JP7036534B2 - Method for producing milk protein concentrate - Google Patents

Description

The present invention relates to a method for producing a milk protein concentrate .

In the past, it has been proposed to "decalcify skim milk using a cation exchange resin to produce a milk protein concentrate" (for example, JP-A-2010-502182, JP-A-2011-024589). See publications, etc.). Such milk protein concentrates have high thermal stability and are used as useful raw materials for various dairy products such as prepared milk powder, beverages, fermented milk, and ice cream.

Special Table 2010-502182 Japanese Unexamined Patent Publication No. 2011-024589

However, when a dairy product is prepared using the milk protein concentrate obtained as described above, the saltiness and "egumi" of the dairy product are weakened, but the milk flavor tends to be insufficient.

An object of the present invention is to provide a method for producing a milk protein concentrate that does not impair the milk flavor while ensuring thermal stability.

The method for producing a milk protein concentrate (also referred to as “Milk Protein Concentrate” (hereinafter abbreviated as “MPC”)) according to the first aspect of the present invention is 130 in the range of pH 6.4 or more and 6.6 or less. A method for producing a milk protein concentrate having a heat coagulation time of 3.5 minutes or more at ° C., which comprises a pH adjustment step, a first milk protein concentrate preparation step, a water addition step, a second milk protein concentrate preparation step, and a second milk protein concentrate preparation step. A pH readjustment step is provided. In the pH adjusting step, the pH of the skim milk is adjusted within the range of 5.5 or more and less than 6.5 to prepare the pH-adjusted skim milk. In the first milk protein concentrate preparation step, the pH-adjusted skim milk is subjected to ultrafiltration treatment to prepare the first milk protein concentrate. Before proceeding from the pH adjusting step to the first milk protein concentrate preparation step, it is preferable to allow the pH-adjusted skim milk to stand or stir for a predetermined time. This is to sufficiently dissociate (free) ions such as calcium from proteins (that is, casein and the like). In the water addition step, water having a mass of 0.6 times or more the mass of the first milk protein concentrate is added to the first milk protein concentrate to prepare a diluted product of the first milk protein concentrate. The temperature of water is preferably adjusted to a temperature within the range of more than 0 ° C and 10 ° C or less. In the second milk protein concentrate preparation step, the first milk protein concentrate diluted product is subjected to ultrafiltration treatment to prepare a second milk protein concentrate. In the pH readjustment step, the pH of the second milk protein concentrate is adjusted within the range of 6.4 or more and 6.6 or less to prepare the third milk protein concentrate.

In this method for producing a milk protein concentrate, the pH of skim milk is adjusted within the range of 5.5 or more and less than 6.5, and then the raw material (that is, pH-adjusted skim milk) is subjected to ultrafiltration treatment. Here, in the pH-adjusted defatted milk, calcium ions, magnesium ions, etc. electrostatically bound to the protein are in a partially dissociated state (usually, the pH of the pH-adjusted defatted milk is 5.2. Below, all calcium ions, magnesium ions, etc. are dissociated.) Then, the partially dissociated calcium ions, magnesium ions, etc. are discharged together with the water content of the permeate when the pH-adjusted skim milk is subjected to the ultrafiltration treatment twice. As a result, a milk protein concentrate in which calcium ions, magnesium ions and the like remain appropriately is prepared. Therefore, the thermal stability of this milk protein concentrate is enhanced, and the milk flavor is not impaired in the dairy products produced using the milk protein concentrate. Further, in this method for producing a milk protein concentrate, no ion exchange treatment is performed. Therefore, in the overall flow of the method for producing a milk protein concentrate, the work man-hours can be reduced and the production cost can be kept low. Further, in this method for producing a milk protein concentrate, the pH readjustment step is performed, so that the acidity of the second milk protein concentrate can be suppressed. Further, in the pH readjustment step, by using sodium hydroxide and potassium hydroxide, the quantitative balance of sodium ions and potassium ions in the second milk protein concentrate can be adjusted. In addition, as described above, the milk protein concentrate produced by this production method has excellent thermal stability. Therefore, when producing dairy products or the like using this milk protein concentrate as a raw material, operations in the heat sterilization step and the like are performed. No need to complicate. Therefore, the milk protein concentrate produced by this production method can keep the production cost of dairy products and the like low in some cases.

The method for producing a milk protein concentrate according to the second aspect of the present invention is the method for producing a milk protein concentrate according to the first aspect, and in the pH adjusting step, the pH of skim milk is 5.5 or more and 5.8. The pH-adjusted skim milk is prepared within the following range.

The method for producing a milk protein concentrate according to the third aspect of the present invention is the method for producing a milk protein concentrate according to the first or second aspect, and in the pH readjustment step, sodium hydroxide and potassium hydroxide. The pH of the second milk protein concentrate is adjusted within the range of 6.4 or more and 6.6 or less by adding the mixed aqueous solution of the second milk protein concentrate to the second milk protein concentrate to prepare the third milk protein concentrate. To.

The method for producing a milk protein concentrate according to the fourth aspect of the present invention is a method for producing a milk protein concentrate according to any one of the first to third aspects, and the third milk protein concentrate is a method for producing a milk protein concentrate. It is liquid.

The method for producing a milk protein concentrate according to the fifth aspect of the present invention is a method for producing a milk protein concentrate according to any one of the first to fourth aspects, and the third milk protein concentrate is a method for producing the milk protein concentrate. The protein content is in the range of 9.0% by mass or more and 15.5% by mass or less, and the ash content is 0.30% by mass or more and 1.45% by mass or less per 20% by mass of the total solid content. It is within the range, the sodium content is within the range of 0.01% by mass or more and 0.09% by mass or less, and the potassium content is within the range of 0.04% by mass or more and 0.38% by mass or less. , The calcium content is in the range of 0.15% by mass or more and 0.38% by mass or less, the magnesium content is in the range of more than 0.00% by mass and 0.03% by mass or less, and the phosphorus content is contained. The amount is in the range of 0.08% by mass or more and 0.23% by mass or less, and the chlorine content is in the range of more than 0.00% by mass and 0.30% by mass or less .

The figure which showed the influence of pH on the heat coagulation time of the milk concentrate which concerns on Example 1 is shown together with the plot figure which shows the influence of pH on the heat coagulation time of the milk concentrate which concerns on Comparative Example 1. Is.

The milk concentrate according to the embodiment of the present invention is produced through a pH adjustment step, a first milk concentrate preparation step, a water addition step, and a second milk concentrate preparation step. Hereinafter, the milk concentrate will be described in detail, and then its production method and its use will be described in detail.

<Milk concentrate>
The milk concentrate according to the embodiment of the present invention is raw milk, milk or special milk or defatted milk (raw milk, milk or special milk from which milk fat is removed) or partially defatted milk (raw milk, milk or special milk). Concentrated milk (with partially removed milk fat), for example, concentrated milk (raw milk, milk or special milk) specified in the "Ministry of Health and Welfare Ordinance on Ingredient Standards for Milk and Milk Products". Those having a milk solid content of 25.5% or more and a milk fat content of 7.0% or more) and defatted concentrated milk (raw milk, milk or special milk from which milk fat content has been removed). The non-fat milk solid content is 18.5% or more, and the number of bacteria (per 1 g by the standard plate culture method) is 100,000 or less. Concentrated milk or special milk with a milk solid content of less than 25.5% (hereinafter referred to as "non-ministerial concentrated milk") "," Remove milk fat from raw milk, milk or special milk It may be a concentrated milk product with a non-fat milk solid content of less than 18.5% (hereinafter referred to as "non-ministerial defatted concentrated milk") ", but it may be a milk protein concentrate (Milk Protein). Concentrate (hereinafter also referred to as "MPC") is preferable. Hereinafter, for convenience of explanation, raw milk, milk, special milk, skim milk and partially skim milk may be collectively referred to as "raw milk".

Further, the milk concentrate according to the embodiment of the present invention contains proteins in the range of 9.0% by mass or more and 15.5% by mass or less per 20% by mass of the total solid content, and 0.30% by mass or more and 1. Ash content in the range of 45% by mass or less, sodium (Na) in the range of 0.01% by mass or more and 0.09% by mass or less, potassium (K) in the range of 0.04% by mass or more and 0.38% by mass or less. ), Calcium (Ca) in the range of 0.15% by mass or more and 0.38% by mass or less, Magnesium (Mg) in the range of more than 0.00% by mass and 0.03% by mass or less, 0.08% by mass or more It contains phosphorus (P) in the range of 0.23% by mass or less and chlorine (Cl) in the range of more than 0.00% by mass and 0.30% by mass or less.

The protein content of the milk concentrate according to the embodiment of the present invention is preferably in the range of 10.0% by mass or more and 15.5% by mass or less per 20% by mass of the total solid content. It is more preferably in the range of 10.5% by mass or more and 15.0% by mass or less, further preferably in the range of 11.0% by mass or more and 15.0% by mass or less, and 11.5% by mass or more. It is more preferably in the range of 14.5% by mass or less, further preferably in the range of 12.0% by mass or more and 14.0% by mass or less, and 12.5% by mass or more and 13.5% by mass or less. It is particularly preferable that it is within the range of.

Further, the ash content of the milk concentrate according to the embodiment of the present invention is preferably in the range of 0.40% by mass or more and 1.45% by mass or less per 20% by mass of the total solid content. It is more preferably in the range of 0.45% by mass or more and 1.40% by mass or less, further preferably in the range of 0.50% by mass or more and 1.35% by mass or less, and 0.55% by mass or more. It is more preferably in the range of 1.35% by mass or less, and particularly preferably in the range of 0.60% by mass or more and 1.30% by mass or less.

Further, the content of sodium (Na) in the milk concentrate according to the embodiment of the present invention shall be in the range of 0.01% by mass or more and 0.08% by mass or less per 20% by mass of the total solid content. Is more preferable, and it is more preferably in the range of 0.01% by mass or more and 0.07% by mass or less, further preferably in the range of 0.02% by mass or more and 0.07% by mass or less, and 0.02. It is particularly preferable that it is in the range of mass% or more and 0.06 mass% or less.

Further, the content of potassium (K) in the milk concentrate according to the embodiment of the present invention depends on the content of sodium (Na), but is generally 0. It is preferably in the range of 05% by mass or more and 0.36% by mass or less, more preferably in the range of 0.05% by mass or more and 0.34% by mass or less, and 0.05% by mass or more and 0.32. It is more preferably in the range of mass% or less, and particularly preferably in the range of 0.05 mass% or more and 0.30 mass% or less. The content of potassium (K) is preferably 3 times or more and 4 times or less of the content of sodium (Na), and 3.2 times or more and 3.9 times or less of the content of sodium (Na). It is more preferably present, more preferably 3.4 times or more and 3.8 times or less of the sodium (Na) content, and 3.6 times or more and 3.7 times or less of the sodium (Na) content. It is particularly preferable to have.

Further, the calcium (Ca) content of the milk concentrate according to the embodiment of the present invention shall be in the range of 0.15% by mass or more and 0.34% by mass or less per 20% by mass of the total solid content. Is more preferable, and it is more preferably in the range of 0.16% by mass or more and 0.32% by mass or less, and further preferably in the range of 0.17% by mass or more and 0.30% by mass or less, and 0.18% by mass. It is particularly preferable that the content is in the range of% or more and 0.28% by mass or less.

Further, the magnesium (Mg) content of the milk concentrate according to the embodiment of the present invention shall be in the range of more than 0.00% by mass and 0.02% by mass or less per 20% by mass of the total solid content. Is preferable, and more preferably in the range of more than 0.00% by mass and 0.01% by mass or less.

Further, the phosphorus (P) content of the milk concentrate according to the embodiment of the present invention shall be in the range of 0.08% by mass or more and 0.22% by mass or less per 20% by mass of the total solid content. Is more preferable, and it is more preferably in the range of 0.09% by mass or more and 0.22% by mass or less, further preferably in the range of 0.10% by mass or more and 0.21% by mass or less, and 0.11. It is particularly preferable that it is in the range of mass% or more and 0.21 mass% or less.

Further, the content of chlorine (Cl) in the milk concentrate according to the embodiment of the present invention shall be in the range of 0.01% by mass or more and 0.25% by mass or less per 20% by mass of the total solid content. Is more preferable, and it is more preferably in the range of 0.03% by mass or more and 0.25% by mass or less, further preferably in the range of 0.05% by mass or more and 0.20% by mass or less, and 0.07. It is particularly preferable that the content is in the range of mass% or more and 0.20 mass% or less.

Further, the content of the total solid content of the milk concentrate according to the embodiment of the present invention is usually in the range of 14% by mass or more and 22% by mass or less, and within the range of 16% by mass or more and 22% by mass or less. It is more preferably 18% by mass or more and 22% by mass or less, and further preferably 20% by mass or more and 22% by mass or less.

Further, the heat coagulation time of the milk concentrate according to the embodiment of the present invention at 130 ° C. (time until the coagulant is generated in the milk concentrate and the time until the viscosity of the milk concentrate increases) is 2. It is preferably 1 minute or longer, more preferably 4 minutes or longer, further preferably 6 minutes or longer, and particularly preferably 8 minutes or longer.

<Manufacturing method of milk concentrate>
As described above, the milk concentrate according to the embodiment of the present invention is produced through a pH adjusting step, a first milk concentrate preparation step, a water addition step, and a second milk concentrate preparation step. Further, when the milk concentrate according to the embodiment of the present invention is skim milk concentrate, skim milk concentrate other than the ministry ordinance, or milk protein concentrate, it is preferable to provide a skim milk preparation step before the pH adjustment step. .. Further, it is preferable that the pH readjustment step is provided after the second milk concentration preparation step. Hereinafter, these steps will be described in detail.

(1) Skim milk preparation step In the skim milk preparation step, skim milk or partially skim milk is prepared from raw milk, milk or special milk. The term "defatted milk" as used herein means that the milk fat content is removed from raw milk, milk or special milk, and for example, "raw milk, milk or special milk has a milk fat content of less than 0.5%". "What was it?" Further, the term "partially defatted milk" as used herein means that the milk fat content is partially removed from raw milk, milk or special milk, and for example, "the milk fat content of raw milk, milk or special milk is 0". It is within the range of 5.5% or more and less than 3.0%. " As described above, the skim milk preparation step does not necessarily have to be carried out. A commercially available product of skim milk concentrate or non-Ministerial skim milk concentrate may be purchased and used as a raw material milk (starting material) in the pH adjustment step.

Examples of the method for preparing defatted milk or partially defatted milk from raw milk, milk or special milk include a method of centrifuging raw milk, milk or special milk milk fat (hereinafter, also referred to as "centrifugal separation method"). , Raw milk, milk or special milk milk fat is subjected to membrane separation treatment (hereinafter, also referred to as "membrane separation method"; for example, there is precision filtration treatment) and the like. When the centrifugation method is adopted, it is preferable to centrifuge the milk fat while keeping the temperature of raw milk, milk or special milk within the range of 45 ° C. or higher and 55 ° C. or lower. Further, in such a case, it is preferable to cool the obtained skim milk or partially skim milk before the pH adjusting step. In such a case, the cooling temperature is preferably in the range of 10 ° C. or lower, which is the temperature at which the skim milk or partially skim milk remains liquid, and more preferably in the range of 1 ° C. or higher and 5 ° C. or lower.

(2) pH adjusting step In the pH adjusting step, the pH of the raw milk (for example, cooled raw milk) is adjusted within the range of 5.5 or more and less than 6.5, and the pH adjusted raw milk is prepared. The pH is preferably a predetermined value from the viewpoint of easy adjustment of the amount of alkali added and easy maintenance of low viscosity. That is, in such a case, in the pH adjusting step, the pH of the pH-adjusting raw milk is preferably in the range of 5.5 or more and 6.2 or less, and more preferably in the range of 5.5 or more and 6.0 or less. It is preferable that it is in the range of 5.5 or more and 5.8 or less. Since the pH of the raw milk is usually in the range of 6.4 or more and 7.2 or less, an acid is used in this pH adjusting step. As this acid, an acid that can be added to food, that is, an acid that is harmless to the human body, for example, hydrochloric acid, lactic acid, acetic acid, or the like is used. In this way, when the pH of the raw material milk is adjusted to the acidic side, calcium ions, magnesium ions, etc. electrostatically attached to the protein are dissociated from the protein in the pH-adjusted raw material milk. Then, by appropriately adjusting the pH of the raw material milk within the above range, the content (number) of calcium ions, magnesium ions, etc. dissociated in the raw material milk can be adjusted.

In this pH adjusting step, it is preferable to allow the pH-adjusted raw milk to stand or stir for a predetermined time after adding the above-mentioned acid to the raw milk. Here, the predetermined time is preferably 0.5 hours or more, more preferably 1 hour or more, further preferably 1.5 hours or more, and particularly preferably 2 hours or more. The predetermined time is not particularly limited, but the predetermined time is, for example, preferably 10 hours or less, more preferably 8 hours or less, further preferably 6 hours or less, and 4 hours or less. Is particularly preferable. Further, in this pH adjusting step, it is preferable to allow the pH-adjusted raw milk to stand or stir at a predetermined temperature. Here, the predetermined temperature is preferably in the range of 25 ° C. or higher, which is the temperature at which the pH-adjusted raw milk remains liquid, more preferably in the range of 1 ° C. or higher and 20 ° C. or lower, and 2 ° C. or higher and 15 ° C. It is more preferably in the range of ° C. or lower, and particularly preferably in the range of 3 ° C. or higher and 10 ° C. or lower.

(3) First milk concentrate preparation step In the first milk concentrate preparation step, after the pH adjustment step, the pH-adjusted raw material milk is subjected to ultrafiltration treatment to obtain the first milk concentrate (first milk protein concentrate). Is prepared. At this time, calcium ions, magnesium ions, etc. dissociated in the pH adjusting step are separated from the pH adjusting raw material milk (or the first milk concentrate) as a permeate. As the ultrafiltration membrane used for the ultrafiltration treatment, a flat membrane, a hollow fiber membrane, a spiral membrane, a ceramic membrane, a rotating membrane, a vibrating membrane, etc. are used, and the fractional molecular weight of the ultrafiltration membrane is , 8000 Da or more and 12000 Da or less, more preferably 9000 Da or more and 11000 Da or less, and further preferably 9500 Da or more and 10500 Da or less. By the way, the lower limit of this concentration ratio may change depending on the type of raw milk, but for example, when the raw milk is skim milk, this concentration ratio is preferably 2.5 times or more. When the raw milk is raw milk, the concentration ratio is preferably 1.5 times or more, and more preferably 2 times or more. The upper limit of the concentration ratio can be determined by the degree of pressure resistance of the ultrafiltration membrane and the ultrafiltration device. For example, when the raw milk is skim milk, the concentration ratio is 4 times or less. It is preferably 3.5 times or less, and when the raw milk is raw milk, the concentration ratio is preferably 3 times or less, more preferably 2.5 times or less. According to the diligent study of the present inventor, the higher the concentration ratio, the higher the thermal stability of the milk concentrate, the smaller the amount of alkali added in the pH readjustment (neutralization) step, and the smaller the amount of alkali added after the pH readjustment step. , It has been clarified that the viscosity of the second milk concentrate is lowered.

(4) Water addition step In the water addition step, water having a mass of 0.6 times or more the mass of the first milk concentrate is added to the first milk concentrate to prepare a diluted product of the first milk concentrate. To. The water may be a buffered aqueous solution or the like. By the way, the amount of this water added can be determined by the capacity of the ultrafiltration membrane device, the tank, etc., but is preferably in the range of 0.6 times or more and 2 times or less, and 0.7 times or more and 1.5 times or less. It is more preferably within the range of times or less, and further preferably within the range of 0.8 times or more and 1 times or less. Further, the temperature of this water is preferably in the range of more than 0 ° C. and 20 ° C. or lower, and more preferably in the range of 1 ° C. or higher and 20 ° C. or lower, from the viewpoint of suppressing the growth of general bacteria. It is more preferably in the range of 2 ° C. or higher and 15 ° C. or lower, and particularly preferably in the range of 3 ° C. or higher and 10 ° C. or lower.

In this water addition step, it is preferable to allow the diluted product of the first milk concentrate to stand or stir for a predetermined time after adding the above-mentioned water to the first milk concentrate. Here, the predetermined time is preferably 0.1 hours or more, more preferably 0.3 hours or more, further preferably 0.5 hours or more, and preferably 1 hour or more. Especially preferable. The predetermined time is not particularly limited, but the predetermined time is, for example, preferably 10 hours or less, more preferably 8 hours or less, further preferably 6 hours or less, and 4 hours or less. Is particularly preferable. Further, in this water addition step, it is preferable to allow the diluted product of the first milk concentrate to stand or stir at a predetermined temperature. Here, the predetermined temperature is preferably in the range of 25 ° C. or lower, which is the temperature at which the diluted product of the first milk concentrate remains liquid, and more preferably in the range of 1 ° C. or higher and 20 ° C. or lower. It is more preferably in the range of ° C. or higher and 15 ° C. or lower, and particularly preferably in the range of 3 ° C. or higher and 10 ° C. or lower.

(5) Second Milk Concentrate Preparation Step In the second milk concentrate preparation step, the first milk concentrate diluted with water in the water addition step, that is, the first milk concentrate diluted product is subjected to ultrafiltration treatment. Then, a second milk concentrate (second milk protein concentrate) is prepared. At this time, calcium ions, magnesium ions, and the like dissociated in the pH adjusting step are separated from the first milk concentrate diluted product (or the second milk concentrate) as a permeate. As a result, the desired "milk concentrate with reduced calcium and magnesium content (concentration)" can be obtained. As the ultrafiltration membrane used for the ultrafiltration treatment, a flat membrane, a hollow fiber membrane, a spiral membrane, a ceramic membrane, a rotating membrane, a vibrating membrane, etc. are used, and the fractional molecular weight of the ultrafiltration membrane is , 8000 Da or more and 12000 Da or less, more preferably 9000 Da or more and 11000 Da or less, and further preferably 9500 Da or more and 10500 Da or less. Further, as this ultrafiltration membrane, the ultrafiltration membrane used in the first milk concentrate preparation step may be used as it is, or a new ultrafiltration membrane may be used. Further, in the latter case, the same type of ultrafiltration membrane as the ultrafiltration membrane used in the first milk concentrate preparation step may be used, or the ultrafiltration used in the first milk concentrate preparation step may be used. An ultrafiltration membrane of a different type from the membrane may be used. By the way, the lower limit of this concentration ratio may change depending on the type of raw milk, but for example, when the raw milk is skim milk, this concentration ratio is preferably 1.5 times or more. It is more preferably 8.8 times or more, and when the raw milk is raw milk, the concentration ratio is preferably 1.3 times or more, and more preferably 1.6 times or more. The upper limit of the concentration ratio can be determined by the degree of pressure resistance of the ultrafiltration membrane and the ultrafiltration device. For example, when the raw milk is skim milk, the concentration ratio is 3.5 times. It is preferably less than or equal to, more preferably 3 times or less, and when the raw milk is raw milk, the concentration ratio is preferably 2.8 times or less, and preferably 2.3 times or less. More preferred. The concentration ratio is set to be less than the concentration ratio in the first milk concentrate preparation step.

(6) pH readjustment step In the pH readjustment step, the pH of the second milk concentrate (for example, cooled second milk concentrate, room temperature second milk concentrate) is 6.5 or more and 7.0 or less. A milk concentrate whose pH has been readjusted within the range (hereinafter, also referred to as "pH-adjusted milk concentrate" or "pH-adjusted second milk concentrate") is prepared. The pH is preferably a predetermined value from the viewpoint of easiness of improving thermal stability and easiness of maintaining low viscosity. That is, in the pH readjustment step, the pH of the pH-adjusted milk concentrate is preferably in the range of 6.5 or more and 6.9 or less, and preferably in the range of 6.5 or more and 6.8 or less. It is more preferably in the range of 6.5 or more and 6.7 or less. Since the pH of the second milk concentrate is usually in the range of 5.5 or more and less than 6.5, an alkali is used in this pH readjustment step. As this alkali, an alkali that can be added to food, that is, an alkali that is harmless to the human body, for example, sodium hydroxide, potassium hydroxide, potassium carbonate, or the like is used. At this time, the alkali is preferably used in the form of a dilute aqueous solution, more preferably in the form of a 1 to 3N alkaline aqueous solution, and further preferably in the form of a 2N alkaline aqueous solution. preferable. At this time, sodium hydroxide and potassium hydroxide so that the ratio of sodium ion / potassium ion of the second milk concentrate is the ratio of sodium ion / potassium ion of the raw material milk or a ratio close to the ratio. It is preferable to use a mixed aqueous solution of sodium hydroxide: potassium hydroxide of 2 to 4: 8 to 6, and more preferably sodium hydroxide: potassium hydroxide is 3. It is more preferable to use a mixed aqueous solution of: 7.

In this pH readjustment step, it is preferable to allow the pH-adjusted milk concentrate to stand or stir for a predetermined time after adding the above-mentioned alkali to the second milk concentrate. Here, the predetermined time is preferably 0.1 hours or more, more preferably 0.3 hours or more, further preferably 0.5 hours or more, and particularly preferably 1 hour or more. preferable. The upper limit of the predetermined time is not particularly limited, but the predetermined time is, for example, preferably 10 hours or less, more preferably 8 hours or less, further preferably 6 hours or less, and 4 hours or less. Is particularly preferable. Further, in this pH readjustment step, it is preferable to allow the pH-adjusted milk concentrate to stand or stir at a predetermined temperature. Here, the predetermined temperature is preferably in the range of 25 ° C. or higher, which is the temperature at which the pH-adjusted milk concentrate remains liquid, more preferably in the range of 1 ° C. or higher and 20 ° C. or lower, and 2 ° C. or higher. It is more preferably in the range of 15 ° C. or lower, and particularly preferably in the range of 3 ° C. or higher and 10 ° C. or lower.

<Use of milk concentrate>
The milk concentrate (second milk concentrate) according to the embodiment of the present invention can be used as a component of a raw material for dairy products. That is, this milk concentrate may be used alone as a raw material (raw milk) for dairy products, or water, raw milk, sterilized milk, skim milk, skim milk powder, skim milk powder, skim milk concentrate, skim milk. It may be mixed with other raw materials such as concentrated milk, butter milk, butter, cream, and cheese and used as a raw material for dairy products (a part of raw milk, etc.).

The above-mentioned dairy products include, for example, milk beverages (including processed milk), yogurts, lactic acid bacteria beverages, fermented milk, ice creams, creams, cheeses and the like. If necessary, any ingredient can be added to this dairy product. There are no particular restrictions on such arbitrary ingredients, but sweeteners, acidulants, vegetables, fruits and seeds, vegetable juices, fruit juices, seed juices, and vegetables, which are ingredients contained in general dairy products. Fruits and seed extracts, vitamins, minerals, nutrients such as peptides and amino acids, useful microorganisms such as lactic acid bacteria, bifidus bacteria, propionic acid bacteria, cultures of useful microorganisms, fermented products of useful microorganisms, royal jelly, Includes existing functional materials such as glucosamine, astaxanthin, polyphenols, fragrances, pH regulators, excipients, acidulants, colorants, emulsifiers, preservatives and the like. At this time, the sweeteners include, for example, glucose, fructose, malt sugar, sucrose, oligosaccharide, sugar, honey, maple syrup, agave syrup, balm sugar, moraces (sugar honey), water candy, glucose fructose liquid sugar, trehalose, and multitose. , Palatinose, xylitol, sorbitol, licorice extract, stevia-processed sweetener, Rakan fruit extract, somatin, glycerin, curculin, monerin, miraculin, erythritol and the like. Since these sweeteners not only give sweetness to dairy products but also suppress acidity and "harshness", they are preferably added positively during the production of dairy products.

When the above-mentioned dairy product is fermented milk, this milk concentrate may be used as a component of a raw material mix of fermented milk. In the preparation of this fermented milk raw material mix, for example, raw materials such as milk concentrate and other optional components (for example, sweeteners, acidulants, minerals, vitamins, flavors, etc.) are added (blended), heated, and mixed.・ It is dissolved. Then, in addition to the milk concentrate, water, raw milk, sterilized milk, whole fat powdered milk, whole fat concentrated milk, buttermilk, butter, cream, cheese, etc. are added, heated, mixed, dissolved, etc. to this raw material mix. May be. In addition, whey protein concentrate (WPC), whey protein isolate (WPI), α-lactalbumin (α-La), β-lactoglobulin (β-Lg), etc. are added and heated to this raw material mix. -Mixing / dissolving may be performed.

When the above-mentioned dairy product is fermented milk, the fermented milk can be used in the same as the conventional method for producing fermented milk, in the preparation step of the raw material mix, the (heating) sterilization step of the raw material mix, and the cooling step of the raw material mix. It is manufactured through processes such as a starter addition process, a fermentation process, and a cooling process of fermented milk. At this time, in the preparation process of the raw material mix, as described above, the raw materials are added, heated, mixed, dissolved (prepared) and the like. In each of the above-mentioned steps, general processing conditions at the time of producing fermented milk may be appropriately adopted. Further, it is preferable that the (heating) sterilization step of the raw material mix, the cooling step of the raw material mix, the addition step of the starter, the fermentation step and the cooling step of the fermented milk are carried out in this order.

<Characteristics of milk concentrate>
The milk concentrate obtained as described above has a relatively high concentration of calcium, magnesium and the like as compared with the conventional milk concentrate, but the thermal stability is satisfactorily improved or maintained. Dairy products prepared from this milk concentrate have a relatively high concentration of calcium, magnesium, etc., as compared with conventional dairy products prepared from milk concentrate, but have a milk flavor and other physical characteristics. Is well improved or maintained.

Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples. The present invention is not limited to this embodiment.

(Example 1)
1. 1. Preparation of milk concentrate (second milk concentrate) First, using a cream separator (Separator F-3 manufactured by elecrea, volume: 0.37 L), raw milk is centrifuged at 50 ° C (rotation speed: 7000 to 8000 rpm). , Treatment flow rate: 315 L / h, Treatment time: 4.2 seconds, Gravity acceleration: 1500-4400 G) to prepare skim milk, and the skim milk was cooled to 5 ° C. (skimmed milk preparation step). Next, a 2N aqueous hydrochloric acid solution was added to the cooled skim milk to adjust the pH of the skim milk to 5.7, and the mixture was left at 5 to 10 ° C. for 2 hours (pH adjustment step). Next, using a hollow fiber membrane module (Romicon Hollow fiber CTG3 "HF25-43 PM-10 manufactured by Koch Co., Ltd., fractional molecular weight: 10,000 Da, membrane area: 2.3 m ² ), the left defatted milk was subjected to. Ultrafiltration (UF) treatment at a concentration ratio of 3.2 times was performed to produce a first milk concentrate (first milk protein concentrate) (first milk concentrate preparation step). Subsequently, this first milk concentrate. Cold water (5 ° C.) having a mass of 0.8 times the mass of the first milk concentrate was added to the milk concentrate and mixed to prepare a diluted first milk concentrate (water addition step). Then, using the above-mentioned hollow fiber membrane module, the diluted product of the first milk concentrate was subjected to ultrafiltration treatment (UF) at a concentration ratio of 1.8 times to produce a second milk concentrate (. Second milk concentrate preparation step).

Before ultrafiltration of skim milk using the hollow fiber membrane module, the hollow fiber membrane was washed with an alkaline aqueous solution to which chlorine was added at 200 ppm. Then, after cooling the hollow fiber membrane while circulating cold water (3 to 5 ° C.) in the hollow fiber membrane module, the cooling water was discharged from the hollow fiber membrane module. Then, the above-mentioned left-behind skim milk (5 to 10 ° C.) was put into a tank with a jacket having a capacity of 20 L. Then, when ultrafiltration treatment of defatted milk using the hollow fiber membrane module, the hollow fiber membrane module is connected to this tank by a pipe or the like to indirectly cool this tank and this pipe. A cooling pipe was provided in the middle of the pipe to indirectly cool the pipe. The concentration ratio for ultrafiltration of skim milk is the amount of skim milk charged (treatment amount), the treatment flow rate of the permeate (permeation flow rate), the concentration of the total solid content of the holding liquid (concentrate), and the concentration of protein. It was decided from the above.

Then, after dividing this second milk concentrate into five, the ratio of sodium (ion) / potassium (ion) of each second milk concentrate is equal to the ratio in milk (about 4/15). , A mixed aqueous solution of 2N sodium hydroxide / potassium hydroxide containing 3: 7 (molar ratio) of sodium hydroxide and potassium hydroxide was added, and each second milk concentrate was added under a constant temperature environment of 20 ° C. The pH of the mixture was adjusted to 6.40, 6.45, 6.50, 6.60, 6.75 to prepare a milk concentrate whose pH was readjusted (pH readjusted milk concentrate) (pH readjustment). Process).

2. 2. Confirmation test of physical characteristics, etc. (1) Confirmation test of thermal stability First, 4 mL of each pH readjusted milk concentrate was weighed into a 14 mL round bottom vial and sealed. Next, the round-bottomed vial is immersed in an oil bath at 130 ° C., and the pH-readjusted milk concentrate is concentrated while shaking the round-bottomed vial while visually checking each pH-adjusted milk concentrate. The time until the solidified product was generated in the product was measured, and this measured time was defined as the "heat solidification time". Finally, 2 hours after the pH readjustment, the pH of each pH readjusted milk concentrate at 10 ° C. was measured, and the pH was taken as the pH of each pH readjusted milk concentrate.

The results of this confirmation test are shown in Table 1. Further, a graph of the data shown in Table 1 is shown in FIG.

(2) Sensory test (2-1)
Fermented milk was prepared using the above pH readjusted milk concentrate as raw milk, and a sensory test was conducted on the fermented milk. Hereinafter, the method for preparing the fermented milk will be described, and then the sensory test will be described in detail.

Each pH readjusted milk concentrate was sterilized by heating and stored in a sterilized vat (5 L stainless steel container). In this heat sterilization, the pH readjusted milk concentrate was heated at a temperature of 95 ° C. by a batch method using a vat.

Next, each pH-adjusted milk concentrate that had been heat-sterilized was placed in a bat and the temperature was adjusted to 43 ° C. (Mixed starter of Filth bacterium) was added so as to be 2% by mass, and they were stirred and held for 10 minutes.

Next, 70 g of each pH readjusted milk concentrate supplemented with a lactic acid bacterium starter was filled in a cup containing about 100 mL. On the other hand, each pH readjusted milk concentrate remaining here was left in the vat. Subsequently, the cups and bats were placed in a 43 ° C. incubator to ferment each pH readjusted milk concentrate. Then, when the pH of each pH readjusted milk concentrate reaches 4.6, the fermented milk in a cup is placed in a refrigerator (3 to 5 ° C.) and held overnight (about 12 hours) to be hard. A type of fermented milk was produced. On the other hand, when the pH of each pH readjusted milk concentrate reaches 4.6, the fermented milk in a vat is stirred and cooled in a cold water bath (3 to 5 ° C) to produce a soft type fermented milk. Manufactured.

(2-2)
A panel of 5 specialists eats the above hard-type fermented milk and soft-type fermented milk in a cooled state (5 ° C), and has sweetness, saltiness, acidity, harshness, milk flavor, smoothness, and unpleasant odor. The strength (degree) was evaluated on a 5-point scale. At this time, the majority of the specialized panels said, "The fermented milk of Example 1 (described above) has less harshness and richer milk flavor and smoothness than the fermented milk of Comparative Example 1 (described later)." evaluated.

(Comparative Example 1)
In the preparation of the milk concentrate, the same as in Example 1 except that the pH adjustment step is omitted and the skim milk is subjected to ultrafiltration treatment only for the first time (first time) without adjusting the pH of the cooled skim milk. To prepare a pH-adjusted milk concentrate. Then, in the same manner as in Example 1, a thermal stability confirmation test was conducted on the pH-adjusted milk concentrate. In Comparative Example 1, the pH readjustment step was carried out only for comparison with Example 1 and Example 2, and the patentability of the pH readjustment in the present invention is not denied.

The results of this confirmation test are shown in Table 1. Further, a graph of the data shown in Table 1 is shown in FIG.

<Discussion for Examples and Comparative Examples>
As is clear from FIG. 1, in the range of pH 6.4 to 6.6, the pH readjusted milk concentrate prepared in Example 1 becomes the pH readjusted milk concentrate prepared in Comparative Example 1. In comparison, it was revealed that the thermal stability was excellent. In the range of pH 6.4 to 6.5, the thermal stability of the pH readjusted milk concentrate prepared in Example 1 is at a level that can sufficiently withstand the production of fermented milk and the like, and the pH is high. Within the range of 6.5 to around 6.6, the thermal stability of the pH readjusted milk concentrate prepared in Example 1 should be evaluated as a significant level.

Claims (5)

A method for producing a milk protein concentrate, wherein the heat coagulation time at 130 ° C. is 3.5 minutes or more in the range of pH 6.4 or more and 6.6 or less.
A pH adjustment step of adjusting the pH of skim milk within the range of 5.5 or more and less than 6.5 to prepare pH-adjusted skim milk, and a pH adjustment step.
The first milk protein concentrate preparation step of preparing the first milk protein concentrate by ultrafiltration treatment of the pH-adjusted skim milk, and
A water addition step of adding water in an amount of 0.6 times or more the mass of the first milk protein concentrate to the first milk protein concentrate to prepare a diluted product of the first milk protein concentrate.
A second milk protein concentrate preparation step of preparing a second milk protein concentrate by ultrafiltration treatment of the first milk protein concentrate diluted product, and a second milk protein concentrate preparation step.
A method for producing a milk protein concentrate, comprising a pH readjustment step of adjusting the pH of the second milk protein concentrate within the range of 6.4 or more and 6.6 or less to prepare a third milk protein concentrate. The method for producing a milk protein concentrate according to claim 1, wherein in the pH adjusting step, the pH of the skim milk is adjusted within the range of 5.5 or more and 5.8 or less to prepare the pH-adjusted skim milk. In the pH readjustment step, the pH of the second milk protein concentrate is 6.4 or more and 6.6 or less by adding a mixed aqueous solution of sodium hydroxide and potassium hydroxide to the second milk protein concentrate. The method for producing a milk protein concentrate according to claim 1 or 2, wherein the third milk protein concentrate is prepared within the range of. The method for producing a milk protein concentrate according to any one of claims 1 to 3, wherein the third milk protein concentrate is a liquid. The third milk protein concentrate has a protein content of 9.0% by mass or more and 15.5% by mass or less and an ash content of 0.30% by mass per 20% by mass of the total solid content. % Or more and 1.45% by mass or less, the sodium content is in the range of 0.01% by mass or more and 0.09% by mass or less, and the potassium content is 0.04% by mass or more and 0. It is in the range of 38% by mass or less, the calcium content is in the range of 0.15% by mass or more and 0.38% by mass or less, and the magnesium content is more than 0.00% by mass and 0.03% by mass or less. The phosphorus content is in the range of 0.08% by mass or more and 0.23% by mass or less, and the chlorine content is in the range of more than 0.00% by mass and 0.30% by mass or less. The method for producing a milk protein concentrate according to any one of claims 1 to 4.

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