WO2019189551A1

WO2019189551A1 - Sterilized fermented milk production method

Info

Publication number: WO2019189551A1
Application number: PCT/JP2019/013525
Authority: WO
Inventors: 佑介野澤; 誠二長岡; 淳宮内; 朋史吉田
Original assignee: 株式会社明治
Priority date: 2018-03-30
Filing date: 2019-03-28
Publication date: 2019-10-03
Also published as: JP2019176774A; CN111918554A; JP7316026B2

Abstract

The present invention addresses the problem of obtaining sterilized fermented milk in which an increase in the size of particles or agglomerates generated during heat sterilization of fermented milk is prevented. Provided is a sterilized fermented milk production method comprising the steps of: fermenting raw material milk and thereby providing fermented milk; and heat sterilizing the obtained fermented milk, the step involving controlling the temperature of the fermented milk and the temperature difference (∆t) between the fermented milk and a heating medium to prevent an increase in the size of agglomerates or particles in the fermented milk.

Description

Method for producing pasteurized fermented milk

The present invention relates to a method for producing pasteurized fermented milk that has been heat-sterilized after fermentation.

Ingredients related to fermented milk (sterilized fermented milk) sterilized by heating after fermentation in the revised Ordinance of Milk (Ministerial Ordinance on Component Standards for Milk and Dairy Products), which was promulgated and enforced on December 23, 2014 Standards were stipulated. Specifically, as for fermented milk, the product standard has been established that the number of lactic acid bacteria or yeast (per ml) is 10 million or more. However, this is not limited to those heated at 75 ° C. or higher for 15 minutes or heat-sterilized by a method having a sterilizing effect equivalent to or higher than this. Thereby, the development of pasteurized fermented milk with a long shelf life and less change in flavor during storage is expected in the future compared to conventional fermented milk.

On the other hand, it is known that casein contained in milk has a property of aggregating and precipitating in an acidic region or the like. In order to solve such a problem, in an acidic milk beverage or the like, an attempt has been made to stabilize by adding a component for suppressing aggregation and precipitation. For example, Patent Document 1 describes a fermented milk beverage or a lactic acid bacteria beverage in which milk protein does not cause agglomeration and separation in view of the fact that if agglomeration and separation occur in an acidic beverage, the appearance of the beverage is significantly impaired and the commercial value decreases. As a production method, a method is proposed in which sodium carboxymethylcellulose is added in advance to a protein raw material in producing raw material fermented milk. Patent Document 2 states that, in the production of acidic milk beverages, when a conventional fermented milk is prepared by adding a conventional stabilizer before fermentation, a supernatant or precipitate is produced due to agglomeration and separation, giving a paste-like feeling, and being rough after eating. On the other hand, in view of the problem that the process and equipment are complicated in the method of separately preparing the raw fermented milk and the stabilizer solution, water-soluble hemicellulose is used as a stabilizer in the presence. We propose a method of fermenting lactic acid bacteria with Patent Document 3 proposes to contain a large amount of low-molecular-weight pectin in acidic milk beverages, etc., with the objective of simultaneously improving the stability of acidic proteins and improving the texture by reducing viscosity. To do. Patent Document 4 aims to provide an acidic milk beverage having a low viscosity and easy to drink and a method for producing the same in an acidic milk beverage containing a milk protein containing a high concentration of casein, and preventing separation and precipitation. The present invention proposes an acidic milk drink characterized by containing soybean polysaccharide, HM pectin, and insoluble cellulose at specific concentrations.

Patent Document 5 focuses on heat sterilization after fermentation in order to prevent pH reduction in preserved fermented milk. While pH 6.0 or lower, protein aggregation is likely to occur due to heating, while conventional sour milk stabilizers have pH 5 In view of the fact that the effect is exhibited only in the following, a method for producing fermented milk, which employs a cross-linked modified starch, ferments a milky solution containing the starch to pH 5.3 to 6, and heat-sterilizes the obtained fermented product. suggest. Patent Document 6 describes a fermentation method with a high protein concentration of pH 3.3 to 5.2 as a method for producing fermented milk containing a high concentration of milk protein that can achieve both a good flavor and a smooth tissue even after heat treatment after fermentation. It is proposed to contain a cross-linked modified starch and a sour milk stabilizer when the milk is heat-treated at 75 ° C. or higher.

Japanese Unexamined Patent Publication No. 63-157931 JP 7-059512 A Japanese Patent Laid-Open No. 2001-61409 International Publication WO2016 / 068251 Publication JP 2017-063727 JP-A-2017-169477

An object of the present invention is to obtain sterilized fermented milk that suppresses an increase in aggregates or particle size that occurs when fermented milk is heat-sterilized. As described above, when milk is heated under acidic conditions, milk protein aggregation occurs, leading to a significant deterioration in flavor. In particular, when the concentration of protein contained in milk is high, aggregation increases, so that it is necessary to contain a large amount of a stabilizer to prevent aggregation, which further causes a decrease in flavor.

The inventors of the present invention have studied various conditions for suppressing the generation of aggregates and the increase in particle diameter in the heat sterilization process when producing sterilized fermented milk. As a result, it is effective to control the temperature in the heat sterilization process, and in particular, by controlling the temperature difference between the fermented milk and the heat medium to be low, the fermented milk can be stabilized and a good sterilized fermented milk with little roughness can be obtained. The present invention has been completed.

The present invention provides the following.
[1] A method for producing pasteurized fermented milk,
A step of fermenting raw material milk to obtain fermented milk; and a step of heat sterilizing the obtained fermented milk, controlling the temperature of the fermented milk and the temperature difference (Δt) between the fermented milk and the heat medium, and fermenting The manufacturing method including the process of suppressing the increase in the diameter of the aggregate or particle | grains in milk.
[2] A method for producing pasteurized fermented milk,
In the heat sterilization process, the manufacturing method including the process of controlling the temperature difference ((DELTA) t) of fermented milk and a heat medium to 7.0 degrees C or less.
[3] The production method according to 2, wherein Δt is controlled to 7.0 ° C. or lower at least when the temperature of the fermented milk is 60 ° C. or higher.
[4] The production method according to any one of 1 to 3, wherein the sterilization condition in the heat sterilization step is a heating condition having a sterilization effect at 75 ° C. or higher for 15 minutes or equivalent or higher.
[5] The production method according to any one of 1 to 4, wherein the fermentation step is performed until the fermented milk has a pH of 5.2 or lower.
[6] The production method according to any one of 1 to 5, comprising a homogenization step before or after the heat sterilization step.
[7] The production method according to any one of 1 to 6, for producing a sterilized fermented milk containing a sour milk stabilizer at 0.30% by mass or less.
[8] A method for stabilizing fermented milk, characterized in that, in the heat sterilization step, a temperature difference (Δt) between the heat-sterilized fermented milk and the heat medium is controlled.

It is possible to provide pasteurized fermented milk with coarse particles or less roughness.
It can manufacture, without mix | blending an acid milk stabilizer excessively by carrying out heat control.
Even in the case of using a raw material having a high protein composition, sterilized fermented milk having good taste with little coarse particles or roughness can be produced without excessively adding a sour milk stabilizer, even if it is sterilized.
Bactericidal and fermented fermented milk containing a large amount of milk components, particularly milk protein, can be produced.
When fermented milk of the present invention is used as fermented milk for business use or as a raw material for processed foods, it does not agglomerate even in a concentrated composition containing a large amount of milk protein, and is liquid or pasty. Convenience such as raw material input can be improved.
It is possible to produce a concentrated liquid or pasty pasteurized fermented milk that cannot be achieved with conventional techniques.

Temperature rise in Examples 1 and 2 Temperature rise in Comparative Examples 1 and 2 Change in median diameter Change in median diameter

This invention provides the manufacturing method of pasteurized fermented milk including the following processes.
The process of fermenting raw milk to obtain fermented milk (fermentation process); and the process of heat sterilizing the obtained fermented milk, and controlling the heat sterilization temperature and the temperature difference (Δt) between the fermented milk and the heat medium Step to perform (heat sterilization step).

<Fermentation process>
[Raw milk]
Raw milk used in the present invention is raw milk, cream, concentrated skim milk, milk protein concentrate, milk, special milk, raw goat milk, pasteurized goat milk, raw noodle milk, ingredient-adjusted milk, low-fat milk, non-fat cow , And any one selected from the group consisting of processed milk.

The concentration of the milk fat in the raw milk is, for example, 8.0% by mass or less, preferably 0.01 to 8.0% by mass, more preferably 0.01 to 7.0% by mass with respect to the whole raw milk. Preferably, 0.01 to 6.0% by mass is more preferable. This is because when the concentration of milk fat in the whole raw milk is within the above range, the flavor is suitable for the obtained sterilized fermented milk.

The concentration of the non-fat milk solid content (SNF) of the raw milk is, for example, 20% by mass or less, preferably 1 to 20% by mass, more preferably 3 to 19% by mass with respect to the whole raw milk. 18% by mass is more preferable. This is because the flavor of the sterilized fermented milk obtained is improved when the concentration of the non-fat milk solids (SNF) within the above range is within the above range. In addition, non-fat milk solid content (SNF) means the component except milk fat among milk components.

The protein concentration of the raw milk is, for example, 12% by mass or less with respect to the whole raw milk, preferably 1 to 11% by mass, more preferably 1.5 to 10% by mass, and further 2 to 9% by mass. preferable. This is because the flavor of the sterilized fermented milk obtained is improved when the milk protein concentration relative to the whole raw milk is within the above range. If the milk protein concentration in the raw milk becomes high, aggregation is likely to occur under acidic conditions or under heating. However, since the production method of the present invention stabilizes appropriately, the raw milk has a high protein concentration. Even if it exists, favorable sterilized fermented milk can be obtained.

Raw material milk may have undergone a homogenization process using a homomixer or a homogenizer. By homogenization, fat globules are atomized, and separation and floating of milk fat contained in raw milk and cream are suppressed. When not mixing raw milk or cream, the homogenization step may be omitted.

Raw material milk may have undergone a sterilization process using an indirect heating device, a direct heating device, an electric heating device, or the like. As a method and equipment for sterilizing raw milk, a method and equipment usually used in the food field may be used. At this time, as a method of sterilizing raw milk, for example, low temperature holding sterilization method (LTLT, 60 to 70 ° C., 20 to 40 minutes, etc.), high temperature holding sterilization method (HTLT, 80 to 90 ° C., 5 to 20 minutes, etc.) Examples include high-temperature and short-time sterilization methods (HTST, 100 to 110 ° C., 1 to 3 minutes, etc.), ultra-high temperature instantaneous sterilization methods (UHT, 120 to 150 ° C., 1 to 10 seconds, etc.) and the like. Before sterilizing the raw milk, the pH of the raw milk may be adjusted as necessary. And after sterilizing raw material milk, after cooling raw material milk to the fermentation temperature vicinity, it is good to add the starter for fermentation.

[Lactic acid bacteria, etc.]
The fermentation process is started by inoculating the raw milk with a microbial starter. Examples of microorganisms include lactic acid bacteria, bifidobacteria, and yeast. In the present invention, known lactic acid bacteria, bifidobacteria, yeasts and the like can be appropriately used as long as the effects of the present invention are obtained. Specifically, in the case of lactic acid bacteria, Bulgarian bacteria, thermophilus bacteria, lactis bacteria, cremiris bacteria, casei bacteria, bifidobacteria that have been used in the production of fermented milk are exemplified, and the results of general use in the production of yogurt A combination (mixture) of Bulgarian bacteria and Thermophilus bacteria is preferred. Hereinafter, fermentation of raw material milk will be specifically described by taking lactic acid bacteria as an example, but in the present invention, microorganisms that can be used for fermentation of raw material milk are not limited to lactic acid bacteria.

[Fermentation conditions]
Conditions for fermenting raw milk are not particularly limited as long as the effects of the present invention are obtained, but it is preferable to appropriately adjust the fermentation temperature and / or fermentation time. At this time, in the present invention, the fermentation temperature depends on the type of lactic acid bacteria actually used, the optimum temperature for the activity of the lactic acid bacteria, etc., but for example, 30-50 ° C. is exemplified, and 35-48 ° C. is preferable, 38 More preferred is ˜45 ° C. Specifically, for example, a combination (mixture) of Bulgarian bacteria and Thermophilus bacteria is exemplified by 30 to 45 ° C, preferably 32 to 44 ° C, more preferably 34 to 44 ° C, still more preferably 36 to 43 ° C, and more preferably 38 to 43 ° C. is particularly preferred. When the fermentation temperature is within the above range, fermented milk having a good flavor can be obtained with an appropriate fermentation time.

The fermentation time depends on the type of lactic acid bacterium actually used, the amount of lactic acid bacterium added, the fermentation temperature, and the like. Specifically, for example, when using a combination (mixture) of Bulgarian bacterium and Thermophilus bacterium, 1 to Examples are 20 hours, 1.5 to 15 hours are preferred, 2 to 12 hours are more preferred, and 2.5 to 10 hours are even more preferred. When the fermentation time is within the above range, sterilized fermented milk with good production suitability and good flavor can be obtained.

The fermentation process can be performed until the pH reaches an appropriate value. The pH at the end of the fermentation is exemplified by 3.0 to 5.2, preferably 3.2 to 4.9, more preferably 3.4 to 4.8, still more preferably 3.6 to 4.5, 3.8 to 4.3 are particularly preferable. This is because fermented milk having a good flavor can be obtained when the pH of the raw milk at the end of fermentation is in the above range. When the pH is 3.8 to 5.2 near the isoelectric point, aggregation is likely to occur in the fermented milk. However, since the production method of the present invention appropriately stabilizes, sufficient fermentation is possible. Even if it is performed, good sterilized fermented milk can be obtained. The pH at the end of fermentation of the raw milk is measured, for example, with a pH meter. In the present invention, when a pH value is indicated, it is a value at 10 ° C. unless otherwise specified.

<Heat sterilization process>
In this invention, fermented milk is heat-sterilized and sterilized fermented milk is manufactured.
[Heat sterilization method, etc.]
Steam or hot water can be used as a heat source (heat medium) in heat sterilization. The method may be an indirect heating method in which heating is performed through a heat exchanger heat transfer wall without bringing the heat medium sterilization target into contact with the heat medium, or a direct heating method in which the heat medium water vapor is brought into contact with the heating target. However, the indirect heating method is preferable from the viewpoint that Δt described later can be easily controlled. In the indirect heating system, a plate heat exchanger, a double tube heat exchanger, a multiple tube heat exchanger, and a multi-tube heat exchanger can be used.

[Sterilization conditions]
The sterilization conditions are not particularly limited as long as the deterioration of the flavor of the fermented milk can be appropriately suppressed. However, the heat sterilization conditions after fermentation of the fermented milk, which are defined in the revised Ministerial Ordinance such as milk, can be applied. Specifically, it is preferable that the heating conditions have a bactericidal effect at 75 ° C. or higher for 15 minutes or equivalent or higher. Heating conditions having a sterilizing effect equivalent to or higher than this may be in the range of 5 minutes at 80 ° C. to 3 seconds at 100 ° C. This range includes heating at 85 ° C. for 120 seconds. It is preferable to cool immediately after heat sterilization.

Other sterilization conditions include, for example, about 50 to 100 ° C. for about 5 seconds to 30 minutes, about 60 to 100 ° C. for about 5 seconds to 20 minutes, about 70 to 100 ° C. for about 5 seconds to 10 minutes, and about 80 to 100 ° C. It can be from 5 seconds to 10 minutes.

In the present invention, in the heat sterilization step after fermentation, when the temperature of the fermented milk is 55 ° C, preferably 57 ° C or higher, more preferably 60 ° C or higher, the temperature of the fermented milk, and The temperature difference (Δt) between the fermented milk and the heat medium is controlled. By controlling Δt in such a temperature zone, an increase in the diameter of aggregates or particles in the sterilized fermented milk can be suppressed. You may control (DELTA) t in the temperature range below 55 degreeC, 57 degreeC, or 60 degreeC. In the present invention, the temperature of the fermented milk, and the fermented milk and the heat medium in at least a part of the time period of the heat sterilization process after fermentation, preferably in the time period of 1/2 or more, more preferably through the sterilization process. And the temperature difference (Δt) between the two may be controlled. Also by such control, the increase in the diameter of the aggregate or particle | grains in sterilized fermented milk can be suppressed.

Specific examples of Δt include 7 ° C. or less, preferably 6 ° C. or less, more preferably 4 ° C. or less, and even more preferably 2 ° C. or less. Although the lower limit of (DELTA) t is not specifically limited, From a viewpoint of making fermented milk reach | attain the target sterilization temperature rapidly, it can be set to 1 degreeC or more, and is good also as 1.4 degreeC or more.

In the sterilization process in the food field, Δt is usually about 10 ° C. However, according to the study by the present inventors, when heat treatment was performed so that Δt was 7.0 ° C. or less during sterilization of fermented milk, heat treatment was performed so that Δt was 7.1 or more. It was found that the increase of aggregates and particle system in fermented milk can be remarkably suppressed as compared with. Further, as the heat sterilization process proceeds, the particle size of the fermented milk tends to increase. However, when Δt is 7.1 ° C. or higher, Δt is 7.degree. C. when the temperature of the fermented milk is 75 ° C. or higher. It was found that an increase in the particle size that cannot be seen when it is 0 or less occurs. In particular, it was confirmed that the particle size at the time of 85 ° C. greatly increased. It has also been confirmed that as the temperature increases, the frequency of large particle size that gives roughness increases, for example, the frequency of particles of 30 to 40 μm or more that gives roughness in liquid fermented milk of 1000 mPa · s or less is also confirmed. It was.

By controlling Δt, sterilized fermented milk can be stabilized even if it is fermented milk with poor fluidity because Δt is kept within a certain value, because the viscosity is higher than that of conventional acidic beverages. This is thought to be because uniform sterilization can be performed with a small amount and excessive agglomeration hardly occurs.

In the present invention, Δt may be controlled when the temperature of the fermented milk becomes relatively high in the heat sterilization step. This is because it is considered that the higher the temperature of the fermented milk, the more easily aggregates are formed and the particle diameter is likely to increase. Specifically, it is exemplified that Δt is controlled to 7.0 ° C. or lower when the temperature of fermented milk is 60 ° C. or higher, and Δt is 7.0 when the temperature of fermented milk is 70 ° C. or higher. It is preferable to control the temperature to ℃ or lower, Δt is preferably controlled to 6.0 ° C or lower when the temperature of the fermented milk is 70 ° C or higher, and Δt is set to 6 when the temperature of the fermented milk is 80 ° C or higher. It is preferable to control to 0.0 ° C. or lower, Δt is preferably controlled to 4.0 ° C. or lower when the temperature of fermented milk is 80 ° C. or higher, and Δt when the temperature of fermented milk is 85 ° C. or higher. Is preferably controlled to 4.0 ° C. or lower, and Δt is preferably controlled to 2.0 ° C. or lower when the temperature of the fermented milk is 85 ° C. or higher.

In the heat sterilization process, it is not necessary to control Δt at the initial stage from the viewpoint of suppressing the generation of aggregates, but Δt tends to increase when the temperature of the fermented milk at the initial stage is relatively low. You may fully control (DELTA) t at the initial stage of a heat sterilization process.

<Other processes>
The manufacturing method of the sterilized fermented milk of the present invention may include other steps before or after any of those steps, in addition to the fermentation step and the heat sterilization step. Other steps include a step of liquefying or homogenizing fermented milk, a step of adding a sour milk stabilizer, a step of filling fermented milk into a container, and the like.

[Liquefaction (crushing) or homogenization]
Fermented milk contains solid curd, but the conditions for liquefying (crushing) or homogenizing fermented milk are not particularly limited, but the viscosity after liquefaction (viscosity of fermented fermented milk) becomes a predetermined viscosity. It is preferable that the particle size after liquefaction is appropriately adjusted so as to be a predetermined particle size.

As a method or equipment for liquefying or homogenizing fermented milk containing the card, a method or equipment usually used in the food field may be used. Examples include homogenizers, homomixers, homodispers, super mixers, mesh filters, in-line mixers, tanks with agitation / temperature adjustment functions, tanks with agitation / temperature adjustment / decompression / homogenization functions, etc. Any one of these can be used alone, or two or more can be used in combination.

The conditions for liquefying or homogenizing the fermented milk can be appropriately designed by those skilled in the art according to the flavor, texture, etc. intended for the sterilized fermented milk to be produced. For example, a 60 mesh filter can be used, and when using a homogenizer, the pressure is exemplified to be 0 to 20 MPa, preferably 0.2 to 15 MPa, more preferably 0.4 to 10 MPa, and 0 More preferably, it is 6 to 8 MPa. The homogenization process using a homogenizer may be performed in two or more stages.

[Addition of sour milk stabilizer]
A sour milk stabilizer can be added to the sterilized fermented milk of the present invention. By adding a sour milk stabilizer, an increase in aggregate or particle size can be further suppressed. When the sour milk stabilizer is added, the type and amount of the sour milk stabilizer and the addition method are not particularly limited as long as the effects of the present invention can be obtained.

The type of sour milk stabilizer is not particularly limited as long as the effects of the present invention can be obtained. ι-carrageenan, deacylated gellan gum, and alginate are exemplified, and any one of them can be used alone, or two or more can be used in combination. Pectin means polygalacturonic acid having an average molecular weight of 50,000 to 150,000 Da. There are two types of galacturonic acid as a constituent sugar, a free type and a methyl ester type, and the proportion of galacturonic acid existing as a methyl ester in the total galacturonic acid is called the degree of esterification (DE value). Depending on this DE value, the properties of pectin differ. Those having a DE value of 50% or more are called high methoxy pectin (HM pectin), and those having a DE value of less than 50% are called low methoxy pectin (LM pectin).

In the production method of the present invention, an increase in the diameter of aggregates and particles in the fermented milk can be suppressed by controlling Δt in the heat sterilization step. Therefore, the fermented milk does not contain a sour milk stabilizer or contains a small amount. It can be. From the viewpoint of further suppressing the increase in aggregates or particle size, it is preferable to include an acid milk stabilizer. When an acid milk stabilizer is included, the amount thereof is specifically the whole of the sterilized fermented milk. On the other hand, 0.050 to 0.50 mass% is exemplified, 0.060 to 0.45 mass% is preferable, 0.060 to 0.40 mass% is more preferable, and 0.070 to 0.35 mass% is preferable. Is more preferable, and 0.070 to 0.30% by mass is particularly preferable. From the viewpoint of further suppressing an increase in aggregates or particle size, the amount of the sour milk stabilizer in the sterilized fermented milk is exemplified by 0.10 to 0.70% by mass, and 0.15 to 0.65% by mass. Is preferable, 0.20 to 0.60% by mass is more preferable, 0.25 to 0.55% by mass is further preferable, and 0.30 to 0.50% by mass is particularly preferable.

The method for adding the sour milk stabilizer is not particularly limited as long as the effect of the present invention can be obtained, but examples thereof include a raw milk sterilization process, a fermentation process, and a fermented milk heat sterilization process. It is sufficient that the sour milk stabilizer is sufficiently dispersed and dissolved. For example, after the sour milk stabilizer is dispersed in water or the like and heated to dissolve, this solution is added to the raw milk or the like. Method, method of heating raw milk to a temperature at which the sour milk stabilizer can be dissolved, and dispersing and dissolving the sour milk stabilizer in this heated raw milk, etc., separate the raw milk and sour milk stabilizer solution Examples thereof include a method of mixing these after sterilization.

<Characteristics of pasteurized fermented milk>
[viscosity]
The viscosity immediately after heat sterilization of the sterilized fermented milk obtained by the present invention is, for example, 200 to 800 mPa · s (measurement temperature: 10 ° C.). If the viscosity of the sterilized fermented milk exceeds 850 mPa · s (measurement temperature: 10 ° C.), the liquid state tends to be weakened and the paste-like character tends to be increased.

When the liquefaction or homogenization step is performed, the viscosity of the sterilized fermented milk is 800 mPa · s or less, preferably 750 mPa · s or less, more preferably 700 mPa · s or less, and further preferably 650 mPa · s or less. This is because fermented milk having a good texture can be obtained by adjusting the viscosity after liquefaction to the above range. In fermented milk, the lower the viscosity, the easier it is to feel roughness due to aggregates and particles with increased diameter, but in the production method of the present invention, the increase in the diameter of aggregates and particles in sterilized fermented milk is suppressed. Therefore, the viscosity can be lowered. In addition, in this invention, when showing the viscosity of fermented milk, it is the value of the viscosity in 10 degreeC except the case where it describes especially.

Viscosity can be measured with a B-type viscometer (for example, VISCO METER-TV-10, Toki Sangyo Co., Ltd.). Specifically, 100 mL of a sample (specimen) is filled into a milk cake (capacity: 110 mL) at 10 ° C., and then the spindle M2 (Toki Sangyo Co., Ltd.) is used as the rotor, and the rotor is rotated (60 rpm, 30 Seconds). When the viscosity is measured by a method other than the above measured with a B-type viscometer, the viscosity range of the present invention (upper limit value) is adjusted with the difference in the measured value of the viscosity measured with the B-type viscometer. , Lower limit value, etc.) can be set.

[Agglomerate]
In the sterilized fermented milk obtained by the present invention, aggregates are suppressed. The presence or degree of aggregates in the fermented milk can be evaluated by confirming the presence or absence or degree of roughness by a sensory test.

[Particle size]
The median diameter of the fermented milk immediately after heat sterilization of the sterilized fermented milk obtained by the present invention is, for example, 20 μm or less. The median diameter of the sterilized fermented milk of the present invention is preferably 1 to 20 μm, more preferably 2 to 18 μm, further preferably 4 to 18 μm, further preferably 6 to 16 μm, and particularly preferably 8 to 16 μm.

In the context of the present invention, when referring to the particle size of fermented milk, unless otherwise specified, the particle size at the point of 50% in the cumulative particle number distribution curve measured with a laser diffraction / scattering particle size distribution measuring device, The particle number standard cumulative 50% diameter (d50). More specifically, the particle size distribution of the sterilized fermented milk dispersion was measured with a laser diffraction particle size distribution analyzer (for example, SALD-2000, Shimadzu Corporation). Yes, the particle diameter of 50% in this integrated value is the particle diameter when the number of particles is added from a small particle diameter and reaches 50% of the total value of the number of particles. In the present invention, the 50% diameter (d50) based on the number of particles is called the median diameter.

The sterilized fermented milk obtained by the present invention can be expected to be stored at 10 ° C. for 14 days immediately after production and no water separation or precipitation is observed. In the present invention, “no water separation is recognized” means that water separation is not substantially observed, and water separation is not recognized at all, or even if it is recognized, the amount is extremely small. It can be confirmed visually that no water separation is observed.
Moreover, in the present invention, “precipitation is not recognized” means that precipitation is not substantially recognized, and precipitation is not recognized at all, or even if it is recognized, it is a very small amount. It can be confirmed visually that no precipitation is observed.

Hereinafter, the present invention will be described by way of examples, but the present invention is not limited to these examples. Further, in these examples, the protein concentration was set to be high in the formulation of the milk raw material. This reason is for clarifying the effect by this invention. In particular, with regard to milk protein, protein aggregation is more likely to occur as the pH approaches 4.6, which is the isoelectric point of casein. However, it is not limited to the compounding of an Example for the above-mentioned reason.

[Test 1. Transition evaluation of particle size during heat sterilization]
<Preparation 1 of fermented milk>
A raw material mix was prepared by mixing cream, raw milk, concentrated skim milk, milk protein concentrate, and water so that the milk fat content was 5.2 wt%, the non-fat solid content was 17.2 wt%, and the protein was 8.0 wt%. The raw material mix was heated to 75 ° C and then homogenized with a homogenizer at a primary pressure of 10 MPa and a secondary pressure of 5 MPa (both flow rates were 135 L / h). The raw mix was sterilized at any temperature and time depending on the purpose and then cooled to 43 ° C. After cooling, lactic acid bacteria starter (Bulgaria bacteria and thermophilus bacteria isolated from Meiji Bulgaria yogurt LB81) was added at 3.0% by weight, and fermentation was performed at 43 ° C for 4 hours to 10 hours until the pH of the fermented milk reached 4.1. . Thereafter, 3.3% HM pectin (manufactured by CP Kelco) was added to adjust the final concentration to 0.5%. Furthermore, homogenization was performed with a homogenizer at a primary pressure of 10 MPa and a secondary pressure of 5 MPa (both flow rates were 135 L / h).

<Evaluation method 1>
[Measurement method of median diameter]
For fermented milk that was heat-treated under the conditions of each example, the particle size distribution of the fermented milk was measured using a laser diffraction particle size distribution analyzer SALD-2200 (manufactured by Shimadzu Corporation). Specifically, fermented milk after heat treatment is diluted with ion-exchanged water adjusted to the measurement target pH, and the maximum value of the diffraction / scattering light intensity distribution is 35 to 75% (absolute value: 700 to 1500) ). Then, this light intensity distribution was analyzed using software WingSALD II for particle size distribution measuring apparatus.

<Examples 1 and 2>
The fermented milk obtained in “Preparation of fermented milk 1” was heated to 60 ° C. After that, heat treatment is performed so that the temperature difference between the fermented milk and hot water (hereinafter referred to as Δt) is within 7.0 ° C. through a temperature zone of 60 ° C. or higher (FIG. 1), 60, 65, 70, 75 The median diameter and particle size distribution at 80 and 85 ° C were evaluated.

<Comparative Examples 1-2>
The fermented milk obtained in “Preparation of fermented milk 1” was heated to 60 ° C. Then, heat treatment was performed so that the Δt of the fermented milk and warm water was 7.1 ° C or higher through the temperature range of 60 ° C or higher (Fig. 2), and the median diameter at 60, 65, 70, 75, 80, and 85 ° C. In addition, the particle size distribution was evaluated.

As a result, as shown in FIG. 3, the median diameter of the fermented milk tends to increase as the heat treatment temperature rises. However, when Δt after heating at 60 ° C. is 7.5 ° C. or more, the median diameter at 85 ° C. Was significantly increased (Comparative Examples 1 and 2). On the other hand, it was confirmed that the median diameter was suppressed when Δt after the temperature increase of 60 ° C. was 6.7 ° C. or less (Examples 1 and 2). In Comparative Examples 1 and 2, as the temperature increases, the particle size distribution increases in frequency although the particle size is large, but in Examples 1 and 2, it is also confirmed that by suppressing Δt during the heat treatment, it is suppressed. It was done.

From the above results, it was confirmed that by reducing Δt during heat sterilization of fermented milk, it is possible to suppress an increase in median diameter that occurs during heating and causes roughness.

[Test 2. Evaluation when using a continuous heat exchanger]
<Preparation 2 of fermented milk>
A raw material mix was prepared by mixing cream, raw milk, concentrated skim milk, milk protein concentrate, and water so that the milk fat content was 5.2 wt%, the non-fat solid content was 17.2 wt%, and the protein was 8.0 wt%. The raw material mix was heated to 75 ° C and then homogenized with a homogenizer at a primary pressure of 10 MPa and a secondary pressure of 5 MPa (both flow rates were 135 L / h). The raw mix was sterilized at any temperature and time depending on the purpose and then cooled to 43 ° C. After cooling, lactic acid bacteria starter (Bulgaria bacteria and thermophilus bacteria isolated from Meiji Bulgaria yogurt LB81) was added at 3.0% by weight, and fermentation was performed at 43 ° C for 4 hours to 10 hours until the pH of the fermented milk reached 4.1. . Thereafter, 3.3% HM pectin solution was added to adjust the final concentration to 0.5%. Furthermore, homogenize the fermented milk with pectin added at a primary pressure of 10MPa and a secondary pressure of 5MPa (both flow rates are 135L / h), and using a continuous heat exchanger, Δt was adjusted to an arbitrary value, subjected to sterilization at 85 ° C. for 24 seconds or 120 seconds, and then cooled to 10 ° C. or lower. Furthermore, the homogenization process was performed depending on the Example.

<Evaluation method 2>
(Viscosity measurement)
The viscosity of the fermented milk produced under the conditions of each example was measured using a B-type viscometer TVB-10 (Toki Sangyo). The sample was measured using a No. 4 (M23) rotor at 60 ° C. for 30 seconds at 10 ° C.

[Measurement method of median diameter]
For fermented milk that was heat-treated under the conditions of each example, the particle size distribution of the fermented milk was measured using a laser diffraction particle size distribution analyzer SALD-2200 (manufactured by Shimadzu Corporation). Specifically, fermented milk after heat treatment is diluted with ion-exchanged water whose pH is adjusted according to the measurement target, and the maximum value of the diffraction / scattering light intensity distribution is 35 to 75% (absolute value: 700 to 1500). Then, this light intensity distribution was analyzed using software WingSALD II for particle size distribution measuring apparatus.

〔sensory evaluation〕
Five panelists sampled the fermented milk that had been heat-treated under the conditions of each example, and evaluated the presence or absence of roughness.

<Example 3>
In the description of “Preparation 2 of fermented milk” above, Δt (at 85 ° C.) at the time of heat sterilization is adjusted to 1.5 ° C., this fermented milk is subjected to sterilization at 85 ° C. for 24 seconds, then cooled, and then sterilized. Various evaluations were made on fermented milk. In this heat treatment, Δt ≦ 7.0 ° C. in a temperature range of at least 60 ° C. or higher.

<Example 4>
The sterilized fermented milk obtained in the same manner as in Example 3 was homogenized with a homogenizer at a primary pressure of 10 MPa and a secondary pressure of 5 MPa (both flow rates were 135 L / h), and various evaluations were made.

<Example 5>
In the description of “Preparation 2 of fermented milk” above, Δt (at 85 ° C.) at the time of heat sterilization is adjusted to 3.1 ° C., this fermented milk is subjected to sterilization at 85 ° C. for 120 seconds, and then cooled and then sterilized fermentation The milk was homogenized with a homogenizer at a primary pressure of 10 MPa and a secondary pressure of 5 MPa (both flow rates were 135 L / h) and evaluated in various ways.

<Comparative Example 3>
In the description of “Preparation 2 of fermented milk” above, Δt (at 85 ° C.) at the time of heat sterilization is adjusted to 15.2 ° C., this fermented milk is subjected to sterilization at 85 ° C. for 24 seconds, then cooled, and then sterilized. Various evaluations were made on fermented milk.

<Comparative example 4>
The pasteurized fermented milk obtained in the same manner as in Comparative Example 3 was homogenized with a homogenizer at a primary pressure of 10 MPa and a secondary pressure of 5 MPa (both flow rates were 135 L / h), and various evaluations were made.

As a result, as shown in the table below, in Examples 3 to 5, it was confirmed that smooth fermented milk without roughness could be produced without keeping homogenization after heat sterilization by keeping Δt small. On the other hand, in Comparative Examples 3 to 4, it was confirmed that the roughening of the fermented milk could not be eliminated even if a homogenization treatment was performed after heat sterilization.

From the above results, it was confirmed that even in sterilization using a continuous heat exchanger, by reducing Δt during heat sterilization, it is possible to suppress aggregates and median diameters that occur during heating and cause roughness. .

[Test 3. Evaluation when adjusting pectin concentration]
<Preparation of fermented milk 3>
A raw material mix was prepared by mixing cream, skim milk powder and water so that the milk fat content was 1.7% by weight, the non-fat solid content was 16.7% by weight, and the protein was 6.0% by weight. The raw material mix was heated to 75 ° C and then homogenized with a homogenizer at a primary pressure of 10 MPa and a secondary pressure of 5 MPa (both flow rates were 135 L / h). The raw mix was sterilized at any temperature and time depending on the purpose and then cooled to 43 ° C. After cooling, lactic acid bacteria starter (Bulgaria bacteria and thermophilus bacteria isolated from Meiji Bulgaria yogurt LB81) was added at 3.0 wt%, and fermentation was performed at 43 ° C for 4 to 8 hours until the pH of the fermented milk reached 4.3. . Thereafter, in some examples, 60-mesh filter treatment was performed to obtain a smoothed fermented milk. The final concentration of HM pectin was adjusted to 0.3% or 0.5% in the fermented milk after fermentation or the smoothed fermented milk. Further, after adding pectin, Δt at the time of heat sterilization was adjusted to an arbitrary value by a batch method, subjected to sterilization at 85 ° C. for 120 seconds, cooled to 10 ° C. or less, and homogenized.

<Evaluation method 3>
(Viscosity measurement)
The viscosity of the fermented milk heat-treated under the conditions of each example was measured using a B-type viscometer TVB-10 (Toki Sangyo). The sample was measured using a No. 3 (M22) or No. 4 (M23) rotor at 30 ° C. for 30 seconds at 10 ° C.

[Measurement method of median diameter]
For fermented milk that had been heat-treated under the conditions of each Example, the median diameter of the fermented milk was measured using a laser diffraction particle size distribution analyzer SALD-2200 (manufactured by Shimadzu Corporation). Specifically, fermented milk after heat treatment is diluted with ion-exchanged water whose pH is adjusted according to the measurement target, and the maximum value of the diffraction / scattering light intensity distribution is 35 to 75% (absolute value: 700 to 1500). Then, using the software WingSALD II for the particle size distribution measuring device, the distribution of the light intensity was analyzed, and the median diameter and the standard deviation were obtained.

〔sensory evaluation〕
Five panelists sampled the fermented milk that had been heat-treated under the conditions of each Example, and evaluated the flavor and texture.

<Example 6>
In the description of “Preparation 3 of fermented milk” described above, 60-mesh filter treatment was performed to obtain a smoothed fermented milk. Thereafter, the mixture was mixed so that the final concentration of HM pectin was 0.3%, Δt at the time of heat sterilization was adjusted to 1.0 to 4.0 ° C., this fermented milk was subjected to sterilization at 85 ° C. for 120 seconds, and then cooled. The obtained sterilized fermented milk was homogenized with a homogenizer at a primary pressure of 10 MPa and a secondary pressure of 5 MPa (both flow rates were 135 L / h) and variously evaluated. The median diameter at 80 and 85 ° C. during the heat treatment was also evaluated.

<Example 7>
The fermented milk obtained in the above description of “Preparation of Fermented Milk 3” (without 60 mesh filter treatment) was adjusted so that the final concentration of HM pectin was 0.5%. Thereafter, Δt at the time of heat sterilization was adjusted to 2.0 to 4.0 ° C., the fermented milk was subjected to sterilization at 85 ° C. for 120 seconds, and then cooled. The obtained sterilized fermented milk was homogenized with a homogenizer at a primary pressure of 10 MPa and a secondary pressure of 5 MPa (both flow rates were 135 L / h) and variously evaluated. The median diameter at 80 and 85 ° C. during the heat treatment was also evaluated.

<Comparative Example 5>
In the description of “Preparation 3 of fermented milk” described above, 60-mesh filter treatment was performed to obtain a smoothed fermented milk. Thereafter, the final concentration of HM pectin was adjusted to 0.3%, Δt at the time of heat sterilization was adjusted to 8.0 to 12.0 ° C., this fermented milk was subjected to sterilization at 85 ° C. for 120 seconds, and then cooled. The obtained sterilized fermented milk was homogenized with a homogenizer at a primary pressure of 10 MPa and a secondary pressure of 5 MPa (both flow rates were 135 L / h) and variously evaluated. The median diameter at 80 and 85 ° C. during the heat treatment was also evaluated.

<Comparative Example 6>
The fermented milk obtained in the above description of “Preparation of Fermented Milk 3” (without 60 mesh filter treatment) was adjusted so that the final concentration of HM pectin was 0.5%. Thereafter, Δt at the time of heat sterilization was adjusted to 8.0 to 10.0 ° C., the main fermented milk was subjected to sterilization at 85 ° C. for 120 seconds, and then cooled. The obtained sterilized fermented milk was homogenized with a homogenizer at a primary pressure of 10 MPa and a secondary pressure of 5 MPa (both flow rates were 135 L / h) and variously evaluated. The median diameter at 80 and 85 ° C. during the heat treatment was also evaluated.

As a result, as shown in Table 2 and FIG. 4, it was confirmed that the median diameter was suppressed by reducing Δt in Examples 6 and 7 compared to Comparative Examples 5 and 6.

In addition, as shown in Table 3, when the pectin concentration is reduced to 0.3%, the median diameter is suppressed by reducing Δt even when the pectin concentration is reduced to 0.3%. It was confirmed that it was not allowed.

From the above results, it was confirmed that by reducing Δt at the time of heat sterilization, even when the pectin concentration was lowered, it was possible to suppress the aggregates and median diameters that occurred during heating and caused roughness.

Claims

A method for producing sterilized fermented milk,
A step of fermenting raw material milk to obtain fermented milk; and a step of heat sterilizing the obtained fermented milk, controlling the temperature of the fermented milk and the temperature difference (Δt) between the fermented milk and the heat medium, and fermenting The manufacturing method including the process of suppressing the increase in the diameter of the aggregate or particle | grains in milk.
A method for producing sterilized fermented milk,
In the heat sterilization process, the manufacturing method including the process of controlling the temperature difference ((DELTA) t) of fermented milk and a heat medium to 7.0 degrees C or less.
The production method according to claim 2, wherein controlling Δt to 7.0 ° C or lower is performed at least when the temperature of the fermented milk is 60 ° C or higher.
The production method according to any one of claims 1 to 3, wherein the sterilization conditions in the heat sterilization step are heating conditions having a sterilization effect at 75 ° C or higher for 15 minutes or equivalent or higher.
The production method according to any one of claims 1 to 4, wherein the fermentation step is performed until the fermented milk has a pH of 5.2 or less.
The production method according to any one of claims 1 to 5, comprising a homogenization step before or after the heat sterilization step.
The production method according to any one of claims 1 to 6, for producing sterilized fermented milk containing an acid milk stabilizer at 0.30% by mass or less.
A method for stabilizing fermented milk, characterized in that, in the heat sterilization step, the temperature difference (Δt) between the heat-sterilized fermented milk and the heat medium is controlled.