Soymilk manufacturing method and soymilk

Abstract

To provide a method for producing soymilk capable of producing soymilk having a higher soybean solids concentration than conventional soybeans with the same blending amount of soybeans as conventional soybeans and reducing unpleasant odor derived from soybeans, and to provide high-concentration soymilk with reduced unpleasant odor. [Solution] In producing soymilk, the following steps are carried out in succession: step S3, in which unsterilized soymilk obtained by grinding soybeans or defatted soybeans and then separating the solid and liquid is preheated by indirect heating or electric heating until the liquid temperature reaches 90°C or higher; step S4, in which the preheated unsterilized soymilk is sterilized by a direct steam heating method such as steam injection or steam infusion; and step S5, in which the sterilized soymilk is cooled under reduced pressure until the liquid temperature reaches 85°C or lower, with the difference between the liquid temperature during preheating and the liquid temperature during reduced pressure cooling being set to 5 to 35°C.

Description

[Technical field]

[0001] The present invention relates to a method for producing soymilk and soymilk produced by this method, and more particularly to a technique for producing highly concentrated soymilk. [Background technology]

[0002] Drinking soy milk currently available on the market is generally produced by crushing soybeans that have absorbed water, separating the liquid component obtained by solid-liquid separation, sterilizing the liquid component, and further subjecting it to vacuum deodorization and deaeration treatment and homogenization treatment as necessary. In addition, due to the increasing health consciousness in recent years, high-concentration soy milk with a high soybean solid content concentration has been attracting attention.

[0003] On the other hand, soy milk has a particular odor (a grassy smell), and when the soybean solids concentration is high, the grassy smell becomes stronger, which reduces consumer preference, and therefore there is a demand for improving the flavor. One method for reducing the grassy smell of soy milk is to subject a slurry or solution obtained from soybeans or defatted soybeans that has not been subjected to acid precipitation to a direct steam injection high-temperature instantaneous heating and decompression treatment at 100 to 140°C for 30 to 90 seconds and then at 140 to 160°C for 3 to 30 seconds (see Patent Document 1).

[0004] Also proposed is a grinding and heat treatment method in which, immediately after the grinding step, the temperature of the ground soybeans is raised to a temperature range of 65°C to 90°C so that the temperature rise rate of the ground soybeans is 1°C to 70°C per second, and this raised temperature state is maintained for 1 to 180 seconds, and then, the temperature rise rate of the ground soybeans is set to predetermined conditions, the temperature of the ground soybeans is raised to a predetermined temperature, and this raised temperature state is maintained for a predetermined period of time.These steps are connected in series to form a sealed continuous line (see Patent Document 2). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2007-82510 A [Patent Document 2] JP 2007-222158 A Summary of the Invention [Problem to be solved by the invention]

[0006] However, when high-concentration soy milk is produced by the conventional soy milk production method described above, there are problems with productivity and quality. Specifically, in the conventional production method, if the blending ratio of soybeans during extraction is increased to increase the soybean solids concentration of the soy milk, the efficiency of protein extraction from the soybeans to the soy milk decreases, resulting in a decrease in productivity. In addition, as the soybean solids concentration increases, the grassy smell of the resulting soy milk also becomes stronger, but the methods described in the above-mentioned Patent Documents 1 and 2 are unable to sufficiently reduce this smell.

[0007] Therefore, an object of the present invention is to provide a method for producing soymilk that can produce soymilk having a higher soybean solids concentration than conventional soybeans with the same amount of soybeans blended as conventional soybeans and that can also reduce unpleasant odors derived from soybeans, and to provide high-concentration soymilk with reduced unpleasant odors. [Means for solving the problem]

[0008] The method for producing soymilk according to the present invention comprises the steps of preheating unsterilized soymilk obtained by grinding soybeans or defatted soybeans and then separating the solid and liquid, using an indirect heating method or an electric heating method until the liquid temperature reaches 90°C or higher, sterilizing the preheated unsterilized soymilk using a direct steam heating method, and cooling the sterilized soymilk under reduced pressure until the liquid temperature reaches 85°C or lower, wherein each of the above steps is carried out continuously, and the difference between the liquid temperature during the preheating and the liquid temperature during the reduced pressure cooling is set to 5 to 35°C. The sterilization treatment may be carried out, for example, under a temperature condition of 130 to 160° C. for 1 to 90 seconds. In the method for producing soymilk of the present invention, for example, the liquid temperature during the preheating may be set to 90 to 100°C, and the liquid temperature during the reduced pressure cooling may be set to 65 to 85°C. In the method for producing soymilk of the present invention, for example, when the soybean solids concentration of the unsterilized soymilk before the pre-heating is 6 to 14 mass%, the soybean solids concentration of the sterilized soymilk after the reduced pressure cooling can be 0.3 to 1 mass% higher than that of the unsterilized soymilk before the pre-heating.

[0009] The soymilk of the present invention contains 3% by mass or more of soy protein, and has a hexanal content of 15 ppb or less and a 1-hexanol content of 5 ppb or less per 1% by mass of the soy protein. Effect of the Invention

[0010] According to the present invention, the soybean solids concentration can be increased without increasing the amount of soybeans blended, and further, the unpleasant odor derived from soybeans can be reduced, thereby obtaining high-concentration soymilk with reduced unpleasant odor. [Brief description of the drawings]

[0011] [Figure 1] 1 is a flowchart showing a method for producing soymilk according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. Note that the present invention is not limited to the following preferred embodiments.

[0013] The method for producing soymilk according to the embodiment of the present invention continuously performs at least a step of preheating non-sterile soymilk, a step of sterilizing the pre-heated non-sterile soymilk, and a step of cooling the sterilized soymilk under reduced pressure to obtain high-concentration soymilk. Fig. 1 is a flow chart showing the method for producing soymilk according to the embodiment of the present invention. In the method for producing soymilk according to the embodiment of the present invention, for example, as shown in Fig. 1, a grinding step S1, a solid-liquid separation step S2, a preheating step S3, a sterilization step S4, and a cooling step S5 are performed.

[0014] [Friction process S1] In the grinding step S1, for example, soybeans or defatted soybeans that have been soaked in water or hot water to absorb water are ground as is or with the addition of water or hot water to obtain go (soybean slurry). The soybeans used in the soymilk of this embodiment may be either whole soybeans or dehulled soybeans, and the type is not particularly limited, and various types of soybeans such as yellow soybeans, black soybeans, red soybeans, green soybeans, white soybeans, large-grain soybeans, medium-grain soybeans, and small-grain soybeans may be used, and components contained in soybeans such as lipoxygenase and saponin, or genetically modified soybeans in which a part of soybean storage protein has been deleted or increased may also be used.

[0015] [Solid-liquid separation process S2] In the solid-liquid separation step S2, the soybean pulp obtained in the grinding step S1 is separated from the soybean pulp by centrifugation, filtration, or the like to obtain unsterilized soymilk. To obtain high-concentration soymilk with a soybean solids concentration of 10% by mass or more, it is preferable that the unsterilized soymilk after solid-liquid separation (unsterilized soymilk before preheating) has a soybean solids concentration of 6 to 14% by mass.

[0016] [Preheating process S3] In the preheating step S3, the non-sterilized soymilk obtained in the solid-liquid separation step S2 is preheated by indirect heating or electric heating until the liquid temperature reaches 90°C or higher. The soymilk temperature here can be measured, for example, at the outlet of a heater, but it may also be measured inside the heater. The heating method in the preheating step S3 is indirect heating, which indirectly heats the soymilk from the outside of a pipe using steam or hot water, or an electric heating method, which directly heats the soymilk using Joule heating or microwave heating, so the concentration of the soymilk does not change in the preheating step S3.

[0017] In this way, by preheating the non-sterilized soymilk at a higher temperature than conventionally using an indirect heating method or an electric heating method that does not involve the introduction of a heat transfer medium such as steam, prior to the sterilization process S4, it is possible to reduce the amount of steam used in the sterilization process S4 and also to reduce the amount of steam that gets mixed into the soymilk throughout the entire production process.

[0018] However, if the preheating temperature (liquid temperature of soymilk during preheating) is less than 90°C, the effect of reducing the amount of steam used in the sterilization treatment step S4 may not be fully achieved, and therefore, in the method for producing soymilk of this embodiment, the preheating temperature is set to 90°C or higher. From the viewpoint of suppressing the generation of deterioration odor due to excessive thermal history during preheating, the preheating temperature is preferably set to 90 to 100°C.

[0019] [Sterilization process S4] In the sterilization process S4, the preheated non-sterilized soymilk is sterilized by a steam injection method in which steam is injected, or a steam infusion method in which non-sterilized soymilk is heated by passing it through a space filled with steam. The heating method used in this sterilization process S4 is a direct steam heating method in which high-temperature steam is mixed with non-sterilized soymilk to heat it directly, and since moisture is added to the soymilk by the amount of the mixed steam, the concentration of the soymilk becomes diluted, but in the soymilk manufacturing method of this embodiment, the liquid temperature of the non-sterilized soymilk is 90°C or higher due to the preheating process S3, so sterilization can be performed with less steam mixed in than before.

[0020] The sterilization conditions are not particularly limited, but the smaller the difference between the preheating temperature (soymilk liquid temperature during preheating) and the sterilization temperature (soymilk liquid temperature during sterilization), the smaller the amount of direct steam mixing. From the viewpoint of sterilization efficiency and reducing the amount of steam mixing, the sterilization is preferably performed at a liquid temperature (sterilization temperature) of 130 to 160°C for 1 to 90 seconds, and more preferably under conditions where the liquid temperature after direct steam mixing is 140 to 160°C.

[0021] [Decompression cooling process S5] In the reduced pressure cooling step S5, the sterilized soy milk obtained by the sterilization process is exposed to a vacuum pressure and instantly cooled to the saturated steam temperature at the vacuum pressure, and the steam mixed in during the sterilization process S4 is evaporated and removed. Specifically, the heated sterilized soy milk is cooled under reduced pressure until the liquid temperature is 85°C or lower, and the steam mixed in during the sterilization process is removed.

[0022] Conventionally, reduced pressure cooling after sterilization is performed under conditions where the same amount of steam as that mixed in is evaporated, resulting in the same solids concentration in non-sterilized soymilk and sterilized soymilk. In contrast, in the method for producing soymilk of this embodiment, the reduced pressure cooling step S5 removes more water than the amount of condensed water mixed in during sterilization, thereby increasing the soybean solids concentration of the sterilized soymilk compared to non-sterilized soymilk, and concentrating the soymilk. In addition, because hexanol, 1-hexanol, and other components that cause unpleasant odors (hereinafter referred to as "unpleasant odor components") are volatile, these unpleasant odor components can also be removed by the above-mentioned reduced pressure cooling.

[0023] However, if the difference between the preheating temperature (liquid temperature of soymilk during preheating) and the reduced pressure cooling temperature (liquid temperature of soymilk during reduced pressure cooling) is less than 5°C, the soymilk may not be sufficiently concentrated. Therefore, in the method for producing soymilk of this embodiment, the reduced pressure cooling temperature (liquid temperature of soymilk during reduced pressure cooling) is set to a temperature that is 5 to 35°C lower than the preheating temperature. The liquid temperature of soymilk referred to here can be measured, for example, at the outlet of a cooling device, but may also be measured inside the cooling device.

[0024] In the method for producing soymilk of this embodiment, the amount of steam mixed into the soymilk is reduced by preheating using an indirect heating method or an electric heating method, so the lower the reduced pressure cooling temperature is relative to the preheating temperature, the greater the amount of steam evaporated by reduced pressure cooling compared to the amount of steam mixed into the soymilk during the sterilization treatment, and the higher the solids concentration of the sterilized soymilk is than that of non-sterilized soymilk. Therefore, by setting the difference between the preheating temperature and the reduced pressure cooling temperature at 5 to 35°C, the concentration rate of the soymilk can be increased, and the soybean solids concentration of the sterilized soymilk can be increased by about 0.3 to 1% compared to non-sterilized soymilk.

[0025] From the viewpoint of soymilk concentration efficiency and unpleasant odor component removal efficiency, when the preheating temperature is 90-100°C, the reduced pressure cooling temperature is preferably 65-85°C. In this way, for example, when the soybean solids concentration of non-sterilized soymilk before preheating is 6-14% by mass, highly concentrated sterilized soymilk with a soybean solids concentration of 6.3-15% by mass can be obtained. The method for measuring the soybean solids concentration of soymilk is not particularly limited, and can be measured by known methods such as heat drying method and infrared spectroscopy, but can also be measured by, for example, the method described in Yoshimasa Omura and 1 other person, "Effect of Hot Water Treatment on Soymilk Flavor," Journal of Food Engineering, Vol. 37, No. 4, April 1990, pp. 278-280.

[0026] The above-mentioned preheating step S3, sterilization step S4, and reduced pressure cooling step S5 can be carried out, for example, using a direct heating sterilization device that is commonly used by those skilled in the art.

[0027] [Highly concentrated soy milk] Hexanal and 1-hexanol are known to be the components that give soy milk its grassy smell, but because these components are produced by the oxidation of fatty acids contained in soybeans, the more soybeans are used to produce high-concentration soymilk, the greater the amount of the components that cause the grassy smell in the resulting soymilk. On the other hand, because both hexanal and 1-hexanol are volatile components, it is known that the content of these components is reduced by the reduced pressure treatment carried out during the production process.

[0028] That is, the soymilk of this embodiment is produced by the above-mentioned method, contains 3% by mass or more of soy protein, has a hexanal content of 15 ppb or less and a 1-hexanol content of 5 ppb or less per 1% by mass of soy protein. The soymilk of this embodiment has a soy protein content of preferably 4% by mass or more, more preferably 4.65% by mass or more.

[0029] The method for measuring the amount of soy protein contained in soy milk is not particularly limited, and known methods such as the Kjeldahl method, the combustion method (modified Dumas method), and Fourier transform infrared spectroscopy can be used, but an analysis method using a Fourier transform infrared spectrometer is generally used. The method for measuring odor components in soy milk is also not particularly limited, and known methods such as high performance liquid chromatography (HPLC), gas chromatography (GC), headspace gas chromatography (HSS-GC), and solid phase microextraction gas chromatography (SPME-GC) can be used, but measurement by the headspace sampler (HSS) method (see Japanese Patent No. 6122172) is preferred.

[0030] Even though the soymilk of this embodiment is a high-concentration soymilk containing 3% by mass or more of soy protein, the contents of hexal and 1-hexanol, which cause unpleasant odors, are equal to or less than those of normal concentration soymilk. Thus, according to the method for producing soymilk of this embodiment, high-concentration soymilk with reduced unpleasant odors can be obtained.

[0031] As described above in detail, in the method for producing soymilk of this embodiment, preheating is performed at a higher temperature than in the past by indirect heating or electric heating before sterilization, and the reduced pressure cooling temperature is set to a temperature 5 to 35°C lower than the preheating temperature, so that the soybean solids concentration can be increased without increasing the amount of soybeans blended, and unpleasant odors derived from soybeans can also be reduced. This allows efficient concentration of soymilk and removal of unpleasant odor components, resulting in high-concentration soymilk with reduced unpleasant odors.

[0032] In conventional manufacturing methods such as those described in Patent Documents 1 and 2, sterilization by direct heating and cooling under reduced pressure are repeated two or more times to increase the removal rate of unpleasant odor components. However, in the soymilk manufacturing method of the present embodiment, it is possible to keep the dilution rate of soymilk lower than in conventional manufacturing methods, so that unpleasant odor components can be sufficiently removed with a single sterilization treatment using the direct steam heating method. EXAMPLES

[0033] The effects of the present invention will be specifically described below with reference to Examples and Comparative Examples. In these Examples, soymilk of Examples and Comparative Examples was prepared by the method described below, and the amount of unpleasant odor components contained therein was compared.

[0034] Comparative Example 1 Whole soybeans A were ground, and the unsterilized soy milk (soybean solid content: 9% by mass) obtained by solid-liquid separation was preheated by indirect heating with steam until the liquid temperature at the heater outlet reached 80°C, and then sterilized for at least 1 second at a temperature of 140°C or higher using a steam injection method in which steam is injected. The sterilized soy milk after sterilization was then cooled under reduced pressure until the liquid temperature at the cooler outlet reached 80°C, producing soy milk with a soy protein content of 4.00% by mass.

[0035] Comparative Example 2 Whole soybeans A were ground in an amount increased by 20% by mass compared to Comparative Example 1, and the unsterilized soymilk (soybean solids concentration: 11% by mass) obtained by solid-liquid separation was preheated by indirect heating with steam until the liquid temperature at the heater outlet reached 80°C, and then sterilized at 140°C or higher for 1 second or more using a steam injection method in which steam is injected. The sterilized soymilk after sterilization was then cooled under reduced pressure until the liquid temperature at the cooler outlet reached 80°C, producing soymilk with a soy protein content of 4.65% by mass.

[0036] Example 1 Unsterilized soy milk (soybean solid content: 9% by mass) obtained by grinding the same amount of whole soybeans A as in Comparative Example 1 and then separating the solid and liquid was preheated by indirect heating with steam until the liquid temperature at the heater outlet reached 95°C, and then sterilized at 140°C or higher for 1 second or more by a steam injection method in which steam is injected. The sterilized soy milk after sterilization was then cooled under reduced pressure until the liquid temperature at the cooler outlet reached 76°C, producing soy milk with a soy protein content of 4.65% by mass.

[0037] Comparative Example 3 Soy milk with a soy protein content of 4.00% by mass was produced using the same method and conditions as in Comparative Example 1, except that whole soybeans B different from those used in Comparative Examples 1 and 2 and Example 1 described above were used and the preheating temperature was 81°C and the reduced pressure cooling temperature was 81°C.

[0038] Comparative Example 4 Soy milk with a soy protein content of 4.65% by mass was produced using the same whole soybeans B as in Comparative Example 3, using the same method and conditions as in Comparative Example 2, except that the preheating temperature was 81°C and the reduced pressure cooling temperature was 81°C.

[0039] Comparative Example 5 Soy milk with a soy protein content of 4.65% by mass was produced using the same whole soybeans B as in Comparative Example 3, using the same method and conditions as in Comparative Example 2, except that the preheating temperature was 95°C and the reduced pressure cooling temperature was 95°C.

[0040] Example 2 Soy milk with a soy protein content of 4.65% by mass was produced using the same whole soybeans B as in Comparative Example 3, using the same method and conditions as in Example 1, except that the preheating temperature was 93°C and the reduced pressure cooling temperature was 76°C.

[0041] [Measurement of odor components] Next, for each of the soymilks of Comparative Examples 1 to 5 and Examples 1 and 2 prepared by the above-mentioned method, the hexanal content and 1-hexanol content per 1 mass% of soy protein were determined by the same method as described in the examples of Japanese Patent No. 6122172. Measurements of hexanal and 1-hexanol were performed using a 20 ml vial containing 10 g of soymilk and sealed, using an HSS-GC / MS device. The measurement conditions are shown below.

[0042] (1)HSS conditions Equipment: Agilent Technologies 7697A Oven: Temperature 80℃, stirring for 20 minutes

[0043] (2)GC / MS conditions Equipment: Agilent Technologies Gas Chromatography (GC) 8890 and Mass Spectrometer 5977B Column: Agilent Technologies VF-WAXms (length 60 m × inner diameter 320 μm × film thickness 0.50 μm) Column temperature: 35°C for 5 min, increase to 100°C at 5°C / min, increase to 240°C at 15°C / min, and hold at 240°C for 4 min. Carrier gas: Helium Injection mode: Pulsed split mode Injection port temperature: 200℃ Transfer line: 240℃ Ion source: Temperature 230℃ EI mode SIM parameters: m / z=56, 69, 82

[0044] (3) Calculation of the amount of unpleasant odor components First, the hexanal concentration and 1-hexanol concentration in each soy milk were calculated from the peak area on the chromatogram using a calibration curve with the standard of each component as an external standard. Next, the hexanal content and 1-hexanol content per 1% by mass of soy protein were calculated based on the soy protein content of each soy milk. The results are summarized in Table 1 below.

[0045] [Table 1]

[0046] As shown in Table 1 above, the soymilk of Examples 1 and 2 produced by the method of the present invention had the same soy protein content as the high-concentration soymilk of Comparative Examples 2 and 4 and 5 produced using the same soybean raw material and at the same preheating temperature and reduced pressure cooling temperature, but the unpleasant odor components hexanal and 1-hexanol were reduced by about 40% and about 60%, respectively. Furthermore, the soymilk of Examples 1 and 2 had lower hexanal and 1-hexanol contents per 1% by mass of soy protein than the normal concentration soymilk of Comparative Examples 1 and 3, which used the same soybean raw material.

[0047] From the above results, it was confirmed that according to the present invention, soymilk with a high soybean solids concentration can be produced even with the same amount of soybeans blended as in the past, and that the unpleasant odor derived from soybeans can also be reduced, thereby obtaining high-concentration soymilk with reduced unpleasant odor.

[0048] The present invention can also have the following configuration. [1] A step of preheating non-sterilized soy milk obtained by grinding soybeans or defatted soybeans and then separating the solid and liquid, by indirect heating or electric heating until the liquid temperature reaches 90°C or higher; a step of sterilizing the preheated non-sterile soy milk by a direct steam heating method; a step of cooling the sterilized soy milk under reduced pressure until the liquid temperature is 85°C or less; having The above steps are carried out continuously, and A method for producing soymilk, wherein the difference between the liquid temperature during the preheating and the liquid temperature during the reduced pressure cooling is set to 5 to 35°C. [2] The method for producing soymilk according to [1], wherein the sterilization treatment is carried out at a temperature of 130 to 160° C. for 1 to 90 seconds. [3] The method for producing soymilk according to [1] or [2], wherein the liquid temperature during the preheating is set to 90 to 100°C, and the liquid temperature during the reduced pressure cooling is set to 65 to 85°C. [4] The non-sterilized soy milk before preheating has a soybean solids concentration of 6 to 14% by mass, The method for producing soymilk according to any one of [1] to [3], wherein the sterilized soymilk after the reduced pressure cooling has a soybean solids concentration 0.3 to 1 mass % higher than that of the non-sterilized soymilk before the preheating. [5] Contains 3% or more by mass of soy protein, The soy milk has a hexanal content of 15 ppb or less and a 1-hexanol content of 5 ppb or less per 1 mass % of the soy protein.

Claims

1. A step of preheating non-sterilized soy milk obtained by grinding soybeans or defatted soybeans and then separating the solid and liquid, by indirect heating or electric heating until the liquid temperature reaches 90°C or higher; a step of sterilizing the preheated non-sterile soy milk by a direct steam heating method; a step of cooling the sterilized soy milk after the sterilization treatment under reduced pressure until the liquid temperature is 85° C. or less; having The above steps are carried out consecutively, and The method for producing soymilk, wherein the difference between the liquid temperature during the preheating and the liquid temperature during the reduced pressure cooling is set to 5 to 35°C.

2. 2. The method for producing soymilk according to claim 1, wherein the sterilization treatment is carried out at a liquid temperature in the range of 130 to 160° C. for 1 to 90 seconds.

3. 2. The method for producing soymilk according to claim 1, wherein the liquid temperature during the preheating is set to 90 to 100°C, and the liquid temperature during the reduced pressure cooling is set to 65 to 85°C.

4. The non-sterilized soy milk before preheating has a soybean solids concentration of 6 to 14% by mass, 2. The method for producing soymilk according to claim 1, wherein the sterilized soymilk after the reduced pressure cooling has a soybean solids concentration 0.3 to 1% by mass higher than that of the non-sterilized soymilk before the preheating.

5. Contains 3% or more by mass of soy protein; The soymilk has a hexanal content of 15 ppb or less and a 1-hexanol content of 5 ppb or less per 1 mass % of the soy protein.

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