WO2016009950A1 - Fermented milk having enhanced lactobacillus bulgaricus growth and method for producing same - Google Patents

Abstract

[Problem] To enhance the growth of Lactobacillus bulgaricus and minimize the growth of Streptococcus thermophilus relative to each other. [Solution] A method for producing fermented milk, said method comprising: a sterilization step in which a starting milk is sterilized; a cooling step in which the starting milk is cooled after heat sterilization thereof; a starter addition step in which a lactic acid bacteria starter containing Lactobacillus bulgaricus and Streptococcus thermophiles is added to the starting milk during the cooling step or after the cooling step in order to obtain a fermented milk base material; a low temperature holding step in which, after the starter addition step, the fermented milk base material is held at a temperature that is lower than a temperature that promotes the fermentation thereof; a heating step in which, after the low temperature holding step, the fermented milk base material is heated to a temperature that promotes the fermentation thereof; and a fermentation step in which, after the heating step, the fermented milk base material is fermented in order to obtain fermented milk.

Description

Fermented milk with enhanced growth of Bulgarian bacteria and method for producing the same

The present invention relates to a method for producing fermented milk containing Bulgarian bacteria and Thermophilus bacteria. Examples of this fermented milk are plain type, hard type, soft type and drink type yogurt. The present invention also relates to a fermented milk containing Bulgarian bacteria and Thermophilus bacteria.

For some time, yogurt obtained by inoculating raw milk (yogurt mix) as a starter with two types of lactic acid bacteria, Bulgarian bacteria and Thermophilus bacteria, has been known. In such yogurt, the ratio of the number of Bulgarian bacteria to Thermophilus bacteria is generally about 1: 4 to 1: 5, and there are overwhelmingly large numbers of Thermofilus bacteria compared to Bulgarian bacteria. is doing.

By the way, there is a product in which a standard (for example, 10 ⁶ cfu / g or more after storage for 16 days) is set for the number of Bulgarian bacteria in yogurt. In addition, there is a product characterized in that yogurt contains a predetermined amount of functional polysaccharide (EPS) produced by Bulgarian bacteria. In such a yogurt, it is desired to increase the number of Bulgarian bacteria in the production process.

In this regard, a method for promoting the growth of lactic acid bacteria by adding a pH buffering agent to raw milk (yogurt mix), fermented milk base (yogurt base), medium, etc. has been known. ing.

For example, Patent Document 1 discloses a method for producing low-fat yogurt in which oleic acid or the like is added to a fermented milk base material (yogurt base). According to Patent Document 1, it is proposed that the survival of lactic acid bacteria in low-fat yogurt can be improved by using oleic acid or the like.

For example, Patent Document 2 discloses a method for producing a fermented food, in which a guava leaf extract is added to a fermented milk base material (yogurt base). According to Patent Document 2, it is proposed that the use of guava leaf extract can improve the survival of lactic acid bacteria in fermented foods because it functions as a survival improver for lactic acid bacteria and a growth promoter for lactic acid bacteria. ing.

For example, Patent Document 3 discloses a fermented food production method in which gum arabic is added to a fermented milk base (yogurt base). According to Patent Document 3, it is proposed that the survival rate of bifidobacteria during storage of fermented food can be increased by using gum arabic.

JP 2001-045968 A JP 2010-119305 A Special table 2010-505390

However, if the growth promoter of lactic acid bacteria such as pH buffer is added to the raw milk or fermented milk base material to increase the number of lactic acid bacteria as in the above-mentioned prior art, this growth promoter causes As a result, there was a problem that miscellaneous taste, bitterness, acidity, etc. different from the original flavor of milk occurred. For this reason, when using the conventional lactic acid bacteria growth promoter, it is difficult to adjust the flavor of the fermented milk.

The addition of lactic acid bacteria growth promoters can increase the number of lactic acid bacteria in fermented milk, but in fermented milk containing both Bulgarian and thermophilus bacteria, conventional lactic acid bacteria growth promoters can be added. If used, the number of both Bulgarian and Thermophilus bacteria will increase together. In other words, when a conventional lactic acid bacteria growth promoter is used, the growth of Bulgarian bacteria and Thermophilus bacteria are promoted together, and thus it is difficult to relatively promote the growth of Bulgarian bacteria. It was difficult to promote the production of polysaccharides derived from bacteria. On the other hand, in the yogurt as described above, there is a product that only promotes the growth of Bulgarian bacteria and does not need to promote the growth of Thermophilus bacteria during the production process. At this time, it is possible to increase the production amount of polysaccharides derived from Bulgaria bacteria by increasing the ratio of the number of Bulgaria bacteria in fermented milk containing both Bulgaria bacteria and Thermophilus bacteria.

Therefore, at present, in fermented milk containing Bulgarian bacteria and Thermophilus bacteria, the growth of Bulgarian bacteria is relatively promoted and the growth of Thermophilus bacteria is relatively promoted without using additives such as lactic acid bacteria growth promoters. There is a need for a technique that can be effectively controlled.

Therefore, the inventors of the present invention, as a result of intensive studies on the means for solving the conventional problems, added a lactic acid bacteria starter containing Bulgarian bacteria and Thermophilus bacteria to the raw milk after (heated) sterilization, and before the fermentation It was found that the growth of Bulgarian bacteria was promoted and the growth of Thermophilus was suppressed unexpectedly by carrying out the process of holding the fermented milk base at a low temperature. As a result, it has succeeded in relatively increasing the number of Bulgarian bacteria without using additives such as lactic acid bacteria growth promoters, and can produce fermented milk that is rich in polysaccharides and has no taste. did it. The inventors of the present invention have conceived that the problems of the prior art can be solved based on the above knowledge, and have completed the present invention.

The 1st side surface of this invention is related with the manufacturing method of fermented milk.
The method for producing fermented milk of the present invention includes a sterilization step, a cooling step, a starter addition step, a low temperature holding step, a heating step, and a fermentation step.
A sterilization process is a process of sterilizing (heating) raw material milk.
The cooling step is a step of cooling the raw milk after the sterilization step.
The starter addition step is a step of obtaining a fermented milk base material by adding a lactic acid bacteria starter containing Bulgaria bacteria and Thermophilus bacteria to the raw material milk during or after the cooling process.
The low temperature holding step is a step of holding the fermented milk base material after the starter addition step at a temperature lower than the fermentation promoting temperature. The fermentation promotion temperature means a temperature at which lactic acid bacteria are activated and fermentation of the fermented milk base is promoted. At a temperature lower than the fermentation promoting temperature, the fermented milk base does not ferment at all, and the fermented milk base may be slightly fermented.
A heating process is a process of heating the fermented milk base material after a low-temperature holding process to fermentation promotion temperature.
A fermentation process is a process of fermenting the fermented milk base material after a heating process, and obtaining fermented milk.

As described above, in the present invention, the fermented milk base material to which the lactic acid bacteria starter including Bulgarian bacteria and Thermophilus bacteria is added is set to intentionally keep at low temperature. And after keeping a fermented milk base material low temperature for a predetermined period, this fermented milk base material is heated and fermentation is accelerated | stimulated. In this way, in the process of producing fermented milk, the number of Bulgarian bacteria contained in fermented milk is relatively increased unexpectedly by performing an operation of holding the fermented milk base material at a low temperature. Results were obtained. In other words, comparing the fermented milk with the low-temperature holding process (low-temperature holding process) with the fermented milk without the low-temperature holding process (low-temperature holding process), However, the number of Thermophilus bacteria was smaller in the former than in the latter. For this reason, it can be said that it succeeded in suppressing the proliferation of Thermophilus bacteria, promoting the proliferation of Bulgaria bacteria by performing the low temperature maintenance process. Some Bulgarian bacteria produce functional polysaccharides (EPS: Exopolysaccharide). Therefore, according to the present invention, a fermented milk containing a large amount of polysaccharides and having no miscellaneous taste is produced by relatively increasing the number of bacterial bacteria without using an additive such as a growth promoter for lactic acid bacteria. be able to.

In this invention, it is preferable that a cooling process is a process of cooling raw material milk to 15 degrees C or less. More specifically, the raw material milk is preferably cooled to 1 ° C. or higher and 15 ° C. or lower.
The low temperature holding step is preferably a step of holding the fermented milk base material at a low temperature at 15 ° C. or lower for a period of 1 day or longer. More specifically, the fermented milk base material is preferably held at 5 ° C. or higher and 15 ° C. or lower for 1 day (24 hours) to 10 days (240 hours).

As described above, by keeping the fermented milk base material at a low temperature at 15 ° C. or lower for 1 day or more before the fermentation step, the activities of Bulgarian bacteria and Thermophilus bacteria can be appropriately adjusted, which is unexpected. In addition, the number of Bulgarian bacteria contained in fermented milk increased relatively, and the number of Thermofilus bacteria decreased relatively. In other words, by performing the low-temperature holding process, the growth rate of Bulgaria bacteria was improved and the growth rate of Thermophilus bacteria was reduced in the fermentation process. By performing such an operation, it becomes possible to adjust the ratio of the number of Bulgarian bacteria and Thermophilus bacteria contained in the fermented milk to a preferable value.

In the present invention, the heating step is preferably a step of heating the fermented milk base material to a fermentation acceleration temperature of 30 ° C. or higher and 50 ° C. or lower.

As described above, when the temperature of the fermented milk base material is 15 ° C. or lower after the low temperature holding step, the fermented milk base material is set in the heating step by setting the fermentation promoting temperature to 30 ° C. or higher and 50 ° C. or lower. Is heated at least at 15 ° C. or higher. In this way, by giving a large temperature difference of 15 ° C. or more between the temperature at which the temperature is maintained and the temperature at which the fermentation is performed, the growth rate of Thermophilus is reduced while improving the growth rate of Bulgarian bacteria in the fermentation process. Can be made.

In the present invention, it is preferable to further include an anaerobic process in which an inert gas is injected into the fermented milk base material to an anaerobic state at least in the low temperature holding process. In addition, an anaerobic process may be performed not only at a low temperature maintenance process but at a cooling process, a starter addition process, a heating process, and a fermentation process.

As mentioned above, while keeping the fermented milk base material at a low temperature, the fermented milk base material is anaerobically mixed with an inert gas to suppress oxidation of the fermented milk base material during the low temperature holding process. The activity of Bulgarian bacteria and Thermophilus bacteria can be moderately adjusted while preventing. For this reason, in the fermentation process after the low-temperature holding process, Bulgarian bacteria and Thermophilus bacteria, particularly Bulgarian bacteria are preferably activated, and for example, fermented milk containing a large amount of polysaccharides can be produced.

In the present invention, the numerical value of the ratio of the number of Bulgarian bacteria to the number of Thermophilus bacteria contained in the fermented milk base material before the low-temperature holding step (the number of Bulgarian bacteria / the number of Thermophilus bacteria) is α. . In the present invention, the numerical value of the ratio of the number of Bulgarian bacteria to the number of Thermophilus bacteria contained in the fermented milk (the number of Bulgarian bacteria / the number of Thermophilus bacteria) is β. In this case, it is preferable that the numerical value of β / α is 1.1 or more.

In the present invention, the ratio of the number of Bulgarian bacteria to the number of Thermophilus bacteria (the number of Bulgarian bacteria / the number of Thermophilus bacteria) in the fermented milk base material before the low temperature holding step is 0.01 or more and 0. .5 or less is preferable. In contrast, in the present invention, in the fermented milk, the ratio of the number of Bulgarian bacteria to the number of Thermophilus bacteria (the number of Bulgarian bacteria / the number of Thermophilus bacteria) is 0.6 or more. It is preferable.

As described above, according to the method for producing fermented milk of the present invention, even when a lactic acid bacteria starter having a small ratio of the number of Bulgarian bacteria to the number of Thermophilus bacteria is used, the number of Thermofilus bacteria is Fermented milk with a large ratio of the number of Bulgarian bacteria to the above can be produced. That is, according to the method for producing fermented milk of the present invention, it is possible to dramatically improve the ratio of the number of Bulgarian bacteria to Thermophilus bacteria.

In the present invention, it is preferable not to add a growth promoter for lactic acid bacteria. Lactic acid bacteria growth promoters are additives other than milk derived for the purpose of promoting the growth of lactic acid bacteria. For example, conventionally known additives such as pH buffer, oleic acid, guava leaf extract, gum arabic and the like can be mentioned as growth promoters for lactic acid bacteria.

As described above, according to the method for producing fermented milk of the present invention, fermented milk having a large number of Bulgarian bacteria can be produced without adding a lactic acid bacteria growth promoter. As a result, according to the present invention, it is possible to prevent the occurrence of miscellaneous taste, bitterness, acidity and the like derived from this growth promoter, and fermented milk can be produced without impairing the original flavor of milk. .

In the present invention, the fermentation process may be a process of obtaining fermented milk by fermenting after filling the fermented milk base material in a container. By performing so-called post-fermentation treatment, so-called set-type yogurt and plain-type yogurt can be produced.

The second aspect of the present invention relates to fermented milk.
The fermented milk of the present invention is obtained by adding a lactic acid bacteria starter containing Bulgarian bacteria and Thermophilus bacteria to raw milk to obtain a fermented milk base material, and then fermenting the fermented milk base material. Here, the value of the ratio of the number of Bulgarian bacteria to the number of Thermophilus bacteria contained in the fermented milk base material is α. The ratio of the number of Bulgarian bacteria to the number of Thermophilus bacteria contained in the fermented milk is defined as β. In this case, the fermented milk of the present invention has a β / α value of 1.1 or more.

As described above, in the present invention, it is possible to increase the production amount of polysaccharides derived from Bulgaria bacteria by increasing the ratio of the number of Bulgaria bacteria to the number of Thermophilus bacteria. In particular, in the present invention, it is preferable that the ratio of the number of Bulgarian bacteria to the number of Thermophilus bacteria is increased without adding a lactic acid bacteria growth promoter.

The fermented milk of the present invention preferably has a lactic acidity (acidity) of 0.9% or less.

As described above, in the present invention, the fermentation time is not lengthened, and the fermented milk has a moderate lactic acidity of 0.9% or less and maintains the mildness of the flavor and texture of the fermented milk. However, the ratio of the number of Bulgarian bacteria can be increased. In general, if the lactic acid acidity is increased until the fermentation time is increased and the lactic acid acidity of the fermented milk exceeds 0.9%, the production of polysaccharides derived from Bulgarian bacteria can be sufficiently increased. Conceivable. However, if the fermentation time is lengthened and the lactic acid content of the fermented milk is increased, the mildness of the flavor and the smoothness of the texture may be impaired. Therefore, the fermented milk of the present invention preferably has a β / α value of 1.1 or more under the condition that the lactic acid acidity is 0.9% or less.

The fermented milk of the present invention preferably has a polysaccharide concentration of 5 mg / 100 g or more.

As described above, in the present invention, it is possible to increase the concentration of polysaccharides derived from Bulgaria bacteria by increasing the ratio of the number of Bulgaria bacteria. In this invention, the density | concentration of the polysaccharide derived from a Bulgaria bacterium increases, and smoothness increases rather than the case where the polysaccharide derived from a Thermophilus bacterium increases.

According to the present invention, in fermented milk containing Bulgarian bacteria and Thermophilus bacteria, the growth of Bulgarian bacteria is relatively promoted without the use of additives such as lactic acid bacteria growth promoters. Can be suppressed.

FIG. 1 is a flowchart showing an embodiment of the manufacturing method of the present invention.

Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings. However, the present invention is not limited to the embodiments described below, and includes those appropriately modified by those skilled in the art from the following embodiments.

In the present specification, “raw milk (yogurt mix)” is a material of fermented milk, and consists of raw milk only, or prepared by mixing raw milk with skim milk powder, cream, water, etc. It means the previous state. The “fermented milk base (yogurt base)” is a material of fermented milk obtained by adding lactic acid bacteria starter to raw material milk, and means a state before the fermentation process. Moreover, "fermented milk" means the product obtained after fermentation process obtained by fermenting a fermented milk base material.
In this specification, “A to B” means “A to B”.

The present invention relates to fermented milk and a method for producing the same. An example of fermented milk is yogurt. The yogurt may be a plain type, a hard type, a soft type, or a drink type. Moreover, it is possible to use the fermented milk manufactured by this invention as a material of frozen yogurt. It is also possible to use the fermented milk produced according to the present invention as a cheese material. 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 an ordinance of milk.

FIG. 1 is a flowchart showing each step of a manufacturing method according to an embodiment of the present invention. As shown in FIG. 1, the method for producing fermented milk according to the present invention includes a raw material milk preparation step (step S1), a sterilization step (step S2), a cooling step (step S3), a starter addition step (step S4), It is preferable to include a low temperature holding process (step S5), a heating process (step S6), a fermentation process (step S7), and a recooling process (step S8). Moreover, it is preferable that the manufacturing method of this invention includes an anaerobic process (step S9) further.

As shown in FIG. 1, in producing fermented milk, a raw material milk preparation step (step S1) is first performed. The raw material milk preparation step is a step of preparing raw material milk as a material for fermented milk. Raw milk is also called yogurt mix. In the present invention, known milk can be used as raw material milk. For example, the raw milk may be composed only of raw milk (raw milk 100%). The raw milk may be prepared by mixing raw milk with skim milk powder, cream, water, and the like. In addition, raw milk includes sterilized milk, full fat milk, skim milk, full fat concentrated milk, nonfat concentrated milk, full fat powdered milk, 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), lactose and the like may be added. In addition, gelatin, agar, thickener, gelling agent, stabilizer, emulsifier, sucrose, sweetener, fragrance, vitamin, mineral, and the like may be appropriately added to the raw milk. In the raw material milk preparation step, it is preferable to finely sulfurize (pulverize) fat globules and the like contained in the raw material milk by a homogenization step of homogenizing the raw material milk. By this homogenization process, it is possible to suppress or prevent the raw milk, the fermented milk base material, and the fat content of the fermented milk from separating or rising during the manufacturing process or after the manufacturing of the fermented milk.

The sterilization step (step S2) is performed after the raw material milk preparation step. The sterilization process is a process of sterilizing raw milk by heat treatment or the like. For example, in the sterilization process, the heating temperature and the heating time may be adjusted so as to sterilize the germs of the raw material milk. In the present invention, a known method can be used for the sterilization step. For example, in the sterilization process, heat treatment may be performed with a plate heat exchanger, a tube heat exchanger, a steam injection heating device, a steam infusion heating device, an energizing heating device, etc., and heating is performed with a jacketed tank. Processing may be performed. In the sterilization process, when the yogurt is plain type, hard type or soft type, heat treatment such as high temperature short time sterilization treatment (HTST) may be performed. When yogurt is drink type, ultra high temperature sterilization is performed. Heat treatment such as treatment (UHT) may be performed. Further, for example, in the sterilization process, the high temperature short time sterilization process (HTST) may be a process in which the raw material milk is heated to 80 ° C. to 100 ° C. for about 3 minutes to 15 minutes. May be any treatment that heats to 110 ° C. to 150 ° C. for about 1 to 30 seconds.

The cooling process (step S3) is performed after the sterilization process. The cooling step is a step of cooling the raw material milk that has been heat-treated to a predetermined temperature. In the cooling step, the raw milk is cooled to a temperature lower than the fermentation promotion temperature (for example, 30 ° C. to 50 ° C.). In the present invention, a known method can be used for the cooling step. For example, in the cooling process, 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. Specifically, it is preferable that the raw milk is cooled to 15 ° C. or lower in the cooling step. In the cooling step, the raw milk is preferably cooled to 1 to 15 ° C., more preferably 3 to 10 ° C., and preferably 5 to 8 ° C. Further preferred.

In the cooling process, when the sterilization process is a heat treatment, it is preferable to rapidly cool the raw milk at about 100 ° C. whose temperature has increased in the sterilization process to a low temperature (15 ° C. or less). And, for example, in the cooling process, when the sterilization process is a heat treatment, the time for cooling the raw milk of about 100 ° C. whose temperature has increased in the sterilization process to 15 ° C. is preferably within 10 minutes, It is more preferably within minutes, more preferably within 1 minute, and particularly preferably within 30 seconds. By this cooling step, it is possible to suppress or prevent the protein from being denatured or the sugar from being browned in the raw material milk.

The starter addition process (step S4) is performed after the cooling process or during the cooling process. The starter addition step is a step of obtaining a fermented milk base material by adding (mixing) lactic acid bacteria starter to raw material milk. That is, the lactic acid bacteria starter may be added after the raw milk is lowered to a predetermined temperature after the sterilization process, or the lactic acid bacteria starter is added while the raw milk is lowered to the predetermined temperature after the sterilization process. Also good. In the present invention, a known method can be used for the starter addition step. However, in the present invention, the lactic acid bacteria starter includes at least Bulgarian bacteria and Thermophilus bacteria. That is, "Bulgaria" is Lactobacillus bulgaricus (L. bulgaricus) and "Thermophyllus" is Streptococcus thermophilus (S.t hermophilus). In the present invention, a known lactic acid bacterium may be added (mixed) in addition to the Bulgarian bacterium and Thermophilus bacterium in the starter addition step. For example, in the starter addition process, gasseri (L. gasseri), lactis (L. lactis), cremollis (L. Bacteria (such as Bifidobacterium) may be added (mixed). The lactic acid bacteria starter is preferably composed of only Bulgarian bacteria and Thermophilus bacteria as lactic acid bacteria. On the other hand, the amount of lactic acid bacteria starter added may be any quantity used in known fermented milk production methods, for example, preferably 0.1 to 5% by weight, and 0.5 to 4% by weight. More preferably, it is 1 to 3% by weight.

In the starter addition step, the number of bacteria (viable cell count) of Bulgarian bacteria and Thermophilus bacteria contained in the lactic acid bacteria starter may be a numerical value adopted in a known method for producing fermented milk. For example, the ratio of the number of Bulgarian bacteria and the number of Thermophilus bacteria contained in the lactic acid bacteria starter is generally 1: 4 to 1: 5. Specifically, in the starter addition step, the ratio of the number of Bulgarian bacteria when the number of Thermophilus bacteria contained in the lactic acid bacteria starter is 1 (standard) (the number of Bulgarian bacteria / the number of Thermophilus bacteria) The number) may be 0.01 to 0.8, preferably 0.05 to 0.7, more preferably 0.1 to 0.5, and 0.2 to 0.4. More preferably. On the other hand, in the starter addition step, the number of Bulgarian and Thermofilus bacteria contained in the lactic acid bacteria starter (viable cell count) can include a larger number of Bulgarian bacteria than the number of Thermofilus bacteria in advance. . For example, the ratio of the number of Bulgarian bacteria to the number of Thermophilus bacteria contained in the lactic acid bacteria starter may be 1.0 to 5.0 or 1.5 to 4.0. The number of lactic acid bacteria may be measured according to a known method.

The low temperature holding step (step S5) is performed after the starter addition step. The low temperature holding step is a step of holding the fermented milk base to which the lactic acid bacteria starter is added at a temperature lower than the fermentation promoting temperature (for example, 30 ° C. to 50 ° C.) for a predetermined period. For example, in the low temperature holding process, since the fermented milk base material is cooled to 15 ° C. or lower in the cooling process, it may be held as it is at 15 ° C. or lower. However, even if the temperature of the fermented milk base material rises between the cooling step and the low temperature holding step, there is no problem as long as the temperature is kept lower than the fermentation promoting temperature (for example, 30 ° C. to 50 ° C.). . In the present invention, a known method can be used for the low temperature holding step. For example, in the low temperature holding process, the low temperature holding process may be performed by a tank with a jacket. Specifically, it is preferable that the fermented milk base material is kept at a low temperature of 15 ° C. or lower in the low temperature holding step. In the low temperature holding step, the fermented milk base material is preferably held at a low temperature of 1 ° C. to 20 ° C., more preferably at a low temperature of 3 ° C. to 15 ° C., and a low temperature of 5 ° C. to 10 ° C. More preferably, it is retained. Further, specifically, in the low temperature holding step, the fermented milk base material is preferably held in a low temperature state for one day or longer. In the low temperature holding step, the period of holding the fermented milk base material is preferably 1 day (24 hours) to 10 days (240 hours), and 2 days (48 hours) to 8 days (192 hours). More preferably, it is 3 days (72 hours) to 6 days (144 hours).

The warming step (step S6) is performed after the low temperature holding step. The heating step is a step of heating the fermented milk base material that has been subjected to the low-temperature holding treatment to a fermentation acceleration temperature (for example, 30 ° C. to 50 ° C.). Here, the fermentation acceleration temperature means a temperature at which microorganisms (such as lactic acid bacteria) are activated and fermentation of the fermented milk base proceeds or is promoted. In the present invention, a known method can be used for the heating step. For example, in the heating step, heat treatment may be performed using a plate heat exchanger, a tube heat exchanger, or the like, or heat treatment may be performed using a tank with a jacket. For example, 30 to 50 ° C. is generally used as a fermentation promoting temperature for lactic acid bacteria. In addition, specifically, in a heating process, it is preferable that the fermented milk base material is heated to 30 degreeC or more. Furthermore, in the heating step, the fermented milk base material is preferably heated to 30 ° C. to 50 ° C., more preferably 33 ° C. to 47 ° C., and it is heated to 35 ° C. to 44 ° C. More preferably, it is warm.

In the warming process, the fermented milk base of about 10 ° C. whose temperature has been lowered in the low temperature holding process is heated to a fermentation promoting temperature (for example, 30 ° C. to 50 ° C.) for a predetermined time (in a relatively short time). Is preferred. And, for example, in the heating step, the time for heating the fermented milk base of about 10 ° C. whose temperature has been lowered in the low temperature holding step to the fermentation accelerating temperature (eg, 30 ° C. to 50 ° C.) is within 1 hour. Preferably, it is within 30 minutes, more preferably within 10 minutes, and particularly preferably within 1 minute. By this heating step, it is possible to efficiently suppress the growth of Thermophilus bacteria while efficiently promoting the growth of Bulgaria bacteria on the fermented milk base material. In the warming step, the fermented milk base material at about 10 ° C. whose temperature has been lowered in the low temperature holding step is moved to the fermentation chamber set at a room temperature of about 30 ° C. to 50 ° C. as it is, and gradually moved in the fermentation chamber. Heating treatment can also be performed while raising the temperature. However, as a result, the time required for the heating process may be greatly extended, and it becomes difficult to efficiently produce fermented milk in a short time.

The fermentation process (step S7) is performed after the heating process. In the fermentation process, a fermented milk base material heated to a fermentation promoting temperature (for example, 30 ° C. to 50 ° C.) is fermented while being maintained at the fermentation promoting temperature (for example, 30 ° C. to 50 ° C.). It is a process to obtain. 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. Further, for example, in the fermentation process, the temperature in the fermentation chamber (fermentation temperature) may be maintained at 30 ° C. to 50 ° C. and the fermented milk base material may be fermented in the fermentation chamber. (Fermentation temperature) may be maintained at 30 ° C. to 50 ° C., and the fermented milk base material may be fermented in the tank. Here, in the fermentation process, the conditions for fermenting the fermented milk base material can be adjusted as appropriate, such as the fermentation temperature and fermentation time, taking into account the type and quantity of raw milk and lactic acid bacteria, the flavor and texture of the fermented milk, etc. Good. Specifically, in the fermentation process, the fermented milk base material is preferably held at 30 ° C. or higher. Further, in the fermentation process, the fermented milk base material is preferably maintained at 30 ° C. to 50 ° C., more preferably at 33 ° C. to 47 ° C., and at 35 ° C. to 44 ° C. More preferably. Moreover, specifically, in a fermentation process, it is preferable that the fermented milk base material is hold | maintained in the state of fermentation promotion temperature in 1 hour or more. In the fermentation process, the period for holding the fermented milk base material (fermentation time) is preferably 1 hour to 12 hours, more preferably 2 hours to 8 hours, and 3 hours to 5 hours. More preferably.

In the fermentation process, the conditions for fermenting the fermented milk base material can be adjusted as appropriate by adjusting the lactic acidity (acidity), pH, etc., taking into consideration the type and quantity of raw milk and lactic acid bacteria, the flavor and texture of the fermented milk, etc. Good. Specifically, in the fermentation process, it is preferable that the lactic acid acidity reaches 0.7% or more. Furthermore, in the fermentation process, when the post-fermentation treatment is performed when the yogurt is a plain type or a hard type, the lactic acid acidity is preferably 0.9% or less (0.7% to 0.9%), 0.85% or less (0.7% to 0.85%) is more preferable, 0.8% or less (0.7% to 0.8%) is more preferable, and yogurt is a soft type When the pre-fermentation treatment is performed in the case of a drink type or the like, the lactic acid acidity is preferably 1.2% or less (0.7% to 1.2%), and 1.1% or less (0.7% To 1.1%), more preferably 1.0% or less (0.7% to 1.0%). At this time, as described above, the fermented milk base material is preferably held at the fermentation promoting temperature.

In the present specification, the acidity (lactic acid acidity) can be 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 a sample, 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. , Lactic acid acidity. The phenolphthalein solution is prepared by dissolving 1 g of phenolphthalein in an ethanol solution (50%) and filling up to 100 ml.

The fermentation process may be either post-fermentation treatment or pre-fermentation treatment. And when performing a post-fermentation process, after fermenting milk base material is filled into the container for actually selling as a product, fermented milk base material is fermented. For example, when post-fermentation treatment is performed, fermented milk (fermented milk card) that is an intermediate product obtained by fermenting a container (sealed) filled with a fermented milk base material by leaving it in a fermentation chamber or the like Is cooled in a re-cooling step 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, before filling a fermented milk base material into the container for actually selling as a product, fermented milk base material is fermented. For example, when pre-fermentation is carried out, the fermented milk (fermented milk card), which is the intermediate product obtained by fermenting by leaving a tank with a jacket filled with a fermented milk base, for example, is crushed or finely divided. After cooling, it is cooled in the re-cooling process described later, and if necessary, after mixing pulp, vegetables, fruit juice, vegetable juice, jam, sauce, preparation, etc., it is filled into a (sealed) container, and finally What is necessary is just to obtain fermented milk (soft type yogurt, drink type yogurt) which is a product.

In this embodiment, the container used for the post-fermentation process includes all containers that can be filled with fermented milk. For example, fermented milk may be a container made of plastic, paper, glass, metal, earthenware, or a composite material thereof. Fermented milk may be filled in a container having an opening on the top, fermented or coagulated, the container may be covered, a plastic shrink film, a light-shielding film (for example, a metal foil laminate) Each container may be covered with a film, a metal thin film layer film, a black or dark color ink coating film). You may use the said container, the said film, etc. in combination of 2 or more types. Fermented milk is coated with a light-shielding film after filling into PET bottles and bottles, and sealed with a light-shielding film after filling into a paper container or light-shielding plastic container from the viewpoint of suppressing flavor deterioration due to light transmission and oxygen transmission. It is preferable to use a light-shielding lid after sealing with a plastic shrink film.

In the fermentation process, it is possible to produce a large amount of polysaccharides by suppressing the growth of Thermophilus bacteria while promoting the growth of Bulgarian bacteria that produce functional polysaccharides. In other words, in the present invention, fermented milk that is rich in polysaccharides and not rich in taste is obtained by relatively increasing the number of bacterial bacteria without using additives such as growth promoters for lactic acid bacteria in the fermentation process. Can be manufactured. At this time, when the lactic acid acidity is 0.9% or less (any of 0.7% to 0.9%), the concentration of the polysaccharide in the fermented milk is preferably 5 mg / 100 g or more, and 5.5 mg / 100 g or more is more preferable, and 6 mg / 100 g or more is more preferable. For example, when the lactic acid acidity is 0.85% or less (any of 0.7% to 0.85%), the polysaccharide concentration in the fermented milk is preferably 5 mg / 100 g or more. It is more preferably 5 mg / 100 g or more, and further preferably 6 mg / 100 g or more. For example, when the lactic acid acidity is 0.8% or less (any of 0.7% to 0.8%), the polysaccharide concentration in the fermented milk is preferably 5 mg / 100 g or more. It is more preferably 5 mg / 100 g or more, and further preferably 6 mg / 100 g or more.

The recooling step (step S8) is performed after the fermentation step. The recooling step is a step of cooling the fermented milk obtained in the fermentation step. In the recooling process, the progress of fermentation is suppressed. At this time, in the recooling step, the fermented milk is cooled to a temperature lower than the fermentation promoting temperature (for example, 30 ° C. to 50 ° C.). In the present invention, a known method can be used for the recooling step. For example, in the recooling process, the recooling process may be performed in a refrigerator room or a freezer room, and the recooling process may be performed in a plate heat exchanger, a tube heat exchanger, or a tank with a jacket. Specifically, it is preferable that the fermented milk is cooled to 15 ° C. or lower in the recooling step. In the recooling step, the fermented milk is preferably cooled to 1 to 15 ° C, more preferably 3 to 10 ° C, and 5 to 8 ° C. Is more preferable. 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.

An anaerobic process (step S9) is an arbitrary process. An anaerobic process is a process which mixes inert gas, such as nitrogen, with raw material milk, fermented milk base material, and fermented milk, and makes it an anaerobic state. In the present invention, a known method can be used for the anaerobic process. For example, in the anaerobic process, the raw milk and fermented milk base material is mixed (injected) with an inert gas for anaerobic treatment, or the headspace in a container filled with fermented milk, in a tank filled with fermented milk The oxygen present in these headspaces is removed or reduced by filling the headspace with an inert gas and performing anaerobic treatment. 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, fermented milk base material, and fermented milk is preferably reduced to 5 ppm or less, more preferably 4 ppm or less, and 3 ppm or less. It is more preferable to reduce it, and it is particularly preferable to reduce it to 2 ppm or less.

The anaerobic process may be performed at any stage including the raw material milk preparation process and the sterilization process, and as shown in FIG. 1, it may be performed at any stage after the heat sterilization process. Good. Further, the anaerobic process can be continuously performed in a plurality of process stages. In the present invention, the anaerobic process is preferably performed at least in a low temperature holding process and / or a starter addition process. Moreover, in this invention, it is preferable to perform an anaerobic process at a heating process and / or a fermentation process. And, in addition to reducing the concentration of dissolved oxygen in the fermented milk base material by mixing an inert gas such as nitrogen into the fermented milk base material (which has been kept at a low temperature) in the low temperature holding step and / or the starter addition step, An inert gas such as nitrogen is mixed into the fermented milk base material (heated) in the heating step and / or fermentation step to reduce the dissolved oxygen concentration of the fermented milk base material. It is more preferable to fill the head space in the container filled with the substrate (sealed) with an inert gas. As described above, in the present invention, the fermented milk base is kept at a low temperature for a relatively long period of time (for example, 1 day or more). At this time, by performing anaerobic treatment, the flavor and quality of the fermented milk base material should be maintained well, and the activities of Bulgarian bacteria and thermophilus bacteria contained in the fermented milk base material should be appropriately managed. Can do. When fermented milk base material is fermented after being kept at a low temperature by this anaerobic process, Bulgarian bacteria and Thermophilus bacteria, in particular, Bulgarian bacteria are suitably activated, and fermented milk containing a large amount of polysaccharides can be obtained.

As described above, in the present invention, the fermented milk produced through each processing step has a relatively large number of Bulgarian bacteria (viable bacteria number). That is, in the production method of the present invention, the fermented milk base material to which a lactic acid bacteria starter containing Bulgarian bacteria and Thermophilus bacteria is added is intentionally set to be kept at a low temperature for a long time (predetermined period). Then, the fermented milk base material kept at a low temperature for the predetermined period is heated to promote fermentation. Thus, in the process of producing fermented milk, it was confirmed that the number of Bulgarian bacteria contained in fermented milk unexpectedly increases by performing an operation to hold the fermented milk base material at a low temperature. It was done. In other words, comparing the fermented milk with the low-temperature holding process (low-temperature holding process) with the fermented milk without the low-temperature holding process (low-temperature holding process), However, the number of Thermophilus bacteria was smaller in the former than in the latter. For this reason, it can be said that it succeeded in suppressing the proliferation of Thermophilus bacteria, promoting the proliferation of Bulgaria bacteria by performing the low temperature maintenance process. Some Bulgarian bacteria produce functional polysaccharides (EPS: Exopolysaccharide). Therefore, according to the present invention, a fermented milk containing a large amount of polysaccharides and having no miscellaneous taste is produced by relatively increasing the number of bacterial bacteria without using an additive such as a growth promoter for lactic acid bacteria. be able to.

In the present invention, the ratio of the number of Bulgarian bacteria when the number of Thermophilus bacteria contained in the fermented milk base material before the low-temperature holding step (step S5) is 1 (reference) (the number of Bulgarian bacteria / thermo The value of the number of Filus bacteria is α. Here, the value of α is the number of thermophilus bacteria contained immediately after the starter addition step (step S4) (specifically, the fermented milk base material within 1 hour after adding the lactic acid bacteria starter to the raw milk). It is preferable to obtain from the number and the number of Bulgarian bacteria. The ratio of the number of Bulgarian bacteria when the number of Thermophilus bacteria contained in the fermented milk after the fermentation process (step S7) is 1 (standard) (the number of Bulgarian bacteria / the number of Thermofilus bacteria) ) Is β. Here, the numerical value of β is the number of thermophilus bacteria contained in fermented milk immediately after the recooling step (step S8) (specifically, fermented milk within 1 hour after recooling) and Bulgarian bacteria. It is preferable to obtain from the number of bacteria. In this case, according to the present invention, the numerical value of β / α can be 1.1 or more. In this case, according to the present invention, the numerical value of β / α is preferably 1.2 or more, more preferably 1.5 or more, and further preferably 2.0 or more. , 2.5 or more, particularly preferably 3.0 or more. In this case, according to the present invention, the upper limit of the numerical value of β / α is not particularly limited, but may be 20.0, for example. Thus, according to the present invention, the ratio of the number of Bulgarian bacteria to the number of Thermophilus bacteria can be dramatically improved. That is, according to the present invention, it is possible to relatively promote the growth of Bulgarian bacteria and relatively suppress the growth of Thermophilus bacteria.

In the present invention, for example, when the ratio (α) of the number of Bulgarian bacteria to the number of Thermophilus bacteria contained in the fermented milk base material before the low-temperature holding step is 0.01 to 0.5, According to the invention, the ratio (β) of the number of Bulgarian bacteria to the number of Thermophilus bacteria contained in the fermented milk after the fermentation process can be 0.6 or more. Here, the ratio of the number of Bulgarian bacteria to the number of Thermophilus bacteria contained in the fermented milk base material before the low temperature holding step is determined by the fermented milk base material (specifically, in the raw milk immediately after the starter addition step). It is preferable to obtain from the number of Thermophilus bacteria and the number of Bulgarian bacteria contained in the fermented milk base material (within 1 hour after adding the lactic acid bacteria starter). Further, the ratio of the number of Bulgarian bacteria to the number of Thermophilus bacteria contained in the fermented milk after the fermentation process is 1% after the recooling process (step S8). It is preferable to determine from the number of thermophilus bacteria and the number of Bulgarian bacteria contained in the fermented milk within a period of time. In this case, according to the present invention, the ratio of the number of Bulgarian bacteria to the number of Thermophilus bacteria contained in the fermented milk is preferably 0.65 or more, more preferably 0.7 or more. Is more preferably 0.8 or more, particularly preferably 0.9 or more, and most preferably 1.0 or more. In this case, according to the present invention, the upper limit of the ratio of the number of Bulgarian bacteria to the number of Thermophilus bacteria contained in the fermented milk is not particularly limited, but may be, for example, 5.0. . Thus, according to the present invention, at the stage of the fermented milk base, even if the number of Bulgarian bacteria is less than half of the number of the Thermophilus bacteria, finally, at the stage of fermented milk, the Bulgarian bacteria It is possible to obtain fermented milk in which the number of bacteria is equal to or higher than the number of thermophilus bacteria.

The present invention also relates to a method for promoting the growth of Bulgaria bacteria, a method for suppressing the growth of Thermophilus bacteria, a method for improving the ratio of the number of Bulgarian bacteria to the number of Thermophilus bacteria, and the like. That is, the present invention provides a sterilization process for sterilizing raw milk, a cooling process for cooling the raw milk after the sterilization process, and a Bulgarian bacterium and a thermostat in the raw milk during the cooling process or after the cooling process. A starter addition step of adding a lactic acid bacteria starter containing Filus bacteria to obtain a fermented milk base, a low temperature holding step of holding the fermented milk base after the starter addition step at a temperature lower than the fermentation promoting temperature, and A heating step of heating the fermented milk base material after the low temperature holding step to the fermentation accelerating temperature; and a fermentation step of fermenting the fermented milk base material after the heating step to obtain fermented milk. It includes a method for promoting the growth of Bulgaria bacteria, a method for suppressing the growth of Thermophilus bacteria, and a method for improving the ratio of the number of Bulgarian bacteria to the number of Thermophilus bacteria. In addition, these details shall follow the manufacturing method of fermented milk of this invention, etc.

Hereinafter, the present invention will be described in detail 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> Low temperature retention of fermented milk base: Raw milk: 500 g, skim milk powder: 76 g, fresh cream: 23 g, tap water: 401 g are mixed to produce raw milk (yogurt mix, non-fat milk solids (SNF ): 9.5% by weight, milk fat content: 3.0% by weight), sterilized by heating at 95 ° C. for 5 minutes, and then cooled to about 10 ° C. (8 ° C. to 12 ° C.). Lactic acid bacteria starter (produced by Meiji Co., Ltd., lactic acid bacteria isolated from Meiji Bulgaria yogurt LB81) was added (inoculated) at 2% by weight to the cooled raw material milk to obtain a fermented milk base material (yogurt base). In order to confirm the reproducibility of the experiment, the operation for producing the fermented milk base material was performed twice. For each of the first and second fermented milk bases, the number of Bulgarian bacteria and the number of Thermofilus bacteria were measured.

In the first fermented milk base, the number of Bulgarian bacteria was 0.1 × 10 ⁷ cfu / g, and the number of Thermofilus was 1.5 × 10 ⁷ cfu / g. And this bacteria count ratio (Bulgaria bacterium / thermofilus bacterium) was 0.067.
In the second fermented milk base, the number of Bulgarian bacteria was 0.3 × 10 ⁷ cfu / g, and the number of Thermofilus was 1.1 × 10 ⁷ cfu / g. And this bacteria count ratio (Bulgaria bacterium / thermofilus bacterium) was 0.273.

The fermented milk base was kept at a low temperature at 5 to 10 ° C. for 3 days (72 hours). Further, while keeping the fermented milk base material at a low temperature, nitrogen gas (N ₂ ) was injected into the fermented milk base material to make it anaerobic. Thereafter, the fermented milk base after heated to 40 ° C., a nitrogen gas (N ₂₎ was injected, and reduced dissolved oxygen concentration in the fermented milk base material (DO) to 5 ppm. After that, the fermented milk base material is filled into a cup container (capacity: 100 g, made of plastic) and left in the fermentation room (40 ° C.) for about 3 hours until the lactic acid acidity reaches 0.8%. Then, it was cooled in a refrigerator (10 ° C. or lower) to produce fermented milk (set type yogurt) [Example 1]. The operation for producing the fermented milk of Example 1 was performed twice using the first fermented milk base and the second fermented milk base. About each of Example 1 of the 1st time and the 2nd time, the number of bacteria of Bulgaria and the number of bacteria of Thermophilus were measured.

In Example 1 (fermented milk) for the first time, the number of Bulgarian bacteria was 38.5 × 10 ⁷ cfu / g, and the number of Thermophilus bacteria was 40.0 × 10 ⁷ cfu / g. And this bacteria count ratio (Bulgaria bacterium / Thermophilus bacterium) was 0.963.
In the second example 1 (fermented milk), the number of Bulgarian bacteria was 33.5 × 10 ⁷ cfu / g, and the number of Thermofilus was 38.0 × 10 ⁷ cfu / g. And this bacteria count ratio (Bulgaria bacterium / Thermophilus bacterium) was 0.882.

<Comparative example 1> Low temperature maintenance of fermented milk base material : In order to confirm the effect of keeping low temperature non- fermented milk base material, fermented milk (set type yogurt) [comparative example 1] Manufactured. The manufacturing conditions of Comparative Example 1 were the same as those of Example 1 except for the presence or absence of holding at low temperature.

That is, raw milk: 500 g, skim milk powder: 76 g, fresh cream: 23 g, tap water: 401 g are mixed, and raw material milk (yogurt mix, nonfat milk solids (SNF): 9.5% by weight, milk fat content: 3.0 wt%) was prepared, sterilized by heating at 95 ° C. for 5 minutes, and then cooled to about 10 ° C. (8 ° C. to 12 ° C.). Then, lactic acid bacteria starter (lactic acid bacteria isolated from Meiji Bulgaria, yogurt LB81) was added (inoculated) at 2% by weight to the cooled raw material milk to obtain a fermented milk base (yogurt base). In order to confirm the reproducibility of the experiment, the work of producing the fermented milk base material was performed twice. For each of the first and second fermented milk bases, the number of Bulgarian bacteria and the number of Thermofilus bacteria were measured.

In the first fermented milk base, the number of Bulgarian bacteria was 0.6 × 10 ⁷ cfu / g, and the number of Thermofilus was 2.0 × 10 ⁷ cfu / g. And this bacteria count ratio (Bulgaria bacterium / thermofilus bacterium) was 0.300.
In the second fermented milk base, the number of Bulgarian bacteria was 0.3 × 10 ⁷ cfu / g, and the number of Thermofilus was 2.2 × 10 ⁷ cfu / g. And this bacteria count ratio (Bulgaria bacterium / thermofilus bacterium) was 0.136.

Immediately after adding the lactic acid bacteria starter, this fermented milk base is heated to 40 ° C., and then nitrogen gas (N ₂ ) is injected to reduce the dissolved oxygen concentration (DO) of the fermented milk base to 5 ppm. did. After that, the fermented milk base material is filled into a cup container (capacity: 100 g, made of plastic) and left in the fermentation room (40 ° C.) for about 3 hours until the lactic acid acidity reaches 0.8%. And it cooled in the refrigerator compartment (10 degrees C or less), and fermented milk (set type yogurt) [comparative example 1] was manufactured. Using the first fermented milk base material and the second fermented milk base material, the operation for producing the fermented milk of Comparative Example 1 was performed twice. About each of Example 1 of the 1st time and the 2nd time, the number of bacteria of Bulgaria and the number of bacteria of Thermophilus were measured.

In the first comparative example 1 (fermented milk), the number of Bulgarian bacteria was 16.5 × 10 ⁷ cfu / g, and the number of Thermofilus was 91.5 × 10 ⁷ cfu / g. And this bacteria count ratio (Bulgaria bacterium / Thermophilus bacterium) was 0.180.
In the second comparative example 1 (fermented milk), the number of Bulgarian bacteria was 10.0 × 10 ⁷ cfu / g, and the number of Thermofilus was 86.0 × 10 ⁷ cfu / g. And this bacteria count ratio (Bulgaria bacteria / Thermophilus bacteria) was 0.116.

[Comparison of number of bacteria in fermented milk base]
Table 1 below shows the comparison of the numbers of Bulgarian bacteria and Thermophilus bacteria in the fermented milk base material used in Example 1 and the fermented milk base material used in Comparative Example 1.

[Comparison of number of bacteria in fermented milk]
Table 2 below shows the comparison of the numbers of Bulgarian bacteria and Thermophilus bacteria in the fermented milk of Example 1 and the fermented milk of Comparative Example 1.

In Example 1, when the bacterial count ratio (α) of the fermented milk base material and the bacterial count ratio (β) of the fermented milk base material were compared, the bacterial count ratio (β) of the fermented milk base material was The numerical value was larger than the number ratio (α) (β> α). In Example 1 for the first time, the value of β / α was 0.963 ÷ 0.067 = 14.373. In Example 2 for the second time, the value of β / α was 0.882 ÷ 0.273 = 3.230.

<Example 2> Low temperature retention of fermented milk base material: skim milk powder: 124 g, unsalted butter: 4, sugar: 54 g, tap water: 818 g are mixed, and raw milk (yogurt mix, non-fat milk solids ( SNF): 9.5% by weight, milk fat content: 3.0% by weight), sterilized by heating at 95 ° C. for 5 minutes, and then cooled to about 10 ° C. (8 ° C. to 12 ° C.). Lactic acid bacteria starter (produced by Meiji Co., Ltd., lactic acid bacteria separated from Meiji Yogurt R-1) was added (inoculated) at 2% by weight to the cooled raw material milk to obtain a fermented milk base material (yogurt base). In order to confirm the reproducibility of the experiment, the operation for producing the fermented milk base material was performed twice. For each of the first and second fermented milk bases, the number of Bulgarian bacteria and the number of Thermofilus bacteria were measured.

In the first fermented milk base, the number of Bulgarian bacteria was 0.4 × 10 ⁷ cfu / g, and the number of Thermofilus was 1.1 × 10 ⁷ cfu / g. And this bacteria count ratio (Bulgaria bacterium / Thermophilus bacterium) was 0.364.
In the second fermented milk base, the number of Bulgarian bacteria was 0.3 × 10 ⁷ cfu / g, and the number of Thermofilus was 1.1 × 10 ⁷ cfu / g. And this bacteria count ratio (Bulgaria bacterium / thermofilus bacterium) was 0.273.

The fermented milk base was kept at a low temperature at 5 to 10 ° C. for 2 days (48 hours). Further, while keeping the fermented milk base material at a low temperature, nitrogen gas (N ₂ ) was injected into the fermented milk base material to make it anaerobic. Then, after warming the fermented milk base material to 38 ° C., nitrogen (N ₂ ) was injected, and the dissolved oxygen concentration (DO) of the fermented milk base material was reduced to 3 ppm. 2 kg, made of stainless steel), left in the fermentation chamber (38 ° C.) for about 4 hours until the lactic acid acidity reached 0.8%, and then the curd of fermented milk was crushed. Then, the obtained fermented milk was filled into a cup container (capacity: 100 g, made of plastic) and cooled in a refrigerator (10 ° C. or lower) to produce fermented milk (soft type yogurt) [Example 2]. The operation for producing the fermented milk of Example 2 was performed twice using the first fermented milk base material and the second fermented milk base material. About each of Example 2 of the 1st time and the 2nd time, the number of bacteria of Bulgaria and the number of bacteria of Thermophilus were measured.

In Example 2 (fermented milk) for the first time, the number of Bulgarian bacteria was 43.0 × 10 ⁷ cfu / g, and the number of Thermofilus was 51.0 × 10 ⁷ cfu / g. And this bacteria count ratio (Bulgaria bacteria / Thermophilus bacteria) was 0.843.
In the second example 2 (fermented milk), the number of Bulgarian bacteria was 41.0 × 10 ⁷ cfu / g, and the number of Thermofilus was 46.5 × 10 ⁷ cfu / g. And this bacteria count ratio (Bulgaria bacterium / Thermophilus bacterium) was 0.882.

<Comparative example 2> Low temperature maintenance of fermented milk base material : In order to confirm the effect of keeping low temperature non- fermented milk base material, fermented milk (soft type yogurt) [comparative example 2] Manufactured. The manufacturing conditions of Comparative Example 2 were the same as those of Example 2 except for the presence or absence of holding at low temperature.

That is, skim milk powder: 124 g, unsalted butter: 4, sugar: 54 g, tap water: 818 g are mixed, and raw milk (yogurt mix, nonfat milk solids (SNF): 9.5% by weight, milk fat content) : 3.0 wt%) was prepared, sterilized by heating at 95 ° C for 5 minutes, and then cooled to about 10 ° C (8 ° C to 12 ° C). Lactic acid bacteria starter (produced by Meiji Co., Ltd., lactic acid bacteria separated from Meiji Yogurt R-1) was added (inoculated) at 2% by weight to the cooled raw material milk to obtain a fermented milk base material (yogurt base). In order to confirm the reproducibility of the experiment, the operation for producing the fermented milk base material was performed twice. For each of the first and second fermented milk bases, the number of Bulgarian bacteria and the number of Thermofilus bacteria were measured.

In the first fermented milk base, the number of Bulgarian bacteria was 0.2 × 10 ⁷ cfu / g, and the number of Thermofilus was 0.7 × 10 ⁷ cfu / g. And this bacteria count ratio (Bulgaria bacterium / Thermophilus bacterium) was 0.286.
In the second fermented milk base, the number of Bulgarian bacteria was 0.3 × 10 ⁷ cfu / g, and the number of Thermophilus was 1.3 × 10 ⁷ cfu / g. And this bacteria count ratio (Bulgaria bacterium / Thermophilus bacterium) was 0.231.

Immediately after the addition of the lactic acid bacteria starter, the fermented milk base material was heated to 38 ° C., and then nitrogen (N ₂ ) was injected to reduce the dissolved oxygen concentration (DO) of the fermented milk base material to 3 ppm. , Packed in a small vat (capacity: 2 kg, made of stainless steel), left in the fermentation chamber (38 ° C) for about 4 hours until the lactic acid acidity reached 0.8%, and then the fermented milk card Was crushed. Then, the obtained fermented milk was filled into a cup container (capacity: 100 g, made of plastic) and cooled in a refrigerator (10 ° C. or lower) to produce fermented milk (soft type yogurt) [Comparative Example 2]. The operation for producing the fermented milk of Comparative Example 2 was performed twice using the first fermented milk base material and the second fermented milk base material. About each of Example 2 of the 1st time and the 2nd time, the number of bacteria of Bulgaria and the number of bacteria of Thermophilus were measured.

In the first comparative example 2 (fermented milk), the number of Bulgarian bacteria was 28.0 × 10 ⁷ cfu / g, and the number of Thermofilus was 73.5 × 10 ⁷ cfu / g. And this bacteria count ratio (Bulgaria bacterium / Thermophilus bacterium) was 0.381.
In the second comparative example 2 (fermented milk), the number of Bulgarian bacteria was 21.5 × 10 ⁷ cfu / g, and the number of Thermofilus was 111.5 × 10 ⁷ cfu / g. And this bacteria count ratio (Bulgaria bacterium / Thermophilus bacterium) was 0.193.

[Comparison of number of bacteria in fermented milk base]
Table 3 below shows the comparison of the numbers of Bulgarian bacteria and Thermophilus bacteria in the fermented milk base material used in Example 2 and the fermented milk base material used in Comparative Example 2.

[Comparison of number of bacteria in fermented milk]
Table 4 below shows the comparison of the numbers of Bulgarian bacteria and Thermophilus bacteria in the fermented milk of Example 2 and the fermented milk of Comparative Example 2.

In Example 2, when the bacterial count ratio (α) of the fermented milk base and the bacterial count ratio (β) of the fermented milk base are compared, the bacterial count ratio (β) of the fermented milk base is The numerical value was larger than the number ratio (α) (β> α). In Example 2 for the first time, the value of β / α was 0.843 ÷ 0.364 = 2.315. In the second example 2, the value of β / α was 0.882 ÷ 0.273 = 3.230.

[Comparison of polysaccharide concentration in fermented milk]
Table 5 below shows a comparison between the concentration (production amount) of the polysaccharide contained in the fermented milk of Example 2 and the concentration (production amount) of the polysaccharide contained in the fermented milk of Comparative Example 2.

As shown in Table 5 above, the fermented milk of Example 2 had a higher polysaccharide concentration than the fermented milk of Comparative Example 2. As shown in Table 4, this result is considered to be due to the fact that the fermented milk of Example 2 has a larger number of Bulgarian bacteria than the fermented milk of Comparative Example 2.

When measuring the concentration of the polysaccharide contained in the fermented milk, the polysaccharide was separated from 100 g of fermented milk, and the polysaccharide outside the cell was quantified by the phenol-sulfuric acid method. The following steps a) to d) were carried out as a method for separating polysaccharides from fermented milk.
a) Deproteinization using trichloroacetic acid.
b) The polysaccharide is precipitated by ethanol precipitation.
c) Dialyze the polysaccharide aqueous solution using a dialysis membrane.
d) An aqueous solution on the polymer side is obtained.
However, in the steps such as deproteinization, ethanol precipitation, and dialysis, the operating conditions can be appropriately adjusted according to the lactic acid bacteria, the culture solution, the culture conditions, and the like.

As shown in Tables 1 to 4 above, in Examples 1 and 2 in which the fermented milk base material before fermentation was subjected to a low temperature holding treatment, Comparative Examples in which the fermented milk base material before fermentation was not subjected to the low temperature holding treatment Compared with 1 and 2, the number of Bulgarian bacteria increased, and the number of Thermofilus bacteria decreased. From this fact, by maintaining the fermented milk base material at a lower temperature (for example, 15 ° C. or less) than the fermentation promoting temperature (for example, 30 ° C. to 40 ° C.) before fermentation, the growth of Bulgarian bacteria is promoted, It was confirmed that the growth of Thermophilus was suppressed. On the other hand, as shown in Table 5 above, Example 2 in which the fermented milk base material before fermentation was subjected to the low-temperature holding treatment was compared with Comparative Example 2 in which the fermented milk base material prior to fermentation was not subjected to the low-temperature holding treatment. As a result, the total amount of polysaccharides contained in fermented milk increased. From this, it was confirmed that fermented milk containing a large amount of polysaccharides derived from Bulgaria bacteria can be produced by fermenting the fermented milk base material at a temperature lower than the fermentation promoting temperature before fermentation.

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

Claims (11)

1. A sterilization process to sterilize raw milk;
   A cooling step for cooling the raw milk after the sterilization step;
   A starter addition step of obtaining a fermented milk base material by adding a lactic acid bacteria starter containing Bulgaria bacteria and Thermophilus bacteria to the raw milk during the cooling step or after the cooling step;
   A low temperature holding step for holding the fermented milk base material after the starter addition step at a temperature lower than the fermentation promoting temperature;
   A heating step of heating the fermented milk base material after the low-temperature holding step to the fermentation acceleration temperature;
   Fermenting the fermented milk base material after the heating step to obtain fermented milk. A method for producing fermented milk.
2. The cooling step is a step of cooling the raw milk to 15 ° C. or less,
   The method for producing fermented milk according to claim 1, wherein the low temperature holding step is a step of holding the fermented milk base material at 15 ° C. or lower for 1 day or longer.
3. The method for producing fermented milk according to claim 1, wherein the heating step is a step of heating the fermented milk base material to a fermentation acceleration temperature of 30 ° C. or higher and 50 ° C. or lower.
4. The method for producing fermented milk according to claim 1, further comprising an anaerobic process in which an inert gas is injected into the fermented milk base material to an anaerobic state at least in the low temperature holding process.
5. The numerical value of the ratio of the number of Bulgarian bacteria to the number of the Thermophilus bacteria contained in the fermented milk base material before the low-temperature holding step is α,
   When the numerical value of the ratio of the number of Bulgarian bacteria to the number of the Thermophilus bacteria contained in the fermented milk is β,
   The method for producing fermented milk according to claim 1, wherein the numerical value of β / α is 1.1 or more.
6. The fermented milk base material before the low-temperature holding step has a ratio of the number of Bulgarian bacteria to the number of the Thermophilus bacteria of 0.01 or more and 0.5 or less,
   The method for producing fermented milk according to claim 1, wherein the fermented milk has a ratio of the number of Bulgarian bacteria to the number of the thermophilus bacteria of 0.6 or more.
7. The method for producing fermented milk according to claim 1, wherein a growth promoter for lactic acid bacteria is not added.
8. The method for producing fermented milk according to claim 1, wherein the fermentation step is a step of obtaining fermented milk by filling the fermented milk base material into a container and then fermenting the fermented milk base material.
9. Fermented milk obtained by fermenting a fermented milk base material in which lactic acid bacteria starter containing Bulgarian bacteria and Thermophilus bacteria is added to raw milk,
   The numerical value of the ratio of the number of Bulgarian bacteria to the number of the Thermophilus bacteria contained in the fermented milk base material is α,
   When the numerical value of the ratio of the number of Bulgarian bacteria to the number of the Thermophilus bacteria contained in the fermented milk is β,
   Fermented milk with a β / α value of 1.1 or more.
10. The fermented milk according to claim 9, wherein the lactic acid acidity is 0.9% or less.
11. The fermented milk of Claim 9. The density | concentration of a polysaccharide is 5 mg / 100g or more.

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