Full-bean soybean milk having rich bean flavor and preparation method therefor

Abstract

Full-bean soybean milk having rich bean flavor and a preparation method therefor. The preparation method comprises: carrying out steam treatment on soybeans, carrying out ultralow-temperature crushing treatment, and then adding water for boiling soybean milk, so as to obtain full-bean soybean milk having rich bean flavor. The prepared soybean milk is free of beany flavor, has rich bean flavor, is slightly yellow, and has high nutritional value. The process increases the utilization rate of soybeans, shortens the processing period of soybean milk, and improves the product quality.

Description

Whole bean milk with rich bean flavor and preparation method thereof Technical Field

[0001] The invention belongs to the technical field of food processing, and in particular relates to whole bean milk with rich bean flavor and a preparation method thereof. Background Art

[0002] Soy milk is rich in nutrients, with protein, lipid, carbohydrate, and ash contents of approximately 3.6%, 2.0%, 2.9%, and 0.5%, respectively. Despite its nutritional richness, sensory characteristics such as the beany flavor of traditionally prepared soy milk remain a significant factor limiting its widespread acceptance. Currently, a wide variety of soy milk products are available in the domestic market, using a variety of production processes. Consequently, product quality varies widely, with most products exhibiting issues such as insufficient bean flavor, a strong beany odor, and poor color. Processing technology is a key factor influencing soy milk quality.

[0003] At present, the main preparation processes of soy milk are raw pulp process and cooked pulp process. The raw pulp process is to separate the soy milk residue and then boil it, while the cooked pulp process is to boil the soy milk and then separate the residue. The above two processes have the following disadvantages: (1) Soybeans need to be soaked, and the soy milk production cycle is long; (2) During the soaking process, the soybeans undergo complex changes under the action of endogenous enzymes in the soybeans, producing some primary and secondary metabolites, which change the oil free radicals and thus make the prepared soy milk have bad color and flavor. (3) The soybean residue needs to be separated, and the filtration operation causes the rich dietary fiber in the soybean residue to be lost and causes a large amount of protein loss. (4) When the above process is used to prepare whole soybean soy milk, more dietary fiber combines with protein during the heating process, producing larger particles, making the prepared soy milk rough and easy to stratify. Johnson et al. grind soybeans, quickly blanch them, inactivate enzymes, blend, and separate them to make soy milk, but during the grinding process, lipoxygenase catalyzes the hydroperoxidation of polyunsaturated fatty acids, resulting in soy milk with bad color and flavor.

[0004] The key to solving the serious beany smell and poor color in soy milk production is to avoid the production of fat oxidation in soybeans during the soy milk processing process. Chinese invention patent CN202210859473.1 (application number) discloses a method for preparing soy milk with a strong aroma and no beany smell. The soy milk is subjected to step-by-step heat shock on soybeans, and the prepared soy milk has reduced beany smell and produces a rich, sweet and fragrant taste of cereals. Chinese invention patent CN201710299435.4 (application number) discloses a method for making deodorized, low-purine soy milk. The washed soybeans are steamed for 10 to 12 minutes, quickly frozen at low temperature, and then flash-evaporated for 2 seconds. After saturation with oxygen, the soy milk is prepared. The obtained soy milk has a strong beany aroma and no beany smell. However, the filtering operation of the soy milk causes the rich dietary fiber and part of the protein in the bean dregs to be lost, and the nutritional utilization rate is not high, resulting in a large economic loss. Therefore, finding a new method for preparing whole soybean soy milk without beany smell to overcome the defects of the existing technology has broad application prospects.

[0005] Summary of the Invention

[0006] In order to overcome the above-mentioned shortcomings and deficiencies of the prior art, the primary purpose of the present invention is to provide a method for preparing whole soybean milk with rich bean flavor.

[0007] The method of the present invention can prepare whole bean soy milk which does not require soaking treatment, has no beany smell and has a strong bean aroma, improves the taste of the soy milk, improves the color of the soy milk, and shortens the soy milk processing time.

[0008] Another object of the present invention is to provide a whole soybean milk with a strong bean flavor prepared by the above method.

[0009] The purpose of the present invention is achieved through the following solutions:

[0010] A method for preparing whole soybean milk with rich bean flavor comprises the following steps:

[0011] (1) Steam treatment: steaming soybeans to obtain steamed beans;

[0012] (2) Ultra-low temperature pulverization treatment: the steamed beans obtained in step (1) are pulverized at -70 to -196°C to obtain bean powder;

[0013] (3) boiling: boiling the soy flour obtained in step (2) with water to obtain whole bean milk with a strong bean aroma.

[0014] The soybeans in step (1) are full, shiny, uniform in size, free of damage and pests and diseases.

[0015] The soybeans in step (1) are cleaned before steam treatment to remove dust and impurities in the soybeans.

[0016] After the steam treatment in step (1), the soybeans are cooled to room temperature within 60 to 90 seconds.

[0017] The temperature of the steam treatment in step (1) is 100-130° C., and the time of the steam treatment is 1-10 min, preferably 3-7 min.

[0018] Before the crushing in step (2), the steamed beans obtained in step (1) are frozen at -40 to -20°C for 10 to 60 minutes, preferably at -25 to -20°C for 30 minutes.

[0019] The refrigerant used to maintain low temperature during the ultra-low temperature pulverization process in step (2) is liquid nitrogen.

[0020] The rotation speed of the ultra-low temperature pulverization treatment in step (2) is 4000-6000 rpm, and the time is 10-30 minutes.

[0021] The particle size of the soybean powder in step (2) is 0 to 60 μm.

[0022] The mass ratio of the soy flour to water in step (3) is 1:5 to 1:12, preferably 1:7 to 1:10.

[0023] The cooking time of step (3) is 5 to 10 minutes, and the cooking temperature is 90 to 100°C.

[0024] The invention discloses whole bean milk with rich bean aroma prepared by the method.

[0025] The mechanism of the present invention is:

[0026] Heat treatment is a common soybean pretreatment method. Heating inactivates anti-nutritional factors in soybeans while modifying the protein structure and fat distribution of soymilk, improving its taste and stability. Ultra-low temperature grinding not only reduces oxidation during the grinding process, preserving the natural flavor and aroma of soybeans and minimizing pigment damage, but also improves soybean grinding efficiency and imparts a delicate texture to soymilk.

[0027] The present invention uses steam to treat soybeans. During the steaming process, due to the attack of water molecules, the fiber matrix of hemicellulose and cellulose is destroyed, which is beneficial to the grinding of soy milk and the dissolution of substances such as protein and oil. At the same time, the activity of lipoxygenase in soybeans is reduced, preventing oil oxidation, thereby removing the beany smell of soy milk. This is one of the key technologies of the present invention.

[0028] Ultra-low temperature freezing and crushing can crush soybeans at a lower temperature, which can keep the material at a lower temperature, prevent the occurrence of oxidation reactions during the grinding process, reduce the destruction of pigments and the loss of heat-sensitive components, and at the same time make the fiber brittle, making it easier to crush and reducing the impact of dietary fiber on the texture of soy milk. This is another key technology of the present invention.

[0029] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0030] (1) Steam pretreatment of soybeans allows for a rapid influx of water. During the steaming process, the attack of water molecules destroys the fiber matrix of hemicellulose and cellulose, making it easier to grind the soy milk and dissolve substances such as protein and oil, potentially producing soy milk with a rich flavor. At the same time, a large amount of heat enters the soybean tissue, reducing the activity of lipoxygenase in the soybean.

[0031] (2) The preparation method of the present invention not only shortens the processing cycle, but also produces a high dietary fiber content in the prepared soy milk, thereby improving the nutritional value of the product and the utilization rate of soybeans. Ultra-low temperature freezing and pulverization of soybeans not only ensures that the soybeans are at a lower temperature during pulverization, thereby preventing some uninactivated lipoxygenase from catalyzing polyunsaturated fatty acids during the grinding process, but also, due to the circulating freezing of liquid nitrogen, the cellulose in the soybeans becomes brittle and becomes easier to pulverize, thereby preventing the prepared soy milk from containing large particles of fiber, and making the soy milk taste smoother and more delicate.

[0032] (3) The soymilk produced by the present invention has no beany smell, a strong bean aroma, a slightly yellow color, and high nutritional value. The process improves the utilization rate of soybeans, shortens the processing cycle of soymilk, and improves product quality. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] FIG1 is a scanning electron microscope image of soybeans obtained in step S03 of the embodiment and the comparative example.

[0034] FIG2 is a shear rheology diagram of the whole soybean milk obtained in the embodiment and the comparative example.

[0035] FIG3 is an appearance diagram of the whole soybean milk obtained in the embodiment and the comparative example.

[0036] FIG4 is a sensory evaluation chart of the whole soybean milk obtained in the embodiment and the comparative example. DETAILED DESCRIPTION

[0037] The present invention will be described in further detail below with reference to the Examples and accompanying drawings, but the embodiments of the present invention are not limited thereto. Where specific conditions are not specified in the Examples, conventional conditions or conditions recommended by the manufacturer were followed. Reagents or instruments used, where the manufacturer is not specified, are commercially available conventional products.

[0038] Unless otherwise specified, all reagents used in the examples can be purchased from the market.

[0039] Experimental Example 1

[0040] This embodiment provides a whole soybean milk preparation process for improving soybean milk quality, comprising the following steps:

[0041] S01. Material selection: 50.0g of soybeans with plump, shiny, uniform size, no damage, and no pests and diseases are selected as raw material.

[0042] S02. Cleaning: Clean the soybean raw material in step S01 to remove dust and impurities in the soybean.

[0043] S03. Steam treatment: Place the soybeans cleaned in step S02 in steam, remove them, and cool them to room temperature in 60 seconds to obtain steamed beans; wherein the steam temperature is 130°C and the steam treatment time is 1 minute.

[0044] S04. Ultra-low temperature pulverization: The steamed beans obtained in step S03 are quickly frozen at -20°C for 60 minutes. The frozen soybeans are then pulverized in an ultra-low temperature pulverizer using liquid nitrogen as the refrigerant. The temperature is controlled at -196°C and the pulverizer speed is 6000 rpm. The pulverization is performed for 15 minutes to obtain soy flour with a particle size of less than 60 μm.

[0045] S05. Boiling: Add water to the soy flour obtained in step S04 and boil it, wherein the mass ratio of soy flour to water is 1:10, the boiling time is 10 minutes, the boiling temperature is 100°C, and the whole bean milk is obtained after the boiling is completed.

[0046] Example 2

[0047] S01. Material selection: 50.0g of soybeans with plump, shiny, uniform size, no damage, and no pests and diseases are selected as raw material.

[0048] S02. Cleaning: Clean the soybean raw material in step S01 to remove dust and impurities in the soybean.

[0049] S03. Steam treatment: The soybeans cleaned in step S02 are placed in steam, taken out, and cooled to room temperature in 70 seconds to obtain steamed beans; wherein the steam temperature is 130°C and the steam treatment time is 3 minutes.

[0050] S04. Ultra-low temperature pulverization: The steamed beans obtained in step S03 are quickly frozen at -40°C for 10 minutes. The frozen soybeans are placed in an ultra-low temperature pulverizer and pulverized using liquid nitrogen as the refrigerant. The temperature is controlled at -150°C and the pulverizer speed is 5000 rpm. The pulverization is performed for 20 minutes to obtain bean powder with a particle size of less than 60 μm.

[0051] S05. Boiling: Add water to the soy flour obtained in step S04 and boil it, wherein the mass ratio of soy flour to water is 1:7, boil for 10 minutes, and the boiling temperature is 95°C. After the boiling is completed, whole bean milk without beany smell is obtained.

[0052] Example 3

[0053] S01. Material selection: 50.0g of soybeans with plump, shiny, uniform size, no damage, and no pests and diseases are selected as raw material.

[0054] S02. Cleaning: Clean the soybean raw material in step S01 to remove dust and impurities in the soybean.

[0055] S03. Steam treatment: The soybeans cleaned in step S02 are placed in steam, taken out, and cooled to room temperature in 90 seconds to obtain steamed beans; wherein the steam temperature is 120°C and the steam treatment time is 5 minutes.

[0056] S04. Ultra-low temperature pulverization: The steamed beans obtained in step S03 are quickly frozen at -30°C for 30 minutes. The frozen soybeans are then pulverized in an ultra-low temperature pulverizer using liquid nitrogen as the refrigerant. The temperature is controlled at -170°C and the pulverizer speed is 4000 rpm. The pulverization is performed for 25 minutes to obtain soy flour with a particle size of less than 60 μm.

[0057] S05. Boiling: Add water to the soy flour obtained in step S04 and boil it, wherein the mass ratio of soy flour to water is 1:8, the boiling time is 8 minutes, the boiling temperature is 90°C, and the boiling is completed to obtain whole bean milk without beany smell.

[0058] Example 4

[0059] S01. Material selection: 50.0g of soybeans with plump, shiny, uniform size, no damage, and no pests and diseases are selected as raw material.

[0060] S02. Cleaning: Clean the soybean raw material in step S01 to remove dust and impurities in the soybean.

[0061] S03. Steam treatment: The soybeans cleaned in step S02 are placed in steam, taken out, and cooled to room temperature for 80 seconds to obtain steamed beans; wherein the steam temperature is 110°C and the steam treatment time is 7 minutes.

[0062] S04. Ultra-low temperature pulverization: The steamed beans obtained in step S03 are quickly frozen at -25°C for 40 minutes. The frozen soybeans are placed in an ultra-low temperature pulverizer and pulverized using liquid nitrogen as the refrigerant. The temperature is controlled at -100°C and the pulverizer speed is 6000 rpm. The pulverization is performed for 10 minutes to obtain soy flour with a particle size of less than 60 μm.

[0063] S05. Boiling: Add water to the soy flour obtained in step S04 and boil it, wherein the mass ratio of soy flour to water is 1:10, the boiling time is 7 minutes, the boiling temperature is 97°C, and the whole bean milk is obtained after the boiling is completed.

[0064] Experimental Example 5

[0065] S01. Material selection: 50.0g of soybeans with plump, shiny, uniform size, no damage, and no pests and diseases are selected as raw material.

[0066] S02. Cleaning: Clean the soybean raw material in step S01 to remove dust and impurities in the soybean.

[0067] S03. Steam treatment: Place the soybeans cleaned in step S02 in steam, remove them, and cool them to room temperature for 60 seconds to obtain steamed beans; wherein the steam temperature is 100°C and the steam treatment time is 10 minutes.

[0068] S04. Ultra-low temperature pulverization: The steamed beans obtained in step S03 are quickly frozen at -20°C for 30 minutes. The frozen soybeans are then pulverized in an ultra-low temperature ultrafine grinder using liquid nitrogen as the refrigerant at -70°C at a speed of 5000 rpm for 15 minutes. The soybeans are then returned to room temperature to obtain a soy flour with a particle size of less than 60 μm.

[0069] S05. Boiling: Add water to the soy flour obtained in step S04 and boil it, wherein the mass ratio of soy flour to water is 1:10, the boiling time is 5 minutes, the boiling temperature is 90°C, and the whole bean milk is obtained after the boiling is completed.

[0070] Comparative Example 1

[0071] S01. Material selection: 50.0g of soybeans with plump, shiny, uniform size, no damage, and no pests and diseases are selected as raw material.

[0072] S02. Cleaning: Clean the soybean raw material selected in step S01 to remove dust and impurities.

[0073] S03. Bean soaking: Add room temperature water to the soybeans obtained in step S02 for soaking, with the soaking material-liquid ratio being dry beans: room temperature water = 1:3 (unit: g / mL). Add 0.3% (w / v) (unit: g / mL) NaHCO3 to the room temperature water, and soak the soybeans for 10 hours to obtain soaked beans.

[0074] S04. Grinding: The soaked beans obtained in step S03 are passed through a sieve to filter out impurities, and the soaked beans are washed. Water is added to the soaked beans at a mass ratio of 1 (dry beans): 10, and the beans are beaten. The grinding time is 3 minutes, and the beans are ground twice, each time for 1.5 minutes. After a 1-minute interval, the beans are ground again to obtain raw soy milk.

[0075] S05. Boiling: Boil the raw soy milk obtained in step S04 for 10 minutes at a temperature of 100°C to obtain soy milk.

[0076] Comparative Example 2

[0077] S01. Material selection: 50.0g of soybeans with plump, shiny, uniform size, no damage, and no pests and diseases are selected as raw material.

[0078] S02. Cleaning: Clean the soybean raw material in step S01 to remove dust and impurities in the soybean.

[0079] S03. Steam treatment: Place the soybeans cleaned in step S02 in steam, remove them, and cool them to room temperature in 60 seconds to obtain steamed beans; wherein the steam temperature is 130°C and the steam treatment time is 1 minute.

[0080] S04. Conventional low-temperature ultrafine grinding: The steamed beans obtained in step S03 are quickly frozen at -20°C for 60 minutes. The frozen soybeans are then ground in an ultrafine grinder using carbon dioxide as the refrigerant. The temperature is controlled at -18°C and the grinder speed is 6000 rpm. The grinding process is continued for 15 minutes, and the temperature is returned to room temperature to obtain soy flour with a particle size of less than 100 μm.

[0081] S05. Boiling: Add water to the soy flour obtained in step S04 and boil it, wherein the mass ratio of soy flour to water is 1:10, the boiling time is 10 minutes, the boiling temperature is 100°C, and the whole bean milk is obtained after the boiling is completed.

[0082] The soybeans obtained in step S03 of the above Examples 1 to 5 and Comparative Examples 1 to 2 were measured using a scanning electron microscope. The measurement method is as follows:

[0083] (1) Microscopic morphology of soybeans: The microscopic morphology of the soybean seeds obtained in step S03 of the comparative example and the embodiment after treatment was observed using a scanning electron microscope. The soybean seeds after treatment in step S03 of the embodiment and the comparative example were placed in liquid nitrogen for 10 minutes, gently tapped with a hammer to produce a natural cross-section, fixed with 5% (g / mL) glutaraldehyde for 1 hour, rinsed with deionized water for 20 minutes, and the fixed samples were sequentially treated with 70% (mL / mL), 80%, 85%, 90%, and 100% ethanol for 5 minutes for a series of dehydration. The samples were placed at room temperature to evaporate the ethanol for 30 minutes, and then freeze-dried. The dried samples were placed in a vacuum coating machine for gold spraying. The samples were taken out and observed under a scanning electron microscope. The cross-sections of soybean cotyledons treated with different steaming times were scanned with an electron microscope to observe the tissue morphology structure of the treated soybeans.

[0084] The color difference value, shear viscosity and sensory evaluation of the finished soymilk obtained in Examples 1 to 5 and Comparative Examples 1 to 2 were measured as follows:

[0085] (1) Determination of color difference: The color difference of soy milk was measured using a CR-10Plus colorimeter. After calibrating the colorimeter with a standard color plate, a certain amount of soy milk was placed in a white cap for measurement.

[0086] (2) Determination of apparent viscosity of soy milk: The apparent viscosity of soy milk was determined using a Haake rheometer with a C60 / 1° TiL cone-plate rotor (diameter 60.0 mm, gap 52.0 μm), a temperature of 25.0°C, and a time interval of 0.1 to 100 s. -1 Changes in apparent viscosity of soy milk within a range of shear rates.

[0087] (3) Soy milk appearance: Take an appropriate amount of soy milk and place it in a 10 mL centrifuge tube. Take a photo within 3 hours to record its appearance.

[0088] (4) Sensory Evaluation: The evaluation panel consisted of 10 food professional tasters who conducted sensory evaluations of the finished soymilk products in the Examples and Comparative Examples at room temperature. The soymilk flavor evaluation criteria are shown in Table 1. The soymilk was evaluated based on five aspects: color, bean flavor, beany odor, texture, and taste. The average value was used to represent the sample's acceptability. The higher the score, the higher the acceptability. After evaluating each sample, the taster rinsed their mouths three times with clean water and waited 10 minutes before evaluating the next sample to ensure the validity of the results. To better present the test results, the final scores were normalized. All results were multiplied by different coefficients, resulting in a final value of 70 for each indicator.

[0089] Table 1 Soymilk flavor evaluation criteria

[0090] Scanning electron microscopy results of soybeans from the Examples and Comparative Examples are shown in Figure 1. The microstructure of soybean seeds treated solely with soaking (Comparative Example 1) was relatively stretched and loose, while the cross-section of cells after steam treatment was elongated and arranged in a tight network structure, with each cell surrounded by a cell membrane. The spherical structures were oil bodies and protein bodies. In soybeans not subjected to steam treatment, as in Comparative Example 1, the protein bodies present were surrounded by a cytoplasmic protein network embedded in the spherical oil bodies. The particles were small and tightly bound together. After steam treatment, as in Comparative Example 2 and Examples 1-5, the structure of the oil bodies and proteins in the soybeans was gradually destroyed, the spherical shape of the protein bodies was slightly deformed, and the particles aggregated. In addition, the cytoplasmic network and the surface of the wrinkled cell wall were exposed, possibly due to the destruction of the oil bodies or the partial diffusion of the internal lipids. After steam treatment, the pulping process makes the protein and lipids in the soybeans more easily dissolve, and the prepared soymilk has a richer taste.

[0091] Table 2 Color difference between Examples 1 to 5 and Comparative Examples 1 to 2

[0092] Note: Different superscript lowercase letters in the same column indicate significant differences (p<0.05).

[0093] The color difference of soy milk was measured using a CR-10Plus colorimeter, and the results are shown in Table 2. The L* value indicates the brightness of the color. The larger the value, the closer it is to white, and the smaller the value, the closer it is to black. The a* value indicates the red-green degree of the color. The larger the value, the closer it is to red, and the smaller the value, the closer it is to green. The b* value indicates the yellow-blue degree of the color. The larger the value, the closer it is to yellow, and the smaller the value, the closer it is to blue. When soy protein is heat-treated under neutral conditions, the color change is mainly due to the fact that hydroxyl compounds and amino compounds generate brown-black macromolecular substances - melanoidins through the Maillard reaction. At the same time, the change in soy milk color is also related to the pigments in soybeans. The color values ​​of the soy milks of the comparative example and the example are shown in Table 2. There is no significant difference in L* of the soy milk obtained after steam treatment, and its b* value is between 0.1% and 0.2%.

[0094] There were no significant differences between Examples 2, 3, and 4, but the b* value increased compared to the soymilk in Comparative Example 1 that was not steam-treated or insufficiently steam-treated. Example 5 had a higher b* value due to the long steam treatment time. Under the same steam treatment time conditions, the a* and b* values ​​of the soymilk from ultra-low temperature grinding (Example 1) increased compared to the soymilk from ordinary low temperature grinding (Comparative Example 2), possibly because the ultra-low temperature treatment reduced the destruction of the pigment. Compared to Comparative Example 1, the brightness and a* values ​​of all whole bean soymilks decreased, while the b* values ​​increased. As can be seen from Figure 3, the color of the soymilk changed from brown to light yellow. This may be because the protein in the soymilk prepared by steam treatment and freeze grinding was partially denatured, and some amino groups were embedded in the interior of the protein aggregates, reducing the exposed amino groups, resulting in a low degree of Maillard reaction, and thus the brown color of the prepared soymilk disappeared. Protein denaturation and the presence of larger particle size fibers can also cause the brightness of the soymilk to decrease. Tryptophan content is also related to the browning effect of soymilk. Steaming degrades tryptophan in soymilk, slowing the Maillard reaction and resulting in a lower a* value and an increased b* value. Furthermore, steaming denatures some proteins attached to liposomes, releasing fat, which may also contribute to an increase in the b* value and the release of more oil bodies during the grinding process.

[0095] Viscosity value (η) is an important indicator for evaluating fluid flow properties. It is expressed as the relative resistance to liquid flow, that is, the internal friction between molecules, and is expressed in fluid mechanics as the ratio of shear rate to shear stress. The results of the soymilk shear viscosity test of the embodiments and comparative examples are shown in Figure 2. The traditional soaked soymilk and the whole bean soymilk samples with a strong bean aroma are all Newtonian fluids. Within the range of 1-100mP.s, soymilk with a higher viscosity may make the mouthfeel more dense, produce a stronger tactile sensation in the throat, and the mouthfeel stays in the mouth for a longer time, bringing a more rich taste experience of soymilk bean aroma. When the boiling water ratio is the same, when steaming for 10min (Example 5), steaming for 7min (Example 4), steaming for 1min (Example 1) and not steaming (Comparative Example 1), Example 5 has a higher viscosity, and the viscosity of the soymilk prepared by steaming is higher than that of the soaked soymilk. As the heating treatment time increases, the soymilk viscosity shows an increasing trend. However, when the steaming time is short, such as in Comparative Example 2, the shear viscosity is not much different from the soymilk prepared by the traditional process (Comparative Example 1). Soymilk viscosity decreases with increasing shear rate, exhibiting shear-thinning properties. This is because intermolecular bonding forces form a network structure in soymilk, but this structure is disrupted under high shear forces, resulting in a decrease in soymilk viscosity. Furthermore, the pH of soymilk prepared by steam treatment (shown in Table 2) is higher than that of soymilk prepared by soaking, which may also contribute to the increase in viscosity. Heating denatures proteins, exposing hydrophobic groups and causing some protein particles to become loose and disordered from a dense structure. Furthermore, heating accelerates particle movement and increases collisions between protein molecules. Longer steam treatment times lead to greater fat dissolution, resulting in increased soymilk viscosity.

[0096] The sensory evaluation results of the soymilk of the Examples and Comparative Examples are shown in Figure 4. The flavor of soymilk is primarily formed by the degradation of unsaturated fatty acids by lipoxygenase and hydroperoxidase to form small molecules such as aldehydes, alcohols, ketones, and esters. Compared to Comparative Example 1, the sensory evaluation of the samples of Examples 2, 3, and 4 was significantly improved, with the beany odor of the soymilk almost eliminated and a strong bean flavor. However, the steam treatment time of Example 1 was too short, which resulted in insufficient inactivation of the lipoxygenase in the soybeans. Low temperatures can inhibit enzyme activity. After ultrafine grinding, the soy flour returned to room temperature during the process of lipoxygenase-catalyzed oxidation, resulting in a brownish color and a beany odor. Ultrafine grinding at a normal low temperature in Comparative Example 2 failed to achieve the effect of fiber embrittlement, making the fibers difficult to pulverize. A longer grinding time was required, and the particle size of the soy flour after pulverization was still large, resulting in a strong grainy texture in the prepared soymilk. The steam treatment time of Example 5 was too long, resulting in severe protein aggregation, a reduced texture of the soymilk, and a grainy texture.

[0097] Proteins can improve product flavor by binding to flavor compounds through hydrophobic interactions. During heating, proteins denature, enhancing their ability to bind hexanal and other substances. Heat-denatured proteins are 2-3 times more capable of binding hexanal than natural proteins. Therefore, soymilk prepared with steam treatment has a lower beany odor. Ultra-low temperature grinding keeps soybeans at a lower temperature, preventing heat generation during grinding that can lead to fat oxidation. It also brittles the fibers, making them easier to grind, reducing the impact of dietary fiber on the texture of soymilk and resulting in a better taste.

[0098] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be considered as equivalent replacement methods and are included in the scope of protection of the present invention.

Claims

1. A method for preparing whole bean milk with strong bean flavor, characterized in that The steps include: (1) Steam treatment: steaming soybeans to obtain steamed beans; (2) Ultra-low temperature pulverization treatment: the steamed beans obtained in step (1) are pulverized at -70 to -196°C to obtain bean powder; (3) boiling: boiling the soy flour obtained in step (2) with water to obtain whole bean soy milk with a strong bean flavor.

2. The preparation method according to claim 1, characterized in that: After the steam treatment in step (1), the soybeans are cooled to room temperature within 60 to 90 seconds.

3. The preparation method according to claim 1, characterized in that: The temperature of the steam treatment in step (1) is 100-130° C., and the time of the steam treatment is 1-10 min, preferably 3-10 min.

4. The preparation method according to claim 1, characterized in that: The refrigerant used to maintain low temperature during the ultra-low temperature pulverization process in step (2) is liquid nitrogen.

5. The preparation method according to claim 1, characterized in that: The rotation speed of the ultra-low temperature pulverization treatment in step (2) is 4000-6000 rpm, and the time is 10-30 minutes.

6. The preparation method according to claim 1, characterized in that: The particle size of the soybean powder in step (2) is 0 to 60 μm.

7. The preparation method according to claim 1, characterized in that: Before the crushing in step (2), the steamed beans obtained in step (1) are frozen at -40 to -20°C for 10 to 60 minutes.

8. The preparation method according to claim 1, characterized in that: The mass ratio of the soy flour to water in step (3) is 1:5 to 1:

12.

9. The preparation method according to claim 1, characterized in that: The boiling time of step (3) is 5 to 10 minutes, and the boiling temperature is 90 to 100°C.

10. A whole bean milk with strong bean flavor prepared by the method according to any one of claims 1 to 9.

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