and free flowing liquid whey (65- 85% by weight). The term "total whey" refers in the context of the present invention to both the whey bound in cheese curds as moisture and free flowing liquid whey.

In step i) of the method of treating cheese curds of the present invention, the cheese curds provided therefore have been separated from free flowing liquid whey. Hence, in an embodiment of the invention the cheese curds provided comprises essentially no free flowing liquid whey. The term "essentially no" refers in the context of the present invention to that the cheese curds obtained only comprise free flowing liquid whey that is "attached" or "sticking" to the cheese curds after a separation step. For example, after decanting, the free flowing liquid whey is removed, but a small amount of free flowing liquid whey may be attached to the curds after decanting. Hence, in an embodiment of the invention, the cheese curds provided comprise 5% by weight or less of free flowing liquid whey. More preferably, the cheese curds provided comprise 3% by weight or less of free flowing liquid whey. Most preferably, the cheese curds provided comprises 2% by weight or less of free flowing liquid whey.

In a further embodiment of the invention, the cheese curds provided have been separated from whey such that at least 65% by weight of the total whey after curd formation has been removed. It is important to remove sufficient whey from the curd before further processing in order to enable further calcium removal from the curd in the subsequent process steps. Preferably, at least 70% by weight of the total whey after curd formation is removed from the curds. Hence, in another embodiment, of the invention, the cheese curds provided comprise an amount of total whey in the range of 15 to 35% by weight, preferably an amount of total whey in the range of 20 to 25% by weight.

The coagulated cheese curd (curd particles) can be separated from the free flowing liquid whey by use of a separator, such as for example a decanter, a sieve, a filter or other means suitable for separation of curds from whey.

In a further embodiment of the present invention, the cheese curds provided do not comprise any pH adjusting agents. The cheese curds provided should preferably not comprise any pH adjusting agents. Hence, the cheese curds provided should not be prepared with the use of pH adjusting agents. Preparing the cheese curds with pH adjusting agents will lead to the pH adjusting agents being present in the cheese curds in the whey bound in the curd structure. Further, the whey separated may be of limited use if comprising pH adjusting agents.

The dry matter content of the cheese curds provided 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.

Cutting the cheese curds:

The cheese curds provided are in step ii) of the method of the invention cut into smaller pieces. The term "cutting" includes cutting, shredding, grating or other ways of cutting the cheese curds into smaller pieces. Cutting the curds into smaller pieces will increase the surface area of the curds such that when the curds are immersed into a liquid, selected from the group of one or more food grade acids and one or more food grade calcium chelating agents, an improved calcium removal effect is obtained. Cutting will provide a larger surface area and hence a larger area for the acid or calcium chelating agent to interact with.

Immersion of cheese curds

In step iii) of the present invention, the cheese curds provided are immersed into a liquid selected from the group consisting of one or more food grade acids and one or more food grade calcium chelating agents, wherein the liquid if being a food grade acid, is having a pH in the range of 2.0 to 5.0 and wherein food grade calcium chelating agents are non-acidic calcium chelating agents.

In the context of the present invention, when referring to immersion into a liquid, it may also be understood as immersion into a bath and these terms may be used interchangeable.

The term "food grade acid" refers in the context of the present invention to an acid suitable for human consumption. Examples of food grade acids are for example organic acids, such as citric acid, malic acid, tartaric acid, acetic acid, oxalic acid, lactic acid, tannic acid, glucono delta lactone, phosphoric acid and sulphuric acid and other food grade acids. Hence, one or more of these food grade acids may be used in step iii). Food grade acids may also be referred to as edible acids, and the terms are used interchangeably herein. Preferably, the one or more food grade acids used are one or more selected from the group of consisting of citric acid, lactic acid and acetic acid.

In an aspect of the present invention, the liquid, if comprising one or more food grade acids, is having a pH in the range of 2.0 to 5.0. More preferably, the pH is in the range of 2.5 to 4.5. A pH below 2.0 is not desired since the curd will be destroyed at such low pH values. Further, pH values above 5.0 are not desired, since when immersing curds in an acid bath with a pH above 5.0, it will take too long time to remove calcium and may not work at all.

When immersing the curds in a food grade acid, the acid will solubilize the calcium in the curds, release the calcium from the curds and draw calcium from the curds into the liquid. Hereby, the calcium content in the cheese curds is reduced. The lower the pH of the solution which the curds are immersed into, the more calcium is solubilized and removed from the curds. Further, calcium removal can be controlled by the period of time the cheese curds are immersed into the acid bath. The longer time the cheese curds are immersed into the food grade acid, the more calcium is removed. Hence, with the method according to the present invention, it is possible to control the calcium removal.

Further, when cutting the cheese curds into smaller pieces before immersion into an acid bath, the surface area of the cheese curds is increased such that solubilisation and drawing of calcium into the liquid is optimized. Hence, the cutting step before immersion into an acid bath makes the process faster, more efficient and more calcium can be removed.

The liquid the cheese curds may be immersed in according to the present invention, may besides from being one or more food grade acids also be one or more food grade calcium chelating agents.

The term "food grade calcium chelating agent" refers in the context of the present invention to a calcium chelating agent suitable for human consumption. Furthermore, the term calcium chelating agent may also be referred to as a calcium chelator and the terms may be used interchangeable. In the context of the present invention, the term calcium chelating agent refers to what is normally understood by a calcium chelating agent, i.e. a compound that forms very strong bonds to divalent metal ions (M²⁺), i.e. Ca²⁺, forming a complex.

The action of the calcium chelating agent is therefore different from the action of the food grade acid. The calcium chelating agent will bind calcium in the cheese curd such that calcium from the cheese curds is separated from the cheese curds into the liquid, i.e. leading to removal of calcium. The calcium removal can be controlled by the period of time the cheese curds are immersed into the liquid with one or more calcium chelating agents. The longer time the cheese curds are immersed into the liquid with one or more food grade calcium chelating agents, the more calcium is removed. Hence, with the method according to the present invention, it is possible to control the calcium removal.

Further, when cutting the cheese curds into smaller pieces before immersion into a liquid with one or more calcium chelating agents, the surface area of the cheese curds is increased such that the calcium chelating agent more efficiently can bind calcium. Hence, the cutting step before immersion into the calcium chelating agent makes the process faster, more efficient and more calcium can be removed.

In an aspect of the invention, the one or more calcium chelating agents are non- acidic chelating agents. Hence, the calcium chelating agent will not include chelating agents that also decrease the pH.

In a preferred embodiment, the one or more food grade calcium chelating agents are selected from the group consisting of ethylenediaminetetraacetic (EDTA), calcium disodium ethylenediaminetetraacetic (calcium disodium EDTA), disodium ethylenediaminetetraacetic (disodium EDTA), (monohydroxyethyl)ethylenediaminetriacetic acid, Dihydroxyethyl)ethylenediaminediacetic acid and any other chelating agent capable of binding calcium.

Preferably, the one or more food grade calcium chelating agents are selected from the group consisting of ethylenediaminetetraacetic (EDTA), calcium disodium ethylenediaminetetraacetic (calcium disodium EDTA), and disodium ethylenediaminetetraacetic (disodium EDTA). At neutral or alkaline pH, EDTA reacts with the calcium ion to form the highly water-soluble calcium-EDTA complex, CaEDTA.

The pH of the liquid with one or more food grade calcium chelating agents should therefore preferably have a neutral or slightly alkaline pH since the calcium chelating agent, such as EDTA, will not efficiently chelate calcium ions at low pH. Furthermore, the solubilisation of EDTA in water is decreased in an acidic environment.

Hence, in an embodiment of the present invention the liquid comprising one or more food grade calcium chelating agents has a pH of 6.4 or more and most preferably a pH of 6.7 or more. The temperature of the bath with one or more calcium chelating agents is not important for calcium removal and will typically be in the range of 4°C to 50°C.

The liquid comprising one or more food grade calcium chelating agents is typically obtained by dissolving a food grade calcium chelating agent in water. The concentration of the calcium chelating agent will be in an amount of at least 2% by weight. Typically, the concentration of the calcium chelating agent is in the range of 2 to 10% by weight, and preferably, the concentration of the calcium chelating agent is 2 to 6% by weight. At higher concentrations of the calcium chelating agent, it will be necessary to wash the curds after being immersed in the bath of the calcium chelating agent.

The temperature of the liquid comprising one or more food grade acids or one or more food grade calcium chelating agents is for example in the range of 4°C to 50°C. The temperature of the liquid is not a limiting factor of the present invention and can in principle be any temperature in the range of 4°C to 50°C. Preferably, the temperature of the liquid, which the cheese curds are immersed into, should not exceed 50°C in order to avoid the cheese curds sticking to each other and to achieve efficient calcium removal.

In a preferred embodiment of the invention, the temperature of the liquid, which the cheese curds are immersed into is in the range of 5°C to 40°C, more preferably 10°C to 30°C and even more preferably 10°C to 20°C. At temperatures below 10°C, calcium is removed, but there is a risk of not having efficient calcium removal.

The period of time the cheese curds are immersed into the liquid may vary a lot depending on which acid, pH or calcium chelating agent are used and depending on the amount of calcium wanted removed from the cheese curds. However, the cheese curds should preferably be immersed into the liquid for at least 1 minute to obtain removal of calcium, such as at least 5 minutes, and even more preferably at least 10 minutes.

In another embodiment of the invention, the cheese curds are immersed into the liquid for 1 minute to 10 hours, such as 5 minutes to 8 hours, more preferably 10 minutes to 6 hours and even more preferably 15 minutes to 4 hours.

In further embodiments of the invention, the cheese curds are immersed into the liquid having a temperature of 5°C to 40°C for at least 5 minutes, such as a temperature of 5°C to 40°C for 5 minute to 10 hours, such as a temperature of 5°C to 40°C for 10 minute to 6 hours. In another embodiment of the invention, the cheese curds are immersed into the liquid having a temperature of 10°C to 30°C for at least 5 minutes, such as a temperature of 10°C to 30°C for 5 minute to 10 hours, such as a temperature of 10°C to 30°C for 10 minute to 6 hours.

Separate the cheese curds from the liquid

In step vi) of the method of the present invention, the cheese curds are separated from the liquid they have been immersed into.

The cheese curds can be separated from the liquid by use of a separator, such as for example a decanter, a sieve, a filter or other means suitable for separation of curds from liquid.

The dry matter content in 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.

Further, the cheese curds obtained after immersion into a liquid selected from the group of one or more food grade acids and one or more food grade calcium chelating agents comprise a calcium content of 5000 to 12000 mg/kg curd. More preferably, the cheese curds obtained after immersion comprise a calcium content of 6000 to 10000 mg/kg, most preferably a calcium content of 7000 to 9000 mg/kg.

The calcium content in cheese curds before immersion (into a liquid selected from the group of one or more food grade acids having a pH in the range of 2.0 to 5.0 and one or more non-acidic food grade calcium chelating agents) is dependent of the method of preparing the cheese curds. However, if the curds are produced without addition of acids or chelating agents and without the use of membrane filtration, the calcium content will typically be in the range of 20000-25000 mg/kg. The calcium content is measured using X-ray fluorescence spectroscopy from Rigaku Ltd.

Continuous method:

According to an embodiment, the method of treating 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 treated.

The curds provided may for example be transported on a conveyor belt and transported to a bath comprising either one or more food grade acids or one or more food grade calcium chelating agents. After the "bath", the curds along with the liquid from the bath may be conveyed to a decanting process where curds and acid bath liquid are separated. The separated liquid comprising removed calcium may, for example, be subjected to reverse osmosis to remove calcium and returned to the bath. Further, the separation step to separate the curds from the liquid may be followed by an optional washing step of the curds (if needed) before the curds are conveyed to further steps of processing into cheeses, for example to a cooker/stretcher for preparing a pasta filata cheese.

The continuous process of treating cheese curds as compared to a vat process provides the advantage that it is possible to have a better control of the composition of the curds with regards 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.

Further processing of the cheese curds into cheeses

The cheese curds obtained after the method of treating cheese curds according to the present invention may be stored before further processing, but may also be processed immediately while still fresh into cheeses. 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 cheeses, such as soft, semi-soft, hard or extra hard cheeses and processed cheeses. Hence, the present invention relates in an aspect to a method of preparing a cheese product, wherein the cheese curds obtained from the method of treating cheese curds according to the present invention are subjected to further processing to obtain a cheese product selected from the group consisting of soft cheeses, semi-soft cheeses, hard cheeses, extra hard cheeses and processed cheeses.

In an embodiment, the cheese product prepared from the cheese curds treated according to the present invention is selected from the group consisting of pasta filata cheeses, white cheeses, yellow cheeses, Cheddar, cheddar-like cheeses, halloumi, paneer, Queso Fresco, cream cheeses, processed cheeses, gouda, gouda-like cheeses, and parmesan. The cheese curds of the present invention are in particular used for preparing pasta filata cheeses.

Further processing 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. Hence, an embodiment of the present invention also relates to a method wherein the cheese curds obtained by the method of treating cheese curds according to the invention are subjected to heating and stretching to obtain a pasta filata cheese.

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

The present invention also relates to a method of preparing a pasta filata cheese, wherein the cheese curds obtained by the method of treating cheese curds are 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 method of preparing a pasta filata cheese comprises: a) providing the cheese curds obtained by the method of treating cheese curds according to the present invention; b) optionally adding fat to the cheese curds to obtain fattened cheese curds; c) subjecting the cheese curds of step a) or step b) to heating and stretching to obtain a pasta filata cheese.

In some cases, it is desired to prepare cheese curds with a low fat content and then add fat when processing the curds into cheeses. Preparing cheese curds with a low fat content and adding fat later before processing the curds into cheese, will make the process more flexible and avoid loss of fat in the process. Further, using cheese curds with a low fat content and adding fat later in the process of cheese making will allow for using other types of fat than milk fat.

Preferably the cheese curds obtained by the method of treating cheese curd of the invention and used for preparing the pasta filata cheese comprise a fat content of 0.1% by weight or below. Preferably, the fat content is 0.05% by weight or below. 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.

The fat added may for example be a cream comprising 40% to 85% fat or may be a vegetable fat. Preferably, cream is added. Suitable vegetable fats are rape seed oil, palm oil, coconut oil, sunflower oil and other neutral flavoured vegetable oils. In the method of preparing a pasta filata cheese, minerals, lactose, acid and moisture may in an embodiment also be added 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 for example be added in the amount of 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 wanted 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 c) are 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 commonly used 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 pasta filata cheese is a mozzarella or mozzarella-like cheese product.

Method of preparing cheese curds for use in the invention:

In an embodiment, the present invention also relates to a method of preparing cheese curds to be provided in step i) of the method of treating cheese curds according to the present invention. In a preferred embodiment of the invention, the cheese curds provided for the method of treating cheese curds comprises no pH adjusting agents.

Therefore, it is an embodiment of the invention to provide cheese curds prepared by a method without the use of pH adjusting agents.

Hence, the present invention relates in an embodiment to the cheese curds provided in step i) are prepared by a method comprising the following steps: a) providing a milk derived feed that has not been subjected to any pH adjustment and adjusting the temperature of the milk derived feed to a temperature of 4°C to 15°C; b) adding one or more coagulating enzyme(s) to the temperature adjusted milk derived feed of step a) to obtain a mixture and storing for at least 30 minutes; c) heating the mixture of step b) to a temperature of 25°C to 60°C for a time period sufficient to coagulate the mixture and obtain cheese curds and whey; d) separating the cheese curds and whey.

Milk derived feed:

The milk derived feed may be based on milk from mammals, such as cows, buffalos, goats, sheep, yaks, pigs, camels, 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 to avoid loss of fat during the process. In the process of preparing the cheese curds of the invention, fat removed can be added later in the process, either to the cheese curds before or after immersion into the bath of acid and/or calcium chelating 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 (also referred to as 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 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.

As earlier mentioned, 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 coagulating enzyme, such as rennet. In other methods known in art, the coagulation is due to acidification or a combination of acidification and addition of coagulating enzymes. The whey obtained from enzyme-based precipitation of casein is typically referred to as sweet whey, and the whey obtained from acid precipitation of casein is typically referred to as acid whey or sour whey. Further, as disclosed earlier whey comprises both the free flowing liquid whey and whey bound in the curd structure. The combination of both free flowing liquid whey and whey bound in the curds structure is referred to as total whey. The whey removed in step d) is free flowing liquid whey.

Where acid whey have limited use, the sweet whey can be further processed into various products, i.e. preparation of whey protein products or lactose products.

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 denaturing heat treatment. It is therefore also preferred that the milk derived feed and the product stream from which the milk derived feed has been derived has 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 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 the embodiment of the present invention relating to the method of preparing cheese curds, the milk derived feed has not been subjected to any pH adjustment. Hence, no acidifying agents have been added, including both chemical acids and lactic 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, and preferably 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 addition of any acidifying agents to the milk derived feed or during the hydrolysis or coagulation process. In prior art, the preparation of cheese curds typically involves an acidification step during the preparation of curds, i.e. either by adding chemical acids or adding lactic acid producing bacteria, or both, before curd formation. However, in the method of the present invention, the inventors have surprisingly found that a controlled removal of calcium from cheese curds can be obtained by first preparing cheese curds and subsequently immersing the cheese curds that have been separated from whey into a liquid selected from one or more food grade acids having a pH in the range of 2.0 to 5.0 and one or more food grade calcium chelating agents wherein said food grade calcium chelating agents are non-acidic calcium chelating agents. Hence, it is possible to prepare cheese curds with a controlled removal of calcium, but without adding any acidifying agents to the milk derived feed or during the hydrolysis and coagulation step. Besides from obtaining a controlled removal of calcium, the present invention also provides the possibility to obtain whey that comprises no acidifying agents.

In the method of preparing cheese curds according to the present invention, it is important that the pH of the milk derived feed corresponds to the pH of fresh milk. Hence, in the method of the present invention, no acidifying agents or cultures are added before the curds are obtained. A pH adjustment of the milk derived feed to a pH below 6.5 results in initiation of unwanted gelation and precipitation in the milk derived feed. This is wished avoided. In addition, a high degree of acidification of the milk derived feed before or during the preparation of cheese curds can lead to excess calcium removal that could result in some deficiencies in the cheese obtained.

Hence, in a preferred embodiment of the present invention, the method comprises no addition of acidifying agents before the cheese curds are obtained. In the context of the present invention, the term "acidifying agent" refers both to chemical acids and lactic acid producing microorganisms. In particular, the method of the invention comprises no addition of acidifying agents to the milk derived feed, to the temperature adjusted milk derived feed, to the hydrolysis step (milk derived feed added coagulating enzyme) or during the coagulation step. In particular, the method of the invention comprises no addition of acidifying agents during steps a) to d) of the method according to the invention. 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 aspect of the invention, the temperature of the milk derived feed is, or is adjusted to be, in the range of 4°C to 15°C, preferably from 5°C to 10°C, and more preferably from 5°C to 8°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 coagulation is. Preferably, the temperature of the milk derived feed 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 coagulating 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 coagulating 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 in the 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 milk derived feed and 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 milk derived feed mixed with coagulating enzyme(s) is stored cold for 30 minutes to 48 hours before further processing. Preferably, the temperature adjusted milk derived feed mixed 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 enzymes cut 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 milk derived feed.

The milk derived feed mixed with coagulating enzymes 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 limit for the cold storing of the milk derived feed mixed with coagulating enzymes because the temperature is so low that coagulating does not occur and there are 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/are 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) com prises/com prise chymosin.

Rennet is a complex set of enzymes (when describing commercial products) produced in the stomachs 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 milk derived feed in an amount from 5 ml/100 kg liquid (milk derived feed) 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 milk derived feed is, after adding the coagulating enzyme(s) and after cold storage, heated 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. With the method of the present invention, the calcium content in cheese curds is reduced after the cheese curds are obtained. As mentioned earlier, calcium plays an important role in the clustering of casein micelles during the coagulation process. The effect of maintaining the calcium content during the preparation of cheese curds is therefore that a good and efficient network of casein is obtained during the coagulation process.

Preferably, the heating during the coagulation 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. Further, the cheese curds begin to stretch at high temperatures which is wished avoided at this point of 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. 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 milk derived feed mixed and 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. The heating is typically by using direct or indirect heating means to coagulate the protein and form coagulated curd particles. In the case of direct heating, steam can be injected into the flow of the liquid milk derived feed. 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 cheese curds obtained are suitable to be used in the method of treating cheese curds according to the present invention.

In a further aspect, the invention relates to a method of preparing and treating cheese curds comprising the following steps: a) providing a milk derived feed that has not been subjected to any pH adjustment and adjusting the temperature of the milk derived feed to a temperature of 4°C to 15°C; b) adding one or more coagulating enzyme(s) to the temperature adjusted milk derived feed of step a) to obtain a mixture and storing for at least 30 minutes; c) heating the mixture of step b) to a temperature of 25°C to 60°C for a time period sufficient to coagulate the mixture and obtain cheese curds and whey; d) separating the cheese curds and whey; e) cutting the cheese curds; f) immersing the cut cheese curds from step e) into a liquid selected from the group of one or more food grade acids and one or more food grade calcium chelating agents, wherein the liquid if being a food grade acid, is having a pH in the range of 2.0 to 5.0 and wherein food grade calcium chelating agents are non-acidic calcium chelating agents; g) separating the cheese curds treated in step f) from the liquid. The above mentioned method of preparing cheese curds may in an embodiment of the invention be prepared 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 while the temperature is 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 whey removed by transporting over a decanter or sieve or the like. The conveyor belt can then transport the curds to a bath of either one or more food grade acids or one or more food grade calcium chelating agents. After the "bath", the curds along with the liquid from the bath may be conveyed to a decanting process or sieve where curd and acid bath liquid is separated. This is followed by 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 use 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. The present invention in an embodiment also relates to a method of preparing pasta filata cheese comprising the steps of: a) providing a milk derived feed that has not been subjected to any pH adjustment and has a fat content of 0.1% by weight; b) adjusting the temperature of the milk derived feed to a temperature of 4 to 15°C; c) adding one or more coagulating enzyme(s) to the temperature adjusted milk derived feed of step b) to obtain a mixture and storing for at least 30 minutes; d) heating the mixture of step c) 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; e) separating the cheese curds and whey; f) cutting the cheese curds g) immersing the cheese curds obtained in step f) into a liquid selected from the group of one or more food grade acids and one or more foods grade chelating agents, wherein the liquid if being a food grade acid, is having a pH in the range of 2.0 to 5.0 and wherein food grade calcium chelating agents are non-acidic calcium chelating agents; h) separating the cheese curds treated in step g) from the liquid. i) mixing the cheese curds from step h) with fat to obtain fattened cheese curds having a fat content of 5 to 30% by weight; j) subjecting the fattened cheese curds to heating and stretching to obtain a pasta filata cheese.

The fat added in step i) 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 and lactose are also added in step i) 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 i). 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 of 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.

When the cheese curds in step j) are 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 commonly used in the art, such as single or twin screw stretcher/extruder type device or steam jacketed and/or infused vessels equipped with mechanical agitators.

The heated and stretched curd is transferred into moulds for forming and shaping the cheese obtained. The form may be any shape, such as sheets, shreds, blocks and dices. 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. The cooled cheese may optionally be shredded or formed in blocks.

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

Also, an embodiment of the invention provides a soft cheese, semi-soft cheese, hard cheese, or extra hard cheese product produced by the process of 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: Effect of calcium removal on cheese curds after immersion into acid bath

An example was made to show that the calcium content in cheese curds is reduced by immersing the cheese curds into an acid.

The cheese curds were obtained by providing skim milk (fat-free milk) having a fat content of 0.05-0.08% by weight, calcium content of 1100-1400 mg/L, protein content of 3.5-3.7% by weight and a pH around 6.7. The skim milk was cooled to a temperature of 5-10°C and chymosin (ChyMax® from Christian Hansen A/S, Horsholm, Denmark) was added (5-50 ml coagulating enzyme per 100 kg milk) and the mixture was stored at the cooling temperature (5-10°C) for 180 minutes.

The mixture was after adding chymosin and cold storage heated to a temperature of 45°C for 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 cheese curds obtained were shredded and immersed for 15 minutes into an acid bath of citric acid with 30% w/w concentration and a pH of 2.5 at the temperature of 10°C.

Afterwards, the curds were removed from the acid bath and immersed into process water for 10 minutes while the temperature was maintained 10°C. After this step, the curds were transported on a draining belt to remove excess water and then transported into a mixer to add other ingredients for making a cheese. Figure 1 shows a flow sheet of the process after formation of cheese curds. Figure 2 shows the process of immersing cheese curds into an bath of acid or EDTA. The cheese curds were further processed into a pasta filata cheese, e.g. mozzarella or mozzarella-like cheese involving heating and stretching of the cheese and finally cooling and forming the cheese obtained.

The final curd had a calcium content of 7000-9000 mg/kg. Hence, up to 70% of the calcium may be removed by this method.

In table 1 below, the calcium content in the cheese curds before and after immersion into the acid bath is shown. The calcium content is measured using X- ray fluorescence spectroscopy from Rigaku Ltd.

Table 1:

In figure 4A, is the blister color of a cheese obtained with curds that have not been immersed into a bath of acid according to example 1 or into a bath of calcium chelating agent according to example 2 shown. Figure 4A shows a cheese having a black blister color. A black blister color is not desired.

In figure 4B, is the blister color of a cheese obtained with curds that have been immersed into a bath of acid according to example 1 or calcium chelating agent according to example 2 shown. Figure 4B shows a cheese with a golden blister color. A golden blister color is desired.

The blister size of a cheese obtained with curds that have and have not been immersed into a bath of acid or calcium chelating agent is analysed because the blister size is also a parameter of the functional properties of a cheese.

The blister size of a cheese obtained with curds that have not been immersed into a bath of acid or calcium chelating agent was found to be more than 12 mm, while the blister size of a cheese obtained with curds that have been immersed into a bath of acid or calcium chelating agent was found to be 1.5-3 mm. Hence, the blister size of a cheese is reduced if the cheese curds used for preparing the cheese have been immersed into a bath of acid or calcium chelating agent. 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 5A is more than 60%, while the browning area of figure 5B is 20-30%. The browning area of a cheese obtained with cheese curds that have not been immersed into a bath of acid or chelating agent is shown in figure 5A and is more than 60%. On the contrary, the browning area of a cheese obtained with cheese curds that have been immersed into a bath of acid or chelating agent is shown in figure 5B and is more 20-30%.

Example 2: Effect of calcium removal on cheese curds after immersion into EDTA bath

An example was made to show that the calcium content in the cheese curds is reduced by immersing cheese curds into an EDTA solution.

The cheese curds were obtained by providing skim milk (fat-free milk) having a fat content of 0.05-0.08% by weight, calcium content of 1100-1400 mg/L, protein content of 3.5-3.7% by weight and a pH around 6.7. The skim milk was cooled to a temperature to 5-10°C and chymosin ((ChyMax® from Christian Hansen A/S, Horsholm, Denmark) was added (5-50 ml coagulating enzyme per 100 kg milk) and the mixture was stored at the cooling temperature (5-10°C) for 180 minutes.

The cheese curds obtained were shredded and immersed for 15 minutes in a solution of EDTA containing EDTA with a 5% w/w concentration, a pH of 7.0 and a temperature of 10°C. After this step, the curds were removed from the bath and immersed into process water for 10 minutes while the temperature was maintained 10°C. The curd after this step were transported on a draining belt to remove excess water and then transported into a mixer to add other ingredients for making a cheese. Figure 2 shows the process of immersing cheese curds in a bath of acid or EDTA.

The cheese curds were further processed into a pasta filata cheese, e.g. mozzarella or mozzarella-like cheese involving heating and stretching of the cheese and finally cooling and forming the cheese obtained.

The final curd had a calcium content of 7000-9000 mg/kg.

In table 2, is the calcium content in the cheese curds obtained shown before and after immersion into the acid bath. The calcium content is measured using X-ray fluorescence spectroscopy from Rigaku Ltd.

Table 2:

In figure 4A, the blister color of a cheese obtained with curds without being immersed into a bath of acid or calcium chelating agent is shown. Figure 4A shows a cheese having a black blister color. A black blister color is not desired.

In figure 4B, the blister color of a cheese obtained with curds that have been immersed into a bath of acid or calcium chelating agent is shown. Figure 4B shows a cheese with a golden blister color. A golden blister color is desired.

The blister size of a cheese obtained with curds that have not been immersed into a bath of acid or calcium chelating agent is more than 12 mm, while the blister size of a cheese obtained with curds that have been immersed into a bath of acid or calcium chelating agent is 1.5-3 mm. Hence, the blister size of a cheese is reduced if the cheese curds used for preparing the cheese have been immersed into a bath of acid or calcium chelating agent. The optimal blister size is 1.5-3 mm.

Example 3: Effect of calcium removal on cheese curds after continuous immersion into EDTA or acid bath

An example was made to show that the calcium content in cheese curds is reduced by continuously immersing the cheese curds into an EDTA solution or an acid bath.

The cheese curds obtained were immersed for 15 minutes into an bath of either citric acid or an EDTA solution as described in example 1 and 2. The temperature was 10°C. The curds were continuously passed through the bath using a perforated belt and the excess solution was washed and recycled for further use in the system. The curds were then transported on a draining belt to remove excess water and then transported into a mixer to add other ingredients for making a cheese. Figure 3 shows the continuous process of immersing cheese curds into a bath of acid or EDTA.

The cheese curds were further processed into a pasta filata cheese, e.g. mozzarella or mozzarella-like cheese involving heating and stretching of the cheese and finally cooling and forming the cheese obtained. The final curd had a calcium content of 7000-9000 mg/kg. The same blister color, blister size and browning area were obtained before and after immersion into a bath of acid or calcium chelating agent as for example 1 and 2.

Example 4: Effect of pH in the acid bath on removal of calcium

An example was made to show that the calcium removal in cheese curds immersed into an acid bath is dependent of the pH of the acid bath. The cheese curds were obtained as mentioned in example 1. The cheese curds obtained were shredded and immersed into different acid baths having different pH level.

The acid baths were made by adding 3500g of process water to a tank and adjusting the pH with 10% w/w citric acid. The pH was adjusted to:

- solution 1: neutral pH (no pH adjustment)

- solution 2: pH 3.5

- solution 3: pH 4.5

- solution 4: pH 5.5

The temperature of all 4 acid baths was 30°C.

900g of shredded curd was immersed into each solution/acid bath and the pH was maintained at the target pH during the immersion using a 10% citric acid solution. After 30 and 90 minutes of immersion respectively, 100 g of curd from each test tank was taken out and squeezed for excess water and chilled.

The calcium content was measured in the curds before immersion in acid bath and after 30 min. and 90 min. of soaking. The calcium content was measured using X-ray fluorescence spectroscopy from Rigaku Ltd.

In table 3 below is the amount of calcium measured in the different samples of curd shown.

Table 3: %-calcium in curds before and after being immersed into acid bath having different pH and immersion time

From table 3, it is shown that the calcium removal is increased when the pH level of the acid bath is decreased. Hence, using an acid bath having a pH below 5.0 will lead to an increased removal of calcium from the curds as compared to having a pH above 5.0. In addition, removal of calcium is increased when the immersion time is increased.

The blister color of a cheese obtained with curds without being immersed into an acid bath is shown in figure 4A. Figure 4A shows a cheese having a black blister color. A black blister color is not desired. Further, figure 4B shows the blister color of a cheese made with curds that have been immersed into an acid bath where at least 40% calcium has been removed. Hence, where the acid bath is at a pH in the range of 2.0-4.5. Figure 4B shows a cheese with a golden blister color. A golden blister color is desired.

Example 5: Sensoric evaluation of cheese made from curds having low calcium content versus a high clacium 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 immersion into an acid bath according to example 1 or by immersion into EDTA as disclosed in example 2. The curds having a high calcium content are curds that have not been immersed into a bath of acid or calcium chelating agent.

The sensoric evaluation was made with a panel of 8 trained panelists. The sensory panel was trained to evaulate apperance and functional properties of a cheese.

The following parameters of the mozzarella made with curds comprising a low and high calcium content were evaluated:

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

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

Appearance - brown area (scale 1-5). A score of 1-2.5 is considered good, while a higher score is considered not good. Melting - (scale 0-15T The better the higher the score.

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

Stretch - (scale 0-30\ The better the higher the score.

Smooth - (scale 0-15T The better the higher the score. Elasticity - (scale 0-15T A score of 7.5-12.5 is good.

Firm - (scale 0-15T The better the lower the score.

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

Off- flavour - (scale 0-15T The 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

37 Claims

1. A method of treating cheese curds comprising the following steps: i) providing cheese curds that have been separated from whey; ii) cutting the cheese curds; iii) immersing the cut cheese curds from step ii) into a liquid selected from the group of one or more food grade acids and one or more food grade calcium chelating agents, wherein the liquid if being a food grade acid, is having a pH in the range of 2.0 to 5.0 and wherein food grade calcium chelating agents are non-acidic calcium chelating agents; iv) separating the cheese curds treated in step iii) from the liquid.

2. The method according to claim 1, where the cheese curds provided do not comprise any pH adjusting agents.

3. The method according to any of claims 1 to 2, where the cheese curds provided comprise essentially no free flowing liquid whey.

4. The method according to any of the claims 1 to 3, wherein the cheese curds provided comprise an amount of total whey in the range of 15 to 35% by weight,

5. The method according to any of claims 1 to 4, wherein the cheese curds are immersed into the liquid in step iii) for 1 minute to 10 hours.

6. The method according to any of the claims 1 to 5, wherein the method is continuous.

7. The method according to any of the claims 1 to 6, wherein the one or more food grade acids are selected from the group consisting of citric acid, malic acid, tartaric acid, acetic acid, oxalic acid, lactic acid, tannic acid, glucono delta lactone, phosphoric acid and sulphuric acid and other food grade acids.

8. The method according to claim 1, wherein the one or more food grade calcium chelating agents are selected from the group consisting of 38 ethylenediaminetetraacetic (EDTA), calcium disodium ethylenediaminetetraacetic (calcium disodium EDTA), disodium ethylenediaminetetraacetic (disodium EDTA), (monohydroxyethyl)ethylenediaminetriacetic acid, (Dihydroxyethyl)ethylenediaminediacetic acid and any other chelating agent capable of binding calcium.

9. The method according to claim 1, wherein the cheese curds provided in step i) are prepared by a method comprising the following steps: a) providing a milk derived feed that has not been subjected to any pH adjustment and adjusting the temperature of the milk derived feed to a temperature of 4°C to 15°C; b) adding one or more coagulating enzyme(s) to the temperature adjusted milk derived feed of step a) to obtain a mixture and storing for at least 30 minutes; c) heating the mixture of step b) to a temperature of 25°C to 60°C for a time period sufficient to coagulate the mixture and obtain cheese curds and whey; d) separating the cheese curds and whey.

10. The method according to claim 9, wherein essentially all free flowing liquid whey is removed from the curds in step d).

11. The method according to any of the claims 9 to 10, wherein no acidifying agents are added during step a) to d).

12. A method of preparing a cheese product wherein the cheese curds obtained from the method according to any of claims 1 to 11 are subjected to further processing to obtain a cheese product selected from the group consisting of soft cheeses, semi-soft cheeses, hard cheeses, extra hard cheeses and processed cheeses.

13. The method according to claim 12, wherein the the cheese product is selected from the group consisting of pasta filata cheeses, white cheeses, yellow cheeses, Cheddar, cheddar-like cheeses, halloumi, paneer, queso fresco, cream cheeses, processed cheeses, gouda, gouda-like cheeses, and parmesan.

14. The method according to claim 12, wherein the cheese curds obtained by any of the claims 1 to 11 are subjected to heating and stretching to obtain a pasta filata cheese.