Method for determining gelation or thickening of milk

Abstract

To provide a method for determining gelation or thickening in milk.SOLUTION: The present invention provides a method for determining gelation or thickening that may occur during storage of milk based on a degree of casein decomposition in the milk. The degree of casein decomposition may be represented by an amount of change in a casein decomposition product content or an amount of change in a casein content in the milk. Further, the amount of change in the casein decomposition product content may be a value represented based on the casein decomposition product content after a storage test of the milk at 15°C or higher. The amount of change in the casein content may be a value represented based on the casein content of the milk after the storage test at 15°C or higher. The present invention also provides a method for analyzing the milk including performing the determination method. The present invention also provides a method for producing the milk including performing the determination method.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a method for determining gelation or thickening of milk, and more particularly to a method for determining gelation or thickening of milk using specific indicators.

Background Art

[0002] In the manufacturing process of milk such as cow's milk, a sterilization treatment is performed before filling into a container. Gels may form during storage in the sterilized milk. Regarding the formation of such gels, for example, Non-Patent Document 1 below describes that proteolysis causes undesirable gelation in pasteurized milk or ultra-high temperature sterilized milk.

Prior Art Documents

Non-Patent Documents

[0003]

Non-Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] Milk and other dairy products sold as products that can be stored at room temperature are stored for a long period of time, and thus it is required that their quality be maintained over the storage period.

[0005] The present inventors have found that gelation or thickening may occur for the first time when milk is stored at room temperature for a long period of time. The gelation or thickening may be observed for the first time, for example, when stored at room temperature for about six months.

[0006] Although it is considered desirable to conduct an analysis regarding the occurrence of such gelation or thickening and to develop dairy products that prevent such gelation or thickening, since a long time is required until such gelation or thickening occurs, it is desirable to improve the efficiency of such analysis and development from the perspective of time. For example, regarding the gelation or thickening that occurs after long-term storage as described above, if it is possible to predict the presence or absence of occurrence in dairy products in a short period of time, it is considered very useful for the analysis and development of milk that is stored for a long time. Therefore, an object of the present invention is to provide a method for determining gelation or thickening in dairy products.

Means for Solving the Problems

[0007] The present inventors have found that gelation or thickening that can occur in dairy products can be determined by a specific method.

[0008] That is, the present invention provides the following. [1] A method for determining gelation or thickening that can occur during storage of dairy products based on the degree of casein degradation in the dairy products. [2] The method for determination according to [1], wherein the degree of casein degradation is the amount of change in the content of casein degradation products or the amount of change in the casein content in the dairy products. [3] The method for determination according to [2], wherein the amount of change in the content of casein degradation products is a value represented based on the content of casein degradation products after a storage test of the dairy products at 15°C or higher. The method for determination according to [2]. [4] The method for determination according to [2], wherein the amount of change in the casein content is a value represented based on the casein content after a storage test of the dairy products at 15°C or higher. The method for determination according to [2]. [5] The storage test is a storage test in which dairy products are stored at 15°C or higher for 5 days or more. The method for determination according to [3] or [4]. [6] The method for determination according to any one of [1] to [5], which is a prediction of gelation or thickening of the dairy products when the dairy products are stored at room temperature for 1 month or more. [7] The determination method according to any one of [1] to [6], wherein the milk is milk packed in an aseptic container. [8] A method for analyzing milk, comprising performing the determination method according to any one of [1] to [7]. [9] A method for manufacturing milk, comprising performing the determination method according to any one of [1] to [7].

[10] The determination method according to any one of [1] to [7], the analysis method according to [8], or the manufacturing method according to [9], wherein the milk is a product that can be stored at room temperature. [Advantages of the Invention]

[0009] According to the present invention, it is possible to determine gelation or thickening that may occur in milk, particularly gelation or thickening that occurs when stored for a long period of time. According to the present invention, the gelation or thickening can be determined by a short-term test. Thereby, it is possible to improve the efficiency of analysis related to the gelation or thickening or the development of milk products in which the gelation or thickening does not occur. Note that the effects of the present invention are not limited to the effects described in this paragraph, and may be any of the effects described in this specification. [Brief Description of the Drawings]

[0010]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

[0011] The preferred embodiments of the present invention will be described below. However, the present invention is not limited to only the following preferred embodiments and can be freely changed within the scope of the present invention. Note that the present invention will be described in the following order. 1. Method for determining gelation or thickening of milk 1.1 Milk 1.2 Gelation and thickening 1.3 Amount of change 1.3.1 Amount of change in the content of casein degradation products 1.3.1.1 Amount of change in the content of casein degradation products based on the difference in storage temperature 1.3.1.2 Amount of change in the content of casein degradation products based on the difference in the presence or absence of storage 1.3.2 Amount of change in the casein content 1.3.2.1 Amount of change in the casein content based on the difference in storage temperature 1.3.2.2 Amount of change in the casein content based on the difference in the presence or absence of storage 1.4 Storage treatment 1.5 Determination 2. Method for analyzing milk 3. Method for producing milk 4. Examples <Test example> <Production example>

[0012] 1. Method for determining gelation or thickening of milk

[0013] The present invention provides a method for determining gelation or thickening of milk, particularly a method for determining gelation or thickening that may occur during storage of milk. The determination method may be performed based on the degree of casein degradation in milk. The degree of casein degradation in milk is useful for predicting gelation and thickening that may occur during storage of the milk.

[0014] 1.1 Milk The milk may be, in particular, milk derived from mammals, more particularly milk derived from dairy livestock. The mammals may be, for example, bovine animals such as cows, goats, water buffalo, or sheep, but are not limited thereto. The milk product contains milk protein, and particularly contains at least casein. The degree of casein decomposition can be used as an index for determining whether gelation or thickening occurs during long-term storage of the milk product.

[0015] The milk product may be liquid milk. That is, the determination method of the present invention may be a determination method for the occurrence of gelation or thickening of liquid milk in liquid milk. The milk product may be, for example, cow's milk, special cow's milk, pasteurized goat's milk, adjusted milk, low-fat milk, fat-free milk, or processed milk, but is not limited thereto. For example, the milk product may be cow's milk.

[0016] Specific examples of the composition of the milk product to which the determination method of the present invention is applied will be described below. The determination method of the present invention is particularly suitable for predicting gelation or thickening that may occur in milk products having the following composition.

[0017] The non-fat milk solid content ratio of the milk product may be, for example, 8% by mass or more based on the mass of the milk product. The solid content ratio may be, for example, 35% by mass or less, preferably 20% by mass or less, and more preferably 15% by mass or less.

[0018] The water content ratio of the milk product may be, for example, 65% by mass or more based on the mass of the milk product, preferably 75% by mass or more, and more preferably 80% by mass or more. The water content ratio may be, for example, 92% by mass or less, preferably 90% by mass or less, and more preferably 85% by mass or less.

[0019] The protein content ratio of the milk product may be, for example, 1% by mass or more based on the mass of the milk product, preferably 2% by mass or more, and more preferably 3% by mass or more. The protein content ratio may be, for example, 15% by mass or less, preferably 10% by mass or less, and more preferably 7% by mass or less.

[0020] The casein content ratio of the milk may be, for example, 0.8% by mass or more, preferably 1.6% by mass or more, and more preferably 2.4% by mass or more, based on the mass of the milk. The casein content ratio may be, for example, 12% by mass or less, preferably 8% by mass or less, and more preferably 5.6% by mass or less.

[0021] The lipid content ratio of the milk may be, for example, 0% by mass or more, preferably 1.5% by mass or more, and more preferably 3% by mass or more, based on the mass of the milk. The lipid content ratio may be, for example, 6% by mass or less, preferably 5% by mass or less, and more preferably 4.5% by mass or less.

[0022] The milk may be milk packed in an aseptic container. The milk packed in an aseptic container is obtained by separately sterilizing the milk and the container in which the milk is contained, and then filling the milk into the container in a sterile environment. The determination method of the present invention is suitable for predicting gelation or thickening in the milk contained in the aseptic container. In addition, the milk packed in an aseptic container can be stored for a long time, and the determination method of the present invention is particularly suitable. The container may be a resin container, a paper container, or a glass container or a metal container. The resin of the resin container may be a polyester resin (such as PET resin), a polyolefin resin (such as PP resin or PE resin), or a polystyrene resin (such as PS resin). The paper container may be, for example, a container formed of a laminate of a paper layer and a resin layer. The resin layer may be a barrier resin layer that particularly prevents the penetration of milk. The resin layer may be, for example, a layer containing the resin described above, or a layer containing other resins. The type of the container may be appropriately selected by those skilled in the art, and the container packing method can also be appropriately selected by those skilled in the art according to, for example, the type of the container.

[0023] The milk may be a product that can be stored at room temperature. Products that can be stored at room temperature are often stored for a long time, and the determination method of the present invention is particularly suitable. In this specification, room temperature may be, for example, 15°C to 30°C. The milk may be a product assumed to be stored in such a temperature range.

[0024] The milk may be milk that has been subjected to a sterilization treatment. For example, it may be milk that has been subjected to an indirect heating type sterilization treatment such as a plate type or a tubular type, or milk that has been subjected to a direct heating type sterilization treatment such as an infusion type or an injection type. The determination method of the present invention is suitable for predicting gelation or thickening that may occur when such sterilized milk is stored for a long time. The sterilization treatment may be, for example, a sterilization treatment at 120°C to 150°C for 1 to 6 seconds. These sterilization treatment temperatures and sterilization treatment times apply to both the indirect heating type sterilization treatment and the direct heating type sterilization treatment described above. For example, the sterilization treatment may be a plate type sterilization treatment at 120°C to 150°C for 1 to 6 seconds. The sterilization treatment may also be an infusion type sterilization treatment at 120°C to 150°C for 1 to 6 seconds.

[0025] Before the sterilization treatment, the milk may be subjected to a preliminary heating treatment. The temperature of the heating treatment may be, for example, 65°C to 95°C, particularly 70°C to 90°C. Also, the time of the heating treatment may be, for example, 30 seconds to 10 minutes, particularly 30 seconds to 5 minutes. By this heating treatment, the protein contained in the milk is denatured, thereby preventing burning during the sterilization treatment.

[0026] 1.2 Gelation and thickening In the determination method of the present invention, the gelation determined may mean the formation of a gel containing a casein degradation product. The gel generated by the gelation determined in the determination method of the present invention may be, for example, a gel confirmed as a precipitate in milk.

[0027] In one embodiment, the gelation may be such that, before the gelation occurs, for example, 90% by volume or more, particularly 95% by volume or more, and more particularly almost the entire amount of the milk can pass through an 80-mesh filter, but due to the gelation, for example, 10% by volume or more, more particularly 20% by volume or more, even more particularly 30% by volume or more, 40% by volume or more, or 50% by volume or more of the milk no longer passes through the filter.

[0028] The thickening determined in the determination method of the present invention may mean the thickening of the milk itself. In particular, the thickening may mean an increase in the viscosity measurement value. For example, the viscosity of the milk may be, before thickening, for example, 5 mPa·s or less, particularly about 3 to 4 mPa·s. The viscosity of the milk may, with thickening, become, for example, more than 5 mPa·s, particularly 6 mPa·s or more, more particularly 8 mPa·s or more. The viscosity of the milk may further increase according to the storage period and may become, for example, 10 mPa·s or more, 20 mPa·s or more, or 30 mPa·s or more. The thickening may be thickening associated with gelation. The viscosity is measured using a tuning fork vibration viscometer (SV-100, A&D Company, Limited) after adjusting the temperature of the sample to 10°C ± 2°C.

[0029] 1.3 Amount of change The degree of the casein decomposition may be, for example, the amount of change in the content of casein degradation products or the amount of change in the casein content in the milk. Prediction of the occurrence of gelation or thickening based on the degree of the casein decomposition may be performed, for example, visually based on measurement results indicating the content of casein degradation products or the casein content such as the results of SDS-PAGE or HPLC, or may be performed based on values representing these amounts of change, as will be described below. More specific examples of these amounts of change will be described below.

[0030] 1.3.1 Amount of change in the content of casein degradation products

[0031] The change amount of the content of the casein hydrolyzate may be a value represented based on the content of the casein hydrolyzate after the storage test of the milk at a predetermined temperature. The predetermined temperature in the storage test may preferably be a temperature of 15°C or higher, more preferably 20°C or higher, even more preferably 25°C or higher, and in some embodiments may be 30°C or higher, or 35°C or higher. The predetermined temperature in the storage is preferably 50°C or lower, more preferably 45°C or lower, even more preferably 40°C or lower. Storing milk at such a temperature contributes to making it possible to determine gelation or thickening that may occur during long-term storage (particularly gelation or thickening that occurs after a long storage period) in a short period of time. Also, storing milk at such a temperature contributes to more reliably determining gelation or thickening that may occur during long-term storage.

[0032] In one embodiment, the predetermined temperature may be room temperature. The storage treatment at room temperature can reduce the cost required for storage compared to the storage treatment at a higher temperature, so that the determination method can be performed more efficiently.

[0033] In the storage test, the storage of the milk at the predetermined temperature may be performed over a predetermined period. The predetermined period may preferably be 5 days or more, more preferably 7 days or more, even more preferably 10 days or more, 11 days or more, 12 days or more, 13 days or more, 14 days or more, or 15 days or more, and may further be 20 days or more, or 25 days or more. Storing over such a period contributes to more reliably determining gelation or thickening that may occur. The predetermined period in the storage is preferably 3 months or less, more preferably 2 months or less, even more preferably 1 month or less. Storing over such a period contributes to making it possible to determine gelation or thickening that may occur in a short period of time.

[0034] In a preferred embodiment, the storage test may be a storage test in which mammals are stored at 15°C or higher for 5 days or longer, more preferably a storage test in which mammals are stored at 20°C or higher for 10 days or longer.

[0035] More specific examples of the amount of change will be described below.

[0036] 1.3.1.1 Change in the content of casein hydrolyzate based on the difference in storage temperature The amount of change in the content of the casein hydrolyzate may be, for example, the amount of change in the content of the casein hydrolyzate based on the difference in storage temperature. The amount of change in the content of the casein hydrolyzate in mammals stored at different temperatures is useful for determining gelation or thickening in the mammals that may occur during long-term storage of the mammals.

[0037] The amount of change in the content of the casein hydrolyzate may be, for example, "the content of casein hydrolyzate in mammals after storage for a predetermined period at a first predetermined temperature at which gelation or thickening does not occur" (hereinafter also referred to as "the content of hydrolyzate at the first temperature") and "the content of the casein hydrolyzate in the mammals after storage for the predetermined period at a second predetermined temperature at which gelation or thickening may occur" (hereinafter also referred to as "the content of hydrolyzate at the second temperature") and the amount of change based on. The predetermined period may be the period as described in 1.3.1 above.

[0038] The first predetermined temperature may be, for example, a temperature less than 15°C, preferably 10°C or less, more preferably 7°C or less. The first predetermined temperature may be, for example, 0°C or higher, particularly 1°C or higher, 2°C or higher, or 3°C or higher. In one embodiment, the first predetermined temperature may be, for example, more than 0°C to 10°C, particularly 1°C to 7°C, and more particularly about 5°C. The first predetermined temperature may be, for example, the temperature in a constant temperature bath in which mammals are stored for the storage test.

[0039] The second predetermined temperature may be, for example, 15°C or higher, preferably 20°C or higher, and more preferably 22°C or higher. The second predetermined temperature may be, for example, 50°C or lower, particularly 45°C or lower, 43°C or lower, or 40°C or lower. In one embodiment, the second predetermined temperature may be, for example, 20°C to 45°C, particularly 22°C to 40°C, and more particularly 25°C to 37°C. The second predetermined temperature may also be, for example, the temperature in a thermostatic chamber in which mammals are stored for a storage test.

[0040] When gelling or thickening, the content of the casein hydrolyzate when stored at the second predetermined temperature increases compared to that when stored at the first predetermined temperature. Therefore, this change amount may also be referred to as an increase amount or an increase rate.

[0041] In one embodiment, the change amount may be, for example, a value calculated by a predetermined calculation method using the hydrolyzate content at the first temperature and the hydrolyzate content at the second temperature.

[0042] For example, the change amount may be represented by the ratio of the hydrolyzate content at the second temperature to the hydrolyzate content at the first temperature. In this case, the predetermined calculation method may include (hydrolyzate content at the second temperature) / (hydrolyzate content at the first temperature), or (hydrolyzate content at the first temperature) / (hydrolyzate content at the second temperature). The predetermined calculation method may be represented only by this division, or may be represented based on the quotient and a predetermined coefficient, such as a predetermined coefficient being added to or multiplied by the quotient obtained from this division.

[0043] Also, the change amount may be represented by the difference between the hydrolyzate content at the second temperature and the hydrolyzate content at the first temperature. In this case, the predetermined calculation method may include (the content of the decomposition product at the second temperature) - (the content of the decomposition product at the first temperature), or (the content of the decomposition product at the first temperature) - (the content of the decomposition product at the second temperature). The predetermined calculation method may be represented only by this subtraction, or may be represented based on the difference and a predetermined coefficient, such as a predetermined coefficient being added to or multiplied by the result of this subtraction.

[0044] Also, the content of the decomposition product at the first temperature and the content of the decomposition product at the second temperature used to obtain the change amount may be values specified by measuring the amount or content ratio of the decomposition product contained in the milk, or may be values represented based on a predetermined scale. The value specified by the measurement may be obtained by a method known in the art. For example, the decomposition product may be separated from the milk by, for example, SDS-PAGE, and the content of the decomposition product after the separation may be measured. The value represented based on the predetermined scale may be, for example, the color density or area of the band of the decomposition product after SDS-PAGE for the milk, or the height or area of the peak corresponding to the decomposition product in the chromatogram obtained by HPLC for the milk, etc.

[0045] In another embodiment, a predetermined reference value may be used instead of the content of the decomposition product at the first temperature. That is, the change amount of the content of the casein decomposition product may be, for example, a change amount based on a predetermined reference value and the content of the decomposition product at the second temperature. For example, even if two or more milks are produced on different days, the two or more milks may generally have the same composition. In such a case, the content of the decomposition product at the first temperature specified for one milk may be used as a predetermined reference value in the specification of the change amount of the other milk. The method for calculating the change amount when a predetermined reference value is used may be the same as the calculation method described above, except that the "predetermined reference value" is used instead of the "decomposition product content at the first temperature". That is, the description regarding the acquisition of the change amount using the decomposition product content at the first temperature also applies to the acquisition of the change amount using the predetermined reference value.

[0046] The change amount obtained as described above may be compared with a predetermined threshold value. When the change amount is equal to or greater than (or less than or equal to) the predetermined threshold value, it may be determined that the milk gels or thickens after long-term storage. Conversely, when the change amount is less than (or greater than) the predetermined threshold value, it may be determined that the milk does not gel or thicken after long-term storage. The predetermined threshold value may be appropriately set by those skilled in the art based on, for example, the details of the storage test, the method for measuring the decomposition product content, and the method for calculating the change amount. Thus, a predetermined threshold value for determining the occurrence of gelation or thickening according to the storage test may be used in the determination method of the present invention.

[0047] A more specific example of the change amount of the casein decomposition product content will be described below. Milk is stored at 5°C and at 15°C or higher for 5 days or more, respectively. For the milk after storage, the content of the casein decomposition product is measured according to the HPLC analysis procedure described in the following examples. Then, as follows, the "increase rate of the content of the casein decomposition product after the storage test at 15°C or higher with respect to the content of the casein decomposition product after the storage test at 5°C of the milk" is calculated. When the increase rate is, for example, 1.2 or more, it may be determined that gelation or thickening occurs when the milk is stored at room temperature for a long time. Increase rate = (height of the peak top between 21.6 and 21.8 min among the peaks of the HPLC chromatogram of the milk after storage at 15°C or higher) / (height of the peak top between 21.6 and 21.8 min among the peaks of the HPLC chromatogram of the milk after storage at 5°C) In this example, the peak height between 21.6 and 21.8 min is used as the peak top height, but it is also possible to calculate using the one between 22.0 and 22.2 min. Further, it is obvious that the position of the peak top may be appropriately changed by those skilled in the art according to the HPLC conditions and the type of milk. In this example, 1.2 is used as the threshold for determining that gelation or thickening occurs, but it is obvious that other thresholds may be used according to the HPLC conditions and the type of milk. In this way, by using the content of the casein degradation product in the milk subjected to the predetermined storage treatment or an index corresponding to the content of the casein degradation product (for example, the peak top height, etc.), it is possible to determine gelation or thickening. Further, whether gelation or thickening occurs may be determined based on whether the amount of change becomes equal to or more than a predetermined threshold as described above.

[0048] 1.3.1.2 Change amount of the content of casein degradation product based on the difference in the presence or absence of storage In the determination method of the present invention, the change amount of the content of the casein degradation product may be the change amount of the content of the casein degradation product based on the difference in the presence or absence of storage. The change amount of the content of the casein degradation product in the milk specified by the difference in the presence or absence of storage is useful for determining gelation or thickening in the milk that may occur during long-term storage of the milk.

[0049] The change amount of the content of the casein degradation product is, for example, "the content of the casein degradation product in the milk before storage for a predetermined period" (hereinafter also referred to as "the degradation product content before storage"), and "the content of the casein degradation product in the milk after storage for the predetermined period" (hereinafter also referred to as "the degradation product content after storage"), and It may be a change amount based on. In the case of gelation or thickening, since the casein degradation product increases with storage, the change amount may be referred to as an increase amount or an increase rate. The predetermined period may be the period as described in 1.3.1 above. The storage may be performed at a predetermined temperature. The predetermined temperature may be the temperature as described in 1.3.1 above.

[0050] In one embodiment, the change amount may be a value calculated by a predetermined calculation method using, for example, the decomposition product content before the storage and the decomposition product content after the storage.

[0051] For example, the change amount may be represented by the ratio of the decomposition product content after the storage to the decomposition product content before the storage. In this case, the predetermined calculation method may include (the decomposition product content after the storage) / (the decomposition product content before the storage), or (the decomposition product content before the storage) / (the decomposition product content after the storage). The predetermined calculation method may be represented only by this division, or may be represented based on the quotient and a predetermined coefficient, such as a predetermined coefficient being added to or multiplied by the quotient resulting from this division.

[0052] Further, the change amount may be represented by the difference between the decomposition product content after the storage and the decomposition product content before the storage. In this case, the predetermined calculation method may include (the decomposition product content after the storage) - (the decomposition product content before the storage), or (the decomposition product content before the storage) - (the decomposition product content after the storage). The predetermined calculation method may be represented only by this subtraction, or may be represented based on the difference and a predetermined coefficient, such as a predetermined coefficient being added to or multiplied by the difference resulting from this subtraction.

[0053] Also, the decomposition product content after the storage and the decomposition product content before the storage used to obtain the change amount may be specified or represented as described above with respect to the decomposition product content at the first temperature and the decomposition product content at the second temperature. That is, the above description regarding the decomposition product content at the first temperature and the decomposition product content at the second temperature also applies to the decomposition product content after the storage and the decomposition product content before the storage.

[0054] In other embodiments, a predetermined reference value may be used instead of the content of the degradation product before storage. That is, the amount of change in the content of the casein degradation product may be, for example, the amount of change based on a predetermined reference value and the content of the degradation product after storage. The method for calculating the amount of change when a predetermined reference value is used may be the same as the calculation method described above, except that the "predetermined reference value" is used instead of the "content of the degradation product before storage". That is, the description regarding the acquisition of the amount of change using the content of the degradation product before storage also applies to the acquisition of the amount of change using the predetermined reference value.

[0055] Casein degradation products are produced by the degradation of casein. Therefore, similar to this example, gelation or thickening can also be predicted based on the amount of change (particularly the decrease amount) in the casein content. The amount of change in the casein content will be described below.

[0056] 1.3.2 Amount of change in casein content

[0057] The amount of change in the casein content may be a value represented based on the casein content after the storage test at a predetermined temperature of the milk. The storage test may be as described above, for example, a storage test in which the milk is stored at 15 °C or higher for 5 days or more.

[0058] 1.3.2.1 Amount of change in casein content based on the difference in storage temperature The amount of change in the casein content may be, for example, the amount of change in the casein content based on the difference in storage temperature. The amount of change in the casein content of milk stored at different temperatures is useful for determining gelation or thickening in the milk that may occur during long-term storage of the milk.

[0059] The amount of change in the casein content is, for example, "the casein content in milk after storage for a predetermined period at a first predetermined temperature at which gelation or thickening does not occur" (hereinafter also referred to as "the casein content at the first temperature") and "The casein content in the milk after storage for the predetermined period at the second predetermined temperature at which gelation or thickening occurs" (hereinafter also referred to as "the casein content at the second temperature") and may be a change amount based thereon. The predetermined period may be the period as described in 1.3.1 above.

[0060] The first predetermined temperature and the second predetermined temperature may be as described in 1.3.1.1 above with respect to the content of the casein degradation product, and the description also applies to the change amount of the casein content. The change amount of the casein content regarding milk stored at different temperatures is useful for determining gelation or thickening in the milk that can occur during long-term storage of the milk. In the case of gelation or thickening, since the casein content when stored at the second predetermined temperature decreases compared to that when stored at the first predetermined temperature, the change amount may be referred to as a decrease amount or a decrease rate.

[0061] In one embodiment, the change amount may be, for example, a value calculated by a predetermined calculation method using the casein content at the first temperature and the casein content at the second temperature.

[0062] For example, the change amount may be represented by the ratio of the casein content at the second temperature to the casein content at the first temperature. In this case, the predetermined calculation method may include (the casein content at the second temperature) / (the casein content at the first temperature), or (the casein content at the first temperature) / (the casein content at the second temperature). The predetermined calculation method may be represented only by this division, or may be represented based on the quotient and a predetermined coefficient, such as a predetermined coefficient being added to or multiplied by the result of this division.

[0063] Also, the change amount may be represented by the difference between the casein content at the second temperature and the casein content at the first temperature. In this case, the predetermined calculation method may include (the casein content at the second temperature) - (the casein content at the first temperature), or (the casein content at the first temperature) - (the casein content at the second temperature). The predetermined calculation method may be represented only by this subtraction, or may be represented based on the difference and a predetermined coefficient, such as a predetermined coefficient being added to or multiplied by the result of this subtraction.

[0064] Also, the casein content at the second temperature used to obtain the change amount may be a value specified by measuring the amount or content ratio of casein contained in mammals, or may be a value represented based on a predetermined scale. The value specified by the measurement may be obtained by a method known in the art. For example, the casein may be separated from mammals by, for example, SDS-PAGE, and the content of the casein after the separation may be measured. The value represented based on the predetermined scale may be, for example, the density of the color of the band of the casein after SDS-PAGE for mammals or the area of the band, or the height or area of the peak corresponding to the casein in the chromatogram obtained by HPLC for mammals, etc. Regarding the casein content at the first temperature as well, as described for the casein content at the second temperature, it may be a value specified by measuring the amount or content ratio of the casein contained in mammals, or may be a value represented based on a predetermined scale. That is, the above description regarding the casein content at the second temperature also applies to the casein content at the first temperature.

[0065] In other embodiments, a predetermined reference value may be used instead of the casein content at the first temperature. That is, the change amount of the casein content may be, for example, a change amount based on a predetermined reference value and the casein content at the second temperature. For example, even if two or more milk products are manufactured on different days, the compositions of the two or more milk products may be generally the same. In such a case, the casein content at the first temperature specified for one milk product may be used as a predetermined reference value in the specification of the change amount of the other milk product. The method for calculating the change amount when the predetermined reference value is used may be the same as the calculation method described above, except that the "predetermined reference value" is used instead of the "casein content at the first temperature". That is, the description regarding the acquisition of the change amount using the casein content at the first temperature also applies to the acquisition of the change amount using the predetermined reference value.

[0066] The change amount obtained as described above may be compared with a predetermined threshold value. When the change amount is equal to or greater than (or less than or equal to) the predetermined threshold value, it may be determined that the milk product gels or thickens after long-term storage. Conversely, when the change amount is less than (or greater than) the predetermined threshold value, it may be determined that the milk product does not gel or thicken after long-term storage. The predetermined threshold value may be appropriately set by those skilled in the art based on, for example, the details of the storage test, the method for measuring the casein content, and the method for calculating the change amount. In this way, a predetermined threshold value for determining the occurrence of gelation or thickening according to the storage test may be used in the determination method of the present invention.

[0067] 1.3.2.2 Change amount of casein content based on the difference in the presence or absence of storage In the determination method of the present invention, the change amount of the casein content may be the change amount of the casein content based on the difference in the presence or absence of storage. The change amount of the casein content in the milk product specified by the difference in the presence or absence of storage is useful for predicting the gelation or thickening in the milk product that may occur during long-term storage of the milk product.

[0068] It may be a change amount based on "the casein content in milk before storage for a predetermined period" (hereinafter also referred to as "the casein content before storage") and "the casein content in the milk after storage for the predetermined period" (hereinafter also referred to as "the casein content after storage"). When it gels or thickens, since casein decreases with storage, the change amount may be referred to as a decrease amount or a decrease rate. The predetermined period may be the period as described in 1.3.1 above. The storage may be performed at a predetermined temperature. The predetermined temperature may be the temperature as described in 1.3.1 above.

[0069] In one embodiment, the change amount may be, for example, a value calculated by a predetermined calculation method using the casein content before storage and the casein content after storage.

[0070] For example, the change amount may be represented by the ratio of the casein content after storage to the casein content before storage. In this case, the predetermined calculation method may include (the casein content after storage) / (the casein content before storage), or (the casein content before storage) / (the casein content after storage). The predetermined calculation method may be represented only by this division, or may be represented based on the quotient and a predetermined coefficient, such as a predetermined coefficient being added to or multiplied by the quotient of this division.

[0071] Also, the change amount may be represented by the difference between the casein content after storage and the casein content before storage. In this case, the predetermined calculation method may include (the casein content after storage)-(the casein content before storage), or (the casein content before storage)-(the casein content after storage). The predetermined calculation method may be represented only by this subtraction, or may be represented based on the difference and a predetermined coefficient, such as a predetermined coefficient being added to or multiplied by the difference of this subtraction.

[0072] Also, the post-preservation casein content and the pre-preservation casein content used to obtain the change amount may be specified or represented as described above regarding the casein content at the first temperature and the casein content at the second temperature. That is, the above description regarding the casein content at the first temperature and the casein content at the second temperature also applies to the post-preservation casein content and the pre-preservation casein content.

[0073] In other embodiments, a predetermined reference value may be used instead of the pre-preservation casein content. That is, the change amount of the casein content may be, for example, a change amount based on a predetermined reference value and the post-preservation casein content. The method for calculating the change amount when a predetermined reference value is used may be the same as the calculation method described above, except that the "predetermined reference value" is used instead of the "pre-preservation casein content". That is, the description regarding the acquisition of the change amount using the pre-preservation casein content also applies to the acquisition of the change amount using the predetermined reference value.

[0074] 1.4 Storage treatment The content of the casein degradation product or the change amount of the casein content may be a change amount obtained by performing a predetermined storage test on the milk of the test subject. The storage test may be, for example, a test for evaluating the degree of casein degradation in the milk when the milk is stored at a predetermined temperature for a predetermined period.

[0075] In the storage, the milk may be held in an apparatus configured to maintain the temperature of the milk at the predetermined temperature for the predetermined period. The apparatus may be, for example, a constant temperature bath, but is not limited thereto. In the storage, the milk may be contained, for example, in a container, particularly in a sterilized container. In particular, the milk may be held in the apparatus for a predetermined period while being contained in the container. The type of the container may be appropriately selected by those skilled in the art. In the method according to the present invention, mammals may be stored in this way for a predetermined period, and the degree of casein degradation in the mammals after the storage may be determined. Based on the degree of casein degradation, gelation or thickening that may occur during the storage of the mammals is determined.

[0076] 1.5 Determination Based on the degree of casein degradation, for example, gelation or thickening that occurs when the mammals are stored at room temperature for 1 month or more, particularly 2 months or more, more particularly 3 months or more, 4 months or more, or 5 months or more may be determined. The gelation and the thickening may be gelation or thickening that does not occur, for example, when the mammals are stored at room temperature for less than 1 month, particularly does not occur when stored at room temperature for less than 2 months, and more particularly does not occur when stored for a period of 3 months or less or 4 months or less at room temperature. The gelation or thickening targeted by the determination method according to the present invention may be gelation or thickening that does not occur only by being stored for such a period. The gelation or the thickening may occur, for example, within 12 months, 10 months, 8 months, 7 months, or 6 months after starting the storage of the mammals at room temperature. The determination method of the present invention is suitable for determining gelation or thickening that occurs when stored for several months or more in this way. For example, it is assumed that room temperature stored milk will be stored for a long period of several months or more, but gelation or thickening after such a long period of storage can be predicted in a short period by the method of the present invention. Therefore, according to the present invention, in the analysis of gelation or thickening that may occur during long-term storage of room temperature stored milk or in the development of products that prevent such gelation or thickening, it is not necessary to perform such long-term storage every time for analysis or development. This is considered to contribute to efficient analysis or development. As used herein, "determination" may mean a determination regarding gelation or thickening that may occur during the storage of mammals (especially during long-term storage). As used herein, "determination" includes, but is not limited to, for example, predicting whether gelation or thickening of the mammal occurs during storage of the mammal, identifying the possibility of gelation or thickening of the mammal that occurs during storage of the mammal, and identifying the risk of gelation or thickening of the mammal. In addition, the determination method of the present invention may further include an output step of outputting a determination result. The output may be an output to a display medium such as a display or a printing medium such as paper. The output may be executed using an output device (display device or printing device) known in the art. By executing the output step, for example, a developer or manufacturer of mammals can confirm the determination result and use it in the analysis or production of mammals. In addition, the determination method of the present invention may further include a recording step of recording a determination result. The recording may be a storage in an information storage medium such as a memory, or a recording in an information recording medium such as a disk or a tape (such as a magnetic recording tape). By executing the recording step, the determination result is recorded and can be used in the analysis or production of mammals.

[0077] 2. Method for analyzing mammals

[0078] The present invention also provides a method for analyzing mammals, which includes executing the determination method described in 1. above. The determination method can be executed based on the degree of casein decomposition, and since the degree of casein decomposition can be specified relatively easily, the determination method can be combined with various analysis methods other than the determination method. The mammals targeted by the analysis method of the present invention may be as described in 1. above, and the description thereof also applies to the analysis method.

[0079] For example, in addition to the determination method, the analysis method may include performing various quality analyses on mammals. The quality analysis may be, for example, one or more of physical property tests on mammals (such as specific gravity, etc.), physicochemical analyses on mammals (such as analysis of pH and / or acidity, etc.), sensory evaluations of mammals, component analyses of mammals, and analyses related to microorganisms that may be contained in mammals. The sensory evaluation may be, for example, a sensory evaluation related to one or more of the flavor, aroma, color, and texture of mammals, but is not limited thereto. The component analysis may be, for example, an analysis for specifying the composition of mammals and / or the specification or quantification of one or more components contained in mammals, but is not limited thereto. The analysis related to microorganisms may be an investigation of the presence or absence of microorganisms that may be contained in mammals and / or the identification of such microorganisms, but is not limited thereto.

[0080] 3. Method for manufacturing mammals

[0081] The present invention also provides a method for manufacturing mammals, including executing the determination method described above. The determination method can be executed based on the degree of casein decomposition, and since the degree of casein decomposition can be specified relatively easily, the determination method can be incorporated into the method for manufacturing mammals. The mammals targeted by the manufacturing method of the present invention may be as described in 1.1 above, and the description also applies to the analysis method.

[0082] For example, at any stage in the manufacturing method, a sample of the mammals targeted by the determination method may be obtained. Then, for the sample of the mammals, the degree of casein decomposition may be specified. And based on the specified degree of casein decomposition, gelation or thickening that may occur during the storage of the mammals may be determined. That is, in one embodiment, the manufacturing method may include obtaining a sample of the mammals targeted by the determination method. Further, the manufacturing method may include subjecting the sample to the storage test described in 1.4 above. Thereby, the degree of casein decomposition in the mammals used for performing the determination method of the present invention can be specified.

[0083] The method for manufacturing the dairy product may include, for example, a preparation step of preparing raw milk, and a sterilization step of subjecting the raw milk to a sterilization treatment to obtain a dairy product. The manufacturing method may further include a filling step of filling the dairy product into a container. Before the sterilization step (particularly after the preparation step and before the sterilization step), a preheating step of performing the preliminary heating treatment described in 1. above may be executed. Among these steps, after the sterilization step, a sample of the dairy product that is the subject of the determination method may be obtained. For example, the sample may be obtained after the sterilization step and before the filling step. Alternatively, the sample may be obtained after the filling step. The determination method of the present invention may be executed on the sample obtained at such a timing.

Example

[0084] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

[0085] 4. Example

[0086] <Test Example> (1) Purpose This test example was conducted to examine the relationship between the degree of casein decomposition of milk stored at 25°C for 2 to 4 weeks and gelation after long-term storage.

[0087] (2) Preparation of Samples Milk samples 1 to 4 were prepared by performing the treatments as shown in Table 1. The details of the preparation method of these samples are as follows. Raw milk (milk fat 3.8% by mass, non-fat milk solids 8.8% by mass) was purified using a clarifier. After the purification, in the preparation of Samples 1 and 2, the raw milk was heated to 87°C (preheating) without performing a heating and holding step on the raw milk. That is, for Samples 1 and 2, the purified raw milk was heated to 87°C, and immediately after the heating, the 87°C raw milk was supplied to a sterilization treatment device. In the preparation of Samples 3 and 4, after the purification, a heating and holding process was performed on the raw milk. In this heating and holding process, the raw milk was heated to 87°C and held at 87°C for 5 minutes. Regarding the preparation of Sample 1, no heating and holding process was performed, and regarding the preparation of Sample 3, after the heating and holding process, a plate-type sterilization treatment was performed on the raw milk. The sterilization treatment was a sterilization treatment at 140°C for 2 seconds using a plate-type sterilizer. Regarding the preparation of Sample 2, no heating and holding process was performed, and regarding the preparation of Sample 4, after the heating and holding process, an infusion-type sterilization treatment was performed on the raw milk. The sterilization treatment was a sterilization treatment at 127°C for 5.5 seconds using an infusion-type sterilizer (Morinaga Engineering Co., Ltd., MORINAGA DIRECT ULTRA HIGH TEMPERATURE HEATING). After the sterilization treatment, each sample was homogenized using a homogenizer under the condition of a total pressure of 22 MPa (second-stage pressure of 5 MPa), and after the homogenization treatment, it was cooled to 10°C or lower. After the cooling, sodium azide (added for preservation) was added to each sample so that the content ratio was 0.1% by mass, and each sample was aseptically filled into a sterilized 250 ml PET bottle container.

[0088]

Table 1

[0089] (3) Preparation of Samples for Analysis Samples 1 to 4 prepared in (2) above were stored at a temperature of 5, 25, or 37°C for 2 weeks or 4 weeks. After the storage, the samples were stored in an environment at 5°C until the start of the analysis. For any of Samples 1 to 4 after storage, gelation was not visually observed.

[0090] (4) Long-Term Storage Test Samples 1 to 4 prepared in (2) above were stored at a temperature of 5°C or 25°C for 90 to 210 days. For Samples 1 to 4 after long-term storage, the presence or absence of gelation was visually confirmed. Also, using a commercially available coffee filter (product name: Coffee Filter with a Focus on 2 to 4 Cups, Unbleached, company name: DAISO Co., Ltd.), the gelified product was filtered and visually confirmed.

[0091] (5) SDS-PAGE and CBB Staining For Samples 1 to 4 after storage in (3) above, SDS-PAGE was performed. 2-Mercaptoethanol (manufactured by BIORAD) and 4x Laemmi Sample Buffer (manufactured by BIORAD) were mixed at a volume ratio of 1:9 to obtain a mixed solution. Then, the mixed solution and each of Samples 1 to 4 were mixed at a volume ratio of 1:3, and after adjusting with pure water so that the final concentration of the protein content in Samples 1 to 4 was 1.5 mg / mL, heat treatment (99 °C, 3 minutes) was performed to obtain SDS-PAGE samples for each sample. Samples were applied to each lane of a 10 - 20% polyacrylamide gel (manufactured by ATTO Corporation, e-PagelHR) so that each lane contained 30 μg of protein, and SDS-PAGE was performed for 90 minutes. The gel after electrophoresis was immersed in a CBB staining solution (manufactured by ATTO Corporation, EzStain Aqua) and stained at room temperature for 3 hours or more. After removing the CBB staining solution, it was washed twice with distilled water, and then a sufficient amount of distilled water was added for decolorization. The protein bands in the decolorized gel were observed.

[0092] (6) HPLC Analysis For Samples 1 to 4 after storage in (3) above, analysis was performed by high performance liquid chromatography (HPLC). Samples 1 to 4 were diluted 3-fold using an aqueous solution of 0.1% TFA (trifluoroacetic acid), and then filtered through an ultrafiltration membrane with a molecular weight cut-off of 3 kDa made of polyethersulfone material (manufactured by Nippon Pall Corporation). The filtrate was used as a sample solution for HPLC analysis. The equipment used in this HPLC analysis and the measurement conditions for this HPLC analysis are as follows. <HPLC Equipment Used> High-performance liquid chromatograph: UltiMate 3000 HPLC / UHPLC system (manufactured by Thermo Fisher Scientific). Column: Hypersil GOLD (trademark) Phenyl HPLC column φ10 mm×250 mm, 5 μm (manufactured by Thermo Fisher Scientific). <HPLC measurement conditions> Mobile phase A: 0.1 v / v% TFA-aqueous solution Mobile phase B: 0.1 v / v% TFA-acetonitrile solution Time program: 5%B (0 min) - 5%B (1 min) - 80%B (29 min) - 80%B (34 min) - 5%B (35 min) - STOP (45 min). Sample injection volume: 300 μL, column temperature: 40°C, liquid flow rate: 2 mL / min Detection: UV215 nm

[0093] (7) Results (7-1) SDS-PAGE and CBB staining Figure 1 shows the results of CBB staining of Samples 1 to 4 after storage for 2 weeks. As shown by the component names described on the right side of the figure, the band near 14.3 kDa is the band derived from the casein hydrolyzate. From this figure, it can be seen that when Sample 2 (without heat retention, infusion type) was stored at 37°C for 2 weeks, the band derived from the casein hydrolyzate (the band within the white line frame indicated by arrow A) was darker than the bands of the other samples. That is, it was revealed that the decomposition of casein was observed when the milk of Sample 2 was stored at 37°C for 2 weeks. Figure 2 shows the results of CBB staining of Samples 1 to 4 after storage for 4 weeks. The band derived from the casein hydrolyzate (the band within the white line frame indicated by arrow A) when Sample 2 was stored at 37°C for 4 weeks became significantly darker than that when stored for 2 weeks (Figure 1). Also, when stored for 4 weeks, a dark band derived from the casein hydrolyzate was confirmed even when Sample 2 was stored at 25°C. That is, it was revealed that significant casein decomposition was observed when the milk of Sample 2 was stored at 25°C or 37°C for 4 weeks.

[0094] (7-2) HPLC analysis There were almost no differences in the shapes of the HPLC chromatograms among the samples of Sample 4 (with temperature maintenance, infusion type) stored at 5°C, 25°C, and 37°C for 2 weeks. Also, there were almost no differences in the shapes of the HPLC chromatograms among the samples of Sample 4 stored at 5°C, 25°C, and 37°C for 4 weeks. Figure 3 shows the HPLC chromatograms of the samples of Sample 2 (without temperature maintenance, infusion type) stored at 5°C for 4 weeks, 25°C, or 37°C for 2 weeks. As shown in the figure, differences were observed in the chromatograms between 20.0 and 23.0 min of retention time among the samples. Specifically, the peak tops between 21.6 and 21.8 min (''Peak 1'' in Figure 3) and between 22.0 and 22.2 min (''Peak 2'' in Figure 3) had significantly different heights. For both Peak 1 and Peak 2, the samples stored at 25°C and 37°C showed higher values than the samples stored at 5°C. When the increase rate was calculated from the following formula, the increase rate of the sample stored at 25°C was 1.34, and the increase rate of the sample stored at 37°C was 1.72. Increase rate = height of Peak 1 at 25°C or 37°C / height of Peak 1 at 5°C Similarly, when the increase rate was calculated by the following formula, the increase rate of the sample stored at 25°C was 1.32, and the increase rate of the sample stored at 37°C was 1.80. Increase rate = height of Peak 2 at 25°C or 37°C / height of Peak 2 at 5°C Figure 4 shows the HPLC chromatograms of the samples obtained by storing Sample 2 at 5°C, 25°C, or 37°C for 4 weeks. As shown in the figure, the differences in the chromatograms between 22.0 and 23.0 min in retention time were significant among the samples. Specifically, the peak tops between 21.6 and 21.8 min (Peak 3 in Figure 4) and between 22.0 and 22.2 min (Peak 4 in Figure 4) differed significantly in height, and in both Peak 3 and Peak 4, the samples stored at 25°C and 37°C showed significantly higher values than the samples stored at 5°C. When the increase rate was calculated from the following formula, the increase rate of the sample stored at 25°C was 1.58, and that of the sample stored at 37°C was 2.35. Increase rate = height of Peak 3 at 25°C or 37°C / height of Peak 3 at 5°C Similarly, when the increase rate was calculated from the following formula, the increase rate of the sample stored at 25°C was 1.57, and that of the sample stored at 37°C was 2.49. Increase rate = height of Peak 4 at 25°C or 37°C / height of Peak 4 at 5°C

[0095] (7-3) Long-term storage test Table 2 shows the results of the above (4) long-term storage test. “〇” indicates that gelation was visually confirmed, and “-” indicates that gelation was not confirmed. For Sample 2 stored at 25°C (without heat retention, infusion sterilization), significant gelation was visually confirmed at 173 days, 180 days, and 210 days of the storage period.

[0096]

Table 2

[0097] Figure 5 shows the filtered photos of Samples 1 to 4 after storage at 25°C for 6 months in the above (4) long-term storage test. When stored at 25°C for 6 months, it was clear that Sample 2 (without heat retention, infusion type) had gelled. No significant gelation was observed for samples other than Sample 2 stored at 25°C. In the experiments (7-1) and (7-2) above, for sample 2 in which casein degradation was confirmed, it was confirmed that gelation actually occurred by storing it at room temperature for a long time.

[0098] (7-4) Summary It was revealed that by analyzing the amount of casein degradation products in milk at the initial stage of milk storage (37°C, 2 to 4 weeks), that is, milk in which gelation has not occurred, using SDS-PAGE or HPLC, it is possible to determine the presence or absence of gelation after long-term storage at room temperature.

[0099] <Production Example> Raw milk (milk fat 3.8% by mass, non-fat milk solids 8.8% by mass) was purified with a clarifier and then heated and held at 87°C for 5 minutes. The raw milk was sterilized at 140°C for 2 seconds using a plate sterilizer, treated using a homogenizer under the conditions of a total pressure of 22 MPa and a second-stage pressure of 5 MPa, and cooled to 10°C or lower. The sterilized raw milk was stored in a sterile tank, stirred and homogenized, and then aseptically filled into sterilized 200 ml paper containers to obtain container-packed milk. The obtained container-packed milk was stored at a temperature of 5°C or 37°C for 2 weeks, and the same procedure as in the (6) HPLC analysis of the above test example was performed. Since no difference was observed in the two obtained chromatograms, it was possible to determine that the container-packed milk did not gel even after long-term storage at room temperature.

Claims

1. A method for determining gelation or thickening that may occur during storage of milk, based on the degree of casein degradation in the milk.

2. The method for determination according to claim 1, wherein the degree of casein degradation is the amount of change in the content of casein degradation products or the amount of change in the casein content in the milk.

3. The amount of change in the content of casein degradation products is a value expressed based on the content of casein degradation products after a storage test of the milk at 15°C or higher. The method for determination according to claim 2.

4. The amount of change in the casein content is a value expressed based on the casein content after a storage test of the milk at 15°C or higher. The method for determination according to claim 2.

5. The storage test is a storage test in which the milk is stored at 15°C or higher for 5 days or more. The method for determination according to claim 3 or 4.

6. The method for determination according to claim 1 or 2, wherein the method for determination is a prediction of gelation or thickening of the milk when the milk is stored at room temperature for 1 month or more.

7. The method for determination according to claim 1 or 2, wherein the milk is milk packed in an aseptic container.

8. A method for analyzing milk, including performing the method for determination according to claim 1 or 2.

9. A method for manufacturing milk, including performing the method for determination according to claim 1.

10. The method for determination or manufacturing method according to claim 1 or 9, wherein the milk is a product that can be stored at room temperature.

Images