Method for producing soybean milk and soybean milk

Abstract

To provide a method for producing soybean milk capable of producing soybean milk having a higher concentration of soybean solid content than conventional one with the same blending amount of soybean as conventional one and reducing unpleasant smell derived from soybean, and to provide high-concentration soybean milk having reduced unpleasant smell.SOLUTION: In the production of soybean milk, a S3 in which unsterilized soybean milk obtained by grinding soybeans or defatted soybeans and then subjecting the ground soybeans to solid-liquid separation is preheated to a liquid temperature of 90 °C or higher, a S4 in which the preheated unsterilized soybean milk is sterilized by a vapor direct-heating method such as a steam-injection method or a steam-infusion method, and a S5 in which the sterilized soybean milk is cooled under reduced pressure to a liquid temperature of 85 °C or lower are continuously performed, and the difference between the liquid temperature during preheating and the liquid temperature during cooling under reduced pressure is 5 to 35 °C.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

[0002] Soy milk for drinking that is currently commercially available is generally produced by crushing soybeans that have absorbed water, separating the soybeans into solid and liquid components, sterilizing the resulting liquid component, and further subjecting it to vacuum deodorization and deaeration treatments and homogenization treatments as necessary. In addition, with the recent increase in health consciousness, high-concentration soy milk with a high concentration of soybean solids has been attracting attention.

[0003] On the other hand, soy milk has a distinctive odor (a grassy smell), and a high soybean solids concentration intensifies this grassy smell, reducing consumer preference, so there is a need to improve 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 high-temperature flash heating and reduced pressure treatment by direct steam injection 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 milling and heat treatment method in which, immediately after the milling step, the temperature of the milled soybeans is raised to a temperature range of 65°C to 90°C so that the temperature rise rate of the milled 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 milled soybeans is set to predetermined conditions, the temperature of the milled soybeans is raised to a predetermined temperature, and this raised temperature state is maintained for a predetermined time, and 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] Japanese Patent Application Laid-Open No. 2007-82510 [Patent Document 2] Japanese Patent Application Laid-Open No. 2007-222158 Summary of the Invention [Problem to be solved by the invention]

[0006] However, when high-concentration soy milk is produced using the conventional soy milk production methods described above, there are problems with productivity and quality. Specifically, in conventional production methods, 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 into the soy milk decreases, resulting in a decrease in productivity. Furthermore, as the soybean solids concentration increases, the resulting soy milk also has a stronger grassy smell, 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 soymilk 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 from the 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 the above steps are carried out continuously, and the difference in liquid temperature between the preheating step and the cooling step under reduced pressure is set to 5 to 35°C. The sterilization treatment may be carried out, for example, at a temperature 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 preheating is 6 to 14% by mass, the soybean solids concentration of the sterilized soymilk after the reduced-pressure cooling can be made 0.3 to 1% by mass higher than that of the unsterilized soymilk before the preheating.

[0009] The soy milk 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. [Effects 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 highly concentrated soy milk with reduced unpleasant odor. [Brief explanation of the drawings]

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

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

[0013] The method for producing soymilk according to an embodiment of the present invention comprises successively performing at least a step of preheating unsterilized soymilk, a step of sterilizing the preheated unsterilized soymilk, and a step of cooling the sterilized soymilk under reduced pressure to obtain high-concentration soymilk. Fig. 1 is a flowchart showing the method for producing soymilk according to an embodiment of the present invention. For example, as shown in Fig. 1, the method for producing soymilk according to this embodiment comprises a grinding step S1, a solid-liquid separation step S2, a preheating step S3, a sterilization step S4, and a cooling step S5 under reduced pressure.

[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 water or hot water added to obtain a 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 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. Components contained in soybeans, such as lipoxygenase and saponin, or genetically modified soybeans in which a portion of a 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, okara is separated from the go obtained in the grinding step S1 by centrifugation, filtration, or the like to obtain unsterilized soy milk. To obtain high-concentration soy milk with a soybean solids concentration of 10% by mass or more, the unsterilized soy milk after solid-liquid separation (unsterilized soy milk before preheating) preferably has a soybean solids concentration of 6 to 14% by mass.

[0016] [Preheating step S3] In the preheating step S3, the unsterilized 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 liquid temperature here can be measured, for example, at the outlet of the heater, but it may also be measured inside the heater. The heating method in the preheating step S3 is indirect heating, in which the soymilk is indirectly heated from the outside of the piping using steam or hot water, or electric heating, in which the soymilk is directly heated using Joule heating or microwave heating, and therefore the concentration of the soymilk does not change in the preheating step S3.

[0017] In this way, by preheating the unsterilized soy milk at a higher temperature than conventionally using an indirect heating method or an electric heating method that does not involve the mixing of a heat medium such as steam before the sterilization treatment step S4, it is possible to reduce the amount of steam used in the sterilization treatment step S4 and also reduce the amount of steam mixed into the soy milk throughout the entire production process.

[0018] However, if the preheating temperature (liquid temperature of soy milk 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 sufficiently obtained, and therefore, in the method for producing soy milk 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 step S4, the preheated unsterilized soy milk is sterilized by a steam injection method in which steam is injected, or a steam infusion method in which unsterilized soy milk is heated by passing it through a space filled with steam. The heating method used in this sterilization step S4 is a direct steam heating method in which high-temperature steam is mixed with the unsterilized soy milk to heat it directly, and since moisture is added to the soy milk in an amount equal to the amount of mixed steam, the concentration of the soy milk becomes diluted, but in the soy milk manufacturing method of this embodiment, the liquid temperature of the unsterilized soy milk is 90°C or higher due to the preheating step S3, so sterilization can be performed with less mixed steam than in the past.

[0020] The sterilization conditions are not particularly limited, but the smaller the difference between the preheating temperature (liquid temperature of soy milk during preheating) and the sterilization temperature (liquid temperature of soy milk during sterilization), the less steam is directly mixed in. From the viewpoint of sterilization efficiency and reducing the amount of steam mixed in, the sterilization is preferably carried out 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 treatment is exposed to vacuum pressure and instantly cooled to the saturated steam temperature under vacuum pressure, and the steam mixed in during the sterilization treatment step S4 is evaporated and removed. Specifically, the heated sterilized soy milk is cooled under reduced pressure until the liquid temperature reaches 85°C or less, and the steam mixed in during the sterilization treatment is removed.

[0022] Conventionally, reduced-pressure cooling after sterilization is performed under conditions in which the same amount of steam as that mixed in is evaporated, resulting in the same solids concentration in unsterilized soy milk and sterilized soy milk. In contrast, in the method for producing soy milk 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 soy milk compared to unsterilized soy milk and concentrating the soy milk. Furthermore, 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 soy milk during preheating) and the reduced pressure cooling temperature (liquid temperature of soy milk during reduced pressure cooling) is less than 5°C, the soy milk may not be sufficiently concentrated. Therefore, in the method for producing soy milk of this embodiment, the reduced pressure cooling temperature (liquid temperature of soy milk during reduced pressure cooling) is set to a temperature that is 5 to 35°C lower than the preheating temperature. The liquid temperature of soy milk referred to here can be measured, for example, at the outlet of the cooling device, but it may also be measured inside the cooling device.

[0024] In the method for producing soymilk of this embodiment, preheating is performed by an indirect heating method or an electric heating method, thereby reducing the amount of steam mixed into the soymilk, and therefore 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 sterilization, resulting in a higher solids concentration in sterilized soymilk than in unsterilized soymilk. Therefore, by setting the difference between the preheating temperature and the reduced pressure cooling temperature to 5 to 35°C, the concentration rate of the soymilk can be increased, and the soybean solids concentration in sterilized soymilk can be made about 0.3 to 1% higher than in unsterilized soymilk.

[0025] From the viewpoint of the efficiency of concentrating soy milk and the efficiency of removing unpleasant odor components, when the preheating temperature is 90 to 100°C, the reduced-pressure cooling temperature is preferably 65 to 85°C. This makes it possible to obtain highly concentrated sterilized soy milk with a soy solids concentration of 6.3 to 15% by mass, for example, when the soy solids concentration of unsterilized soy milk before preheating is 6 to 14% by mass. The method for measuring the soy solids concentration of soy milk is not particularly limited, and can be measured by known methods such as heat drying and infrared spectroscopy. However, it can also be measured by the method described in, for example, Yoshimasa Omura et al., "Effect of Hot Water Treatment on Soy Milk Flavor," Journal of Food Technology, 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 using, for example, 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 soy milk, the greater the amount of the components that cause the grassy smell in the resulting soy milk.On the other hand, because both hexanal and 1-hexanol are volatile components, it is known that the content of these components decreases through vacuum treatments and other processes carried out during the production process.

[0028] That is, the soy milk of this embodiment is produced by the above-mentioned method, 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 soy protein. The soy protein content in the soy milk of this embodiment is 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 analytical method using a Fourier transform infrared spectrometer is generally used. Furthermore, 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 soy milk of this embodiment is a high-concentration soy milk 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 soy milk. Thus, the method for producing soy milk of this embodiment can produce high-concentration soy milk with reduced unpleasant odors.

[0031] As described above in detail, in the method for producing soymilk of this embodiment, preheating is performed by indirect heating or electric heating at a temperature higher than conventional methods before sterilization, and the reduced pressure cooling temperature is set to a temperature 5 to 35°C lower than the preheating temperature, so 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 soymilk to be concentrated efficiently and unpleasant-odor components to be removed, 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 treatment 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 soy milk manufacturing method of the present embodiment, it is possible to keep the dilution rate of soy milk lower than in conventional manufacturing methods, and therefore unpleasant odor components can be sufficiently removed with a single sterilization treatment by the direct steam heating method. [Example]

[0033] The effects of the present invention will be specifically described below with reference to Examples and Comparative Examples. In these Examples, soy milks of Examples and Comparative Examples were prepared by the methods described below, and the amounts of unpleasant odor components contained therein were compared.

[0034] Comparative Example 1 Whole soybeans A were ground, and then solid-liquid separation was carried out to obtain unsterilized soy milk (soybean solids concentration: 9% by mass). The unsterilized soy milk 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 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 milled in an amount 20% by mass greater than that of Comparative Example 1, and the resulting unsterilized soy milk (soybean solids concentration: 11% by mass) was then separated into solid and liquid forms. This 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 140°C or higher using a steam injection method in which steam is injected. The sterilized soy milk 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 4.65% 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 using a steam injection method in which steam is injected.The sterilized soy milk 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 whole soybeans B different from those used in the above-mentioned Comparative Examples 1 and 2 and Example 1, using the same method and conditions as in the above-mentioned Comparative Example 1, except that 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 soy milks 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% by mass of soy protein were determined using a method similar to that described in the examples of Japanese Patent No. 6122172. Measurement of hexanal and 1-hexanol was carried out using an HSS-GC / MS system using 10 g of soy milk in a 20 ml vial that was sealed. The measurement conditions are shown below.

[0042] (1)HSS conditions Apparatus: Agilent Technologies 7697A Oven: 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 minutes, increased to 100°C at 5°C / min, increased to 240°C at 15°C / min, and maintained at 240°C for 4 minutes. Carrier gas: Helium Injection mode: Pulsed split mode Injection port temperature: 200°C 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 and 1-hexanol concentrations in each soy milk were calculated from the peak areas on the chromatogram using calibration curves with the standard products of each component as external standards. Next, the hexanal and 1-hexanol contents 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 soy milk of Examples 1 and 2 produced by the method of the present invention had the same soy protein content as the high-concentration soy milk of Comparative Examples 2 and 4 and 5, which were produced using the same soybean raw material and at the same preheating and reduced-pressure cooling temperatures, but the unpleasant odor components hexanal and 1-hexanol were reduced by about 40% and about 60%, respectively. Furthermore, the soy milk of Examples 1 and 2 had lower hexanal and 1-hexanol contents per 1% by mass of soy protein than the normal-concentration soy milk of Comparative Examples 1 and 3, which were produced using the same soybean raw material.

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

[0048] The present invention can also have the following configuration. [1] A step of preheating unsterilized soy milk obtained by grinding soybeans or defatted soybeans and then separating the solid and liquid, by an indirect heating method or an electric heating method until the liquid temperature reaches 90°C or higher; a step of sterilizing the preheated unsterilized soy milk using 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; and The steps are carried out consecutively, and A method for producing soy milk, 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 soy milk 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 unsterilized 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 that is 0.3 to 1% by mass higher than that of the unsterilized 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% by 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 soy milk into solid and liquid forms by indirect heating or electric heating until the liquid temperature reaches 90°C or higher; a step of sterilizing the preheated unsterilized soy milk using 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; and The steps are carried out consecutively, and The method for producing soy milk, 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 unsterilized 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 that is 0.3 to 1% by mass higher than that of the unsterilized soymilk before the preheating.

5. Contains 3% by mass or more 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% by mass of the soy protein.

Images