JP7612081B2 - Method for producing granular soy milk powder, and granular soy milk powder - Google Patents

Description

The present invention relates to a method for producing granular soy milk powder, and to granular soy milk powder.

Soy milk is rich in protein and is widely accepted by consumers as a nutritious beverage.

On the other hand, in order to improve the storage stability and distribution of soy milk, soy milk powder made by drying soy milk has been developed (for example, Patent Documents 1 to 3).

Japanese Patent Application Publication No. 6-153841 JP 2007-6835 A JP 2010-268781 A

Here, soy milk powder is known to have the problem that when added to liquid (such as water), it has low dispersibility and solubility and is prone to forming lumps.
In order to solve such problems, attempts have been made to improve the dispersibility of soy milk powder by using excipients, as shown in Patent Documents 1 to 3.

However, the nutritional content (particularly protein content) of soy milk powder containing excipients may be reduced.
For example, when 10% by mass of an excipient is added to raw soy milk in terms of solid content, the protein content of the resulting soy milk powder is about half that of a soy milk powder that does not contain the excipient.
Therefore, soy milk powder containing excipients functions poorly as a protein source.

Therefore, there is a need for technology to obtain soy milk powder with excellent dispersibility and solubility, regardless of whether or not excipients are used.

The present invention was made in consideration of the above-mentioned circumstances, and aims to provide a manufacturing technology for soy milk powder with excellent dispersibility and solubility.

The inventors discovered that the above problems can be solved by preparing concentrated soy milk that meets certain conditions from raw soy milk during the soy milk powder manufacturing process and then drying the concentrated soy milk, and thus completed the present invention. Specifically, the present invention provides the following:

(1) A method for producing granular soymilk powder, comprising the steps of:
The manufacturing method comprises:
A concentration step for obtaining concentrated soy milk from raw soy milk;
A drying step of obtaining soy milk powder from the concentrated soy milk by spray granulation drying,
The concentrated soy milk has a solid content of 18% by mass or more;
The viscosity of the concentrated soy milk is 500 mPa·s or less at 20°C.
Manufacturing method.

(2) Granular soy milk powder having an average particle size of 220 μm or more and 500 μm or less.

(3) The granulated soymilk powder according to (1), wherein the particle size distribution of the granulated soymilk powder satisfies all of the following:
D10 is 50 μm.
- D50 is 250 μm.
- D90 is 500 μm.

(4) The granulated soy milk powder according to (2), wherein the granulated soy milk powder does not contain any excipients.

The present invention provides a technology for producing soy milk powder with excellent dispersibility and solubility.

The following describes in detail an embodiment of the present invention, but the present invention is not limited thereto.

<Method of producing granulated soy milk powder>
The method for producing granulated soymilk powder of the present invention (hereinafter also referred to as "the production method of the present invention") comprises a concentrating step of obtaining concentrated soymilk from raw soymilk, and a drying step of obtaining soymilk powder from the concentrated soymilk by spray granulation drying.
The concentrated soy milk has a solid content of 18% by mass or more, and a viscosity of 500 mPa·s or less at 20°C.

Soy milk powder is usually obtained by spray drying raw soy milk.
In addition, a concentration step may be performed before spray drying by partially evaporating the water content of the raw soy milk by heating. By performing such a concentration step, the volume of the raw soy milk can be reduced and the drying efficiency can be improved.

However, the present inventors have found that the conditions of the concentration process have a significant effect on the dispersibility and solubility of the resulting soymilk powder.
Specifically, it has been found that if soy milk proteins are denatured during the concentration process, the resulting soy milk powder tends to have poor dispersibility and solubility.
It was also found that the solids concentration and viscosity of the concentrated soymilk obtained after the concentration step serve as indicators of whether or not soymilk protein has been denatured.

As a result of further investigations, the inventors have determined that if the solids concentration of concentrated soy milk is 18% by mass or more and the viscosity of concentrated soy milk is 500 mPa·s or less at 20°C, not only can spray granulation drying be carried out well, but the resulting dried powder also has excellent dispersibility and solubility.

The inventors have also discovered that such soy milk powder with excellent dispersibility and solubility becomes a granular soy milk powder with a specified average particle size.

(1) Definitions The definitions of terms commonly used in the present invention are as follows.

In the present invention, "soy milk" includes a liquid obtained by soaking soybeans in water, grinding them, adding water, boiling them down, and then filtering the liquid.
The term "soymilk powder" also encompasses powder in which the water content of soymilk has been reduced.

In the present invention, "dispersibility of soy milk powder" includes whether the soy milk powder easily sinks in a liquid (such as water) or whether it does not easily float to the surface of the liquid when added to the liquid.
The dispersibility of soy milk powder can be evaluated by the method shown in the Examples.

In the present invention, the "solubility of soymilk powder" includes the property that when soymilk powder is added to a liquid (such as water), the particle size distribution in the liquid is similar to the particle size distribution in the raw material soymilk.
The solubility of soy milk powder can be evaluated by the method shown in the Examples.

In the present invention, "solids concentration" means the ratio of solids to liquid (soy milk, etc.) (unit: mass %), and can be measured using a microwave moisture analyzer.

In the present invention, "viscosity" refers to the viscosity coefficient (unit: Pa·s) of a substance, and can be measured using a B-type viscometer. Furthermore, unless otherwise specified, the viscosity in the present invention refers to the value at 20°C.

In the present invention, the term "granular powder" refers to aggregated particles formed by agglomeration of primary particles.
In one form of the invention, the granular soymilk powder is shaped like a bunch of grapes.

In the present invention, the "average particle size" is determined by laser diffraction methods using the Fraunhofer diffraction theory and the Mie scattering theory.
In the present invention, the average particle size is synonymous with the particle size distribution D50 (median diameter).

In the present invention, "the particle size distribution Dn is X μm" means that "n %" of the particle population has a particle diameter of "X μm or less".
For example, "the D10 of the granular soy milk powder is 1 μm" means that 10% of the particles in the entire granular soy milk powder have a particle size of 1 μm or less.
In the present invention, the particle size distribution Dn is determined by laser diffraction methods using the Fraunhofer diffraction theory and the Mie scattering theory.

In the present invention, "moisture content" refers to the amount of moisture (unit: mass %) contained in a substance (soy milk powder, etc.), and can be measured using an infrared moisture meter.

(2) Details of the Production Method of the Present Invention Each step of the production method of the present invention will be described in detail below.

(2-1) Concentration Step The concentration step is a step for obtaining concentrated soymilk from raw soymilk.

(2-1-1) Raw Soymilk The raw soymilk is not particularly limited, and the same soymilk raw material as the raw soymilk used in the conventional production of soymilk powder can be used.
However, in order to satisfy the viscosity requirements of concentrated soy milk described below, the raw material soy milk used must not have been subjected to any process that would cause protein denaturation (such as excessive heating).

From the viewpoint of easily achieving the effects of the present invention, the raw soy milk is preferably soy milk whose solid content consists only of soybean-derived components, and unadjusted soy milk is more preferable.

The solids concentration of raw soy milk is usually 9 to 10% by mass.

The viscosity of raw soy milk is usually 2 to 3 mPa·s at 20°C.

(2-1-2) Conditions for the Concentration Step In the concentration step, conditions are adopted which can reduce the water content in the raw soymilk and prevent denaturation of soymilk proteins.
Whether or not soy milk protein has been denatured can be determined based on the appearance of the soy milk (gelation, etc.) and the viscosity of the soy milk (whether or not it is greater than 500 mPa·s at 20° C., etc.).

The concentration process is preferably carried out under vacuum conditions, as this makes it easier to prevent denaturation of soy milk proteins.

The degree of vacuum in the concentration process is not particularly limited as long as it can suppress the denaturation of soy milk proteins and achieve the desired solids concentration of the concentrated soy milk, but is usually 4 to 20 kPa.

The temperature of the concentration process is adjusted according to the solids concentration of the desired concentrated soy milk and the degree of vacuum, but is usually between 30 and 70°C.

In the concentration step, a falling film evaporator is preferably used from the viewpoint of facilitating the production of the desired concentrated soy milk.
The "falling film evaporator" is a device that can evaporate and concentrate a liquid substance (soy milk) while it flows down the heat transfer inner wall surface of a heat exchanger as a liquid film.

When the concentration process is carried out using a falling film evaporator, it is preferable to set the evaporation temperature of the raw soy milk under reduced pressure to within the range of 40 to 60°C, and the difference between the evaporation temperature and the heating steam side temperature to within the range of 5 to 15°C.

In the concentration process, the solids concentration of the raw soy milk, the solids concentration and viscosity of the concentrated milk, etc. are monitored, and the resulting concentrated soy milk is subjected to the drying process described below while maintaining the desired solids concentration.

(2-1-3) Concentrated Soy Milk The concentrated soy milk obtained after the concentration step has a solid content of 18% by mass or more and a viscosity of 500 mPa·s or less at 20°C.

The lower limit of the solids concentration of concentrated soy milk is 18% by mass or more, preferably 20% by mass or more.

The upper limit of the solids concentration of concentrated soy milk is preferably 25% by mass or less, more preferably 22% by mass or less, in order to suppress an increase in viscosity.

The upper limit of the viscosity of concentrated soy milk at 20°C is 500 mPa·s or less, preferably 250 mPa·s or less, and more preferably 100 mPa·s or less.

The lower limit of the viscosity of concentrated soy milk is not particularly limited, but is usually 20 mPa·s or more at 20°C.

(2-2) Drying Step The drying step is a step for obtaining soymilk powder from the concentrated soymilk by spray granulation drying.
The soymilk powder obtained after the drying step is the granular soymilk powder desired in the present invention.

The conditions for spray granulation drying can be any conditions that are unlikely to cause denaturation of proteins, reduce the moisture content of the concentrated soy milk by spray drying, and allow powder particles to be granulated.

In terms of preventing protein denaturation, it is preferable to set the drying conditions for the hot air used for drying at an inlet temperature of 120°C or higher and 180°C or lower, and at an outlet temperature of 40°C or higher and 90°C or lower.

For the spray granulation drying, it is preferable to use a fluidized bed granulation spray dryer, since this makes it easier to prepare granular soy milk powder.
A "fluid bed granulation spray dryer" is a device that dries a liquid substance (soy milk) sprayed into a high-temperature air current and granulates the dried material using a fluid bed granulation method.

The granular soy milk powder obtained after the drying process can be used as is, or can be stored or processed.

(2-3) Other Steps Furthermore, the production method of the present invention may or may not include any steps that can be carried out in a soymilk production method, in addition to the above steps, as long as the effects of the present invention are not impaired.
Such a step can be carried out at any time in the production method of the present invention depending on the purpose, etc.

Steps that may be included in the manufacturing method of the present invention include a heating step, a stirring step, a cooling step, a step of deactivating the enzymes in the raw soy milk, a step of packaging the soy milk powder, a sterilization step, etc.

(3) Granulated soymilk powder The present invention also includes granulated soymilk powder obtained by the production method of the present invention.

The average particle size of the granular soymilk powder of the present invention is from 220 μm to 500 μm.
In conventional methods for producing soymilk powder, the viscosity of concentrated soymilk before drying has not been sufficiently adjusted, and therefore it has been difficult to obtain soymilk powder having the above average particle size and in a granular form.

In the granular soymilk powder of the present invention, the lower limit of the average particle size is 220 μm or more, preferably 250 μm or more.

In the granular soy milk powder of the present invention, the upper limit of the average particle size is 500 μm or less, preferably 300 μm or less.

The particle size distribution (Dn) of the granular soymilk powder of the present invention is not particularly limited, but from the viewpoint of facilitating the production of a uniform granular soymilk powder, it may satisfy any or all of the following requirements.
D10 is preferably 100 μm, more preferably 80 μm, and even more preferably 50 μm.
D50 is preferably 500 μm, more preferably 300 μm, and even more preferably 250 μm.
D90 is preferably 2000 μm, more preferably 1000 μm, and even more preferably 500 μm.

The granular soymilk powder of the present invention has good dispersibility and solubility.
In a preferred embodiment of the present invention, the granular soymilk powder of the present invention has an average particle size of 0.5 μm to 1.5 μm when dissolved in water. Conventional soymilk powders tend to form lumps when added to water, making it difficult to achieve such a small average particle size in water.
In the above, the temperature of the water in which the granular soymilk powder is dissolved is not particularly limited, but is preferably from 20° C. to 80° C., more preferably from 50° C. to 60° C. After the granular soymilk powder is dissolved in water, the average particle size may be measured as is, or it may be measured after cooling to about 4° C. to 20° C.

The granular soymilk powder of the present invention is not particularly limited as long as it is in a sufficiently dry state.
The moisture content of the granular soymilk powder of the present invention is preferably 5.0% by mass or less, more preferably 4.5% by mass or less.

The granular soymilk powder of the present invention is in the form of aggregated particles formed by agglomeration of primary particles.
The average particle size of the aggregated particles is, as described above, 220 μm or more and 500 μm or less.
The average particle size of the primary particles constituting the aggregated particles is not particularly limited, but is preferably 30 to 60 μm.

The granular soy milk powder of the present invention may or may not contain any ingredient that can be incorporated into conventional soy milk powders.
Such ingredients include excipients, stabilizers, emulsifiers, thickeners, etc. The types and amounts of these ingredients are appropriately adjusted depending on the effects to be obtained.
The above-mentioned components may also be blended as ingredients together with the raw soymilk when producing the granular soymilk powder.

Conventionally, in order to improve the dispersibility and solubility of soy milk powder, excipients have been blended as ingredients of soy milk powder, as shown in Patent Documents 1 to 3. Examples of excipients include sugars (monosaccharides, oligosaccharides, polysaccharides, and chemically treated products thereof, etc.), proteins derived from sources other than soybeans (collagen, etc.), etc.
On the other hand, the granular soymilk powder of the present invention has excellent dispersibility and solubility, regardless of the presence or absence of an excipient.
Thus, in a preferred embodiment of the present invention, the granulated soy milk powder does not contain an excipient, although the present invention does not exclude an embodiment in which the granulated soy milk powder contains an excipient.

When an excipient is contained in the granulated soy milk powder of the present invention, the content is preferably an amount that does not function as an excipient and an amount that does not impair the function of the granulated soy milk powder as a protein source.
The amount of excipient acceptable from the above viewpoints may be preferably 5% by mass or less, more preferably 1% by mass or less, based on the raw soymilk. In such a case, the granular soymilk powder obtained from the raw soymilk may contain preferably 33.3% by mass or less, more preferably 9.1% by mass or less of the excipient.

The uses of the granular soy milk powder of the present invention are not particularly limited, and it can be used for a variety of purposes similar to those of conventional soy milk powder.

The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

<Preparation of soy milk powder>
Granular soy milk powder (consisting only of ingredients derived from raw soy milk) was prepared by the following method.
As a "reference example," commercially available soy milk powder was also prepared.

(1) Concentration Step Commercially available soy milk (solid content concentration = approximately 9% by mass) was prepared as raw soy milk.
The raw soy milk was concentrated under vacuum conditions using a falling film evaporator.
The vacuum conditions were set so that the evaporation temperature of the raw soy milk under reduced pressure was in the range of 40 to 60°C, and the difference between the evaporation temperature and the heating steam side temperature was in the range of 5 to 15°C.

During the concentration process, the solids concentration and viscosity of the raw soy milk were monitored. The concentration process was completed when the solids concentration of the raw soy milk reached 18-22% by mass, and the resulting soy milk was collected as concentrated soy milk and subjected to a drying process. The viscosity of the concentrated soy milk at the time of the drying process (20°C) was 250 mPa·s.

As "Comparative Example 1," soy milk that had not been subjected to the concentration process (raw soy milk itself) was also subjected to the drying process.

(2) Drying Step The concentrated soy milk was spray-granulated and dried using a fluidized bed granulation spray dryer. The concentrated soy milk was dried and granulated to obtain a granular soy milk powder.

In addition, as "Comparative Example 2," soy milk powder (commercially available, not granular) was also obtained by drying using a single-stage spray dryer and a drum dryer.

<Evaluation of granular soy milk powder>
The obtained soy milk powder was subjected to the following various evaluations.

(1) Average particle size and particle size distribution (Dn)
The average particle size of each soy milk powder was measured by laser diffraction methods using the Fraunhofer diffraction theory and the Mie scattering theory. For the measurement, a "Mastersizer 3000" (manufactured by Malvern Panalytical Co., Ltd.) was used.
The average particle size was measured for the following objects at 20° C. When the object to be measured was a powder, a dry method was used, and when the object was an aqueous solution, a wet method was used.
・Each soy milk powder ・7% by weight aqueous solution of each soy milk powder

(2) Moisture Content The moisture content of each soy milk powder was measured using an infrared moisture meter "FD-720" (manufactured by Kett Electric Laboratory, Ltd.).

(3) Dispersibility MilliQ water (300 g) was placed in a 500 ml stainless steel mug and kept at a water temperature of 60°C.
Next, while stirring with a homogenizing mixer (5,000 rpm), each soy milk powder (25 g) was added, and the dispersion time (unit: second) until the entire amount was sunk was measured.
The shorter the dispersion time, the better the dispersibility.

(4) Solubility As in the above section on "Dispersibility," each soy milk powder was placed in warm MilliQ water and stirred to obtain an aqueous solution of each soy milk powder.
The particle size distribution in each of the obtained aqueous solutions was identified and compared with the particle size distribution in the raw soy milk, and evaluated according to the following criteria. Whether the particle size distributions were similar to each other was judged based on the position and size of the peaks, etc.
A: The particle size distribution is similar to that in the raw soymilk. B: The particle size distribution is different from that in the raw soymilk.

<Results>
The results are shown in the table.

The granular soymilk powder obtained by the manufacturing method of the present invention ("Example") had remarkably excellent dispersibility and solubility.
Furthermore, the granular soymilk powder obtained by the production method of the present invention had an average particle size stably in the range of 220 μm or more and 300 μm or less.

Particle size distribution analysis confirmed that the primary particles of the granular soy milk powder had an average particle size of approximately 50 μm.

On the other hand, when the concentration process was not performed ("Comparative Example 1"), granular soy milk powder could not be obtained stably. In addition, the obtained powder had extremely low dispersibility, and formed large lumps in the aqueous solution, decreasing its solubility.

Although no data is shown, for concentrated soy milk, even if the solid concentration was high, spray granulation drying could be carried out well as long as the viscosity (20° C.) was 500 mPa·s or less. Furthermore, by satisfying all the requirements for concentrated soy milk in the present invention, denaturation of soy milk proteins (which affects gelation, etc.) was suppressed, and the obtained granular soy milk powder had excellent both dispersibility and solubility.
Conversely, if the viscosity (20°C) exceeds 500 mPa·s, regardless of the solids concentration of the concentrated soy milk, the proteins in the soy milk are likely to be denatured, making it difficult to carry out spray granulation drying and only resulting powders have poor dispersibility and solubility.
From this, it was found that suppression of protein denaturation during the concentration step is extremely important from the viewpoint of obtaining granular soymilk powder with excellent dispersibility and solubility. Furthermore, the significance of the solids concentration and viscosity of concentrated soymilk as indicators of the suppression of denaturation was clarified.

Claims (2)

Granular soymilk powder (excluding soymilk powder containing milk) having an average particle size of 220 μm or more and 500 μm or less and containing no excipients. The granular soymilk powder according to claim 1, wherein the particle size distribution satisfies all of the following:
D10 is 50 μm.
- D50 is 250 μm.
- D90 is 500 μm.