Method for producing soy milk and soy milk

Abstract

Provided are: a method for producing soy milk that is capable of producing soy milk with a higher concentration of soybean solids than conventional methods from a blending amount of soybeans equivalent to conventional methods, and that can also reduce unpleasant odors originating from the soybeans; and a soy milk that has a reduced amount of unpleasant odors originating from soybeans while maintaining the flavor of the soy milk.　In the present invention, a soy milk with a soy protein content of at least 3% by mass and a hexanal content per 1% by mass of soy protein of 15 ppb or less is obtained by performing, in sequence: a step S3 in which an unsterilized soy milk, obtained by milling soybeans or defatted soybeans and then subjecting same to solid / liquid separation, is preliminarily heated to a liquid temperature of 90°C or higher by indirect heating or electrical heating; a step S4 in which the preliminarily heated unsterilized soy milk is subjected to sterilization treatment using direct steam heating such as steam injection, steam infusion, or the like; and a step S5 in which the sterilized soy milk resulting from the sterilization treatment is subjected to reduced-pressure cooling to a liquid temperature of 85°C or below, the difference between the liquid temperature at the time of preliminary heating and the liquid temperature at the time of reduced-pressure cooling being 5–35°C.

Description

Soy milk manufacturing method and soy milk

[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.

[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 the grassy smell, which reduces consumer preference, and therefore 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 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 a predetermined condition, the temperature of the ground 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).

[0005] JP 2007-82510 A JP 2007-222158 A

[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 the 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 to the soy milk decreases, resulting in a decrease in productivity. Furthermore, 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, the present invention aims to provide a method for producing soymilk that can produce soymilk having a higher soybean solids concentration than conventional soybeans with the same soybean blending amount as conventional soybeans and that can also reduce unpleasant odors derived from soybeans, and to provide soymilk in which the unpleasant odors derived from soybeans are reduced while maintaining the flavor of soymilk.

[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 the steps are carried out continuously, and the difference in liquid temperature between the preheating and the cooling under reduced pressure is set to 5 to 35°C. The sterilization 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 according to 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 cooling under reduced pressure 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% 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 pre-heating.

[0009] The soymilk according to the present invention has a hexanal content per 1% by mass of soy protein of 15 ppb or less, and a ratio of the amount of maltol to the amount of hexanal (maltol / hexanal) determined from the peak area in gas chromatography by the headspace method of 100 or more. Another soymilk according to the present invention has a 1-octen-3-ol content per 1% by mass of soy protein of 3.0 ppb or less, and a ratio of the amount of maltol to the amount of 1-octen-3-ol (maltol / 1-octen-3-ol) determined from the peak area in gas chromatography by the headspace method of 105 or more. In the soymilk of the present invention, the maltol content per 1% by mass of soy protein can be 1.0 ppm or more. Another soymilk according to the present invention has a 1-octen-3-ol content of 3.0 ppb or less per 1% by mass of soy protein, and a ratio of the amount of vanillin to the amount of 1-octen-3-ol (vanillin / 1-octen-3-ol) determined from the peak area in gas chromatography using the headspace method of 0.45 or more. The soymilk of the present invention may, for example, have a soy protein content of 3% by mass or more and a soybean solids concentration of 10% by mass or more. Furthermore, the soymilk of the present invention may, for example, have 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.

[0010] According to the present invention, the soybean solids concentration can be increased without increasing the amount of soybeans blended, and furthermore, the unpleasant odor components derived from soybeans are reduced while maintaining the flavor components of soy milk, thereby obtaining high-concentration soy milk with good flavor and reduced unpleasant odors.

[0011] 1 is a flowchart showing a method for producing soy milk according to an embodiment of the present 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] (First Embodiment) A method for producing soymilk according to a first embodiment of the present invention successively performs 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 a method for producing soymilk according to an embodiment of the present invention. In the method for producing soymilk according to this embodiment, 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]

[0033] 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 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. 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. Also usable are genetically modified soybeans that lack or increase a portion of components contained in soybeans, such as lipoxygenase and saponin, or soybean storage proteins.

[0015] [Solid-liquid separation step S2] In the solid-liquid separation step S2, unsterilized soy milk is obtained by separating the okara from the go obtained in the grinding step S1 by centrifugation, filtration, etc. In order to obtain high-concentration soy milk having a soybean solids concentration of 10% by mass or more, it is preferable that the soybean solids concentration of the unsterilized soy milk after solid-liquid separation (unsterilized soy milk before preheating) be 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 an electric heating method, 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 step 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 the 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 method for producing soy milk of this embodiment, the temperature of the unsterilized soy milk is set to 90°C or higher by 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 the amount of steam directly mixed in. Therefore, from the viewpoint of sterilization efficiency and reducing the amount of steam mixed in, it is preferable that the sterilization be carried out at a liquid temperature (sterilization temperature) of 130 to 160°C for 1 to 90 seconds, and it is more preferable to carry out the sterilization under conditions where the liquid temperature after direct steam mixing is 140 to 160°C.

[0021] [Depressurized Cooling Step 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 carried out 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. As a result, for example, when the soybean solids concentration of unsterilized soy milk before preheating is 6 to 14% by mass, high-concentration sterilized soy milk with a soybean solids concentration of 6.3 to 15% by mass can be obtained. The method for measuring the soybean 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, for example, the method described in Yoshimasa Omura et al., "Effect of Hot Water Treatment on the Flavor of Soy Milk," 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 type sterilization device that is commonly used by those skilled in the art.

[0027] [High-concentration soy milk] Hexanal and 1-hexanol are known to be components that cause the grassy smell of soy milk, and because these components are produced by oxidation of fatty acids contained in soybeans, the more soybeans are used to produce high-concentration soy milk, the greater the amount of components that cause the grassy smell contained in the resulting soy milk. On the other hand, because both hexanal and 1-hexanol are volatile components, it is known that the contents of these components are reduced by vacuum treatment or the like carried out in the production process.

[0028] That is, the soy milk of this embodiment is produced by the method described above, 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, and 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, although 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, although 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 provides 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 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 makes it possible to efficiently concentrate soymilk and remove unpleasant-odor components, thereby producing highly concentrated soymilk with reduced unpleasant odors.

[0032] In conventional production 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 production method of the present embodiment, it is possible to keep the dilution rate of soy milk lower than in conventional production methods, and therefore unpleasant odor components can be sufficiently removed with a single sterilization treatment by the direct steam heating method.

[0033] Second Embodiment Next, soymilk according to a second embodiment of the present invention will be described. The soymilk of this embodiment is produced by the soymilk production method of the first embodiment described above, and has an unpleasant odor component hexanal content of 15 ppb or less per 1% by mass of soy protein, and a 1-octen-3-ol content of 3.0 ppb or less per 1% by mass of soy protein.

[0034] Hexanal and 1-octen-3-ol are odorous components produced by oxidation of fatty acids contained in soybeans, and are the components that cause unpleasant odors in soy milk (soybean-derived grassy, ​​mushroomy, and earthy odors). For this reason, it is preferable that the amounts of hexanal and 1-octen-3-ol in soy milk are low. Specifically, when the hexanal content per 1% by mass of soy protein is 15 ppb or less, or the 1-octen-3-ol content is 3.0 ppb or less, unpleasant odors are less likely to be perceived.

[0035] On the other hand, the soy milk of this embodiment contains at least certain amounts of maltol and vanillin, which are components that impart a good flavor. Specifically, the soy milk of this embodiment has a hexanal content of 15 ppb or less per 1% by mass of soy protein, and a ratio of the amount of maltol to the amount of hexanal (maltol / hexanal) of at least 100. By making the maltol / hexanal ratio at least 100, soy milk with a sweet and pleasant aroma and good flavor can be obtained.

[0036] The "maltol / hexanal ratio" referred to here is a value determined from the peak area of ​​gas chromatography using the headspace method. The upper limit of the maltol / hexanal ratio is not particularly limited, but is preferably 160 or less from the viewpoint of productivity, etc.

[0037] Alternatively, the soymilk of this embodiment has a 1-octen-3-ol content per 1% by mass of soy protein of 3.0 ppb or less, and a ratio of the amount of maltol to the amount of 1-octen-3-ol (maltol / 1-octen-3-ol) of 105 or more, or a ratio of the amount of vanillin to the amount of 1-octen-3-ol (vanillin / 1-octen-3-ol) of 0.45 or more, or both. By making the maltol / 1-octen-3-ol ratio 105 or more and / or the vanillin / 1-octen-3-ol ratio 0.45 or more, soymilk having a sweet, rich, and pleasant aroma and a good flavor can be obtained.

[0038] The "maltol / 1-octen-3-ol ratio" and "vanillin / 1-octen-3-ol ratio" referred to here are values ​​determined from the peak areas of gas chromatography by the headspace method. The upper limits of these component ratios are not particularly limited, but from the viewpoint of productivity, it is preferable that the maltol / 1-octen-3-ol ratio be 200 or less and the vanillin / 1-octen-3-ol ratio be 0.7 or less.

[0039] The ratio of each of the odor components described above can be adjusted, for example, by changing the temperature 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) during soy milk production.

[0040] Furthermore, the soy milk of this embodiment preferably has a maltol content of 1.0 ppm or more per 1% by mass of soy protein, which enhances the sweet aroma derived from soybeans and further improves the flavor of the soy milk.

[0041] Furthermore, when the soy milk of the present embodiment is a high-concentration soy milk, it is preferable that the soy protein content is 3% by mass or more and / or the soy solids concentration is 10% by mass or more, thereby obtaining soy milk with a high component concentration and a rich body and flavor.

[0042] As described above in detail, the soymilk of this embodiment reduces the amount of components that cause unpleasant odors while maintaining the amount of components that provide a sweet and pleasant flavor, and the ratio of these odorous components is set to a specific value or more, thereby achieving soymilk in which the unpleasant odor derived from soybeans is reduced while maintaining the flavor of the soymilk. Each configuration of this embodiment is particularly effective for high-concentration soymilk.

[0043] The effects of the present invention will be specifically described below with reference to examples and comparative examples.

[0044] <First Example> As a first example of the present invention, soy milk of an example and a comparative example were prepared by the method described below, and the amounts of unpleasant odor components contained were compared.

[0045] [Comparative Example 1] Whole soybeans A were ground and then subjected to solid-liquid separation to obtain unsterilized soy milk (soybean solids concentration: 9% by mass). This was preheated by indirect heating with steam until the liquid temperature at the heater outlet reached 80°C, and then sterilized for 1 second or more 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.

[0046] [Comparative Example 2] Whole soybeans A were milled in an amount increased by 20% by mass compared to Comparative Example 1, and then solid-liquid separation was carried out to obtain unsterilized soy milk (soybean solids concentration: 11% by mass). This was preheated by indirect heating with steam until the liquid temperature at the heater outlet reached 80°C, and then sterilized for 1 second or more at 140°C or higher using a steam injection method in which steam is injected. The sterilized 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.

[0047] Example 1 Unsterilized soy milk (soybean solids concentration: 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.

[0048] 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 Comparative Examples 1 and 2 and Example 1 described above, using the same method and conditions as in Comparative Example 1 described above, except that the preheating temperature was 81°C and the reduced pressure cooling temperature was 81°C.

[0049] 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.

[0050] 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.

[0051] 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.

[0052] Example 3 Soy milk with a soy protein content of 4.10% by mass was produced using whole soybeans (whole soybeans C) different from those used in the above-mentioned Comparative Examples 1 to 5 and Examples 1 and 2, using the same method and conditions as in Example 1, except that the preheating temperature was 80°C and the reduced-pressure cooling temperature was 75°C.

[0053] Example 4 Soy milk with a soy protein content of 4.30% by mass was produced using the same whole soybeans C as in Example 3, using the same method and conditions as in Example 1, except that the preheating temperature was 100°C and the reduced pressure cooling temperature was 65°C.

[0054] [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 method described above, 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. Furthermore, for each of the soy milks of Comparative Example 1 and Examples 2 to 4, the 1-octen-3-ol content per 1% by mass of soy protein was determined. Measurement of hexanal, 1-hexanol, and 1-octen-3-ol was carried out with an HSS-GC / MS device using 10 g of soy milk in a 20 ml vial that was sealed. The measurement conditions are shown below.

[0055] (1) HSS conditions Apparatus: 7697A manufactured by Agilent Technologies Oven: Temperature 80°C, stirring for 20 minutes

[0056] (2) GC / MS Conditions Apparatus: Gas Chromatography (GC) 8890 and Mass Spectrometer 5977B manufactured by Agilent Technologies Column: VF-WAXms (length 60 m × inner diameter 0.32 mm × film thickness 0.50 μm) manufactured by Agilent Technologies Column temperature: Hold at 35°C for 5 minutes → Heat to 100°C at 5°C / min → Heat to 240°C at 15°C / min → Hold at 240°C for 4 minutes Carrier gas: Helium Injection mode: Pulsed split mode Injection port temperature: 200°C Transfer line: 240°C Ion source: Temperature 230°C EI mode SIM Parameters: m / z = 56, 57, 69, 72, 82

[0057] (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 areas on the chromatogram using calibration curves with the standard products of each component as external standards. Next, based on the soy protein content of each soy milk, the hexanal content and 1-hexanol content per 1% by mass of soy protein were determined. The results are summarized in Table 1 below.

[0058]

[0059] 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 (liquid temperature difference: 0°C), yet 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.

[0060] Furthermore, the soy milk of Examples 3 and 4, which used whole soybeans C as the soybean raw material, had a higher soy protein content than the soy milk of Comparative Examples 1 and 3, but the hexanal content, 1-hexanol content, and 1-octen-3-ol content per 1% by mass of soy protein were lower.

[0061] 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.

[0062] <Second Example> Next, as a second example of the present invention, the contents of hexanal, 1-octen-3-ol, maltol and vanillin were measured for each of the soymilks of Comparative Example 1 and Examples 2 to 4 of the first example described above, and the maltol / hexanal ratio, maltol / 1-octen-3-ol ratio and vanillin / 1-octen-3-ol ratio were determined.

[0063] Measurement of hexanal, 1-octen-3-ol, maltol, and vanillin was carried out by solvent extraction of 5 g of each soy milk of Examples 2 to 4 and Comparative Example 1 with 5 ml of acetone, and using the obtained extract, solvent extraction-dynamic headspace-gas chromatography-mass spectrometry was carried out. The measurement conditions are shown below.

[0064] (1) DHS conditions: Apparatus: MPS2 manufactured by GERSTEL; Temperature: 80°C; Purge flow rate: 4000 ml

[0065] (2) Thermal desorption conditions Temperature: 300°C Holding time: 10 minutes

[0066] (3) GC / MS Analysis Conditions Apparatus: 5977C GC / MDSD manufactured by Agilent Technologies Column: DB-WAXUI manufactured by Agilent Technologies (length 60 m × inner diameter 0.25 mm × film thickness 0.25 μm) Column temperature: held at 40°C for 3 minutes → heated to 250°C at 6°C / min → held at 250°C for 15 minutes Carrier gas: helium Transfer line: 250°C Ion source temperature: 230°C Quadrupole temperature: 140°C Measurement type: SIM / scan Scan: 29 m / z-300 m / z SIM: 18 m / z

[0067] (4) Calculation of Odor Component Ratio The odor component ratio of each soy milk in Comparative Example 1 and Examples 2 to 4 was calculated from the peak area value of the base ion. Specifically, the peak area value of each component was calculated using hexanal: 56 m / z, 1-octen-3-ol: 57 m / z, maltol: 126 m / z, and vanillin: 151 m / z as base ions. The component ratio was then determined from these peak area values.

[0068] [Evaluation of Flavor] The flavor of each soy milk of Comparative Example 1 and Examples 2 to 4 was evaluated by a five-person analytical sensory evaluation panel (training period: 3 years or more). The evaluation was conducted using the soy milk of Comparative Example 1 with a liquid temperature difference of 0°C as the reference sample, and the degree of difference in flavor from the reference sample (soy milk of Comparative Example 1) was evaluated on the following three-point scale. The evaluation selected by the most number of the five panelists was then used as the overall evaluation. ◎: Much better flavor than the reference sample ○: Better flavor than the reference sample ×: Equivalent to the reference sample

[0069] The results are summarized in Table 2 below. Table 2 also shows the number of panelists who selected each rating.

[0070]

[0071] As shown in Table 2 above, the soymilk of Examples 2 to 4, which had low contents of the unpleasant odor components hexanal and 1-octen-3-ol and in which the maltol / hexanal ratio, maltol / 1-octen-3-ol ratio, and vanillin / 1-octen-3-ol ratio satisfied the requirements of the present invention, had a reduced unpleasant odor compared to the soymilk of Comparative Example 1, in which the ratios of these odor components were outside the ranges of the present invention, but maintained a sweet and pleasant aroma and presented a good flavor.

[0072] From the above results, it was confirmed that the present invention can provide soy milk in which the unpleasant odor derived from soybeans is reduced while maintaining the flavor of soy milk. The configuration of the present invention is particularly suitable for high-concentration soy milk having a high concentration of soybean solids.

Claims

1. A method for producing soy milk, comprising the steps of: preheating unsterilized soy milk, 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 soy milk using a direct steam heating method; and cooling the sterilized soy milk 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 5 to 35°C.

2. The method for producing soy milk 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. A method for producing soymilk according to claim 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. A method for producing soymilk according to any one of claims 1 to 3, wherein the unsterilized soymilk before preheating has a soybean solids concentration of 6 to 14% by mass, and the sterilized soymilk after cooling under reduced pressure has a soybean solids concentration 0.3 to 1% by mass higher than that of the unsterilized soymilk before preheating.

5. Soy milk having a hexanal content of 15 ppb or less per 1% by mass of soy protein, and a ratio of the amount of maltol to the amount of hexanal (maltol / hexanal) calculated from the peak area of ​​gas chromatography using the headspace method of 100 or more.

6. Soy milk in which the 1-octen-3-ol content per 1% by mass of soy protein is 3.0 ppb or less, and the ratio of the amount of maltol to the amount of 1-octen-3-ol (maltol / 1-octen-3-ol) calculated from the peak area of ​​gas chromatography using the headspace method is 105 or more.

7. Soy milk according to claim 5 or 6, wherein the maltol content per 1% by mass of soy protein is 1.0 ppm or more.

8. Soy milk in which the 1-octen-3-ol content per 1% by mass of soy protein is 3.0 ppb or less, and the ratio of the amount of vanillin to the amount of 1-octen-3-ol (vanillin / 1-octen-3-ol) determined from the peak area in gas chromatography using the headspace method is 0.45 or more.

9. Soy milk according to any one of claims 5 to 8, containing 3% by mass or more of soy protein.

10. Soy milk according to claim 9, wherein the hexanal content per 1% by mass of the soy protein is 15 ppb or less and the 1-hexanol content per 1% by mass of the soy protein is 5 ppb or less.

11. Soy milk according to any one of claims 5 to 10, wherein the soybean solids concentration is 10% by mass or more.

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