JP2018038359A - Milk concentrate and method for producing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a milk concentrate in which the milk flavor is not impaired while the thermal stability is ensured, and to provide a method for producing the same.SOLUTION: The method for producing milk concentrate according to the present invention is a method for producing thermally stable milk concentrate and comprises a pH adjustment step and a milk concentrate preparation step. In the pH adjustment step, the pH of a raw milk is adjusted within a range of from 5.5 or more to less than 6.5 to prepare a pH adjusted raw milk. In the milk concentrate preparation step, the pH adjusted raw milk is subjected to ultrafiltration treatment to prepare a milk concentrate.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a milk concentrate, in particular a milk protein concentrate and a method for producing the same.

  In the past, it has been proposed to “decalcinate skim milk using a cation exchange resin to produce a milk protein concentrate” (for example, JP 2010-502182 A, JP 2011-024589 A). (See the official gazette). Such a milk protein concentrate (milk concentrate) has high heat stability and is used as a useful raw material for various dairy products such as prepared milk powder, beverages, fermented milk, and ice cream.

Japanese translation of PCT publication 2010-502182 JP 2011-024589 A

  However, when a dairy product is prepared using the milk concentrate obtained as described above, although the salty taste and “egumi” of the dairy product are weakened, the milk flavor tends to be insufficient.

  The subject of this invention is providing the milk concentrate which does not impair milk flavor, and its manufacturing method, ensuring heat stability.

  The method for producing a milk concentrate according to the first aspect of the present invention is a method for producing a thermally stable (excellent thermal stability) milk concentrate, comprising a pH adjustment step and a milk concentrate preparation step. In the pH adjustment step, the pH of the raw material milk is adjusted within the range of 5.5 or more and less than 6.5, and the pH adjusted raw material milk is prepared. In the milk concentrate preparation step, the pH-adjusted raw material milk is ultrafiltered to prepare a milk concentrate. In addition, before advancing to a milk concentrate preparation process from a pH adjustment process, it is preferable to leave the pH adjustment raw material milk still for a predetermined time or to stir. This is because ions such as calcium are sufficiently dissociated (released) from proteins (that is, casein and the like).

  In this method for producing a milk concentrate, the raw material milk is adjusted to fall within the range of 5.5 or more and less than 6.5, and then the raw material (that is, the pH-adjusted raw material milk) is subjected to an ultrafiltration treatment. Here, in the pH-adjusted raw material milk, calcium ions, magnesium ions and the like electrostatically bound to the protein are in a partially dissociated state (normally, the pH of the pH-adjusted raw material milk is 5.2). In the following, all calcium ions and magnesium ions are dissociated.) Then, the partially dissociated calcium ions, magnesium ions and the like are discharged together with the moisture of the permeate when the pH-adjusted raw material milk is subjected to an ultrafiltration treatment. As a result, a milk concentrate in which calcium ions, magnesium ions and the like remain moderately is prepared. For this reason, the heat stability of this milk concentrate is improved, and milk flavor is not impaired in the dairy product manufactured using it. Furthermore, in this method for producing a milk concentrate, no ion exchange treatment is performed. For this reason, in the whole flow of the manufacturing method of a milk concentrate, an operation man-hour decreases and it can hold down manufacturing cost low. In addition, since the milk concentrate produced by this production method is excellent in thermal stability as described above, the operation in the heat sterilization process is complicated when producing dairy products using this milk concentrate as a raw material. There is no need to do it. For this reason, the milk concentrate manufactured by this manufacturing method can suppress the manufacturing cost of dairy products etc. low depending on the case.

  The above-described method for producing a milk concentrate preferably further includes a pH readjustment step. In the pH readjustment step, the pH of the milk concentrate is adjusted within the range of 6.5 or more and 7.0 or less. For this reason, the acidity of this milk concentrate can be suppressed. In the pH readjustment step, the quantitative balance of sodium ions and potassium ions in the milk concentrate can be adjusted by using sodium hydroxide and potassium hydroxide.

  In the above-described method for producing a milk concentrate, the raw milk is skim milk, and the milk concentrate is a milk protein concentrate (hereinafter also referred to as “Milk Protein Concentrate” (hereinafter abbreviated as “MPC”)). It is preferable. For this reason, while ensuring heat stability, when used as raw materials, such as dairy products, the milk protein concentrate which has not lost the milk flavor can be obtained.

  The milk concentrate which concerns on 2nd aspect of this invention is a milk concentrate manufactured by the manufacturing method of the above-mentioned milk concentrate. In addition, the composition of this milk concentrate has a protein content in the range of 9.0% to 15.5% by mass and an ash content of 0.40 per 20% by mass of the total solid content. The sodium content is in the range of 0.01% by mass to 0.10% by mass and the potassium content is 0.05% by mass to 0%. .40% by mass or less, calcium content in the range of 0.15% by mass or more and 0.40% by mass or less, and magnesium content in excess of 0.00% by mass to 0.03% by mass. Within the following range, the phosphorus content is in the range of 0.08% by mass or more and 0.25% by mass or less, and the chlorine content is in the range of more than 0.00% by mass to 0.35% by mass or less. It is. And dairy products rich in various milk flavors can be produced using this milk concentrate as a raw material.

The figure which showed the plot which shows the influence of pH which acts on the thermocoagulation time of the milk concentrate which concerns on Example 1 with the plot which shows the influence which pH has on the thermocoagulation time of the milk concentrate which concerns on the comparative example 1 It is.

  The milk concentrate which concerns on embodiment of this invention is manufactured through a pH adjustment process and a milk concentrate preparation process. Hereinafter, after describing the milk concentrate in detail, the production method and its application will be described in detail.

<Milk concentrate>
The milk concentrate according to the embodiment of the present invention includes raw milk, milk or special milk or skim milk (raw milk, milk or special milk from which milk fat has been removed) or partially skim milk (raw milk, milk or special milk). Concentrated milk (from which milk fat has been partially removed), for example, concentrated milk (raw milk, milk or special milk as defined in the Ministry of Health and Welfare Ordinance on Component Standards for Milk and Dairy Products) Milk solid content is 25.5% or more and milk fat content is 7.0% or more, or nonfat concentrated milk (raw milk, milk or special milk with milk fat removed) In which the solid content of non-fat milk is 18.5% or more and the number of bacteria (per 1 g by standard plate culture method) is 100,000 or less. Concentrated milk or special milk The milk solids content is less than 25.5% (hereinafter referred to as “non-Ministerial Concentrated Milk”), “raw milk, milk or special milk from which milk fat is removed, Milk protein concentrate (hereinafter abbreviated as “MPC”), although it may be a non-fat milk solid content of less than 18.5% (hereinafter referred to as “non-ordered non-fat concentrated milk”). It is also preferred that Hereinafter, for convenience of explanation, raw milk, milk, special milk, skim milk and partially skim milk may be collectively referred to as “raw milk”.

  Moreover, the milk concentrate which concerns on embodiment of this invention is a protein in the range of 9.0 mass% or more and 15.5 mass% or less, and 0.40 mass% or more and 1. Ash content in the range of 55% by mass or less, sodium (Na) in the range of 0.01% by mass or more and 0.10% by mass or less, potassium in the range of 0.05% by mass or more and 0.40% by mass or less (K ), Calcium (Ca) in the range of 0.15 mass% to 0.40 mass%, magnesium (Mg) in the range of more than 0.00 mass% to 0.03 mass%, 0.08 mass% or more It contains phosphorus (P) in the range of 0.25% by mass or less and chlorine (Cl) in the range of more than 0.00% by mass and 0.35% 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 within a range of 14.5% by mass or less, further preferably within a 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 the value falls within the range.

  The ash content of the milk concentrate according to the embodiment of the present invention is preferably in the range of 0.50% by mass or more and 1.55% by mass or less per 20% by mass of the total solid content, More preferably, it is in the range of 0.55 mass% or more and 1.50 mass% or less, more preferably in the range of 0.60 mass% or more and 1.50 mass% or less, and 0.65 mass% or more. More preferably, it is in the range of 1.45% by mass or less, and particularly preferably in the range of 0.70% by mass to 1.45% by mass.

  Moreover, content of sodium (Na) of the milk concentrate which concerns on embodiment of this invention exists in the range of 0.01 to 0.09 mass% per 20 mass% of total solid content. It is more preferable that it is in the range of 0.01% by mass or more and 0.08% by mass or less, more preferably in the range of 0.02% by mass or more and 0.08% by mass or less. It is particularly preferable that the content be in the range of from mass% to 0.07 mass%.

  Further, the content of potassium (K) in the milk concentrate according to the embodiment of the present invention is 0.05% by mass or more per 20% by mass of the total solid content, although it depends on the content of sodium (Na). It is preferably in the range of 0.38% by mass or less, more preferably in the range of 0.05% by mass or more and 0.36% by mass or less, and 0.06% by mass or more and 0.34% by mass or less. It is more preferable that it be within the range, and it is particularly preferable that it be within the range of 0.06 mass% or more and 0.32 mass% or less. The potassium (K) content is preferably 3 to 4 times the sodium (Na) content, and is 3.2 to 3.9 times the sodium (Na) content. More preferably, it is 3.4 to 3.8 times the content of sodium (Na), more preferably 3.6 to 3.7 times the content of sodium (Na). It is particularly preferred.

  In addition, the content of calcium (Ca) in the milk concentrate according to the embodiment of the present invention is in the range of 0.15% by mass to 0.36% by mass per 20% by mass of the total solid content. More preferably, it is in the range of 0.16% by mass to 0.34% by mass, more preferably in the range of 0.17% by mass to 0.32% by mass, It is particularly preferable that the content be in the range of mass% to 0.30 mass%.

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

  The content of phosphorus (P) in the milk concentrate according to the embodiment of the present invention is within the range of 0.10% by mass to 0.24% by mass per 20% by mass of the total solid content. More preferably, it is in the range of 0.11% by mass or more and 0.24% by mass or less, more preferably in the range of 0.12% by mass or more and 0.23% by mass or less, It is particularly preferable that the amount be in the range of from mass% to 0.23 mass%.

  In addition, the content of chlorine (Cl) in the milk concentrate according to the embodiment of the present invention is in the range of 0.01% by mass to 0.30% by mass per 20% by mass of the total solid content. It is more preferable that it is in the range of 0.03% by mass or more and 0.30% by mass or less, more preferably in the range of 0.05% by mass or more and 0.25% by mass or less, and 0.07% by mass. It is particularly preferable that the content be in the range of mass% to 0.25 mass%.

  Further, 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 to 22% by mass, and in the range of 16% by mass to 22% by mass. It is preferable that it is in the range of 18% by mass or more and 22% by mass or less, and more preferably in the range of 20% by mass or more and 22% by mass or less.

  Further, the heat coagulation time at 130 ° C. of the milk concentrate according to the embodiment of the present invention (the time until the coagulum is generated in the milk concentrate and the time until the viscosity of the milk concentrate is increased) is 2 It is preferably at least 4 minutes, more preferably at least 4 minutes, even more preferably at least 6 minutes, and particularly preferably at least 8 minutes.

<Method for producing milk concentrate>
The milk concentrate which concerns on embodiment of this invention is manufactured through a pH adjustment process and a milk concentrate preparation process as above-mentioned. In addition, when the milk concentrate according to the embodiment of the present invention is skim concentrated milk, non-decorated skim concentrated milk, or milk protein concentrate, a skim milk preparation step is preferably provided before the pH adjustment step. . Moreover, it is preferable that a pH readjustment process is provided after the milk concentration preparation process. Hereinafter, these steps will be described in detail.

(1) Skim milk preparation process In skim milk preparation process, skim milk or partial skim milk is prepared from raw milk, cow milk, or special milk. As used herein, “fat milk” refers to milk, fat or special milk from which milk fat has been removed. For example, “milk fat content of raw milk, milk or special milk is less than 0.5%. Etc. ”. In addition, “partially skim milk” as used herein refers to milk, milk or special milk from which milk fat has been partially removed. For example, “milk fat content of raw milk, milk or special milk is 0 0.5% or more and less than 3.0% ". In addition, as above-mentioned, skim milk preparation process does not necessarily have to be implemented. A commercially available product of defatted concentrated milk or non-decree defatted concentrated milk may be purchased and used as raw material milk (starting material) in the pH adjustment step.

  Examples of a method for preparing skim milk or partially skim milk from raw milk, milk or special milk include, for example, a method of centrifuging raw milk, milk or special milk (hereinafter also referred to as “centrifugation method”). There is a method of membrane separation treatment of milk fat of raw milk, milk or special milk (hereinafter also referred to as “membrane separation method”, for example, there is a microfiltration treatment). In addition, when employ | adopting the centrifugation method, it is preferable to centrifuge milk fat, keeping the temperature of raw milk, milk, or special milk in the range of 45 degreeC or more and 55 degrees C or less. In such a case, it is preferable to cool the obtained skim milk or partially skim milk before the pH adjustment step. In such a case, the cooling temperature is preferably in the range from the temperature at which the skim milk or partially skimmed milk is kept in a liquid state to 10 ° C or less, and more preferably in the range from 1 ° C to 5 ° C.

(2) pH adjustment step In the pH adjustment step, the pH of the raw material milk (for example, cooled raw material milk) is adjusted within the range of 5.5 or more and less than 6.5 to prepare the pH-adjusted raw material milk. In addition, it is preferable that pH is a predetermined value from the viewpoint of easy adjustment of the addition amount of alkali and easy maintenance of low viscosity. That is, in such a case, in the pH adjustment step, the pH of the pH-adjusted raw material milk is preferably in the range of 5.5 to 6.2, more preferably in the range of 5.5 to 6.0. Preferably, it is in the range of 5.5 or more and 5.8 or less. In addition, since the pH of raw material milk is normally in the range of 6.4 to 7.2, an acid is used in this pH adjustment step. For this acid, an acid that can be added to food, that is, an acid that is harmless to the human body, such as hydrochloric acid, lactic acid, acetic acid, and the like is used. Thus, when the pH of the raw material milk is adjusted to the acidic side, in the pH-adjusted raw material milk, calcium ions, magnesium ions and the like electrostatically attached to the protein are dissociated from the protein. And content (number) of calcium ion dissociated in raw material milk, etc. can be adjusted by adjusting pH of raw material milk suitably in the said range.

  In this pH adjustment step, it is preferable that the pH-adjusted raw material milk is allowed to stand or is stirred for a predetermined time after the above-described acid is added to the raw material 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 more preferably 4 hours or less. It is particularly preferred that Moreover, in this pH adjustment process, it is preferable to leave the pH-adjusted raw milk at a predetermined temperature or to stir. Here, the predetermined temperature is preferably in the range of not less than the temperature at which the pH-adjusted raw milk is kept in a liquid state and not more than 25 ° C, more preferably in the range of 1 to 20 ° C, and more preferably in the range of 2 to 15 ° C. It is more preferable that the temperature is in the range of not higher than ° C, and it is particularly preferable that the temperature is in the range of 3 ° C or higher and 10 ° C or lower.

(3) Milk concentrate preparation step In the milk concentrate preparation step, after the pH adjustment step, the pH-adjusted raw milk is subjected to an ultrafiltration treatment to prepare a milk concentrate (milk protein concentrate). At this time, calcium ions and magnesium ions dissociated in the pH adjustment step are separated from the pH-adjusted raw material milk (or milk concentrate) as a permeate. As a result, the target “milk concentrate with reduced content (concentration) of calcium and magnesium” is obtained. In addition, flat membranes, hollow fiber membranes, spiral membranes, ceramic membranes, rotating membranes, vibrating membranes, etc. are used for the ultrafiltration membrane used for ultrafiltration treatment, and the molecular weight cut off of the ultrafiltration membrane is , Preferably in the range of 8000 Da to 12000 Da, more preferably in the range of 9000 Da to 11000 Da, and even more preferably in the range of 9500 Da to 10500 Da. By the way, the lower limit of the concentration factor may vary depending on the type of raw material milk, but when the raw material milk is skim milk, for example, the concentration factor is preferably 2.5 times or more. More preferably, the concentration ratio is 1.5 times or more, more preferably 2 times or more when the raw material milk is raw milk. Moreover, although the upper limit of this concentration ratio can be determined by the degree of pressure resistance of the ultrafiltration membrane and the ultrafiltration apparatus, for example, when the raw material milk is skim milk, this concentration ratio is 4 times or less. Preferably, it is 3.5 times or less, and when the raw material milk is raw milk, the concentration factor is preferably 3 times or less, and more preferably 2.5 times or less. In addition, as a result of diligent investigation by the present inventors, the higher the concentration ratio, the higher the heat stability of the milk concentrate, and the smaller the amount of alkali added in the pH readjustment (neutralization) step. It has been shown that the viscosity of the milk concentrate is low.

(4) pH readjustment step In the pH readjustment step, the pH of the milk concentrate (eg, cooled milk concentrate, room temperature milk concentrate) is adjusted within the range of 6.5 to 7.0. A milk concentrate whose pH has been readjusted (hereinafter also referred to as “pH-adjusted milk concentrate”) is prepared. In addition, it is preferable that pH is a predetermined value from the viewpoint of easy improvement of thermal stability and easy maintenance of 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 to 6.9, and preferably in the range of 6.5 to 6.8. More preferably, it is more preferably in the range of 6.5 or more and 6.7 or less. Since the pH of the milk concentrate is usually in the range of 5.5 or more and less than 6.5, alkali is used in this pH readjustment step. As this alkali, an alkali that can be added to foods, that is, an alkali that is harmless to the human body, such as sodium hydroxide, potassium hydroxide, potassium carbonate and the like is used. At this time, the alkali is preferably used in the form of a dilute aqueous solution, specifically, more preferably used in the form of a 1 to 3N aqueous alkali solution, and more preferably in the form of a 2N aqueous alkali solution. preferable. At this time, sodium hydroxide and potassium hydroxide are mixed so that the ratio of sodium ions / potassium ions in the milk concentrate becomes the ratio of sodium ions / potassium ions in raw milk or a ratio close to that ratio. It is preferable to use a mixed aqueous solution. Specifically, it is more preferable to use a mixed aqueous solution in which sodium hydroxide: potassium hydroxide is 2 to 4: 8 to 6, and sodium hydroxide: potassium hydroxide is 3: 7. More preferably, a mixed aqueous solution is used.

  In this pH readjustment step, it is preferable that the pH-adjusted milk concentrate is allowed to stand or stirred for a predetermined time after adding the above-mentioned alkali to the 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 more preferably 4 hours or less. It is particularly preferred that In this pH readjustment step, it is preferable that the pH-adjusted milk concentrate is allowed to stand or is stirred at a predetermined temperature. Here, the predetermined temperature is preferably in the range of not less than the temperature at which the pH-adjusted milk concentrate is liquid and not more than 25 ° C, more preferably in the range of not less than 1 ° C and not more than 20 ° C, and more preferably not less than 2 ° C. It is more preferably within a range of 15 ° C. or less, and particularly preferably within a range of 3 ° C. or more and 10 ° C. or less.

<Application of milk concentrate>
The milk concentrate which concerns on embodiment of this invention can be used as one component of the raw material of dairy products. That is, this milk concentrate may be used alone as a raw material for dairy products (raw material milk), water, raw milk, pasteurized milk, skim milk, whole milk powder, skim milk powder, whole milk concentrate milk, skim milk It may be mixed with other raw materials such as concentrated milk, butter milk, butter, cream, cheese, etc. and used as a raw material for dairy products (a part of raw milk).

  The above-mentioned dairy products include, for example, milk drinks (including processed milk), yogurts, lactic acid bacteria drinks, fermented milk, ice creams, creams, cheeses and the like. In addition, arbitrary components can be added to this dairy product as needed. There are no particular restrictions on such optional ingredients, but sweeteners, acidulants, vegetables and fruits and seeds, vegetable juices and fruit juices and seed juices, and vegetables, which are ingredients mixed in general dairy products , Fruit and seed extracts, vitamins, minerals, nutrients such as peptides and amino acids, useful microorganisms such as lactic acid bacteria, bifidobacteria and propionic acid bacteria, useful microorganism cultures, useful microorganism fermentation products, royal jelly, Examples include existing functional materials such as glucosamine, astaxanthin and polyphenol, fragrances, pH adjusters, excipients, acidulants, colorants, emulsifiers, preservatives and the like. In this case, for example, glucose, fructose, maltose, sucrose, oligosaccharide, sugar, honey, maple syrup, agave syrup, balm sugar, molasses, molasses, glucose fructose liquid sugar, trehalose, maltose , Palatinose, xylitol, sorbitol, licorice extract, stevia processed sweetener, rahan fruit extract, thaumatin, glycerin, curculin, monelin, miraculin, erythritol and the like. These sweeteners not only give sweetness to dairy products, but also can suppress sourness and “eggumi”, so that 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 one component of the fermented milk raw mix. In the preparation of this fermented milk raw material mix, for example, raw materials such as milk concentrate and other optional ingredients (for example, sweeteners, sour agents, minerals, vitamins, flavors, etc.) are added (mixed), heated, and mixed.・ It is dissolved. In addition to milk concentrate, water, raw milk, pasteurized milk, whole milk powder, whole fat concentrated milk, buttermilk, butter, cream, cheese, etc. are added to this raw material mix, heated, mixed, dissolved, etc. May be. In addition, whey protein concentrate (WPC), whey protein isolate (WPI), α-lactalbumin (α-La), β-lactoglobulin (β-Lg), etc. are added to this raw material mix and heated. -You may mix and dissolve.

  In addition, when the above-mentioned dairy product is fermented milk, this fermented milk is the same as the conventional method for producing fermented milk, the raw material mix preparation step, the raw material mix (heating) sterilization step, the raw material mix cooling step, It is manufactured through processes such as a starter addition process, a fermentation process, and a cooling process for fermented milk. At this time, in the raw material mix preparation step, as described above, the raw materials are added, heated, mixed, dissolved (prepared), and the like. In addition, what is necessary is just to employ | adopt suitably the process conditions at the time of manufacture of general fermented milk in each above-mentioned process. Moreover, it is preferable that the raw material mix (heating) sterilization step, the raw material mix cooling step, the starter addition step, the fermentation step, and the fermented milk cooling step are performed in this order.

<Features of milk concentrate>
The milk concentrate obtained as described above has a relatively high concentration of calcium, magnesium, etc., as compared with conventional milk concentrates, but has improved or maintained good thermal stability. And dairy products prepared using this milk concentrate as a raw material have a relatively high concentration of calcium and magnesium, etc., compared with dairy products prepared using conventional milk concentrate as a raw material, but have a milk flavor and other physical properties. Improved or maintained well.

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

Example 1
1. Preparation of milk concentrate First, raw milk was centrifuged at 50 ° C. using a cream separator (Separator F-3, volume: 0.37 L, manufactured by elecream) (rotation speed: 7000-8000 rpm, processing flow rate: 315 L / h). , Treatment time: 4.2 seconds, gravitational acceleration: 1500-4400 G), skim milk was prepared, and the skim milk was cooled to 5 ° C. (skim milk preparation step). Next, 2N hydrochloric acid aqueous solution was added to the cooled skimmed milk to adjust the pH of the skimmed milk to 5.7, and left at 5 to 10 ° C. for 2 hours (pH adjusting step). Next, using the module of a hollow fiber membrane (Romicon Hollow fiber CTG3 "HF25-43 PM-10 manufactured by Koch, fractional molecular weight: 10,000 Da, membrane area: 2.3 m ² ) 3. A milk concentrate (milk protein concentrate) was produced by ultrafiltration (UF) treatment at a concentration factor of 2 times (milk concentrate preparation step).

  In addition, the hollow fiber membrane was wash | cleaned using the alkaline aqueous solution which added chlorine at 200 ppm before ultrafiltration processing skim milk using the module of a hollow fiber membrane. And after cooling a hollow fiber membrane, circulating cold water (3-5 degreeC) to the module of a hollow fiber membrane, this cooling water was discharged | emitted from the module of the hollow fiber membrane. Then, the above-mentioned neglected skim milk (5 to 10 ° C.) was charged into a 20 L jacketed tank. Then, when the skim milk is ultrafiltered using the module of the hollow fiber membrane, the module of the hollow fiber membrane is connected to this tank by piping or the like, and the tank is indirectly cooled, and this piping A cooling pipe was provided in the middle of this to cool the pipe indirectly. Concentration ratio for ultrafiltration treatment of skim milk is as follows: skim milk preparation amount (processing amount), permeate processing flow rate (permeation flow rate), retentate (concentrated liquid) total solid concentration and protein concentration Etc.

  And after dividing this milk concentrate into five, sodium hydroxide is made so that the ratio of sodium (ion) / potassium (ion) of each milk concentrate is equivalent to the ratio in milk (about 4/15). And a 2N sodium hydroxide / potassium hydroxide mixed aqueous solution containing potassium hydroxide in a ratio of 3: 7 (molar ratio) was added to adjust the pH of each milk concentrate to 6.40 in a constant temperature environment at 20 ° C. 6.45, 6.50, 6.60, 6.75, and a pH-adjusted milk concentrate (pH readjusted milk concentrate) was prepared (pH readjustment step).

2. Physical property confirmation test (1) Thermal stability confirmation test First, each pH readjusted milk concentrate was weighed and sealed in a 14 mL round-bottom vial. Next, this round bottom vial is immersed in a 130 ° C. oil bath, and each pH readjusted milk concentrate is visually confirmed while shaking the round bottom vial, and the pH readjusted milk concentrate is concentrated. The time until the solidified material was generated in the product was measured, and this measurement time was defined as “thermal solidification time”. Finally, 2 hours after the time of pH readjustment, the pH of each pH readjusted milk concentrate was measured at 10 ° C., 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. The graph of the data published in Table 1 is shown in FIG.

(2) Sensory test (2-1)
Fermented milk was prepared by using the pH-reconstituted milk concentrate as raw material milk, and a sensory test was performed on the fermented milk. Hereinafter, after explaining the preparation method of the fermented milk, a sensory test is explained in full 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-adjusted milk concentrate was heated at a temperature of 95 ° C. by a batch method using a vat.

  Next, each pH-reconstituted milk concentrate sterilized by heating was placed in a vat and the temperature was adjusted to 43 ° C. A mixed starter of Filus bacteria) was added to 2% by mass, and they were stirred and held for 10 minutes.

  Next, 70 g of each pH-reconstituted milk concentrate to which a lactic acid bacteria starter was added was filled into a cup of about 100 mL. On the other hand, each pH readjusted milk concentrate remaining here was left in the vat. Subsequently, the cups and vats were placed in a 43 ° C. incubator to ferment each pH-reconstituted milk concentrate. And when the pH of each pH readjusted milk concentrate reaches 4.6, put the fermented milk in a cup in a refrigerator (3-5 ° C.) and hold it overnight (about 12 hours). A type of fermented milk was produced. On the other hand, when the pH of each pH-reconcentrated milk concentrate reaches 4.6, the fermented milk with vat is stirred and cooled in a cold water bath (3 to 5 ° C.) to obtain soft type fermented milk. Manufactured.

(2-2)
Five expert panels eat the above-mentioned hard type and soft type fermented milk in a cooled (5 ° C) state, and have sweetness, saltiness, sourness, gummy, milk flavor, smoothness, and unpleasant odor. The strength (degree) was evaluated in five levels. At this time, the majority of the specialized panel said that the fermented milk of Example 1 (described above) has less puffiness and rich milk flavor and smoothness compared to the fermented milk of Comparative Example 1 (described later). evaluated.

(Comparative Example 1)
In the preparation of the milk concentrate, the pH-adjusted milk was omitted in the same manner as in Example 1 except that the skim milk was subjected to ultrafiltration treatment without adjusting the pH of the cooled skim milk. A concentrate was prepared. And it carried out similarly to Example 1, and the heat stability confirmation test was done about the pH readjusted milk concentrate. In Comparative Example 1, the pH readjustment process was performed only for comparison with Example 1 and Example 2, and the patentability of pH readjustment in the present invention is not denied.

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

<Consideration for Examples and Comparative Examples>
As is apparent from FIG. 1, within the range of pH 6.4 to 6.75, the pH-reconstituted milk concentrate prepared in Example 1 is changed to the pH-reconstituted milk concentrate prepared in Comparative Example 1. In comparison, it was found that the thermal stability is excellent. In addition, within the range of pH 6.4 to 6.5, the heat stability of the pH readjusted milk concentrate prepared in Example 1 is a level that can sufficiently withstand the production of fermented milk and the like. Within the range of 6.5 to around 6.7, the thermal stability of the pH-reconstituted milk concentrate prepared in Example 1 should be evaluated as a significant level.

Claims (6)

A method for producing a thermally stable milk concentrate, comprising:
Adjusting the pH of the raw material milk within the range of 5.5 to less than 6.5, and preparing a pH-adjusted raw material milk; and
A milk concentrate production method comprising: a milk concentrate preparation step of preparing a milk concentrate by subjecting the pH-adjusted raw milk to ultrafiltration treatment. The manufacturing method of the milk concentrate of Claim 1 further equipped with the pH readjustment process which adjusts the pH of the said milk concentrate in the range of 6.5 or more and 7.0 or less. The raw milk is skim milk,
The method for producing a milk concentrate according to claim 1 or 2, wherein the milk concentrate is a milk protein concentrate.   The milk concentrate manufactured by the manufacturing method of the milk concentrate of any one of Claim 1 to 3. The protein content is within the range of 9.0% to 15.5% by mass and the ash content is 0.40% to 1.55% by mass with respect to 20% by mass of the total solid content. Within the range, the sodium content is in the range of 0.01% by mass to 0.10% by mass, and the potassium content is in the range of 0.05% by mass to 0.40% by mass. The content of calcium is in the range of 0.15% by mass to 0.40% by mass, the content of magnesium is in the range of more than 0.00% by mass and 0.03% by mass, and the content of phosphorus Milk concentrate in which the amount is in the range of 0.08% to 0.25% by weight and the chlorine content is in the range of more than 0.00% to 0.35% by weight.   A dairy product produced using the milk concentrate according to claim 4 or 5 as a raw material.

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