Fermented milk and method for producing the same

Abstract

To produce fermented milk that has a high content of whey protein and a smooth texture without using special raw material or equipment.SOLUTION: A static-fermented milk has a milk protein content of 5.2 mass% or more relative to the static-fermented milk, and contains both of non-heat-denatured whey protein and heat-denatured whey protein.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a settling type fermented milk and a method for producing the fermented milk. More specifically, the present invention relates to a settling type fermented milk that has a smooth texture and does not require special ingredients or equipment, and a method for producing the fermented milk. The present invention also relates to a method for inhibiting an increase in hardness of fermented milk and a method for improving the smoothness of the texture of fermented milk. [Background technology]

[0002] Fermented milk is made from animal milk such as cow's milk, fermented with lactic acid bacteria, yeast, or both. Consumers have become increasingly health-conscious in recent years. Demand for fermented milk is growing as a food product that provides lactic acid bacteria, which are believed to improve the intestinal environment, as well as a convenient source of protein, one of the three major nutrients. Among these, fermented milk products that promote high protein content are on the rise. The milk proteins contained in fermented milk include casein and whey protein. Compared to casein, whey protein is absorbed more quickly by the body and is rich in BCAAs (branched chain amino acids). However, increasing the amount of whey protein in fermented milk poses challenges, such as reduced thermal stability during production and increased product hardness, which compromises the original texture of fermented milk.

[0003] Regarding the thermal stability during sterilization in the production of fermented milk with increased protein content, there is a method of concentrating and / or diluting milk protein after sterilization (Patent Document 1). In this method, the protein concentration during sterilization is not high, and therefore the problem of thermal stability can be solved. Patent Document 2 discloses a method for preparing a high-protein liquid dairy product with a high whey protein content but low viscosity by using a whey protein material containing 30% or more insoluble whey protein. This method prevents an increase in viscosity that would impair the flavor and texture of the product, even when the whey protein content is increased. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent Publication No. 2017-169491 [Patent Document 2] Special Table 2020-507330 Summary of the Invention [Problem to be solved by the invention]

[0005] However, the method of Patent Document 1 discloses a method for preparing fermented milk by concentrating and diluting after sterilization, but does not mention the proportion of whey protein. Furthermore, the method of Patent Document 1 is limited to liquid fermented milk, and further has the problem of requiring the introduction of membrane concentration equipment. The method of Patent Document 2 discloses a whey material that suppresses the increase in viscosity of fermented milk, but has the problem of requiring the purchase of a specific expensive material, or the installation of equipment for independently producing the whey material. The present invention has been made in view of the above circumstances, and aims to obtain a static fermented milk that has a smooth texture, and to produce the fermented milk without using special raw materials or equipment. [Means for solving the problem]

[0006] The present inventors discovered that by making the milk protein content of fermented milk 5.2 mass% or more based on the fermented milk and by having the fermented milk contain both non-heat-denatured and heat-denatured whey protein, the texture of the fermented milk becomes smooth and pleasant to the palate, and thus completed the present invention. The present inventors also discovered that in the production of fermented milk, low-temperature sterilization of a whey material solution separately from sterilization of a fermented milk raw material mix solution, and then mixing the fermented milk raw material mix solution with the whey material solution, can suppress an increase in the hardness of the fermented milk after fermentation and result in a smooth texture and a pleasant mouthfeel, which led to the completion of the present invention. That is, if the raw materials are sterilized separately and then mixed, the number of steps increases, making the production process complicated. Also, the yield decreases. Despite the above-mentioned drawbacks, the inventors came up with the production method of the present invention, found that the increase in hardness of the fermented milk after fermentation is suppressed, and the texture is smooth and pleasant to the palate, and completed the present invention. The present invention employs the following configuration.

[0007] <1> A still-set fermented milk having a milk protein content of 5.2% by mass or more based on the still-set fermented milk standard, and containing non-heat-denatured whey protein and heat-denatured whey protein. <2> The ratio of whey protein to milk protein is 30% by mass or more. <1> The static fermented milk according to claim 1. <3> Hardness is 6gw or more and 30gw or less. <1> or <2> The static fermented milk according to claim 1. <4> a step of sterilizing a raw material mix solution of fermented milk; sterilizing the whey material solution; a step of mixing the sterilized fermented milk raw material mix solution with the sterilized whey material solution; A method for producing fermented milk, comprising: The fermented milk raw material mix solution contains whey protein, The sterilization conditions of the raw material mix solution of fermented milk are conditions under which whey protein is thermally denatured, and The sterilization conditions for the whey material solution are such that the whey protein is not denatured by heat. The method for producing fermented milk. <5> The fermented milk is a static fermented milk. <4> A method for producing fermented milk according to claim 1. <6> a step of sterilizing a raw material mix solution of fermented milk; sterilizing the whey material solution; a step of mixing the sterilized fermented milk raw material mix solution with the sterilized whey material solution; A method for suppressing an increase in hardness of fermented milk, comprising: The fermented milk raw material mix solution contains whey protein, The sterilization conditions of the raw material mix solution of fermented milk are conditions under which whey protein is thermally denatured, and The sterilization conditions for the whey material solution are such that the whey protein is not denatured by heat. A method for suppressing an increase in hardness of fermented milk. <7> a step of sterilizing a raw material mix solution of fermented milk; sterilizing the whey material solution; a step of mixing the sterilized fermented milk raw material mix solution with the sterilized whey material solution; A method for improving the smoothness of the texture of fermented milk, comprising: The fermented milk raw material mix solution contains whey protein, The sterilization conditions of the raw material mix solution of fermented milk are conditions under which whey protein is thermally denatured, and The sterilization conditions for the whey material solution are such that the whey protein is not denatured by heat. A method for improving the smoothness of the texture of fermented milk. [Effects of the Invention]

[0008] According to the present invention, fermented milk having a high protein content and a smooth texture can be obtained. Moreover, since the fermented milk can be produced without using special raw materials or equipment, it is suitable for industrial production. DETAILED DESCRIPTION OF THE INVENTION

[0009] The present invention will be described in detail below.

[0010] (fermented milk) Fermented milk is defined in the "Ministerial Ordinance on Milk, etc." as a product made by fermenting milk or milk containing an equivalent or greater amount of non-fat milk solids with lactic acid bacteria or yeast into a paste or liquid, or a frozen version of these. In this specification, the definition of "fermented milk" as defined in the Ministerial Ordinance on Milk, etc. applies. In this specification, static fermented milk (also called post-fermented fermented milk, plain yogurt, hard yogurt, or set yogurt) refers to fermented milk that is prepared by filling a container for consumption with fermentation ingredients and then fermenting it. That is, it is fermented milk that is prepared by filling a container for consumption with fermentation ingredients, fermenting it, and then selling it commercially without stirring. Static fermented milk prepared by dissolving ingredients so that the protein content is high, or by using fermentation ingredients that have been concentrated in advance using equipment such as a membrane device, is also called concentrated fermented milk (Greek yogurt). In addition to static fermented milk, fermented milk generally includes stirred fermented milk (also called pre-fermented fermented milk or soft yogurt) and liquid fermented milk. Stirred fermented milk is fermented milk obtained by stirring and breaking down the curds obtained by fermenting raw materials, and is available in plain types as well as types containing ingredients such as fruit pulp. Liquid fermented milk is fermented milk that is prepared by finely crushing settling fermented milk or stirred fermented milk using a homogenizer or other device to enhance its liquid properties, mixing it with fruit pulp or sauce as needed, and then filling it into drinking containers for commercial sale. Liquid fermented milk is also called drinkable yogurt and is liquid (for example, with a viscosity of 600 mPa·s or less). The viscosity was measured using a general B-type viscometer manufactured by Toki Sangyo Co., Ltd. or similar, by dispensing 100 ml of sample into a measuring container, inserting the measuring probe (rotor M2 or M3), and recording the measured value (mPa·s) 30 seconds after the start of rotation. In this case, the viscosity measurement was performed at 10°C.

[0011] (Milk raw materials, etc.) The fermented milk of the present invention can use raw materials contained in ordinary fermented milk as long as they contain non-heat-denatured whey protein and heat-denatured whey protein. For the non-heat-denatured whey protein and heat-denatured whey protein, different milk raw materials, milk raw material powders, or whey ingredient powders can be used. For example, to add non-heat-denatured whey protein and heat-denatured whey protein, milk raw materials such as raw milk (raw milk), whole milk, and skim milk can be used; milk raw material powders such as milk protein concentrate (MPC), isolated milk protein (MPI), concentrated milk protein (MCC), micellar casein concentrate (MCI), skim milk powder, and whole milk powder can be used; or whey ingredient powders such as whey protein concentrate (WPC) and isolated whey protein (WPI). Similarly, whey obtained during the production of dairy products such as cheese whey, and dairy products such as condensed milk, cream, butter, and cheese can also be used. In the fermented milk of the present invention, in order to add whey protein that has not been heat-denatured, it is preferable to use a whey material powder, and it is more preferable to use a whey protein concentrate or isolated whey protein. The fermented milk of the present invention preferably contains not only non-heat-denatured whey protein but also casein protein. The inclusion of casein protein promotes tissue formation in the fermented milk and allows it to have an appropriate hardness. It is more preferable that the casein protein is sterilized at a temperature at which whey protein denatures. When casein protein is sterilized, kappa-casein, a part of the casein protein, is liberated. As a result, fermented milk containing casein protein is given hardness. The coexistence of casein protein and whey protein during sterilization promotes the liberation of kappa-casein. Materials that can be added as raw materials containing casein protein include raw milk (raw milk), whole milk, skim milk, skim milk powder, whole milk powder, MPC, MPI, MCC, and MCI. These raw materials containing casein protein also contain whey protein, and these whey proteins are sterilized together with the casein protein, and the prepared fermented milk also contains heat-denatured whey protein. In other words, it is preferable that the casein protein and the heat-denatured whey protein in the fermented milk are derived from the same raw material.

[0012] In this specification, "milk protein" refers to a protein derived from milk. "Milk protein" consists of two types of protein: casein protein and whey protein. Casein protein is a milk protein that accounts for approximately 80% of the milk proteins contained in cow's milk. As used herein, the term "whey protein" refers to proteins other than casein contained in "milk proteins." Representative whey protein components include α-lactalbumin, β-lactoglobulin, immunoglobulins, and lactoferrin. As used herein, the term "heat-denatured whey protein" refers to whey protein that has been denatured by being heat-sterilized at a temperature equal to or higher than the temperature at which whey protein denatures. As used herein, "non-heat-denatured whey protein" refers to whey protein that has not been heat-sterilized at a temperature equal to or higher than the temperature at which whey protein denatures and has not been denatured. In this specification, the term "dairy raw material" refers to liquid animal milk such as raw milk (raw milk), whole milk, and skim milk. In this specification, the term "dairy raw material powder" refers to a powder obtained by processing livestock milk or a dairy raw material. As used herein, "whey material powder" refers to a milk raw material powder that has been treated to remove casein protein and increase the proportion of whey protein in the milk protein. Specifically, it refers to a powder in which 99% by mass or more of the milk protein is whey protein. In contrast, "whey material" includes not only whey material powder, but also solutions rich in whey protein obtained in the process of producing dairy products such as cheese whey, and whey powder obtained by powdering such solutions. In this specification, "casein material powder" refers to a powder of raw milk material that has been treated to remove whey protein and increase the proportion of casein protein in the milk protein. Specifically, it refers to a powder in which 90% by mass or more of the milk protein is casein protein. The contents of whey protein and casein protein in the fermented milk of the present invention can each be measured using liquid chromatography.

[0013] (Milk protein content) The fermented milk of the present invention has a milk protein content of 5.2% by mass or more based on the fermented milk. If the milk protein content is less than 5.2% by mass, a coagulation will not form and the hardness will be insufficient. The milk protein content may be 5.2% by mass or more, 5.5% by mass or more, 6.0% by mass or more, 6.5% by mass or more, 7.0% by mass or more, 7.5% by mass or more, 8.0% by mass or more, 8.5% by mass or more, 9.0% by mass or more, 9.5% by mass or more, 10.0% by mass or more, or 11.0% by mass or more based on the fermented milk, with the upper limit being 14.0% by mass or less, 13.5% by mass or less, 13.0% by mass or less, 12.5% ​​by mass or less, or 12.0% by mass or less. Specific ranges include 5.2% by mass or more and 14.0% by mass or less, 5.5% by mass or more and 13.5% by mass or less, and 6.0% by mass or more and 13.0% by mass or less. The milk protein content in the fermented milk of the present invention can be measured by the Kjeldahl method. The fermented milk of the present invention may contain proteins other than milk proteins, such as soybean proteins, but preferably does not contain them.

[0014] (Percentage of whey protein in milk protein) The proportion of whey protein in the milk protein contained in the fermented milk of the present invention (including both denatured and undenatured whey protein) is preferably 30% by mass or more, more preferably 30% by mass to 80% by mass, and even more preferably 40% by mass to 70% by mass. Whey protein has the advantage of being more absorbable than casein and containing more BCAAs. However, a high proportion of whey protein often results in a poor mouthfeel. The fermented milk of the present invention can achieve a smooth texture even when the proportion of whey protein is high. When the amount of heat-denatured whey protein is increased, the hardness increases significantly due to the whey protein denatured by sterilization, and the curd increases. This curd forms curd grains in the fermented milk, worsening the texture of the fermented milk (Comparative Examples 1 and 2 described below). By replacing a portion of the heat-denatured whey protein with non-heat-denatured whey protein, the fermented milk of the present invention can achieve a smooth texture even when the proportion of whey protein is high. On the other hand, when all of the heat-denatured whey protein is replaced with non-heat-denatured whey protein, the hardness is insufficient (Comparative Example 3 described below).

[0015] The fermented milk of the present invention contains whey protein that has not been heat-denatured. The presence or absence of whey protein that has not been heat-denatured is evaluated by the following procedure. The fermented milk is centrifuged at 25°C and 1000 g for 10 minutes. The resulting supernatant is used as a sample containing potentially undenatured whey. The presence of β-lactoglobulin and α-lactalbumin in the sample is assessed by liquid chromatography according to J. Chromatography A 2001, 928, 63-76. Identification and quantification of major bovine milk proteins by liquid chromatography. (Bordin et al.)

[0016] The fermented milk of the present invention contains heat-denatured whey protein. The presence or absence of heat-denatured whey protein can be evaluated using known techniques. For example, the mass of non-heat-denatured whey protein measured by liquid chromatography can be subtracted from the total amount of whey protein.

[0017] (Other ingredients) The fermented milk of the present invention may contain foods, food ingredients, or food additives such as sugar, sugars, sweeteners, flavorings, fruit juice, fruit pulp, vitamins, minerals, vegetable oils and fats, emulsifiers, pectin, soybean polysaccharides, agar, gelatin, stabilizers (such as carboxymethylcellulose), starch, and dextrin.

[0018] Examples of starters to be added to and mixed (inoculated) with the raw materials for fermented milk include one or more species selected from lactobacilli such as Lactobacillus bulgaricus and Lactobacillus lactis, lactobacillus such as Streptococcus thermophilus, and other lactic acid bacteria and yeasts commonly used in the production of fermented milk. The amount of starter to be added can be appropriately determined according to the amount used in known methods for producing fermented milk. The method for inoculating the starter is not particularly limited, and any method commonly used in the production of fermented milk can be used appropriately. Fermentation conditions can be set appropriately taking into consideration the type of fermented milk, the desired flavor, the type of starter used, etc. For example, a method can be used in which the temperature inside the fermentation chamber (fermentation temperature) is maintained in the range of 30°C to 50°C, and the fermentation is carried out while the milk is left standing in the fermentation chamber. Lactic acid bacteria are generally active under such temperature conditions, allowing fermentation to proceed effectively. The fermentation temperature is usually around 30°C to 50°C, preferably in the range of 35°C to 45°C, and more preferably in the range of 37°C to 43°C. The fermentation time can be appropriately set and adjusted based on the time until the lactic acid acidity of the fermented milk reaches a predetermined ratio.

[0019] (hardness) The fermented milk of the present invention is characterized by its suppressed increase in hardness and smooth texture. The fermented milk of the present invention preferably has a hardness of 6 gw to 30 gw, more preferably 10 gw to 30 gw, even more preferably 12 gw to 30 gw, and most preferably 15 gw to 30 gw. In the fermented milk of the present invention, hardness is evaluated by the following method. The fermented milk is adjusted to a temperature of 10°C, and the load measured when a 16 mm diameter cylinder is penetrated to a depth of 10 mm from the top surface of the fermented milk at a speed of 0.5 mm / second is taken as the hardness. Evaluation is carried out on the 7th day after production. In this specification, "suppressing an increase in hardness" in relation to fermented milk or "suppressing an increase in hardness" of fermented milk means preventing the hardness of the fermented milk from exceeding 30 gw.

[0020] (Smoothness of texture) The "smooth" texture of fermented milk means that the fermented milk has a fine structure and does not have a powdery or granular texture when eaten. Whether the fermented milk has a smooth texture can be evaluated by sensory evaluation by panelists. In this specification, "improving the smoothness" of fermented milk means preventing the generation of powdery or granular matter and finely granulating the texture of the fermented milk.

[0021] As described below, the fermented milk of the present invention is preferably produced by separately sterilizing raw materials and then mixing them. One raw material mix contains casein protein and whey protein and is heat-sterilized at a temperature at which the whey protein is heat-denatured. The other raw material mix also contains whey protein and is heat-sterilized at a temperature at which the whey protein is not heat-denatured. The fermented milk produced by later mixing these raw material mixes will contain both heat-denatured and non-heat-denatured whey protein.

[0022] (Production method of fermented milk) The method for producing fermented milk of the present invention includes a step of sterilizing a fermented milk raw material mix solution, a step of sterilizing a whey material solution, and a step of mixing the sterilized fermented milk raw material mix solution with the sterilized whey material solution, wherein the fermented milk raw material mix solution contains casein protein and whey protein, the fermented milk raw material mix solution is sterilized under conditions that cause heat denaturation of the whey protein, and the whey material solution is sterilized under conditions that do not cause heat denaturation of the whey protein.

[0023] (Sterilization process of fermented milk raw material mix solution) (Fermented milk raw material mix solution) As used herein, the term "fermented milk raw material mix solution" refers to a liquid containing milk components such as milk raw materials or milk raw material powder. As long as the fermented milk raw material mix solution contains whey protein, it can contain whole milk, skim milk, etc., as well as processed products thereof (e.g., whole milk powder, whole fat concentrated milk, skim milk powder, desalted skim milk powder, skim concentrated milk, condensed milk, cream, butter, cheese, etc.) and solutions thereof. The fermented milk raw material mix solution preferably contains casein protein in addition to whey protein. In the method for producing fermented milk of the present invention, the raw material mix solution of the fermented milk preferably contains skim milk powder. In the fermented milk of the present invention, a whey material may be added to the raw material mix of the fermented milk within a range that does not impair the effects of the present invention, but it is preferable not to add it. Of the proteins contained in the raw material mixed solution of fermented milk, the whey protein concentration is preferably 50% by mass or less, more preferably 40% by mass or less, even more preferably 30% by mass or less, and most preferably 25% by mass or less. In addition to milk components, the fermented milk raw material mixed solution may contain foods or food ingredients and food additives such as sugar, sugars, sweeteners, flavorings, fruit juice, fruit pulp, vitamins, minerals, vegetable oils and fats, emulsifiers, etc. Furthermore, the fermented milk raw material mixed solution may contain stabilizers such as pectin, soybean polysaccharides, agar, gelatin, and carboxymethyl cellulose, starch, dextrin, etc., as needed.

[0024] (Sterilization of fermented milk raw material mix solution) In the sterilization step of producing ordinary fermented milk, the milk protein concentration of the raw materials is the milk protein concentration derived from the raw material mixture, for example, about 3.0% to 4.0% by mass. In the present invention, the milk protein concentration of the fermented milk raw materials during sterilization is, for example, 3.0 to 9.23% by mass, preferably 4.43 to 9.23% by mass, and more preferably 7.38 to 9.23% by mass. By performing sterilization within this milk protein concentration range, problems related to thermal stability, such as the fermented milk raw materials burning on equipment such as plates during the sterilization step, can be avoided, and an appropriate hardness can be imparted to the produced fermented milk.

[0025] (sterilization conditions) In the method for producing fermented milk of the present invention, a raw material mix solution of fermented milk is sterilized under conditions that thermally denature whey protein. Because whey protein denatures at approximately 80°C, the sterilization temperature is preferably 78°C or higher, more preferably 80°C or higher. The sterilization time is not limited to the following, but can be 1 second to 10 minutes. Those skilled in the art can determine an appropriate sterilization time depending on the sterilization temperature. Specific sterilization conditions are not limited to the following, but include, for example, 90°C to 95°C for 15 seconds to 5 minutes in the HTST method, or 130°C or higher for approximately 2 seconds (e.g., 2.0 to 2.2 seconds) in the UHT method, or any equivalent conditions. The upper limit of the sterilization temperature can be 150°C, 145°C, or 140°C.

[0026] (Whey material solution sterilization process) (Whey material solution) As used herein, the term "whey material solution" refers to a solution in which a whey-rich raw material is dissolved in a solvent. In the fermented milk of the present invention, the whey material solution can contain whey powder, whey concentrated powder (e.g., whey protein concentrate or isolated whey protein), or a solution thereof. The whey protein concentration of the protein contained in the whey material solution is preferably 60% by mass or more, more preferably 70% by mass or more, even more preferably 80% by mass or more, even more preferably 90% by mass or more, even more preferably 95% by mass or more, and even more preferably 99% by mass or more. In addition to milk components, the whey material solution can contain food or food ingredients and food additives such as sugar, saccharides, sweeteners, flavorings, fruit juice, fruit pulp, vitamins, minerals, vegetable oils and fats, emulsifiers, etc. Furthermore, the whey material solution can contain stabilizers such as pectin, soybean polysaccharides, agar, gelatin, and carboxymethyl cellulose, starch, dextrin, etc. as needed.

[0027] (Sterilization of whey material solution) In the method for producing fermented milk of the present invention, the protein concentration of the whey material solution at the time of sterilization is, for example, 2.67% to 20.00% by mass, preferably 8.51% to 17.02% by mass, and more preferably 9.60% to 17.02% by mass.

[0028] (sterilization conditions) The sterilization temperature of the whey material solution is preferably 75°C or lower. The sterilization temperature of the whey material solution is not limited, as long as it is under conditions equivalent to these, such as the LTLT method (low temperature hold sterilization) at 63°C to 65°C for 30 minutes, the LTLT method (continuous low temperature sterilization) at 65°C to 68°C for 30 minutes or more, or the HTST method at 72°C or higher for 15 seconds or more. The sterilization device used may be, for example, a plate-type heat exchanger, a tube-type sterilizer, a thermocylinder, a rotatherm, a kettle emulsification vessel, a Stephan emulsification vessel, a Joule heating device, a batch sterilization using a tank, or a combination thereof, and is not limited as long as it can be used to produce fermented milk. By performing sterilization within this protein concentration and sterilization temperature range, thermal denaturation of the whey protein in the whey material solution during production is suppressed, and problems due to thermal stability, such as burning on equipment such as plates during the sterilization process, can be avoided. Furthermore, the weight ratio of whey protein to milk protein can be increased to 30% or more without changing the hardness of the fermented milk after production, without the need for special materials or equipment.

[0029] (Mixing process after sterilization) The mixing of the sterilized fermented milk raw material mix solution and whey material solution, and the subsequent mixing of the starter, may be carried out by continuous dosing in a pipe, by adding to a tank and stirring and dissolving, or by a combination of these.

[0030] The method for producing fermented milk of the present invention can include, in addition to a step of sterilizing a fermented milk raw material mix solution, a step of sterilizing a whey material solution, and a step of mixing the sterilized fermented milk raw material mix solution with the sterilized whey material solution, a step of mixing the fermented milk raw material mix solution, a heating and homogenizing step, a cooling step, a step of mixing the whey material solution, a heating and homogenizing step, a step of adding a starter to and mixing the mixture of the fermented milk raw material mix solution and the whey material solution, a filling step, a fermentation step, and a cooling step. Hereinafter, one embodiment of the method for producing fermented milk of the present invention will be described, but the present invention should not be construed as being limited to the following embodiment. First, dairy products such as raw milk, skim milk powder, and nonfat milk are mixed and dissolved. If necessary, additional ingredients such as pre-dissolved agar, swollen gelatin, sweeteners, and flavorings are mixed in. This mixture is heated to 50-75°C, homogenized in a homogenizer, and then sterilized. The heating and sterilization equipment can be a plate heat exchanger, a tube sterilizer, a thermocylinder, a Joule heating device, a batch sterilization method using a tank, or a combination of these, but is not limited to these. Any equipment suitable for the production of fermented milk can be used. The sterilization temperature is not limited as long as it is within the conditions used in fermented milk production, such as HTST at 90-95°C or UHT at 130°C or higher. After sterilization, the mixture is cooled to 35-55°C using a plate cooler or similar device before being transferred to a mixing tank. Next, whey powder and other ingredients are mixed and dissolved. Pre-dissolved auxiliary ingredients such as sweeteners and flavorings are also mixed in, if necessary. This mixture is heated to 50-65°C, homogenized using a homogenizer if necessary, and then sterilized. The equipment used for heating and sterilization can be, for example, a plate heat exchanger, a tube sterilizer, direct steam injection, direct steam infusion, a thermocylinder, a rotatherm, a kettle emulsifier, a Stephan emulsifier, a Joule heating device, a batch sterilization using a tank, or a combination of these. There is no limitation as long as it is suitable for fermented milk production. After sterilization, the mixture is cooled to 35-55°C using a plate cooler or similar device before being transferred to a mixing tank. Lactic acid bacteria and / or yeast (starter) are added and mixed with the fermented milk ingredients and whey material mixed in the tank. The mixture is then filled into containers (usually paper or plastic cup-shaped containers with paper or plastic top lids) and packaged in small batches as needed, after which fermentation begins. Fermentation conditions vary depending on the starter, but any temperature, time, final acidity, and final pH that are generally used in the production of fermented milk are acceptable. After fermentation, the mixture is cooled to a temperature of 10°C or below.

[0031] The fermented milk produced by the production method of the present invention is preferably settling type fermented milk, but may be other types of fermented milk such as stirred type fermented milk or liquid type fermented milk. When the fermented milk produced by the production method of the present invention is other types of fermented milk such as stirred type fermented milk or liquid type fermented milk, the production method of the present invention may include steps necessary for producing these types of fermented milk. Examples of necessary steps include a crushing step of crushing curds by stirring after the fermentation step, a step of adding solids or other ingredients such as fruit pulp or fruit preserve, and a step of stirring the solids or other ingredients and the fermented milk to homogenize them. [Example]

[0032] The present invention will be described in more detail below with reference to examples, but is not limited thereto. Unless otherwise specified, % indicates % by mass. Furthermore, "protein concentration" and "protein content" indicate the concentration and content of milk protein, respectively. Of the milk proteins in skim milk powder, approximately 20% by mass is whey protein, and approximately 80% by mass is casein protein. Of the proteins in WPC and WPI, 99% by mass or more is whey protein. Hardness was measured using the above-mentioned measurement method.

[0033] Example 1 1500 g of fermented milk raw material obtained by dissolving skim milk powder (Megmilk Snow Brand Co., Ltd.) to a protein concentration of 7.38% was placed in a stainless steel can and heated in a boiling water bath at 90°C for 5 minutes to obtain a fermented milk raw material mix solution, which was then cooled to 45°C in ice water. Next, 1500 g of a whey material solution obtained by dissolving WPI (manufactured by Fonterra, whey protein concentration 85.1%) to a protein concentration of 8.51% was placed in a stainless steel can and heated in a 65°C water bath at 63°C for 30 minutes to obtain a whey material solution, which was then cooled to 45°C in ice water. After cooling, the fermented milk raw material mix solution and whey material solution were mixed, and 0.09% DVS lactic acid bacteria starter, which had been dissolved in 0.85% saline solution to a concentration of 100 U / 1000 kg, was added and mixed. 70 g of the mixture was filled into plastic cup-shaped containers, and aluminum lids were sealed with an iron. Fermentation was then carried out in a 41°C incubator, and when the pH reached 4.5, the mixture was transferred to a 5°C incubator to terminate fermentation. The following day, the mixture was transferred to a 10°C incubator to obtain Example Product 1.

[0034] (Comparative Example 1) 1500 g of a fermented milk raw material obtained by dissolving skim milk powder (Megmilk Snow Brand) to a protein concentration of 7.38% was placed in a stainless steel can to obtain a fermented milk raw material mix solution. Next, WPI (Fonterra, whey protein concentration 85.1%) was dissolved to a protein concentration of 8.51%, and 1500 g of the resulting whey material solution was placed in a stainless steel can to obtain a whey material solution. The fermented milk raw material mix solution and whey material solution were mixed and heated in a boiling water bath at 90°C for 5 minutes. The mixture was then cooled to 45°C in ice water. After cooling, a 0.09% DVS lactic acid bacteria starter, which had been dissolved in 0.85% saline to a concentration of 100 U / 1000 kg, was added and mixed. The mixture was filled into plastic cup-shaped containers (70 g each), and the aluminum lids were sealed with an iron. Fermentation was then carried out in a 41°C incubator. When the pH reached 4.5, the mixture was transferred to a 5°C incubator to terminate the fermentation. The following day, the mixture was transferred to a 10°C incubator to obtain Comparative Example Product 1.

[0035] (Comparative Example 2) Comparative Example Product 2 was obtained in the same manner as Example Product 1, except that 1500 g of whey material solution obtained by dissolving WPI (manufactured by Fonterra, whey protein concentration 85.1%) to a protein concentration of 8.51% was placed in a stainless steel can and heated in a boiling water bath at 90°C for 5 minutes.

[0036] (Comparative Example 3) Comparative product 3 was obtained in the same manner as comparative product 1, except that the fermented milk raw material mix solution and the whey material solution were mixed and heated in a 65°C water bath at 63°C for 30 minutes.

[0037] (Test Example 1: Mix properties after sterilization) The properties of the fermented milk raw material mix solution, whey material solution, or the mixed mix of the fermented milk raw material mix solution and whey material solution after the sterilization step were visually checked and evaluated as either "○: uniform" or "×: aggregated." Burning on the sterilizer was also rated as "×."

[0038] (Test Example 2: Smoothness of fermented milk) Seven days after production, the products were evaluated using a sensory evaluation based on an absolute rating scale of 7 points. The evaluation items were "3 points: very smooth, 2 points: somewhat smooth, 1 point: slightly smooth, 0 point: neither, -1 point: slightly rough, -2 points: somewhat rough, -3 points: very rough," and the evaluation was carried out by a trained expert panel of 10 or more people. Products with an average rating of 0.5 points or higher were considered smooth.

[0039] (Test Example 3: Presence or absence of heat-denatured whey protein) The fermented milk was centrifuged at 25°C and 1000 g for 10 minutes. The resulting supernatant contained non-heat-denatured whey. The presence of β-lactoglobulin and α-lactalbumin in the sample was assessed by liquid chromatography according to Bordin et al., J. Chromatography A 2001, 928, 63-76. Identification and quantification of major bovine milk proteins by liquid chromatography.

[0040] The evaluation results of Example Product 1 and Comparative Examples 1 to 3 are shown in Table 1. In Example Product 1, the milk protein concentration of the fermented milk was 7.95%, of which whey protein accounted for 53.56%. Example Product 1 contained both non-heat-denatured and heat-denatured whey protein, as well as casein protein. Although Example Product 1 had a high protein content and a high whey protein content, the properties of the mix after sterilization were uniform for both the fermented milk raw material mix solution and the whey material solution. The hardness of the fermented milk was 25 gw, and it was evaluated as smooth. Comparative Examples 1 to 3 had the same fermented milk components as Example 1. Comparative Example 1, which was made by mixing a fermented milk raw material mix solution with a whey material solution and then sterilizing it at 90°C, had a fermented milk hardness of 75gW, which was too hard and impaired the texture. The smoothness score was 0.36 points, less than 0.5 points. Comparative Example 1 contains heat-denatured whey protein and casein protein, but does not contain non-heat-denatured whey protein. Comparative Example 2, in which a whey material solution was sterilized at 90°C and then mixed with a sterilized fermented milk raw material mix solution, had a fermented milk hardness of 90gw, which was hard enough to impair the texture. The smoothness score was 0, less than 0.5. Comparative Example 2 contains heat-denatured whey protein and casein protein, but does not contain non-heat-denatured whey protein. In Comparative Example 3, which was prepared by mixing a fermented milk raw material mix solution and a whey material solution and then pasteurizing both at low temperature at 63°C, the hardness of the fermented milk was 5 gw and no coagulation was formed. Comparative Example 3 contains non-heat-denatured whey protein and casein protein, but does not contain heat-denatured whey protein. Example product 1 was evaluated as having a preferable hardness and being smooth compared to comparative examples 1 to 3. Therefore, by sterilizing the raw material mix solution of fermented milk at a relatively high temperature as usual and separately sterilizing the whey material solution at a low temperature, a static fermented milk with a high milk protein concentration, especially a high whey protein concentration, a desirable hardness, and a smooth texture was obtained.

[0041] [Table 1]

[0042] Example 2 2500 g of fermented milk raw material obtained by dissolving skim milk powder (Megmilk Snow Brand Co., Ltd.) to a protein concentration of 4.43% was placed in a stainless steel can and heated in a boiling water bath at 90°C for 5 minutes to obtain a fermented milk raw material mix solution, which was then cooled to 45°C in ice water. Next, 500 g of a whey material solution obtained by dissolving WPC (manufactured by Fonterra, whey protein concentration 80.0%) to a protein concentration of 9.6% was placed in a stainless steel can and heated in a 65°C water bath at 63°C for 30 minutes to obtain a whey material solution, which was then cooled to 45°C in ice water. After cooling, the fermented milk raw material mix solution and whey material solution were mixed, and 0.09% DVS lactic acid bacteria starter, which had been dissolved in 0.85% saline solution to a concentration of 100 U / 1000 kg, was added and mixed. 70 g of the mixture was filled into plastic cup-shaped containers, and aluminum lids were sealed with an iron. Fermentation was then carried out in a 41°C incubator, and when the pH reached 4.5, the mixture was transferred to a 5°C incubator to terminate fermentation. The following day, the mixture was transferred to a 10°C incubator to obtain Example Product 2.

[0043] Example 3 Skim milk powder (Megmilk Snow Brand) was dissolved to a protein concentration of 3.10%, and the solution was heated to 150 kg / cm 2 2500 g of the fermented milk raw material obtained by homogenization at a homogenizing pressure of 1000 kJ / min was placed in a stainless steel can and heated in a boiling water bath at 90°C for 5 minutes to obtain a fermented milk raw material mixed solution. Thereafter, this fermented milk raw material mixed solution was cooled to 45°C in ice water. Next, 500 g of a whey material solution obtained by dissolving WPI (manufactured by Fonterra, whey protein concentration 85.1%) to a protein concentration of 17.02% was placed in a stainless steel can and heated in a 65°C water bath at 63°C for 30 minutes to obtain a whey material solution, which was then cooled to 45°C in ice water. After cooling, the fermented milk raw material mix solution and whey material solution were mixed, and 0.09% DVS lactic acid bacteria starter, which had been dissolved in 0.85% saline solution to a concentration of 100 U / 1000 kg, was added and mixed. 70 g of the mixture was filled into plastic cup-shaped containers, and aluminum lids were sealed with an iron. Fermentation was then carried out in a 41°C incubator, and when the pH reached 4.5, the mixture was transferred to a 5°C incubator to terminate fermentation. The following day, the mixture was transferred to a 10°C incubator to obtain Example Product 3.

[0044] Example 4 1500 g of fermented milk raw material obtained by dissolving skim milk powder (Megmilk Snow Brand Co., Ltd.) to a protein concentration of 7.38% was placed in a stainless steel can and heated in a boiling water bath at 90°C for 5 minutes to obtain a fermented milk raw material mix solution, which was then cooled to 45°C in ice water. Next, WPI (Fonterra, whey protein concentration 85.1%) was dissolved to a protein concentration of 17.02%, and the mixture was stirred at 150 kg / cm 2 1500 g of the whey material obtained by homogenization at a homogenizing pressure of 1000 rpm was placed in a stainless steel can and heated in a 65°C water bath at 63°C for 30 minutes to obtain a whey material solution. This whey material solution was then cooled to 45°C in ice water. After cooling, the fermented milk raw material mix solution and whey material solution were mixed, and 0.09% DVS lactic acid bacteria starter, which had been dissolved in 0.85% saline solution to a concentration of 100 U / 1000 kg, was added and mixed. 70 g of the mixture was filled into plastic cup-shaped containers, and aluminum lids were sealed with an iron. Fermentation was then carried out in a 41°C incubator, and when the pH reached 4.5, the mixture was transferred to a 5°C incubator to terminate fermentation. The following day, the mixture was transferred to a 10°C incubator, yielding Example Product 4.

[0045] Example 5 1200 g of fermented milk raw material obtained by dissolving skim milk powder (Megmilk Snow Brand Co., Ltd.) to a protein concentration of 9.23% was placed in a stainless steel can and heated in a boiling water bath at 90°C for 5 minutes to obtain a fermented milk raw material mix solution, which was then cooled to 45°C in ice water. Next, 1800 g of a whey material solution obtained by dissolving WPI (manufactured by Fonterra, whey protein concentration 85.1%) to a protein concentration of 17.02% was placed in a stainless steel can and heated in a 65°C water bath at 63°C for 30 minutes to obtain a whey material solution, which was then cooled to 45°C in ice water. After cooling, the fermented milk raw material mix solution and whey material solution were mixed, and 0.09% DVS lactic acid bacteria starter, which had been dissolved in 0.85% saline solution to a concentration of 100 U / 1000 kg, was added and mixed. 70 g of the mixture was filled into plastic cup-shaped containers, and aluminum lids were sealed with an iron. Fermentation was then carried out in a 41°C incubator, and when the pH reached 4.5, the mixture was transferred to a 5°C incubator to terminate fermentation. The following day, the mixture was transferred to a 10°C incubator, yielding Example Product 5.

[0046] Comparative Example 4 1100 g of fermented milk raw material obtained by dissolving skim milk powder (Megmilk Snow Brand Co., Ltd.) to a protein concentration of 10.06% was placed in a stainless steel can and heated in a boiling water bath at 90°C for 5 minutes to obtain a fermented milk raw material mix solution, which was then cooled to 45°C in ice water. Next, 1900 g of a whey material solution obtained by dissolving WPI (manufactured by Fonterra, whey protein concentration 85.1%) to a protein concentration of 17.02% was placed in a stainless steel can and heated in a 65°C water bath at 63°C for 30 minutes to obtain a whey material solution, which was then cooled to 45°C in ice water.

[0047] (Comparative Example 5) 2400 g of fermented milk raw material obtained by dissolving skim milk powder (Megmilk Snow Brand Co., Ltd.) to a protein concentration of 4.61% was placed in a stainless steel can and heated in a boiling water bath at 90°C for 5 minutes to obtain a fermented milk raw material mix solution, which was then cooled to 45°C in ice water. Next, 600 g of a whey material solution obtained by dissolving WPI (manufactured by Fonterra, whey protein concentration 85.1%) to a protein concentration of 21.28% was placed in a stainless steel can and heated in a 65°C water bath at 63°C for 30 minutes to obtain a whey material solution, which was then cooled to 45°C in ice water.

[0048] (Comparative Example 6) 2000 g of fermented milk raw material obtained by dissolving skim milk powder (Megmilk Snow Brand Co., Ltd.) to a protein concentration of 0.92% was placed in a stainless steel can and heated in a boiling water bath at 90°C for 5 minutes to obtain a fermented milk raw material mix solution, which was then cooled to 45°C in ice water. Next, 1000 g of a whey material solution obtained by dissolving WPI (manufactured by Fonterra, whey protein concentration 85.1%) to a protein concentration of 8.51% was placed in a stainless steel can and heated in a 65°C water bath at 63°C for 30 minutes to obtain a whey material solution. Thereafter, this fermented milk raw material mix solution was cooled to 45°C in ice water. After cooling, the fermented milk raw material mix solution and whey material solution were mixed, and 0.09% DVS lactic acid bacteria starter, which had been dissolved in 0.85% saline solution to a concentration of 100 U / 1000 kg, was added and mixed. 70 g of the mixture was filled into plastic cup-shaped containers, and aluminum lids were sealed with an iron. Fermentation was then carried out in a 41°C incubator, and when the pH reached 4.5, the mixture was transferred to a 5°C incubator to terminate fermentation. The following day, the mixture was transferred to a 10°C incubator to obtain Comparative Example Product 6.

[0049] The test results for Example Products 2 to 5 and Comparative Examples 4 to 6 are shown in Table 2. In Example Products 2 to 5, the protein concentrations of the fermented milk were 5.29%, 5.42%, 12.20%, and 13.90%, of which the whey protein proportions were 30.25%, 52.34%, 69.75%, and 73.46%, respectively. Although Example Products 2 to 5 had high protein contents and high whey protein proportions, the properties of the mixes after sterilization were uniform for both the fermented milk raw material mix solution and the whey material solution. The hardness of the fermented milk was 22 to 30 gw, and all were evaluated as smooth. In the test of Comparative Example 4, the protein content in the raw material mix solution of fermented milk was 10.06%. After sterilization at 90°C, aggregation was observed in the mix. In the test of Comparative Example 5, the protein concentration of the whey material solution was 21.28%. After sterilization at 63°C, aggregation was observed in the mix. In Comparative Example 6, the protein concentration of the fermented milk was 3.45%, of which the proportion of whey protein was 82.18%. The mix after sterilization was uniform in appearance, but no fermented milk gel was formed. Therefore, the protein content of the fermented milk raw material mix solution was 3.1% to 9.23%, and fermented milk could be produced without any stability problems during the sterilization process. Furthermore, by setting the protein content of the whey material solution to 2.67% or more, the whey protein content of the protein in the fermented milk could be increased to 30% or more without any problems. Furthermore, when the protein content of the whey material solution was set to 17.02% or less, fermented milk could be produced without any stability problems during the sterilization process. However, even if the protein content exceeded 17.02%, it was thought that sterilization of the whey material solution could be carried out without any problems by adjusting the protein content in the whey material solution or adjusting the sterilization conditions.

[0050] [Table 2] [Industrial Applicability]

[0051] According to the present invention, fermented milk having a high whey protein content and a smooth texture can be obtained. Moreover, since the fermented milk can be produced without using special raw materials or equipment, it is suitable for industrial production.

Claims

1. a step of sterilizing a raw material mix solution of fermented milk; sterilizing the whey material solution; A step of mixing the sterilized fermented milk raw material mix solution with the sterilized whey material solution; A method for producing fermented milk, comprising: The fermented milk raw material mix solution contains whey protein, The sterilization conditions of the raw material mix solution of fermented milk are conditions under which whey protein is thermally denatured, and The sterilization conditions for the whey material solution are such that the whey protein is not denatured by heat. The method for producing fermented milk.

2. The method for producing fermented milk according to claim 1, wherein the fermented milk is a static fermented milk.

3. a step of sterilizing a raw material mix solution of fermented milk; sterilizing the whey material solution; a step of mixing the sterilized fermented milk raw material mix solution with the sterilized whey material solution; A method for suppressing an increase in hardness of fermented milk, comprising: The fermented milk raw material mix solution contains whey protein, The sterilization conditions of the raw material mix solution of fermented milk are conditions under which whey protein is thermally denatured, and The sterilization conditions for the whey material solution are such that the whey protein is not denatured by heat. A method for suppressing an increase in hardness of fermented milk.

4. a step of sterilizing a raw material mix solution of fermented milk; sterilizing the whey material solution; a step of mixing the sterilized fermented milk raw material mix solution with the sterilized whey material solution; A method for improving the smoothness of the texture of fermented milk, comprising: The fermented milk raw material mix solution contains whey protein, The sterilization conditions of the raw material mix solution of fermented milk are conditions under which whey protein is thermally denatured, and The sterilization conditions for the whey material solution are such that the whey protein is not denatured by heat. A method for improving the smoothness of the texture of fermented milk.

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