Method for treating milk

Abstract

A method of treating milk comprising the steps of: a homogenization step in which the milk is maintained at a temperature of less than about 60 DEG C; and a high pressure treatment step wherein the milk is subjected to an elevated pressure of greater than about 350 MPa during the high pressure treatment step wherein the elevated pressure of the high pressure treatment step does not cause the temperature of the milk to increase beyond a limiting temperature of about 60 DEG C.

Description

[0001] This application is a divisional application of Chinese Patent Application No. 201680039283.8, filed July 1, 2016, entitled "A method of processing milk". TECHNICAL FIELD

[0002] The present invention relates generally to a method of processing milk and milk products processed by the method. BACKGROUND Raw milk generally contains microorganisms / pathogens that can be unsafe for human consumption. Methods of processing raw milk to produce milk for human consumption with safe pathogenic levels are known. These methods, known as pasteurization, involve exposing the milk to high temperatures.

[0003] The most common pasteurization method involves heating the milk to a temperature of about 72.5°C for about 15 seconds to produce milk for human consumption with safe pathogenic levels with a shelf life of about 14 days. Milk produced by this method is often referred to simply as pasteurized milk, fresh milk or fresh pasteurized milk.

[0004] Ultra-heat pasteurization (UHT) processing of milk involves pasteurizing the milk at a temperature in excess of 135°C for a period of about 4 seconds to produce milk known as UHT milk, which has a relatively stable shelf life. Pasteurizing milk at a temperature of about 121°C to produce milk known as extended shelf life (ESL) milk, which has a shelf life of about 21 to 31 days.

[0005] The temperatures required for pasteurizing milk result in significant denaturation of milk proteins and enzymes, and changes in some sensoric properties of the milk as the heat processing increases. As a result, the nutritional quality of the milk is reduced by pasteurization, with the degree of reduction increasing as the processing temperature increases. Thus, there is a trade-off between nutritional value and shelf life, with pasteurized milk having a higher nutritional quality and a shorter shelf life than ESL or UHT milk. The short shelf life of pasteurized milk makes it difficult to transport and market in some markets, particularly in markets where the consumers of the milk are located in areas without significant dairy processing industries. These types of markets often only offer ESL or UHT milk, which is nutritionally deficient but has a long shelf life.

[0006] Accordingly, there is a need to produce milk that has a high nutritional value by preserving key proteins and enzymes and has an extended shelf life.

[0007] The reference in this specification to any prior publication (or information derived from it), or to any matter which is known, is not, and should not be taken as an acknowledgment or admission or any form of suggestion that the prior publication (or information derived from it) or known matter forms part of the common general knowledge in the field of endeavour to which this specification relates. SUMMARY The present invention seeks to provide methods and products having improved characteristics and performance.

[0008] According to a first aspect, the present invention provides a method for processing milk, comprising the steps of: a homogenization step, wherein the milk is maintained at a temperature below about 60°C; and a high pressure treatment step, wherein the milk is subjected to an elevated pressure above about 350 MPa, wherein during the high pressure treatment step, the elevated pressure of the high pressure treatment step does not cause an increase in the temperature of the milk above a limit temperature of about 60°C.

[0009] According to another aspect, the present invention provides the method according to the first aspect, wherein the elevated pressure of the high pressure treatment step causes an increase in the temperature in the milk such that during the high pressure treatment step, the temperature of the milk is increased to at least about 45°C.

[0010] According to another aspect, the present invention provides the method according to the first aspect, wherein the elevated pressure of the high pressure treatment step causes an increase in the temperature in the milk such that during the high pressure treatment step, the temperature of the milk is increased to about 50°C to about 55°C.

[0011] According to another aspect, the present invention provides the method according to the first aspect, wherein during the high pressure treatment step, the milk is subjected to an elevated pressure of about 500 MPa to about 750 MPa.

[0012] According to another aspect, the present invention provides the method according to the first aspect, wherein the milk is subjected to an elevated pressure of about 600 MPa.

[0013] According to another aspect, the present invention provides the method according to the first aspect, wherein the milk is subjected to an elevated pressure for a period of time in the high pressure treatment step such that the level of pathogens in the milk is reduced to a level that is substantially safe for human consumption.

[0014] According to another aspect, the present invention provides the method according to the first aspect, wherein the milk is subjected to an elevated pressure for a period of about 3 minutes or less or about 4 minutes or less in the high pressure treatment step.

[0015] According to another aspect, the present invention provides the method according to the first aspect, further comprising the step of pre-cooling the milk to an initial temperature prior to the high pressure treatment step, wherein the initial temperature is selected such that the temperature of the milk does not exceed 60°C during the high pressure treatment step.

[0016] According to another aspect, the present invention provides the method according to the preceding aspect, wherein the initial temperature is selected such that the temperature of the milk increases to a range of about 50°C to about 55°C during the high pressure treatment step.

[0017] According to another aspect, the present invention provides the method according to the preceding aspect, wherein the initial temperature is about 33°C to about 37°C.

[0018] According to another aspect, the present application provides the method according to the first aspect, wherein the high pressure treatment step is performed by packaging the milk into a sealed container and immersing the sealed container into a fluid, wherein the fluid is subsequently pressurized such that the milk is subjected to an elevated pressure.

[0019] According to another aspect, the present application provides the method according to the first aspect, wherein the temperature of the fluid prior to pressurization is about the same as the initial temperature.

[0020] According to another aspect, the present application provides the method according to the first aspect, further comprising the step of subjecting the milk to UV treatment and / or ozone treatment and / or centrifugal bacteria removal.

[0021] According to another aspect, the present application provides the method according to the first aspect, wherein the method is used to treat milk obtained from a bovine animal, a sheep animal, a goat animal, a bubaline animal, or a cardinal animal.

[0022] According to another aspect, the present application provides the method according to the first aspect, wherein the method further comprises the step of cooling the milk to a temperature below about 4°C after the high pressure treatment step.

[0023] According to another aspect, the present application provides the method according to the first aspect, wherein the method further comprises the step of standardizing the milk to a certain fat content.

[0024] According to another aspect, the present application provides the method according to the first aspect, wherein the method is completed within about 72 hours of obtaining the milk from the animal or within about 48 hours of obtaining the milk from the animal.

[0025] According to a second aspect, the present application provides a method for treating milk, comprising the steps of: (a) obtaining milk from an animal and storing the milk at a temperature of about 0°C to about 4°C; (b) clarifying the milk; and (c) homogenizing the milk at a temperature of about 50°C and about 55°C; and (d) loading the milk into a sealed container; and (e) cooling the milk to an initial temperature; and (f) high pressure treating the homogenized milk, wherein the packaged milk is immersed into a fluid, subjected to an elevated pressure of above about 500 MPa; and (g) cooling the packaged milk to a temperature below about 4°C after the high pressure treatment step, wherein the initial temperature is selected such that the temperature of the milk increases to about 50°C to about 55°C during the high pressure treatment step.

[0026] According to a third aspect, the present application provides milk produced by any of the preceding aspects.

[0027] According to another aspect, the present application provides the milk according to the third aspect, wherein the milk has a shelf life of about 60 days to about 90 days.

[0028] According to one aspect, the present invention provides a method for processing milk, wherein the method includes the steps of: a homogenization step; and a high-pressure treatment step, wherein the milk is subjected to increased pressure.

[0029] Advantageously, compared with milk produced by conventional methods, the methods described above can produce milk with reduced pathogen levels, while providing improved nutritional value, sensory characteristics and shelf life. Brief description of the attached diagram The exemplary embodiments will become apparent from the following description, taken in conjunction with the accompanying drawings, of at least one preferred but non-limiting embodiment given by way of example only.

[0030] Figure 1 A flowchart of the method according to the present invention is shown.

[0031] Preferred implementation scheme In the accompanying drawings incorporated to illustrate the features of the exemplary embodiments, the same reference numerals are used throughout the drawings to identify the same parts.

[0032] Reference Figure 1 A flowchart illustrating a method for processing milk according to an embodiment of the present invention is provided. This method uses high pressure instead of pasteurization to remove bacteria and other pathogens from the milk. Using high pressure to process the milk allows the method to be carried out at a lower temperature than conventional pasteurization methods, thereby avoiding the degradation of certain proteins and enzymes associated with high-temperature processing of milk. The described method can also produce milk with a longer stable shelf life than pasteurized milk. The described method also avoids certain sensory changes to the milk that can occur due to pasteurization, particularly high-temperature pasteurization used in the production of UHT milk. Figure 1 The method includes the following steps: homogenizing the milk 1, cooling the milk to an initial loading temperature 2, transferring the milk to a sealed container 3, subjecting the milk in the sealed container to high pressure treatment step 4, and cooling the milk 5. However, certain optional steps may also be used in the method for processing milk described herein.

[0033] In this example implementation, raw milk is typically obtained by milking animals on a farm and, where feasible, cooled to a temperature of about 0°C to about 4°C as quickly as possible after milking. The pre-cooled milk can then be transported to a processing facility, where it can be stored in large vats at temperatures of about 0°C and about 4°C for processing.

[0034] The stored milk can then be passed through a clarifier to remove some foreign material and help minimize any possible sedimentation effects during subsequent milk homogenization.

[0035] The milk can then be subjected to a pre-heat step, in which the milk can be pre-heated to about 45°C and about 60°C, and preferably in the range of about 50°C and 55°C. Once the milk is pre-heated, the milk can be subjected to a homogenization step 1, in which the milk is homogenized while the temperature of the milk is maintained in the range of about 45°C and 60°C, and preferably in the range of about 50°C and 55°C. Homogenizing the milk at temperatures below about 45°C can induce deleterious effects in the milk, such as premature spoilage and the precipitation of white blood cells and epithelial cells. If the milk is heated to temperatures above about 60°C or about 58°C, phosphatase and the denaturation of casein and whey proteins can begin to occur, thereby reducing the nutritional quality of the milk. It has been found that maintaining the temperature of the milk in the range of about 50°C to 55°C during homogenization will buffer the milk from the deleterious effects experienced by the milk outside the range of about 45°C to about 60°C.

[0036] Homogenization of the milk will reduce the size of the fat globules in the milk and will disperse the reduced globules evenly throughout the milk. In this step, the milk is passed through small orifices under pressure to reduce the size of the fat globules and disperse them evenly throughout the remainder of the milk. The homogenization step 1 can be performed while the temperature of the milk is above about 25°C (i.e., above ambient temperature) and below about 60°C. In certain preferred embodiments, the homogenization step can be performed at a temperature of about 45°C to about 55°C.

[0037] After homogenization, the milk can be delivered to a temperature-controlled equilibration tank 2. The equilibration tank is configured to reduce the temperature of the milk below the range of 45°C to 60°C, or the preferred range of about 50°C to about 55°C. The equilibration tank is also configured to maintain the temperature of the milk above the initial loading temperature of the downstream high-pressure treatment step. After the temperature control of the milk as it passes through the equilibration tank 2, the milk can be transferred to a filling head. In certain embodiments, the equilibration tank can be located at a higher elevation than the filling head, such that the milk can flow under the influence of gravity to the transfer head.

[0038] The filling head dispenses the milk into individual packages 3, which can subsequently be sealed. The packages can be PET bottles, glass bottles, pouches, or any other suitable packaging.

[0039] The packaged milk can then be subjected to a high-pressure treatment step 4. In the high-pressure treatment step, the packaged milk is immersed in a fluid (e.g., water) within a high-pressure treatment chamber and exposed to elevated pressure. As the pressure within the high-pressure treatment chamber is increased, the fluid uniformly exerts hydrostatic pressure on the packaged milk. It has been found that subjecting the packaged milk to elevated pressure for a determined period of time can inactivate certain pathogens in the milk, thereby producing milk having a level of pathogens that is substantially safe for human consumption. It has also been found that the high-pressure treatment of the milk results in a more stable shelf life of the milk than pasteurized milk, enabling the milk to be transported to markets that are too far away for pasteurized milk to reach before the shelf life expires.

[0040] The elevated pressure applied to the milk in the high pressure treatment step can be on the order of 350 MPa to about 1500 MPa, although other pressures can be used. Higher pressures can require the milk to be exposed to the elevated pressure for a shorter period of time as compared to lower pressures, resulting in a higher throughput of milk during the overall process step. However, higher pressures can require more expensive equipment and involve higher associated operating costs than lower pressures. Similarly, lower pressures can require the milk to be exposed to the elevated pressure for a longer period of time, which in some cases can impact the commercial viability of the process. In one example embodiment, the high pressure treatment step exposes the packaged milk to an elevated pressure of about 600 MPa for about 3 minutes to inactivate certain pathogens within the milk. Conducting the high pressure treatment step can be beneficial to avoid higher pressures that can complicate the process and increase costs. It has also been found that this pressure produces milk with pathogen levels that are substantially safe for human consumption within a time frame of about 3 minutes. A time frame of about 3 minutes is beneficial because longer time frames can reduce the commercial viability of the high pressure treatment step in a batch operation as compared to other sterilization methods, although in some embodiments, a treatment time of 4 minutes or about 5 minutes is acceptable. However, it should be understood that the exact time required to reduce pathogen levels in the high pressure treatment step can be a function of the nature of the milk being treated. For example, milk with a higher pathogen load can require a longer treatment time of high pressure treatment to sufficiently reduce pathogen levels. Similarly, milk with a relatively lower load of pathogens can require a shorter treatment time of high pressure treatment to achieve sufficient pathogen mortality such that a high pressure treatment of less than 600 MPa pressure can be used to achieve sufficient pathogen mortality in about 3 minutes or less. In certain non-limiting embodiments, it has been found that an elevated pressure of about 500 MPa to about 750 MPa in the high pressure treatment step has been found to produce acceptable results within an acceptable time frame, although it should be understood that certain parameters, such as the initial pathogen load of the milk and the types of pathogens present in the milk, can impact the operating parameters of the high pressure treatment step. In some embodiments, the milk can be subjected to an elevated pressure for a short time frame of about 2 minutes or less or about 1 minute or less or less than about 45 seconds.

[0041] The initial loading temperature of the fluid in the high pressure treatment step can be selected to increase the mortality rate of certain pathogens in the milk to make the milk safer for human consumption. The loading temperature can also take into account the temperature increase that can occur in the high pressure treatment chamber due to the elevated pressure. Without wishing to be bound by theory, it is expected that for approximately every 100 MPa increase in the chamber, the temperature increases by approximately 3°C to 4°C. Thus, a loading temperature of approximately 33°C to approximately 37°C can be selected as the temperature in the high pressure treatment chamber at approximately 600 MPa, such that when the treatment chamber is pressurized from atmospheric to 600 MPa, the temperature can increase from 33°C to 37°C to approximately 50°C to 55°C. Keeping the temperature of the milk at 50°C to 55°C will advantageously avoid temperatures of approximately 60°C or approximately 58°C, at which certain nutritional components of the milk can begin to denature. Performing the high pressure treatment at a relatively high temperature, such as approximately 50°C to approximately 55°C, can be beneficial to help promote the mortality rate of pathogens in the milk, particularly pathogens that can exhibit a certain level of high pressure resistance, while keeping the temperature below approximately 58°C or approximately 60°C to avoid a decrease in certain nutritional and / or organoleptic properties of the milk. However, it has been found that performing the high pressure treatment on the milk at a temperature of approximately 45°C or lower can provide acceptable results, however, lower temperatures can require the high pressure treatment step to be performed for a longer period of time or at a higher pressure. Surprisingly, it has been found that the combination of elevated pressure and elevated temperature below approximately 60°C in a commercially viable process compared to pasteurization results in milk having a substantially safe level of pathogens for human consumption. The milk produced by this process can also have improved organoleptic and nutritional properties compared to pasteurized milk, and can also have a longer shelf life.

[0042] It is additionally noted that it can be beneficial to perform the high pressure treatment step on the milk with a temperature increase above an approximate lower limit of approximately 45°C or approximately 50°C to help reduce the pathogen level, but below an approximate upper limit of approximately 60°C to avoid or minimize a decrease in the nutritional value and / or organoleptic properties of the milk.

[0043] It has also been found that the temperature regime of the process for treating the milk can help certain spore-forming pathogens, such as Bacillus cereus (B. cereus), to be inactivated. It has been found that the temperature regime of the process can help to inactivate B. cereus, which can be present in the milk, by increasing the mortality rate of the B. cereus in the milk. The temperature regime of the process can also help to inactivate B. cereus by increasing the mortality rate of the B. cereus in the milk to a level that is substantially safe for human consumption. bacillus cereus) to allow the germination of the spores so that the germinated spores can be inactivated by the elevated pressure of the high pressure treatment step. For example, it has been found that a temperature regime that results in an initial loading temperature of about 33°C to 37°C, which results in a milk temperature of about 50°C to about 55°C, in a high pressure treatment step operating at an elevated pressure of about 600 MPa, helps to germinate certain spore-forming pathogens so that the germinated spores can be more easily inactivated by the elevated pressure of the high pressure treatment step. Furthermore, during the initial phase of the high pressure treatment step, the pressure is elevated to the specified elevated pressure. During the initial phase of the pressure elevation, these lower pressures in combination with the temperature regime of the present method can further help to germinate spore-forming pathogens, resulting in easier pathogen inactivation at the elevated pressure. In this way, the temperature and pressure regime, if the high pressure treatment step can result in an increased mortality rate of certain spore-forming pathogens, such as Bacillus cereus.

[0044] It has been found that homogenizing milk at a temperature of about 45°C and 60°C, preferably at about 50°C and 55°C, followed by subjecting the homogenized milk to a high pressure treatment step, the resulting milk can show substantially reduced pathogen levels, as well as improved nutritional value, shelf life and sensory properties, compared to milk produced by pasteurization.

[0045] In certain preferred embodiments, the temperature of the fluid used to pressurize the high pressure treatment step chamber can be pre-heated to the same or similar temperature as the initial loading temperature of the milk in the high pressure treatment step. By pre-heating the fluid, the elevated pressure will cause the temperature of the fluid to increase to about the same temperature as the temperature of the packaged milk will be increased by the elevated pressure. In this way, the heat transfer between the fluid and the packaged milk will be minimized for the reasons described above, thereby simplifying the process of controlling the temperature of the packaged milk to about 45°C to about 60°C, or about 50°C to about 55°C.

[0046] After the high pressure treatment of the milk, the packaged milk is at a relatively high temperature, for example, about 50°C to 55°C, such that cooling 5 can be required for subsequent storage and transportation. The cooling can be achieved by any suitable cooling method step, for example, by spraying cold water over and around the packaged milk to reduce the temperature of the milk to below 4°C. Another cooling method step can be a flash cooling step in which the packaged milk is subjected to a reduced pressure environment, thereby reducing the temperature of the packaged milk. Cooling the milk by these methods can result in a rapid reduction in temperature, limiting the time the milk is exposed to high temperatures, which can result in an extension of the shelf life of the milk. Once the internal temperature of the milk is below about 4°C, the milk can be transferred to a refrigerated room for storage at below 4°C until the milk is subsequently distributed to the market.

[0047] Milk treated for a sufficient time by the high pressure treatment step can exhibit substantially reduced pathogen levels. The pathogen levels can be at or near levels that are safe for human consumption. The pathogen levels can be the same or similar to pathogen levels of milk treated by pasteurization.

[0048] In some cases, depending on the initial load of pathogens present in the milk and the type of pathogens present in the milk, further treatment in addition to the high pressure processing step can be required to reduce the pathogen levels in the milk. In some embodiments, UV treatment or ozone treatment of the milk can be performed, if necessary, to further reduce the pathogen levels of the milk. In some embodiments, a centrifugal bacteria removal step can also be performed prior to the high pressure treatment step to reduce the pathogen load of the milk. For example, when the milk being treated has a particularly high initial load of pathogens, it can be advantageous to use one of these additional treatment steps prior to the high pressure treatment step.

[0049] The methods as described herein can be used to treat milk that has been standardized to produce treated milk having various levels of fat and SNF, such as skim milk.

[0050] As used herein, milk refers to the liquid produced by the mammary glands of a mammal. Milk is an emulsion or colloid of butterfat globules in a water-based fluid containing agglomerations of dissolved carbohydrates with proteins and minerals. The methods described herein can be used to treat milk from any animal, including: cows, sheep, goats, antelope, and deer animals. The milk treatment process methods described herein are completed within 72 hours or preferably within 48 hours of obtaining the milk from these animals. Milk treated within such time frames can exhibit improved sensory properties and can further exhibit increased shelf life.

[0051] Milk produced by the methods for treating milk described herein can have certain advantages over milk treated by other methods, such as pasteurization or ESL milk, for example, in preserving the nutritional content of the milk and producing milk having improved sensory properties. In addition, milk treated by the methods for treating milk as described herein can exhibit a shelf life of more than about 45 days, or about 60 to 90 days or more, thus exceeding the shelf life of pasteurized milk. This extended shelf life can allow the milk to be shipped to distant markets by economical methods, such as sea transport, so that milk having good nutritional and sensory properties can reach distant markets at an economical cost.

[0052] Many modifications will be apparent to those skilled in the art without departing from the scope of the present application.

Claims

1. A method for processing milk, comprising the following steps: The homogenization step, in which the milk is kept at a temperature below 60°C; and, A high-pressure treatment step, wherein during the high-pressure treatment step, the milk is subjected to an increased pressure of more than 350 MPa, wherein the increased pressure of the high-pressure treatment step does not cause the milk temperature to rise above a limit temperature of 60°C, wherein during the high-pressure treatment step, the increased pressure of the high-pressure treatment step causes the milk temperature to rise to at least about 45°C, and wherein the high-pressure treatment step is carried out by packaging the milk into a sealed container and immersing the sealed container in a fluid, wherein the fluid is subsequently pressurized, thereby subjecting the milk to the increased pressure.

2. The method of claim 1, wherein during the high-pressure processing step, the increased pressure of the high-pressure processing step causes the milk temperature to rise to 50°C to 55°C.

3. The method of claim 1 or 2, wherein during the high-pressure processing step, the milk is subjected to an increased pressure of 500 MPa to 750 MPa.

4. The method of any of the preceding claims, wherein the milk is subjected to an increased pressure of 600 MPa.

5. The method of any of the preceding claims, wherein the milk is subjected to high pressure for 3 minutes or less or 4 minutes or less in the high-pressure treatment step.

6. The method of any of the preceding claims further includes the step of precooling the milk to an initial temperature prior to the high-pressure processing step, wherein the initial temperature is selected such that the temperature of the milk does not exceed 60°C during the high-pressure processing step.

7. The method of any of the preceding claims, wherein the initial temperature is selected such that the temperature of the milk rises to a range of 50°C to 55°C during the high-pressure processing step.

8. The method of any of the preceding claims, wherein the initial temperature is between 33°C and 37°C.

9. The method of any of the preceding claims, wherein the temperature of the fluid prior to pressurization is the same as the initial temperature.

10. A method for processing milk, comprising the following steps: (a) Obtaining milk from animals and storing milk at temperatures between 0°C and 4°C; and, (b) Clarified milk; and, (c) Homogenize the emulsion at temperatures of 50°C and 55°C; and, (d) Pour the milk into a sealed container; and, (e) Cool the milk to its initial temperature; and, (f) High-pressure homogenized milk, wherein packaged milk is immersed in a fluid and subjected to elevated pressures exceeding 500 MPa; and, (g) After the high-pressure processing step, the packaged milk is cooled to a temperature below 4°C. The initial temperature is selected such that the temperature of the milk rises to 50°C to 55°C during the high-pressure processing step.

Images