JP2009189260A - Heat-sterilized milk, and method for producing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing heat-sterilized milk excellent in heat stability, in more details, hardly causing precipitation even by sterilization under a high temperature condition, and hardly causing browning, and to provide the heat-sterilized milk. <P>SOLUTION: This method for producing the heat-sterilized milk comprises a first process of bringing raw material milk into contact with positive ion-exchange resin to obtain decalcium milk which has a calcium content (mg/100g)/defatted milk solid (mass%) of ≤5.2, a second process of adjusting a pH of the decalcium milk to 5.7-6.5 to obtain pH adjusted milk, and a third process of heat-sterilizing the pH adjusted milk. The heat-sterilized milk obtained by the method is also provided. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to heat-sterilized milk and a method for producing the same.

  Milk is known to be unstable to heat, such as when it is subjected to high-temperature conditions such as sterilization, it causes browning that changes its color to brown and precipitation due to protein aggregates. Yes. However, in order to preserve milk for a long period of time, it is necessary to sterilize spores that cannot be sterilized by pasteurization, and sterilization under high temperature conditions is indispensable. .

As a method for improving the thermal stability of milk, a method of removing calcium by bringing an ion exchange resin into contact with milk is known.
For example, Non-Patent Document 1 discloses a method of exchanging calcium for sodium when removing calcium from milk using an ion exchange resin. However, this method is known to increase the pH of milk after ion exchange. Moreover, although precipitation (for example, curd etc.) at the time of heat sterilization under high temperature conditions is reduced, it is not complete, and browning is not improved. Furthermore, there is a problem in flavor such as an increase in sodium in milk resulting in a strong salty taste.
Therefore, Patent Document 1 discloses a method in which milk after ion exchange is made to have the same pH as milk that is originally neutral when removing calcium from milk using an ion exchange resin. Specifically, in the ion exchange, calcium is exchanged not only with sodium but also with hydrogen ions.
In addition, as milk from which calcium has been removed, Patent Literature 2 discloses an acidic drinking raw material in which milk is acid-treated and then contacted with an ion exchange resin to remove calcium.
Japanese Patent Publication No. 7-12276 Special table 2003-515353 gazette Kunio Yamauchi et al. “Milk General Dictionary” Asakura Shoten, January 20, 1992, p. 374

However, as a result of reexamining the method described in Patent Document 1 (see Example 16 to be described later), there was a problem that the pH of milk was temporarily lowered during ion exchange, thereby causing precipitation due to protein. . When protein precipitation occurs, the ion exchange resin column becomes clogged and the resin washing after ion exchange becomes complicated. In addition, the milk after ion exchange could not completely prevent precipitation upon heat sterilization under high temperature conditions, and further, the flavor problem of strong saltiness was not solved.
In addition, the method described in Patent Document 2 is not originally intended to improve thermal stability. However, as a result of additional tests (see Example 17 described later), it was found that the thermal stability of the acidic drinking raw material finally obtained by this method is good. However, the stability of milk after acid treatment is very poor, and heating for ion exchange treatment causes adhesion and precipitation to a large amount of containers. It was necessary to do. Moreover, there is a problem that the flavor is sour so that it is difficult to use as a milk material.

  This invention is made | formed in view of the said situation, and it aims at providing the manufacturing method of heat pasteurized milk excellent in heat stability, and heat pasteurized milk. More specifically, an object of the present invention is to provide a method for producing heat-sterilized milk and a heat-sterilized milk that hardly cause precipitation even when sterilized under high-temperature conditions, and that hardly cause browning.

  In the method for producing heat-sterilized milk of the present invention, raw milk and cation exchange resin are brought into contact with each other, and the calcium content (mg / 100 g) / non-fat milk solid content (mass%) is 5.2 or less. A first step for obtaining milk, a second step for obtaining pH-adjusted milk by adjusting the pH of the decalcified milk to 5.7 to 6.5, and a third step for heat-sterilizing the pH-adjusted milk It is characterized by that.

  In the method for producing heat-sterilized milk of the present invention, raw material milk and a cation exchange resin are brought into contact to obtain ion-exchanged milk, and the ion-exchanged milk and raw material milk are mixed to obtain a calcium content (mg / 100 g ) / First step of obtaining a decalcified milk having a non-fat milk solid content (mass%) of 5.2 or less, and adjusting the pH of the decalcified milk to 5.7 to 6.5. It has the 2nd process to obtain, and the 3rd process which heat-sterilizes this pH adjustment milk, It is characterized by the above-mentioned.

In the method for producing heat-sterilized milk of the present invention, the second step is preferably a step of adding an acid to decalcified milk.
In the method for producing heat-sterilized milk of the present invention, the acid is preferably an acid selected from hydrochloric acid, carbonic acid, phosphoric acid, lactic acid, sulfuric acid, malic acid, and tartaric acid.
In the method for producing heat-sterilized milk of the present invention, the acid is preferably hydrochloric acid.
In the method for producing heat-sterilized milk of the present invention, it is preferable that the pH-adjusted milk is desalted and concentrated to remove monovalent ions between the second step and the third step.
In the method for producing heat-sterilized milk of the present invention, it is preferable that the raw material milk is any of full-fat milk, full-fat concentrated milk, full-fat powdered milk solution, skim milk, skim-fat concentrated milk, and skim milk powder solution.
The heat-sterilized milk of the present invention is obtained by any one of the above production methods.

  According to the production method of the present invention, it is possible to provide a heat-sterilized milk excellent in thermal stability and having a good flavor. More specifically, it is possible to provide heat-sterilized milk that does not easily precipitate even when sterilized under high-temperature conditions, and that hardly undergoes browning. Furthermore, it is possible to provide a manufacturing method in which no card is generated in the manufacturing process.

  Hereinafter, the manufacturing method and heat pasteurized milk of the heat-sterilized milk of this invention are demonstrated in detail.

[Production method of heat pasteurized milk]
The method for producing heat-sterilized milk of the present invention comprises decalcification in which raw milk is brought into contact with a cation exchange resin and the calcium content (mg / 100 g) / non-fat milk solid content (mass%) is 5.2 or less. A first step for obtaining milk; a second step for obtaining pH-adjusted milk by adjusting the pH of the decalcified milk to 5.7 to 6.5; and a third step for heat-sterilizing the pH-adjusted milk. (First aspect).
In the first step, raw material milk and a cation exchange resin are brought into contact to obtain ion-exchanged milk, and the ion-exchanged milk and raw material milk are mixed to obtain a calcium content (mg / 100 g) / non-fat. A decalcified milk having a milk solid content (mass%) of 5.2 or less may be obtained (second embodiment).

In the present invention, the solid content means a component excluding moisture. Furthermore, non-fat milk solid content means the component remove | excluding lipid from solid content.
In the present invention, the calcium content indicates the amount of calcium per 100 g contained in raw milk, ion-exchange milk, decalcified milk, heat-sterilized milk, and the like.
The calcium content per non-fat milk solid content in the present invention is the value obtained by dividing the calcium content in milk by the non-fat milk solid content (calcium content (mg / 100 g) / non-fat milk solid content ( Mass%)).

(First step)
First, raw material milk and a cation exchange resin are contacted to obtain ion exchange milk.
In obtaining the heat-sterilized milk of the present invention, raw milk (whole milk) or skim milk prepared by separating and removing fat from a raw milk with a cream separator can be used as raw material milk. . For convenience, commercially available milk and skim milk can also be used. Moreover, these can also be prepared and used as a solution of a suitable density | concentration. In addition, full-fat concentrated milk, non-fat concentrated milk, full-fat powder, non-fat milk, and non-fat dry milk can be prepared and used as a solution having an appropriate concentration. Furthermore, milk containing milk protein, such as those obtained by subjecting milk to membrane treatment such as ultrafiltration and microfiltration, can also be used.

In addition, in order to obtain decalcified milk whose calcium content (mg / 100 g) / non-fat milk solid content (mass%) is 5.2 or less in the first step, calcium content (mg / 100 g) / none It is preferable to use raw material milk whose fat milk solid content (mass%) is 10 to 15.6.
For example, when raw material milk having a calcium content (mg / 100 g) / non-fat milk solid content (mass%) of 10 is used, if calcium is removed by 48.0% or more based on the non-fat milk solid content, the calcium content The amount (mg / 100 g) / non-fat milk solid content (mass%) can be made 5.2 or less.
In this invention, a calcium removal rate is calculated | required on the basis of non-fat milk solid content. A specific calculation method will be described in an example described later.

  As the cation exchange resin used in the present invention, a cation exchange resin having a property of exchanging and removing calcium can be used. Specifically, a strong acid cation exchange resin, a weak acid cation exchange resin, a metal chelate resin, or the like can be used as the cation exchange resin.

As an exchange group of the cation exchange resin, a sodium form, a potassium form, a hydrogen ion form, or the like can be used, or a combination thereof may be used.
When removing calcium from raw milk using a cation exchange resin, protein precipitation tends to occur when the pH of the raw milk drops, so it is necessary to prevent the pH from dropping too low even temporarily. is there. In order not to lower the pH, it is preferable to use sodium form, potassium form, or a combination thereof. However, since the salty taste is strong when the exchange group is only in the sodium form, and the bitter taste is strong when the exchange form is only the potassium form, it is more preferable to use a sodium-potassium mixed form in which sodium and potassium form exchange groups are combined.
Examples of a method for obtaining a sodium-potassium mixed cation exchange resin include a method of mixing cation exchange resins each having a sodium-type exchange group and a potassium-type exchange group at an arbitrary ratio. Alternatively, a regeneration solution for regenerating the cation exchange resin may be prepared as a mixed solution of sodium chloride and potassium chloride to prepare a cation exchange resin in which sodium-type and potassium-type exchange groups are mixed in a single regeneration. . In particular, the latter method of preparing a cation exchange resin in which sodium-type and potassium-type exchange groups are mixed is preferable from the viewpoint of ease of regeneration, ease of equipment, and workability in actual production.

When removing calcium from raw milk using a cation exchange resin, the temperature of the raw milk can be selected from a low temperature around 5 ° C. to a high temperature above 60 ° C.
However, if the temperature of the raw milk is low, the ion exchange reactivity is poor. For this reason, when the raw material milk is passed through a column filled with a cation exchange resin, it is necessary to lower the liquid passing speed in order to maintain a calcium removal rate that provides thermal stability. If the liquid passing efficiency is poor, it takes a long time to remove calcium, which is inefficient and difficult to implement industrially. Conversely, the higher the temperature, the better the ion exchange reactivity, so the calcium removal efficiency is better, and the liquid flow efficiency in the column is higher, which is preferable.
Specifically, the temperature of the raw material milk when the raw material milk is brought into contact with the cation exchange resin is preferably 40 ° C. or higher, and more preferably 55 ° C. or higher.
However, if the temperature is too high, the problem of heat change of milk components occurs, so 75 ° C. or lower is preferable.

The raw milk and the cation exchange resin are brought into contact with each other as a batch system in which the cation exchange resin is directly put into the raw milk and stirred and contacted, and the raw milk is passed through a column filled with the cation exchange resin. A method for doing this is known. Among them, the method using a column is preferable because the calcium removal rate of ion-exchanged milk is high, it can be continuously processed, and the production efficiency is good.
Note that SV is a unit often used when liquid is passed through a column filled with resin. SV is an abbreviation for Space Velocity (space velocity) and is a value representing how many times the amount of resin per hour is allowed to pass through. For example, a speed at which a liquid twice the amount of resin per hour is passed is expressed as SV2.
In the present invention, an SV of about 3 to 5 is preferable because calcium can be efficiently removed from milk.

In the first step, it is preferable to obtain the decalcified milk of the present invention from the obtained ion exchange milk by bringing the raw material milk into contact with the cation exchange resin.
The decalcified milk of the present invention has a calcium content (mg / 100 g) / non-fat milk solid content (mass%) of 5.2 or less, and more preferably 3.8 or less.
If the calcium content (mg / 100 g) / non-fat milk solid content (mass%) is 5.2 or less, precipitation hardly occurs and high thermal stability can be obtained. In addition, when calcium content (mg / 100g) / non-fat milk solid content (mass%) exceeds 5.2, precipitation will occur easily and desired thermal stability cannot be obtained.

In the first aspect of the present invention, the ion-exchange milk is directly used as decalcified milk. Since the high calcium removal rate is obtained in the first aspect, it is preferable to use it in the manufacture of a product that requires higher thermal stability.
In the second aspect of the present invention, the ion-exchanged milk obtained by bringing the raw material milk and the cation exchange resin into contact with the raw material milk is mixed to obtain a calcium content (mg / 100 g) / non-fat milk solid. A decalcified milk having a minute (mass%) of 5.2 or less is obtained. A 2nd aspect can manufacture a product of uniform quality by keeping the calcium removal rate of a product constant, and is preferable on the management of product quality.

(Second step)
The pH of the decalcified milk obtained in the first step is adjusted to obtain pH adjusted milk.

  Examples of the pH adjusting method include a method of adjusting by adding an acid, a method of adjusting by contacting a cation exchange resin containing some hydrogen ion-type exchange groups, and the like. Especially, the method of adjusting pH by adding an acid is a more preferable method from the workability of pH adjustment being simple.

Ordinary emulsions coagulate when the pH is lowered and become a cause of adhesion during heating. Therefore, in the production method of the present invention, the calcium in the raw milk is removed using a cation exchange resin, and then the acid is added.
The acid used can be either a strong acid or a weak acid. Specific examples include hydrochloric acid, carbonic acid (carbon dioxide gas), phosphoric acid, citric acid, lactic acid, sulfuric acid, malic acid, tartaric acid, succinic acid, acetic acid, and the like. Among these, hydrochloric acid, carbonic acid, lactic acid, sulfuric acid, phosphoric acid, malic acid, or tartaric acid is preferably used from the aspect of flavor, and hydrochloric acid, carbonic acid, or lactic acid is more preferably used from the viewpoint of milk flavor. It is particularly preferable to use hydrochloric acid that is easy to use in terms of physical properties and stability and improves the desalting efficiency of the nanofiltration treatment. In addition, when carbonic acid is used, it is preferable to consider the sterilization conditions because the carbonic acid component may be lost during the third step due to the sterilization conditions, and the pH may increase and browning may occur.
Moreover, these pH adjustment methods can also be used in combination.

  In the second step, the pH of the decalcified milk is adjusted to 5.7 to 6.5 by the above pH adjustment method to obtain pH adjusted milk. If pH is 6.5 or less, precipitation and browning change hardly occur in heat sterilization under high temperature conditions, and thermal stability can be obtained. However, the lower the pH, the better. If the pH is less than 5.7, precipitation tends to occur again, and thermal stability cannot be obtained.

(Desalination and concentration treatment)
The pH-adjusted milk obtained by the above method is preferably subjected to a desalting and concentration treatment before the third step.
When a desalting and concentration treatment is performed on milk, the content of monovalent ions such as sodium, potassium, and chlorine can be reduced, and milk with better flavor can be obtained. Examples of the desalting concentration treatment method include nanofiltration and electrodialysis. Among these, nanofiltration is preferable because the apparatus is simple and easy to manufacture.
In nanofiltration, filtration is performed using a nanofiltration membrane having a pore diameter in the range of 1 to 10 nm and mainly permeable to monovalent ions and water.
In the nanofiltration, desalting and concentration can be performed until an appropriate flavor is obtained, and if necessary, diafiltration may be performed by adding water and desalting and concentrating again. In the following description, the desalted and concentrated pH-adjusted milk is referred to as desalted and concentrated pH-adjusted milk.
Moreover, when hydrochloric acid was used for pH adjustment of decalcified milk, it turned out that the desalting efficiency by nanofiltration tends to increase remarkably. Therefore, it is preferable to adjust the pH using hydrochloric acid and then perform nanofiltration treatment because the flavor improving effect is large.

(Third step)
In the third step, the pH-adjusted milk (or desalted and concentrated pH-adjusted milk) obtained in the second step is heat sterilized to obtain the heat sterilized milk of the present invention.
Examples of the heat sterilization method include a direct heating method and an indirect heating method.
Examples of the direct heating method include an infusion method and an injection method.
Examples of the indirect heating method include a plate type, a tubular type, and a scraping type.
In heat sterilization, the heat sterilization temperature is preferably 63 ° C, and more preferably 125 ° C or higher. If the heat sterilization temperature is 125 ° C. or higher, a sufficient sterilization effect can be obtained.
As the combination of the heat sterilization temperature and the heat sterilization time, the heat sterilization temperature is 63 ° C. and the heat sterilization time is 30 minutes, the heat sterilization temperature is 125 ° C. and the heat sterilization time is 2 to 30 seconds, Examples include a temperature of 135 ° C. and a heat sterilization time of 2 to 30 seconds.
The heat sterilized milk of the present invention can withstand heat sterilization at a high temperature such as a heat sterilization temperature of 121 ° C. and a heat sterilization time of 10 minutes, for example.

Since the production method of the present invention is composed of the above three steps, it is possible to efficiently obtain heat-sterilized milk having excellent thermal stability without producing aggregates such as cards during production. It is.
In addition, you may concentrate the obtained heat pasteurized milk and obtain the heat pasteurized concentrated milk excellent in heat stability. Furthermore, the heat-sterilized milk powder obtained can be concentrated and dried to obtain heat-sterilized milk powder having excellent heat stability.

[Heat pasteurized milk]
The heat-sterilized milk of the present invention is obtained by the above production method.
The heat-sterilized milk obtained by the above method has a calcium content (mg / 100 g) / non-fat milk solid content (mass%) of 5.2 or less and a pH in the range of 5.7 to 6.5. It has good thermal stability and can withstand sterilization and sterilization again, and browning and precipitation (curd formation, etc.) can be suppressed even after sterilization under high temperature conditions for a long time.
Furthermore, milk obtained from the heat-sterilized milk of the present invention (for example, heat-sterilized concentrated milk, heat-sterilized powdered milk, and a solution of the milk powder) has good heat stability in any form, and is sterilized and sterilized again. Even if it is treated, it can be tolerated, and browning and precipitation (curd formation etc.) can be suppressed even if sterilization treatment is performed for a long time under high temperature conditions.

Hereinafter, the present invention will be specifically described by way of examples, but the present invention is not limited thereto.
Each physical property in each example was measured by the following method.
In the following examples, measurement of calcium content and the like in the middle stage is omitted as appropriate, but calcium content (mg / 100 g) per non-fat milk solid content (mass%) is adjusted to pH, heat sterilization It is believed that there is no substantial change due to the concentration, or drying process.

[Calcium content]
The calcium content in the emulsion was measured using CM-212 CA / MG COUNTER manufactured by Hiranuma Sangyo Co., Ltd., which is a calcium measuring device.

[Solid content]
The solid content of the emulsion was measured using a SMART System 5 manufactured by CEM, which is a moisture measuring device.

[Fat-free milk solids]
The fat content was measured by a general method, and the value obtained by subtracting the fat content from the solid content was defined as the non-fat milk solid content.

[Removal rate of calcium based non-fat milk solid content]
According to the following formula, the calcium removal rate based on the non-fat milk solid content was determined.
In the following formula, A: calcium content of raw milk (mg / 100 g), B: calcium content of milk from which calcium has been removed (mg / 100 g), C: non-fat milk solid content (mass%) in raw milk ), D: Non-fat milk solid content (mass%) in milk from which calcium has been removed.

[PH measurement]
The pH was measured using a castani LAB pH meter F-22 manufactured by Horiba, which is a pH measuring device.

Each emulsion (heat pasteurized milk etc.) was obtained by the method of the following Examples 1-19.
Examples 1 to 11 are examples, and examples 12 to 19 are comparative examples.

[Example 1]
Non-fat milk (manufactured by Morinaga Milk Industry Co., Ltd., pH 6.8, solid content 9.1% by mass, nonfat milk solid content 9.0% by mass, calcium content 116 mg / 100 g, nonfat milk solids (mass%) ) 12.9) 51 kg of calcium content per mg) was used.
The skim milk was brought to 60 ° C., 3 columns filled with 2 liters of sodium cation exchange resin (Diaion SK-1B, manufactured by Mitsubishi Chemical Corporation) were placed in parallel, and 17 kg each was passed through SV5.0. Calcium-free milk (ion-exchange milk) having a calcium content (mg / 100 g) per non-fat milk solid content (mass%) of 1.0 (pH 7.6, solid content 8.9 mass%, non-fat milk The solid content was 8.8% by mass, the calcium content was 8.6 mg / 100 g, and the calcium non-fat milk solid content removal rate was 92.4%.
One liter of 1% by mass hydrochloric acid (manufactured by Wako Pure Chemical Industries, adjusted from a 20% by mass hydrochloric acid diluent) was added to 17 kg of the obtained calcium-free milk, and the pH was adjusted to 6.3 to obtain pH-adjusted milk. .
This pH-adjusted milk is pre-sterilized with a plate sterilizer at 85 ° C. for 5 minutes, then sterilized at 135 ° C. for 30 seconds using an infusion type direct heating method, and contains calcium per non-fat milk solid content (mass%) Heat-sterilized milk having an amount (mg / 100 g) of 1.0 (pH 6.4, solid content 8.2% by mass, nonfat milk solid content 8.1% by mass, calcium content 7.9 mg / 100 g) 5 kg was obtained.
Further, 10 kg of the heat-sterilized milk obtained was concentrated to about 2.5 times using a centrifugal thin film evaporator to obtain 3.9 kg of heat-sterilized concentrated milk (pH 6.3, solid content 21.0% by mass). It was.
Furthermore, 3.9 kg of heat-sterilized concentrated milk obtained by the same concentration method as described above was spray-dried with a milk powder dryer to obtain 600 g of heat-sterilized milk powder.

[Example 2]
Nonfat milk as raw material milk (manufactured by Morinaga Milk Industry Co., Ltd., pH 6.8, solid content 9.1% by mass, nonfat milk solid content 9.0% by mass, calcium content 116 mg / 100 g, nonfat milk solid content (% by mass) Per calcium content (mg / 100 g) 12.9) was used.
In the composition shown in Table 1, this skim milk and the decalcified milk (ion-exchange milk) obtained in Example 1 (pH 7.6, solid content 8.9% by mass, nonfat milk solid content 8.8% by mass, calcium Content 8.6 mg / 100 g, calcium content per non-fat milk solid content (mass%) 1.0), and calcium content per non-fat milk solid content (mass%) Decalcified milk (pH 7.5, solid content 9.0 mass%, non-fat milk solid content 8.9 mass%, calcium content 33.9 mg / 100 g, no calcium) (mg / 100 g) is 3.8 The removal rate (70.5% based on fat milk solid content) was 17 kg.
1 liter of 1% by mass hydrochloric acid was added to 17 kg of the obtained decalcified milk to adjust the pH to about 6.3 to obtain pH-adjusted milk.
This pH-adjusted milk was sterilized in the same manner as in Example 1, and heat-sterilized milk (pH 6.4, solid content) having a calcium content (mg / 100 g) per non-fat milk solid content (mass%) of 3.8. (17 mass%, non-fat milk solid content 8.2 mass%, calcium content 31.2 mg / 100 g) was obtained.

[Example 3]
Nonfat milk as raw material milk (manufactured by Morinaga Milk Industry Co., Ltd., pH 6.8, solid content 9.1% by mass, nonfat milk solid content 9.0% by mass, calcium content 116 mg / 100 g, nonfat milk solid content (% by mass) Per calcium content (mg / 100 g) 12.9) was used.
In the composition shown in Table 1, this skim milk and the decalcified milk (ion-exchange milk) obtained in Example 1 (pH 7.6, solid content 8.9% by mass, nonfat milk solid content 8.8% by mass, calcium Content 8.6 mg / 100 g, calcium content per non-fat milk solid content (mass%) 1.0), and calcium content per non-fat milk solid content (mass%) Decalcified milk (pH 7.4, solid content 9.0 mass%, non-fat milk solid content 8.9 mass%, calcium content 45.9 mg / 100 g, no calcium) (mg / 100 g) is 5.2 The removal rate based on the solid content of fat milk was 60.0%) and 17 kg.
One liter of 1% by mass hydrochloric acid as in Example 1 was added to 17 kg of the obtained decalcified milk to adjust the pH to about 6.3 to obtain pH-adjusted milk.
This pH-adjusted milk was sterilized in the same manner as in Example 1, and heat-sterilized milk (pH 6.4, solid content) having a calcium content (mg / 100 g) per non-fat milk solid content (mass%) of 5.2. (17 mass%, non-fat milk solid content 8.2 mass%, calcium content 42.3 mg / 100 g) was obtained.

[Example 4]
Non-fat milk (manufactured by Morinaga Milk Industry Co., Ltd., pH 7.0, solid content 9.2% by mass, nonfat milk solid content 9.1% by mass, calcium content 118 mg / 100 g, nonfat milk solid content (% by mass) ) Per calcium content (mg / 100 g) 13.0) 54 kg.
The skim milk was brought to 60 ° C., two columns as in Example 1 were juxtaposed, and 27 kg each was passed through SV5.0, and the calcium content per non-fat milk solid content (mass%) (mg / 100 g) decalcified milk (pH 7.7, solid content 9.1% by mass, nonfat milk solid content 9.0% by mass, calcium content 21.0 mg / 100 g, calcium nonfat milk solid 50%) was obtained.
Seven liters of 0.5 mass% hydrochloric acid was added to the total amount of the decalcified milk obtained to adjust the pH to 6.4 to obtain pH adjusted milk.
The pH-adjusted milk was subjected to nanofiltration treatment using a spiral nanofiltration device (manufactured by Nitto Denko Corporation, RUW-5A) and a membrane module (manufactured by Nitto Denko Corporation, NTR-7450HG), and concentrated twice. Thereafter, the same amount of water as the concentrated solution is added, and diafiltration treatment is performed three times again, and desalted and concentrated pH from which monovalent ions are partially removed by four times of concentration treatment. 28 kg of prepared milk (pH 6.4, solid content 15.3% by mass) was obtained.
This desalted and concentrated pH-adjusted milk is sterilized under the same conditions as in Example 1, and heat-sterilized milk having a calcium content (mg / 100 g) per non-fat milk solid content (mass%) of 2.3 (pH 6.4, 28 kg of solid content 13.2 mass%, non-fat milk solid content 13.1 mass%, calcium content 30.5 mg / 100 g) was obtained. Further, 3.1 kg of heat sterilized milk powder was obtained from 28 kg of the heat sterilized milk in the same manner as in Example 1.

[Example 5]
Sodium-type cation exchange resin (Diaion SK-1B), so that the final concentration of sodium chloride (manufactured by Salt Business Center) is 6% by mass and the final concentration of potassium chloride (manufactured by Tomita Pharmaceutical) is 4% by mass. The mixture was regenerated with a mixed aqueous solution to prepare a sodium-potassium mixed cation exchange resin.
Non-fat milk (manufactured by Morinaga Milk Industry Co., Ltd., pH 6.8, solid content 9.1% by mass, nonfat milk solid content 9.0% by mass, calcium content 106.0 mg / 100 g, nonfat milk solids ( 11.8) 51 kg of calcium content (mg / 100 g) per mass%) was used.
The skim milk was brought to 40 ° C., two columns filled with 2 liters of the sodium-potassium mixed cation exchange resin were juxtaposed, and 25.5 kg each was passed through SV5.0, and the nonfat milk solid Decalcified milk having a calcium content (mg / 100 g) per minute (mass%) of 2.2 (pH 7.7, solid content 9.1 mass%, nonfat milk solid content 9.0 mass%, calcium content An amount of 20.0 mg / 100 g and a calcium non-fat milk solid content removal rate of 81.1%) 50 kg were obtained.
Two liters of 2% by mass hydrochloric acid was added to the total amount of the decalcified milk obtained to adjust the pH to 6.3 to obtain pH-adjusted milk. This pH-adjusted milk is subjected to nanofiltration treatment using a spiral nanofiltration device, and is concentrated twice to remove desalted and concentrated pH-adjusted milk (pH 6.2, solid content 16.1). 26% by mass) was obtained.
This desalted and concentrated pH-adjusted milk is sterilized under the same conditions as in Example 1, and heat-sterilized milk having a calcium content (mg / 100 g) per non-fat milk solid content (mass%) of 2.2 (pH 6.2, 25 kg of solid content 15.3% by mass, non-fat milk solid content 15.2% by mass, calcium content 33.6 mg / 100 g). Further, 2.7 kg of heat sterilized milk powder was obtained from 25 kg of the heat sterilized milk in the same manner as in Example 1.

[Example 6]
A sodium-potassium mixed cation exchange resin was prepared in the same manner as in Example 5.
As raw material milk, dissolved milk (pH 6.7, solid content 11.6% by mass, non-fat milk solid content 11.5% by mass) obtained by dissolving 4.8 kg of skim milk powder (manufactured by Morinaga Milk Industry Co., Ltd.) with water to 12% by mass, A calcium content (mg / 100 g) 12.6) 40 kg per calcium content 145 mg / 100 g and non-fat milk solids (mass%) was used.
This dissolved milk was heated to 45 ° C., and 3 columns each containing 2 liters of sodium-potassium mixed cation exchange resin were used in parallel, and 13.3 kg was passed through SV3.3. Decalcified milk having a calcium content (mg / 100 g) per solid content (mass%) of 2,6 (pH 7.7, solid content 11.3 mass%, nonfat milk solid content 11.2 mass%, calcium A content of 29.3 mg / 100 g and a calcium non-fat milk solid content removal rate of 79.3% was obtained.
3.5 liters of 1% by mass hydrochloric acid was added to the total amount of the decalcified milk obtained to adjust the pH to 6.3 to obtain pH adjusted milk.
This pH-adjusted milk was subjected to nanofiltration treatment using a spiral nanofiltration apparatus in the same manner as in Example 5, concentrated twice, and desalted and concentrated pH-adjusted milk (pH 6.3, from which some monovalent minerals were removed) 21 kg of solid content 18.3% by mass was obtained.
This desalted and concentrated pH-adjusted milk is sterilized under the same conditions as in Example 1, and heat-sterilized milk having a calcium content (mg / 100 g) per non-fat milk solid content (mass%) of 2, 6 (pH 6.3, 20 kg of solid content 16.4 mass%, non-fat milk solid content 16.2 mass%, calcium content 42.4 mg / 100g) was obtained. Further, 2.7 kg of heat sterilized milk powder was obtained from 20 kg of the heat sterilized milk in the same manner as in Example 1.

[Example 7]
Dissolved milk (pH 6.8, solid content 9.0 mass%, non-fat milk solid content 8.9 mass%) obtained by dissolving 18.8 g of skim milk powder similar to Example 6 in water to 9.4 mass% as raw material milk , Calcium content 118 mg / 100 g, calcium content per non-fat milk solid content (mass%) (mg / 100 g) 13.3) 200 g were used.
The dissolved milk was brought to 60 ° C., 50 ml of sodium cation exchange resin (Diaion SK-1B) was added, and ion exchange treatment was performed in a batch manner while stirring for 30 minutes. After removing the ion exchange resin with a 400 mesh sieve (manufactured by Tokyo Screen Co., Ltd.), 50 ml of the same cation exchange resin is added again to perform the same ion exchange treatment, and calcium per non-fat milk solid content (mass%) Decalcified milk having a content (mg / 100 g) of 0.3 (pH 7.7, solid content 8.9% by mass, nonfat milk solid content 8.8% by mass, calcium content 2.5 mg / 100 g, calcium Of non-fat milk solids based on 97.9%).
To 100 g of this decalcified milk, 6 ml of 1% by mass hydrochloric acid was added to adjust the pH to 6.3 to obtain pH-adjusted milk.
This pH-adjusted milk is sterilized by an indirect heating method at 90 ° C. for 10 minutes, and heat-sterilized milk (pH 6.3, with a calcium content (mg / 100 g) per non-fat milk solid content (mass%) of 0.3, The solid content was 8.5% by mass, the non-fat milk solid content was 8.4% by mass, and the calcium content was 2.4 mg / 100 g.

[Example 8]
A sodium-potassium mixed cation exchange resin was prepared in the same manner as in Example 5.
Non-fat milk (manufactured by Morinaga Milk Industry Co., Ltd., pH 6.9, solid content 9.1% by mass, non-fat milk solid content 9.0% by mass, calcium content 112 mg / 100 g, non-fat milk solid content (% by mass) ) Per calcium content (mg / 100 g) 12.4) 55 kg.
This skim milk was brought to 60 ° C., 2 columns filled with 2 liters of the sodium-potassium mixed cation exchange resin were placed in parallel, and 27.5 kg each was passed through SV5.0, and the non-fat milk solid Decalcified milk having a calcium content (mg / 100 g) per minute (mass%) of 1.2 (pH 7.5, solid content 9.0 mass%, nonfat milk solid content 8.9 mass%, calcium content An amount of 10.4 mg / 100 g, a removal rate of 90.6% on the basis of solid content of non-fat milk of calcium) 52 kg was obtained.
The total amount of the decalcified milk obtained is subjected to nanofiltration using a spiral nanofiltration device, and concentrated twice to obtain a desalted and concentrated decalcified milk from which a part of monovalent mineral has been removed (pH 7.6, solid content) 15.5 mass%) 26.5 kg was obtained. Carbon dioxide gas (manufactured by High Pressure Gas Industry Co., Ltd., derived from liquefied carbon dioxide gas) was blown in while cooling the obtained desalted and concentrated decalcified milk to adjust pH to 6.2 to obtain desalted and concentrated pH-adjusted milk.
This desalted and concentrated pH-adjusted milk is sterilized under the same conditions as in Example 1, and heat-sterilized milk having a calcium content (mg / 100 g) per non-fat milk solid content (mass%) of 1.2 (pH 7.2, 24 kg of solid content 13.6 mass%, non-fat milk solid content 13.5 mass%, calcium content 15.8 mg / 100 g). Further, 2.4 kg of heat-sterilized powdered milk was obtained from 24 kg of the heat-sterilized milk in the same manner as in Example 1.

[Example 9]
Calcium content (mg / 100 g per non-fat milk solid content (mass%) in the same manner as in Example 7 except that 50 ml of sodium cation exchange resin (Diaion SK-1B) was charged once. ) Is 1.0 (pH 7.7, solid content 9.0 mass%, non-fat milk solid content 8.9 mass%, calcium content 8.9 mg / 100 g, calcium non-fat milk solid content 200 g of a standard removal rate of 92.5%) was obtained.
Three milliliters of 10% by mass phosphoric acid (manufactured by Wako Pure Chemical Industries, Ltd., adjusted from 85% by mass phosphoric acid dilution) was added to 100 g of this calcium-free milk, and the pH was adjusted to 6.3 to obtain pH-adjusted milk.
This pH-adjusted milk is sterilized by an indirect heating method at 90 ° C. for 10 minutes, and heat-sterilized milk having a calcium content (mg / 100 g) per non-fat milk solid content (mass%) of 1.0 (pH 6.3, 100 g of solid content 8.7 mass%, non-fat milk solid content 8.6 mass%, calcium content 8.6 mg / 100g) was obtained.

[Example 10]
In the same manner as in Example 9, decalcified milk having a calcium content (mg / 100 g) per non-fat milk solid content (mass%) of 1.0 (pH 7.7, solid content 9.0 mass%, non-fat A milk solid content of 8.9% by mass, a calcium content of 8.9 mg / 100 g, and a calcium non-fat milk solid content removal rate of 92.5%) 200 g were obtained.
Five milliliters of 10% by mass lactic acid (manufactured by Daiichi Pharmaceutical Co., Ltd., adjusted from a 90% by mass lactic acid dilution) was added to 100 g of this calcium-free milk, and the pH was adjusted to 6.3 to obtain pH-adjusted milk.
This pH-adjusted milk is sterilized by an indirect heating method at 90 ° C. for 10 minutes, and heat-sterilized milk having a calcium content (mg / 100 g) per non-fat milk solid content (mass%) of 1.0 (pH 6.3, 100 g of solid content 8.6 mass%, non-fat milk solid content 8.5 mass%, calcium content 8.5 mg / 100g) was obtained.

[Example 11]
Dissolved milk (pH 6.8, solid content 9.0 mass%, non-fat milk solid content 6.3) obtained by dissolving 18.8 g of whole milk powder (manufactured by Morinaga Milk Industry Co., Ltd.) with water to 9.4 mass% as raw material milk Mass%, calcium content 90 mg / 100 g, calcium content (mg / 100 g) 14.3) 200 g per non-fat milk solid content (mass%) were used.
This dissolved milk is heated to 60 ° C., 50 ml of sodium-type cation exchange resin (Diaion SK-1B) is added, and ion exchange treatment is performed in a batch system while stirring to obtain a solid content of non-fat milk (mass% ) Decalcified milk having a calcium content (mg / 100 g) of 4.0 (pH 7.7, solid content 9.0% by mass, nonfat milk solid content 6.3% by mass, calcium content 24.9 mg) / 100 g, calcium nonfat milk solid content removal rate 72.3%) 200 g was obtained.
To 100 g of this calcium-free milk, 5 ml of 1% by mass hydrochloric acid was added to adjust the pH to 6.3 to obtain pH-adjusted milk.
This pH-adjusted milk is sterilized by an indirect heating method at 90 ° C. for 10 minutes, and heat-sterilized milk having a calcium content (mg / 100 g) per non-fat milk solid content (mass%) of 4.0 (pH 6.3, 100 g of solid content 8.6 mass%, non-fat milk solid content 6.0 mass%, calcium content 23.8 mg / 100g) was obtained.

[Example 12]
Nonfat milk as raw material milk (manufactured by Morinaga Milk Industry Co., Ltd., pH 6.8, solid content 9.1% by mass, nonfat milk solid content 9.0% by mass, calcium content 117 mg / 100 g, nonfat milk solid content (% by mass) Per calcium content (mg / 100 g) 13.0) 17 kg was used.
The skim milk was brought to 60 ° C. and passed through one column similar to Example 1 at SV 5.0, and the calcium content (mg / 100 g) per nonfat milk solids (mass%) was 1.0. A certain decalcified milk (pH 7.6, solid content 9.0 mass%, non-fat milk solid content 8.9 mass%, calcium content 8.7 mg / 100 g, removal rate of calcium based on non-fat milk solid content 92. 4%) 17 kg was obtained.
Of the obtained decalcified milk, 16 kg was not pH-adjusted and heat sterilized at the same pH as in Example 1 to obtain a calcium content (mg / 100 g) per non-fat milk solid content (mass%). 16 kg of heat pasteurized milk (pH 7.5, solid content 9.0 mass%, non-fat milk solid content 8.9 mass%, calcium content 8.7 mg / 100 g) is obtained.
15 kg of this heat-sterilized milk was concentrated and spray-dried in the same manner as in Example 1 to obtain 1.0 kg of heat-sterilized milk powder.

[Example 13]
Nonfat milk as raw material milk (manufactured by Morinaga Milk Industry Co., Ltd., pH 6.8, solid content 9.1% by mass, nonfat milk solid content 9.0% by mass, calcium content 116 mg / 100 g, nonfat milk solid content (% by mass) Per calcium content (mg / 100 g) 12.9) was used.
In the composition shown in Table 1, this skim milk and the decalcified milk (ion-exchange milk) obtained in Example 1 (pH 7.6, solid content 8.9% by mass, nonfat milk solid content 8.8% by mass, calcium Content 8.6 mg / 100 g, calcium content per non-fat milk solid content (mass%) 1.0), and calcium content per non-fat milk solid content (mass%) Decalcified milk (pH 7.6, solid content 8.9% by mass, non-fat milk solid content 8.8% by mass, calcium content 57.2 mg / 100 g, no calcium) (mg / 100 g) is 6.5 17 kg) was obtained.
One liter of 1% by mass hydrochloric acid as in Example 1 was added to 17 kg of the obtained decalcified milk to adjust the pH to about 6.3 to obtain pH-adjusted milk.
This pH-adjusted milk was sterilized in the same manner as in Example 1, and heat-sterilized milk (pH 6.3, solid content) having a calcium content (mg / 100 g) per non-fat milk solid content (mass%) of 6.5. 18.4 kg of 8.4 mass%, non-fat milk solid content 8.3 mass%, calcium content 54.0 mg / 100g) was obtained.

[Example 14]
In the same manner as in Example 11, decalcified milk having a calcium content (mg / 100 g) per non-fat milk solid content (mass%) of 4.0 (pH 7.7, solid content 9.0 mass%, non-fat Milk solid content 6.3% by mass, calcium content 24.9 mg / 100 g, calcium non-fat milk solid content removal rate 72.3%) 200 g was obtained.
This calcium free milk 100 g is sterilized by indirect heating method at 90 ° C. for 10 minutes without adjusting pH, and the calcium content (mg / 100 g) per non-fat milk solid content (mass%) is 4.0. 100 g of pasteurized milk (pH 7.7, solid content 9.0 mass%, non-fat milk solid content 6.3 mass%, calcium content 24.9 mg / 100 g) was obtained.

[Example 15]
Sodium-type cation exchange resin (Diaion SK-1B) was regenerated with a regenerating solution (hydrochloric acid concentration 0.8% by mass) containing 10% by mass sodium chloride aqueous solution and 4% by mass of 20% by mass hydrochloric acid. A hydrogen ion mixed cation exchange resin was prepared.
Non-fat milk (manufactured by Morinaga Milk Industry Co., Ltd., pH 6.8, solid content 9.1% by mass, nonfat milk solid content 9.0% by mass, calcium content 116 mg / 100 g, nonfat milk solids (mass%) ) 12.9) 17 kg of calcium content per mg).
This skim milk is brought to 60 ° C., 2 liters of the sodium-hydrogen ion mixed cation exchange resin is added, and batch-type ion exchange treatment is carried out with stirring to obtain calcium per non-fat milk solid content (mass%). Decalcified milk having a content (mg / 100 g) of 2.0 (pH 6.3, solid content 8.6% by mass, nonfat milk solid content 8.5% by mass, calcium content 16.7 mg / 100 g, calcium The non-fat milk solid content removal rate of 84.8%) was 17 kg.
The decalcified milk having a pH of 6.3 is heat-sterilized in the same manner as in Example 1, and the heat-sterilized milk content (mg / 100 g) per non-fat milk solid content (mass%) is 2.0. 18 kg of milk (pH 6.2, solid content 7.6% by mass, nonfat milk solid content 7.5% by mass, calcium content 14.8 mg / 100 g) was obtained.

[Example 16]
A sodium-hydrogen ion mixed cation exchange resin was prepared by a method of mixing a sodium-type and hydrogen ion-type cation exchange resin in a ratio of 93: 7 (see Japanese Patent Publication No. 07-012276).
Non-fat milk (manufactured by Morinaga Milk Industry Co., Ltd., pH 6.8, solid content 9.1% by mass, nonfat milk solid content 9.0% by mass, calcium content 117 mg / 100 g, nonfat milk solids (mass%) ) Per calcium content (mg / 100 g) 13.0) 17 kg.
This skim milk was brought to 60 ° C., and an attempt was made to pass it through SV5.0 through one column packed with 2 liters of the sodium-hydrogen ion mixed cation exchange resin. However, the precipitate (curd) generated inside the column during the passage was clogged at the lower part of the column, making the passage impossible, and decalcified milk could not be obtained.
Therefore, except that this sodium-hydrogen mixed cation exchange resin was used as the cation exchange resin, the batch-type ion exchange treatment was carried out in the same manner as in Example 15, and calcium content per non-fat milk solid content (mass%) was obtained. Decalcified milk (pH 7.1, solid content 9.0 mass%, non-fat milk solid content 8.9 mass%, calcium content 20.2 mg / 100 g, calcium content 2 mg / 100 g) 17 kg of non-fat milk solid content removal rate 82.5%) was obtained.
This decalcified milk was heat-sterilized in the same manner as in Example 1, and heat-sterilized milk having a calcium content (mg / 100 g) per non-fat milk solid content (mass%) of 2.3 (pH 7.0, solid content) 9.0 mass%, non-fat milk solid content 8.9 mass%, calcium content 20.2 mg / 100 g) 15 kg was obtained.

[Example 17]
Non-fat milk (manufactured by Morinaga Milk Industry Co., Ltd., pH 6.8, solid content 9.1% by mass, nonfat milk solid content 9.0% by mass, calcium content 116 mg / 100 g, nonfat milk solids (mass%) ) 12.9) 17 kg of calcium content per mg). To this raw milk, 0.8 kg of a 3.3% by mass citric acid solution (manufactured by DSM Citric Acid, prepared from anhydrous citric acid) was added to obtain 17.8 kg of pH-adjusted milk having a pH of 5.8 (Special Table 2003). No. 515353).
Although this pH-adjusted milk was heated to 60 ° C., the thermal stability of the solution was poor, and a large amount of thin-film card adhered to the heating container. Therefore, the pH-adjusted milk after heating was filtered with a 400 mesh sieve.
After that, 17 kg of pH-adjusted milk (solid content: 8.8% by mass) having a pH of 5.8, from which the curd was removed, was passed through the column filled with 2 liters of the sodium ion exchange resin used in Example 1 at SV 5.0. , Decalcified milk having a calcium content (mg / 100 g) per non-fat milk solid content (mass%) of 0.6 (pH 6.3, solid content 8.8 mass%, non-fat milk solid content 8.7 17% of mass%, calcium content 4.9 mg / 100 g, removal rate of calcium based on non-fat milk solid content 95.6%).
This decalcified milk was heat-sterilized in the same manner as in Example 1, and heat-sterilized milk (pH 6.3, solid content) having a calcium content (mg / 100 g) per non-fat milk solid content (mass%) of 0.6. 8.2 mass%, non-fat milk solid content 8.1 mass%, calcium content 4.6 mg / 100 g) was obtained 16 kg.

[Example 18]
Non-fat milk (manufactured by Morinaga Milk Industry Co., Ltd., pH 6.8, solid content 9.1% by mass, nonfat milk solid content 9.0% by mass, calcium content 116 mg / 100 g, nonfat milk solids (mass%) ) Calcium content per mg (mg / 100 g) 12.9) 100 g was used. A 1% by mass hydrochloric acid solution was appropriately added to the skimmed milk to obtain pH-adjusted milk having a pH of 6.3.
When this pH-adjusted milk was sterilized by heating at 121 ° C. for 10 minutes in an autoclave apparatus, it became a pudding and completely gelled. Moreover, when the liquid before sterilization was preserve | saved at 5 degreeC for about 8 hours, it turned out that this also gelatinized completely and became a very bad emulsion.

Example 19
Non-fat milk (manufactured by Morinaga Milk Industry Co., Ltd., pH 6.9, solid content 9.2% by mass, nonfat milk solid content 9.1% by mass, calcium content 112.0 mg / 100 g, nonfat milk solids ( The calcium content (mg / 100 g) per mass%) (12.3) 22 kg was used.
The raw material milk was brought to 60 ° C., and passed through one column packed with 2 liters of the same ion exchange resin as in Example 1 at SV 5.0, and the calcium content per non-fat milk solid content (mass%) ( decalcified milk (pH 7.8, solid content 8.9% by mass, nonfat milk solid content 8.8% by mass, calcium content 6.8 mg / 100 g, calcium nonfat) (Removal rate based on milk solid content 93.7%) 20 kg was obtained.
The total amount of the decalcified milk thus obtained was subjected to the same nanofiltration treatment as in Example 5 at the same pH and concentrated twice to remove monovalent minerals, and then the same amount as the concentrated solution. 20 kg of desalted pH-adjusted milk (pH 7.8, solid content 8.4% by mass) whose solid content was adjusted by adding water was obtained.

As mentioned above, when the component composition of each emulsion obtained by Examples 1-19, concentrated milk, and powdered milk was analyzed by the general method, the composition per solid content is the fat almost the same as normal skim milk or whole fat milk. It was milk that had protein, carbohydrates, and ash, and only changed mineral and organic acid composition.
In Examples 1 to 11, which are examples, heat-sterilized milk was efficiently obtained without agglomerates such as curds being produced during the production.
On the other hand, Example 12, which is a comparative example, differs from the present invention in that pH adjustment is not performed.
The heat-sterilized milk obtained in Example 13 has a calcium content (mg / 100 g) per non-fat milk solid content (mass%) of 5.2 or more, which is different from the heat-sterilized milk of the present invention.
Example 14 differs from the present invention in that pH adjustment is not performed.
Example 15 is different from the method for producing heat-sterilized milk of the present invention in that calcium exchange and pH adjustment are performed simultaneously. The method of Example 15 was not practical because the ion exchange treatment could only be performed in batch mode.
Example 16 differs from the present invention in that pH adjustment is not performed. The method of Example 16 was not practical because the ion exchange treatment could only be performed in a batch mode.
Example 17 differs from the method for producing heat-sterilized milk of the present invention in that calcium is removed after pH adjustment. This method was not practical because a curd was generated when the temperature was adjusted to 60 ° C. after adjusting the pH.
In Example 18, only pH adjustment was performed without exchanging and removing calcium, and then heat sterilization was performed at 121 ° C. for 10 minutes, and the pH-adjusted milk gelled at the time of heat sterilization.
In Example 19, neither pH adjustment nor heat sterilization was performed.
In addition, since the heat sterilization in Examples 1 to 17 ("sterilize at 135 ° C for 30 seconds after preliminary sterilization at 85 ° C for 5 minutes" or "sterilize at 90 ° C for 10 minutes") is low temperature or short time, In any of the examples, no curd or browning occurred during the heat sterilization.
Each emulsion, concentrated milk, or powdered milk obtained in each example was evaluated by the following test.

[Test Example 1]
The purpose of this test was to verify the thermal stability of each emulsion obtained in each example, and 17 types of samples were examined as shown in Table 2.
1. Test sample As shown in Table 2, each emulsion prepared in each example and a powdered milk solution were prepared and used as a thermal stability test sample.
Specifically, the heat-sterilized milk prepared in Example 1 was used as the sample (1). As sample (2), the heat-sterilized milk prepared in Example 12 was used. As sample (3), the heat-sterilized milk prepared in Example 11 was used. As sample (4), the heat-sterilized milk prepared in Example 14 was used. As sample (5), the heat-sterilized milk prepared in Example 7 was used. As the sample (6), the heat-sterilized milk prepared in Example 2 was used. As sample (7), the heat-sterilized milk prepared in Example 3 was used. As sample (8), the heat-sterilized milk prepared in Example 13 was used. As sample (9), the heat-sterilized milk prepared in Example 15 was used. As the sample (10), the emulsion prepared in Example 16 was used. As the sample (11), a solution obtained by dissolving the heat-sterilized milk powder prepared in Example 4 (solid content: 96% by mass) in water at 50 ° C. at 9.4% by mass (solid content: 9.0% by mass) was used. . As the sample (12), a solution obtained by dissolving the heat-sterilized milk powder (solid content: 96% by mass) prepared in Example 5 in water at 50 ° C. at 9.4% by mass (solid content: 9.0% by mass) was used. . As the sample (13), a solution obtained by dissolving the heat-sterilized milk powder (solid content: 96% by mass) prepared in Example 6 in water at 50 ° C. at 9.4% by mass (solid content: 9.0% by mass) was used. . As sample (14), the heat-sterilized milk prepared in Example 17 was used. As the sample (15), a solution obtained by dissolving the heat-sterilized milk powder (solid content: 96% by mass) prepared in Example 8 in water at 50 ° C. at 9.4% by mass (solid content: 9.0% by mass) was used. . As sample (16), the heat-sterilized milk prepared in Example 9 was used. As the sample (17), the heat-sterilized milk prepared in Example 10 was used.
Table 2 shows the pre-sterilization pH, calcium content (mg / 100 g), non-fat milk solid content (mass%), calcium content (mg / 100 g) / non-fat milk solid content (mass%) of each sample. Indicated.

2. Test method In order to examine thermal stability, 50 g of each sample was put into a beaker, and heat sterilization was performed at 121 ° C. for 10 minutes using an autoclave apparatus (KS-323, manufactured by Tommy Seiko Co., Ltd.) which is a general sterilization apparatus. did.
The method for evaluating the precipitation (curd) formation by heating is to transfer the entire amount to a 50 ml centrifuge tube for milk powder (manufactured by Nakamura Medical Science Co., Ltd.), and at a centrifugal force of 1500 g using an H-103N centrifuge manufactured by a domestic centrifuge. After centrifuging for 5 minutes, the amount of sediment collected at the bottom of the centrifuge tube was measured. The results are shown in Table 3.
The measuring method of the degree of browning was evaluated using a hunter type color difference meter, which is one of general color evaluation methods. Specifically, using a COLOR READER CR-13 colorimeter manufactured by Minolta Co., Ltd., the color difference value was measured 5 times for 3 ml of the obtained emulsion or sterilizing solution, and the average value was taken as the color difference value of the solution. From the color difference value, the value of color difference ΔE, which is a general color difference evaluation method, was obtained, and the change in the color of the solution due to the presence or absence of heating was evaluated. The results are shown in Table 3.
The value of ΔE is obtained using the Hunter color system value according to the following formula (the color difference of the sample before heating is (L1, a1, b1), and the color difference of the sample after heating is (L2, a2, When expressed as b2), ΔL = L1-L2, Δa = a1-a2, Δb = b1-b2).

3. Test results Samples (1) and (2) are each made from skim milk, and sample (1) is a weakly acidic heat-sterilized milk whose pH is adjusted, and sample (2) is near neutral without pH adjustment. This is heat pasteurized milk. Samples (3) and (4) each have a whole milk powder solution as raw material milk. Similarly, sample (3) is a weakly acidic heat-sterilized milk and sample (4) is a heat-sterilized milk near neutrality. . According to these, it can be said that by making it weakly acidic, it is possible to obtain a milk or a milk concentrate having very high thermal stability in which both precipitation and browning are suppressed.
The calcium content (mg / 100 g) per non-fat milk solid content (mass%) in the samples (5) to (8) is 0.3, 3.8, 5.2, and 6.5 in order. According to this, in order to suppress precipitation, browning, etc., it is effective when the calcium content (mg / 100 g) per non-fat milk solid content (mass%) is 5.2 or less. It can be said that the effect is particularly great when it is 8 or less.
Although the sample (9) is an emulsion having high heat stability, as described above, the method for producing the heat-sterilized milk of Example 15 used for the sample (9) is only a batch method and is not practical. . Sample (10) had a pH of 7.0 and could not suppress browning.
In samples (11), (12), and (13), even if the pH-adjusted milk is subjected to nanofiltration treatment for desalting, precipitation and browning can be suppressed, and the high thermal stability does not change. It has been shown. Further, samples (12) and (13) showed that the same thermal stability can be obtained even when a sodium-potassium mixed resin is used as the cation exchange resin.
Sample (14) is an emulsion with high heat stability, but as described above, in Example 17 used for sample (14), a phenomenon such as card formation or gelation occurs after the addition of acid during production, resulting in instability. Is not practical.
In samples (15) to (17), carbon dioxide, phosphoric acid, and lactic acid were used as the acid to be added. With carbonic acid, sterilization for a long time in an autoclave caused carbon dioxide to vaporize during sterilization, resulting in a pH increase and browning, but precipitation did not occur at all, and heat stability was higher than conventional calcium-free milk without pH adjustment. It was shown that it was improving. In addition, phosphoric acid and lactic acid had no problem with browning or precipitation. Thus, it was shown that precipitation and browning can be prevented and the thermal stability can be improved even if the pH is adjusted with an acid used as a food.

[Test Example 2]
The purpose of this test is to verify the desalting efficiency during the nanofiltration process.
As shown in Table 4, for the decalcified milk obtained in Examples 4, 5, and 19, and the emulsion after double concentration, the sodium content was measured by the ICP method, and the sodium content X per 100 g of solid content X Was calculated from the following formula, X = sodium content (mg / 100 g) ÷ solid content (mass%) × 100, and evaluated. The results are shown in Table 4.

Example 4 and Example 19 compare the desalting efficiency at the time of double concentration by nanofiltration treatment. Table 4 shows that desalting by adding nanohydrochloric acid after adding hydrochloric acid (Example 4) increases the desalting efficiency about twice as much as performing nanofiltration without adding hydrochloric acid (Example 19). Was confirmed. In other words, it was shown that by adding hydrochloric acid and then desalting by nanofiltration treatment, the salty taste increased by ion exchange can be suppressed, and milk having good flavor and excellent thermal stability can be produced.
Further, from the comparison between Examples 4 and 5, it was found that sodium-potassium mixed cation exchange resin was used for calcium removal when sodium cation exchange resin was used and when sodium-potassium mixed cation exchange resin was used. It was shown that the amount of sodium can be reduced, the heat stability is good, and the milk with excellent flavor can be produced.

[Test Example 3]
The purpose of this test is to verify the flavor of the typical emulsion obtained in each example.
The emulsions or milk powders obtained in Example 12, Example 1, Example 4 and Example 5 were prepared as shown in Table 6 and evaluated by 20 trained flavor panelists.
Specifically, the heat-sterilized milk prepared in Example 1 was used as the sample (1). As the sample (2), a diluted solution obtained by diluting the heat-sterilized milk obtained in Example 4 to a solid content of 9% by mass was used. As the sample (3), a diluted solution obtained by diluting the heat-sterilized milk obtained in Example 5 to a solid content of 9% by mass was used.
The evaluation method uses the heat-sterilized milk of Example 12 that has been sterilized by removing calcium in skim milk with a sodium ion resin as a control. Evaluation was made on a 5-point scale. Table 6 shows the results of statistical processing.

From the results in Table 6, the salty and sour tastes were significantly stronger in the sample (1) to which hydrochloric acid was added than in the control in which calcium and sodium were ion-exchanged. However, according to the samples (2) and (3), the saltiness was significantly reduced by the nanofiltration treatment (significant level 1%), the taste was good and the heat stability was high without increasing the acidity. It was shown that an emulsion was obtained.
That is, it can be said that it is preferable to carry out desalting and concentration treatment in the production process of heat-sterilized milk in order to obtain an emulsion having good heat stability without reducing salty taste and increasing sourness.

[Test Example 4]
The purpose of this test was to verify at which pH the heat stability of the milk was excellent. As shown in Table 7, 18 types of samples were prepared and examined.
1. Test sample As shown in Table 7, the heat-sterilized milk of pH 7.5 prepared in Example 12 was used as the sample (1). Samples (2) to (18) were prepared by appropriately adding 1% by mass hydrochloric acid to the heat-sterilized milk of pH 7.5 prepared in Example 12 to adjust the pH to 5.4 to 7.0. .

2. Test Method The thermal stability of each sample heat-sterilized in an autoclave apparatus at 121 ° C. for 10 minutes in the same manner as in Test Example 1 was evaluated by the precipitation amount and the color difference ΔE. The results are shown in Table 7.

3. Test result From Table 7, when calcium was exchanged and removed and an emulsion having a calcium content (mg / 100 g) per non-fat milk solid content (mass%) of 5.2 or less was used, the pH was 6.5 which was weakly acidic. By making it below, it is possible to obtain milk with high heat stability in which both precipitation and browning are suppressed, and it was shown that the lower the pH, the more effective. However, the lower the pH, the better. The lower the pH, the lower the thermal stability. Therefore, it was shown that the pH should be adjusted to 5.7 to 6.5 in order to obtain milk having high heat stability.

[Test Example 5]
The purpose of this test was to verify which acid can be used for the production of heat-sterilized milk having high thermal stability. As shown in Table 8, nine types of samples were prepared and examined.
1. Test sample As shown in Table 8, the sample (1) was prepared by adding 2 mass% hydrochloric acid to the heat-sterilized milk prepared in Example 12 and adjusting the pH to 6.1. As sample (2), the heat-sterilized milk prepared in Example 12 was blown with carbon dioxide to adjust the pH to 6.1. As the sample (3), 8.5% by mass phosphoric acid was added to the heat-sterilized milk prepared in Example 12 to adjust the pH to 6.1. As sample (4), 9 mass% lactic acid was added to the heat-sterilized milk prepared in Example 12 to adjust the pH to 6.1. As the sample (5), 10% by mass malic acid was added to the heat-sterilized milk prepared in Example 12 to adjust the pH to 6.1. As the sample (6), 10% by mass tartaric acid was added to the heat-sterilized milk prepared in Example 12 to adjust the pH to 6.1. As the sample (7), 10% by mass of succinic acid was added to the heat-sterilized milk prepared in Example 12 to adjust the pH to 6.1. As sample (8), 10 mass% acetic acid was added to the heat-sterilized milk prepared in Example 12 to adjust the pH to 6.1. As the sample (9), 10% by mass citric acid was added to the heat-sterilized milk prepared in Example 12 to adjust the pH to 6.1. As the sample (10), the heat-sterilized milk prepared in Example 12 was added with 2% by mass sulfuric acid to adjust the pH to 6.1.

2. Test method The thermal stability of the sample heat-sterilized on the conditions of 121 degreeC for 10 minutes with the autoclave apparatus by the method similar to Test Example 1 was evaluated by the amount of precipitation. Furthermore, the flavor evaluation of the emulsion adjusted with the acid was evaluated by six trained flavor panelists, and the flavor tendency and availability were examined. The results are shown in Table 8.

3. Test results From Table 8, when an emulsion having calcium content (mg / 100 g) per non-fat milk solid content (mass%) of 5.2 or less was used, the acid for adjusting the pH was organic. It was shown that any kind of acid, inorganic acid, strong acid, weak acid and long-term sterilization treatment under high temperature conditions can achieve the desired thermal stability without browning or precipitation. .
However, depending on the acid, the flavor may be very bad, so hydrochloric acid, carbonic acid, or lactic acid that is yogurt-flavored, which has little effect on the flavor, is desirable. It was shown that phosphoric acid, malic acid and tartaric acid, which have sulfuric acid and sour taste, but have no wrinkle, may be used as raw materials.

Claims (8)

A first step of bringing raw milk into contact with a cation exchange resin to obtain decalcified milk having a calcium content (mg / 100 g) / non-fat milk solid content (mass%) of 5.2 or less;
A second step of adjusting the pH of the decalcified milk to 5.7-6.5 to obtain a pH-adjusted milk;
A method for producing heat-sterilized milk, comprising a third step of heat-sterilizing the pH-adjusted milk. Raw material milk and cation exchange resin are contacted to obtain ion-exchanged milk, and the ion-exchanged milk and raw material milk are mixed to obtain a calcium content (mg / 100 g) / non-fat milk solid content (mass%). A first step of obtaining a decalcified milk having a pH of 5.2 or less;
A second step of adjusting the pH of the decalcified milk to 5.7-6.5 to obtain a pH-adjusted milk;
A method for producing heat-sterilized milk, comprising a third step of heat-sterilizing the pH-adjusted milk.   The method for producing heat-sterilized milk according to claim 1 or 2, wherein the second step is a step of adding an acid to decalcified milk.   The method for producing heat-sterilized milk according to claim 3, wherein the acid is an acid selected from hydrochloric acid, carbonic acid, phosphoric acid, lactic acid, sulfuric acid, malic acid, and tartaric acid.   The method for producing heat-sterilized milk according to claim 3, wherein the acid is hydrochloric acid.   The method for producing heat-sterilized milk according to any one of claims 1 to 5, wherein monovalent ions are removed by desalting and concentrating the pH-adjusted milk between the second step and the third step.   7. The heat-sterilized milk according to any one of claims 1 to 6, wherein the raw milk is any of whole milk, whole milk concentrated milk, whole milk powder solution, skim milk, skim milk concentrate, and skim milk powder solution. Method.   Heat-sterilized milk obtained by the production method according to claim 1.