WO2024058230A1 - Sterilized fermented milk and production method for same - Google Patents

Abstract

The present invention provides a set-type sterilized fermented milk and a production method therefor. This set-type sterilized fermented milk is characterized: by including 1.5–3.0 mass% of whey protein and 2.0–3.0 mass% of casein protein, there being 50–125 parts by mass of whey protein per 100 parts by mass of casein protein; and by having a pH of 5.3–5.9.

Description

Sterilized fermented milk and its manufacturing method REFERENCE TO RELATED APPLICATIONS

This application claims priority based on Japanese Patent Application No. 2022-146607, which was filed on September 14, 2022, and the entire disclosure content of this Japanese application is hereby incorporated by reference. be part of the disclosure.

The present invention relates to a set-type sterilized fermented milk and a method for producing the same. More specifically, the present invention relates to a set-type sterilized fermented milk that is filled into a container, fermented (post-fermented), and solidified in the container, and a method for producing the same.

Amid health-consciousness, consumer interest in fermented milk is increasing, and if fermented milk becomes applicable to more types of cooking, it is expected that opportunities to consume it will further increase. However, fermented milk has a strong sour taste and weak shape retention properties, so in reality, it is eaten as is, spread on vegetables, meat, and other ingredients as a dip, or used as a part of the ingredients when cooking. The main way to eat it is by mixing it with other ingredients.

If you just want to improve the shape retention of fermented milk, you can solidify it by making it a highly concentrated composition or by adding a gelling agent or thickening polysaccharide, but if you cook it, it will collapse or become more dense than necessary. Problems such as hardening occur. Another problem is that when heated to high temperatures, a strong sour taste occurs. On the other hand, when the pH is increased to suppress sourness, shape retention is extremely reduced, so to compensate for this, it is necessary to use a highly concentrated composition or use a gelling agent or polysaccharide thickener. There is a problem that the flavor and texture are impaired. In order to make fermented milk more widely used in cooking, it is necessary to improve its taste and physical properties, such as preventing it from collapsing during cooking, while suppressing acidity.

No prior art documents were found that disclose fermented milk that does not boil apart while suppressing acidity without using gelling agents or thickening polysaccharides, and a method for producing the same.

Patent Documents 1 and 2 are prior art documents that disclose a technique common to the production method of the present invention in that heat treatment (secondary heat treatment) is performed after post-fermentation. However, Patent Document 1 is characterized in that a β-glucan-containing material (Aureobasidium culture solution) is added as a stabilizer after fermentation and then heat treated, and further, after the heat treatment, the mixture is homogenized and liquefied. This differs from the present invention in that it is not a set type sterilized fermented milk. Further, Patent Document 2 is different from the present invention in that it is characterized by blending cross-linked processed starch as a material and is directed to soft or drinkable yogurt prepared by crushing curd after fermentation. .

Japanese Patent Application Publication No. 2005-137245 JP2017-63727A

The objective of the present invention is to provide a set type pasteurized fermented milk that has a reduced sour taste and does not easily fall apart when cooked with heat, and a method for producing the same.

The present inventors have conducted intensive studies to produce a set-type fermented milk that solves the above-mentioned problems, and found that the content of whey protein is 1.5-3.0% by mass and casein protein is 2.0-3.0% by mass. Add lactic acid bacteria to a raw milk mix containing a specific proportion of 3.0% by mass, and ferment in a container until the pH reaches 5.3 to 5.9. It has been found that a set-type sterilized fermented milk having the desired characteristics (low acidity, resistance to boiling) can be obtained by heat treatment to achieve the above thermal history.

The present invention was completed based on this knowledge, and includes the following embodiments.

(I) Set type sterilized fermented milk (I-1) Contains 1.5 to 3.0% by mass of whey protein and 2.0 to 3.0% by mass of casein protein, and contains 100 parts by mass of casein protein. A set type sterilized fermented milk with a pH of 5.3 to 5.9 and a whey protein ratio of 50 to 125 parts by mass.
(I-2) The sterilized fermented milk described in (I-1), which has a non-fat milk solids content of 9.5 to 11.2% by mass.
(I-3) The sterilized fermented milk described in (I-1) or (I-2), which has shape retention and/or resistance to boiling.
(I-4) The sterilized fermented milk according to any one of (I-1) to (I-3), in which the maximum load at break is 5.0 to 8.0 N in a break test using a plunger. .

(II) Method for producing set type sterilized fermented milk (II-1) (a) Whey protein content is 1.5 to 3.0% by mass, and casein protein content is 2.0 to 3.0% by mass. , a step of adding lactic acid bacteria to a raw milk mix in which the ratio of whey protein to 100 parts of casein protein is 50 to 125 parts by mass, and fermenting it in a container until the pH reaches 5.3 to 5.9; (b) Production of a set-type sterilized fermented milk, which includes the step of heat-treating the obtained fermented milk in a container so that its thermal history becomes at least 75°C x 15 minutes x normal pressure. Method.
(II-2) The production method according to (II-1), wherein the non-fat milk solid content of the raw milk mix is 9.5 to 11.2% by mass.
(II-3) The production method described in (II-1) or (II-2), wherein the raw milk mix is subjected to homogenization treatment and sterilization treatment before adding lactic acid bacteria.
The manufacturing method can also be restated as follows:
“Before the step (a) above, the whey protein content is 1.5 to 3.0% by mass, the casein protein content is 2.0 to 3.0% by mass, and the ratio of whey protein to 100 parts by mass of casein protein is The manufacturing method described in (II-1) or (II-2), which comprises the steps of homogenizing and sterilizing 50 to 125 parts by mass of the raw milk mix.
(II-4) The production method according to any one of (II-1) to (II-3), wherein the fermentation temperature is 35 to 48°C.

The sterilized fermented milk of the present invention and the sterilized fermented milk obtained by the production method of the present invention have a pH higher at 5.3 to 5.9 compared to normal fermented milk, which has a pH of about 4.6. , the acidity is moderated. Therefore, it is easy to eat and can be combined with many ingredients.

In addition, the sterilized fermented milk of the present invention and the sterilized fermented milk obtained by the production method of the present invention have good shape retention and do not easily collapse even when boiled, so they can be used regardless of whether they are heated or not. Easy to use for various cooking. In addition, when boiling sterilized fermented milk, the broth does not become cloudy, so there is less loss of nutritional components during cooking, and the appearance of the dish does not deteriorate.

Furthermore, the sterilized fermented milk of the present invention and the sterilized fermented milk obtained by the production method of the present invention are appropriately adjusted from a hardness and/or texture equivalent to that of silken tofu to a hardness and/or texture equivalent to that of firm tofu. Therefore, it can be used in place of tofu used in widely commonly eaten tofu dishes (boiled tofu, hot pot dishes, soup ingredients, tofu steak, chilled yakko, mapo tofu, etc.). This can expand the cooking uses of fermented milk and increase opportunities for consumers to eat fermented milk, which is a healthy food.

Images of the broths (in beakers) of Comparative Examples 24 and 25 and Examples 5 and 6 that were subjected to the broth turbidity test in Experimental Example 2. From 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) ).

(I) Set type sterilized fermented milk Fermented milk is manufactured by the Ministry of Health, Labor and Welfare Ordinance No. 52 of 1952, revised on January 9, 2015: Ministry of Health, Labor and Welfare of Japan. (hereinafter referred to as the ``Milk Ministerial Ordinance''), ``Milk or milk containing an equivalent or higher non-fat milk solid content is fermented with lactic acid bacteria or yeast and made into a paste or liquid, or frozen. The non-fat milk solids content is determined to be 8.0% or more.These fermented milks are made by (a) filling the raw milk into a container and then fermenting it; (b) Crushing the solid fermented milk solidified in a large tank (this is called "set type fermented milk" or "post-fermented fermented milk") and (b) the curd formed after fermentation in a large tank, etc. (c) paste-like fermented milk filled in a container after mixing with fruit pulp, sauce, etc. (this is referred to as "soft yogurt" or "pre-fermented fermented milk"); Fermented milk in the form of fermented milk or paste-like fermented milk is finely crushed and liquefied using a homogenizer, etc., and mixed with pulp, sauce, etc. as necessary, and then filled into a container to form liquid fermented milk (this is It is broadly divided into ``drinking yogurt.''

Among these fermented milks, the fermented milk targeted by the present invention is a set type fermented milk (solid form) that is post-fermented using lactic acid bacteria. Furthermore, the fermented milk targeted by the present invention is sterilized fermented milk that is sterilized by heat treatment after fermentation (referred to as "sterilized fermented milk"). Specifically, it is defined in the Milk Ministerial Ordinance as ``fermented milk that is manufactured by fermenting and then heating it at 75℃ for 15 minutes or more, or by heating and sterilizing it by a method that has an equivalent or higher sterilization effect.'' be.

The sterilized fermented milk of the present invention contains whey protein at a ratio of 1.5 to 3.0 mass % and casein protein at a ratio of 2.0 to 3.0 mass % per 100 mass % of sterilized fermented milk. It is characterized in that the ratio of whey protein (solid content mass ratio) to 100 parts by mass is 50 to 125 parts by mass.
Here, the content of whey protein and casein protein means the solid content of each protein contained in 100% by mass (wet mass) of sterilized fermented milk (in terms of solid content).

Whey protein is a mixture of proteins found in whey, the liquid portion of milk after the casein and fat have been removed. Proteins constituting whey protein include β-lactoglobulin, α-lactalbumin, immunoglobulin, bovine serum albumin, lactoferrin, lactoperoxidase, proteose peptone, and the like. It is said that about 20% by mass of milk proteins contained in milk is whey protein.
Casein protein (commonly referred to as "casein") is a milk protein that is present in approximately 80% of milk and is derived from α _s1 -casein, α _s2 -casein, β-casein, and κ-casein. It is a complex protein.

The content of casein protein and whey protein contained in sterilized fermented milk (sample) can be measured by the following method.
[Casein protein]
Add 90 ml of water to 10 g of sample and warm to about 40-42°C, add 1.5 ml of 10% by mass acetic acid aqueous solution, stir, and leave to stand for 5 minutes, then remove the precipitate (casein) from filter paper. Filter. The precipitate (residue) remaining on the filter paper is washed with water that has been made acidic (pH 4.6) with acetic acid, and the residue is quantified with the filter paper by the combustion method or Kjeldahl method, and this is converted into nitrogen protein. Calculated by multiplying by a coefficient.
[Whey protein]
It is calculated by quantifying the total protein contained in the sample by the combustion method or Kjeldahl method, and then subtracting the amount of casein protein obtained by the above method.

The whey protein content (in terms of solid content) in 100% by mass (wet mass) of sterilized fermented milk is not limited as described above, but is preferably 1.5 to 3.0% by mass, more preferably 1.5% by mass. It is 7 to 2.5% by mass. Further, the casein protein content (in terms of solid content) is not limited as described above, but is preferably 2.3 to 3.0% by mass, more preferably 2.5 to 3.0% by mass. Further, the ratio of whey protein to 100 parts by mass of casein protein (solid content mass ratio) is not limited as described above, but is preferably 50 to 120 parts by mass, more preferably 62 to 100 parts by mass.

The content of non-fat milk solids in the sterilized fermented milk of the present invention is 8% by mass or more based on the standards for fermented milk. It is preferably 9 to 12% by weight, more preferably 9.5 to 11.2% by weight.

Although the sterilized fermented milk of the present invention is not limited, the proportion of milk fat is 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; The proportion of lactose is 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; The proportion can range from 0 to 10% by weight, preferably from 2.5 to 7.5% by weight, more preferably from 4 to 6% by weight.

The types of carbohydrates other than lactose are not limited, but include monosaccharides (e.g., glucose, fructose, galactose, etc.), disaccharides (e.g., sucrose, maltose, lactose, trehalose, etc.), oligosaccharides (e.g., sucrose, maltose, lactose, trehalose, etc.), For example, fructooligosaccharides, soybean oligosaccharides, raffinose (beet oligosaccharides), galactooligosaccharides, and isomaltooligosaccharides), polysaccharides (e.g., EPS (exopolysaccharides), pectin, etc.), and sugar alcohols (e.g., xylitol). , sorbitol, maltitol, etc.).

The sterilized fermented milk of the present invention is characterized by a pH of 5.3 to 5.9, which is higher than the pH of normal fermented milk (about 4.6). For this reason, it has a lower sourness than normal fermented milk. More preferably, the pH is 5.4 to 5.8.

The sterilized fermented milk of the present invention is characterized by having a solid state and having shape retention properties. The presence or absence of shape retention is determined by taking out the target sterilized fermented milk from a cylindrical (diameter 7 cm) cup-shaped container (filling capacity 100 g) and placing it on a flat plate such as a plate, as described in the experimental example below. Judgment can be made by whether the shape of the cup is maintained without collapsing even under its own weight when left for 60 minutes at a product temperature (25℃), and if the shape is maintained without collapsing. can be evaluated as having "shape retention".
Note that "the shape is maintained without collapsing" means not only that the cup shape is maintained as it is, but also that the corners (edges) are maintained even if the cup shape is slightly sunken downward. This also includes cases where the flow is maintained without collapsing.

The sterilized fermented milk of the present invention is characterized by being resistant to boiling. To determine whether or not the sterilized fermented milk is resistant to boiling, remove the target sterilized fermented milk from a cup-shaped container (filling capacity: 100 g), immerse it in 10 times the volume of boiling water (80°C) for 10 minutes (static immersion), and then It can be determined by comparing the shape (cup shape) and whether or not the shape is distorted. As described in the experimental examples described below, if the shape remains unchanged even after immersion, it can be evaluated as "resistant to boiling." Here, the meaning of "the shape has not collapsed" includes not only the case where the cup shape before immersion is maintained as it is, but also the case where the cup shape is in a loose state (swelled state) as a whole. This also includes cases where the corners (edges) can be maintained without collapsing even if there is a problem. More preferably, the residual liquid (boiled liquid) obtained from the sterilized fermented milk after the boiling resistance test is passed through a 60# filter, and the permeated liquid is transparent, and the 200P TURBIDIMETER (HACH The turbidity is less than 5 NUT when measured using

In addition, the sterilized fermented milk of the present invention may have a hardness similar to silken tofu (equal to or similar to silken tofu), a hardness similar to silken tofu (equal to or similar to cotton tofu), or a hardness of silken tofu and firm tofu, although it is not limited thereto. It is preferable that the hardness is between . This hardness can be evaluated by eating and comparing the sterilized fermented milk, silken tofu, and cotton tofu of the present invention at the same temperature (for example, 10° C.).
Alternatively, evaluation can be made by comparing the maximum load (N) measured in a breaking test using a creep meter (for example, manufactured by Leonor II Co., Ltd., Yamaden Co., Ltd.) with silken tofu or firm tofu. can. Specifically, as described in the experimental example below, a disk-shaped plunger was lowered from above onto the surface of sterilized fermented milk (test sample) (product temperature 25°C) placed in a cup container, and a load was applied to compress the milk. Measure the curve and determine the maximum value of the load (maximum load (N)) until the test sample breaks. When measured under the conditions described in the experimental examples described below, the sterilized fermented milk of the present invention preferably has a maximum load in the range of 5.00 to 8.00N. The range is more preferably 5.10 to 7.00N, and even more preferably 5.10 to 6.50N.

Further, although not limited to, the sterilized fermented milk of the present invention has a smooth texture similar to silken tofu (equal to or similar to silken tofu); It is preferable that it has a slightly rough texture similar to tofu (equivalent to or similar to firm tofu), or a texture between silken tofu and firm tofu. More preferably, it has a texture between silken tofu and firm tofu. As described in the experimental examples below, the texture was evaluated by a specialized panel trained in sensory evaluation using commercially available regular silken tofu and firm tofu, whose temperature was adjusted to 10°C, as controls 1 and 2, respectively. Compare the texture of the sterilized fermented milk of the invention (test sample) (product temperature 10°C) with the texture of Controls 1 and 2, and evaluate whether the degree of smoothness and roughness felt by the tongue is the same or different. be able to.

(II) Method for producing set type sterilized fermented milk The sterilized fermented milk of the present invention described above can be produced by a method comprising the following steps (a) and (b):
(a) The whey protein content in the raw milk mix (100 wet mass %) is 1.5 to 3.0 mass % in solid content, and the casein protein content is 2.0 to 3.0 mass % in solid content. Lactic acid bacteria are added to a raw milk mix in which the ratio of whey protein to 100 parts by mass of casein protein (solid content mass ratio) is 50 to 125 parts by mass, and the pH is adjusted to 5.3 to 5.5 in a container. 9 (hereinafter referred to as "step (a)" or "fermentation step"), and (b) the obtained fermented milk is placed in a container with a thermal history of 75°C. A step of heating for 15 minutes or more (hereinafter, this is referred to as "step (b)" or "heating step").

The manufacturing process of the present invention described above includes, before the step (a), (1) a step of preparing a raw milk mix (raw milk mix preparation step), (2) a step of homogenizing the raw milk mix (homogenization). and (3) a step of sterilizing the raw milk mix (pre-sterilization step). These are called pretreatment steps. Among these pretreatment steps, (2) homogenization step and (3) presterilization step are carried out in any order after subjecting the raw milk mix prepared in (1) to (2) homogenization step. ) It may be subjected to a pre-sterilization step, or it may be subjected to a (2) homogenization step after being subjected to (3) a pre-sterilization step. Furthermore, (2) the homogenization step and (3) the presterilization step can be performed simultaneously.

Further, the manufacturing process of the present invention described above may further include a step (4) of filling a container with the raw milk mix obtained in the pretreatment steps (1) to (3) above (filling step). can. The filling step may be performed before adding lactic acid bacteria to the raw milk mix obtained in the pretreatment steps (1) to (3), or may be performed in the pretreatment steps (1) to (3). This may be carried out after adding lactic acid bacteria to the obtained raw milk mix.
Although not limited, it is preferable to include a filling step after the pretreatment steps (1) to (3) above and before adding lactic acid bacteria in step (a). That is, after the raw milk mix obtained in the pretreatment steps (1) to (3) is filled into a container, it is subjected to the step (a), and lactic acid bacteria are added to the raw milk mix filled in the container. , it is preferable to ferment in a container.

Each step will be explained below.
[(1) Raw milk mix preparation process]
The "raw milk mix" targeted by the present invention is a composition containing milk components derived from cow's milk, with a whey protein content of 1.5 to 3.0% by mass as a solid content and a casein protein content of 1.5 to 3.0% by mass. is 2.0 to 3.0% by mass as a solid content, and the ratio of whey protein to 100 parts by mass of casein protein is 50 to 125 parts by mass.
The raw milk mix contains raw milk squeezed from cows, cow milk, skim milk, whole milk powder, skim milk powder, whole fat concentrated milk, skim concentrated milk, sweetened condensed milk, sweetened skim condensed milk, evaporated condensed milk, and non-fat milk. Sugar-skimmed condensed milk, whey (whey), whey powder, desalted whey, desalted whey powder, whey protein concentrate (WPC), whey protein isolate (WPI), alpha-lactalbumin, beta-lactoglobulin, milk protein Two or more types selected from concentrate (MPC), casein, sodium caseinate, calcium caseinate, cream, fermented cream, compound cream, cream powder, butter, fermented butter, buttermilk, buttermilk powder, butter oil, etc. It can be prepared by appropriately setting and adjusting the proportions of whey protein and casein protein in 100% by mass of the raw milk mix.
The content of whey protein and casein protein in the raw milk mix may be within the above range and is not limited, but the whey protein content is preferably 1.5 to 3.0% by mass, more preferably 1.7 to 2.0% by mass. The amount of casein protein is preferably 2.3 to 3% by weight, more preferably 2.5 to 3.0% by weight. Further, the ratio of whey protein to 100 parts by mass of casein protein (solid content mass ratio) is also not limited as described above, but is preferably 50 to 120 parts by mass, more preferably 62 to 100 parts by mass.
When using milk as a raw material, the sterilization treatment stipulated by the Milk Ministerial Ordinance is ``heat sterilization at 63℃ for 30 minutes using a holding method, or heat sterilization by a method that has an equivalent or higher sterilization effect.'' It is sufficient if this is done. Sterilization methods include low temperature sterilization (LTLT), continuous pasteurization (LTLT), high temperature sterilization (HTLT), high temperature short sterilization (HTST), ultra high temperature flash sterilization (UHT), and ultra high temperature sterilization. (LL) is included. 90% of milk sold in Japan is UHT treated.

The raw milk mix can be adjusted so that the content of non-fat milk solids is 8% by mass or more based on the specifications for fermented milk. It is preferably 9 to 12% by weight, more preferably 9.5 to 11.2% by weight. Although not limited, the raw milk mix should have a milk fat ratio 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; The proportion of carbohydrates other than lactose is 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; It can be adjusted to a range of 0 to 10% by weight, preferably 2.5 to 7.5% by weight, more preferably 4 to 6% by weight.

The raw milk mix can be prepared using only the milk components described above, but as long as the effects of the present invention are not impaired, in addition to the milk components, for example, lipids, whey protein, and casein protein may be added. It may also be prepared by blending other proteins, carbohydrates, minerals (salts), vitamins, flavor components, perfumes, pigments, and other food additives. Although not strictly limited, the raw milk mix targeted by the present invention may contain a gelling agent, a thickening polysaccharide, or a stabilizer (for example, the β-glucan-containing material described in Patent Document 1, It is preferable that components corresponding to modified starches such as crosslinked modified starch described in Patent Document 2 are not included.
The raw milk mix of the present invention is a composition containing water together with the milk components. The proportion of water in the raw milk mix can range from 11 to 25% by mass. Preferably it is 12 to 20% by weight, more preferably 13 to 16% by weight.

[(2) Homogenization process]
The step of homogenizing the raw milk mix refers to finely pulverizing (refining) particles composed of proteins and/or lipids contained in the raw milk mix. The method of homogenization can follow a standard method and is not limited, but for example, a method of stirring while applying shear using a device such as a mixer or a pump, a method of stirring the raw milk mix while applying pressure, and forcing it to pass through a narrow gap while pressurizing the raw milk mix. Alternatively, a method may be used in which the raw milk mix is passed through a narrow gap while being sucked under reduced pressure. Note that the method and equipment for homogenizing the raw milk are not limited to the methods described above, and any known method and equipment can be used.
The homogenization step may be performed to achieve an average particle size of the raw milk of 0.8 μm or less.

[(3) Pre-sterilization step]
The step of sterilizing the raw milk mix is carried out with the aim of sterilizing the raw milk mix until the number of bacteria (excluding spores) contained in the raw milk mix becomes 10 to the third power or less per ml.
Any method and conditions may be used as long as this objective can be achieved; for example, a heat treatment method used for sterilizing milk can be adopted. Heat treatment methods used to sterilize milk include, for example, ultra-high temperature sterilization (UHT sterilization), which involves heat treatment at 120 to 150°C for 2 to 3 seconds, and continuous heat treatment at 72 to 75°C, for 15 seconds or more. High-temperature short-time sterilization (HTST sterilization) method, high-temperature holding sterilization (HTLT sterilization) method in which heat treatment is performed at 75°C or higher for 15 minutes or more using a holding method, and high-temperature short-term sterilization (HTLT sterilization) in which heat treatment is performed continuously at 72°C or higher for 15 seconds or more. HTST sterilization) method, low temperature holding sterilization (LTLT sterilization) method, which involves heat treatment at 63 to 65 degrees Celsius for 30 minutes, and continuous pasteurization (LTLT sterilization) method, which involves continuous heat treatment at 65 to 68 degrees Celsius for 30 minutes or more. and an ultra-high temperature sterilization (LL sterilization) method in which heat treatment is performed at 135 to 150°C for 1 to 4 seconds. The method is not limited to the above-mentioned method, as long as the thermal history expressed by "heating temperature (product temperature) x heating time x pressure" is equal to or higher than the heat treatment method described above. Alternatively, a method may be used in which the raw milk mix is heat-treated for 1 minute at a temperature of 95° C. under normal pressure conditions.

[(4) Filling process]
As mentioned above, the step of filling the raw milk mix into a container may be performed before the raw milk mix is fermented. This can be done before adding the lactic acid bacteria or after adding the starter to the raw milk mix.
The container to be filled with the raw milk mix may be any container commonly used in the production of fermented milk (dairy products) by post-fermentation, and is not particularly limited in size (capacity), material, and shape. . For example, the size (capacity) of the container may be a one-serve size, a family size, or a business size. Further, although the material is not limited, for example, containers made of plastic, glass, paper, etc. can be used. The shape is not particularly limited as long as it has strength and sealing properties, and may be, for example, a cup shape, a brick pack shape, or a cheer pack shape. A commonly used method and device for filling the container are also used.

[(a) Fermentation process]
In the present invention, the fermentation step can be carried out by adding lactic acid bacteria as a starter to the raw milk mix and then fermenting the raw milk mix in a container.
Examples of lactic acid bacteria used as starters include Lactobacillus bulgaricus (L. bulgaricus), Streptococcus thermophilus (S. thermophilus), and Lactobacillus lactis (L. lactis). ), Lactobacillus gasseri (L.gasseri), Lactobacillus plantarum (L.plantarum), Lactobacillus casei (L.casei), Lactobacillus acidophilus (L. One type of lactic acid bacteria commonly used in the production of fermented milk, such as Lactic acidophilus and Bifidobacterium, can be used alone, or two or more types can be used in combination. You can also do it. Bacterium bulgaricus is preferred. In addition, a mixed starter of B. bulgaricus and B. thermophilus can also be used from the viewpoint that it is standardized as a yogurt starter in the Codex standard.

The amount of starter (lactic acid bacteria) added to the raw milk mix may be any amount commonly used in the production of fermented milk, for example 0.1 to 10% by mass, preferably 0.1 to 10% by mass, based on the raw milk mix. The amount is 2 to 5% by weight, more preferably 0.5 to 4% by weight. In addition, the starter may be added by any method generally used in the production of fermented milk, such as adding it aseptically to the raw milk mix filled in a container, or adding it aseptically to the raw milk mix in a pipe. In this method, the starter is added in-line while the water is still in the tank, and then the starter is filled into containers. Note that the method and equipment for adding the starter to the raw milk mix are not limited to the above-mentioned method, and any known method and equipment can be used.

Fermentation of the raw milk mix can be carried out by adding a starter (lactic acid bacteria) and then keeping the mixture filled in a container stationary in a fermentation chamber set at a predetermined temperature.
The conditions for fermenting the raw milk mix are adjusted in consideration of the type and amount of lactic acid bacteria added to the raw milk, and the flavor, texture, physical properties, etc. of the fermented milk to be actually obtained. For example, the lower limit of the temperature at which the raw milk mix is fermented (fermentation temperature) is preferably 33°C or higher, more preferably 35°C or higher, and still more preferably 38°C or higher. The upper limit of the temperature at which raw material milk is fermented 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 arbitrarily combining these lower and upper limits. Examples include, but are not limited to, 33-50°C, 35-48°C, 38-45°C, etc.

Further, the time for fermenting the raw milk (fermentation time) is until the pH of the fermented milk falls within the range of 5.3 to 5.9. In other words, fermentation is terminated when the pH of the fermented milk falls within the range of 5.3 to 5.9. The pH range for terminating fermentation is preferably pH 5.4 to 5.8, more preferably pH 5.5 to 5.7. By completing the fermentation in this pH range, it is possible to obtain fermented milk with less sourness and a texture (hardness, texture) similar to tofu, which is one of the effects of the present invention.
Note that any known method and equipment can be used for fermenting the raw milk mix.

[(b) Heating process]
The heating step is a step of heating the fermented milk, which has reached a predetermined pH in the fermentation step, while being filled in a container. The heat treatment is performed without stirring the fermented milk (under non-stirring conditions).
This process is carried out to sterilize lactic acid bacteria added as a starter to the raw milk mix to prevent fermentation from proceeding, and to kill bacteria to ensure hygiene and safety as a food product and a shelf life.
The heat treatment conditions may be any method and conditions that can achieve this purpose. For example, if the heat history expressed as "heating temperature (product temperature) x heating time x pressure" is "75℃ x 15 minutes x normal pressure"'' can be used. The thermal history of "75°C x 15 minutes x normal pressure" means that the product is heated under normal pressure conditions for 15 minutes after the product temperature reaches 75°C. . By doing this, we are able to meet the standards stipulated for "sterilized fermented milk" in the Milk Ministerial Ordinance (after fermentation, heat sterilization at 75℃ for 15 minutes or more, or heat sterilization using a method that has an equivalent or higher sterilization effect). It is possible to obtain sterilized fermented milk that conforms to the fermented milk to be produced. An example of a heating method that results in a thermal history of "75° C. x 15 minutes x normal pressure" or more includes a heating treatment of immersion in hot water at 85° C. for 60 minutes under normal pressure conditions. Note that normal pressure here means that the pressure inside the container is in a normal pressure state, and does not include a pressure state that is artificially pressurized or reduced.
Such heat treatment may be performed after the fermented milk filled in a container is sealed and packaged. Alternatively, the container may be heat-treated before being sealed and then sealed.
Note that any known method and equipment can be used for heat-treating the fermented milk in a container.

After being cooled, the sterilized fermented milk produced in this manner can be placed in a container, sealed and packaged, and then distributed.
The sterilized fermented milk obtained by the production method of the present invention has shape retention and/or resistance to boiling down, as described in the examples below, and has a texture that is less sour and tofu-like (silky). It has the firmness and texture of tofu (tofu, firm tofu). Therefore, it can be used in a variety of cooking methods as a milk protein-containing ingredient instead of tofu.

As mentioned above, in this specification, the terms "comprising" and "containing" include the meanings of "consisting of" and "consisting essentially of."

Hereinafter, the present invention will be explained using experimental examples in order to help understand the structure and effects of the present invention. However, the present invention is not limited in any way by these experimental examples. The following experiments were conducted at room temperature (25±5° C.) and atmospheric pressure (normal pressure) unless otherwise specified. In addition, unless otherwise mentioned, "%" described below means "mass %" and "part" means "mass part."

The raw materials used in the following experimental examples (examples, comparative examples) are as follows.
(material)
Milk: Unadjusted milk (milk protein 3.0-3.6%, milk fat 3.5-4.2%, non-fat milk solids 8.5-9.3%) Meiji Milk Co., Ltd. Protein concentrate (MPC): MPC80 (casein 64.4%, whey 16.1%) Lacto Japan Co., Ltd. Whey protein isolate (WPI): WPI895 (whey 93.5%) Fonterra Japan Co., Ltd.
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.)

Experimental Example 1 Effect of type and content of milk protein, presence or absence of secondary heat treatment, and pH at the end of fermentation Various fermented milks (Examples 1 to 2, Comparative Examples 1 to 10) were prepared by the following method, The type and content of milk protein added to the raw milk mix, the presence or absence of secondary heat treatment, and the pH at the end of fermentation were evaluated for their effects on the shape retention, resistance to boiling, and texture of the obtained fermented milk.

(1) Preparation of fermented milk (a) No secondary heat treatment after fermentation: Comparative Examples 1 to 6
MPC or WPI was added to 500 g of milk (homogenized in the manufacturing process) at a rate of 2% and mixed to prepare raw milk containing the components listed in Table 1 (Comparative Examples 1 to 3). 3: MPC addition, Comparative Examples 4 to 6: WPI addition). This raw milk was heat-treated at 95° C. for 1 minute (pre-sterilization treatment) to prepare a raw milk mix. This raw milk mix was cooled to 43° C., and lactic acid bacteria starter was added (inoculated) at a rate of 3%. Thereafter, the mixture was filled into a plastic cylindrical (diameter 7 cm) cup container (filling capacity: 100 g), left to stand in a fermentation chamber (43° C.), and fermented until the pH shown in Table 1 was reached. After reaching the pH, it was cooled in a refrigerator (10°C or less) to produce fermented milk (Comparative Examples 1 to 6).

(b) With secondary heat treatment after fermentation: Comparative Examples 7 to 10, Examples 1 to 2
MPC (or WPI) was added and mixed at a rate of 2% to 500 g of milk (homogenized in the manufacturing process) to prepare raw milk containing the components listed in Table 1 (Comparative Example 7) ~10: MPC addition, Comparative Example 11 and Examples 1-2: WPI addition).This raw milk was heat-treated at 95°C for 1 minute (pre-sterilization treatment) to prepare a raw milk mix.This raw milk mix was It was cooled to 43°C, and lactic acid bacteria starter was added (inoculated) at a rate of 3%.Then, it was filled into a plastic cup container (filling capacity: 100g), left to stand in a fermentation chamber (43°C), and then Fermentation was carried out until the pH reached 1. After reaching the pH, the container was immersed in boiling water at 85°C for 60 minutes (secondary heat treatment), and then cooled by being transferred to ice-cold water and immersed for 30 minutes. Sterilized fermented milk (Comparative Examples 7 to 10, Examples 1 to 2) was produced.

(2) Evaluation of prepared sterilized fermented milk (a) Properties and shape retention As mentioned above, after preparation, cooled fermented milk (Comparative Examples 1 to 6) and sterilized fermented milk (Comparative Examples 7 to 10, Examples 1 to 2) (product temperature 25°C), the container was turned over and the sterilized fermented milk inside was transferred directly to a plate, and the properties (liquid, semi-solid, solid) were confirmed. If the fermented milk is fluid after being left to stand for 60 minutes, like milk, it is called "liquid." It is semi-liquid, like a shake or soft yogurt, and it collapses under its own weight and cannot maintain its shape. The case was recognized as "semi-solid", and all of these were judged as "shape retention: ×". On the other hand, if the shape could be maintained without collapsing even under its own weight, it was recognized as "solid" and judged as "shape retention: 〇". Note that the shape can be maintained not only when the cup shape is maintained as it is, but also when the corners (edges) are not collapsed even if the cup shape is slightly sunken due to its own weight. I decided that.

(b) Resistance to boiling down After preparation, among the fermented milks (Comparative Examples 1 to 10, Examples 1 to 2) that were cooled, those determined to be solid were evaluated for their resistance to boiling down. Resistance to boiling down is determined by soaking 100g of sterilized fermented milk directly from the container in 1L of boiling water (80°C) for 10 minutes, and comparing it to before soaking, when the shape has completely collapsed. "×", when the shape partially collapsed, it was judged as "resistance to boiling down: △", and when the shape did not collapse, it was judged as "resistance to boiling down: 〇". Note that the shape is not only maintained when the shape before immersion is maintained, but also when the corners (edges) have not collapsed even though the shape has swollen as a whole due to immersion in hot water. It was determined that it had not collapsed.

(c) Sour taste and texture Six expert panels trained in sensory evaluation were asked to eat fermented milk (Comparative Examples 1 to 10, Examples 1 to 2) that had been prepared and cooled to 10°C. (Hardness and texture) were evaluated according to the following method.

[acidity]
In comparison with a commercially available plain yogurt with a sour taste (product name: Meiji Bulgaria Yogurt LB81 Plain, manufactured by Meiji Co., Ltd., pH 4.2) (control), each fermented milk (Comparative Examples 1 to 10, The sourness of Examples 1-2) was evaluated.
"Sour taste: +": There is a sour taste similar to that of the control.
"Slightly sour taste: ±": Less sour taste than the control, but slightly felt "No sour taste: -": No sour taste felt.

[Texture]
Compared to the texture (hardness, texture [feeling of the tongue when placed in the mouth and rubbed with the tongue]) of commercially available regular firm tofu and silken tofu (control), the following criteria were used: The texture of each fermented milk (Comparative Examples 1 to 10, Examples 1 to 2) was classified and evaluated as to whether the texture was good or bad.

The firm tofu and silken tofu used as controls are both listed in the 2020 Standard Table of Food Composition of Japan (8th edition) (Ministry of Education, Culture, Sports, Science and Technology of Japan) ("General Composition List - Inorganics and Vitamins"). It meets the standards.
The maximum loads (N) of firm tofu and silken tofu (number of specimens for each: 3) measured by the following breaking test were as shown in Table 3.

[Rupture test]
(1) Measuring device Creep meter (viscoelasticity measuring device): Leonor II (model number RE-3305S, parallel plate type) manufactured by Yamaden Co., Ltd. (2) Conditions for rupture test Plunger: Disc type (diameter 3 cm, thickness 8mm)
Contact area with test sample piece: 7.1cm ²Compression speed: 1mm/sec Compression distance: 10mm
(3) Rupture test method Place the test sample (temperature: 25°C) in a plastic cup container (filling capacity: 100g) on the test stand of the creep meter, and lower the plunger from the top of the test sample. A rupture test was conducted under the above conditions by applying a load in the thickness direction to the surface of the test specimen. Record and analyze the compression curve using an automatic analyzer (model number CA-3305: manufactured by Yamaden Co., Ltd.), a peak indicator (model number PA-3305: manufactured by Yamaden Co., Ltd.), and a recorder, and start measurement. The maximum load (N) was defined as the maximum load (N) that was applied during the period from 1 to 2 until the test specimen broke.

(3) Evaluation results The evaluation results of the fermented milk produced in (1) (Comparative Examples 1 to 10, Examples 1 to 2) are listed in Table 4.

As shown in Table 4, WPI is added to milk as a fermented milk raw material, and the milk protein content is 2.49% by mass of whey and 2.48% by mass of casein (ratio of whey to 100 parts by mass of casein: Using a raw milk mix prepared to contain 100.4 parts by mass), ferment it with lactic acid bacteria in individual containers until the pH reaches 5.4 to 5.8. By performing a secondary heat treatment (thermal history equivalent to 75°C x 15 minutes x normal pressure) or higher, we produce a set type of sterilized fermented milk that has good shape retention and does not easily collapse even when boiled. It was confirmed that Examples 1 and 2) were obtained. In addition, this set type of sterilized fermented milk did not have the sour taste that is felt in ordinary yogurt, was harder than silken tofu, softer than firm tofu, and had a good texture.

On the other hand, when MPC is added to milk as a raw material for fermented milk, the milk protein content becomes 0.94% by mass of whey and 3.76% by mass of casein (ratio of whey to 100 parts by mass of casein: 25.0 parts by mass). Fermented milk prepared using a raw milk mix prepared to contain within a range of Met. In addition, fermented milks prepared by adding WPI to milk as a raw material for fermented milk so that the milk protein content was the same as in Examples 1 and 2 (Comparative Examples 4 to 6, 10) had good shape retention. However, fermented milk that was not subjected to secondary heat treatment (Comparative Examples 4 to 6) did not have good resistance to boiling down, and even when secondary heat treatment was performed, the pH at the end of fermentation was 5 or less. The fermented milk (Comparative Example 10) had good shape retention and boiling resistance, but had a strong sour taste and a tendency to have an excessively hard texture.

Experimental Example 2 Effect of WPI Blend Amount (1) Production of Fermented Milk Based on the results of Experimental Example 1 above, various fermented milks (Example 3 -8 and Comparative Examples 11 to 26) were prepared (see Table 5). The fermented milk of Comparative Examples 11 to 21 was prepared using the method described in Experimental Example 1 (1) (a) (pH 5.8 or 5.4 at the end of fermentation: no secondary heat treatment), and Examples 3 to 8 and The fermented milk of Comparative Examples 22 to 26 was prepared according to the method described in Experimental Example 1 (1) (b) (pH 5.8 or 5.4 at the end of fermentation: with secondary heat treatment).

(2) Evaluation of fermented milk The obtained fermented milk was evaluated in the same manner as in Experimental Example 1 for properties, shape retention, resistance to boiling, acidity, and texture (hardness, texture).
Further, regarding the solid fermented milk, a breaking test was conducted according to the breaking test method performed on tofu in Experimental Example 1, and the maximum load (N) was determined. Furthermore, for fermented milk that is determined to be solid, the turbidity of the broth after subjecting it to the boil-down resistance test is measured using the method below, and the degree of disintegration of the fermented milk (contents: milk fat, milk The degree of efflux of proteins, etc.) was evaluated.

[Turbidity test]
100 g of fermented milk taken out from the container is immersed in 1 L of boiling water (80° C.) for 10 minutes to evaluate its resistance to boiling, and the remaining liquid after taking out the fermented milk is used as broth. After cooling, the solution is passed through a 60# filter, and the turbidity (NTU) of the permeated solution is measured using a 200P TURBIDIMETER (manufactured by HACH).
According to the permeate turbidity (NTU), it was evaluated as follows:
〇：＜5NTU
△: 10-5NTU
×: >10NTU

(3) Evaluation results The evaluation results of the fermented milk produced in (1) (Comparative Examples 11 to 26, Examples 3 to 8) are listed in Table 6. Furthermore, images of the broths (in beakers) used in the broth turbidity test for Comparative Examples 24 and 25 and Examples 5 and 6 are shown in FIG.

As shown in Table 6, as a fermented milk raw material, the milk protein content is 1.56 to 2.95% by mass of whey and 2.46 to 2.5% by mass of casein, and the whey protein content is 1.56 to 2.95% by mass and the casein content is 2.46 to 2.5% by mass, based on 100 parts by mass of casein. Using a raw milk mix prepared to contain 62.4 to 119.9 parts by mass of A set-type sterilizer that has good shape retention and does not easily collapse even when boiled by subjecting the container to secondary heat treatment (heat history equivalent to 75°C x 15 minutes x normal pressure) or higher within the pH range. It was confirmed that fermented milk (Examples 3 to 8) was obtained. In addition, it was confirmed that this set type of sterilized fermented milk does not have the sour taste that is felt in regular yogurt, and has a tofu-like (firm to silken tofu) texture (hardness and texture). .

On the other hand, as a fermented milk raw material, the milk protein content is 0.63 to 1.1% by mass of whey and 2.51 to 2.53% by mass of casein (ratio of whey to 100 parts by mass of casein: 24.9 to 43. Fermented milk prepared using raw milk mixes containing 8 parts by mass (Comparative Examples 11 to 14, 22 to 25) had poor shape retention, or even if the shape retention was good, The boiling resistance was poor. In addition, fermented milk (Comparative Examples 15 to 20) prepared so that the milk protein content was the same as in Examples 3 to 8 but not subjected to secondary heat treatment as a fermented milk raw material (Comparative Examples 15 to 20) had shape retention. Although the results were good, the boiling resistance was poor and the turbidity of the broth was high. Furthermore, the fermented milk raw material is prepared so that the milk protein content is within a range of whey content of 3.42% by mass and casein content of 2.45% by mass (ratio of whey to 100 parts by mass of casein: 139.6 parts by mass). Although the fermented milk prepared using the raw material milk mix (Comparative Examples 21 and 26) had good shape retention and boiling resistance, the texture tended to be too hard.

Fermented milk, which is a healthy food, can now be used for purposes that have never existed before (general-purpose cooking). Mapo tofu, etc.) It does not fall apart when boiled, and can be ingested without any loss of whey protein in the broth. It is possible to obtain fermented milk without sour taste. Overall, this will lead to the development of a healthy food scene and the development of a new market for fermented milk.

Claims (10)

1. Contains whey protein at a ratio of 1.5 to 3.0% by mass and casein protein at a ratio of 2.0 to 3.0% by mass, and the ratio of whey protein to 100 parts by mass of casein protein is 50 to 125 parts by mass. A set type sterilized fermented milk with a pH of 5.3 to 5.9.
2. The sterilized fermented milk according to claim 1, wherein the content of non-fat milk solids is 9.5 to 11.2% by mass.
3. The sterilized fermented milk according to claim 1 or 2, which has shape retention and/or resistance to boiling.
4. The sterilized fermented milk according to claim 1 or 2, wherein the maximum load at break is 5.0 to 8.0 N in a break test using a plunger.
5. Raw materials containing a whey protein content of 1.5 to 3.0 mass % and a casein protein content of 2.0 to 3.0 mass %, and the ratio of whey protein to 100 mass parts of casein protein is 50 to 125 parts by mass. A step in which lactic acid bacteria are added to the milk mix and fermented in a container until the pH reaches 5.3 to 5.9, and the resulting fermented milk is placed in a container with a thermal history of 75°C. A method for producing a set type of sterilized fermented milk, which includes a step of heat treatment to a temperature of 15 minutes x normal pressure or more.
6. The production method according to claim 5, wherein the non-fat milk solid content of the raw milk mix is 9.5 to 11.2% by mass.
7. The manufacturing method according to claim 5 or 6, wherein the raw milk mix is homogenized and sterilized before adding the lactic acid bacteria.
8. Before step (a), the whey protein content is 1.5 to 3.0% by mass, the casein protein content is 2.0 to 3.0% by mass, and the ratio of whey protein to 100 parts by mass of casein protein is 50 to 3.0% by mass. The manufacturing method according to claim 7, comprising the steps of homogenizing and sterilizing 125 parts by mass of the raw milk mix.
9. The production method according to claim 5 or 6, wherein the fermentation temperature is 35 to 48°C.
10. The production method according to claim 7, wherein the fermentation temperature is 35 to 48°C.

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