Sterilized fermented milk and method for producing same

Abstract

The invention provides solidified sterilized fermented milk and a manufacturing method thereof. The set-type sterilized fermented milk is characterized by containing 1.5-3.0 mass% of whey protein and 2.0-3.0 mass% of casein, with the whey protein being contained in an amount of 50-125 parts by mass per 100 parts by mass of casein; and the pH (Potential of Hydrogen) is 5.3 to 5.9.

Description

[0001] REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority based on Japanese Patent Application No. 2022-146607 filed on September 14, 2022, the entire disclosure of which is incorporated herein by reference. TECHNICAL FIELD

[0003] The present invention relates to a sterilized fermented milk in a solidified form and a method for producing the same. More specifically, the present invention relates to a sterilized fermented milk in a solidified form that is filled in a container, then fermented (post-fermented), and solidified in the container, and a method for producing the same. BACKGROUND ART

[0004] With the growth of health consciousness, consumers' interest in fermented milk is also increasing. If fermented milk can be used in a wider range of dishes, the opportunity to consume it is expected to increase even more. However, due to its properties such as strong sour taste and weak shape retention, in practice, fermented milk is mainly consumed as it is, or spread on ingredients such as vegetables and meats and eaten by dipping, or used as one of the ingredients and mixed with other ingredients during cooking.

[0005] In order to simply improve the shape retention of fermented milk, it can have a high-concentration composition or be solidified by adding a gelling agent or thickening polysaccharides; however, when heated for cooking, the fermented milk will break or become too hard. When heated to a high temperature, the fermented milk also produces a strong sour taste. On the other hand, increasing the pH to suppress the sour taste will sharply reduce the shape retention; to make up for this, it becomes necessary to apply a high-concentration composition or use a gelling agent or thickening polysaccharides, which will damage the flavor and texture. In order to expand the application of fermented milk in a wider range of dishes, it is necessary to improve its taste and physical properties, for example, by reducing its sour taste while preventing it from disintegrating during cooking.

[0006] No prior art documents have been found that disclose a fermented milk that does not disintegrate when boiled and has a limited sour taste without using a gelling agent or thickening polysaccharides, and a method for producing such a fermented milk.

[0007] PTL 1 and PTL 2 are prior art documents that disclose technologies common to the manufacturing method of the present invention in terms of heat treatment (secondary heat treatment) after post-fermentation. However, PTL 1 is characterized in that, after fermentation, a substance containing β-glucan (Aureobasidium medium) is added as a stabilizer, and then the mixture is heated. Further, after the heat treatment, the mixture is homogenized to make it liquefy. Therefore, PTL 1 is different from the present invention in that it is not a coagulated sterilized fermented milk. PTL 2 is different from the present invention in that it is characterized by incorporating cross-linked modified starch as a component and relates to soft or drinkable yogurt prepared by breaking curd after fermentation.

[0008] Prior art documents

[0009] Patent documents

[0010] Patent Document 1: Japanese Unexamined Patent Application Publication No. 2005-137245

[0011] Patent Document 2: Japanese Unexamined Patent Application Publication No. 2017-63727 Summary of the Invention

[0012] Problems to be Solved by the Invention

[0013] An object of the present invention is to provide a coagulated sterilized fermented milk with reduced sourness and less likely to disintegrate even during heat cooking, and to provide a manufacturing method of the coagulated sterilized fermented milk.

[0014] Solutions to the Problems

[0015] The present inventors conducted extensive research to manufacture a coagulated fermented milk that solves the above problems, and found that by adding lactic acid bacteria to a raw milk mixture containing 1.5 to 3.0% by mass of whey protein and 2.0 to 3.0% by mass of casein in a specific ratio, fermenting the mixture in a container until the pH reaches 5.3 to 5.9, and then subjecting the container to heat treatment such that the heat history is at least 75°C × 15 minutes × normal pressure, a coagulated sterilized fermented milk having desired properties (low sourness, boil-resistant disintegration) can be obtained.

[0016] The present invention has been completed based on the above findings and includes the following embodiments.

[0017] (I) Coagulated sterilized fermented milk

[0018] (I-1) A coagulated sterilized fermented milk, comprising

[0019] 1.5 to 3.0% by mass of whey protein, and

[0020] 2.0 to 3.0% by mass of casein,

[0021] wherein

[0022] the amount of whey protein is 50 to 125 parts by mass relative to 100 parts by mass of casein, and

[0023] the pH of the set-type sterilized fermented milk is 5.3 to 5.9.

[0024] (I-2) The sterilized fermented milk according to (I-1), which contains 9.5 to 11.2% by mass of fat-free milk solids.

[0025] (I-3) The sterilized fermented milk according to (I-1) or (I-2), which has shape retention and / or boiling resistance to disintegration.

[0026] (I-4) The sterilized fermented milk according to any one of (I-1) to (I-3), wherein the maximum load at break in a fracture test using a plunger is 5.0 to 8.0 N.

[0027] (II) Method for producing coagulated sterilized fermented milk

[0028] (II-1) A method for manufacturing a set-type sterilized fermented milk, which includes the following steps:

[0029] (a) Adding lactic acid bacteria to a raw milk mixture to ferment the raw milk mixture in a container until the pH reaches 5.3 to 5.9, wherein the raw milk mixture contains 1.5 to 3.0% by mass of whey protein and 2.0 to 3.0% by mass of casein, and the amount of whey protein is 50 to 125 parts by mass relative to 100 parts by mass of casein; and

[0030] (b) Heating the obtained fermented milk together with the container such that the heat history is at least: 75°C × 15 minutes × atmospheric pressure.

[0031] (II-2) The manufacturing method according to (II-1), wherein the raw milk mixture contains 9.5 to 11.2% by mass of fat-free milk solids.

[0032] (II-3) The manufacturing method according to (II-1) or (II-2), wherein before adding lactic acid bacteria, the raw milk mixture is homogenized and sterilized.

[0033] This manufacturing method can also be described as follows.

[0034] The production method according to (II-1) or (II-2) further includes, before step (a), a step of homogenizing and sterilizing the raw milk mixture, the raw milk mixture containing 1.5 to 3.0% by mass of whey protein and 2.0 to 3.0% by mass of casein, wherein the amount of whey protein is 50 to 125 parts by mass relative to 100 parts by mass of casein.

[0035] (II-4) The production method according to any one of (II-1) to (II-3), wherein the fermentation temperature is 35 to 48 °C.

[0036] Effects of the Invention

[0037] The sterilized fermented milk of the present invention and the sterilized fermented milk obtained by the production method of the present invention have a higher pH of 5.3 to 5.9 compared to a conventional fermented milk with a pH of about 4.6, and thus their sour taste is milder. This makes such sterilized fermented milk easy to consume and allows it to be combined with many ingredients.

[0038] The sterilized fermented milk of the present invention and the sterilized fermented milk obtained by the production method of the present invention also have good shape retention and are not easily disintegrated even when boiled; therefore, they are easy to use in a variety of cooking processes whether heated or not. In addition, when the sterilized fermented milk is boiled, the broth is not easily turbid. Therefore, the loss of nutrients during cooking is limited and the appearance of the dish is not deteriorated.

[0039] Furthermore, the sterilized fermented milk of the present invention and the sterilized fermented milk obtained by the production method of the present invention can be appropriately adjusted to have the same hardness and / or texture as silk tofu or cotton tofu, and thus can be used in place of the tofu used in commonly eaten tofu dishes such as yudofu, shabu-shabu, soup stock, tofu steak, cold tofu, and mapo tofu. This will broaden the cooking uses of fermented milk and increase the opportunity for consumers to consume this healthy food, fermented milk. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 Images of the broths (contained in beakers) of Comparative Examples 24 and 25 and Examples 5 and 6 in which the broth turbidity test was conducted in Experimental Example 2 are shown. From the left, Comparative Example 24 (turbidity: >40 NTU), Comparative Example 25 (turbidity: 33.3 NTU), Example 5 (turbidity: 3.9 NTU), and Example 6 (turbidity: >2.9 NTU). DETAILED DESCRIPTION OF THE INVENTION

[0041] (I) Coagulated sterilized fermented milk

[0042] In the "Ministerial Ordinance Concerning Compositional Standards, etc. for Milk and Milk Products" (Ministry of Health, Labour and Welfare Ordinance, No. 52 of 1951, revised on January 9, 2015, Ministry of Health, Labour and Welfare of Japan) (hereinafter referred to as the "Ministerial Ordinance on Milk and Milk Products"), fermented milk is defined as "a product obtained by fermenting milk or milk products containing not less than an equal amount of non-fat milk solids with lactic acid bacteria or yeast and then forming a paste or liquid, or a frozen product", in which the non-fat milk solids are set at 8.0% or more. These fermented milks are generally classified into the following categories: (a) firm fermented milk: obtained by filling raw milk into a container, fermenting it and solidifying it in the container (referred to as "set fermented milk" or "post-fermented milk"); (b) paste fermented milk: obtained by fermenting in a large tank or the like, breaking the formed curd, mixing it with pulp, sauce, etc. as required, and then filling it into a container (referred to as "soft yogurt" or "pre-fermented milk"); and (c) liquid fermented milk: obtained by finely pulverizing the firm fermented milk or paste fermented milk with a homogenizer or the like to make it liquefy, mixing it with pulp, sauce, etc. as required, and then filling it into a container (referred to as "yogurt drink").

[0043] The fermented milk targeted by the present invention is the set (solid) fermented milk that is post-fermented with lactic acid bacteria among these fermented milks. The fermented milk targeted by the present invention is also prepared by heat treatment for sterilization after fermentation ("sterilized fermented milk"). Specifically, the fermented milk targeted by the present invention is a fermented milk prepared by fermenting according to the regulations of the Ministerial Ordinance on Milk and Milk Products and then heating at 75°C for at least 15 minutes, or by heat sterilization using a method that exhibits an equal or higher sterilization effect.

[0044] The sterilized fermented milk of the present invention contains 1.5 to 3.0% by mass of whey protein and 2.0 to 3.0% by mass of casein based on the sterilized fermented milk taken as 100% by mass, and the amount of whey protein (mass ratio of solid components) is 50 to 125 parts by mass relative to 100 parts by mass of casein.

[0045] The content of whey protein and the content of casein refer to the solid content (converted into solid components) of each protein contained in the sterilized fermented milk taken as 100% by mass (wet mass).

[0046] Whey protein is a mixture of several proteins contained in whey, which is the liquid part of cow's milk from which casein and fat have been removed. The proteins that make up whey protein include β-lactoglobulin, α-lactalbumin, immunoglobulins, bovine serum albumin, lactoferrin, lactoperoxidase, and proteose peptone. Whey protein is considered to account for approximately 20% by mass of the milk protein contained in cow's milk.

[0047] Casein (commonly referred to as "casein") is the milk protein that accounts for approximately 80% of cow's milk and is a complex protein composed of α S1 -casein, α S2 -casein, β-casein, and κ-casein.

[0048] The casein content and whey protein content in sterilized fermented milk (sample) can be measured by the following method.

[0049] [Casein]

[0050] Add 90 ml of water to 10 g of the sample and heat the mixture to approximately 40 to 42 °C. Add 1.5 ml of a 10% by mass aqueous acetic acid solution thereto and stir. After allowing the mixture to stand for 5 minutes, collect the precipitate (casein) through a filter paper. Wash the precipitate (residue) remaining on the filter paper with water acidified with acetic acid (pH 4.6), and subject the residue and the filter paper together to a combustion method or the Kjeldahl method to quantify nitrogen, and then multiply the quantified nitrogen by the nitrogen-protein conversion factor to determine the casein content.

[0051] [Whey protein]

[0052] Quantify the total amount of all proteins contained in the sample according to the combustion method or the Kjeldahl method, and subtract the casein content determined by the above method to determine the whey protein content.

[0053] There is no limitation on the whey protein content (in terms of solid content conversion) in sterilized fermented milk taken as 100% by mass (wet mass), as long as the above requirements are met. However, the whey protein content is preferably 1.5 to 3.0% by mass, more preferably 1.7 to 2.5% by mass. There is no limitation on the casein content (in terms of solid content conversion), as long as the above requirements are met. However, the casein content is preferably 2.3 to 3.0% by mass, more preferably 2.5 to 3.0% by mass. In addition, there is no limitation on the amount of whey protein (mass ratio of solid content) relative to 100 parts by mass of casein, as long as the above requirements are met. However, the amount of whey protein relative to 100 parts by mass of casein is preferably 50 to 120 parts by mass, more preferably 62 to 100 parts by mass.

[0054] The content of fat-free milk solids in the sterilized fermented milk of the present invention is 8% by mass or more based on the standard of the fermented milk. The content of fat-free milk solids is preferably 9 to 12% by mass, more preferably 9.5 to 11.2% by mass.

[0055] The sterilized fermented milk of the present invention may contain, but is not limited to, milk fat in an amount in the range of 0.5 to 4% by mass, preferably 1 to 3.5% by mass, more preferably 1.5 to 3.0% by mass; lactose in an amount in the range of 4.4 to 6.7% by mass, preferably 5.0 to 6.2% by mass, more preferably 5.3 to 5.9% by mass; and sugars (carbohydrates) other than lactose in an amount in the range of 0 to 10% by mass, preferably 2.5 to 7.5% by mass, more preferably 4 to 6% by mass.

[0056] The types of sugars other than lactose include, but are not limited to, monosaccharides (such as glucose, fructose, and galactose); disaccharides (such as sucrose, maltose, lactose, and trehalose); oligosaccharides (such as fructooligosaccharide, soy oligosaccharide, raffinose (beet oligosaccharide), galactooligosaccharide, and isomaltooligosaccharide); polysaccharides (such as EPS (exopolysaccharides) and pectin); and sugar alcohols (such as xylitol, sorbitol, and maltitol).

[0057] The pH of the sterilized fermented milk of the present invention is 5.3 to 5.9, which is higher than the pH of conventional fermented milk (about 4.6). Therefore, the sterilized fermented milk of the present invention has less sour taste than conventional fermented milk. More preferably, the pH of the sterilized fermented milk of the present invention is 5.4 to 5.8.

[0058] The sterilized fermented milk of the present invention is in a solid state and has shape retention. Whether the sterilized fermented milk has shape retention can be determined in the following manner: As described in the following experimental example, the target sterilized fermented milk is directly taken out from a cylindrical (diameter: 7 cm) cup-shaped container (filled capacity: 100 g) and left standing on a flat plate such as a dish at the product temperature (25°C) for 60 minutes. Observe whether the cup shape does not disintegrate under its own weight and whether the shape is maintained. If the shape is maintained without breaking, the sterilized fermented milk can be evaluated as having "shape retention".

[0059] In addition, the meaning of "the shape is maintained without breaking" not only means maintaining the cup shape as it is, but also means that the cup shape slightly sags while maintaining the corners (edges) without flowing and breaking.

[0060] The sterilized fermented milk of the present invention has resistance to boiling and disintegration. By directly taking out the target sterilized fermented milk from a cup-shaped container (filled volume: 100 g), then immersing it in 10 times the volume of hot water (80 °C) for 10 minutes (static immersion), and comparing the shape of the sterilized fermented milk with the shape before immersion (cup shape) to observe whether the shape is broken, it is determined whether the sterilized fermented milk has resistance to boiling and disintegration. As described in the following experimental examples, the sterilized fermented milk whose shape does not break even after immersion can be evaluated as "having resistance to boiling and disintegration". The meaning of "the shape does not break" herein not only means that the cup shape before immersion remains as it is, but also means that the whole cup shape loosens (expands), but the corners (edges) are kept without breaking. More preferably, the residual liquid (soup) is obtained by removing the sterilized fermented milk that has undergone the above-mentioned resistance to boiling and disintegration test, and passing it through a 60# filter; then, the filtrate is transparent, and the turbidity measured with a 200P turbidimeter (HACH) according to the method described in the following experimental examples is less than 5 NUT.

[0061] Although not limited thereto, the sterilized fermented milk of the present invention preferably has a hardness similar to or equivalent to that of silk tofu, a hardness similar to or equivalent to that of cotton tofu, or a hardness between silk tofu and cotton tofu. The hardness can be evaluated by eating the sterilized fermented milk, silk tofu, and cotton tofu of the present invention all adjusted to the same product temperature (e.g., 10 °C) and comparing them.

[0062] Optionally, the maximum load (N) measured in the fracture test using a creep meter (e.g., Rheoner II manufactured by Yamaden Co., Ltd.) can be compared with the maximum loads (N) of silk tofu and cotton tofu for evaluation. Specifically, as described in the following experimental examples, a disk-shaped plunger is lowered from above onto the surface of the sterilized fermented milk (test sample; product temperature: 25 °C) contained in a cup-shaped container to apply a load, and the compression curve is measured to determine the maximum value of the load applied until the test sample breaks (maximum load (N)). When measured under the conditions described in the following experimental examples, the maximum load of the sterilized fermented milk of the present invention is preferably in the range of 5.00 to 8.00 N, more preferably 5.10 to 7.00 N, and even more preferably 5.10 to 6.50 N.

[0063] In addition, although there is no limitation, it is preferable that when the sterilized fermented milk of the present invention is put into the mouth and squeezed with the tongue, the tongue feeling is a smooth texture like silk tofu (equivalent to or similar to silk tofu), a slightly rough texture like cotton tofu (equivalent to or similar to cotton tofu), or a texture between silk tofu and cotton tofu. More preferably, the sterilized fermented milk has a texture between silk tofu and cotton tofu. As described in the following experimental examples, the texture can be evaluated as follows: A panel of experts trained in sensory evaluation compares the texture of the sterilized fermented milk of the present invention (test sample; product temperature: 10°C) with the textures of commercially available ordinary silk tofu and cotton tofu whose product temperatures are adjusted to 10°C as Controls 1 and 2, and determines whether the smoothness and roughness felt by the tongue are the same or different.

[0064] (II) Method for producing coagulated sterilized fermented milk

[0065] The above-mentioned sterilized fermented milk of the present invention can be produced by a method including the following steps (a) and (b):

[0066] (a) A step of adding lactic acid bacteria to a raw milk mixture and fermenting the mixture in a container until the pH reaches 5.3 to 5.9, wherein the raw milk mixture (100% wet mass) contains 1.5 to 3.0% by mass of whey protein and 2.0 to 3.0% by mass of casein in terms of solid components, and the amount of whey protein (solid component mass ratio) is 50 to 125 parts by mass relative to 100 parts by mass of casein (hereinafter referred to as "step (a)" or "fermentation step"); and

[0067] (b) A step of heat-treating the obtained fermented milk in the container so that the heat history is at least 75°C for 15 minutes (hereinafter referred to as "step (b)" or "heating step").

[0068] The above-mentioned production steps of the present invention may include, before step (a): (1) a step of preparing a raw milk mixture (raw milk mixture preparation step); (2) a step of homogenizing the raw milk mixture (homogenization step); and (3) a step of sterilizing the raw milk mixture (pre-sterilization step). These are called "pretreatment steps". In these pretreatment steps, the homogenization step (2) and the pre-sterilization step (3) can be carried out in any order. The raw milk mixture prepared in step (1) can be subjected to the homogenization step (2) and then the pre-sterilization step (3); or it can be subjected to the pre-sterilization step (3) and then the homogenization step (2). The homogenization step (2) and the pre-sterilization step (3) can also be carried out simultaneously.

[0069] The manufacturing steps of the present invention described above may further include a step (4) of filling the raw milk mixture obtained in the pretreatment steps (1) to (3) into a container (filling step). The filling step may be carried out before adding lactic acid bacteria to the raw milk mixture obtained in the pretreatment steps (1) to (3), or may be carried out after adding lactic acid bacteria to the raw milk mixture obtained in the pretreatment steps (1) to (3).

[0070] Although not limited, the manufacturing steps of the present invention preferably include a filling step after the pretreatment steps (1) to (3) and before adding lactic acid bacteria in step (a). In other words, it is preferred to fill the raw milk mixture obtained in the pretreatment steps (1) to (3) into a container, and then carry out step (a), in which lactic acid bacteria are added to the raw milk mixture filled in the container to ferment the mixture in the container.

[0071] The following describes each step.

[0072] [(1) Raw milk mixture preparation step]

[0073] The "raw milk mixture" targeted by the present invention is a composition containing milk components derived from cow's milk, and refers to a composition containing 1.5 to 3.0% by mass of whey protein and 2.0 to 3.0% by mass of casein calculated on a solid component basis, wherein the whey protein is present in an amount of 50 to 125 parts by mass relative to 100 parts by mass of casein.

[0074] The raw milk mixture is prepared by using two or more raw materials selected from the following and adjusting the amounts of whey protein and casein to achieve the above ratio in the raw milk mixture taken as 100%: raw milk squeezed from cows, cow's milk, skim milk, whole milk powder, skim milk powder, whole milk concentrate, skim milk concentrate, sweetened condensed milk, sweetened skim condensed milk, unsweetened condensed milk, unsweetened skim condensed milk, whey, whey powder, desalted whey, desalted whey powder, whey protein concentrate (WPC), whey protein isolate (WPI), α-lactalbumin, β-lactoglobulin, milk protein concentrate (MPC), casein, sodium caseinate, calcium caseinate, cream, fermented cream, compound cream, cream powder, butter, fermented butter, buttermilk, buttermilk powder, butter oil, etc.

[0075] If the amounts of whey protein and casein in the raw milk mixture fall within the above ranges, this is sufficient. Although the amounts are not limited, the amount of whey protein is preferably 1.5 to 3.0% by mass, more preferably 1.7 to 2.5% by mass, and the amount of casein is preferably 2.3 to 3% by mass, more preferably 2.5 to 3.0% by mass. In addition, the amount of whey protein relative to 100 parts by mass of casein (solid component mass ratio) is preferably 50 to 120 parts by mass, more preferably 62 to 100 parts by mass, although it is not limited thereto.

[0076] Furthermore, when using cow's milk as the raw material, if the cow's milk has been subjected to the sterilization treatment specified in the Milk Act and other regulations (wherein it is stated that the cow's milk should be heated and sterilized at 63°C for 30 minutes using a holding method or a method having an equivalent or higher sterilization effect), this is sufficient. The sterilization treatment methods include low-temperature long-time sterilization (LTLT), continuous low-temperature sterilization (LTLT), high-temperature long-time sterilization (HTLT), high-temperature short-time sterilization (HTST), ultra-high temperature instantaneous sterilization (UHT), and ultra-high temperature sterilization method (LL). Among the cow's milk sold in Japan, 90% is treated with UHT.

[0077] The raw milk mixture can be adjusted so that the content of non-fat milk solids is 8% by mass or more based on the standard of fermented milk. The content of non-fat milk solids is preferably 9 to 12% by mass, more preferably 9.5 to 11.2% by mass. Although not limited, the raw milk mixture can be adjusted so that the raw milk mixture contains 0.5 to 4% by mass, preferably 1 to 3.5% by mass, more preferably 1.5 to 3.0% by mass of milk fat, 4.4 to 6.7% by mass, preferably 5.0 to 6.2% by mass, more preferably 5.3 to 5.9% by mass of lactose, and 0 to 10% by mass, preferably 2.5 to 7.5% by mass, more preferably 4 to 6% by mass of carbohydrates other than lactose.

[0078] The raw milk mixture can be prepared using only the above milk components, but it can also be prepared by adding, to the extent that the effects of the present invention are not impaired, for example, lipids, proteins other than whey protein and casein, carbohydrates, minerals (salts), vitamins, flavor components, spices, pigments, and other food additives in addition to the above milk components. Although not strictly limited, it is preferred that the raw milk mixture targeted by the present invention does not contain any components falling under the categories of gelling agents, thickening polysaccharides, or stabilizers (for example, β-glucan-containing substances described in Patent Document 1 and processed starches such as cross-linked processed starches described in Patent Document 2).

[0079] The raw milk mixture of the present invention is a composition containing water and milk components. The proportion of water in the raw milk mixture can be in the range of 11 to 25% by mass, preferably 12 to 20% by mass, more preferably 13 to 16% by mass.

[0080] [(2) Homogenization step]

[0081] The step of homogenizing the raw milk mixture refers to finely pulverizing (miniaturizing) the particles composed of proteins and / or lipids contained in the raw milk mixture. The homogenization method can follow standard methods; examples of the methods used include, but are not limited to, stirring the raw milk mixture while applying shear by using equipment such as a mixer or a pump, passing the raw milk mixture through a narrow gap while pushing the raw milk mixture by applying pressure, or passing the raw milk mixture through a narrow gap while sucking the raw milk mixture by decompression. The methods and equipment for homogenizing raw milk are not limited to these methods, and any known methods and equipment can be used.

[0082] The homogenization step can be carried out so that the average particle size of the raw milk is 0.8 μm or less.

[0083] [(3) Pre-sterilization step]

[0084] In order to sterilize the raw milk mixture until the number of bacteria (excluding spores) contained in the raw milk mixture becomes 10 3 / ml or less, the step of sterilizing the raw milk mixture is implemented.

[0085] Any method and conditions capable of achieving this purpose can be used, such as heat treatment methods for sterilizing cow's milk. Examples of heat treatment methods for sterilizing cow's milk include: ultra-high temperature instant sterilization (UHT sterilization) method, in which heat treatment is carried out at 120 to 150 °C for 2 to 3 seconds; high temperature short time sterilization (HTST sterilization) method, in which heat treatment is continuously carried out at 72 to 75 °C for more than 15 seconds; high temperature holding sterilization (HTLT sterilization) method, in which heat treatment is carried out at 75 °C or higher for more than 15 minutes in a holding mode; high temperature short time sterilization (HTST sterilization) method, in which heat treatment is continuously carried out at 72 °C or higher for more than 15 seconds; low temperature holding sterilization (LTLT sterilization) method, in which heat treatment is carried out at 63 to 65 °C for 30 minutes in a holding mode; continuous low temperature sterilization (LTLT sterilization) method, in which heat treatment is continuously carried out at 65 to 68 °C for more than 30 minutes; and ultra-high temperature sterilization (LL sterilization) method, in which heat treatment is carried out at 135 to 150 °C for 1 to 4 seconds. The method is not limited to the above-mentioned methods, and any method can be used as long as the heat history represented by heating temperature (product temperature) × heating time × pressure is equal to or greater than the heat history of the above heat treatment methods. For example, the method used in the experimental examples described later can also be adopted, in which the raw milk mixture is heated at a product temperature of 95 °C for 1 minute under normal pressure.

[0086] [(4) Filling step]

[0087] As described above, the step of filling the raw milk mixture into a container can be carried out before fermenting the raw milk mixture. For example, the step of filling the raw milk mixture into a container can be carried out after the homogenization step and the pre-sterilization step, and before or after adding a starter lactic acid bacterium to the raw milk mixture.

[0088] The container filled with the raw milk mixture can be any container commonly used for manufacturing fermented milk (dairy products) by post-fermentation, and there are no particular restrictions on the size (capacity), material, or shape. For example, the container can be of a size (capacity) for single-person single consumption, or for household or commercial use. The container used can be made of any material such as plastic, glass, paper, or other materials. The container can be of any shape as long as it has strength and tightness; for example, the container can be cup-shaped, brick-packaged, or cheer-pack-shaped. The methods and equipment for filling the container can be commonly used methods and equipment.

[0089] [(a) Fermentation step]

[0090] In the present invention, the fermentation step can be carried out by adding a starter lactic acid bacterium to the raw milk mixture and then fermenting the raw milk mixture in the container.

[0091] The lactic acid bacterium used as a starter can be one or a combination of two or more selected from lactic acid bacteria commonly used in the manufacture of fermented milk, such as Lactobacillus bulgaricus, Streptococcus thermophilus, Lactobacillus lactis, Lactobacillus gasseri, Lactobacillus plantarum, Lactobacillus casei, Lactobacillus acidophilus, and Bifidobacterium. Preferably, the lactic acid bacterium is Lactobacillus bulgaricus. In addition, from the perspective of being standardized as a yogurt starter in the Codex Alimentarius, a mixed starter of Lactobacillus bulgaricus and Streptococcus thermophilus can also be used.

[0092] The amount of the starter (lactic acid bacterium) added to the raw milk mixture can be any amount commonly used in the manufacture of fermented milk, for example, 0.1 to 10% by mass, preferably 0.2 to 5% by mass, more preferably 0.5 to 4% by mass relative to the raw milk mixture. The starter can be added according to any method commonly used in the manufacture of fermented milk, such as a method of aseptically adding the starter to the raw milk mixture filled into the container, or a method of adding the starter online while the raw milk mixture is flowing through a pipeline and then filling the container with the mixture. The methods and equipment for adding the starter to the raw milk mixture are not limited to the above, and any known methods and equipment can be used.

[0093] The fermentation of the raw milk mixture can be carried out by adding a starter culture (lactic acid bacteria) and then allowing the mixture filled in a container to stand in a fermentation chamber set at a predetermined temperature.

[0094] The conditions for fermenting the raw milk mixture are adjusted in consideration of the type and amount of lactic acid bacteria and the like added to the raw milk, as well as the flavor, texture, physical properties, etc. of the fermented milk actually to be obtained. For example, the lower limit of the temperature (fermentation temperature) for fermenting the raw milk mixture is preferably 33 °C or higher, more preferably 35 °C or higher, and even more preferably 38 °C or higher. The upper limit of the temperature for fermenting the raw milk is preferably 50 °C or lower, more preferably 48 °C or lower, and even more preferably 45 °C or lower. The fermentation temperature range can be set by appropriately combining these lower and upper limits. Although not limited thereto, the fermentation temperature range can be, for example, 33 to 50 °C, 35 to 48 °C, or 38 to 45 °C.

[0095] The time for fermenting the raw milk (fermentation time) is the time until the pH of the fermented milk falls within the range of 5.3 to 5.9. In other words, when the pH of the fermented milk reaches a certain point within the range of 5.3 to 5.9, the fermentation ends. The pH range at the end of fermentation is preferably 5.4 to 5.8, and more preferably 5.5 to 5.7. Fermentation ending within this pH range gives a fermented milk with less acidity (one of the effects of the present invention) and a texture (hardness, mouthfeel) like that of tofu.

[0096] The method and equipment for fermenting the raw milk mixture can be any known method and equipment.

[0097] [(b) Heating step]

[0098] The heating step is a step of heat-treating the fermented milk that has reached a predetermined pH in the fermentation step while the fermented milk is filled in a container. The heat treatment is carried out without stirring the fermented milk (under non-stirring conditions).

[0099] This step is carried out to kill the lactic acid bacteria added to the raw milk mixture as a starter culture to stop the fermentation, and to kill bacteria to ensure the hygienic safety and shelf life of the food.

[0100] The heat treatment can be carried out according to any method under any conditions capable of achieving this purpose. For example, a heat treatment method can be used in which the heat history represented by heating temperature (product temperature) × heating time × pressure is equal to or greater than 75°C × 15 minutes × atmospheric pressure. The heat history of 75°C × 15 minutes × atmospheric pressure means that after the product temperature reaches 75°C under atmospheric pressure, the product is heated for 15 minutes under the same temperature condition. In this way, a sterilized fermented milk that meets the standards of sterilized fermented milk specified in the relevant regulations such as for milk can be obtained (fermented milk manufactured by heat sterilization by heating at 75°C for 15 minutes or more after fermentation, or by using a method with an equivalent or higher sterilization effect for heat sterilization). An example of a heating method that achieves a heat history of at least 75°C × 15 minutes × atmospheric pressure is a heat treatment in which the product is immersed in hot water at 85°C for 60 minutes under atmospheric pressure. Note that the atmospheric pressure used herein means a pressure state where the pressure inside the container is atmospheric pressure, excluding pressure states with artificial pressurization or depressurization.

[0101] The heat treatment can be carried out after the fermented milk packed in the container is sealed. Optionally, the fermented milk filled into the container can be heat-treated before being sealed and packed, and then sealed and packed.

[0102] Any known method and equipment can be used to heat the fermented milk together with its container.

[0103] After cooling, the sterilized fermented milk thus produced can be directly distributed on the market in the state of being filled, sealed, and packed in the container.

[0104] As described in the following examples, the sterilized fermented milk obtained by the manufacturing method according to the present invention has shape retention and / or resistance to boiling and disintegration, and has less sourness and a tofu-like hardness and texture (silken tofu and cotton tofu). Therefore, the sterilized fermented milk can be used as an ingredient containing milk protein in a variety of recipes, instead of tofu.

[0105] In this specification, the terms "comprise" and "contain" include the meanings of "consist of" and "consist essentially of".

[0106] Examples

[0107] The present invention will be described with reference to experimental examples to help understand the constitution and effects of the present invention. However, the present invention is not limited by these experimental examples in any way. Unless otherwise specified, the following experiments are all carried out at room temperature (25 ± 5°C) and atmospheric pressure (normal pressure). Unless otherwise specified, the unit "%" hereinafter means mass %, and the unit "parts" hereinafter means mass parts.

[0108] The raw materials used in the following experimental examples (examples and comparative examples) are as follows:

[0109] (Raw materials)

[0110] Cow's milk: Cow's milk with no composition adjustment (milk protein: 3.0 to 3.6%, milk fat: 3.5 to 4.2%, non-fat milk solids: 8.5 to 9.3%) (manufactured by Meiji Co., Ltd.)

[0111] Milk protein concentrate (MPC): MPC80 (casein: 64.4%, whey: 16.1%), Lacto Japan Co., Ltd.

[0112] Whey protein isolate (WPI): WPI895 (whey: 93.5%), Fonterra Japan

[0113] Lactic acid bacteria starter: Lactobacillus bulgaricus OLL1073R-1 (1073R-1 lactic acid bacteria) isolated from Meiji Probio yogurt R-1 (manufactured by Meiji Co., Ltd.).

[0114] Experimental Example 1: Effects of type and content of milk protein, whether secondary heating treatment is performed, and pH at the end of fermentation

[0115] Various fermented milks (Examples 1 and 2, Comparative Examples 1 to 10) were prepared according to the method described below, and the types and contents of milk proteins added to the raw milk mixture, whether secondary heat treatment was performed, and the pH at the end of fermentation were evaluated for their effects on the shape retention, boiling resistance to disintegration, and texture of the obtained fermented milk.

[0116] (1) Preparation of fermented milk

[0117] (a) Without secondary heat treatment after fermentation: Comparative Examples 1 to 6

[0118] MPC or WPI was added to 500 g of cow's milk (homogenized during the manufacturing step) at a ratio of 2% and mixed to prepare raw milk containing the components shown in Table 1 (Comparative Examples 1 to 3: adding MPC, Comparative Examples 4 to 6: adding WPI). The raw milk was heated at 95°C for 1 minute (pre-sterilization treatment) to prepare a raw milk mixture. The raw milk mixture was cooled to 43°C, and a lactic acid bacteria starter was added (inoculated) at a ratio of 3%. Thereafter, the mixture was filled into cylindrical plastic cup containers (diameter 7 cm, filling capacity 100 g), and left to ferment in a fermentation chamber (43°C) until the pH shown in Table 1 was reached. After the pH reached the predetermined value, the mixture was cooled in a refrigerator (below 10°C) to produce fermented milk (Comparative Examples 1 to 6).

[0119] (b) With secondary heat treatment after fermentation: Comparative Examples 7 to 10 and Examples 1, 2

[0120] MPC (or WPI) was added to 500 g of milk (homogenized during the manufacturing process) at a ratio of 2% and mixed to prepare raw milk containing the components shown in Table 1 (Comparative Examples 7 to 10: MPC added, Comparative Examples 11 and Examples 1, 2: WPI added). The raw milk was heated at 95 °C for 1 minute (pre-sterilization treatment) to prepare a raw milk mixture. The raw milk mixture was cooled to 43 °C, and a lactic acid bacteria starter was added (inoculated) at a ratio of 3%. Thereafter, the mixture was filled into plastic cup containers (filling capacity: 100 g) and allowed to stand and ferment in a fermentation chamber (43 °C) until the pH shown in Table 1 was reached. After the pH reached the predetermined value, the containers were immersed in hot water at 85 °C for 60 minutes (secondary heating treatment), then transferred and immersed in ice-cold water for 30 minutes to cool, thereby producing sterilized fermented milk (Comparative Examples 7 to 10 and Examples 1, 2).

[0121] [Table 1]

[0122]

[0123] (2) Evaluation of the prepared sterilized fermented milk

[0124] (a) Texture and shape retention

[0125] As described above, after preparation, the containers were inverted, and the cooled fermented milk (Comparative Examples 1 to 6) and sterilized fermented milk (Comparative Examples 7 to 10 and Examples 1, 2) (product temperature 25 °C) were directly placed on a plate, and their texture (liquid, semi-solid or solid) was confirmed. If the fermented milk after standing for 60 minutes was in a fluid state like milk, the fermented milk was determined to be "liquid". If the fermented milk was in a semi-fluid state like a milkshake or soft yogurt and broke under its own weight and could not maintain its shape, the fermented milk was determined to be "semi-solid". In both cases, the fermented milk was evaluated as "Shape retention: ×". Fermented milk that could maintain its shape under its own weight without breaking was determined to be "solid" and was evaluated as "Shape retention: ○". Not only the case where the cup shape was maintained was evaluated as maintaining the shape without breaking, but also the case where the cup shape slightly sagged due to its own weight and the corners (edges) did not break was evaluated as maintaining the shape without breaking.

[0126] (b) Resistance to boiling and disintegration

[0127] After preparation, in the cooled fermented milk (Comparative Examples 1 to 10 and Examples 1 and 2), the fermented milk determined to be in a solid state was evaluated for its resistance to boiling and disintegration. The resistance to boiling and disintegration was evaluated by immersing 100 g of the sterilized fermented milk directly taken out of the container in 1 L of hot water (80 °C) for 10 minutes and comparing the shape before and after immersion. The fermented milk with the whole shape broken was determined as "resistance to boiling and disintegration: ×", the fermented milk with only a part of the shape broken was determined as "resistance to boiling and disintegration: Δ", and the fermented milk with the shape not broken was determined as "resistance to boiling and disintegration: ○". Not only the case where the shape before immersion was maintained was evaluated as maintaining the shape, but also the case where the whole shape swelled after immersion in hot water and the corners (edges) were not broken was evaluated as maintaining the shape.

[0128] (c) Sour taste and texture

[0129] A panel of 6 experts trained in sensory evaluation tasted the fermented milk samples (Comparative Examples 1 to 10 and Examples 1 and 2) cooled to 10 °C after preparation and evaluated the sour taste and texture (hardness and mouthfeel) according to the following method.

[0130] [Sour taste]

[0131] Compared with commercially available plain yogurt (product name: Meiji Bulgaria Yogurt LB81 Plain, manufactured by Meiji Co., Ltd., pH 4.2, control), the sour taste of each fermented milk sample (Comparative Examples 1 to 10 and Examples 1 and 2) was evaluated according to the following criteria.

[0132] "Sour taste: +": The same degree of sour taste as the control.

[0133] "Slightly sour taste: ±": The sour taste is lower than the control, but still slightly sour.

[0134] "No sour taste: -": The sour taste is not felt.

[0135] [Texture]

[0136] Based on the texture (hardness and the texture felt on the tongue (the feeling when the fermented milk is put into the mouth and squeezed with the tongue)) compared with the texture of commercially available regular cotton tofu and silk tofu (control), the fermented milk samples (Comparative Examples 1 to 10 and Examples 1 and 2) were classified according to the following criteria and the quality of the texture was evaluated.

[0137] [Table 2]

[0138]

[0139] The kapi tofu and kinugoshi tofu used as controls both meet the standards listed in the "General Composition Table - Inorganic Substances and Vitamins" of the 2020 Edition (8th Revision) of the Japanese Food Standard Composition Table (Ministry of Education, Culture, Sports, Science and Technology, Japan).

[0140] The maximum loads (N) of kapi tofu and kinugoshi tofu (3 samples each) measured in the fracture test described below are shown in Table 3.

[0141] [Table 3]

[0142] Sample 1 Sample 2 Sample 3 Average value Kagori tofu 6.93 7.15 7.86 7.31N Kinugoshi tofu 5.07 5.38 5.79 5.41N

[0143] [Fracture Test]

[0144] (1) Measuring Equipment

[0145] Creep meter (viscoelastic analyzer): Rheoner II (Model: RE-3305S, parallel plate type) manufactured by Yamaden Co., Ltd.

[0146] (2) Fracture Test Conditions

[0147] Plunger: Disk-shaped (diameter: 3 cm, thickness: 8 mm)

[0148] Contact area with the test sample: 7.1 cm 2

[0149] Compression speed: 1 mm / second

[0150] Compression distance: 10 mm

[0151] (3) Fracture Test Method

[0152] Place the test sample (product temperature: 25°C) in a plastic cup container (filled volume: 100 g) on the test bench of the creep meter. Lower the plunger from above the test sample so that the plunger contacts the surface of the test sample, applying a load in the thickness direction, and thus conduct the fracture test under the above conditions. Use an automatic analyzer (Model: CA-3305, manufactured by Yamaden Co., Ltd.), a peak indicator (Model: PA-3305, manufactured by Yamaden Co., Ltd.), and a recorder to record and analyze the compression curve. Record the maximum value of the load (N) applied during the period from the start of measurement to the fracture of the test sample as the maximum load (N).

[0153] (3) Evaluation Results

[0154] Table 4 shows the evaluation results of the fermented milk produced in section (1) (Comparative Examples 1 to 10 and Examples 1 and 2).

[0155] [Table 4]

[0156]

[0157] 4*: Similar to agar-agar hardness and texture

[0158] ND: Not measured

[0159] As shown in Table 4, the raw milk mixture used (as a fermented milk raw material) was prepared by adding WPI to cow's milk in the following manner to contain milk protein: 2.49 mass % whey and 2.48 mass % casein (the amount of whey relative to 100 mass parts of casein: 100.4 mass parts). The raw milk mixture was fermented with lactic acid bacteria in a separate container until the pH reached 5.4 to 5.8, and then the container was subjected to a secondary heating treatment within the pH range (equivalent to a thermal history of at least 75°C × 15 minutes × normal pressure). This resulted in a coagulated sterilized fermented milk (Examples 1 and 2) that had good shape retention and was not easily disintegrated even when boiled. In addition, the coagulated sterilized fermented milk did not have the sour taste of ordinary yogurt, was harder than silken tofu, but softer than kapok tofu, and had a good texture.

[0160] Fermented milk (Comparative Examples 1 to 3, 7 to 9) was prepared using a raw milk mixture (as a fermented milk raw material) prepared by adding MPC to cow's milk in the following manner to include milk protein: 0.94% by mass of whey and 3.76% by mass of casein (the amount of whey relative to 100 parts by mass of casein: 25.0 parts by mass). The fermented milk (Comparative Examples 1 to 3, 7 to 9) had poor shape retention, or had good shape retention but poor resistance to boiling disintegration. In addition, the fermented milk (Comparative Examples 4 to 6, 10) prepared by adding WPI to cow's milk as a fermented milk raw material so that the milk protein content was the same as in Examples 1 and 2 had good shape retention, but the fermented milk (Comparative Examples 4 to 6) that was not subjected to secondary heating treatment did not have good resistance to boiling disintegration. Even when a secondary heating treatment was performed, the fermented milk (Comparative Example 10) whose pH at the end of fermentation was set to 5 or less had good shape retention and resistance to boiling disintegration, but tended to have a strong sour taste and a hard texture.

[0161] Experimental Example 2: Effects of WPI blending amount

[0162] (1) Production of fermented milk

[0163] Based on the results of Experimental Example 1, various fermented milk samples (Examples 3 to 8 and Comparative Examples 11 to 26) were prepared using WPI as a milk protein concentrate in the amounts shown in Table 5 (see Table 5). The fermented milk of Comparative Examples 11 to 21 was prepared according to the method described in Experimental Example 1(1)(a) above (pH at the end of fermentation: 5.8 or 5.4, without secondary heat treatment), and the fermented milk of Examples 3 to 8 and Comparative Examples 22 to 26 was prepared according to the method described in Experimental Example 1(1)(b) above (pH at the end of fermentation: 5.8 or 5.4, with secondary heat treatment).

[0164] [Table 5]

[0165]

[0166] (2) Evaluation of fermented milk

[0167] The obtained fermented milk was evaluated in terms of properties, shape retention, boiling resistance to disintegration, sour taste, and texture (hardness and mouthfeel) in the same manner as in Experimental Example 1.

[0168] For solid fermented milk, a fracture test was conducted according to the fracture test method for tofu in Experimental Example 1, and the maximum load (N) was determined. The fermented milk determined to be solid was subjected to a boiling resistance to disintegration test, and the turbidity of the soup after the test was further measured according to the method described below. Based on the turbidity, the degree of disintegration of the fermented milk (e.g., the degree of leakage of contents such as milk fat and milk protein) was evaluated.

[0169] [Turbidity test]

[0170] To evaluate the boiling resistance to disintegration, the fermented milk (100 g) taken out from the container was immersed in 1 L of hot water (80 °C) for 10 minutes. After that, the remaining liquid after removing the fermented milk was used as the soup. After cooling, the soup was passed through a 60# filter, and the turbidity (NTU) of the filtrate was measured using a 200P turbidimeter (HACH). The evaluation was carried out as follows based on the turbidity (NTU) of the filtrate:

[0171] ○: <5 NTU

[0172] Δ: 10 to 5 NTU

[0173] ×: >10 NTU

[0174] (3) Evaluation results

[0175] Table 6 shows the evaluation results of the fermented milk (Comparative Examples 11 to 26 and Examples 3 to 8) manufactured in section (1). Figure 1 Images of the soup (contained in a beaker) of Comparative Examples 24 and 25 and Examples 5 and 6 for which a soup turbidity test was conducted are shown.

[0176] [Table 6]

[0177]

[0178] ND: Not measured Note: Maximum load of kinu-dofu (n = 3): 6.93 N to 7.86 N (average: 7.31 N)

[0179] Maximum load of kinugoshi-dofu (n = 3): 5.07 N to 5.79 N (average: 5.41 N)

[0180] As shown in Table 6, as the fermented milk raw material, a raw milk mixture prepared in the following manner was used: whey with a milk protein content of 1.56 to 2.95% by mass and casein of 2.46 to 2.5% by mass. With respect to 100 parts by mass of casein, the amount of whey was in the range of 62.4 to 119.9 parts by mass. The raw milk mixture was fermented with lactic acid bacteria in a container until the pH reached 5.4 to 5.8, and then the container was subjected to a secondary heat treatment within this pH range (equivalent to a heat history of at least 75°C × 15 minutes × normal pressure). It was confirmed that the resulting set-type sterilized fermented milk (Examples 3 to 8) had good shape retention and was not easily disintegrated even when boiled. It was also confirmed that the set-type sterilized fermented milk did not have the sour taste felt in conventional yogurt and had a texture (hardness and mouthfeel) similar to that of tofu (from kinu-dofu to kinugoshi-dofu).

[0181] In addition, fermented milk (Comparative Examples 11 to 14, 22 to 25) was prepared using a raw milk mixture prepared in such a way that the whey had a milk protein content of 0.63 to 1.1% by mass and casein of 2.51 to 2.53% by mass (with respect to 100 parts by mass of casein, the amount of whey was 24.9 to 43.8 parts by mass) as the fermented milk raw material. The fermented milk (Comparative Examples 11 to 14, 22 to 25) had poor shape retention, or even if the shape retention was good, the boiling resistance and disintegration resistance were poor. Fermented milk (Comparative Examples 15 to 20) prepared using a fermented milk raw material prepared in the same manner as in Examples 3 to 8 but without the secondary heat treatment had good shape retention but poor boiling resistance and disintegration resistance, and the soup was also highly turbid. In addition, fermented milk (Comparative Examples 21, 26) prepared using a raw milk mixture prepared in such a way that the whey had a milk protein content of 3.42% by mass and casein of 2.45% by mass (with respect to 100 parts by mass of casein, the amount of whey was 139.6 parts by mass) as the fermented milk raw material had good shape retention and boiling resistance and disintegration resistance, but tended to have an overly hard texture.

[0182] Industrial applicability

[0183] Fermented milk as a health food can now be used for applications that have never been seen before (general cooking applications; for example, uses as tofu-like ingredients: ingredients for hot pot, tofu steak, chilled tofu, and mapo tofu). The fermented milk of the present invention does not disintegrate when boiled, and whey protein is not lost into the soup, so it can be eaten. The present invention can obtain fermented milk without sour taste. Overall, this will drive the development of healthy eating scenarios and the development of the new fermented milk market.

Claims

1. A coagulated sterilized fermented milk, which comprises 1.5 to 3.0% by mass of whey protein, and 2.0 to 3.0% by mass of casein, wherein the amount of whey protein is 50 to 125 parts by mass relative to 100 parts by mass of casein, and the coagulated sterilized fermented milk has a pH of 5.3 to 5.

9.

2. The sterilized fermented milk according to claim 1, which comprises 9.5 to 11.2% by mass of fat-free milk solids.

3. The sterilized fermented milk according to claim 1 or 2, which has shape retention and / or boiling resistance to disintegration.

4. The sterilized fermented milk according to claim 1 or 2, wherein the maximum load at break in a fracture test using a plunger is 5.0 to 8.0 N.

5. A method for manufacturing a coagulated sterilized fermented milk, which comprises the following steps: Adding lactic acid bacteria to the raw milk mixture to ferment the raw milk mixture in a container until the pH reaches 5.3 to 5.9, wherein the raw milk mixture contains 1.5 to 3.0% by mass of whey protein and 2.0 to 3.0% by mass of casein, and the amount of whey protein is 50 to 125 parts by mass relative to 100 parts by mass of casein; and Heating the obtained fermented milk together with the container such that the heat history is at least the following: 75 °C × 15 minutes × atmospheric pressure.

6. The manufacturing method according to claim 5, wherein the raw milk mixture comprises 9.5 to 11.2% by mass of fat-free milk solids.

7. The manufacturing method according to claim 5 or 6, wherein before adding lactic acid bacteria, the raw milk mixture is homogenized and sterilized.

8. The manufacturing method according to claim 7, which further comprises, before step (a), a step of homogenizing and sterilizing the raw milk mixture, the raw milk mixture comprising 1.5 to 3.0% by mass of whey protein and 2.0 to 3.0% by mass of casein, wherein the amount of whey protein is 50 to 125 parts by mass relative to 100 parts by mass of casein.

9. The manufacturing method according to claim 5 or 6, wherein the fermentation temperature is 35 to 48 °C.

10. The manufacturing method according to claim 7, wherein the fermentation temperature is 35 to 48 °C.

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