JP2021073882A - Method for producing lactic acid food that can be preserved at room temperature and method for improving physical stability thereof, and heat sterilization method for lactic acid food - Google Patents

Abstract

To improve the physical stability of lactic acid food that can be preserved at room temperature.SOLUTION: A method for producing lactic acid food that can be preserved at room temperature includes a heat sterilization step for heat sterilizing lactic acid food containing stabilizer, and a cooling step for cooling the lactic acid food to 1-10°C after the heat sterilization step.SELECTED DRAWING: None

Description

The present invention relates to a method for producing sour milk food stored at room temperature, a method for improving the physical stability of sour milk food stored at room temperature, and a method for heat sterilizing sour milk food.

For example, yogurt is produced by adding lactic acid bacteria to a dairy raw material and fermenting it. Since general yogurt contains live lactic acid bacteria, it needs to be stored refrigerated, and the storage period is relatively short.
On the other hand, a method for producing yogurt that can be stored at room temperature by heat sterilization after fermentation has also been proposed (for example, Patent Documents 1 and 2).

Japanese Unexamined Patent Publication No. 58-187133 Japanese Unexamined Patent Publication No. 2012-530489

Heating acidic dairy products such as yogurt has the problem of agglutination of milk proteins. In response to this problem, the inventions described in Patent Documents 1 and 2 propose a method of adding a stabilizer before heat sterilization.
However, it is difficult to sufficiently enhance the physical stability by simply adding a stabilizer.
An object of the present invention is to provide a method for producing a sour milk food stored at room temperature and a method for improving the physical stability of the sour milk food stored at room temperature, which is obtained by heat sterilizing the sour milk food, and a method for heat sterilizing the sour milk food. And.

The present invention has the following aspects.
[1] A sour milk food stored at room temperature, which comprises a heat sterilization step of heat sterilizing the sour milk food containing a stabilizer and a cooling step of cooling the sour milk food to 1 to 10 ° C. after the heat sterilization step. Manufacturing method.
[2] The method for producing a sour milk food stored at room temperature, which comprises a filling step of filling the container with the sour milk food and sealing it after the heat sterilization step and before the cooling step.
[3] The method for producing a sour milk food stored at room temperature according to [2], wherein the temperature of the sour milk food when filling the container is 15 to 40 ° C.
[4] The method for producing a sour milk food stored at room temperature according to [2] or [3], wherein the time from the end of the filling step to the start of the cooling is within 24 hours.
[5] An acid having a heat sterilization step of heat sterilizing the sour milk food containing a stabilizer and a cooling step of cooling the sour milk food to 1 to 10 ° C. after the heat sterilization step. Heat sterilization method for dairy foods.
[6] A method for improving the physical stability of sour milk foods stored at room temperature in which sour milk foods are heat-sterilized, wherein the sour milk foods are heat-sterilized with a stabilizer contained therein, and the above-mentioned heat sterilization step. A method for improving the physical stability of sour milk food stored at room temperature, which comprises a cooling step of cooling the sour milk food to 1 to 10 ° C. after the heat sterilization step.

According to the present invention, the physical characteristics of sour milk foods stored at room temperature can be improved.
According to the present invention, it is possible to improve the physical characteristic stability of heat-sterilized sour milk foods.

As used herein, the term "sour milk food" means a food containing milk protein and in which a milk protein card is formed by the production of acid by fermentation or by the addition of an acid component. Specific examples of sour milk foods include fermented milk and lactic acid bacteria beverages.
The non-fat milk solids content of fermented milk is 8.0% or more, and the non-fat milk solids content of lactic acid bacteria beverages is less than 8.0%.
Among lactic acid bacteria beverages, those containing 3.0% or more of non-fat milk solids are classified as "dairy products" specified by the Ordinance of the Ministry of Milk, etc. and are labeled as "dairy products lactic acid bacteria beverages". In particular, those sterilized after fermentation are labeled as "dairy lactic acid bacteria beverage (sterilized)". Non-fat milk solids with a solid content of less than 3.0% are classified as "foods made mainly from milk" and labeled as "lactic acid bacteria beverages".
In addition, among fermented milks, those sterilized after fermentation are labeled as "fermented milk (sterilized)".

As used herein, the term "room temperature" means a temperature in the range of more than 10 ° C and 35 ° C or less. The “normal temperature-preserved sour milk food” means a sour milk food that can be stored and distributed at room temperature without the need to refrigerate the manufactured final product at 10 ° C. or lower.

As used herein, the term "stabilizer" refers to the effect of suppressing the aggregation of milk proteins in heat sterilization under acidic conditions by increasing the viscosity of the liquid containing milk proteins or gelling the liquid, and during storage. It means additives and foods that exert the effect of suppressing morphological changes.
As the stabilizer, a water-soluble polysaccharide or gelatin having the ability to thicken or gel by dissolving in a solvent and then cooling is preferable.
Specific examples of the stabilizer include carrageenan, agar, gelatin, locust bean gum, tara gum, guar gum, xanthan gum, tamarind seed gum, gellan gum, pectin, soybean polysaccharide, carboxymethyl cellulose (CMC), starch and modified starch. These may be used alone or in combination of two or more.

<Measurement method>
In the present specification, the non-fat milk solid content is a value obtained by subtracting the milk-derived fat content from the milk-derived solid content.
The protein and fat contents are measured according to the procedure disclosed in the attachment "Analysis method of nutritional components, etc." of the Food Labeling Standards (2015 Cabinet Office Ordinance No. 10).
The solid content is a value calculated by solid content (mass%) = 100-moisture (mass%).
The water content is a value measured by a normal pressure heating and drying method (drying aid addition method).

<Manufacturing method of sour milk food stored at room temperature>
The method for producing a sour milk food stored at room temperature according to the present embodiment has undergone a heat sterilization step of heat sterilizing a sour milk food containing a stabilizer (hereinafter, also referred to as sour milk food (I)) and a heat sterilization step. It has a cooling step for cooling sour milk food (hereinafter, also referred to as sour milk food (II)).
In the heat sterilization step, the sour milk food (I) is sterilized by heating to obtain the sour milk food (II). The component composition of sour milk food (I) and sour milk food (II) is the same except for heat denaturation.
In the cooling step, the sour milk food (II) is cooled to obtain a sour milk food stored at room temperature. The composition of the sour milk food (II) and the sour milk food stored at room temperature is the same except for the food material added after heat sterilization.

The non-fat milk solid content is preferably 0.5 to 20% by mass, more preferably 3 to 15% by mass, still more preferably 8 to 12% by mass, based on the total mass of the sour milk food (I). When it is at least the lower limit of the above range, an appropriate milky taste is exhibited and a good flavor can be obtained. If it is not more than the upper limit, it is easy to add an appropriate amount of the stabilizer, and it is easy to suppress the morphological change during storage.
The protein content is preferably 0.2 to 7.1% by mass, more preferably 1.1 to 5.3% by mass, and 2.8 to 4.3, based on the total mass of the sour milk food (I). Mass% is more preferred. When it is at least the lower limit of the above range, agglutination of milk proteins is likely to occur due to heat sterilization, and the application of the present invention has a great effect. If it is not more than the upper limit, it is easy to add an appropriate amount of the stabilizer, and it is easy to suppress the morphological change during storage.

The pH of the sour milk food (I) at 25 ° C. is preferably 6.0 or less. In terms of flavor, pH 3.0 or higher is preferable. Further, the closer to the isoelectric point (pH 4.6) of casein, the more likely it is that milk protein aggregates due to heat sterilization, and the greater the effect of applying the present invention. From this point of view, the pH of the sour milk food (I) is more preferably 3.4 to 5.4, and even more preferably 3.8 to 4.8.
The acid contained in the sour milk food (I) is not particularly limited.

The stabilizer contributes to the improvement of physical characteristic stability. In terms of flavor, it is preferable that the content of the stabilizer is low. From this viewpoint, the content is preferably 0.01 to 3.5% by mass, more preferably 0.04 to 3.3% by mass, and 0.05 to 3% by mass with respect to the total mass of the sour milk food (I). .0% by mass is more preferable.

The method for preparing the sour milk food (I) will be described later.
In the process of heat sterilizing sour milk food (I), the heat sterilization conditions (heating temperature and heating time) are the Ministry of Milk, etc. ("Ministry Ordinance on Ingredient Standards of Milk and Milk Products", Ministry of Health and Welfare Ordinance No. 52, 1951. , 2015 revised on January 9, 2015.) The heat sterilization conditions after fermentation of fermented milk can be applied. Specifically, heating conditions such as heating at 75 ° C. or higher for 15 minutes or having a bactericidal effect equivalent to or higher than this are preferable. The lower the heating temperature during heat sterilization, the longer the time required for heat sterilization, and if it is too high, changes in flavor and physical properties due to heating are likely to occur. From these viewpoints, the heating conditions are preferably in the range of 80 to 112 ° C. for 5 minutes to 2 seconds, and more preferably 90 to 100 ° C. for 30 to 3 seconds.
Heat sterilization can be performed using a commonly used heat sterilizer such as batch sterilization, tubular sterilization, and plate sterilization. If necessary, homogenization treatment may be performed before one or both before heat sterilization and after heat sterilization.

It is preferable that the heat-sterilized sour milk food (II) is filled in a container and sealed (filling step) before the cooling step or after the cooling step.
In the filling step, it is preferable that the sour milk food (II) is aseptically filled in a container and sealed. As a method of aseptically filling a container, a known aseptic filling method such as a method of filling a sterilized container and sealing it in a sterile environment such as a sterile room where the viable cell count is controlled can be used. ..

When a filling step is provided after the cooling step, for example, the sour milk food (II) that has been heat-sterilized is cooled to 1 to 10 ° C. by the method described later (cooling step), and if necessary, homogenized. By filling and sealing the container, a sour milk food stored at room temperature can be obtained.
A filling step may be provided after the cooling step, and a cooling step may be provided again after the filling step.

When a filling step is provided before the cooling step, for example, the sour milk food (II) that has been heat-sterilized is cooled to a temperature of more than 10 ° C. and 50 ° C. or lower, filled in a container, and sealed. If necessary, homogenize before heat sterilization or after heat sterilization and before filling. The temperature (filling temperature) of the sour milk food (II) when it is filled in a container is preferably 15 to 40 ° C, more preferably 20 to 30 ° C. When the filling temperature is within the above range, control during filling becomes easier.
When the sour milk food (II) after heat sterilization is kept in a sterile environment and filled in a container, it is preferable that the time from the completion of heat sterilization to the filling is short. From that viewpoint, it is preferable to perform the filling step after the heat sterilization step, and then perform the cooling step.

Before filling the sour milk food (II) in a container, food materials other than the sour milk food (II) may be added to the sour milk food (II) and mixed as long as the effects of the present invention are not impaired. .. Use sterilized food materials.
Examples of food materials include fruits and fruit juices and fruit preserves and fruit sauces containing them.

In the cooling step, the sour milk food (II) is cooled to 1 to 10 ° C. Preferably, the sour milk food (II) filled in the container is cooled. For example, sour milk food (II) is placed in a refrigerator having an internal temperature of 1 to 10 ° C. and cooled. The cooling process contributes to improving the physical stability of sour milk foods stored at room temperature.
In the cooling step, cooling starts when the sour milk food (II) is put into an environment whose temperature is adjusted to 1 to 10 ° C., and cooling ends when the sour milk food (II) is taken out of the environment. The time from the start of cooling to the end of cooling of sour milk food (II) is defined as the cooling time.
The cooling time may be longer than the time required for the product temperature (center temperature) of the sour milk food (II) to reach 10 ° C. or lower. For example, 10 minutes or more is preferable, 4 hours or more is more preferable, and 24 hours or more is further preferable. The upper limit of the cooling time is not particularly limited.
From the viewpoint of promoting the formation of a complex structure of the milk protein and the stabilizer, the sour milk food (II) is preferably cooled to 1 to 8 ° C, more preferably 1 to 5 ° C.

The sour milk food stored at room temperature that has undergone the cooling step can be stored or distributed at room temperature.
When the sour milk food (II) after heat sterilization is kept in a sterile environment and filled in a container, a sour milk food stored at room temperature that can be stored for a long time at room temperature can be obtained. For example, a product having a best-by date of 1 to 360 days when stored at room temperature (25 ° C.) can be obtained.
The time from the end of the filling step (the end of filling and sealing) to the start of cooling is preferably within 24 hours. If it is within 24 hours, the effect of contributing to stability is large.

[Method of preparing sour milk food (I)]
The method for preparing the sour milk food (I) is not particularly limited. A known method can be used.
For example, fermenting bacteria are added to a raw material liquid containing a dairy raw material and fermented to form a milk protein card, and a stabilizer is added to one or both of the raw material liquid before fermentation and the fermented product after fermentation. , A method for obtaining sour milk food (I) can be used.

The milk raw material is a milk-derived raw material and contains at least milk protein. Known dairy ingredients used in the production of fermented milk can be used. For example, raw milk, milk, buffalo milk, goat milk, sheep milk, horse milk, defatted milk, defatted concentrated milk, defatted powdered milk, concentrated milk, whole fat powdered milk, cream, butter, butter milk, condensed milk, milky protein concentrate (WPC) ), Milk protein isolate (WPI), milk protein concentrate (MPC), miserasein concentrate (MCC), milk protein isolate (MPI) and the like. These may be used alone or in admixture of two or more.

The raw material liquid contains water in addition to the above dairy raw material. Further, other components can be contained as long as the effects of the present invention are not impaired.
Other components include, for example, sugars, sweeteners, casein hydrolysates, vegetable fats, flavors, pH regulators, vitamins, minerals, dietary fiber, fruit juices / pulp, antioxidants, colorants and the like.

The dairy raw material, water, and other components as required are mixed and dissolved to prepare a raw material liquid. The raw material liquid may be heated if necessary. For example, the temperature of the raw material liquid is preferably 10 to 85 ° C.
Before adding the fermenting bacteria to the raw material liquid, it is preferable to heat sterilize the raw material liquid. In the present specification, the heat sterilization of the raw material liquid may be referred to as "primary sterilization", and the heat sterilization of the sour milk food (I) may be referred to as "secondary sterilization". The heat sterilization conditions in the primary sterilization are preferably in the range of, for example, 90 to 145 ° C. for 15 minutes to 2 seconds. The raw material liquid may be homogenized before being heat sterilized.

As the fermenting bacterium, it is preferable to use at least lactic acid bacterium. Two or more kinds of lactic acid bacteria may be combined. In addition to lactic acid bacteria, one or more known fermenting bacteria (for example, bifidobacteria, yeast) may be used in combination.
It is preferable to use a lactic acid bacterium starter as the fermenting bacterium. For example, one or more lactic acid bacteria starters commonly used in yogurt production such as Lactobacillus bulgaricus, Lactococcus lactis, S. thermophilus and the like. Is preferably used. These starters are available from commercial products.

Fermenting bacteria are added to the raw material liquid, kept at the fermentation temperature, and fermented until the pH reaches a preset value to obtain a fermented product containing a milk protein card (fermentation step). Before adding the fermenting bacteria, it is preferable to adjust the temperature of the raw material liquid to a predetermined fermentation temperature in advance. For example, when the lactic acid bacterium starter exemplified above is used as the fermenting bacterium, the fermentation temperature is preferably 25 to 45 ° C, more preferably 35 to 43 ° C.
Since acid is produced in fermentation by lactic acid bacteria, the pH of the raw material liquid after the fermentation is started decreases with time. The ultimate pH in the fermentation step is preferably 3.8 to 4.8. The pH of the raw material liquid in the fermentation step can be adjusted by the type of fermenting bacteria, the amount added and the fermentation time.
The fermentation step can be carried out, for example, at 25 to 45 ° C. for 3 to 24 hours.
When the pH reaches the target value (reached pH), the resulting fermented product is preferably stirred or homogenized to grind the curd. It may be cooled to 10 ° C. or lower before grinding the fermented product.

As a method of incorporating the stabilizer in the sour milk food (I), when preparing the raw material solution, the stabilizer is dissolved in the raw material solution, or the stabilizer is dissolved in water in advance to prepare an aqueous solution. Examples thereof include a method of setting the state and adding it to the fermented product after fermentation.
Thus, the sour milk food (I) containing the stabilizer is obtained.

In the above description, the method of preparing the sour milk food (I) by forming a milk protein card by producing acid by fermentation has been described, but a method of adding an acid component to the raw material solution to form a milk protein card. But sour milk food (I) is obtained.
As the acid component, citric acid, lactic acid and the like can be used. When the acid component is a solid, it is preferable to dissolve it in a solvent such as water in advance before use. As the acid component, a liquid containing an acid (for example, fruit juice) may be used. The pH of the liquid containing the acid component at 25 ° C. is preferably 0.5 to 3.0, more preferably 1.0 to 2.5. If it is at least the lower limit of the above range, excessive acid aggregation is unlikely to occur, and if it is at least the upper limit, the fermentation process tends to proceed smoothly.

The acid component may be added before the stabilizer is added, after the stabilizer is added, or both may be added at the same time.
The acid component is preferably added to the raw material liquid after the primary sterilization.
For example, sour milk food (I) can be obtained by a method in which a raw material solution containing a stabilizer is first sterilized and then an acid component is added to form a milk protein card.
Alternatively, the sour milk food (I) can also be obtained by a method of primary sterilizing the raw material solution and then adding an acid component and a stabilizer to form a milk protein card.

According to the present embodiment, the physical characteristics of the sour milk food stored at room temperature are improved by providing a cooling step after heat sterilizing (secondary sterilization) the sour milk food (I) containing the stabilizer. Specifically, aggregation of milk proteins during storage is further suppressed, and morphological changes such as sedimentation and water separation are further suppressed.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to these Examples.
<Measurement method / evaluation method>
[Evaluation method of physical property stability (Measurement method of TSI value)]
For drink-type sour milk foods, the TSI value (Turbiscan Stability Index), which is an index indicating the instability of the dispersion liquid, was measured using a stability evaluation device (Product name "Turbican Tower" manufactured by Formulaction Co., Ltd.). The smaller the TSI value, the smaller the morphological changes such as sedimentation and water separation during storage, and the more stable it is.
Specifically, the measurement was performed according to the following procedure.
The temperature of the Turbiscan Tower and the measurement sample was adjusted to 25 ° C. in advance. Next, the measurement sample was collected in a sample bottle by a predetermined method, and the sample was set in the Turbiscan Tower. Under the product name "Tower Soft" of Formulaction Co., Ltd., the amount of backscattered light and transmitted light after 0 hours and 72 hours was measured with a standby time of 5 minutes, and the change width was calculated as a TSI value.

[Measurement method of water separation amount]
For drink yogurt type sour milk food, fill 45 mL in a sterile 50 mL graduated container (manufactured by STARSTEDT), store it in a heat insulator at 25 ° C for 60 days, and visually check the amount of water separated from the top. Weighed.
For soft yogurt type sour milk food, fill 200 mL in a sterile 250 mL graduated container (manufactured by STARSTEDT), store it in a heat insulator at 25 ° C or 30 ° C for a specified period, and leave water on the top. Was visually weighed.

[Measurement method of median diameter]
The median diameter of the sample is the particle size at the point where the cumulative volume distribution curve measured by the laser diffraction / scattering particle size distribution measuring device is 50%, that is, the volume-based cumulative 50% diameter (d50). The smaller the median diameter, the more the aggregation of milk proteins is suppressed and the more stable it is.
LA-950V2 (product name) manufactured by HORIBA, Ltd. was used as a laser diffraction / scattering particle size distribution measuring device.

<Raw materials>
The following raw materials were used.
Skim milk powder: Made by Morinaga Milk Industry Co., Ltd.
Cream: Milk fat content 45.5%, manufactured by Morinaga Milk Industry Co., Ltd.
Sugar: Made by Toyo Sugar Refining Co., Ltd.
Lactic acid bacterium starter: Danisco product name "YO-MIX (R) 505", a mixed culture of Streptococcus thermophilus and Lactobacillus delbrucki subspecies bulgaricus.
Gelatin: Nitta Gelatin Co., Ltd. Product name "Gelatin GAP 250MB".
Agar: Ina Food Industry Co., Ltd. Product name "Agar UP-6".
Modified starch: Matsutani Chemical Industry Co., Ltd. Product name "Farinex VA-70WM".
HM Pectin: Saneigen FFI's product name "SM-MN-2779".

[Examples 1 to 6]
Examples 1 to 6 are examples.
In this example, a drink-type fermented milk was produced as a sour milk food stored at room temperature.
With the composition of the raw material liquid shown in Table 1, raw materials other than the lactic acid bacterium starter were mixed with a mixer to prepare a raw material liquid (70 ° C.). Then, the temperature was raised and homogenized with a homogenizer (temperature 85 ° C., pressure 15 MPa at 2 seconds). The raw material liquid (85 ° C.) after the homogenization treatment was heat sterilized (primary sterilization) in a batch type sterilizer under the conditions of 90 ° C. for 10 minutes, and then the temperature was lowered to 43 ° C.
After adding the lactic acid bacterium starter to the cooled raw material solution, the mixture was kept at 41 to 45 ° C. in a tank and fermented until the pH reached 4.2, and the temperature was lowered to 10 ° C. to complete the fermentation. After that, a pre-prepared sterilized pectin solution (5 ° C.) is added, the temperature is raised to 40 ° C. with a tubular heat exchanger, homogenized with a homogenizer (pressure 15 MPa), and the milk protein card is used. Obtained sour milk food (I), which is a mixture of crushed fermented milk and a pectin solution.
The obtained sour milk food (I) (40 ° C.) was heat sterilized (secondary sterilization) at 90 ° C. for 30 seconds and then cooled to 30 ° C. to obtain sour milk food (II). The obtained dairy food (II) was aseptically filled in a container and sealed to obtain a drink yogurt (filling step). The filling temperature was 30 ° C. and the filling amount was 45 mL. Immediately after the completion of the filling process, the food was cooled in a refrigerator in which the temperature inside the refrigerator was set to a predetermined cooling temperature for a predetermined cooling time, and then transferred to a room temperature environment at room temperature of 25 ° C. to obtain a room temperature storage acid milk food. ..
Table 2 shows the cooling temperature and the cooling time in each example.
For the sour milk foods stored at room temperature obtained in each example, the TSI value was measured by the above method immediately after the completion of the filling step (0 hours later) and 72 hours after the completion of the filling step. In addition, the amount of water separation was measured by the above method. The results are shown in Table 2 (the same applies hereinafter).

[Example 7]
Example 7 is an example.
In Example 5, the drink yogurt obtained in the filling step was stored in a room temperature environment at room temperature of 25 ° C. for 12 hours, and then placed in a refrigerator to start cooling. Other than that, a sour milk food stored at room temperature was produced in the same manner as in Example 5, and the TSI value and the amount of water separation were measured.

[Example 8]
Example 8 is an example.
In Example 5, the drink yogurt obtained in the filling step was stored in a room temperature environment at room temperature of 25 ° C. for 24 hours, and then placed in a refrigerator to start cooling. Other than that, a sour milk food stored at room temperature was produced in the same manner as in Example 5, and the TSI value and the amount of water separation were measured.

[Example 9]
Example 9 is an example.
The process up to the filling step is the same as in Example 1. The obtained drink yogurt is stored in a room temperature environment at room temperature of 20 ° C. for 8 hours, then transferred to a heat insulating chamber having an internal temperature of 15 ° C. and stored for 8 hours, and then transferred to a refrigerator having an internal temperature of 10 ° C. and stored for 8 hours. Then, the food was moved to a room temperature environment of 25 ° C. to obtain a sour milk food stored at room temperature. The TSI value and the amount of water separation were measured in the same manner as in Example 1.

[Example 10]
Example 10 is a comparative example.
The process up to the filling step is the same as in Example 1. The obtained drink yogurt was stored as a sour milk food stored at room temperature in a room temperature environment of 25 ° C. without putting it in a refrigerator. The TSI value and the amount of water separation were measured in the same manner as in Example 1.

As shown in the results of Table 2, the sour milk foods stored at room temperature obtained in Examples 1 to 9 provided with the cooling step have a smaller TSI value and a smaller amount of water separation than the sour milk foods stored at room temperature in Example 10. It can be seen that the physical stability has improved.

[Example 11]
Example 11 is an example. In this example, a solid type soft yogurt that is scooped up with a spoon or the like and eaten as a sour milk food stored at room temperature was produced. Soft yogurt is fermented milk in which milk protein curds are crushed to have fluidity, and is also called agitated yogurt.
Raw materials other than the lactic acid bacterium starter were mixed with a mixer according to the formulation shown in Table 3 to prepare a raw material solution (70 ° C.). Then, the temperature was raised and homogenized with a homogenizer (temperature 85 ° C., pressure 15 MPa at 2 seconds). The raw material liquid (85 ° C.) after the homogenization treatment was heat sterilized (primary sterilization) at 100 ° C. for 60 seconds, and then the temperature was lowered to 45 ° C.
After adding the lactic acid bacterium starter to the lowered raw material solution, the mixture was kept at 43 ° C. in a tank and fermented until the pH reached 4.1, and the temperature was lowered to 10 ° C. to complete the fermentation. After that, the temperature was raised to 70 ° C. with a tubular heat exchanger, and homogenization treatment (pressure 15 MPa) was performed with a homogenizer to obtain sour milk food (I), which is fermented milk in which milk protein curds were crushed. ..
The obtained sour milk food (I) (75 ° C.) was heat sterilized (secondary sterilization) at 94 ° C. for 20 seconds and then cooled to 30 ° C. to obtain sour milk food (II). The obtained dairy food (II) was aseptically filled in a container and sealed to obtain soft yogurt (filling step). The filling temperature was 40 ° C. and the filling amount was 200 mL. Immediately after the completion of the filling step, the food was placed in a refrigerator having an internal temperature of 5 ° C. for 24 hours to cool, and then transferred to a room temperature environment of 25 ° C. to obtain a sour milk food stored at room temperature.
With respect to the obtained sour milk food stored at room temperature (stored at 25 ° C.), the median diameter and the amount of water separation were measured by the above method 24 hours after the completion of the filling step, and used as initial values.
Further, after storing the obtained sour milk food stored at room temperature at 25 ° C. for 30 days, 60 days, 90 days, and 120 days, the median diameter and the amount of water separation were measured by the above methods, respectively. These results are shown in Table 4.

[Example 12]
Example 12 is a comparative example. The process up to the filling step is the same as in Example 11. The obtained soft yogurt was stored in a room temperature environment of 25 ° C. as a sour milk food stored at room temperature without being placed in a refrigerator.
The median diameter and the amount of water separated from the sour milk food stored at room temperature after storage were measured in the same manner as in Example 11. These results are shown in Table 4.
Table 4 also shows the difference between Example 11 and Example 12 (Examples 11-12) for each measured value.

[Example 13]
Example 13 is an example. In Example 11, a sour milk food stored at room temperature was produced in the same manner as in Example 11 except that the storage temperature after the cooling step was changed to 30 ° C., and the median diameter and the amount of water separated were measured. The results are shown in Table 5.

[Example 14]
Example 14 is a comparative example. The process up to the filling step is the same as in Example 13. The obtained soft yogurt was stored in a room temperature environment at room temperature of 30 ° C. as a sour milk food stored at room temperature without being placed in a refrigerator.
The median diameter and the amount of water separated from the obtained sour milk food stored at room temperature were measured in the same manner as in Example 13. The results are shown in Table 5.
Table 5 also shows the difference between Example 13 and Example 14 (Example 13-14) for each measured value.

As shown in the results of Tables 4 and 5, the sour milk foods stored at room temperature obtained in Examples 11 and 13 provided with the cooling step were compared with the sour milk foods stored at room temperature in Examples 12 and 14, respectively, for 120 days. The median diameter is small during the storage period, and the amount of water separated is also small. That is, it was confirmed that the physical stability was improved by providing the cooling step.

Claims (6)

A method for producing a sour milk food stored at room temperature, which comprises a heat sterilization step of heat sterilizing the sour milk food containing a stabilizer and a cooling step of cooling the sour milk food to 1 to 10 ° C. after the heat sterilization step. .. The method for producing a sour milk food stored at room temperature according to claim 1, further comprising a filling step of filling the sour milk food in a container and sealing the sour milk food after the heat sterilization step and before the cooling step. The method for producing a sour milk food stored at room temperature according to claim 2, wherein the temperature of the sour milk food when it is filled in the container is 15 to 40 ° C. The method for producing a sour milk food stored at room temperature according to claim 2 or 3, wherein the period from the end of the filling step to the start of the cooling is within 24 hours. A sour milk food having a heat sterilization step of heat sterilizing the sour milk food containing a stabilizer and a cooling step of cooling the sour milk food to 1 to 10 ° C. after the heat sterilization step. Heat sterilization method. It is a method for improving the physical stability of sour milk foods stored at room temperature by heat sterilizing sour milk foods.
A sour milk storage acid having a heat sterilization step of heat sterilizing the sour milk food containing a stabilizer and a cooling step of cooling the sour milk food to 1 to 10 ° C. after the heat sterilization step. A method for improving the physical stability of dairy foods.