JP7659491B2 - Milk Protein Concentrates and Dairy Products - Google Patents

Description

The present invention relates to a milk protein concentrate. The present invention also relates to a dairy product produced using the milk protein concentrate as a raw material.

In the past, it has been proposed to "use a cation exchange resin to remove calcium from skim milk and produce a milk protein concentrate" (see, for example, JP 2010-502182 A and JP 2011-024589 A). Such milk protein concentrates (milk concentrates) have high thermal stability and are used as useful raw materials for various dairy products such as infant formula, beverages, fermented milk, and ice cream.

Special Publication No. 2010-502182 JP 2011-024589 A

However, when a dairy product is prepared using the milk concentrate obtained as described above, although the saltiness and bitterness of the dairy product are reduced, the dairy flavor tends not to be sufficient.

The objective of the present invention is to provide a milk concentrate that maintains heat stability without impairing the milk flavor, and a method for producing the same.

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, and includes a pH adjustment step, a first milk concentrate preparation step, a water addition step, and a second milk concentrate preparation step. In the pH adjustment step, the pH of the raw milk is adjusted to a range of 5.5 or more and less than 6.5 to prepare a pH-adjusted raw milk. In the first milk concentrate preparation step, the pH-adjusted raw milk is ultrafiltered to prepare a first milk concentrate. It is preferable to leave the pH-adjusted raw milk stationary or to stir it for a predetermined time before proceeding from the pH adjustment step to the first milk concentrate preparation step. This is to sufficiently dissociate (liberate) ions such as calcium from proteins (i.e., casein, etc.). In the water addition step, water of a mass of 0.6 times or more the mass of the first milk concentrate is added to the first milk concentrate to prepare a diluted first milk concentrate. It is preferable that the water is adjusted to a temperature in the range of more than 0°C and less than 10°C. In the second milk concentrate preparation process, the diluted first milk concentrate is ultrafiltered to prepare the second milk concentrate.

In this method for producing a milk concentrate, the pH of the raw milk is adjusted to a range of 5.5 or more and less than 6.5, and then the raw material (i.e., pH-adjusted raw milk) is subjected to ultrafiltration. Here, in the pH-adjusted raw milk, calcium ions, magnesium ions, etc. electrostatically bonded to proteins are partially dissociated (normally, when the pH of the pH-adjusted raw milk is 5.2 or less, all calcium ions, magnesium ions, etc. are dissociated). Then, when the pH-adjusted raw milk is subjected to ultrafiltration twice, the partially dissociated calcium ions, magnesium ions, etc. are discharged together with the water content of the permeate. As a result, a milk concentrate is prepared in which calcium ions, magnesium ions, etc. remain in a moderate amount. Therefore, the heat stability of this milk concentrate is improved, and the milk flavor is not impaired in dairy products produced using it. Furthermore, in this method for producing a milk concentrate, no ion exchange treatment is performed. Therefore, the number of work steps is reduced in the overall flow of the method for producing a milk concentrate, and production costs can be kept low. In addition, as mentioned above, the milk concentrate produced by this manufacturing method has excellent heat stability, so when this milk concentrate is used as a raw material to produce dairy products, etc., there is no need to complicate the operations in the heat sterilization process. Therefore, in some cases, the milk concentrate produced by this manufacturing method can reduce the production costs of dairy products, etc.

The above-mentioned method for producing a milk concentrate preferably further includes a pH readjustment step. In the pH readjustment step, the pH of the second milk concentrate is adjusted to within a range of 6.5 to 7.0. This makes it possible to suppress the sourness of the second milk concentrate. In addition, in the pH readjustment step, the quantitative balance of sodium ions and potassium ions in the second milk concentrate can be adjusted by using sodium hydroxide and potassium hydroxide.

In addition, in the above-mentioned method for producing a milk concentrate, it is preferable that the raw milk is skim milk and the milk concentrate is a milk protein concentrate (also called "Milk Protein Concentrate" (hereinafter abbreviated as "MPC"). This ensures thermal stability and, when used as a raw material for dairy products, etc., a milk protein concentrate that does not lose its milk flavor can be obtained.

The milk concentrate according to the second aspect of the present invention is a milk concentrate produced by the above-mentioned method for producing a milk concentrate. The composition of this milk concentrate is such that, per 20% by mass of the total solid content, the protein content is in the range of 9.0% by mass to 15.5% by mass, the ash content is in the range of 0.30% by mass to 1.45% by mass, the sodium content is in the range of 0.01% by mass to 0.09% by mass, the potassium content is in the range of 0.04% by mass to 0.38% by mass, the calcium content is in the range of 0.15% by mass to 0.38% by mass, the magnesium content is in the range of more than 0.00% by mass to 0.03% by mass, the phosphorus content is in the range of more than 0.08% by mass to 0.23% by mass, and the chlorine content is in the range of more than 0.00% by mass to 0.30% by mass. This milk concentrate can be used as a raw material to produce various dairy products rich in milk flavor.

FIG. 1 is a plot diagram showing the effect of pH on the thermal coagulation time of the milk concentrate of Example 1, together with a plot diagram showing the effect of pH on the thermal coagulation time of the milk concentrate of Comparative Example 1.

The milk concentrate according to the embodiment of the present invention is produced through a pH adjustment step, a first milk concentrate preparation step, a water addition step, and a second milk concentrate preparation step. Below, the milk concentrate will be described in detail, followed by a detailed description of its production method and its uses.

<Milk concentrate>
The milk concentrate according to the embodiment of the present invention is a concentrate of raw milk, cow's milk, special cow's milk, skim milk (raw milk, cow's milk, or special cow's milk from which milk fat has been removed), or partially skim milk (raw milk, cow's milk, or special cow's milk from which milk fat has been partially removed), and is, for example, concentrated milk (raw milk, cow's milk, or special cow's milk from which milk solids have been concentrated and milk fat has been removed from 25.5% or more and 7.0% or more) as specified in the "Ministry of Health, Labour and Welfare Ordinance on the Compositional Standards of Milk and Dairy Products" and skim milk (raw milk, cow's milk, or special cow's milk from which milk fat has been removed). The milk protein concentrate may be a milk protein concentrate (hereinafter abbreviated as "Milk Protein Concentrate" (MPC)) or a milk protein concentrate (hereinafter abbreviated as "Milk Protein Concentrate" (MPC)). The milk protein concentrate may be a milk protein concentrate (hereinafter abbreviated as "Milk Protein Concentrate"), ...

The milk concentrate according to the embodiment of the present invention also contains, per 20% by mass of total solids, protein in the range of 9.0% by mass to 15.5% by mass, ash in the range of 0.30% by mass to 1.45% by mass, sodium (Na) in the range of 0.01% by mass to 0.09% by mass, potassium (K) in the range of 0.04% by mass to 0.38% by mass, calcium (Ca) in the range of 0.15% by mass to 0.38% by mass, magnesium (Mg) in the range of more than 0.00% by mass to 0.03% by mass, phosphorus (P) in the range of 0.08% by mass to 0.23% by mass, and chlorine (Cl) in the range of more than 0.00% by mass to 0.30% by mass.

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 to 15.5% by mass, more preferably in the range of 10.5% by mass to 15.0% by mass, even more preferably in the range of 11.0% by mass to 15.0% by mass, even more preferably in the range of 11.5% by mass to 14.5% by mass, even more preferably in the range of 12.0% by mass to 14.0% by mass, and particularly preferably in the range of 12.5% by mass to 13.5% by mass, per 20% by mass of the total solids.

The ash content of the milk concentrate according to the embodiment of the present invention is preferably in the range of 0.40% by mass to 1.45% by mass, more preferably in the range of 0.45% by mass to 1.40% by mass, even more preferably in the range of 0.50% by mass to 1.35% by mass, even more preferably in the range of 0.55% by mass to 1.35% by mass, and particularly preferably in the range of 0.60% by mass to 1.30% by mass, per 20% by mass of the total solids.

The sodium (Na) content of the milk concentrate according to the embodiment of the present invention is preferably in the range of 0.01% by mass to 0.08% by mass, more preferably in the range of 0.01% by mass to 0.07% by mass, even more preferably in the range of 0.02% by mass to 0.07% by mass, and particularly preferably in the range of 0.02% by mass to 0.06% by mass, per 20% by mass of the total solids.

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

The calcium (Ca) content of the milk concentrate according to the embodiment of the present invention is preferably in the range of 0.15% by mass to 0.34% by mass, more preferably in the range of 0.16% by mass to 0.32% by mass, even more preferably in the range of 0.17% by mass to 0.30% by mass, and particularly preferably in the range of 0.18% by mass to 0.28% by mass, per 20% by mass of the total solids.

The magnesium (Mg) content of the milk concentrate according to the embodiment of the present invention is preferably in the range of more than 0.00% by mass and not more than 0.02% by mass per 20% by mass of the total solids, and more preferably in the range of more than 0.00% by mass and not more than 0.01% by mass.

The phosphorus (P) content of the milk concentrate according to the embodiment of the present invention is preferably in the range of 0.08% by mass to 0.22% by mass, more preferably in the range of 0.09% by mass to 0.22% by mass, even more preferably in the range of 0.10% by mass to 0.21% by mass, and particularly preferably in the range of 0.11% by mass to 0.21% by mass, per 20% by mass of the total solids.

The chlorine (Cl) content of the milk concentrate according to the embodiment of the present invention is preferably in the range of 0.01% by mass to 0.25% by mass, more preferably in the range of 0.03% by mass to 0.25% by mass, even more preferably in the range of 0.05% by mass to 0.20% by mass, and particularly preferably in the range of 0.07% by mass to 0.20% by mass, per 20% by mass of the total solids.

Furthermore, the total solids 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, preferably in the range of 16% by mass to 22% by mass, more preferably in the range of 18% by mass to 22% by mass, and even more preferably in the range of 20% by mass to 22% by mass.

The thermal coagulation time of the milk concentrate according to the embodiment of the present invention at 130°C (the time until coagulation occurs in the milk concentrate or the time until the viscosity of the milk concentrate increases) is preferably 2 minutes or more, more preferably 4 minutes or more, even more preferably 6 minutes or more, and particularly preferably 8 minutes or more.

<Method of producing milk concentrate>
As described above, the milk concentrate according to the embodiment of the present invention is produced through a pH adjustment step, a first milk concentrate preparation step, a water addition step, and a second milk concentrate preparation step. In addition, when the milk concentrate according to the embodiment of the present invention is skim milk concentrate, non-Ministry Ordinance skim milk concentrate, or milk protein concentrate, it is preferable to provide a skim milk preparation step before the pH adjustment step. In addition, it is preferable to provide a pH readjustment step after the second milk concentrate preparation step. These steps will be described in detail below.

(1) Skim milk preparation process In the skim milk preparation process, skim milk or partially skim milk is prepared from raw milk, cow's milk or special milk. The term "skim milk" as used herein means raw milk, cow's milk or special milk from which milk fat has been removed, for example, "raw milk, cow's milk or special milk with milk fat content of less than 0.5%". The term "partially skim milk" as used herein means raw milk, cow's milk or special milk from which milk fat has been partially removed, for example, "raw milk, cow's milk or special milk with milk fat content of 0.5% or more and less than 3.0%". As described above, the skim milk preparation process does not necessarily have to be carried out. Commercially available skim concentrated milk or non-Ministry Ordinance skim concentrated milk may be purchased and used as raw milk (starting material) in the pH adjustment process.

Methods for preparing skim milk or partially skim milk from raw milk, cow's milk, or special milk include, for example, a method of subjecting milk fat from raw milk, cow's milk, or special milk to centrifugation (hereinafter also referred to as "centrifugation method"), and a method of subjecting milk fat from raw milk, cow's milk, or special milk to membrane separation (hereinafter also referred to as "membrane separation method"; for example, microfiltration). When using centrifugation, it is preferable to centrifuge the milk fat while keeping the temperature of the raw milk, cow's milk, or special milk within the range of 45°C to 55°C. 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 within the range of from the temperature at which the skim milk or partial skim milk remains liquid to 10°C, and more preferably within the range of from 1°C to 5°C.

(2) pH Adjustment Step In the pH adjustment step, the pH of raw milk (e.g., cooled raw milk) is adjusted to a range of 5.5 or more and less than 6.5 to prepare pH-adjusted raw milk. In addition, from the viewpoint of ease of adjusting the amount of alkali added and ease of maintaining low viscosity, it is preferable that the pH is a predetermined value. That is, in such a case, in the pH adjustment step, the pH of the pH-adjusted raw milk is preferably in the range of 5.5 or more and 6.2 or less, more preferably in the range of 5.5 or more and 6.0 or less, and even more preferably in the range of 5.5 or more and 5.8 or less. In addition, since the pH of raw milk is usually in the range of 6.4 or more and 7.2 or less, an acid is used in this pH adjustment step. And, as 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, etc., is used. In this way, when the pH of the raw milk is adjusted to the acidic side, calcium ions, magnesium ions, etc. electrostatically attached to proteins in the pH-adjusted raw milk are dissociated from the proteins. By appropriately adjusting the pH of the raw material milk within the above range, the content (number) of calcium ions, magnesium ions, etc. dissociated in the raw material milk can be adjusted.

In addition, in this pH adjustment process, after adding the above-mentioned acid to the raw milk, it is preferable to leave the pH-adjusted raw milk to stand or stir for a predetermined time. Here, this predetermined time is preferably 0.5 hours or more, more preferably 1 hour or more, even more preferably 1.5 hours or more, and particularly preferably 2 hours or more. And, although there is no particular upper limit to this predetermined time, for example, the predetermined time is preferably 10 hours or less, more preferably 8 hours or less, even more preferably 6 hours or less, and particularly preferably 4 hours or less. Also, in this pH adjustment process, it is preferable to leave the pH-adjusted raw milk to stand or stir at a predetermined temperature. Here, this predetermined temperature is preferably within the range of a temperature at which the pH-adjusted raw milk remains liquid and 25°C or less, more preferably within the range of 1°C to 20°C, even more preferably within the range of 2°C to 15°C, and particularly preferably within the range of 3°C to 10°C.

(3) First milk concentrate preparation step In the first milk concentrate preparation step, after the pH adjustment step, the pH-adjusted raw milk is ultrafiltered to prepare a first milk concentrate (first milk protein concentrate). At this time, calcium ions, magnesium ions, etc. dissociated in the pH adjustment step are separated from the pH-adjusted raw milk (or the first milk concentrate) as permeate. In addition, flat membranes, hollow fiber membranes, spiral membranes, ceramic membranes, rotating membranes, vibrating membranes, etc. are used as ultrafiltration membranes used in the ultrafiltration process, and the molecular weight cutoff 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. Incidentally, the lower limit of this concentration ratio may vary depending on the type of raw milk, etc., but for example, when the raw milk is skim milk, the concentration ratio is preferably 2.5 times or more, more preferably 3 times or more, and when the raw milk is raw milk, the concentration ratio is preferably 1.5 times or more, more preferably 2 times or more. The upper limit of this concentration ratio can be determined by the degree of pressure resistance of the ultrafiltration membrane and the ultrafiltration device, but for example, when the raw milk is skim milk, the concentration ratio is preferably 4 times or less, more preferably 3.5 times or less, and when the raw milk is raw milk, the concentration ratio is preferably 3 times or less, more preferably 2.5 times or less. In addition, the inventor's intensive research has revealed that the higher the concentration ratio, the higher the thermal stability of the milk concentrate, the smaller the amount of alkali required to be added in the pH readjustment (neutralization) process, and the lower the viscosity of the second milk concentrate after the pH readjustment process.

(4) Water Addition Step In the water addition step, water of a mass of 0.6 times or more of the mass of the first milk concentrate is added to the first milk concentrate to prepare a first milk concentrate dilution. This water may be a buffer solution or the like. The amount of water added can be determined by the capacity of the ultrafiltration membrane device and the tank, and is preferably in the range of 0.6 times or more and 2 times or less, more preferably in the range of 0.7 times or more and 1.5 times or less, and even more preferably in the range of 0.8 times or more and 1 times or less. In addition, from the viewpoint of suppressing the growth of general bacteria, the temperature of this water is preferably in the range of more than 0 ° C. and 20 ° C. or less, more preferably in the range of 1 ° C. or more and 20 ° C. or less, more preferably in the range of 2 ° C. or more and 15 ° C. or less, and particularly preferably in the range of 3 ° C. or more and 10 ° C. or less.

In addition, in this water addition step, after adding the above-mentioned water to the first milk concentrate, it is preferable to leave the first milk concentrate diluted product to stand or stir for a predetermined time. Here, this predetermined time is preferably 0.1 hours or more, more preferably 0.3 hours or more, even more preferably 0.5 hours or more, and particularly preferably 1 hour or more. And, although there is no particular upper limit to this predetermined time, for example, the predetermined time is preferably 10 hours or less, more preferably 8 hours or less, even more preferably 6 hours or less, and particularly preferably 4 hours or less. Also, in this water addition step, it is preferable to leave the first milk concentrate diluted product to stand or stir at a predetermined temperature. Here, this predetermined temperature is preferably within a range of from a temperature at which the first milk concentrate diluted product remains liquid to 25°C or less, more preferably within a range of from 1°C to 20°C, even more preferably within a range of from 2°C to 15°C, and particularly preferably within a range of from 3°C to 10°C.

(5) Second milk concentrate preparation step In the second milk concentrate preparation step, the first milk concentrate diluted with water in the water addition step, i.e., the first milk concentrate diluted product, is subjected to ultrafiltration to prepare a second milk concentrate (second milk protein concentrate). At this time, calcium ions, magnesium ions, etc. dissociated in the pH adjustment step are separated as permeate from the first milk concentrate diluted product (or the second milk concentrate). As a result, the desired "milk concentrate with reduced calcium and magnesium content (concentration)" is obtained. In addition, flat membranes, hollow fiber membranes, spiral membranes, ceramic membranes, rotating membranes, vibrating membranes, etc. are used as ultrafiltration membranes subjected to ultrafiltration treatment, and the molecular weight cutoff 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. In addition, as this ultrafiltration membrane, the ultrafiltration membrane used in the first milk concentrate preparation process may be used as it is, or a new ultrafiltration membrane may be used. In the latter case, the same type of ultrafiltration membrane as the ultrafiltration membrane used in the first milk concentrate preparation process may be used, or a different type of ultrafiltration membrane from the ultrafiltration membrane used in the first milk concentrate preparation process may be used. Meanwhile, the lower limit of this concentration ratio may change depending on the type of raw milk, etc., but for example, when the raw milk is skim milk, this concentration ratio is preferably 1.5 times or more, more preferably 1.8 times or more, and when the raw milk is raw milk, this concentration ratio is preferably 1.3 times or more, more preferably 1.6 times or more. The upper limit of the concentration ratio can be determined depending on the pressure resistance of the ultrafiltration membrane and the ultrafiltration device, but for example, when the raw milk is skim milk, the concentration ratio is preferably 3.5 times or less, more preferably 3 times or less, and when the raw milk is raw milk, the concentration ratio is preferably 2.8 times or less, more preferably 2.3 times or less. The concentration ratio is set to be less than the concentration ratio in the first milk concentrate preparation step.

(6) pH readjustment step In the pH readjustment step, the pH of the second milk concentrate (for example, the cooled second milk concentrate, the room temperature second milk concentrate) is adjusted to a range of 6.5 to 7.0 to prepare a milk concentrate with a readjusted pH (hereinafter also referred to as a "pH-adjusted milk concentrate" or "pH-adjusted second milk concentrate"). In addition, from the viewpoint of ease of improving thermal stability and ease of maintaining low viscosity, it is preferable that the pH is a predetermined value. That is, in the pH readjustment step, the pH of the pH-adjusted milk concentrate is preferably set to a range of 6.5 to 6.9, more preferably set to a range of 6.5 to 6.8, and even more preferably set to a range of 6.5 to 6.7. In addition, since the pH of the second milk concentrate is usually in the range of 5.5 to less than 6.5, an alkali is used in this pH readjustment step. As the alkali, an alkali that can be added to food, that is, an alkali that is harmless to the human body, such as sodium hydroxide, potassium hydroxide, potassium carbonate, etc., is used. In this case, the alkali is preferably used in the form of a dilute aqueous solution, more preferably in the form of an aqueous alkali solution of 1 to 3 N, and even more preferably in the form of an aqueous alkali solution of 2 N. In addition, in this case, it is preferable to use a mixed aqueous solution of sodium hydroxide and potassium hydroxide so that the ratio of sodium ions to potassium ions in the second milk concentrate is the same as or close to the ratio of sodium ions to potassium ions in the raw milk, and more preferably to use a mixed aqueous solution of sodium hydroxide:potassium hydroxide in a ratio of 2 to 4:8 to 6, and even more preferably to use a mixed aqueous solution of sodium hydroxide:potassium hydroxide in a ratio of 3:7.

In addition, in this pH readjustment step, after adding the above-mentioned alkali to the second milk concentrate, it is preferable to leave the pH-adjusted milk concentrate to stand or stir for a predetermined time. Here, the predetermined time is preferably 0.1 hours or more, more preferably 0.3 hours or more, even more preferably 0.5 hours or more, and particularly preferably 1 hour or more. And, although there is no particular upper limit to this predetermined time, the predetermined time is, for example, preferably 10 hours or less, more preferably 8 hours or less, even more preferably 6 hours or less, and particularly preferably 4 hours or less. Also, in this pH readjustment step, it is preferable to leave the pH-adjusted milk concentrate to stand or stir at a predetermined temperature. Here, this predetermined temperature is preferably within a range of from a temperature at which the pH-adjusted milk concentrate remains liquid to 25°C or less, more preferably within a range of from 1°C to 20°C, even more preferably within a range of from 2°C to 15°C, and particularly preferably within a range of from 3°C to 10°C.

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

The above-mentioned dairy products include, for example, milk drinks (including processed milk), yogurts, lactobacillus drinks, fermented milk, ice creams, creams, cheeses, etc. Any ingredient can be added to the dairy product as needed. There are no particular limitations on such optional ingredients, but they include ingredients commonly used in dairy products, such as sweeteners, acidulants, vegetables, fruits, and seeds, vegetable juices, fruit juices, and seed juices, vegetable, fruit, and seed extracts, nutritional materials such as vitamins, minerals, peptides, and amino acids, useful microorganisms such as lactobacilli, bifidobacteria, and propionic acid bacteria, cultures of useful microorganisms, fermented products of useful microorganisms, existing functional materials such as royal jelly, glucosamine, astaxanthin, and polyphenols, flavorings, pH adjusters, excipients, acidulants, colorants, emulsifiers, and preservatives. In this case, examples of sweeteners include glucose, fructose, maltose, sucrose, oligosaccharides, sugar, honey, maple syrup, agave syrup, baum sugar, molasses, starch syrup, glucose-fructose liquid sugar, trehalose, maltose, palatinose, xylitol, sorbitol, licorice extract, stevia-processed sweetener, Monk fruit extract, thaumatin, glycerin, curculin, monellin, miraculin, erythritol, etc. These sweeteners not only give a sweet taste to dairy products, but also suppress sourness and bitterness, so it is preferable to actively add them during the production of dairy products.

When the dairy product is fermented milk, the milk concentrate may be used as one component of the raw material mix of the fermented milk. In the preparation of the raw material mix of the fermented milk, for example, raw materials such as the milk concentrate and other optional ingredients (for example, sweeteners, acidulants, minerals, vitamins, flavors, etc.) are added (blended), heated, mixed, and dissolved. In addition to the milk concentrate, water, raw milk, pasteurized milk, whole milk powder, whole fat concentrated milk, buttermilk, butter, cream, cheese, etc. may be added, heated, mixed, dissolved, etc. to this raw material mix. In addition, whey protein concentrate (WPC), whey protein isolate (WPI), α-lactalbumin (α-La), β-lactoglobulin (β-Lg), etc. may be added, heated, mixed, and dissolved to this raw material mix.

When the dairy product is fermented milk, the fermented milk is produced through the steps of blending the raw material mix, sterilizing the raw material mix (by heating), cooling the raw material mix, adding a starter, fermenting, and cooling the fermented milk, as in conventional fermented milk production methods. In this case, in the blending step of the raw material mix, the raw materials are added, heated, mixed, dissolved (blended), etc., as described above. In each of the above steps, the processing conditions used in the production of general fermented milk may be appropriately adopted. It is also preferable that the steps of sterilizing the raw material mix (by heating), cooling the raw material mix, adding a starter, fermenting, and cooling the fermented milk are carried out in this order.

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

The present invention will be described in more detail below with reference to examples and comparative examples. Note that the present invention is not limited to these examples.

Example 1
1. Preparation of milk concentrate (second milk concentrate) First, using a cream separator (Separator F-3, manufactured by Elecream, volume: 0.37 L), raw milk was centrifuged at 50 ° C. (rotation speed: 7000-8000 rpm, processing flow rate: 315 L / h, processing time: 4.2 seconds, gravitational acceleration: 1500-4400 G) to prepare skim milk, which was then cooled to 5 ° C. (skim milk preparation step). Next, a 2N aqueous hydrochloric acid solution was added to the cooled skim milk to adjust the pH of the skim milk to 5.7, and the skim milk was left at 5-10 ° C. for 2 hours (pH adjustment step). Next, the left-standing skim milk was subjected to ultrafiltration (UF) at a concentration ratio of 3.2 times using a hollow fiber membrane module (Romicon Hollow fiber CTG3" HF25-43 PM-10 manufactured by Koch, molecular weight cutoff: 10,000 Da, membrane area: 2.3 ^m2 ) to produce a first milk concentrate (first milk protein concentrate) (first milk concentrate preparation step). Subsequently, cold water (5°C) in an amount of 0.8 times the mass of the first milk concentrate was added to the first milk concentrate and mixed to prepare a first milk concentrate dilution (water addition step). Then, the above hollow fiber membrane module was used to ultrafilter (UF) the first milk concentrate dilution at a concentration ratio of 1.8 times to produce a second milk concentrate (second milk concentrate preparation step).

Before ultrafiltration of skim milk using the hollow fiber membrane module, the hollow fiber membrane was washed with an alkaline aqueous solution containing 200 ppm chlorine. After cooling the hollow fiber membrane by circulating cold water (3-5°C) through the hollow fiber membrane module, the cooling water was discharged from the hollow fiber membrane module. The above-mentioned left-standing skim milk (5-10°C) was then placed in a 20 L jacketed tank. When ultrafiltration of skim milk using the hollow fiber membrane module, the hollow fiber membrane module was connected to the tank with piping or the like, and the tank was indirectly cooled, and a cooling pipe was installed in the middle of the piping to indirectly cool the piping. The concentration ratio for ultrafiltration of skim milk was determined from the amount of skim milk charged (treatment amount), the processing flow rate of the permeate (permeation flow rate), the total solids concentration of the retentate (concentrate), and the protein concentration.

After dividing the second milk concentrate into five, a 2N aqueous solution of sodium hydroxide/potassium hydroxide containing sodium hydroxide and potassium hydroxide at a molar ratio of 3:7 was added so that the sodium (ion)/potassium (ion) ratio of each second milk concentrate was equivalent to that in cow's milk (approximately 4/15), and the pH of each second milk concentrate was adjusted to 6.40, 6.45, 6.50, 6.60, or 6.75 in a constant temperature environment of 20°C, thereby preparing milk concentrates with readjusted pH (pH-readjusted milk concentrates) (pH readjustment process).

2. Physical Properties, etc. Confirmation Test (1) Thermal Stability Confirmation Test First, 4 mL of each pH-readjusted milk concentrate was weighed into a 14 mL round-bottom vial and sealed. Next, the round-bottom vial was immersed in an oil bath at 130° C., and while shaking the round-bottom vial, the time until coagulation occurred in each pH-readjusted milk concentrate was measured while visually checking each pH-readjusted milk concentrate, and this measured time was taken as the "thermal coagulation time". Finally, 2 hours after the pH readjustment, the pH of each pH-readjusted milk concentrate at 10° C. was measured, and the pH was taken as the pH of each pH-readjusted milk concentrate.

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

(2) Sensory test (2-1)
The pH-readjusted milk concentrate was used as the raw milk to prepare fermented milk, which was then subjected to a sensory test. The method for preparing the fermented milk will be described below, followed by a detailed description of the sensory test.

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

Next, each heat-sterilized, pH-readjusted milk concentrate was placed in a tray and the temperature was adjusted to 43°C. Then, 2% by mass of lactic acid bacteria starter (a mixed starter of Lactobacillus bulgaricus and Lactobacillus thermophilus isolated from Meiji Bulgaria Yogurt LB81) was added to each pH-readjusted milk concentrate, and the mixture was stirred and held for 10 minutes.

Next, 70 g of each of the pH-readjusted milk concentrates to which the lactic acid bacteria starter had been added was filled into a cup of approximately 100 mL volume. Meanwhile, the remaining pH-readjusted milk concentrates were left in the tray. The cups and trays were then placed in an incubator at 43°C to ferment each pH-readjusted milk concentrate. Then, when the pH of each pH-readjusted milk concentrate reached 4.6, the fermented milk in the cups was placed in a refrigerator (3-5°C) and kept overnight (approximately 12 hours) to produce hard-type fermented milk. Meanwhile, when the pH of each pH-readjusted milk concentrate reached 4.6, the fermented milk in the tray was cooled in a cold water bath (3-5°C) while being stirred to produce soft-type fermented milk.

(2-2)
A panel of five experts tasted the hard-type fermented milk and the soft-type fermented milk in a cooled (5°C) state and evaluated the sweetness, saltiness, sourness, bitterness, milky flavor, smoothness, and the strength (degree) of unpleasant odor on a five-point scale. At this time, the majority of the expert panelists evaluated that "the fermented milk of Example 1 (described above) is less bitter and has a richer milky flavor and smoothness than the fermented milk of Comparative Example 1 (described below)."

(Comparative Example 1)
In the preparation of the milk concentrate, the pH adjustment step was omitted, and the skim milk cooled was subjected to ultrafiltration only once (first time) without adjusting the pH of the skim milk. A pH readjusted milk concentrate was prepared in the same manner as in Example 1. Then, a confirmation test of thermal stability was carried out on the pH readjusted milk concentrate in the same manner as in Example 1. Note that in Comparative Example 1, the pH readjustment step was carried out only for the purpose of comparison with Examples 1 and 2, and does not negate the patentability of the pH readjustment in the present invention.

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

<Considerations on Examples and Comparative Examples>
As is clear from Fig. 1, it was revealed that within the pH range of 6.4 to 6.6, the pH readjusted milk concentrate prepared in Example 1 had superior heat stability compared to the pH readjusted milk concentrate prepared in Comparative Example 1. Note that within the pH range of 6.4 to 6.5, the heat stability of the pH readjusted milk concentrate prepared in Example 1 was at a level sufficient to withstand the production of fermented milk and the like, and within the pH range of 6.5 to around 6.6, the heat stability of the pH readjusted milk concentrate prepared in Example 1 should be evaluated as being at a remarkable level.

Claims (4)

Per 20 mass% of the total solid content, the protein content is within the range of 9.0 mass% or more and 15.5 mass% or less, the ash content is within the range of 0.30 mass% or more and 1.45 mass% or less, the sodium content is within the range of 0.01 mass% or more and 0.09 mass% or less, the potassium content is within the range of 0.04 mass% or more and 0.38 mass% or less, the calcium content is within the range of 0.15 mass% or more and 0.38 mass% or less, the magnesium content is within the range of more than 0.00 mass% and 0.03 mass% or less, the phosphorus content is within the range of 0.08 mass% or more and 0.23 mass% or less, and the chlorine content is within the range of more than 0.00 mass% and 0.30 mass% or less,
A milk protein concentrate having a thermal coagulation time of 3.5 minutes or more at 130°C within a pH range of 6.4 to 6.6. The milk protein concentrate of claim 1, which is in liquid form. A dairy product produced using the milk protein concentrate according to claim 1 or 2 as a raw material. The dairy product according to claim 3, wherein the dairy product is fermented milk.

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