JP2018038357A - Method for producing fermented milk - Google Patents

Abstract

PROBLEM TO BE SOLVED: To efficiently produce fermented milk having high content of EPS.SOLUTION: A method for producing fermented milk includes a process of producing a bulk starter and a process of adding the bulk starter to raw milk and fermenting it. The process of producing the bulk starter includes a starter adding step of adding a lactic acid bacteria starter to a medium containing a milk component, a culturing step of adjusting the temperature of the medium to a culture temperature range and culturing the lactic acid bacteria starter in the medium, a cooling step of cooling the medium to a holding temperature range of 20°C or higher and 30°C or lower, lower than the culture temperature range after completing the culture of the lactic acid bacteria starter, a temperature holding step of holding the medium in the holding temperature range for 1 hour or longer, and a re-cooling step of cooling the medium to 10°C or lower after completing the temperature holding step.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a method for producing fermented milk.

  In the past, when producing fermented milk, it is first known that lactic acid bacteria starters (mother starters) are cultured in a medium for lactic acid bacteria and then subjected to intermediate fermentation to produce lactic acid bacteria starters (bulk starters) that are added directly to raw milk. It has been. And the fermented milk will be manufactured by adding the bulk starter obtained here to raw material milk, hold | maintaining and fermenting raw material milk at predetermined temperature and predetermined time.

  In addition, various methods have been proposed for the preparation of lactic acid bacteria starters and the production of fermented milk using them.

  For example, Patent Document 1 discloses a method for preparing a lactic acid bacteria starter that can exhibit high fermentation activity, and a method for producing fermented milk using a bulk starter after preparation. Specifically, in the invention described in Patent Document 1, a nonfat milk medium containing skim milk components of 10% (W / W) or more and a yeast extract of 0.2% (W / W) or more, Bulgarian bacteria and It is characterized by planting in the presence of Thermophilus bacteria, and neutralizing culture by controlling pH to 5-6.

  For example, Patent Document 2 discloses a medium for increasing the amount of extracellular polysaccharide (EPS) produced by extracellular polysaccharide-producing lactic acid bacteria, and a method for producing an extracellular polysaccharide-producing lactic acid bacterium using the medium. Has been. Specifically, in the invention described in Patent Document 2, formic acid or formate is added to skim milk or reduced skim milk, or heat treatment is performed on skim milk or reduced skim milk to form formic acid or formate. It is characterized by obtaining a culture medium for exopolysaccharide-producing lactic acid bacteria having a total concentration of 0.4 to 10 mM.

JP2011-217679A JP 2014-027925 A

  By the way, in the production of fermented milk, the lactic acid bacteria starter is cultured over several stages, transferred from the mother starter to several generations of bulk starters, and scaled up while activating the bulk starter at each stage. It is common to do. Here, in the production process (activation process) of the bulk starter, conventionally, after sterilizing the medium containing milk components, the lactic acid bacteria starter is added to the medium cooled to 30 to 50 ° C., and the temperature is maintained. In general, the culture was performed, and after completion of the culture, the medium was stored in a refrigerator (room temperature 5 ° C.). Thus, conventionally, for the purpose of prolonging the storage period of the bulk starter, the culture medium after culturing is stored in the refrigerator as soon as possible and cooled from the culture temperature range of about 30-50 ° C. to about 5 ° C. at once. Was to do.

  In the production of fermented milk, in order to cope with a rapid increase in quantity and reduce labor and electric costs, the amount of bulk starter charged in one lot is increased to reduce production days and to reduce waste loss. For this purpose, it is required to increase the usable days (number of storable days) of the bulk starter as much as possible. However, in the conventional method, since the vitality (fermentation power) of the bulk starter gradually decreases during storage in the refrigerator, the usable days are limited to about 5 days. Therefore, there is now a demand for technology that can efficiently increase the vitality of bulk starters.

  Moreover, conventionally fermented milk which increased EPS content by adding and fermenting Bulgarian bacteria (Lactobacillus delbrueckii subsp. Bulgaricus), especially Bulgarian bacteria 1073R-1 strain (L. bulgaricus 1073R-1) to raw milk. The product (yogurt product) is known. Here, in order to obtain a bulk starter with enhanced EPS productivity, it is also possible to increase the concentration of formic acid by adding formic acid or the like to the skim milk medium as in the invention described in Patent Document 2. However, the bulk starter obtained by using the technique of Patent Document 2 has a composition that is significantly different from that of a normal bulk starter, so that a new incubator (fermenter) for culturing it is required. is there. When the bulk starter obtained by using the technique of Patent Document 2 is used for fermented milk products, there is also a concern that the flavor may change greatly. Therefore, at present, there is a need for a technique for more stably increasing the EPS production capacity of a bulk starter without adding additives and the like, without changing the quality of conventional fermented milk products.

  In view of the above, the present invention provides a method for producing a bulk starter that can increase the vitality and EPS productivity of the bulk starter, and a method for producing fermented milk using the bulk starter obtained there. That is, an object of the present invention is to efficiently produce fermented milk having a high EPS content.

  As a result of intensive investigations on means for solving the problems of the prior art, the inventors of the present invention have added and cultured a lactic acid bacteria starter to a medium for lactic acid bacteria, and then maintained at 20 to 30 ° C. for 1 hour or longer. It was found that by cooling to 10 ° C. or lower after holding, the vitality of the bulk starter can be improved as compared with the case of cooling to 10 ° C. or lower at once after the completion of the culture. The inventors have found that fermented milk having a high EPS content can be efficiently obtained by using the bulk starter thus obtained. Specifically, the present invention has the following steps.

  The present invention relates to a method for producing fermented milk. The method for producing fermented milk according to the present invention includes a step of producing a bulk starter and a step of adding the bulk starter to the raw material milk for fermentation.

  In the present specification, a “bulk starter” is a lactic acid bacterium starter prepared by culturing a lactic acid bacterium starter (for example, mother starter) in a medium (solution) and adjusted through intermediate fermentation, and is added directly to the raw material of fermented milk. Say things. The “bulk starter” basically includes lactic acid bacteria and a medium solution as components. In the present specification, “lactic acid bacteria starter” is a concept including a mother starter in addition to the above-described bulk starter. In the present specification, the term “lactic acid bacteria starter” is used in the sense of an inoculum used for the production of a bulk starter. In the process of manufacturing the bulk starter, in addition to inoculating the mother starter into the medium and manufacturing the bulk starter, inoculating the bulk starter into the medium and further growing (scaling up) the lactic acid bacteria Manufacturing a bulk starter is included.

The process for producing the bulk starter includes a starter addition process, a culture process, a cooling process (corresponding to the secondary cooling process in FIG. 1), a temperature holding process, and a recooling process (the tertiary process in FIG. Equivalent to the cooling step).
In the starter addition step, a lactic acid bacteria starter (a mother starter or a bulk starter as an inoculum) is added to a medium containing milk components. In the culture process, the temperature of the medium is adjusted to a culture temperature range (for example, 35 to 55 ° C.), and the lactic acid bacteria starter is cultured in the medium. In addition, what is necessary is just to complete | finish a culture | cultivation process in the stage in which the culture medium reached predetermined | prescribed acidity (for example, 0.7 to 1.2%). In the cooling step, the cultured medium is cooled to a holding temperature range of 20 to 30 ° C., which is lower than the culture temperature range. In the temperature holding step, the medium is held in the holding temperature range for 1 hour or longer. In the recooling step, the medium is cooled to 10 ° C. or lower after the temperature holding step.

  Like the said process, in this invention, when the culture medium after completion | finish of culture | cultivation is cooled to 10 degrees C or less, the temperature maintenance process which once maintains the temperature of a culture medium for 1 hour or more in a 20-30 degreeC maintenance temperature range is inserted. In this way, the lactic acid bacteria contained in the obtained bulk starter are not cooled at a stretch to 10 ° C. or less, but a temperature maintaining step is provided between them, as demonstrated in the examples described later. Can increase the vitality of

  Furthermore, according to the present invention, it is possible to improve the EPS productivity of lactic acid bacteria contained in the bulk starter. Further, according to the present invention, it is not necessary to add a special additive, and the vitality and EPS productivity of lactic acid bacteria contained in the bulk starter can be increased by devising a method for cooling the culture medium after culturing. , The flavor and quality of conventional fermented dairy products can be stably maintained. In addition, since the existing equipment can be used in carrying out the method of the present invention, it is not necessary to make a new capital investment.

  In the present invention, the temperature holding step is preferably a step of holding the medium in the holding temperature range for 2 hours or more. Thus, the vitality of the bulk starter and the EPS productivity can be further increased by setting the holding time in the holding temperature range to 2 hours or more.

  In the present invention, the temperature holding step is preferably a step of holding the medium in the holding temperature range for 1 hour to 5 hours. If the bulk starter after culturing is kept in the holding temperature range for more than 5 hours, the vitality may be lowered. For this reason, it is preferable that the holding time in a holding temperature range is 1 to 5 hours.

  In the present invention, it is preferable that the medium is allowed to stand without being stirred during the culturing step, and the medium is stirred during the subsequent recooling step and the temperature holding step. Thus, the growth of lactic acid bacteria is promoted by allowing the medium to stand during the culturing process, and the time until the end of the culturing is shortened. The vitality of the bulk starter can be further improved by stirring the medium that has been allowed to stand and imparting low stimulation to the bulk starter.

  In the present invention, the lactic acid bacterium starter (seed fungus) preferably contains a Bulgarian bacterium. Bulgaria is a lactic acid bacterium with high EPS productivity. For this reason, in this invention, this Bulgarian bacteria can be used conveniently.

  In the present invention, the bulk starter preferably has an EPS amount of 3.0 mg / 100 g or more in fermented milk measured by the following measurement method. In particular, the EPS amount is preferably 3.1 mg / 100 g or more, and particularly preferably 3.2 mg / 100 g or more. The upper limit of the EPS amount is not particularly limited, but is 10.0 mg / 100 g, for example. Furthermore, regarding the bulk starter stored for 1 day or 7 days at a temperature of 5 ° C., the EPS amount in the fermented milk measured by the following measurement method is preferably 3.0 mg / 100 g or more.

[Method of measuring EPS amount]
Raw milk: 500.0 g, skim milk powder: 47.6 g, fresh cream: 26.3 g, sucrose: 45.0 g, tap water: 378.1 g are mixed to prepare raw milk. The obtained raw milk is sterilized by heating at 95 ° C. for 5 minutes and then cooled to 43 ° C. After inoculating raw milk with 30g of bulk starter, it is filled into a cup container (capacity: 100g, made of plastic), fermented in a fermentation room at room temperature of 43 ° C until the lactic acid acidity reaches 0.8%, then 5 ° C Allow to cool. Thereafter, the amount of EPS in the fermented milk is measured. The number of lactic acid bacteria contained in 30 g of the bulk starter is 50 to 100 × 10 ⁷ cfu / g.

  As in the present invention, when the temperature holding step is performed after the fermentation step, the EPS production amount in the fermented milk by the bulk starter can be improved as compared with the case where the temperature holding step is not performed. In particular, according to the present invention, the EPS production amount per lactic acid bacterium is improved. Thereby, fermented milk with a high EPS amount can be produced efficiently.

  This invention provides the manufacturing method of the bulk starter which improved vitality and EPS productivity, and the manufacturing method of fermented milk using this bulk starter. According to the present invention, fermented milk having a high EPS content can be produced efficiently.

FIG. 1 is a flowchart showing the steps of a method for producing fermented milk according to an embodiment of the present invention.

  Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings. This invention is not limited to the form demonstrated below, The thing suitably changed in the range obvious to those skilled in the art from the following forms is also included.

In the present specification, “deposit number: FERM...” Means a deposit number at the Patent Organism Depositary, National Institute of Advanced Industrial Science and Technology.
In the present specification, “A to B” means “A or more and B or less”.

  Drawing 1 shows each process (S1-1-S1-8) of the manufacturing method of the bulk starter concerning the present invention, and each process (S2-1-S2-6) of the manufacturing method of fermented milk. Below, it demonstrates according to the flowchart shown in FIG.

  The method for producing the bulk starter is a method for producing a bulk starter that is directly added to the raw material of fermented milk by culturing a lactic acid bacteria starter (such as a mother starter or bulk starter as the inoculum) in a medium and subjecting it to intermediate fermentation. It is. As shown in FIG. 1, the method for producing a bulk starter includes a medium adjustment step (S1-1), a heat sterilization step (S1-2), a primary cooling step (S1-3), and a starter addition step (S1- 4), a culture process (S1-5), a secondary cooling process (S1-6), a temperature holding process (S1-7), and a tertiary cooling process (S1-8).

  A culture medium adjustment process (S1-1) is a process of adjusting the culture medium for adding a lactic acid bacteria starter. The medium is a solution for culturing lactic acid bacteria starters. By adding a lactic acid bacteria starter to the medium and culturing the lactic acid bacteria starter in the medium, the number of lactic acid bacteria constituting the lactic acid bacteria starter can be increased. The medium has non-fat milk solids (SNF) of 9% by weight or more, preferably 12% by weight or more. Specifically, the non-fat milk solid content of the medium is preferably 12% by weight or more, 14% by weight or more, 15% by weight or more, 18% by weight or more, or 20% by weight or more. The upper limit of the non-fat milk solid content of the medium is not particularly limited, but is preferably 30% by weight or 25% by weight, for example. In particular, the non-fat milk solid content is preferably derived from skim milk powder. In skim milk powder, about 95% is non-fat milk solids, and most of the remainder is moisture.

  The medium is preferably composed of only non-fat milk solids and moisture. In other words, the medium contains non-fat milk solids at 9% by weight or more, preferably 12% by weight or more, and the remainder consists of moisture. In addition, it is preferable that a culture medium does not contain a yeast extract. Moreover, it is preferable that a culture medium does not contain an emulsifier. In particular, since the yeast extract is not contained in the medium for lactic acid bacteria, the flavor of fermented milk produced by adding a lactic acid bacteria starter cultured in this medium can be improved. Specifically, the medium is preferably prepared only from skim milk powder and raw water (pure water, tap water, well water, etc.).

  The heat sterilization step (S1-2) is a step of heating and sterilizing the medium adjusted in the medium adjustment step. In the heat sterilization step, the heat treatment may be performed by adjusting the heating temperature and the heating time to such an extent that germs in the raw material milk can be sterilized. In the present invention, the medium is preferably heated to 80 ° C. or higher, 90 ° C. or higher, 95 ° C. or higher, or 100 ° C. or higher. A known method can be used for the heat sterilization step. For example, in the heat sterilization process, heat treatment may be performed with a plate heat exchanger, tube heat exchanger, steam injection heating device, steam infusion heating device, energizing heating device, etc. Heat treatment may be performed.

  The primary cooling step (S1-3) is a step of cooling the medium that has become high temperature after heat sterilization to a temperature range (culture temperature range) suitable for culturing lactic acid bacteria. The culture temperature range here means a temperature at which a microorganism (such as a lactic acid bacterium) is activated to promote the growth of the microorganism. For example, the culture temperature range of lactic acid bacteria is generally 30 to 60 ° C. In this invention, it is preferable to cool the culture medium which becomes high after heat sterilization, for example to the culture | cultivation temperature range of 35-55 degreeC, and it is more preferable to cool to 40-50 degreeC. A well-known method can be used for a primary cooling process. For example, in the primary cooling step, the cooling process may be performed by a plate heat exchanger, a tube heat exchanger, a vacuum (reduced pressure) evaporative cooler, or a jacketed tank.

  The starter addition step (S1-4) is a step of adding (mixing) the lactic acid bacteria starter to the medium cooled to the culture temperature range. That is, in the starter addition step, the lactic acid bacteria starter may be added after the medium has been lowered to a predetermined temperature after the heat sterilization process, or the lactic acid bacteria starter is added while the medium has been lowered to the predetermined temperature after the heat sterilization process. May be. In the present specification, “lactic acid bacteria starter” includes a mother starter and a bulk starter. As a lactic acid bacteria starter that is an inoculum to inoculate the medium, a powdery mother starter made of only lactic acid bacteria may be used, or a bulk starter in which lactic acid bacteria are mixed in a medium solution may be used.

  In the present invention, the lactic acid bacterium starter preferably contains a Bulgarian bacterium. Here, "Bulgaria bacteria" is Lactobacillus bulgaricus (L. bulgaricus). Examples of Bulgaria bacteria include L. bulgaricus 1073R-1 strain (Lactobacillus delbruecki subspecies bulgaricus 1073R-1 strain, deposit number: FERM BP-10741) and L. bulgaricus OLL1171 strain (Lactobacillus Bacillus del Brucky Subspecies Bulgarix OLL1171 strain). At this time, at least the lactic acid bacteria preferably include the L. bulgaricus 1073R-1 strain. Moreover, it is preferable that lactic acid bacteria contain thermophilus bacteria. Here, “thermophilus” is Streptococcus thermophilus (S. thermophilus). In the present invention, in the starter addition step, a known lactic acid bacterium may be added (mixed) in addition to the Bulgarian bacterium and Thermophilus bacterium. For example, in the starter addition process, gasseri (L. gasseri), lactis (L. lactis), cremoris (L. cremoris), bifidos Bacteria (such as Bifidobacterium) may be added (mixed). In particular, in the present invention, the lactic acid bacteria starter preferably contains the L. bulgaricus 1073R-1 strain in an amount of 40 to 100% by weight or more, 50 to 90% by weight or more, or 60 to 85% by weight or more.

  The lactic acid bacteria starter is preferably added at 0.1% by weight or more with respect to the medium. Specifically, the lactic acid bacteria starter may be added at 0.1 to 10% by weight, 0.5 to 5% by weight, or 1 to 3% by weight with respect to the medium.

  The culturing step (S1-5) is a step of cultivating lactic acid bacteria contained in the lactic acid bacteria starter in a medium to proliferate the lactic acid bacteria. The cultivation of the lactic acid bacteria starter is preferably terminated with reference to the acidity of the medium. The upper limit of the culture time of the lactic acid bacteria starter is not particularly limited. For example, the culture may be terminated when the acidity of the medium reaches a predetermined value. Here, for example, the acidity at the end of the culture is preferably set to 0.7% or 0.8%, and may be set to 0.7 to 1.2%. In the present invention, the acidity (lactic acidity) of the medium is measured according to the “Testing Method for Component Standards of Milk” in the Ministerial Ordinance of Milk. Specifically, 10 mL of ion exchange water not containing carbon dioxide gas is added to 10 g of the sample at 10 mL, and then a phenolphthalein solution is added at 0.5 mL as an indicator. While adding sodium hydroxide solution (0.1 mol / L), titration was performed up to the point where the faint red color did not disappear, and the content of lactic acid per 100 g of the sample was determined from the titration of the sodium hydroxide solution. , Acidity (lactic acidity). The phenolphthalein solution is prepared by dissolving 1 g of phenolphthalein in an ethanol solution (50%) and filling up to 100 mL. The culture time of the lactic acid bacteria starter is preferably 3 hours or more, 5 hours or more, or 7 hours or more.

  Moreover, it is preferable that the temperature of a culture medium is hold | maintained at 35 degreeC or more in a culture | cultivation process. In particular, the temperature of the culture medium is preferably maintained at 35 to 55 ° C, more preferably 37 to 52 ° C, and further preferably 40 to 50 ° C.

  In the culturing step, it is preferable to leave the medium without stirring. “Standing” here means that the medium is not stirred. For example, even if the container containing the medium is moved, if the inside of the medium is not stirred, It corresponds to "Standing". In this way, by allowing the medium to stand during the culturing step, the growth of lactic acid bacteria can be promoted and the time until the end of the culturing can be shortened.

  The second cooling step (S1-6) is a step of cooling the cultured medium (that is, the medium that has reached a predetermined acidity) to a holding temperature range of 20 to 30 ° C. That is, in the secondary cooling step, the culture medium in the culture temperature range (35 to 55 ° C.) is cooled to a lower holding temperature range (20 to 30 ° C.). Although the holding temperature range here is 20-30 degreeC, it is preferable that it is 22-28 degreeC, and it is especially preferable that it is 25 degreeC (+/- 1 degreeC). In the secondary cooling process, a known method can be used in the same manner as in the primary cooling process. For example, the cooling process is performed by a plate heat exchanger, a tube heat exchanger, or a vacuum (reduced pressure) evaporative cooler. The cooling process may be performed by a tank with a jacket.

  In the secondary cooling step, it is preferable to cool the cultured medium to a predetermined temperature while stirring. The medium is preferably stirred gently, and the stirring speed is preferably 50 to 1000 rpm. In particular, the stirring speed here is preferably in the range of 50 to 500 rpm or 50 to 200 rpm.

  The temperature holding step (S1-7) is a step of holding the medium cooled to the holding temperature range (20 to 30 ° C.) for 1 hour or longer in the holding temperature range. That is, the culture medium that has been cultured needs to be stored in a refrigerator or the like and stored at a temperature of 10 ° C. or lower in order to preserve the lactic acid bacteria for a long time. However, when the culture medium in the culture temperature range (35 to 55 ° C) is cooled to the low temperature storage temperature range (less than 10 ° C) at once, the lactic acid bacteria in the culture medium are damaged by the low temperature, and the vitality of each lactic acid bacteria is increased. It is thought to weaken. Therefore, in the present invention, a temperature holding step is inserted into the medium cooling step, and the culture medium after culturing is once held in a holding temperature range of 20 to 30 ° C. for 1 hour or longer and then stored in a refrigerator or the like at 10 ° C. Cool to below. As a result, it is presumed that the vitality of each lactic acid bacterium contained in the bulk starter is increased and the EPS productivity is improved. Thereby, the tolerance with respect to the recooling after a temperature holding process can be improved.

  Thus, the holding temperature range is a temperature at which the lactic acid bacteria starter inoculated in the medium is not fermented. For this reason, it is preferable that the temperature which hold | maintains a culture medium in a temperature holding process is the range of 20-30 degreeC, and is 10 degreeC or more lower than the temperature for culture | cultivating (fermenting) a lactic acid bacteria starter. . In particular, the temperature at which the medium is maintained is preferably 12 ° C. or higher or 15 ° C. or lower than the temperature at which the lactic acid bacteria starter is cultured (fermented).

  Moreover, what is necessary is just to hold | maintain a culture medium in a holding | maintenance temperature range for 1 hour or more in a temperature holding process. The holding time is more preferably 1.5 hours or more, particularly preferably 2 hours or more, or 3 hours or more. Moreover, although the upper limit of holding time is not specifically limited, It is thought that it is preferable that it is 5 hours or less. If the medium is kept at the holding temperature range for more than 5 hours, the growth of the lactic acid bacteria starter proceeds and the acidity becomes high, and it becomes difficult to keep the quality of the resulting bulk starter constant. In the temperature holding step, the temperature of the culture medium does not have to be constant and may vary within a range of 20 to 30 ° C. However, in the temperature holding step, it is preferable to keep the temperature of the medium constant, and it is preferable to keep the temperature change of the medium within a range of ± 1 ° C.

  Further, during the temperature holding step, it is preferable that the medium is gently stirred following the secondary cooling step. In particular, it is preferable to continue stirring throughout the temperature holding step. The stirring speed in the temperature holding step may be 50 to 1000 rpm, particularly in the range of 50 to 500 rpm or 50 to 200 rpm, as in the secondary cooling step.

  A 3rd cooling process (S1-8) is a process of cooling the culture medium which passed through the temperature holding process to 10 degrees C or less. In the third cooling step, it is particularly preferable to cool the medium to 0 to 5 ° C. In the third cooling process, a known method can be used as in the second cooling process. For example, the cooling process is performed by a plate heat exchanger, a tube heat exchanger, or a vacuum (reduced pressure) evaporative cooler. The cooling process may be performed by a tank with a jacket. A bulk starter can be manufactured by performing the steps up to the third cooling step. The bulk starter (containing medium and lactic acid bacteria) that has undergone the third cooling step is stored in a large refrigerator or the like and can be stored for a long time.

  In the present invention, each step from the first cooling step (S1-3) to the third cooling step (S1-8) is performed in one cooling device having functions of cooling, heat retention and stirring. Is preferred. In the present invention, for example, a jacketed tank can be suitably used in the steps from the primary cooling step to the tertiary cooling step. The jacketed tank consists of a double-walled outer wall that can be filled with cooling water and hot water, a tank part that is surrounded by the outer wall and contains a medium for lactic acid bacteria, and a stirring blade provided inside the tank part. Have.

  In the primary cooling step, the jacketed tank stores the medium after heat sterilization in the tank part, and cools the medium to the culture temperature range by injecting cooling water into the outer wall. In the culturing process, the jacketed tank maintains the temperature of the culture medium in the culture temperature range by injecting hot water into the outer wall. In the secondary cooling step, the jacketed tank cools the culture medium to the holding temperature range by re-injecting cooling water into the outer wall. Further, in the temperature holding process, the jacketed tank releases the cooling water and makes the outer wall hollow, or injects hot water into the outer wall, thereby maintaining the temperature of the culture medium in the holding temperature range. Further, in the third cooling step, the jacketed tank cools the medium to 10 ° C. or less by injecting cooling water into the outer wall again. Thus, in the present invention, the temperature of the culture medium can be controlled using one jacketed tank. For this reason, a bulk starter can be manufactured efficiently.

  Further, all of the steps from the medium adjustment step (S1-1) to the third cooling step (S1-8) can also be performed using a jacketed tank. In this case, a jacketed tank may be used that has a heating function. Thereby, a heat sterilization process (S1-2) can also be performed in a tank with a jacket.

  In the present invention, the bulk starter is preferably stored for 4 days at a temperature of 5 ° C., and then the vitality estimation time measured by the following measurement method is preferably within 4 hours. In particular, the vitality estimation time after storage for 7 days is preferably within 3 hours and 55 minutes, particularly preferably within 3 hours and 50 minutes, or within 3 hours and 40 minutes.

[Measurement method of vitality estimation time]
Raw milk: 500.0 g, skim milk powder: 47.6 g, fresh cream: 26.3 g, sucrose: 45.0, tap water: 378.1 g are mixed to prepare raw milk. The obtained raw milk is sterilized by heating at 95 ° C. for 5 minutes and then cooled to 43 ° C. After inoculating 30g of bulk starter after storage for 7 days at a temperature of 5 ° C into raw milk, it is filled into a cup container (capacity: 100g, made of plastic), and the lactic acid acidity is 0.8% in a fermentation room at a room temperature of 43 ° C. Measure the time to reach. The number of lactic acid bacteria contained in 30 g of the bulk starter is 50 to 100 × 10 ⁷ cfu / g.

  As described above, in the method for producing a bulk starter, the culture medium after completion of the culture is not cooled to 10 ° C. or less at once, but is temporarily held at a temperature of 20 to 30 ° C. for 1 hour or more and then cooled to 10 ° C. or less. Thereby, since the lactic acid bacteria in a culture medium increase the tolerance with respect to low temperature, even if it is under low temperature of 10 degrees C or less, vitality can be maintained for a long period of time. In the specification of the present application, “energy” of the bulk starter is the ability to maintain the ability to ferment raw milk. The higher the vitality of the bulk starter, the longer the ability to ferment raw milk within a certain time can be maintained. In general, it is considered that the bulk starter preferably has a time of 4 hours or less until the fermented milk reaches an acidity of 0.8%. In the conventional bulk starter, when the low temperature storage period exceeds 7 days, the vitality is lowered and it is difficult to ferment fermented milk within 4 hours. On the other hand, since the vitality of each lactic acid bacterium is enhanced, the bulk starter obtained by the present invention is fermented within 4 hours even after being stored at a temperature of 5 ° C. for 7 days. Milk can be fermented until an acidity of 0.8% is reached. Thus, the bulk starter obtained by the present invention can sustain the ability to ferment fermented milk within 4 hours even after storage for 7 days at a low temperature of 5 ° C. In particular, according to the present invention, the vitality of each lactic acid bacterium contained in the bulk starter is increased.

  Then, the manufacturing method of fermented milk is demonstrated. The manufacturing method of fermented milk is a method of manufacturing fermented milk by fermenting raw material milk using the bulk starter obtained through the bulk starter manufacturing method (S1-1 to S1-8) described above. . As FIG. 1 shows, the manufacturing method of fermented milk is raw material milk adjustment process (S2-1), heat sterilization (S2-2), primary cooling process (S2-3), bulk starter addition process (S2). -4), fermentation step (S2-5), and secondary cooling step (S2-6).

  An example of fermented milk produced according to the present invention is yogurt. The yogurt may be a plain type, a hard type, a soft type, or a drink type. Examples of fermented milk produced according to the present invention include frozen yogurt and cheese materials. In the present invention, the fermented milk may be any of “fermented milk”, “dairy lactic acid bacteria beverage”, “lactic acid bacteria beverage” and the like defined by a Japanese ordinance of milk.

  The raw material milk adjustment step (S2-1) is a step of adjusting the raw material milk that is the basis of the fermented milk. Raw milk is also called yogurt base or yogurt mix. In the present invention, known milk can be used as raw material milk. For example, raw material milk may consist of raw milk only (raw milk is 100%). The raw milk may be prepared by mixing raw milk with skim milk powder, cream, water, and the like. In addition to these, raw milk is sterilized milk, whole milk, skim milk, whole fat concentrated milk, whole fat concentrated milk, whole fat milk powder, butter milk, salted butter, unsalted butter, whey, whey powder, Whey protein concentrate (WPC), whey protein isolate (WPI), α-La (alpha-lactalbumin), β-Lg (beta-lactoglobulin), prepared by mixing (adding) lactose There may be. In addition, raw milk may be prepared by appropriately adding pre-warmed gelatin, agar, thickener, gelling agent, stabilizer, emulsifier, sucrose, sweetener, flavor, vitamin, mineral, etc. Good. In the raw milk preparation step, it is preferable to homogenize the raw milk to atomize (pulverize) fat globules contained in the raw milk. That is, by homogenizing the raw material milk, the fat content of the raw material milk and the fermented milk can be prevented from separating and rising during the manufacturing process and after the manufacturing of the fermented milk.

  The heat sterilization step (S2-2) is a step of heating and sterilizing the medium adjusted in the raw material milk adjustment step. In the heat sterilization step, the heat treatment may be performed by adjusting the heating temperature and the heating time to such an extent that germs in the raw material milk can be sterilized. In the present invention, the raw milk is preferably heated to 80 ° C. or higher, preferably 90 ° C. or higher. A known method can be used for the heat sterilization step. In the heat sterilization process, when the yogurt is plain type, hard type or soft type, heat treatment such as high temperature short time sterilization (HTST) may be performed. Heat treatment such as sterilization treatment (UHT) may be performed. Further, for example, in the heat sterilization process, the high temperature short time sterilization process (HTST) may be a process in which the raw milk is heated to 80 ° C. to 100 ° C. for about 3 minutes to 15 minutes. ) Should just be the process heated to 110 to 150 degreeC for about 1 second-30 second.

  A primary cooling process (S2-3) is a process of cooling the raw material milk which is high temperature after heat sterilization to the temperature range (fermentation temperature range) suitable for fermentation. For example, the fermentation temperature range of lactic acid bacteria is generally 30 to 60 ° C. In this invention, it is preferable to cool the culture medium which becomes high after heat sterilization to the fermentation temperature range of 35-55 degreeC, for example, and it is more preferable to cool to 40-50 degreeC. A well-known method can be used for a primary cooling process.

  In the bulk starter addition step (S2-4), the bulk starter obtained through the bulk starter production method (S1-1 to S1-8) described above is added (mixed) to the medium cooled to the fermentation temperature range. It is a process to do. In the bulk starter addition step, the bulk starter may be added after the medium has fallen to the predetermined temperature after the heat sterilization step, or the bulk starter is added while the medium has been lowered to the predetermined temperature after the heat sterilization step. May be. The bulk starter is preferably added at 0.1% by weight or more with respect to the raw milk. Specifically, the lactic acid bacteria starter may be added at 0.1 to 10% by weight, 0.5 to 5% by weight, or 1 to 3% by weight with respect to the medium.

  A fermentation process (S2-5) is a process of fermenting raw material milk with a bulk starter. In the fermentation process, the raw material milk to which the bulk starter is added is fermented while being maintained in a fermentation temperature range (for example, 30 to 60 ° C.) to obtain fermented milk. In the present invention, a known method can be used for the fermentation step. For example, in the fermentation process, the fermentation process may be performed in a fermentation chamber or the like, and the fermentation process may be performed in a tank with a jacket. In the fermentation process, post-fermentation processing may be performed when the yogurt is a plain type or a hard type, and pre-fermentation processing may be performed when the yogurt is a soft type or a drink type. Furthermore, for example, the fermentation process may be a process of maintaining the temperature in the fermentation chamber (fermentation temperature) at about 30 ° C. to 60 ° C. and fermenting the raw milk in the fermentation chamber, or in a tank with a jacket The temperature (fermentation temperature) of this may be maintained at 30-60 degreeC, and the process which ferments raw material milk in the tank may be sufficient. Here, in the fermentation process, the conditions for fermenting the raw milk may be adjusted as appropriate, such as the fermentation temperature and the fermentation time, in consideration of the type and quantity of the raw milk and lactic acid bacteria, the flavor and texture of the fermented milk. Specifically, in the fermentation process, it is preferable that the raw milk is maintained in the fermentation temperature range for 1 hour or more. And in a fermentation process, it is preferable that the period (fermentation time) which hold | maintains raw material milk is 1 hour-12 hours, It is more preferable that it is 2 hours-8 hours, It is that it is 3 hours-5 hours. Further preferred.

  In the fermentation process, the conditions for fermenting raw milk may be adjusted as appropriate by considering the type and quantity of raw milk and lactic acid bacteria, the flavor and texture of fermented milk, and the like. Specifically, in the fermentation process, it is preferable that the lactic acid acidity reaches 0.7% or more. Furthermore, in the fermentation process, for example, when the SNF is 8.5 to 12.0%, the lactic acid acidity is preferably 0.9% or less (0.7% to 0.9%), and 0.85% or less. (0.7% to 0.85%) is more preferable, and 0.8% or less (0.7% to 0.8%) is further preferable. The acidity of the raw milk (lactic acidity) can be measured according to the “Testing Method for Component Standards of Milk” in the Ministerial Ordinance of Milk, similar to the acidity of the medium described above.

  The fermentation process may be either a post-fermentation process or a pre-fermentation process. And when performing a post-fermentation process, after filling the raw material milk with a bulk starter into the container for actually selling as a product, this raw material milk is fermented. For example, when post-fermentation treatment is performed, fermented milk (fermented milk) that is an intermediate product obtained by fermenting by, for example, leaving a container (sealed) filled with raw milk containing a bulk starter in a fermentation chamber. Card) is cooled in a re-cooling step to be described later, and fermented milk (set type yogurt, plain type yogurt) as a final product may be obtained. Moreover, when performing a pre-fermentation process, raw material milk is fermented before filling raw material milk into the container for actually selling as a product. For example, when pre-fermentation is carried out, the fermented milk (fermented milk card), which is the intermediate product, is fermented by leaving a jacketed tank filled with raw material milk, etc. Then, after cooling in the re-cooling process described later, and after mixing the pulp, vegetables, fruit juice, vegetable juice, jam, sauce, preparation, etc., it is filled into a (sealed) container and the final product What is necessary is just to obtain fermented milk (soft type yogurt, drink type yogurt).

  Moreover, when the acidity of fermented milk becomes 0.8%, the production amount of extracellular polysaccharide (EPS amount) in fermented milk is 3.0 mg / 100 g or more, 3.5 mg / 100 g or more, 4.0 mg. / 100g or more, 4.5mg / 100g or more, preferably 5.0mg / 100g or more. Here, the upper limit of the EPS amount is not particularly limited, but is 10.0 mg / 100 g, for example. That is, according to the present invention, the amount of EPS in fermented milk can also be increased efficiently.

  A secondary cooling process (S2-6) is a process of cooling fermented milk obtained by fermenting raw material milk. By performing the secondary cooling step, the progress of fermentation is suppressed. At this time, in the secondary cooling step, the fermented milk is cooled to a temperature lower than the fermentation temperature range (for example, 30 to 60 ° C.). In the present invention, a known method can be used for the secondary cooling step. Specifically, in the secondary cooling step, the fermented milk is preferably cooled to 15 ° C. or lower. And in a secondary cooling process, it is preferable that fermented milk is cooled to 1-15 degreeC, It is more preferable that it is cooled to 3-10 degreeC, It is cooled to 5-8 degreeC Further preferred. By this re-cooling process, fermented milk is cooled to a temperature suitable for edible use, thereby suppressing or preventing changes in flavor (such as acidity), texture (such as tongue touch), and physical properties (such as hardness) of fermented milk. it can.

  Moreover, in this invention, an anaerobic process can also be performed as arbitrary processes. An anaerobic process is a process which mixes inert gas, such as nitrogen, with raw material milk or fermented milk, and makes it anaerobic state. In the present invention, a known method can be used for the anaerobic process. For example, in the anaerobic process, an inert gas is mixed (injected) into raw milk and anaerobic treatment is performed, or the headspace in a container filled with fermented milk and the headspace in a tank filled with fermented milk are not allowed. By filling (filling) the active gas and performing anaerobic treatment, the oxygen present in these is removed or reduced. By this anaerobic process, oxygen contained in the raw milk is removed or reduced, and oxidation of lipids and proteins contained in the raw milk is suppressed or prevented, or the activity of lactic acid bacteria is promoted. For example, as an inert gas, a rare gas such as helium, neon, argon, or xenon can be used in addition to nitrogen. Specifically, in the anaerobic process, the dissolved oxygen concentration (DO) of raw milk and fermented milk is preferably reduced to 5 ppm or less, more preferably 4 ppm or less, and further to 3 ppm or less. Preferably, it is particularly preferably reduced to 2 ppm or less. The anaerobic process can be performed at any stage of the raw milk preparation process (S2-1) to the secondary cooling process (S2-6). Further, the anaerobic process can be continuously performed in a plurality of process stages.

  Moreover, EPS content in the obtained fermented milk can be raised by utilizing the bulk starter obtained by the manufacturing method which concerns on this invention for fermentation of raw material milk. That is, in the method for producing a bulk starter according to the present invention, the medium after completion of fermentation is once held at a temperature of 20 to 30 ° C. for 1 hour or more and then cooled to 10 ° C. or less. When fermented milk is produced using the bulk starter thus obtained, lactic acid bacteria are contained in the fermented milk as compared to the case of using a bulk starter obtained by cooling to 10 ° C. or less at once after the completion of fermentation. The amount of EPS to be calculated increases. In particular, some Bulgarian bacteria produce functional polysaccharides. Therefore, if the bulk starter obtained according to the present invention is used, fermented milk containing a large amount of polysaccharides and having no miscellaneous taste can be produced without using additives such as a growth promoter for lactic acid bacteria.

  Hereinafter, the present invention will be specifically described with reference to examples. However, the present invention is not limited to the following examples, and various improvements based on known methods can be added.

<Example 1> Confirmation of vitality improvement of bulk starter In Example 1, in the production of a bulk starter, the medium after completion of cultivation of lactic acid bacteria was once held at a temperature of 20 to 30 ° C for 1 hour or more and then cooled to 5 ° C. The difference in the vitality of the bulk starter was confirmed between the case where the culture was completed and the case where the medium after completion of the culture was cooled to 5 ° C. or less at once.

Example 1-1 of the present invention is an example having a holding temperature of 25 ° C. and a holding time of 2 hours. In Example 1-1 of the present invention, a medium was prepared by mixing skim milk powder: 100 g and tap water: 870 g in a stainless steel container, and sterilized by heating at 95 ° C. for 5 minutes, and then cooled to 40 ° C. Thereafter, the medium was inoculated with 30 g (3% by weight) of a lactic acid bacteria starter (produced by Meiji Co., Ltd., separated from “Meiji Probio Yogurt R-1”). The lactic acid bacteria starter used here was a mixed starter of Bulgarian bacteria and Thermophilus bacteria (that is, a bulk starter as an inoculum). The number of lactic acid bacteria contained in 30 g of lactic acid bacteria starter was 50 to 100 × 10 ⁷ cfu / g. The lactic acid bacteria starter was left to stand and cultured until the temperature in the medium was 40 ° C. and the lactic acid acidity reached 0.80%. The culture medium container after completion of the culture was immersed in cold water, and the culture medium was cooled to 25 ° C. with stirring and maintained at this temperature for 2 hours (temperature maintaining step). Then, the culture medium was cooled to 5 ° C. to produce a bulk starter according to Example 1-1 of the present invention. Thereafter, the bulk starter was stored at a temperature of 5 ° C. for 7 days.

  About the bulk starter of Example 1-1 stored at a temperature of 5 ° C. for 7 days, the vitality was measured according to the above-described [Measurement method of vitality estimation time], and the vitality estimation time was 3 hours and 38 minutes. .

  Example 1-2 of the present invention is an example having a holding temperature of 20 ° C. and a holding time of 2 hours. In Example 1-2 of the present invention, a bulk starter was produced under the same conditions as Example 1-1, except that the temperature of the medium in the temperature holding step was 20 ° C. The bulk starter of Example 1-2 stored for 7 days at a temperature of 5 ° C. had an estimated activity time of 3 hours and 48 minutes.

  Example 1-3 of the present invention is an example having a holding temperature of 30 ° C. and a holding time of 2 hours. In Example 1-3 of the present invention, a bulk starter was produced under the same conditions as Example 1-1, except that the temperature of the medium in the temperature holding step was 30 ° C. The bulk starter of Example 1-3 stored for 7 days at a temperature of 5 ° C. had an estimated activity of 3 hours and 48 minutes.

  Example 1-4 of the present invention is an example having a holding temperature of 25 ° C. and a holding time of 1 hour. In Example 1-4 of the present invention, a bulk starter was produced under the same conditions as in Example 1-1, except that the temperature holding time in the temperature holding step was 1 hour. The bulk starter of Example 1-4 stored for 8 days and 14 days at a temperature of 5 ° C. had a vitality estimation time of 3 hours 56 minutes and 3 hours 53 minutes, respectively. From this, the bulk starter of Example 1-4 has sufficient production capacity of fermented milk, even when it is stored for 14 days after its manufacture, as it is stored for 8 days. confirmed.

  Example 1-5 of the present invention is an example having a holding temperature of 25 ° C. and a holding time of 5 hours. In Example 1-5 of the present invention, a bulk starter was produced under the same conditions as in Example 1-1, except that the temperature holding time in the temperature holding step was 5 hours. The bulk starter of Example 1-5 stored for 7 days at a temperature of 5 ° C. had a vitality estimation time of 3 hours and 38 minutes.

  On the other hand, in Comparative Example 1 of the present invention, the culture medium container after culturing was immersed in cold water, and the culture medium was cooled to 5 ° C. at a stretch while stirring to produce a bulk starter. In Comparative Example 1, a bulk starter was produced under the same conditions as in Example 1-1 except that the temperature holding step was not performed. About the bulk starter of the comparative example 1, when the vitality estimation time was measured at the stage of storing at a temperature of 5 ° C. for 7 days, 8 days, and 14 days, 4 hours 12 minutes, 4 hours 8 minutes, and 4 hours 41, respectively. Minutes. Thus, in the comparative example 1 which did not perform the temperature holding process, the vitality estimation time already exceeded 4 hours in the storage period of 7 days, and exceeded 4.5 hours after 15 days.

  From the test results in Example 1 above, the culture medium after culturing is kept at 20-30 ° C. for 1-5 hours and then cooled to 5 ° C., compared with the case where it is cooled to 5 ° C. at once after the cultivation is completed. It was confirmed that the vitality of the obtained bulk starter was improved.

The above-described Examples 1-1 to 1-5 and Comparative Example 1 of the present invention are summarized as follows.

<Example 2> Confirmation of EPS productivity improvement of bulk starter In Example 2, in the production of a bulk starter, the medium after completion of cultivation of lactic acid bacteria was once held at a temperature of 20 to 30 ° C for 1 hour or more and then 5 ° C. The difference in EPS production capacity of the bulk starter was confirmed between the case where the medium was cooled to 5 ° C. and the case where the medium after the fermentation was cooled to 5 ° C. or less at once.

Example 2-1 of the present invention is an example having a holding temperature of 25 ° C. and a holding time of 2 hours. In Example 2-1 of the present invention, a medium was prepared by mixing skim milk powder: 100 g and tap water: 870 g in a stainless steel container, sterilized by heating at 95 ° C. for 5 minutes, and then cooled to 40 ° C. Thereafter, the medium was inoculated with 30 g (3% by weight) of a lactic acid bacteria starter (produced by Meiji Co., Ltd., separated from “Meiji Probio Yogurt R-1”). The lactic acid bacteria starter used here was a starter including Bulgarian bacteria 1073R-1 strain (deposit number: FERM BP-10741). The number of lactic acid bacteria in the lactic acid bacteria starter was 50-100 × 10 ⁷ cfu / g. The lactic acid bacteria starter was left to stand and cultured until the temperature in the medium was 40 ° C. and the lactic acid acidity reached 0.80%. The medium container after culturing the lactic acid bacteria was immersed in cold water, cooled to 25 ° C. while stirring the medium, and maintained at this temperature for 2 hours (temperature maintaining step). Then, the culture medium was cooled to 5 ° C. to produce a bulk starter according to Example 2-1 of the present invention. Thereafter, the bulk starter was stored at a temperature of 5 ° C. for 1 day and 7 days.

  Regarding the bulk starter of Example 2-1 stored at a temperature of 5 ° C. for 1 day and 7 days, the amount of EPS was measured according to the above-mentioned [Method of measuring EPS amount], and the value was 2.9 mg / 100 g, respectively. And 3.2 mg / 100 g.

Here, the EPS amount was analyzed by the following procedure.
1) Protein removal by TCA is performed on 1 g of fermented milk (yogurt).
2) Remove impurities with a MicroSpin S-400HR column.
3) The amount of EPS is analyzed by HPLC (High performance liquid chromatography) using a gel filtration column. In addition, Ultimate3000 (Thermo Fisher Scientific) was used as an HPLC analyzer.

  Example 2-2 of the present invention is an example having a holding temperature of 20 ° C. and a holding time of 2 hours. In Example 2-2 of the present invention, a bulk starter was produced under the same conditions as in Example 2-1, except that the temperature of the medium in the temperature holding step was 20 ° C. For the bulk starter of Example 2-2 stored at a temperature of 5 ° C. for 1 day and 7 days, the EPS amount was measured according to the above [Method for measuring EPS amount], and the value was 3.0 mg / 100 g and It was 3.0 mg / 100 g.

  Example 2-3 of the present invention is an example having a holding temperature of 30 ° C. and a holding time of 2 hours. In Example 2-3 of the present invention, a bulk starter was produced under the same conditions as in Example 2-1, except that the temperature of the medium in the temperature holding step was 30 ° C. Regarding the bulk starter of Example 2-3 stored at a temperature of 5 ° C. for 1 day and 7 days, the EPS amount was measured according to the above [Method for measuring EPS amount], and the value was 3.2 mg / 100 g and It was 3.0 mg / 100 g.

  Example 2-4 of the present invention is an example having a holding temperature of 25 ° C. and a holding time of 1 hour. In Example 2-4 of the present invention, a bulk starter was produced under the same conditions as in Example 2-1, except that the temperature holding time in the temperature holding step was 1 hour. Regarding the bulk starter of Example 2-4 stored at a temperature of 5 ° C. for 1 day, 7 days, and 14 days, the amount of EPS was measured according to the above [Method for measuring EPS amount]. 8 mg / 100 g, 3.0 mg / 100 g, and 2.7 mg / 100 g.

  Example 2-5 of the present invention is an example having a holding temperature of 25 ° C. and a holding time of 5 hours. In Example 2-5 of the present invention, a bulk starter was produced under the same conditions as in Example 2-1, except that the temperature holding time in the temperature holding step was 5 hours. Regarding the bulk starter of Example 2-5 which was stored at a temperature of 5 ° C. for 1 day and 7 days, the amount of EPS was measured according to the above [Method for measuring amount of EPS]. The value was 3.1 mg / 100 g, It was 3.3 mg / 100 g.

  On the other hand, in Comparative Example 2 of the present invention, the container of the medium after fermentation was immersed in cold water, and the medium was cooled to 5 ° C. all at once while stirring to produce a bulk starter. In Comparative Example 2, a bulk starter was produced under the same conditions as in Example 2-1, except that the temperature holding step was not performed. Regarding the bulk starter of Comparative Example 2 stored at a temperature of 5 ° C. for 1 day, 7 days, and 14 days, the EPS amount was measured according to the above [Method for measuring EPS amount]. 100 g, 2.3 mg / 100 g, and 2.0 mg / 100 g. Thus, in Comparative Example 2 in which the temperature holding step was not performed, the EPS amount was clearly reduced as compared with Example 2-1 to Example 2-5.

  From the test results in Example 2 above, the fermentation-finished medium is maintained at 20-30 ° C. for 1-5 hours, and then cooled to 5 ° C., compared with the case of cooling to 5 ° C. at once after the fermentation is completed. Thus, it was confirmed that the EPS production capacity of the obtained bulk starter was improved.

The above Examples 2-1 to 2-5 and Comparative Example 2 of the present invention are summarized as follows.

  As mentioned above, in this specification, in order to express the content of the present invention, the embodiment and the example of the present invention were described, referring to drawings. However, the present invention is not limited to the above-described embodiments and examples, but includes modifications and improvements obvious to those skilled in the art based on the matters described in this specification.

  The present invention relates to a method for producing fermented milk. Therefore, the present invention can be suitably used in the manufacturing industry of fermented milk such as yogurt.

Claims (7)

Manufacturing a bulk starter;
A method for producing fermented milk comprising the step of adding the bulk starter to raw milk for fermentation,
The process of manufacturing the bulk starter includes:
A starter addition step of adding a lactic acid bacteria starter to a medium containing milk components;
Adjusting the temperature of the medium to a culture temperature range, and culturing the lactic acid bacteria starter in the medium; and
A cooling step of cooling the medium to a holding temperature range of 20 ° C. or higher and 30 ° C. or lower, which is lower than the culture temperature range, after culturing the lactic acid bacteria starter;
A temperature holding step for holding the medium in the holding temperature range for 1 hour or more;
A re-cooling step of cooling the medium to 10 ° C. or less after the temperature holding step is completed. The method for producing fermented milk according to claim 1, wherein the temperature holding step is a step of holding the medium in the holding temperature range for 2 hours or more. The method for producing fermented milk according to claim 1, wherein the temperature holding step is a step of holding the medium in the holding temperature range for 1 hour or more and 5 hours or less. The method for producing fermented milk according to claim 1, wherein the medium is stirred during the temperature holding step. During the culturing step, the medium is allowed to stand without agitation,
The method for producing fermented milk according to claim 1, wherein the medium is stirred during the recooling step and the temperature holding step. The method for producing fermented milk according to claim 1, wherein the lactic acid bacterium starter includes a Bulgarian bacterium. The method for producing fermented milk according to claim 6, wherein the bulk starter has an EPS amount of 3.0 mg / 100 g or more in fermented milk measured by the following measuring method.
[Method of measuring EPS amount]
Raw milk: 500.0 g, skim milk powder: 47.6 g, fresh cream: 26.3 g, sucrose: 45.0 g, tap water: 378.1 g are mixed to prepare raw milk. The obtained raw milk is sterilized by heating at 95 ° C. for 5 minutes and then cooled to 43 ° C. After inoculating raw milk with 30g of bulk starter, it is filled into a cup container (capacity: 100g, made of plastic), fermented in a fermentation room at room temperature of 43 ° C until the lactic acid acidity reaches 0.8%, then 5 ° C Allow to cool. Thereafter, the amount of EPS in the fermented milk is measured. The number of lactic acid bacteria contained in 30 g of the bulk starter is 50 to 100 × 10 ⁷ cfu / g.

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