Method for producing granular soy milk powder, and granular soy milk powder

Abstract

An object of the present invention is to provide a technique for producing soymilk powder having excellent dispersibility and solubility. The present invention provides a method for producing granulated soymilk powder, the method comprising: a concentrating step of obtaining concentrated soymilk satisfying predetermined conditions from raw soymilk; and a drying step of obtaining soymilk powder from the concentrated soymilk by spray granulation drying.

Description

[Technical field]

[0001] The present invention relates to a method for producing granular soymilk powder, and to a granular soymilk powder. [Background technology]

[0002] Soy milk is widely accepted by consumers as a nutritious beverage rich in protein.

[0003] On the other hand, from the viewpoint of improving the storage stability, distribution, etc. of soy milk, soy milk powder obtained by drying soy milk has been developed (for example, Patent Documents 1 to 3). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 6-153841 [Patent Document 2] JP 2007-6835 A [Patent Document 3] JP 2010-268781 A Summary of the Invention [Problem to be solved by the invention]

[0005] Here, soy milk powder is known to have a problem in that when added to liquid (water, etc.), it has low dispersibility and solubility and is prone to forming lumps. To solve such problems, attempts have been made to improve the dispersibility and other properties of soy milk powder by using excipients, as shown in Patent Documents 1 to 3.

[0006] 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 when no excipient is added. Therefore, soy milk powder containing excipients functions poorly as a protein source.

[0007] Therefore, there is a need for a technology for obtaining soymilk powder with excellent dispersibility and solubility, regardless of whether or not an excipient is used.

[0008] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a production technique for soymilk powder having excellent dispersibility and solubility. [Means for solving the problem]

[0009] The present inventors have found that the above problems can be solved by preparing concentrated soy milk that satisfies certain conditions from raw soy milk in the process of producing soy milk powder, and then drying the concentrated soy milk, and have completed the present invention. Specifically, the present invention provides the following.

[0010] (1) A method for producing granulated soy milk 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.

[0011] (2) Granular soy milk powder having an average particle size of 220 μm or more and 500 μm or less.

[0012] (3) The granulated soy milk powder according to (1), wherein the particle size distribution of the granulated soy milk powder satisfies all of the following: D10 is 50μm. -D50 is 250μm. D90 is 500μm.

[0013] (4) The granulated soy milk powder according to (2), wherein the granulated soy milk powder does not contain an excipient. Effect of the Invention

[0014] According to the present invention, a technique for producing soymilk powder having excellent dispersibility and solubility is provided. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] Hereinafter, an embodiment of the present invention will be described in detail, but the present invention is not particularly limited thereto.

[0016] <Manufacturing method of 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 solids concentration of 18% by mass or more, and a viscosity of 500 mPa·s or less at 20°C.

[0017] 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.

[0018] 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.

[0019] As a result of further investigations, the present inventors have determined that when 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 dry powder also has excellent dispersibility and solubility.

[0020] The present inventors have also found that such soymilk powder having excellent dispersibility and solubility becomes granular soymilk powder having a specified average particle size.

[0021] (1) Definition The definitions of terms commonly used in the present invention are as follows.

[0022] 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.

[0023] 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.

[0024] In the present invention, the "solubility of soymilk powder" includes the fact 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.

[0025] In the present invention, the "solid content concentration" means the ratio (unit: mass %) of solid content to liquid (soy milk, etc.), and can be measured using a microwave moisture analyzer.

[0026] 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.

[0027] 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.

[0028] 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).

[0029] 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 a granulated soy milk powder is 1 μm" means that 10% of the particles in the entire granulated 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.

[0030] In the present invention, the "moisture content" refers to the amount of water (unit: mass %) contained in a substance (soy milk powder, etc.), and can be measured using an infrared moisture meter.

[0031] (2) Details of the manufacturing method of the present invention Each step of the production method of the present invention will be described in detail below.

[0032] (2-1) Concentration process The concentration step is a step for obtaining concentrated soy milk from raw soy milk.

[0033] (2-1-1) Raw soy milk The raw soymilk is not particularly limited, and the same raw soymilk as that 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).

[0034] From the viewpoint of easily achieving the effects of the present invention, the raw material soymilk is preferably soymilk whose solid content consists solely of components derived from soybeans, and unadjusted soymilk is more preferable.

[0035] The solid content concentration of the raw material soymilk is usually 9 to 10% by mass.

[0036] The viscosity of raw soy milk is usually 2 to 3 mPa·s at 20°C.

[0037] (2-1-2) Conditions for the concentration process In the concentration step, conditions are adopted that can reduce the water content in the raw soymilk and that do not easily cause denaturation of soymilk proteins. Whether or not soymilk protein has been denatured can be determined based on the appearance of the soymilk (e.g., gelation) and viscosity of the soymilk (e.g., whether it is greater than 500 mPa·s at 20°C).

[0038] The concentration step is preferably carried out under vacuum conditions, since this makes it easier to prevent denaturation of soy milk proteins.

[0039] The degree of vacuum in the concentration step is not particularly limited as long as it can suppress denaturation of soy milk proteins and can achieve the desired solids concentration of concentrated soy milk, but is usually 4 to 20 kPa.

[0040] The temperature in the concentration step is adjusted depending on the solid content concentration of the desired concentrated soy milk and the degree of vacuum, but is usually 30 to 70°C.

[0041] In the concentration step, it is preferable to use a falling film evaporator, from the viewpoint that the desired concentrated soymilk can be easily obtained. The "falling film evaporator" is a device that can evaporate and concentrate a liquid substance (soy milk) as it flows down the heat transfer inner wall surface of a heat exchanger as a liquid film.

[0042] When the concentration step is carried out using a falling film evaporator, it is preferable to set the evaporation temperature of the raw soymilk under reduced pressure to within a range of 40 to 60°C, and the difference between the evaporation temperature and the heating steam side temperature to within a range of 5 to 15°C.

[0043] In the concentration step, the solids concentration of the raw soy milk, the solids concentration and viscosity of the concentrated soy milk, etc. are monitored, and the concentrated soy milk obtained while maintaining the desired solids concentration is subjected to the drying step described below.

[0044] (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.

[0045] The lower limit of the solid content concentration of concentrated soy milk is 18% by mass or more, and preferably 20% by mass or more.

[0046] The upper limit of the solid content concentration of the concentrated soy milk is preferably 25% by mass or less, and more preferably 22% by mass or less, from the viewpoint of suppressing an increase in viscosity.

[0047] 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.

[0048] 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.

[0049] (2-2) Drying process The drying step is a step of obtaining soy milk powder from the concentrated soy milk by spray granulation drying. The soymilk powder obtained after the drying step is the granular soymilk powder desired in the present invention.

[0050] The conditions for spray granulation drying may be any conditions under which denaturation of proteins is unlikely to occur, the moisture content of the concentrated soy milk can be reduced by spray drying, and powder particles can be granulated.

[0051] From the viewpoint of preventing protein denaturation, the drying conditions in the spray granulation drying are preferably set such that the inlet temperature of the hot air used for drying is 120°C or higher and 180°C or lower, and the outlet temperature is approximately 40°C or higher and 90°C or lower.

[0052] 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 it using the fluid bed granulation method.

[0053] The granular soymilk powder obtained after the drying step may be used as is, or may be stored or processed.

[0054] (2-3) Other processes Furthermore, the production method of the present invention may or may not include, in addition to the above steps, any step that can be carried out in a method for producing soymilk, as long as it does not impair the effects of the present invention. Such a step can be carried out at any time in the production method of the present invention depending on the purpose, etc.

[0055] Steps that may be included in the production method of the present invention include a heating step, a stirring step, a cooling step, a step of inactivating the enzymes in the raw soymilk, a step of packaging the soymilk powder, a sterilization step, and the like.

[0056] (3) Granular soy milk powder The present invention also includes granular soymilk powder obtained by the production method of the present invention.

[0057] The average particle size of the granular soymilk powder of the present invention is 220 μm or more and 500 μm or less. 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.

[0058] 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.

[0059] In the granular soymilk powder of the present invention, the upper limit of the average particle size is 500 μm or less, preferably 300 μm or less.

[0060] 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.

[0061] 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.

[0062] 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.

[0063] 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.

[0064] 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.

[0065] Conventionally, 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.) and proteins derived from sources other than soybeans (collagen, 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.

[0066] 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 does not impair the function of the granulated soy milk powder as a protein source. The amount of excipient acceptable from the above viewpoint 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.

[0067] The applications of the granular soy milk powder of the present invention are not particularly limited, and it can be used for various applications similar to those of conventional soy milk powder. EXAMPLES

[0068] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

[0069] <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.

[0070] (1) Concentration process As the raw soy milk, commercially available soy milk (solid content concentration = approximately 9 mass %) was prepared. 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.

[0071] 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.

[0072] In addition, 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.

[0073] (2) Drying process The concentrated soy milk was spray-granulated and dried using a fluidized bed granulation spray dryer, whereby the concentrated soy milk was dried and granulated to obtain a granular soy milk powder.

[0074] Also, as "Comparative Example 2", soymilk powder (commercially available, not granular) was obtained by drying using a single-stage spray dryer and a drum dryer.

[0075] <Evaluation of granulated soy milk powder> The obtained soy milk powder was subjected to the following various evaluations.

[0076] (1) Average particle size and particle size distribution (Dn) The average particle size of each soy milk powder was measured using laser diffraction methods based on the Fraunhofer diffraction theory and the Mie scattering theory, using a "Mastersizer 3000" (Malvern Panalytical). 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. Soy milk powder 7% by weight aqueous solution of each soy milk powder

[0077] (2) Moisture content The moisture content of each soy milk powder was measured using an infrared moisture meter "FD-720" (Kett Electric Laboratory, Ltd.).

[0078] (3) Dispersibility MilliQ water (300g) was placed in a 500ml stainless steel mug and kept at 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: seconds) until the entire amount was sunk was measured. The shorter the dispersion time, the better the dispersibility.

[0079] (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 of the raw soy milk. B: The particle size distribution is different from that of the raw soy milk.

[0080] <Result> The results are shown in the table.

[0081] The granular soymilk powder obtained by the production 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 that was consistently within the range of 220 μm or more and 300 μm or less.

[0082] Furthermore, particle size distribution analysis confirmed that the primary particles of the granular soymilk powder had an average particle size of about 50 μm.

[0083] On the other hand, when the concentration step was not performed ("Comparative Example 1"), granular soymilk powder could not be obtained stably. In addition, the obtained powder had extremely low dispersibility, and formed large lumps in the aqueous solution, resulting in low solubility.

[0084] Although data is not shown, spray granulation drying could be carried out well for concentrated soy milk, even if the solid concentration was high, so long as the viscosity (20°C) was 500 mPa s or less. Furthermore, by satisfying all of the requirements for concentrated soy milk in this 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 in a powder with 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.

[0085]

Table 1

Claims

1. A method for producing granular soy milk powder (excluding soy milk powder containing milk), comprising the steps of: The manufacturing method comprises: A concentrating step of obtaining concentrated soy milk from raw soy milk using a falling film evaporator; A drying step of obtaining granular 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. The method according to claim 1, wherein the drying step produces granular soymilk powder having an average particle size of 220 μm or more and 500 μm or less.

3. The method according to claim 1 , wherein in the drying step, a granular soymilk powder is obtained having a particle size distribution that satisfies all of the following: D10 is 50 μm. - D50 is 250 μm. - D90 is 500 μm.

4. The method according to any one of claims 1 to 3, which does not include a step of adding an excipient.

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