Sterilized fermented milk and method for producing same

Abstract

The invention provides solidified sterilized fermented milk in a solid form. The coagulated sterilized fermented milk according to the present invention is characterized in that the curd tension (X) and the post-stirring particle diameter (Y) satisfy the following conditions: the curd tension (X): 20-220 g, the post-stirring particle diameter (Y): 166.5-2.5 [mu] m, and Y < =-0.82 X + 183.

Description

[0001] Cross-references to related patent applications

[0002] This application claims priority based on Japanese Patent Application No. 2022-146606 filed on September 14, 2022, the entire disclosure of which is incorporated herein by reference. Technical Field

[0003] The present invention relates to coagulated sterilized fermented milk and a method for producing the coagulated sterilized fermented milk. More specifically, the present invention relates to coagulated sterilized fermented milk that is filled in a container, fermented (post-fermented) and solidified in the container and a method for producing the coagulated sterilized fermented milk. Background Art

[0004] Sterilized fermented milk refers to fermented milk produced by heating at 75°C for at least 15 minutes after fermentation or by heat sterilization according to a method that exerts an equal or higher sterilization effect ("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 (hereinafter referred to as "Ministerial Ordinance on Milk and Milk Products"): Ministry of Health, Labour and Welfare of Japan). Ordinary fermented milk containing live lactic acid bacteria will experience changes in taste and sourness over time, and will also show syneresis as the acidity increases. In contrast, sterilized fermented milk has a long shelf life due to the death of microorganisms including lactic acid bacteria, and undergoes less flavor changes during storage, so it is in high market demand.

[0005] However, heat sterilization of raw milk after fermentation causes milk protein to aggregate and precipitate. Therefore, a method is used in which a stabilizer as described below is added to fermented milk, and then heat sterilization is performed while stirring and circulating with a stirrer to inhibit aggregation and precipitation during heat sterilization: the stabilizer is, for example, the following: HM pectin, LM pectin, gelatin, carrageenan, xanthan gum, methylcellulose, sodium carboxymethylcellulose, hydroxypropyl methylcellulose, sodium polyacrylate, curdlan, dextran, tamarind gum, guar gum, tara gum, locust bean gum, glucomannan, gum arabic, gellan gum, alginic acid, sodium alginate, calcium alginate, ammonium alginate, potassium alginate, propylene glycol alginate, tremel gum, agar, potato starch, tapioca flour, cellulose, fermented cellulose, brown algae extract, guar gum enzymatic hydrolysate, gluten, gluten decomposition product, soybean hemicellulose, Abelmoschus truncatus manihot), acetylated distarch adipate, acetylated oxidized starch, acetylated distarch phosphate, sodium starch octenylsuccinate, starch acetate, oxidized starch, sodium starch glycolate, hydroxypropyl distarch phosphate, hydroxypropyl starch, distarch phosphate, monostarch phosphate, and phosphorylated distarch phosphate.

[0006] For example, PTL 1 discloses that a substance containing β-glucan (Aureobasidium culture solution) is added as a stabilizer after fermentation, followed by heat sterilization, and homogenization is performed by mixing after heat sterilization to liquefy the mixture. PTL 2 discloses a method for producing fermented milk in which a milk preparation containing a milk raw material, a cross-linked modified starch (stabilizer) and a fermentation bacterium is fermented to a pH of 5.3 to 6, and then the resulting fermented product is heat sterilized, the fermented product in the form of curd is heat sterilized while being broken with stirring, and the resulting fermented milk is then filled into a container.

[0007] As described above, all the conventional and documented sterilized fermented milks are of the paste-like soft type or liquid drink type, which are produced by breaking the curd after fermentation. There is no solid coagulated fermented milk so far.

[0008] Citation List

[0009] Patent Literature

[0010] PTL 1: JP2005-137245A

[0011] PTL 2: JP2017-63727A Summary of the invention

[0012] Problem that the invention aims to solve

[0013] The present invention aims to provide a solidified sterilized fermented milk, specifically a solid sterilized fermented milk made by filling in a container, fermenting (post-fermentation) and solidifying in the container, and to provide a method for producing the solidified sterilized fermented milk. More specifically, the present invention aims to provide a solidified sterilized fermented milk in which the aggregation of milk proteins occurring during the heat treatment after fermentation is suppressed, and to provide a method for producing the solidified sterilized fermented milk.

[0014] Solutions for solving problems

[0015] In order to produce coagulated sterilized fermented milk to achieve the above-mentioned purpose, the present inventors conducted extensive research and found that: fermenting a raw milk mixture containing lactic acid bacteria in a container at 37°C to 43°C until the pH reaches 3.8 to 5.4, and then heating the mixture at a heat history of 75°C for more than 15 minutes without destroying the curd, can even provide solid sterilized fermented milk with suppressed aggregation of milk protein and smooth texture.

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

[0017] (I) Coagulation type sterilized fermented milk

[0018] (I-1) A coagulated sterilized fermented milk, wherein the coagulation tension (X) and the particle size after stirring (Y) satisfy the following conditions:

[0019] The curd tension (X) is 20g to 220g,

[0020] The particle size (Y) after stirring is 166.5 μm to 2.5 μm, and

[0021] Y≤-0.82X+183.

[0022] (I-2) The sterilized fermented milk according to (I-1), wherein the curd tension (X) is 35 g or more.

[0023] (I-3) The sterilized fermented milk according to (I-1) or (I-2), which contains 6% by mass or less of fat and 8 to 16% by mass of fat-free milk solids, and has a pH of 3.8 to 5.4,

[0024] The condition is that the pH of the sterilized fermented milk containing 15% by mass or more of fat-free milk solids and 0.5% by mass or less of fat or the sterilized fermented milk containing 15% by mass or more of fat-free milk solids and no externally added sugar is 3.8 to 4.5.

[0025] (I-4) The sterilized fermented milk according to (I-3), which contains 15% by mass or less of sugars.

[0026] (II) Method for producing coagulated sterilized fermented milk

[0027] (II-1) A method for producing sterilized fermented milk according to any one of (I-1) to (I-4), comprising the following steps:

[0028] fermenting the raw milk mixture to which lactic acid bacteria have been added in a container at 37°C to 43°C until the pH reaches 3.8 to 5.4 (fermentation step), and

[0029] The obtained fermented milk is heated together with the container (heating treatment step).

[0030] (II-2) The production method according to (II-1), wherein the raw milk mixture is homogenized and sterilized before the lactic acid bacteria are added.

[0031] (II-3) The production method according to (II-1) and (II-2), further comprising the step of homogenizing and sterilizing the raw milk mixture before the fermentation step and before adding lactic acid bacteria.

[0032] (II-4) The production method according to any one of (II-1) to (II-3),

[0033] wherein the raw milk mixture contains 6% by mass or less of fat and 8 to 16% by mass of fat-free milk solids,

[0034] The conditions are:

[0035] When the raw milk mixture contains 15% by mass or more of fat-free milk solids and 0.5% by mass or less of fat, or when the raw milk mixture contains 15% by mass or more of fat-free milk solids and contains no externally added sugars, the raw milk mixture is fermented until the pH reaches 3.8 to 4.5.

[0036] (II-5) The production method according to (II-4), wherein the raw material milk mixture contains 15% by mass or less of sugars.

[0037] Effects of the Invention

[0038] The manufacturing method of the present invention manufactures and provides solidified sterilized fermented milk. Preferably, the manufacturing method of the present invention manufactures and provides solid sterilized fermented milk that is easy to disintegrate with the tongue in the oral cavity and has a smooth texture without any graininess by adopting a post-fermentation method.

[0039] The sterilized fermented milk produced by the production method of the present invention is a solid coagulated sterilized fermented milk, but is easily disintegrated by the tongue in the oral cavity, and has a smooth texture without any graininess, which is the same as the fermented milk produced without sterilization. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] [ Figure 1 ] A graph showing the texture (O, ×) of the sterilized fermented milk of Examples 1 to 16 and the sterilized fermented milk of Comparative Examples 1 to 6 was plotted with the curd tension (g) as the horizontal axis and the particle size after stirring (μm) as the vertical axis. DETAILED DESCRIPTION

[0041] (I) Coagulation type sterilized fermented milk

[0042] In the "Ministry's Ordinance on Standards for the Composition of Milk and Dairy Products, etc." (Milk, etc. Ministry's Ordinance), fermented milk is defined as "a product obtained by fermenting milk or milk containing an equal or greater amount of fat-free milk solids with lactic acid bacteria or yeast and then forming it into a paste or liquid, or a frozen product", where the fat-free milk solids are set to 8.0% or more. These fermented milks are generally classified into the following categories: (a) firm fermented milk: obtained by putting raw milk into a container, fermenting it and solidifying it in the container (referred to as "coagulated fermented milk" or "post-fermented milk"); (b) paste-like fermented milk: obtained by fermenting in a large tank, breaking the formed curd, mixing it with pulp, sauce, etc. as needed, and filling it in a container (referred to as "soft yogurt" or "pre-fermented milk"); and (c) liquid fermented milk: obtained by finely grinding solid fermented milk or paste-like fermented milk using a homogenizer, etc. to liquefy it, mixing it with pulp, sauce, etc. as needed, and filling it in a container (referred to as "yogurt drink").

[0043] The fermented milk targeted by the present invention is a coagulated (solid) fermented milk that is post-fermented by lactic acid bacteria among these fermented milks. The fermented milk targeted by the present invention is also a fermented milk that is sterilized by heat treatment after fermentation ("sterilized fermented milk"). Specifically, the fermented milk targeted by the present invention is a fermented milk that is fermented as specified by the provincial ordinance of milk, etc. and then heated at 75°C for at least 15 minutes, or is sterilized by heat treatment using a method that has an equivalent or higher sterilization effect.

[0044] Typically, fermented milk that is heat-sterilized under the above-mentioned thermal history conditions after fermentation will undergo milk protein coagulation, resulting in a granular texture and causing precipitation and syneresis, and cannot become a product of marketable quality. Therefore, a common method is to heat the curd formed after fermentation and break the curd at the same time. In contrast, the sterilized fermented milk of the present invention suppresses milk protein coagulation and does not have a granular texture, although it is a coagulated (solid) sterilized fermented milk obtained by heating the curd formed after fermentation under the above-mentioned thermal history conditions without breaking the curd. In addition, the sterilized fermented milk of the present invention has a unique mouthfeel of yogurt (a texture that easily disintegrates when in contact with the tongue in the oral cavity).

[0045] The sterilized fermented milk of the present invention having these characteristics meets the following requirements:

[0046] Curd tension (X): 20g to 220g

[0047] Particle size after stirring (Y): 166.5μm to 2.5μm

[0048] Y≤-0.82X+183

[0049] The phrase "coagulation tension" used herein refers to the hardness (g) of the sterilized fermented milk when the product temperature is adjusted to 5°C, and can be measured using a MAX ME-500 coagulation meter (manufactured by I. Techno Engineering) in the manner described in the following examples. A yogurt knife with a 100 g weight is inserted into the test sample (sterilized fermented milk) from the top surface at a load of about 2 g / sec, and the load applied until the test sample breaks is measured as the coagulation tension (g). Details including the measurement conditions are as described in the examples.

[0050] The range of curd tension is as described above, but preferably is above 35g. By making the sterilized fermented milk have a curd tension of 35g or more, a sterilized fermented milk that can withstand vibration during transportation while having a desired texture (mouthfeel) can be provided. More preferably, the curd tension is above 40g. The upper limit of the curd tension is preferably 200g, more preferably 180g, even more preferably 175g, and particularly preferably 140g. The preferred range of curd tension can be set by appropriately combining these lower and upper limits. Examples of the range of curd tension are 35 to 200g, 40 to 180g, 40 to 175g or 40 to 140g, but are not limited thereto. The sterilized fermented milk with curd tension within these ranges has a better texture (mouthfeel).

[0051] The "particle size after stirring" refers to the particle size measured by subjecting the sterilized fermented milk adjusted to a product temperature of 5°C to a predetermined stirring treatment according to the method described in the Examples below, and measuring the resulting stirred product using a SALD-2200 laser diffraction particle size distribution analyzer (manufactured by Shimadzu Corporation). Details including the measurement conditions are as described in the Examples.

[0052] The range of the particle size after stirring is as described above, but it is preferably less than 150 μm, more preferably less than 145 μm, and particularly preferably less than 100 μm. The lower limit of the particle size after stirring is preferably 20 μm, more preferably 30 μm, and particularly preferably 35 μm. The preferred range of the particle size after stirring can be set by appropriately combining these lower and upper limits. Examples of the range of the particle size after stirring are 20 to 150 μm, 30 to 145 μm, or 35 to 100 μm, but are not limited to this. Sterilized fermented milk with a particle size within these ranges after stirring has a better texture (no graininess).

[0053] The sterilized fermented milk of the present invention preferably contains 6.5% by mass or less, preferably 6% by mass or less of fat and 8 to 16% by mass of fat-free milk solids per 100% by mass (wet mass) of the sterilized fermented milk, and has a pH of 3.8 to 5.4. In addition, the sterilized fermented milk of the present invention preferably contains 15% by mass or less of sugars.

[0054] The sterilized fermented milk of the present invention includes the sterilized fermented milk having the following composition and pH:

[0055] (a) a fat content of 0.1 to 6.5% by mass, preferably 0.5 to 6% by mass, more preferably 1 to 4% by mass; a fat-free milk solids content of 8 to 16% by mass, preferably 8.5 to 15.5% by mass, more preferably 8 to less than 15% by mass; a carbohydrate content of 5 to 15% by mass, preferably 5 to 13% by mass, more preferably 5 to 12% by mass; a pH of 4.5 to 5.4, preferably 4.5 to 5.2, more preferably 4.5 to 5.0;

[0056] (b) a fat content of more than 0.5% by mass and less than 4% by mass, preferably 1 to 3.5% by mass; a fat-free milk solids content of 15 to 16% by mass, preferably more than 15% by mass and less than 16% by mass; a carbohydrate content of 5 to 10% by mass, preferably 7 to 9% by mass; a pH of 3.8 to less than 4.5, preferably 4.0 to 4.4; preferably, the carbohydrate is lactose derived from the raw milk, and no other carbohydrates (externally added carbohydrates) are contained; and

[0057] (c) the fat content is 0.5% by mass or less, preferably 0.1 to 0.5% by mass; the fat-free milk solids content is 15 to 16% by mass, preferably greater than 15% by mass and less than 16% by mass; the carbohydrate content is 5 to 15% by mass, preferably 8 to 15% by mass; and the pH is 3.8 to less than 4.5, preferably 4.0 to 4.4.

[0058] The sterilized fermented milk of the present invention preferably does not include the sterilized fermented milk having the following composition and pH:

[0059] (d) a fat-free milk solids content of 15% by mass or more and a fat content of 0.5% by mass or less, and a pH of 4.7 to 5.4; and

[0060] (e) The fat-free milk solids content is 15% by mass or more, the fat content is more than 0.5% by mass and less than 4% by mass, no sugars (externally added sugars) other than lactose derived from raw material milk are contained, and the pH is 4.7 to 5.4.

[0061] The fat content in the sterilized fermented milk can be analyzed and measured according to the Roese-Gottlieb method. The ratio of fat-free milk solids contained in the sterilized fermented milk can be calculated by subtracting the amount of fat and the amount of water measured according to the above method from the total amount of the sterilized fermented milk. The amount of water in the sterilized fermented milk can be determined by calculating the solid concentration (mass %) according to the direct drying method and subtracting the result from the total amount taken as 100 mass %.

[0062] The above-mentioned sugars include lactose derived from raw milk, and externally added sugars not derived from raw milk, specifically monosaccharides, disaccharides, oligosaccharides, polysaccharides and sugar alcohols. Note that raw milk (milk, milk components and dairy products) does not substantially contain sugars other than lactose. However, if the raw milk has been treated with lactase or other enzymes to decompose lactose, this does not apply.

[0063] Externally added sugars are preferably sugars such as monosaccharides and disaccharides (externally added sugars). Without limitation, monosaccharides include glucose, fructose and galactose; disaccharides include sucrose, maltose, lactose and trehalose; oligosaccharides include oligofructose, soybean oligosaccharides, raffinose (beet oligosaccharides), oligogalactose and isomaltooligosaccharides; polysaccharides include EPS (extracellular polysaccharides) and pectin; and sugar alcohols include xylitol, sorbitol and maltitol. The sterilized fermented milk of the present invention may not contain externally added sugars (preferably externally added sugars); however, when externally added sugars (preferably externally added sugars) are compounded, the amount is preferably, but not limited to, less than 6% by mass.

[0064] The ratio of lactose in the sugars contained in the sterilized fermented milk can be analyzed and measured using a commercially available measurement kit (F-kit lactose / D-galactose: JK International Inc.). When the sterilized fermented milk contains sugars other than lactose, the total amount of these sugars can be calculated by subtracting the amount of dietary fiber from the amount of carbohydrates contained in the sterilized fermented milk. The amount of carbohydrates contained in the sterilized fermented milk can be determined by subtracting other basic nutrients (water, protein, lipid and ash) from the sterilized fermented milk. The ratio of water, protein, lipid, ash and dietary fiber in the sterilized fermented milk can be measured according to standard methods in the food industry. Specifically, the moisture content can be measured according to the direct drying method. The protein content can be measured according to the nitrogen quantitative conversion method, in which the total nitrogen content determined according to the Kjeldahl method is multiplied by the nitrogen protein conversion factor to determine the protein content. The ash content can be measured according to the dry direct ash method. The dietary fiber content can be measured by high performance liquid chromatography (enzyme-HPLC method).

[0065] The water content of the sterilized fermented milk of the present invention is set within a range of 75 to 90% by mass.

[0066] The requirements for the coagulation tension (X) and the particle size after stirring (Y) are met, and the sterilized fermented milk of the present invention shows that the aggregation of milk protein is suppressed and the texture does not have a grainy feeling despite being a sterilized fermented milk (solid state). In addition, the sterilized fermented milk has a mouthfeel unique to the coagulated yogurt (a texture that is easily disintegrated when it comes into contact with the tongue in the oral cavity). The presence or absence of such a texture can be evaluated by adjusting the target sterilized fermented milk to a product temperature of 5°C and then conducting a sensory evaluation test by an expert panel according to the method described in the Examples below.

[0067] (II) Method for producing coagulated sterilized fermented milk

[0068] The sterilized fermented milk of the present invention can be produced by a method comprising the following steps A and B:

[0069] (a) a step of fermenting the raw milk mixture to which lactic acid bacteria have been added in a container until the pH reaches 3.8 to 5.4 (hereinafter "step A" or "fermentation step"); and

[0070] (b) A step of subjecting the obtained fermented milk to a heat treatment while it is in a container (hereinafter "step B" or "heating step").

[0071] The manufacturing steps of the present invention described above 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 referred to as "pretreatment steps". In these pretreatment steps, the homogenization step (2) and the pre-sterilization step (3) may be performed in any order. The raw milk mixture prepared in step (1) may first be subjected to the homogenization step (2) and then to the pre-sterilization step (3); or the pre-sterilization step (3) may first be subjected to the homogenization step (2) and then to the homogenization step (2). The homogenization step (2) and the pre-sterilization step (3) may also be performed simultaneously.

[0072] 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 (4) may be performed before adding lactic acid bacteria to the raw milk mixture obtained in the pretreatment steps (1) to (3), or may be performed after adding lactic acid bacteria to the raw milk mixture obtained in the pretreatment steps (1) to (3).

[0073] Although not limited, the production process of the present invention preferably includes a filling step after the pretreatment steps (1) to (3) and before the addition of lactic acid bacteria in step A. In other words, it is preferred that the raw milk mixture obtained in the pretreatment steps (1) to (3) is filled into a container, and then step A is performed in which lactic acid bacteria are added to the raw milk mixture filled in the container to ferment the mixture in the container.

[0074] Each step is described below.

[0075] (1) Raw milk mixture preparation steps

[0076] The “raw material milk mix” targeted by the present invention is a composition containing milk components derived from cow's milk.

[0077] The raw milk mixture is prepared using one or more raw materials selected from the following: raw milk squeezed from a dairy cow, cow's milk, skim milk, whole milk powder, skim milk powder, whole condensed milk, skim condensed milk, sweetened condensed milk, sweetened skim condensed milk, sugar-free condensed milk, sugar-free skim condensed milk, whey, whey powder, demineralized whey, demineralized 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., preferably so that the fat content in the raw milk mixture taken as 100% by mass (wet mass) is 6.5% by mass or less, preferably 6% by mass or less, and the fat-free milk solid content is 8 to 16% by mass.

[0078] Furthermore, when cow's milk is used as a raw material, it is sufficient if the milk has been sterilized as specified in the Ministry of Milk, etc. Ordinance ("Ministry of Health, Labor and Welfare Ordinance No. 52 of 1951") (which states that the milk should be sterilized by heating at 63°C for 30 minutes using a preservation method or a method having an equal or higher sterilization effect). The sterilization treatment methods include low temperature preservation sterilization (LTLT), continuous low temperature sterilization (LTLT), high temperature preservation sterilization (HTLT), high temperature short time sterilization (HTST), ultra high temperature instantaneous sterilization (UHT) and ultra high temperature sterilization (LL). 90% of the cow's milk sold in Japan is treated with UHT.

[0079] The raw milk mixture may be prepared using only the above-mentioned milk components, but may also be prepared by adding sugars (monosaccharides, disaccharides, oligosaccharides, polysaccharides and sugar alcohols) other than lactose derived from milk components to the above-mentioned milk components to an extent that does not impair the effects of the present invention.

[0080] The raw milk mixture may have the following composition:

[0081] (a) a fat content of 0.1 to 6.5% by mass, preferably 0.5 to 6% by mass, more preferably 1 to 4% by mass; a fat-free milk solids content of 8 to 16% by mass, preferably 8.5 to 15.5% by mass, more preferably 8 to less than 15% by mass; a carbohydrate content of 5 to 15% by mass, preferably 5 to 13% by mass, more preferably 5 to 12% by mass;

[0082] (b) the fat content is greater than 0.5% by mass and less than 4% by mass, preferably 1 to 3.5% by mass; the fat-free milk solids content is 15 to 16% by mass, preferably greater than 15% by mass and less than 16% by mass; the carbohydrate content is 5 to 10% by mass, preferably 7 to 9% by mass, and the carbohydrate is lactose derived from the raw milk, and preferably no other carbohydrates (externally added carbohydrates) are contained;

[0083] (c) The fat content is 0.5% by mass or less, preferably 0.1 to 0.5% by mass; the fat-free milk solids content is 15 to 16% by mass, preferably greater than 15% by mass and less than 16% by mass; and the carbohydrate content is 5 to 15% by mass, preferably 8 to 15% by mass.

[0084] The raw milk mixture can be prepared by further adding, in addition to the above-mentioned milk components and sugars, for example, lipids, proteins other than whey protein and casein, minerals (salts), vitamins, flavor components, spices, pigments, and other food additives to the extent that the effects of the present invention are not impaired. Although not strictly limited, it is preferred that the raw milk mixture targeted by the present invention does not contain any component belonging to the category of gelling agent, thickener, thickening stabilizer or stabilizer (for example, the stabilizer described in the background technology section of this specification, the β-glucan-containing substance described in PTL 1, and the modified starch described in PTL 2).

[0085] The raw material milk mixture of the present invention is a composition containing water and milk components. The proportion of water in the raw material milk mixture may be in the range of 75 to 90% by mass, preferably 78 to 89% by mass, and more preferably 81 to 88% by mass.

[0086] (2) Homogenization step

[0087] The step of homogenizing the raw milk mixture refers to finely crushing (micronizing) the particles composed of protein and / or lipid contained in the raw milk mixture. The homogenization method can follow the standard method; examples of the method used include, but are not limited to, stirring the raw milk mixture using equipment such as a mixer or a stirring blade, 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 method and equipment for homogenizing the raw milk are not limited to these methods, and any known method and equipment can be used. As described in the manufacturing example below, a preferred method is to pressurize and extrude the raw milk mixture through a narrow gap (homogenizer) while heating the raw milk mixture to about 70 to 90°C. The pressure and flow rate (flow rate) used for homogenization can be appropriately set as long as the average particle size of the raw milk can be adjusted to less than 0.8μm. For example, the homogenization pressure is 50 to 400kg / cm 2 , preferably 80 to 300 kg / cm 2, more preferably 120 to 200 kg / cm 2 Homogenization may be performed once or more than once. If homogenization is performed twice or more, it is preferred to set the homogenization so that the total homogenization pressure falls within the above range. The flow rate (flow rate) is not limited, but is 50 to 1000 kg / h, preferably 75 to 500 kg / h, and more preferably 100 to 200 kg / h.

[0088] (3) Pre-sterilization step

[0089] The step of sterilizing the raw milk mixture is performed to sterilize the raw milk mixture until the number of bacteria (excluding spores) contained in the raw milk mixture becomes less than 1000 cfu / ml. Any method and conditions capable of achieving this purpose can be used, such as a heat treatment method for sterilizing milk. Examples of heat treatment methods for sterilizing milk include: ultra-high temperature instantaneous sterilization (UHT sterilization) method, in which heating treatment is carried out at 120 to 150°C for 2 to 3 seconds; high temperature short time sterilization (HTST sterilization) method, in which heating treatment is continuously carried out at 72 to 75°C for more than 15 seconds; high temperature hold sterilization (HTLT sterilization) method, in which heating treatment is carried out at more than 75°C for more than 15 minutes in a hold mode; high temperature short time sterilization (HTST sterilization) method, in which heating treatment is continuously carried out at more than 72°C for more than 15 seconds; low temperature hold sterilization (LTLT sterilization) method, in which heating treatment is carried out at 63 to 65°C for 30 minutes in a hold mode; continuous low temperature sterilization (LTLT sterilization) method, in which heating treatment is continuously carried out at 65 to 68°C for more than 30 minutes; ultra-high temperature sterilization (LL sterilization) method, in which heating treatment is carried out at 135 to 150°C for 1 to 4 seconds.

[0090] The method is not limited to those described above, and any method may be used as long as the thermal history represented by heating temperature (product temperature) × heating time × pressure is equal to or greater than the thermal history of the above-mentioned heat treatment method. For example, the method used in the experimental example described later may also be adopted, in which the raw milk mixture is heated at a product temperature of 95° C. for 1 minute under normal pressure.

[0091] (4) Filling steps

[0092] As described above, the step of filling the raw milk mixture into the container can be performed before the raw milk mixture is fermented. For example, the step of filling the raw milk mixture into the container can be performed after the homogenization step and the pre-sterilization step, before or after the starter lactic acid bacteria are added to the raw milk mixture. The container filled with the raw milk mixture can be any container commonly used for making fermented milk (dairy products) by post-fermentation, and there is no particular restriction on the size (capacity), material or shape. For example, the container can be a size (capacity) for a single person for a single consumption, or for home 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 sealing properties; for example, the container can be a cup-shaped, brick-shaped packaging shape or a cheer pack shape. The method and equipment for filling the container can be a commonly used method and equipment.

[0093] (A) Fermentation Step

[0094] In the present invention, the fermentation step can be carried out by adding a starter lactic acid bacteria to the raw milk mixture and then fermenting the raw milk mixture in a container. The lactic acid bacteria used as a starter can be selected from one or more combinations of lactic acid bacteria commonly used in fermented milk manufacturing, such as: Lactobacillus bulgaricus (L.bulgaricus), Streptococcus thermophilus (S.thermophilus), Lactobacillus lactis (L.lactis), Lactobacillus gasseri (L.gasseri), Lactobacillus plantarum (L.plantarum), Lactobacillus casei (L.casei), Lactobacillus acidophilus (L.acidophilus) and Bifidobacterium. Preferably, the lactic acid bacteria is Lactobacillus bulgaricus. In addition, from the perspective of being standardized as a yogurt starter in the Food Code, a mixed starter of Lactobacillus bulgaricus and Streptococcus thermophilus can also be used.

[0095] The amount of the starter (lactic acid bacteria) 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, and 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 a starter to a raw milk mixture filled in a container, or a method of adding a starter online while the raw milk mixture flows through a pipeline and then filling the container with the mixture. The method and apparatus for adding a starter to a raw milk mixture are not limited to the above method, and any known method and apparatus can be used.

[0096] The fermentation of the raw milk mixture can be performed by adding a starter (lactic acid bacteria) and then allowing the mixture filled in the container to stand in a fermentation chamber set at a predetermined temperature. The conditions for fermenting the raw milk mixture are adjusted in consideration of the type and amount of lactic acid bacteria etc. added to the raw milk and the flavor, texture, physical properties, etc. of the fermented milk to be actually obtained.

[0097] For example, the lower limit of the temperature (fermentation temperature) at which the raw milk mixture is fermented is preferably 35°C or higher, more preferably 37°C or higher. The upper limit of the temperature at which the raw milk is fermented is preferably 50°C or lower, more preferably 45°C or lower. Particularly preferably, it is 37 to 43°C. A low fermentation temperature is likely to result in a decrease in the hardness of the sterilized fermented milk obtained. Therefore, the hardness of the sterilized fermented milk can be appropriately adjusted by adjusting the fermentation temperature.

[0098] The time for fermenting the raw milk (fermentation time) is the time until the pH of the fermented milk falls within the range of 3.8 to 5.4. In other words, the fermentation ends when the pH of the fermented milk reaches a certain point within the range of 3.8 to 5.4. The pH at the end of the fermentation can be set as follows depending on the composition of the raw milk mixture used:

[0099] (a) for a raw milk mixture comprising 0.1 to 6.5 mass%, preferably 0.5 to 6 mass%, more preferably 1 to 4 mass% of fat, 8 to 16 mass%, preferably 8.5 to 15.5 mass%, more preferably 8 to less than 15 mass% of fat-free milk solids, and 5 to 15 mass%, preferably 5 to 13 mass%, more preferably 5 to 12 mass% of sugars: pH at the end of fermentation is 4.5 to 5.4, preferably 4.5 to 5.2, more preferably 4.5 to 5.0;

[0100] (b) for a raw milk mixture containing more than 0.5% by mass and less than 4% by mass, preferably 1 to 3.5% by mass of fat, 15 to 16% by mass, preferably more than 15% by mass and less than 16% by mass of fat-free milk solids, and 5 to 10% by mass, preferably 7 to 9% by mass of sugars (wherein the sugars are lactose derived from the raw milk, and preferably no other sugars (externally added sugars) are contained): the pH at the end of fermentation is 3.8 to less than 4.5, preferably 4.0 to 4.4; and

[0101] (c) For a raw milk mixture containing 0.5% by mass or less, preferably 0.1 to 0.5% by mass, fat, 15 to 16% by mass, preferably more than 15% by mass and less than 16% by mass of fat-free milk solids, and 5 to 15% by mass, preferably 8 to 15% by mass of sugars: the pH at the end of fermentation is 3.8 to less than 4.5, preferably 4.0 to 4.4.

[0102] When a raw material milk mixture having any of the following compositions is used, it is preferred to adjust the fermentation time so that the pH of the fermented milk does not fall within the range of 4.7 to 5.4, but preferably falls within the range of 3.8 to 4.5:

[0103] (d) a raw milk mixture containing 15% by mass or more of fat-free milk solids and 0.5% by mass or less of fat; and

[0104] (e) A raw milk mixture comprising 15% by mass or more of fat-free milk solids and more than 0.5% by mass and less than 4% by mass of fat, and containing no sugars (externally added sugars) derived from the raw milk other than lactose.

[0105] The pH at the end of fermentation is adjusted according to the composition of the raw milk mixture so as to fall within the above range; this provides coagulated sterilized fermented milk showing suppressed milk protein aggregation (which is one of the effects of the present invention) and good texture (no graininess and good taste). The method and apparatus for fermenting the raw milk mixture may be any known method and apparatus.

[0106] (B) Heating step

[0107] The heating step is a step of heating the fermented milk that has reached a predetermined pH in the fermentation step while the fermented milk is filled in a container. This step is performed to kill the lactic acid bacteria added to the raw milk mixture as a starter to prevent the fermentation process and to kill the bacteria to ensure the hygienic safety and shelf life of the food.

[0108] The heat treatment can be carried out according to any method under any conditions that can achieve this purpose. A heat treatment method in which the heat history represented by the heating temperature (product temperature) × heating time × pressure is equal to or greater than 75°C × 15 minutes × normal pressure can be used. A heat history of 75°C × 15 minutes × normal pressure means that after the product temperature reaches 75°C at normal pressure, the product is heated for 15 minutes under the same temperature conditions. An example of a heat treatment method that achieves a heat history equal to or greater than 75°C × 15 minutes × normal pressure is to immerse the product in 85°C hot water for 60 minutes at normal pressure. Note that the normal pressure used in this article means a pressure state in which the pressure inside the container is normal pressure, and does not include a pressure state in which artificial pressure is increased or reduced. The heat treatment can be carried out after the fermented milk filled into the container is packaged and sealed. Alternatively, the fermented milk filled into the container can be heat treated before sealing and packaging, and then sealed and packaged. Any known method and equipment can be used to heat the fermented milk with its container.

[0109] After cooling, the sterilized fermented milk thus manufactured can be directly distributed in the market in a state of being filled, sealed and packaged in a container. As described in the following examples, the sterilized fermented milk obtained according to the manufacturing method of the present invention shows that the aggregation of milk protein is suppressed and has a good texture (no graininess and pleasant taste). Therefore, the manufacturing method of the present invention can provide a solid coagulated sterilized fermented milk that overcomes the previous problems.

[0110] In the present specification, the terms “comprise” and “contain” include the meanings of “consisting of” and “consisting essentially of”.

[0111] Example

[0112] The present invention is described with reference to experimental examples to help understand the composition and effects of the present invention. However, the present invention is not limited by these experimental examples in any way. Unless otherwise stated, the following experiments are carried out at room temperature (25 ± 5 ° C) and atmospheric pressure (normal pressure). Unless otherwise stated, the unit "%" hereinafter means mass %, and the unit "part" hereinafter means mass part.

[0113] The raw materials used in the following preparation examples (embodiments and comparative examples) are as follows:

[0114] raw material

[0115] Cream: manufactured by Meiji Co., Ltd. (milk fat: 47%)

[0116] Milk (UHT sterilized and homogenized): manufactured by Meiji Co., Ltd.

[0117] Skim milk powder: manufactured by Meiji Co., Ltd. (Fat-free milk solids: 96%, lactose: 55%)

[0118] High-heat skim milk powder: manufactured by Meiji Co., Ltd. (Fat-free milk solids: 96%, lactose: 55%)

[0119] Whey protein isolate (WPI): WPI895 (whey protein: 93.5%), Fonterra, Japan Gelatin: M-200C gelatin (manufactured by Nitta Gelatin Inc.)

[0120] 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.)

[0121] Manufacturing example

[0122] (1) Embodiment 1

[0123] 157 g of cream, 231 g of skim milk powder and 2037 g of water were mixed to prepare raw milk (externally added sugar: 0%, stabilizer: 0%). The raw milk was heated to about 70°C and then homogenized at a flow rate of 150 L / h (100 kg / cm 2 +50kg / cm 2 ) is homogenized and sterilized by heating at 95°C for 5 minutes to prepare a raw milk mixture. The obtained raw milk mixture is cooled to 43°C, and a lactic acid bacteria starter is added (inoculated) at a ratio of 3%. Subsequently, the mixture is poured into a cup-shaped container (capacity: 100g, made of plastic) and allowed to stand in a fermentation room (43°C) for 4 hours to allow the fermentation to proceed until the pH reaches 4.6, after which the mixture is cooled in a refrigerator (below 10°C). Thereafter, the cup-shaped container is immersed in hot water at 85°C for 1 hour, and then immersed in ice-cold water for 30 minutes, thereby obtaining a solid coagulated sterilized fermented milk (Example 1).

[0124] (2) Embodiment 2

[0125] Solid coagulated sterilized fermented milk (Example 2) was produced in the same manner as in Example 1 except that a composition (fat content: 0%, stabilizer: 0%) prepared by mixing 238 g of skim milk powder, 150 g of granulated sugar and 2038 g of water was used as the raw milk.

[0126] (3) Embodiment 3

[0127] Solid coagulated sterilized fermented milk (Example 3) is manufactured in the same manner as Example 1, except that a composition prepared by mixing 157 g of cream, 231 g of skim milk powder, 150 g of sugar and 1887 g of water (containing fat and externally added sugars, without stabilizer (0%)) is used as the raw milk.

[0128] (4) Embodiment 4

[0129] Solid coagulated sterilized fermented milk (Example 4) is manufactured in the same manner as Example 1, except that a composition prepared by mixing 315 g of cream, 223 g of skim milk powder, 150 g of granulated sugar and 1738 g of water (containing fat and externally added sugars, without stabilizer (0%)) is used as the raw milk.

[0130] (5) Embodiment 5

[0131] Solid coagulated sterilized fermented milk (Example 5) is manufactured in the same manner as Example 1, except that a composition prepared by mixing 154 g of cream, 379 g of skim milk powder, 150 g of sugar and 1743 g of water (containing fat and externally added sugars, without stabilizer (0%)) is used as the raw milk.

[0132] (6) Examples 6 to 8

[0133] Using the raw milk with the same recipe as in Example 3 (containing fat and externally added sugars, without stabilizer (0%)), except that the homogenization pressure used in the homogenization and the temperature used in the fermentation treatment are as described in Table 1, solid coagulated sterilized fermented milk (Examples 6 to 8) was obtained according to the method and conditions described in Example 1.

[0134] (7) Examples 9 to 12

[0135] Using the raw milk with the same recipe as in Example 3 (containing fat and externally added sugars, without stabilizer (0%)), solid coagulated sterilized fermented milk (Examples 9 to 12) was manufactured according to the same method as in Example 1 under the same conditions, except that the pH at the end of fermentation was set as shown in Table 1.

[0136] (8) Examples 13 and 14

[0137] Using the raw milk with the same recipe as in Example 1 (externally added sugars: 0%, stabilizer: 0%), solid coagulated sterilized fermented milk (Examples 13 and 14) was manufactured under the same conditions according to the same method as in Example 1, except that the pH at the end of fermentation was set as shown in Table 1.

[0138] (9) Embodiment 15

[0139] A raw milk (externally added sugars: 0%, stabilizer: 0%) consisting of cow's milk (UHT sterilized and homogenized), high-heat skimmed milk powder (replacing cream and skimmed milk powder) and water is prepared to have the same formula as in Example 1, and a solid coagulated sterilized fermented milk (Example 15) is obtained according to the same method and under the same conditions as in Example 1.

[0140] (10) Embodiment 16

[0141] A raw milk (externally added sugars: 0%, stabilizer: 0%) consisting of cow's milk (UHT sterilized and homogenized), high-heat skimmed milk powder (replacing cream and skimmed milk powder) and water was prepared to have the same recipe as in Example 1, except that the fermentation temperature was as shown in Table 1, and solid coagulated sterilized fermented milk (Example 16) was obtained under the same conditions as in Example 15 according to the same method.

[0142] (11) Comparative Examples 1 to 6

[0143] Using the raw milk with the same recipe as in Example 1 (externally added sugars: 0%, stabilizer: 0%), except that the pH at the end of fermentation was set as shown in Table 2, solid coagulated sterilized fermented milk (Comparison Examples 1 to 6) was obtained in the same manner as in Example 1 under the same conditions.

[0144] Table 1 shows the composition of the raw milk of Examples 1 to 16 (the ratio of fat, fat-free milk solids, lactose, externally added sugars and the total amount of sugars) and the manufacturing conditions (homogenization pressure, fermentation temperature and pH at the end of fermentation), and Table 2 shows the composition and manufacturing conditions of the raw milk of Comparative Examples 1 to 6.

[0145] Table 1

[0146]

[0147]

[0148] Table 2

[0149]

[0150] Experimental example

[0151] The sterilized fermented milks of Examples 1 to 16 and Comparative Examples 1 to 6 produced in the above-mentioned production examples were evaluated for curd tension (hardness), particle size after stirring, centrifugal syneresis, and texture (smoothness) according to the following methods.

[0152] (A) Curd tension (hardness)

[0153] The sterilized fermented milk of Examples 1 to 16 and Comparative Examples 1 to 6 was immersed in 85° C. hot water for 1 hour in the above-mentioned manufacturing step and then immersed in ice-cooled water for 30 minutes to adjust the product temperature to 5° C., and then its curd tension (hardness) was measured using a MAX ME-500 curd meter (manufactured by I. Techno Engineering).

[0154] Specifically, a yogurt knife with a 100g weight is placed on the top surface of the test sample (sterilized fermented milk), so that the test sample continues to rise, while applying a load of about 2g / second. The measured load is plotted into a curve according to the time of applying the load. At this time, the time (seconds) of applying the load is plotted on the vertical axis, and the measured load value is plotted on the horizontal axis, where the 10g on the vertical axis is the same as the 4 seconds on the horizontal axis. When the test sample breaks, an inflection point (rupture point) will appear on the time-weighted curve due to the yogurt knife piercing the top surface of the test sample. The load applied until the curd breaks is defined as the curd tension (g).

[0155] (B) Particle size after stirring

[0156] The sterilized fermented milks of Examples 1 to 16 and Comparative Examples 1 to 6 in a cup-shaped container were immersed in hot water at 85° C. for 1 hour together with the cup-shaped container in the above-mentioned manufacturing step, and then immersed in ice-cooled water for 30 minutes to adjust the product temperature to 5° C. Thereafter, the sterilized fermented milk was subjected to the stirring treatment described below, and the particle size of the resulting stirred product was measured using a SALD-2200 laser diffraction particle size distribution analyzer (manufactured by Shimadzu Corporation).

[0157] Mixing treatment

[0158] 500 g of sterilized fermented milk (test sample) was placed in a cylindrical stainless steel tray (bottom area: 123 cm 2 ), and stirred at 150 rpm for 1 minute at room temperature (25° C.) using a stirrer (Three-One Motor FBLh1200M: manufactured by Shinto Scientific Co., Ltd., blade shape: T-shape, blade radius: 6 cm).

[0159] Particle size measurement method

[0160] The average particle size and standard deviation of the sterilized fermented milk of Examples 1 to 16 and Comparative Examples 1 to 6 were measured using a SALD-2200 laser diffraction particle size distribution analyzer (manufactured by Shimadzu Corporation). Specifically, the sterilized fermented milk was diluted with ion exchange water so that the maximum value of the diffraction and scattered light intensity distribution was 35 to 75%. The light intensity distribution was then analyzed using WingSALD II software for a particle size distribution analyzer to determine the average particle size ± standard deviation.

[0161] (C) Centrifugal syneresis

[0162] The sterilized fermented milks of Examples 1 to 16 and Comparative Examples 1 to 6 in a cup-shaped container were immersed in hot water at 85° C. for 1 hour together with the cup-shaped container in the above-mentioned manufacturing step, and then immersed in ice-cooled water for 30 minutes to adjust the product temperature to 5° C. Thereafter, the sterilized fermented milk was subjected to the following centrifugal treatment, and the resulting centrifuged product was measured according to the measurement method described below to calculate the syneresis amount (%).

[0163] Centrifugation

[0164] 40 g of the sterilized fermented milk (product temperature: 5° C.) of Examples 1 to 16 and Comparative Examples 1 to 6 was weighed and placed in a centrifuge tube, which was then centrifuged at 3000 rpm at 5° C. for 10 minutes using an LCX-100 centrifuge (Tomy Sieko Co., Ltd.).

[0165] Method for measuring syneresis

[0166] After centrifugation, the weight of the liquid separated into the upper layer of the centrifuged product was measured, and the syneresis amount (%) was calculated using the following formula.

[0167] Syneresis (%) = weight of separated liquid (g) / 40 (g) × 100

[0168] (D) Texture (smoothness)

[0169] The sterilized fermented milk of Examples 1 to 16 and Comparative Examples 1 to 6 was immersed in 85°C hot water for 1 hour in the above-mentioned manufacturing steps, and then immersed in ice-cold water for 30 minutes to adjust the product temperature to 5°C, after which five expert panels tasted each dairy product and evaluated its texture (smoothness).

[0170] The expert panel consisted of experts who participated in the development of fermented milk and who routinely evaluated the texture of solid coagulated fermented milk. Each expert put 10 g of the sterilized fermented milk of each example into the mouth at one time, and evaluated the smoothness based on the mouthfeel and whether the tongue felt the granular feeling. If the fermented milk felt that the fermented milk disintegrated smoothly when it was put into the mouth and in contact with the tongue, the mouthfeel was evaluated as "good mouthfeel"; if the fermented milk still had some granules remaining when it was put into the mouth and in contact with the tongue, it was evaluated as "bad mouthfeel".

[0171] Each expert tasted one pasteurized fermented milk sample three times to check the mouthfeel and the presence or absence of graininess. The results from each expert were collected and discussed among them, and a comprehensive evaluation was performed based on the following criteria.

[0172] Comprehensive evaluation

[0173] ○: Throughout the three tastings, the mouthfeel was generally good with no graininess (smooth texture).

[0174] Δ: Throughout the three tastings, the taste was generally good, but there was a slight graininess.

[0175] ×: Throughout the three tastings, regardless of the taste, there is an obvious grainy feeling overall, or there is no grainy feeling but the taste is bad.

[0176] Table 3 shows the evaluation results of Examples 1 to 16, and Table 4 shows the evaluation results of Comparative Examples 1 to 6. Figure 1A graph showing the textures (○, ×) of Examples 1 to 16 and Comparative Examples 1 to 6 is plotted with curd tension (g) on ​​the horizontal axis and particle size after stirring (μm) on the vertical axis.

[0177] Table 3

[0178]

[0179] Table 4

[0180]

[0181] like Figure 1 As shown, the sterilized fermented milk of Examples 1 to 16 has a curd tension and a particle size after stirring within a predetermined range, and is therefore confirmed to have a good texture. Specifically, unlike the sterilized fermented milk of Comparative Examples 1 to 6, the curd tension (X) of the sterilized fermented milk of Examples 1 to 16 is in the range of 20 to 220 g, preferably 35 to 180 g, and more preferably 40 to 175 g; the particle size after stirring (Y) is in the range of 166.5 to 2.5 μm, preferably 150 to 30 μm, and more preferably 145 to 35 μm; and the curd tension (X) and the particle size after stirring (Y) are in the range represented by the following formula, thereby showing a smooth and good texture: Y≤-0.82X+183.

[0182] Furthermore, compared with Comparative Examples 1 to 6, most of the sterilized fermented milks of Examples 1 to 16 showed less centrifugal syneresis.

[0183] Industrial Applicability

[0184] At present, the market of sterilized fermented milk is expanding not only in Japan but also overseas (especially China). Since sterilized fermented milk has a longer shelf life, it can be sold in a less developed distribution environment compared with ordinary fermented milk, and the requirements for the refrigeration facilities of retailers can also be relaxed. In addition, sterilized fermented milk can have a long tasting period, which makes the production plan more flexible and reduces food waste. However, the dosage form of existing sterilized fermented milk is limited to yogurt drinks and soft yogurt, and there is no solid coagulation type sterilized fermented milk. The present invention can provide a solid sterilized fermented milk, which can bring benefits such as opening up new markets, improving productivity and reducing environmental burden.

Claims

1. A coagulated sterilized fermented milk, wherein the coagulation tension (X) and the particle size after stirring (Y) satisfy the following conditions: The curd tension (X) is 20g to 220g, The particle size (Y) after stirring is 166.5 μm to 2.5 μm, and Y≤-0.82X+183. 2 . The sterilized fermented milk according to claim 1 , wherein the curd tension (X) is 35 g or more.

3. The sterilized fermented milk according to claim 1 or 2, comprising 6% by mass or less of fat and 8 to 16% by mass of fat-free milk solids, and having a pH of 3.8 to 5.4, The condition is that the pH of the sterilized fermented milk containing 15% by mass or more of fat-free milk solids and 0.5% by mass or less of fat or the sterilized fermented milk containing 15% by mass or more of fat-free milk solids and no externally added sugar is 3.8 to 4.

5. The sterilized fermented milk according to claim 3, comprising 15% by mass or less of sugars.

5. A method for producing sterilized fermented milk according to any one of claims 1 to 4, comprising the following steps: The raw milk mixture to which lactic acid bacteria are added is fermented in a container at 37°C to 43°C until the pH reaches 3.8 to 5.4, and The obtained fermented milk is heated together with the container. 6 . The production method according to claim 5 , wherein the raw milk mixture is homogenized and sterilized before adding lactic acid bacteria.

7. The manufacturing method according to claim 5 or 6, wherein the raw milk mixture contains 6% by mass or less of fat and 8 to 16% by mass of fat-free milk solids, The conditions are: When the raw milk mixture contains 15% by mass or more of fat-free milk solids and 0.5% by mass or less of fat, or when the raw milk mixture contains 15% by mass or more of fat-free milk solids and contains no externally added sugars, the raw milk mixture is fermented until the pH reaches 3.8 to 4.

5. 8 . The production method according to claim 7 , wherein the raw material milk mixture contains 15% by mass or less of sugars.

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