WO2013133313A1

WO2013133313A1 - Yoghurt with limited rise in acidity and method for producing same

Info

Publication number: WO2013133313A1
Application number: PCT/JP2013/056108
Authority: WO
Inventors: 内田英明; 座間沙織; 小島公実子; 大橋恵美
Original assignee: 株式会社明治
Priority date: 2012-03-07
Filing date: 2013-03-06
Publication date: 2013-09-12
Also published as: SG11201405534RA; HK1199178A1; JPWO2013133313A1; JP6317251B2; CN104159450A

Abstract

There is provided a high-palatability yoghurt in which a rise in acidity during refrigeration is limited and a suitably mild acidity is maintained while fermentation of lactic bacteria is promoted and fermentation time is reduced, and a method for producing the yoghurt. The method for producing the yoghurt includes a step for mixing a mixing starter and a monoculture liquid of Lactobacillus lactic bacteria into raw milk.

Description

Fermented milk with suppressed increase in acidity and method for producing the same

The present invention relates to fermented milk in which an increase in acidity is suppressed and a method for producing the same.

In fermented milk produced by lactic acid fermentation, live lactic acid bacteria are contained in the fermented milk (product). Therefore, when storing an actual product refrigerated, the acidity of fermented milk rises by the living lactic acid bacteria, and the problem of quality degradation arises. So far, a method for producing fermented milk using Lactococcus lactis subspecies lactis producing nisin has been disclosed for the purpose of obtaining fermented milk in which the increase in acidity during refrigerated storage is suppressed (patent document). 1). For the same purpose, fermented milk production methods using lactic acid bacteria belonging to Streptococcus thermophilus and producing antibacterial substances and low-temperature sensitive strains are also known (Patent Documents 2 and 3).

In addition, a method for producing fermented milk that suppresses an increase in acidity by using a specific lactic acid bacteria strain as a mixed starter is also known. Patent Document 4 describes that fermented milk in which an increase in lactic acid acidity is suppressed can be obtained by using a lactic acid bacterium belonging to Lactobacillus helveticus and Lactobacillus acidophilus as a starter. Furthermore, Patent Document 5 also describes a method for producing fermented milk using a strain that inhibits acid production of Lactobacillus bulgaricus and a strain that produces a viscous product of Streptococcus thermophilus.

On the other hand, some additives that promote the growth of lactic acid bacteria and bifidobacteria are known. Patent Document 6 discloses a lactic acid bacteria growth promoter and survival improver containing dead lactic acid bacteria as active ingredients, and Patent Document 7 discloses lactic acid bacteria containing κ-caseinoglyco macropeptide as active ingredients. Of the present invention have been disclosed. In addition, a growth promoter for bifidobacteria containing milk protein as an active ingredient hydrolyzed by a cell wall-localized proteolytic enzyme PrtP is also known (Patent Document 8).

Japanese Patent No. 2975148 Japanese Patent Publication No. 7-32702 Japanese Patent No. 4331309 Japanese Patent No. 3013157 Japanese Patent No. 3101143 WO2008 / 001497 Publication WO2011 / 027719 WO2009 / 150888

However, when promoting the growth of lactic acid bacteria and shortening the fermentation time, the acidity during refrigerated storage also tends to increase. Therefore, it is very difficult to suppress an increase in acidity during refrigerated storage while promoting fermentation.
Therefore, an object of the present invention is to promote fermentation of lactic acid bacteria and reduce the fermentation time while suppressing an increase in acidity during refrigerated storage and maintaining a moderately mild acidity and highly fermented fermented milk and its It is to provide a manufacturing method.

In the production of fermented milk using a mixed starter, in order to solve the above problems, the present inventors, in the production of fermented milk using a mixed starter, fermented by blending a single culture solution of Lactobacillus bulgaricus into the raw material milk. As a result of further research, we found that fermented milk with improved acidity during refrigerated storage and reduced smoothness of curd tissue was obtained. I came to let you.

That is, the present invention relates to fermented milk in which the following increase in acidity is suppressed and a method for producing the same.
[1] A method for producing fermented milk by adding a starter to raw material milk, the method comprising a step of mixing a mixed starter and a single culture of Lactobacillus lactic acid bacteria.
[2] The method according to [1], wherein the mixed starter includes a lactic acid bacterium of the genus Lactobacillus and a lactic acid bacterium of the genus Streptococcus.
[3] The method according to [1] or [2], wherein the Lactobacillus lactic acid bacterium is selected from the group consisting of Lactobacillus bulgaricus, Lactobacillus lactis, Lactobacillus acidophilus and Lactobacillus gasseri.
[4] The method according to [2] or [3], wherein the Streptococcus lactic acid bacterium is Streptococcus thermophilus or Streptococcus macedonias.
[5] The method according to any one of [2] to [4], wherein the Lactobacillus lactic acid bacterium used in the single culture is the same type of lactic acid bacterium as the Lactobacillus lactic acid bacterium used in the mixed starter.
[6] The method according to any one of [1] to [5], wherein the lactic acid bacteria in the single culture are removed and / or sterilized.
[7] The method according to any one of [1] to [6], wherein the removal treatment and / or sterilization treatment is selected from centrifugation, filtration, and heating.
[8] The method according to [7], wherein the heating of the single culture is performed together with the heating of the raw milk.
[9] The method according to any one of [1] to [8], wherein the single culture solution uses only the components contained in the raw milk as the culture components.
[10] Any one of [1] to [9], wherein the single culture solution comprises raw milk, pasteurized milk, skim milk, whole milk powder, skim milk powder, whole fat concentrated milk and / or skim concentrated milk. The method according to item.
[11] The method according to any one of [1] to [10], wherein the single culture solution is added at a concentration of 2 to 15% by weight.
[12] Fermented milk produced by the method according to any one of [1] to [11].

In the method for producing fermented milk of the present invention, by using a single culture solution of lactic acid bacteria, particularly a single culture solution obtained by removing and / or sterilizing bacterial cells, it functions as an additive for promoting fermentation (fermentation promoter). , Fermentation time can be shortened. Compared with the prior art, the preparation method is simple as a fermentation promoter and can be provided at low cost. Moreover, fermentation time can also be shortened by fermenting after a deoxygenation process.

Since the lactic acid bacteria single culture solution of the present invention contains, for example, peptides that promote fermentation such as casein degradation products, the number of bacteria such as Streptococcus thermophilus can be increased.
On the other hand, since the lactic acid bacteria single culture solution of the present invention contains lactic acid, particularly D-lactic acid, it is considered that excessive lactic acid production during the fermentation process can be suppressed. Therefore, while shortening the fermentation time, an increase in acidity during refrigerated storage can be suppressed, and fermented milk excellent in refrigerated storage stability can be provided.

Moreover, in the fermented milk obtained by the method for producing fermented milk of the present invention, the smoothness of the card structure is improved and the texture is improved. Therefore, according to the method for producing fermented milk of the present invention, moderately mild sourness can be maintained during refrigerated storage, and fermented milk having excellent quality such as texture and flavor, especially plain type yogurt can be provided. .

In addition to stabilizing the quality of fermented milk by selecting and preparing the culture components of a single culture solution of lactic acid bacteria, unlike conventional fermentation accelerators, other than “dairy products” and “milk protein” There is no need to display the ingredients on the product (fermented milk) container. Accordingly, plain type yogurt and the like can be suitably used when manufactured and sold on a commercial scale.

FIG. 1 shows the time courses of D-lactic acid and L-lactic acid during fermentation and refrigerated storage of yogurt (low PA-4 yogurt) using a low PA-4 starter. The fermentation time is 6.75 hours. FIG. 2 shows changes over time in D-lactic acid and L-lactic acid during fermentation and refrigerated storage of low PA-4 yogurt formulated with 0.05% by weight of milk peptide. The fermentation time is 3.5 hours. FIG. 3 shows changes over time in D-lactic acid and L-lactic acid during fermentation and refrigerated storage of low PA-4 yogurt formulated with 0.1% by weight of milk peptide. The fermentation time is 3.25 hours. FIG. 4 shows changes over time in D-lactic acid and L-lactic acid during fermentation and refrigerated storage of low PA-4 yogurt formulated with 5% by weight of a single culture of Bulgaria. The fermentation time is 4 hours. FIG. 5 shows changes over time in D-lactic acid and L-lactic acid during fermentation and refrigerated storage of low PA-4 yogurt formulated with 10% by weight of a single culture of Bulgaria. The fermentation time is 5 hours.

The method for producing fermented milk of the present invention includes a step of mixing a mixed starter and a single culture solution of lactic acid bacteria. Preferably, a single culture solution of Lactobacillus lactic acid bacteria is blended in the raw milk and fermented with a mixed starter.

In the present invention, “fermented milk” includes “fermented milk” defined by a ministerial ordinance (Ministerial Ordinance on Milk, etc.) regarding ingredient standards of milk and dairy products. For example, fermented milk can be raw milk, milk, special milk, raw goat milk, pasteurized goat milk, raw noodle milk, ingredient-adjusted milk, low-fat milk, non-fat milk, processed milk, etc. Milk or the like containing milk solids is fermented with lactic acid bacteria or yeast to form paste or liquid, or those frozen. These include a variety of yogurts, but typically in the present invention are plain type yogurts.

Generally, in a set type yogurt such as plain yogurt, raw milk is filled in a container and then fermented (post-fermentation). On the other hand, soft yogurt or drink yogurt is manufactured by filling fermented milk obtained by fermenting raw material milk into a container (pre-fermentation) after atomization or homogenization.

In the present invention, “raw milk” is a liquid or gel-like raw material for producing fermented milk such as yogurt, and is also called yogurt mix or fermented milk mix. In the present invention, known raw material milk can be appropriately used. The raw milk includes those before sterilization and those after sterilization. Specific ingredients (materials) of raw milk include water, raw milk, pasteurized milk, skim milk, whole milk powder, skim milk powder, whole fat concentrated milk, skim concentrated milk, butter milk, butter, cream, etc. Also good.
Further, whey protein concentrate (WPC), whey protein isolate (WPI), α-lactalbumin (α-La), β-lactoglobulin (β-Lg) and the like may be included.

In order to ferment raw milk with lactic acid, starter is mixed (mixed) with raw milk and fermented. As these starters, known starters can be used as appropriate, but lactic acid bacteria starters are preferred. Examples of lactic acid bacteria starters include, for example, Lactobacillus bulgaricus (L.bulgaricus), Streptococcus thermophilus (S.thermophilus), Lactobacillus lactis (L.lactis), Lactobacillus gasseri (L.gasseri) or Bifidobacterium In the production of fermented milk such as (Bifidobacterium), one or more of lactic acid bacteria, bifidobacteria, yeasts and the like that are generally used can be used.

In the present invention, the “mixed starter” is a starter using two or more of lactic acid bacteria, bifidobacteria, yeast and the like, and may be a mixed starter combining these lactic acid bacteria, bifidobacteria and yeast, or only from lactic acid bacteria. May be a mixed starter. As these mixed starters, mixed starters of lactic acid bacteria are preferable, mixed starters of lactic acid bacteria of the genus Lactobacillus and Streptococcus are more preferable, and mixed starters of Lactobacillus bulgaricus and Streptococcus thermophilus are more preferable. As a mixed starter of lactic acid bacteria, for example, other lactic acid bacteria or bifidobacteria such as Bifidobacterium may be added.

Lactobacillus bulgaricus, Lactobacillus lactis, Lactobacillus acidophilus, Lactobacillus gasseri are preferable for the lactic acid bacteria of the genus Lactobacillus used for the mixed starter, and Streptococcus thermophilus and Streptococcus macedonis are preferable for the lactic acid bacteria of the genus Streptococcus. preferable. In particular, it is preferable to use a mixed starter of Lactobacillus bulgaricus (Bulgaria bacterium) and Streptococcus thermophilus (thermophilus bacterium) standardized as a yogurt starter in Codex standards.

In the method for producing fermented milk of the present invention, an increase in acidity during refrigerated storage can be further suppressed by using a lactic acid bacteria starter that is slow in fermentation. Such a lactic acid bacteria starter may be a mixed starter using lactic acid bacteria that do not establish symbiosis.
Specifically, a lactic acid bacteria starter that requires a fermentation time of 5.5 hours or more until the acidity reaches 0.73% at a fermentation temperature of 43 ° C. is preferable. Lactic acid bacteria used for such a lactic acid bacteria starter include Lactobacillus bulgaricus, Lactobacillus lactis, Lactobacillus acidophilus, Lactobacillus gasseri, Streptococcus thermophilus, Streptococcus macedonis and the like.

The addition amount of the starter is preferably 1 to 8% by weight, more preferably 2 to 6% by weight, and further preferably 2 to 4% by weight. At this time, for example, the number of bacteria of Lactobacillus bulgaricus in the starter is preferably 10 ⁶ to 10 ¹² cfu / mL, more preferably 10 ⁷ to 10 ¹¹ cfu / mL, and further more preferably 10 ⁸ to 10 ¹⁰ cfu / mL. preferable. The number of Streptococcus thermophilus bacteria in the starter is preferably 10 ⁷ to 10 ¹³ cfu / mL, more preferably 10 ⁸ to 10 ¹² cfu / mL, and more preferably 10 ⁹ to 10 ¹¹ cfu / mL. As a starter addition (inoculation) method, there are a method of adding a bulk starter after preparing it from a mother starter, a direct culture method of directly adding frozen bacteria (frozen concentrated bacteria) and the like.

In the present invention, the “single culture medium” mainly means a culture liquid in which microorganisms are independently cultured without mixing a plurality of types of microorganisms. Typically, a specific bacterial cell is cultured alone. Means a simple bacterial culture.
In the method for producing fermented milk of the present invention, it is preferable to use a single culture solution of lactic acid bacteria. As the single culture solution of lactic acid bacteria, those cultured by combining lactic acid bacteria of the same genus are preferable, those cultured by combining lactic acid bacteria of the same genus / same species are more preferable, and those obtained by culturing only lactic acid bacteria of the same strain are more preferable.

In the method for producing fermented milk of the present invention, a lactic acid bacterium belonging to the genus Lactobacillus is preferred as a lactic acid bacterium to be cultivated alone, and Lactobacillus selected from Lactobacillus bulgaricus, Lactobacillus lactis, Lactobacillus acidophilus, Lactobacillus gasseri The genus lactic acid bacteria are more preferred, and Lactobacillus bulgaricus is particularly preferred.

In the method for producing fermented milk of the present invention, the component contained in the single culture solution is not particularly limited, but it is preferable to use the culture component contained in the raw milk, and it is more preferable to use only the culture component contained in the raw milk. preferable. Moreover, although a liquid form is preferable as a single culture solution, as long as the component of a culture solution is contained substantially, a solid form or a semi-solid form (gel form etc.) may be sufficient.

Ingredients for cultivating lactic acid bacteria include raw milk, pasteurized milk, skim milk, whole milk powder, skim milk powder, whole fat concentrated milk, skim concentrated milk, butter milk, butter, cream, whey protein concentrate (WPC), whey protein isolation Products (WPI), α-lactalbumin (α-La), β-lactoglobulin (β-Lg) and the like are preferably used as raw milk, and raw milk, pasteurized milk, skimmed milk, skimmed milk powder, whole milk powder, It is more preferable to use fat concentrated milk and / or defatted concentrated milk as raw material milk.
When skim milk is used, it may be an aqueous solution of 5% by weight or more of skim milk, preferably 7 to 15% by weight, more preferably 8 to 14% by weight, and further preferably 9 to 13% by weight of reduced skim milk. It is milk.

The single culture solution to be blended with the raw milk may be 1% by weight or more of the raw milk, preferably 2 to 15% by weight, more preferably 3 to 10% by weight, and further preferably 4 to 8% by weight. It is. At this time, for example, the number of Lactobacillus bulgaricus bacteria in a single culture solution is preferably 10 ⁶ to 10 ¹² cfu / mL, more preferably 10 ⁷ to 10 ¹¹ cfu / mL, and 10 ⁸ to 10 ¹⁰ cfu / mL. Is more preferable.

In the method for producing fermented milk of the present invention, the casein degradation product (peptide, amino acid, etc.) may be 0.01% by weight or more of the single culture solution as an effective component contained in the single culture solution, preferably 0. 0.02 to 0.2% by weight, more preferably 0.03 to 0.15% by weight, still more preferably 0.05 to 0.1% by weight. The D-lactic acid may be 0.05% by weight or more of the single culture medium, preferably 0.1 to 2% by weight, more preferably 0.4 to 1.6% by weight, and still more preferably 0%. .8 to 1.2% by weight.

In the method for producing fermented milk of the present invention, it is preferable to remove and / or sterilize the cells of the single culture solution. At this time, the removal and / or sterilization treatment of the cells in the single culture solution is not particularly limited, but methods such as centrifugation, filtration, heating, ultraviolet irradiation, γ-ray irradiation, and ultrasonic waves can be used, preferably , Centrifugation, filtration and heating.
Moreover, it can also carry out with the removal and / or disinfection process of the raw material milk | bacteria as a removal and / or disinfection process of a microbial cell of a single culture solution.

After the cells in the single culture solution are removed and / or sterilized, the single culture solution may contain dead cells. On the other hand, after removing and / or sterilizing the cells of the single culture, it may contain viable bacteria. In such a case, the quantity is preferably such that the viable bacteria do not function as a starter.

In the method for producing fermented milk of the present invention, the step of mixing the single culture solution and the mixed starter is not particularly limited, but it is preferable to mix the raw material milk, the single culture solution, and the mixed starter almost simultaneously before fermentation. More preferably, the mixed starter is mixed with the single culture solution. At this time, when the raw material milk and the single culture solution are mixed, the single culture solution may be added either before or after sterilizing the raw material milk, or both. When a single culture solution is added before sterilizing raw material milk, the single culture solution is also sterilized at the same time as the raw milk, so even if a single culture solution containing live bacteria is added, Can be reduced to a quantity that does not function as.

In the method for producing fermented milk of the present invention, as one aspect thereof, a deoxygenation treatment step of deoxygenating raw material milk in the fermentation step may be included.
The deoxygenation process is a process for reducing or removing oxygen present in the raw material milk. As a method for reducing the dissolved oxygen concentration (DO) of raw material milk (deoxygenation method), for example, gas replacement treatment with an inert gas such as nitrogen gas, helium, neon, argon, xenon, membrane separation treatment with an oxygen permeable membrane, low pressure Or a deaeration treatment by vacuum can be used. In the deoxygenation treatment step, the deoxygenation method may be performed so that the oxygen (dissolved oxygen concentration) present in the raw milk is, for example, 5 ppm or less, preferably 3 ppm or less, more preferably 2 ppm or less.

As the dissolved oxygen concentration of raw material milk at the start of fermentation, the lower the concentration, the better. For example, when the temperature of the raw milk is about 40 ° C., it is preferably 5 ppm or less, more preferably 3 ppm or less. Since the fermentation time is shortened by reducing the dissolved oxygen concentration in the raw milk at the start of fermentation, for example, even when the fermentation temperature is lowered, the fermentation time is relatively 3 to 7 hours. The fermentation process can be completed by setting a short time range. These deoxygenation treatment steps are also described in Japanese Patent No. 3666871, Japanese Patent No. 3644505, Japanese Patent No. 3968108, and the like.

The deoxygenation process may be carried out once or several times before the start of fermentation, such as after preparing raw milk, homogenizing and / or sterilizing raw milk, and after adding a starter to raw milk. Good. However, since it is important that the dissolved oxygen concentration is maintained in a reduced state at the start of fermentation, the deoxygenation treatment step is desirably performed immediately before, immediately after, or simultaneously with the addition of the starter.

In the method for producing fermented milk of the present invention, the fermentation temperature is preferably 30 to 50 ° C., more preferably 35 to 47 ° C., and still more preferably 40 to 45 ° C.
In addition, when the raw milk is deoxygenated in the fermentation process, it can be fermented at a relatively low temperature. Therefore, the fermentation temperature is preferably 30 to 39 ° C., more preferably 32 to 38 ° C. Preferably, it is 34 to 37 ° C.

In the method for producing fermented milk of the present invention, the fermentation time can be defined as the elapsed time until the lactic acid acidity of the fermented milk reaches about 0.7%. At this time, the lactic acid acidity can be calculated by titration using an indicator of NaOH or phenolphthalein.

In the method for producing fermented milk of the present invention, the fermentation time is preferably 2 to 24 hours, more preferably 2 to 12 hours, still more preferably 3 to 7 hours, and particularly preferably 3 to 5 hours.
When performing deoxygenation treatment, the fermentation time is preferably 2 to 20 hours, more preferably 2 to 10 hours, still more preferably 3 to 6 hours, particularly preferably 3 to 4 hours. It is.

In the method for producing fermented milk of the present invention, by adding a single culture solution to raw milk, a mild acidity is felt, the natural sweetness and smoothness of the touch are improved, and a taste that maintains a moderately mild acidity A highly fermented milk is produced. At this time, as fermented milk, it is preferable to use yogurt such as set type yogurt, soft yogurt, drink yogurt because it is easy to feel a mellow acidity, and since natural sweetness and smoothness of the texture stand out, plain yogurt etc. More preferably, it is a set type yogurt.

In the fermented milk of the present invention, an increase in acidity during refrigerated storage is suppressed. The acidity increase rate of the fermented milk of the present invention may be 5% or less, preferably 0 to 5%, more preferably 0 to 3% when stored at 10 ° C. for 7 days. More preferably, it is 0 to 2%.

In the fermented milk of the present invention, the lipid is preferably 0 to 5% by weight, more preferably 0 to 4% by weight, and still more preferably 0 to 3% by weight. The protein is preferably 7 to 15% by weight, more preferably 8 to 14% by weight, and still more preferably 9 to 13% by weight.

Hereinafter, the present invention will be further described based on examples. However, the examples are examples of the present invention and do not limit the present invention.

[Example 1] Characteristics of Lactic Acid Bacteria Starter (Low PA Starter) Slowly Progressing Fermentation Yogurt (fat content: 3.0%, SNF: 9.5%) was prepared using a mixed starter of lactic acid bacteria. Table 1 shows the fermentation time, acidity increase and pH during refrigerated storage of this yogurt. As a mixed starter for the four types of lactic acid bacteria in Table 1, a mixed starter composed of Bulgarian bacteria (Lactobacillus bulgaricus) and Thermophilus bacteria (Streptococcus thermophilus) was used.

In this example, a lactic acid bacterium starter having a fermentation time of 5.5 hours or more and a slow progress of fermentation and a tendency of small increase in acidity (Post-acidification: PA) after refrigerated storage was used. In this example, the mixed starter of these lactic acid bacteria is called a low PA starter.

[Experimental example 2] Fermentation-promoting effect of commercially available milk peptide Reduced skim milk (10% aqueous solution of skim milk powder) is blended with 0 to 0.3% of commercially available milk peptide (CE90GMM: Nippon Shinyaku Co., Ltd.). Then, the mixture was heated (90 ° C., 10 min) to prepare raw milk (medium). Various low PA starters were inoculated (added) to the raw milk at 2.0%, and fermented (43 ° C.) to a lactate degree of 0.73%. The fermentation time and acidity after refrigerated storage (14 days) are shown in Table 2.

The fermentation time was shortened in any starter by adding milk peptide to raw milk. In order to complete fermentation within 3.5 hours in a short time when using Thermophilus singly (single), low PA-1, low PA-2 and low PA-3 as starters, It was necessary to blend at 0.3% or more, and when low PA-4 was used as a starter, it was necessary to blend milk peptide at 0.1% or more.

When a thermophilus bacterium alone (single cell) is used as a starter, the acidity after refrigerated storage is 0.9 even if milk peptide is added at 0.3% and fermentation is completed in a short 3.5 hours. It was a low value of less than%. However, when low PA-1, low PA-2, low PA-3 and low PA-4 are used as starters for yogurt, milk peptides are added at 0.3% and fermentation is performed. When it was completed in 3.5 hours, the acidity after refrigerated storage was a high value of 0.9% or more, and the increase in acidity was not suppressed.
In the following examples, as a lactic acid bacteria starter, low PA-4, which was confirmed to have a fermentation promoting effect even when the amount of milk peptide added was minimal, was used.

[Example 3] Fermentation promoting effect of culture solution of lactic acid bacteria After blending various lactic acid bacteria culture solutions at 2.0% with formula milk (fat content: 3.0%, SNF: 9.5%), The raw milk (medium) was prepared by heating (90 ° C., 10 min). The raw milk was inoculated (added) with a low PA-4 starter at 2.0%, and fermented (43 ° C.) to a lactic acid content of about 0.7%.

Table 3 shows the relationship between fermentation time and acidity over time. “No addition” in the table is a control in which no culture solution of lactic acid bacteria was added.

As a culture solution of lactic acid bacteria, reduced skim milk (10% aqueous solution of skim milk powder), Bulgaria A (Bul A) or Bulgaria B (Bul B) alone (single), Thermophilus A (Thermo A) or Thermophilus Bacteria B (Thermo B) alone (single), inoculated with a mixture of Bulgaria A and Thermophilus A (complex), and with a mixture of Bulgaria B and Thermophilus B (complex) at 2.0% ( Added) and cultured (37 ° C., 16 hours). In addition, Bulgaria bacteria A and Thermophilus bacteria A were isolate | separated from Meiji Bulgaria yogurt LB81 plane, Bulgaria bacteria B and Thermophilus bacteria B were isolate | separated from Meiji Bulgaria fruit yogurt.

In the case of the Bulgarian monoculture, the fermentation-promoting effect was recognized compared to the control, but in the case of the thermophilus monoculture and in the case of the mixed culture of Bulgarian and thermophilus, compared to the control. No fermentation promoting effect was observed.

[Example 4] Fermentation promotion effect of single culture solution of Bulgaria bacteria According to Example 3, a fermentation promotion effect was recognized in the single culture solution of Bulgaria bacteria. Therefore, in order to examine the effect of the concentration of the single culture solution of Bulgaria bacteria, the single culture solution of Bulgaria bacteria is mixed at 5% or 10% and fermented to about 0.7% lactic acid (43 ° C). It was.
Table 4 shows the relationship between the fermentation time and acidity over time, and Table 5 shows the increase in acidity and pH during refrigerated storage.

When a single culture solution of Bulgaria was mixed at 5% or 10%, the fermentation time was shortened and a fermentation promoting effect was observed (Table 4). In particular, when a single culture solution of Bulgaria was mixed at 5%, the fermentation time was dramatically shortened, and a fermentation promoting effect was strongly observed.

When a single culture solution of Bulgaria was mixed at 5% or 10%, the acidity during refrigerated storage was a low value of less than 0.9%.

From the above, it was found that by adding 5% or 10% of a single culture solution of Bulgaria bacteria, it is possible to suppress an increase in acidity after refrigerated storage while accelerating the progress of fermentation.
Moreover, by fermenting after deoxygenation, the fermentation time was further shortened, the progress of the fermentation was accelerated (3.5 hours), and a plain yogurt with good storage stability was successfully prepared.

[Example 5] Fermentation promoting effect of various yogurts and inhibitory effect on increase in acidity The following five yogurts were compared in terms of fermentation promotion effect and inhibitory effect on increase in acidity, and the characteristics of each yogurt were examined.
(1) Yogurt using low PA-4 starter (low PA-4 yogurt)
(2) Low PA-4 yogurt formulated with milk peptide at 0.05% (3) Low PA-4 yogurt formulated with milk peptide at 0.1% (4) Single culture solution of Bulgarian bacteria formulated at 5% Low PA-4 yogurt (5) Low PA-4 yogurt formulated with 10% Bulgarian monoculture

FIGS. 1 to 5 show the amount of D-lactic acid produced by Bulgarian bacteria and the production of Thermophilus bacteria during fermentation (43 ° C.) and refrigerated storage (10 ° C.) in the preparation of the yogurt of (1) to (5) above. Changes over time such as the amount of L-lactic acid to be added and the total amount of lactic acid obtained by adding them together are shown.

At this time, the time when the total amount of lactic acid reached 65 mM (the lactic acid acidity was about 0.73%) was set as the fermentation time. At that point, the fermentation was terminated to prepare yogurt, and the effect of promoting fermentation was examined. Thereafter, these yogurts were stored refrigerated (10 ° C.), and the effect of suppressing the increase in acidity was examined. That is, it divided | segmented into fermentability (43 degreeC) and refrigerated storage property (10 degreeC) in preparation of yogurt, and examined each characteristic.
The amount of D-lactic acid and the amount of L-lactic acid were measured by HPLC using a chiral column.

<Fermentation promoting effect of milk peptide (fermenting time shortening effect)>
In (2) (FIG. 2) and (3) (FIG. 3) containing a milk peptide that is a growth promoting factor of thermophilus, the amount of L-lactic acid produced by thermophilus is 2.5 hours after the start of fermentation. It reached about 50 mM. In contrast, in the control (1) (FIG. 1), the amount of L-lactic acid reached about 30 mM. That is, in the cases (2) and (3) containing the milk peptide, the amount of L-lactic acid was remarkably increased as compared with the control (1).

On the other hand, in (2) and (3) containing the milk peptide, the number of thermophilus bacteria did not increase during fermentation as compared with the control (1). Therefore, it was suggested that milk peptides enhance the individual metabolic vitality (L-lactic acid production ability) of Thermophilus bacteria. That is, it was speculated that the milk peptide has a greater effect on the enhancement of its metabolic vitality than the increase in the rate of cell division of Thermophilus bacteria.

By the way, in (2) and (3) which mix | blended the milk peptide, the number of the thermophilus bacteria did not increase at the time of fermentation compared with the control (1), but the number of the bacteria of Bulgaria was 10 times at the time of fermentation. It increased in degree. In other words, it was considered that the milk peptide increased the number of Bulgarian bacteria during fermentation by enhancing the metabolic activity of Thermophilus bacteria and increasing the production of formic acid, a growth promoting factor of Bulgarian bacteria.

<Fermentation-accelerating effect of single culture solution of Bulgarian bacteria (effect of shortening fermentation time)>
In (4) (FIG. 4) containing a single culture of Bulgaria, the amount of L-lactic acid produced by Thermophilus reached about 60 mM 3.5 hours after the start of fermentation, and (5) (FIG. 5). ), The amount of L-lactic acid reached about 55 mM. In contrast, in the control (1) (FIG. 1), the amount of L-lactic acid reached about 45 mM.
That is, the amount of L-lactic acid increased in (4) formulated with a Bulgarian monoculture, compared to control (1), and in (5), L-lactic acid increased compared to control (1). The amount increased slightly.

Fermentation time was shortened sufficiently in (4) in which a single culture solution of Bulgaria was mixed. This is because the amount of L-lactic acid is increased by the action of the casein degradation product and peptide derived from the culture solution, and as a result of the increase in the amount of D-lactic acid derived from the culture solution, the total amount of lactic acid is increased. It was considered that the fermentation time was shortened sufficiently.

Fermentation time was slightly shortened in (5) in which a single culture solution of Bulgaria was mixed. This is because thermophilus bacteria are generally inferior in acid resistance, and as a result of the increase in the amount of D-lactic acid derived from the culture solution to about 10 mM, the metabolic activity of thermophilus bacteria is reduced, and the fermentation time is sufficient. It was thought that it was not shortened. Actually, the amount of L-lactic acid produced by Thermophilus was lower at the time of fermentation in (5) in which a single culture solution of Bulgaria was mixed, compared to the control (1).
In other words, in the case of blending a single culture solution of Bulgaria bacteria (5), the total amount of lactic acid increased as a result of the increase in the amount of D-lactic acid derived from the culture solution, and eventually the fermentation time was slightly reduced. Was thought to have been.

<Inhibition effect on increase in acidity of milk peptide (acidity reduction effect during refrigerated storage)>
In (2) (FIG. 2) in which a milk peptide that is a growth promoting factor of Thermophilus was blended, the increase amount of D-lactic acid (= “D-lactic acid amount (D14)” − “D-lactic acid amount (D1)”) Was about 5 mM, and in (3) (FIG. 3), the increased amount of D-lactic acid was about 8 mM. In contrast, in the control (1) (FIG. 1), the increase in D-lactic acid was about 1 mM.

On the other hand, in (2) containing milk peptide, the increased amount of L-lactic acid (= “L-lactic acid amount (D14)” − “L-lactic acid amount (D1)”) was about 18 mM, and in (3), The increased amount of L-lactic acid was about 23 mM. In contrast, in the control (1), the increase in L-lactic acid was about 8 mM.
That is, in (2) and (3) containing milk peptide, compared to control (1), the amount of D-lactic acid produced by Bulgarian bacteria during storage under refrigeration was also the amount of L-lactic acid produced by Thermophilus bacteria. As a result, the increase in acidity during refrigerated storage was not suppressed, and the sour taste of yogurt was thought to have increased.

At this time, in (2) and (3) containing the milk peptide, it was considered that the metabolic vitality of Thermophilus was enhanced and the amount of L-lactic acid was increased as compared with the control (1). As a result of the increase in the number of Bulgarian bacteria by about 10 times, the milk peptide enhanced the metabolic vitality of Thermophilus bacteria and increased the production of formic acid, a growth promoting factor of Bulgarian bacteria. It was thought that the amount of lactic acid increased.

<Inhibition effect of acidity increase in single culture solution of Bulgaria (acidity reduction effect during refrigerated storage)>
In (4) (FIG. 4) and (5) (FIG. 5) containing a bulgaria single culture solution, the amount of D-lactic acid was also reduced during refrigerated storage compared to the control (1) (FIG. 1). -The amount of lactic acid was not particularly increased, and as a result, the increase in acidity during refrigerated storage was suppressed, and the sourness of yogurt was not particularly strong.

In the case of (4) containing a bulgaria single culture, the number of thermophilus bacteria was increased approximately twice compared to the control (1), and the amount of L-lactic acid produced by thermophilus was moderately increased. It was considered that the acidity did not increase excessively while the fermentation time was shortened due to the increase.
Compared with the control (1), the amount of D-lactic acid derived from the Bulgarian monoculture broth increased in (5) containing the Bulgarian monoculture, and the acidity increased during fermentation and the acidity increased. It was considered that the acidity did not increase excessively while the fermentation time was shortened because the metabolic vitality of thermophilus bacteria with poor resistance was reduced and the production amount of L-lactic acid was reduced.

Summary Milk peptides enhance the metabolic vitality of thermophilus and promote fermentation, but enhance the ability of thermophilus to produce L-lactic acid not only during fermentation but also during refrigerated storage. It was thought that the number of bacteria increased. As a result, yogurt blended with milk peptide has a fast fermentation but tends to increase the acidity during refrigerated storage, and conventional fermentation promoters show that fermentation promotion and suppression of acidity increase during storage are not compatible. It was done.

On the other hand, it was thought that the single culture solution of Bulgaria bacteria increased the total amount of lactic acid during fermentation and shortened the fermentation time by reinforcing the amount of D-lactic acid while increasing the number of thermophilus bacteria moderately. . As a result, it was shown that yogurt blended with a single culture solution of Bulgaria bacteria has a tendency to suppress an increase in acidity during refrigerated storage and maintain an appropriate acidity while promoting fermentation. In addition, plain yogurt blended with a culture solution of Bulgaria has improved the natural sweetness and smoothness of the touch.

The method for producing fermented milk of the present invention not only promotes fermentation, but also suppresses an increase in acidity during storage of the obtained fermented milk, and improves quality such as flavor and physical properties. Therefore, plain yogurt and the like are useful for manufacturing on a commercial scale.

Claims

A method for producing fermented milk by adding a starter to raw milk, the method comprising a step of mixing a mixed starter and a single culture of Lactobacillus lactic acid bacteria.
The method according to claim 1, wherein the mixed starter contains a lactic acid bacterium belonging to the genus Lactobacillus and a lactic acid bacterium belonging to the genus Streptococcus.
The method according to claim 1 or 2, wherein the lactic acid bacterium of the genus Lactobacillus is selected from the group consisting of Lactobacillus bulgaricus, Lactobacillus lactis, Lactobacillus acidophilus and Lactobacillus gasseri.
The method according to claim 2 or 3, wherein the Streptococcus lactic acid bacterium is Streptococcus thermophilus or Streptococcus macedonias.
The method according to any one of claims 2 to 4, wherein the Lactobacillus lactic acid bacterium used in the single culture is the same type of lactic acid bacterium as the Lactobacillus lactic acid bacterium used in the mixed starter.
The method according to any one of claims 1 to 5, wherein the lactic acid bacteria in the single culture solution are removed and / or sterilized.
The method according to any one of claims 1 to 6, wherein the removal treatment and / or sterilization treatment is selected from centrifugation, filtration, and heating.
The method according to claim 7, wherein the heating of the single culture is performed together with the heating of the raw milk.
The method according to any one of claims 1 to 8, wherein the single culture broth uses only components contained in raw milk as culture components.
The method according to any one of claims 1 to 9, wherein the single culture solution comprises raw milk, pasteurized milk, skim milk, whole milk powder, skim milk powder, whole fat concentrated milk and / or skim concentrated milk as a culture component. .
The method according to any one of claims 1 to 10, wherein the single culture solution is added at a concentration of 2 to 15% by weight.
Fermented milk produced by the method according to any one of claims 1 to 11.