A high-fiber soy milk with suspension stability and full utilization of dietary fiber and a processing method thereof

Abstract

This invention belongs to the field of food processing technology, and more specifically relates to a high-fiber soymilk with stable dietary fiber suspension and its processing method. This invention improves the soybean protein dissolution rate and dietary fiber content of the raw pulp by improving the soybean grading and micro-grinding and gradient filtration process. Based on a multi-component composite modification method combining high-temperature microwave polarization effect and enzymatic hydrolysis, it degrades the dietary fiber in soybean residue to form thermally stable microfibers. This is synergistically combined with negatively charged anionic polysaccharide xanthan gum, which improves the suspension stability of the high-fiber soymilk after sterilization by increasing the spatial extension specific surface area of ​​the dietary fiber and enhancing the electrostatic interaction force of the dietary fiber system. This overcomes the problems of unstable dispersion and easy sedimentation of dietary fiber powder in soymilk beverages. This invention achieves full utilization of soybeans in soymilk processing, effectively reduces soymilk processing by-products, and improves the nutritional value and added value of soymilk.

Description

Technical Field

[0001] This invention belongs to the field of food processing technology, and more specifically relates to a suspension-stabilized high-fiber soy milk with full utilization of dietary fiber and its processing method. Background Technology

[0002] my country is the origin of soybeans, and its annual soybean production is currently around 164 million tons, earning it the title of "Hometown of Soybeans." Soy milk, a traditional Chinese plant-based protein beverage, has been proven through amino acid evaluation to be the only plant protein that is a complete protein similar to animal protein, possessing high nutritional value. Studies have shown that among adults in East Asia with lactose intolerance, the incidence of lactose malabsorption after consuming cow's milk is as high as 86.7%, with a lactose intolerance index of 0.9. The intolerance rate is higher in southern regions than in northern regions. Therefore, soy milk is more suitable than cow's milk as an important traditional source of high-quality protein for urban and rural residents in my country. Currently, "refined processing" has become the trend in the food industry. Soy milk and soy pulp undergo multiple filtration processes to obtain smooth, refreshing, tender, and palatable plant-based protein products. However, the dietary fiber-rich soy pulp byproduct is largely discarded or sold as cheap animal feed, resulting in a lack of dietary fiber in soy milk products. In recent years, with the increasing health awareness of consumers, a "back to basics" diet has gradually gained acceptance. However, low-sugar, high-fiber soy milk drinks that align with healthy eating often lack an ideal taste and flavor. This is primarily because the dietary fiber in soy pulp has a rough texture and tends to agglomerate and settle upon heating, requiring the addition of various food emulsifiers to form a stable emulsion system. Furthermore, this conflicts with contemporary consumers' pursuit of "simple and clean" labeled, hygienic foods.

[0003] Currently, there are reports in China of preparing nano-sized dietary fiber powder through physical and chemical methods. The national invention patent "A Bamboo Shoot Dietary Fiber Yogurt and Its Preparation Method" (CN201610795883.9) discloses a method for preparing water-soluble dietary fiber from bamboo shoots using ultra-fine grinding, juicing, and enzymatic hydrolysis with water extraction. This method can be used as a composite stabilizer in yogurt processing to reduce whey precipitation. This method degrades some large-particle insoluble dietary fiber and separates soluble dietary fiber, thereby eliminating the rough texture caused by insoluble dietary fiber. However, the yield of soluble dietary fiber extracted from plant raw materials is low, and the separation and drying process is complex, limiting its application in modern food processing. Another national invention patent, "A Multifunctional Grapefruit Peel Soluble Dietary Fiber Goat Milk Beverage and Its Preparation Method" (CN202010826690.1), discloses a method for extracting soluble dietary fiber from grapefruit peel using microwave-ultrasound combined with alcohol precipitation. The grapefruit peel soluble dietary fiber is evenly dispersed in the milk system, supplementing the insufficient dietary fiber content in animal protein drinks. Another national invention patent, "Soymilk Production Process Rich in Natural Dietary Fiber Without Additives or Processing Aids" (CN202110703297.8), discloses a method for producing high-fiber soymilk using ultra-fine grinding, without filtration, and without adding processing aids. The soymilk products prepared by this method have a high dietary fiber content, but still have problems such as a rough taste and easy fiber sedimentation affecting product quality.

[0004] Currently, most commercially available high-fiber plant-based protein drinks supplement their dietary fiber content by adding low-viscosity soluble food additives. Reports on key technologies for utilizing insoluble plant residues—byproducts of raw material processing—to supplement dietary fiber in plant-based protein drinks are limited. Furthermore, whole-grain high-protein drinks, due to their high insoluble dietary fiber content, still face unresolved technical challenges during heat sterilization, including heat-induced agglomeration, layering, unstable suspension, and a less refined texture. Summary of the Invention

[0005] In view of the above-mentioned technical problems in the background technology, there is a need to provide a suspension-stabilized high-fiber soymilk with full utilization of dietary fiber and its processing method, so as to provide a high-fiber soymilk processing method with strong continuous operability and high efficiency, while overcoming the bottleneck problems such as easy agglomeration and sedimentation of fiber when heated and unsmooth taste during the processing of high-fiber soymilk, and improving the thermal stability and suspension ability of dietary fiber in soybean residue in soymilk, enhancing the mellow and silky taste of soymilk, reducing the amount of food emulsifiers (such as xanthan gum) used in traditional soymilk, and making the plant protein beverage formula label cleaner and returning to its natural attributes.

[0006] To achieve the above objectives, the inventors provide a processing method for suspension-stabilized high-fiber soy milk with full utilization of dietary fiber, comprising the following steps:

[0007] Soaking and rehydration: Soak peeled soybeans in food processing water overnight to obtain soaked peeled soybeans;

[0008] Hot grinding: The soaked and peeled soybeans are added to processing water at 80-85℃ at a mass-to-volume ratio of 1:5-6, and baking soda is added. The mixture is then graded, ground, and filtered. The filtration process includes filtering the graded and ground soybean milk using filter screens of different mesh sizes to obtain raw soy milk and soybean residue.

[0009] Soybean residue nano-micro processing: After washing and filtering the soybean residue, a suspension with a mass concentration of 10-20 g / L is prepared and subjected to ultrasonic-pressure heat modification treatment to obtain a modified soybean residue suspension; the modified soybean residue suspension is subjected to enzymatic hydrolysis, solid-liquid separation, and freeze-drying to obtain nano-micro soybean residue dietary fiber.

[0010] Preparation: Adjust the protein concentration of the original pulp to 4.0g / 100g with water, add glyceryl monostearate, xanthan gum, and white sugar, set the speed to 5000-5500rpm, and perform the first emulsification and shearing for 10-20min. Add the nano-micro soybean residue dietary fiber, and perform the second emulsification and shearing for 5-10min at the same speed to obtain the prepared soy milk.

[0011] Defoaming and high-pressure homogenization: The prepared soy milk is subjected to defoaming and high-pressure homogenization to obtain high-fiber soy milk crude product;

[0012] The high-fiber soy milk crude product is bottled, sterilized, cooled, and refrigerated to obtain the high-fiber soy milk with stable dietary fiber suspension.

[0013] Peeled soybeans refer to soybeans that have undergone a peeling process and can be used in the processing of various soy products, such as soy milk, tofu, tofu skin, and dried bean curd sticks. Peeled soybeans show significant improvements in taste, nutritional value, and processing characteristics. In this invention, pre-processed peeled soybeans can be purchased directly, or peeled soybeans can be prepared in advance using wet or dry peeling methods.

[0014] The transportation and storage of purchased peeled soybeans are prone to spoilage or contamination. Therefore, this invention preferably uses a dry peeling method to prepare peeled soybeans in-house. The peeled soybeans are prepared according to the following steps:

[0015] Select whole, high-quality soybeans for dehulling. The dehulling process is carried out under the following conditions: hot air drying temperature of 80-95℃ for 8-10 minutes, followed by cooling and then machine grinding at a pressure of -0.1MPa and a rotation speed of 3500rpm to obtain the dehulled soybeans.

[0016] The above-mentioned method for preparing peeled soybeans can not only reduce energy consumption and wastewater in the production process and improve production efficiency, but also retain the rich and mellow soybean flavor to a greater extent.

[0017] As a preferred embodiment of the present invention, in the soybean residue nano-microprocessing step:

[0018] The working conditions for microwave-pressure heating modification are as follows: microwave reactor pressure heating temperature is 125-130℃, ultrasonic power is 800-1000W, and reaction time is 60min.

[0019] As a more preferred embodiment of the present invention, in the soybean residue nano-microprocessing step:

[0020] The enzymatic hydrolysis uses cellulase at a dosage of 0.3-0.5%, with a reaction pH of 4.5-5.0, a temperature of 50-55℃, and a reaction time of 12-18 hours. After this treatment, the yield of nano-micronized dietary fiber is approximately 80%, which can then be used to produce high-fiber soymilk. According to calculations, producing 1 ton of ordinary soymilk requires approximately 125 kg of soybeans. Grinding 125 kg of soybeans yields approximately 50 kg of dried soybean residue. After nano-micronization treatment, this residue can produce 40 kg of dietary fiber. Based on a 2.0% nano-micronized dietary fiber content in the soybean residue, this is sufficient for the production of 2 tons of high-fiber soymilk, essentially achieving full utilization of soybean dietary fiber and significantly increasing the yield of high-fiber soymilk.

[0021] As a preferred embodiment of the present invention, in the preparation step, the amount of glyceryl monostearate added is 0.1-0.15% based on the total mass percentage of the high-fiber soy milk, the amount of xanthan gum is 0.03-0.05%, and the amount of nano-micro soybean residue dietary fiber is 1.5-2.0%.

[0022] In a preferred embodiment of the present invention, in the hot grinding step, the amount of baking soda used is 0.05-0.08% based on the total mass percentage of the soaked, peeled soybeans and the aqueous solution; the graded grinding includes:

[0023] First-stage grinding: 6000-8000 rpm, grinding time: 10 minutes; and

[0024] Two-stage grinding, with a speed of 8000-12000 rpm and a grinding time of 15 minutes.

[0025] As a preferred embodiment of the present invention, in the hot grinding step, the filtration is carried out using a combination of filter screens with mesh sizes of 60 mesh, 80 mesh, 120 mesh, 150 mesh and 200 mesh for graded filtration, so that the protein concentration in the obtained pulp is 6.0-8.0g / 100g and the dietary fiber content is 0.6-1.0g / 100g. Thus, the mass of insoluble soybean residue dietary fiber after graded filtration (on dry weight, per 100g pulp) is 4.0-6.0g.

[0026] As a preferred embodiment of the present invention, the high-pressure homogenization pressure is 45±1MPa, and the homogenization is performed more than once; the sterilization is performed by spraying the bottled high-fiber soy milk after filling, with a sterilization temperature of 121℃ and a sterilization time of 20min.

[0027] As a preferred embodiment of the present invention, the cooling is achieved by spray cooling, and the tank temperature is controlled at 45±3℃.

[0028] In a second aspect, the inventors provide a suspension-stabilized high-fiber soy milk with full utilization of dietary fiber, which is processed using the processing method described in the first aspect of the present invention.

[0029] Unlike existing technologies, the above technical solution has at least the following beneficial effects:

[0030] First, this invention increases the solubility of soybean protein to 94% through slightly alkaline multi-stage grinding and gradient filtration technology, thereby effectively utilizing the protein nutrients in soybeans and reducing the cost of soy milk production. At the same time, it increases the dietary fiber content of soy milk pulp to 1.0g / 100g, laying a high-quality raw material foundation for the production of high-fiber soy milk.

[0031] Secondly, this invention differs from existing micron-level dietary fiber pulverization technologies. By using microwave-pressure heating pretreatment to assist enzymatic hydrolysis of cellulose, it can simultaneously degrade the size of dietary fiber particles and promote microfibrillation, altering the morphology of the dietary fiber to form microfibrils with a length of micrometers (10-30 μm) and a diameter of nanometers (10-40 nm). Compared to traditional granular nanofibers, these microfibrils exhibit stronger thermal stability and greater spatial extensibility. This effectively reduces the phenomenon of fiber agglomeration and sedimentation caused by hydrogen bonding during thermal processing due to particle breakage and size reduction, which leads to the exposure of numerous hydrophilic groups.

[0032] Furthermore, this invention employs a simple, low-dose combination of food additives (glyceryl monostearate and xanthan gum) to mitigate the aggregation of dietary fiber under thermodynamically unstable conditions through electrostatic repulsion and surface activity. The high-fiber soy milk product uses fewer additives, meeting modern consumers' demand for green and clean foods. Moreover, after being stored at room temperature (25°C) for 60 days, the high-fiber soy milk maintains a stability index above 90%, with moderate viscosity and a smooth texture.

[0033] In summary, this invention uses soybean residue, a byproduct of soybean milk processing, as the source of dietary fiber, and water as the reaction system. It employs a combination of microwave-pressure heating reaction and enzymatic hydrolysis of cellulose for nano-micronization modification. The nano-micronized dietary fiber is then separated and collected using a tubular centrifuge and added back to the soybean milk. This achieves the full utilization of soybean processing byproducts. The processing method has the advantages of being continuous and clean. The high-fiber soybean milk product produced by this method has the characteristics of strong stability, moderate viscosity, delicate taste, and rich soybean aroma. Attached Figure Description

[0034] Figure 1 This is a schematic diagram showing the particle size distribution of nano-sized soybean residue dietary fiber in Comparative Examples 1-2 and Examples 1-4 of the present invention.

[0035] Figure 2 Microstructure diagrams of nano-sized soybean residue dietary fiber observed by field emission electron microscopy for Comparative Examples 1-2 and Examples 1-4 of the present invention;

[0036] Figure 3 For comparison of the apparent viscosity of high-fiber soy milk in Comparative Examples 1-2 and Examples 1-4 of the present invention. Detailed Implementation

[0037] To illustrate the technical content, structural features, objectives, and effects of the technical solution in detail, the following description is provided in conjunction with specific embodiments and accompanying drawings. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of this application.

[0038] In this document, the term "embodiment" means that a specific feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The term "embodiment" appearing in various places throughout the specification does not necessarily refer to the same embodiment, nor does it specifically limit its independence or connection with other embodiments. In principle, in this application, as long as there are no technical contradictions or conflicts, the technical features mentioned in each embodiment can be combined in any way to form corresponding implementable technical solutions.

[0039] Unless otherwise defined, the technical terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the use of related terms herein is merely for the purpose of describing particular embodiments and is not intended to limit this application.

[0040] In the description of this application, the term "and / or" is used to describe the logical relationship between objects, indicating that three relationships can exist. For example, A and / or B means: A exists, B exists, and A and B exist simultaneously. Additionally, the character " / " in this document generally indicates that the preceding and following objects have an "or" logical relationship.

[0041] In this application, terms such as “first” and “second” are used only to distinguish one entity or operation from another, and do not necessarily require or imply any actual quantity, hierarchy or order relationship between these entities or operations.

[0042] Unless otherwise specified, the use of terms such as “comprising,” “including,” “having,” or other similar expressions in this application is intended to cover non-exclusive inclusion, which does not exclude the presence of additional elements in a process, method, or product that includes the stated elements, such that a process, method, or product that includes a list of elements may include not only those defined elements but also other elements not expressly listed, or elements inherent to such a process, method, or product.

[0043] As understood in the Examination Guidelines, in this application, expressions such as "greater than," "less than," and "exceeding" are understood to exclude the stated number; expressions such as "above," "below," and "within" are understood to include the stated number. Furthermore, in the description of the embodiments in this application, "multiple" means two or more (including two), and similar expressions related to "multiple" are also understood in this way, such as "multiple groups" and "multiple times," unless otherwise explicitly specified.

[0044] In the description of the embodiments of this application, the space-related expressions used, such as "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "vertical," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential," indicate the orientation or positional relationship based on the orientation or positional relationship shown in the specific embodiments or drawings. They are only for the purpose of describing the specific embodiments of this application or for the reader's understanding, and do not indicate or imply that the device or component referred to must have a specific position, a specific orientation, or be constructed or operated in a specific orientation. Therefore, they should not be construed as limitations on the embodiments of this application.

[0045] Unless otherwise expressly specified or limited, the terms "installation," "connection," "linking," "fixing," and "setting," as used in the description of the embodiments of this application, should be interpreted broadly. For example, "connection" can be a fixed connection, a detachable connection, or an integral setting; it can be a mechanical connection, an electrical connection, or a communication connection; it can be a direct connection or an indirect connection through an intermediate medium; it can be the internal connection of two components or the interaction between two components. For those skilled in the art to which this application pertains, the specific meaning of the above terms in the embodiments of this application can be understood according to the specific circumstances.

[0046] In existing technologies, whole-grain high-protein beverages, due to their high content of insoluble dietary fiber, still face technical challenges during heat sterilization, such as heat agglomeration, layering, unstable suspension, and a rough texture. To form a stable emulsion system, various food emulsifiers are typically added to enhance stability and apparent viscosity. However, this not only fails to increase the soluble dietary fiber content but also reduces the natural, green, and healthy characteristics of high-protein beverages. To address these issues, the inventors actively explored nano-micronization of the insoluble polysaccharides from soybean residue processing byproducts, followed by enzymatic hydrolysis to obtain fibrous nano-micronized soybean residue dietary fiber. Furthermore, they actively explored minimizing the addition of external food gums and other additives to ensure the high dietary fiber content and suspension stability of high-fiber soy milk while maintaining its green, natural, and healthy beverage characteristics.

[0047] Unless otherwise specified, the reagents and instruments used in this invention are all commonly used in this technical field.

[0048] Example 1

[0049] A processing method for a suspension-stabilized high-fiber soy milk beverage with full utilization of dietary fiber includes the following steps:

[0050] Mechanical peeling of soybeans: Select whole soybeans of good quality for peeling treatment. Set the hot air drying temperature to 80℃ and process for 10 minutes. After cooling, machine-mill peeling is carried out under a pressure of -0.1MPa and a speed of 3500rpm. In other different embodiments, commercially available peeled soybeans can also be used. However, in this embodiment, in order to obtain a more mellow soybean aroma, peeled soybeans are produced by hot air mechanical peeling of soybean raw materials.

[0051] Soaking and rehydration: Peeled soybeans and food processing water are soaked overnight at a mass-to-volume ratio of 1:5, that is, 300g of peeled soybeans are soaked in 1500g of food processing water to obtain soaked and rehydrated peeled soybeans.

[0052] Hot grinding: The mass-to-volume ratio of soaked and peeled soybeans to processing water is 1:5, that is, 400g of soaked and peeled soybeans are added to 2000mL of processing water at 85℃, and then 1.2g of baking soda is added. The soybeans are then subjected to primary grinding (coarse grinding) at 6000rpm for 10min. Then, secondary grinding (fine grinding) is performed at 10000rpm for 15min.

[0053] Filtration and Boiling: After grinding, filter the ground soy milk through 60-mesh, 100-mesh and 150-mesh silk cloth filters in sequence to obtain raw soy milk and soy pulp; boil the filtered raw soy milk once until the foam disappears and set aside.

[0054] Soybean residue nano-micronization treatment: After filtering the soybean milk from grinding, the soybean residue was washed and filtered again, and then a 20 g / L soybean residue suspension solution (5 L) was prepared. This suspension was placed in a microwave reactor for microwave-pressure heating modification treatment. The ultrasonic power was 800 W, the reaction temperature was 125℃, and the time was 1 h, resulting in a modified soybean residue suspension. After the reaction was completed, the pH of the modified soybean residue suspension was adjusted to 5.0, and 25 g of cellulase was added for enzymatic hydrolysis. The hydrolysis temperature was controlled at 55℃ for 12 h. Then, a tubular centrifuge was used to separate the residue at 10000 rpm to obtain nano-micronized dietary fiber. The nano-micronized dietary fiber was freeze-dried and then ground for 5 h using a low-temperature rod mill to obtain nano-micronized soybean residue dietary fiber. The yield of nano-micronized soybean residue dietary fiber was calculated to be approximately 80%. The fiber was then dried and sealed for storage.

[0055] Preparation: Take 500g of raw soy milk into a mixing tank, maintain the temperature of the raw soy milk at 85℃, and add 2.5g of glyceryl monostearate, 0.80g of xanthan gum, and 100g of fine white sugar in sequence. Glyceryl monostearate and xanthan gum need to be mixed evenly with the white sugar before adding them together. After they are evenly dissolved, set the speed of the emulsifying shear machine to 5500rpm and emulsify and shear for 15min. Then mix it evenly with the remaining 1000g of raw soy milk and 500g of production water, add 35g of nano-micronized soybean residue dietary fiber, and emulsify and shear at 8000rpm for 5min to obtain the prepared soy milk.

[0056] High-pressure homogenization: After defoaming the prepared soy milk, it is subjected to high-pressure homogenization. The material temperature is 60℃, the processing pressure is 45MPa, and the homogenization is performed twice.

[0057] Filling and sterilization: The homogenized soy milk is filled into PP bottles and then subjected to horizontal spray sterilization at a temperature of 121℃ for 20 minutes.

[0058] Cooling: After the soy milk is filled and sterilized, it is shaken evenly and then sprayed to cool it down to 40-45°C. Then it is transferred to room temperature for storage to obtain the dietary fiber suspension-stable high-fiber soy milk.

[0059] Example 2

[0060] A processing method for a suspension-stabilized high-fiber soymilk beverage with full utilization of dietary fiber differs from Example 1 in that the initial grinding speed of soybeans is 8000 rpm for 10 min, and the fine grinding speed is 12000 rpm for 15 min. In the soybean residue nano-micronization treatment step, the microwave power is 800W, the reactor temperature is 130℃, the time is 60 min, and the cellulose enzymatic hydrolysis time is 15 h. On the other hand, in the ingredient preparation step, 2.5 g of glyceryl stearate, 0.8 g of xanthan gum, and 100 g of white sugar are used; 35 g of nano-micronized soybean residue dietary fiber powder is weighed out. All other steps are the same as in Example 1, resulting in the high-fiber soymilk product.

[0061] Example 3

[0062] A processing method for a suspension-stabilized high-fiber soymilk beverage with full utilization of dietary fiber differs from Example 1 in that the initial grinding speed of soybeans is 6000 rpm for 10 min, and the fine grinding speed is 12000 rpm for 15 min. In the nano-micronization treatment step of soybean residue, the microwave power is 1200W, the reaction vessel temperature is 130℃, the time is 60 min, and the cellulose enzymatic hydrolysis time is 18 h. In addition, in the ingredient preparation step, 3.0 g of glyceryl stearate, 1.0 g of xanthan gum, and 100 g of white sugar are used; 40 g of nano-micronized soybean residue dietary fiber powder is weighed out. All other steps are the same as in Example 1 to obtain the high-fiber soymilk product.

[0063] Example 4

[0064] A processing method for a suspension-stabilized high-fiber soymilk beverage with full utilization of dietary fiber differs from Example 1 in that the initial grinding speed of soybeans is 8000 rpm for 10 min, and the fine grinding speed is 15000 rpm for 15 min. In the nano-micronization treatment step of soybean residue, the microwave power is 1200W, the reaction vessel temperature is 130℃, the time is 60 min, and the cellulose enzymatic hydrolysis time is 18 h. In addition, in the ingredient preparation step, 3.0 g of glyceryl stearate, 1.0 g of xanthan gum, and 100 g of white sugar are used; 40 g of nano-micronized soybean residue dietary fiber powder is weighed out. All other steps are the same as in Example 1 to obtain the high-fiber soymilk product.

[0065] Comparative Example 1

[0066] A method for processing soy milk beverage, comprising the following steps:

[0067] Mechanical peeling of soybeans: Select whole, high-quality soybeans for peeling. Set the hot air drying temperature to 80℃ and process for 10 minutes. After cooling, peel the soybeans by grinding under a pressure of -0.1MPa and a speed of 3500rpm.

[0068] Soaking and rehydration: Peeled soybeans and food processing water are soaked overnight at a mass-to-volume ratio of 1:5, that is, 300g of peeled soybeans are soaked in 1500g of food processing water to obtain soaked and rehydrated peeled soybeans.

[0069] Hot grinding: The mass-to-volume ratio of soaked and peeled soybeans to processing water is 1:5, that is, 400g of soaked and peeled soybeans are added to 2000mL of processing water at 85℃, and then 1.2g of baking soda is added. The soybeans are coarsely ground using a grinder at 5000rpm for 10min. Then, a secondary grinding process, namely fine grinding, is carried out at 8000rpm for 15min.

[0070] Filtration and Boiling: After grinding, the soy milk is filtered through 60-mesh, 120-mesh and 200-mesh silk cloth filters respectively. The filtered soy milk is boiled once and the foam disappears before it is set aside as raw soy milk.

[0071] Preparation of dietary fiber from soybean residue: After grinding and filtering, the soybean residue is washed and filtered with water, then freeze-dried, and then ground for 5 hours using a low-temperature rod mill to obtain nanofiber powder, which is then dried and sealed for storage.

[0072] Mixing and dissolving: Take 500g of raw soy milk and heat it to 85℃ in a mixing tank. Add 2.5g of glyceryl monostearate and 100g of fine white sugar. The glyceryl monostearate should be mixed evenly with the white sugar before adding it. After it is evenly dissolved, set the speed of the emulsifying shear machine to 5500rpm and emulsify and shear for 15 minutes. Then, mix it evenly with the remaining 1000g of raw soy milk and 500g of production water. Add 30g of soybean residue dietary fiber and emulsify and shear for 5 minutes.

[0073] High-pressure homogenization: The blended soy milk is subjected to high-pressure homogenization at a material temperature of 60℃ and a processing pressure of 45MPa, and the homogenization is performed twice.

[0074] Filling and sterilization: The homogenized soy milk is filled into PP bottles and then subjected to horizontal spray sterilization at a temperature of 121℃ for 20 minutes.

[0075] Cooling: After sterilization, shake the soy milk evenly and then spray it to cool it down to 40-45℃. Then transfer it to room temperature for storage.

[0076] Comparative Example 2

[0077] A processing method for a soy milk beverage differs from Comparative Example 1 in that: after grinding the soybeans, the filter is performed using 80-mesh, 120-mesh, and 150-mesh silk cloth filters; and in the ingredient mixing and dissolving step, 1.0g of xanthan gum is added and mixed to obtain a mixed ingredient solution. All other operations are the same as in Comparative Example 1.

[0078] The following describes the testing methods for the protein dissolution rate of soybean grinding, the total dietary fiber content in soy milk slurry, the particle size and microstructure of dietary fiber in nano-micro soybean residue, and the testing methods for the apparent viscosity and shelf-life suspension stability of thermally stable high-fiber soy milk:

[0079] 1. Protein dissolution rate after soybean grinding

[0080] The dry weight protein content of 100 kg of soybeans is tested. After calculating the total protein content, water is added and the soybeans are ground into a pulp. Then the original pulp protein content is tested. The original pulp protein content is divided by the total protein content, and the result is multiplied by 100% to obtain the protein dissolution rate after soybean grinding.

[0081] 2. Determination of total dietary fiber content and protein concentration in soy milk concentrate

[0082] The total dietary fiber content in the soy milk slurry of this invention was evaluated according to GB5009.88-2014 "National Food Safety Standard - Determination of Dietary Fiber in Food". The protein concentration in the soy milk slurry of this invention was determined according to the method in GB 5009.5-2016 "National Food Safety Standard - Determination of Protein in Food". 3. Particle size testing method for nano-micronized soybean residue dietary fiber.

[0083] Particle size was determined using a laser particle size analyzer. A nano-micronized soybean residue dietary fiber suspension was placed in an ultrasonic device with a power of 300W and an ultrasonic time of 5 minutes. After ultrasonication, a small amount of surfactant was added to the fiber solution and dispersed evenly. This was then added to the wet disperser of the particle size analyzer. Once the instrument's light-blocking level reached 5-10%, particle size analysis was performed. Each sample was tested in triplicate, and the average particle size data was taken, expressed as D50 particle size.

[0084] 4. Observation Methods for the Microscopic Morphology of Nano-sized Soybean Residue Dietary Fiber

[0085] The morphology of nano-sized soybean residue dietary fiber was observed using transmission electron microscopy (TEM). A dietary fiber solution with a mass concentration of 1 g / L was prepared, sonicated at 300 W for 5 min, and then 50 μL of the solution was placed on a copper grid. 10 μL of uranium acetate with a mass concentration of 20 g / L was added for staining for 2 min. Excess stain was absorbed with filter paper, and the solution was dried under an infrared lamp before being transferred to a TEM for observation of the cellulose morphology. The TEM voltage was 80 kV, and the magnification was 30,000x. The diameter of the microfibrils was measured using ImageJ image processing software.

[0086] 5. Thermal stability test of nano-micro soybean residue dietary fiber

[0087] The thermal stability of nano-sized soybean residue dietary fiber was tested using differential scanning calorimetry (DSC). 30 mg of soybean residue dietary fiber powder was placed in a high-pressure crucible, 100 μL of distilled water was added, the crucible was sealed, and the mixture was allowed to stand at room temperature for 12 hours to equilibrate. The crucible was then placed in the DSC, with an empty crucible used as a control for enthalpy change testing. The test conditions were: nitrogen as purge gas at a flow rate of 20 mL / min; initial temperature of 25 °C, heating rate of 5 °C / min, and final temperature of 140 °C. The enthalpy change temperature and enthalpy value of the sample during the heating process were recorded.

[0088] 6. Apparent viscosity test of high-fiber soy milk

[0089] The apparent viscosity of high-fiber soy milk was tested using a rotational viscometer. A 200 mL sample of soy milk was placed under the rotor of the rotational viscometer. Rotor #1 was selected, and the rotation speed was controlled at 6-60 rpm to test the apparent viscosity of the soy milk. The optimal reading on the meter was controlled within the range of 20-80. After the value stabilized, it was read and the apparent viscosity was calculated by referring to the viscosity coefficient table for that rotor. The formula is as follows:

[0090]

[0091] In the formula, η represents the apparent viscosity (cp); α represents the sample reading; and K represents the conversion factor corresponding to the rotor.

[0092] 7. Shelf suspension stability test of high-fiber soy milk

[0093] Take 30 mL of well-mixed soy milk sample and place it in a 50 mL sterilized stoppered graduated test tube. Add 0.02% sodium azide solution for sterilization. After irradiating with ultraviolet light for 60 min in a clean bench, place at room temperature for 30 days and observe the sedimentation of dietary fiber. Calculate the suspension stability of dietary fiber in high-fiber soy milk by the change in the sedimentation scale on the stoppered test tube, and express it as a stability index. The results are as follows:

[0094]

[0095] In the formula: T is the stability index; S1 represents the height of the soy milk in the stoppered test tube (cm); S2 represents the distance (cm) of dietary fiber sedimentation after the soy milk has been stored for 30 days.

[0096] The protein dissolution rate and dietary fiber content of the soy milk pulp in Comparative Examples 1-2 and Examples 1-4 are shown in Table 1; the particle size distribution of dietary fiber in nano-micro soybean residue is shown in Table 1. Figure 1 Micromorphology Figure 2 The apparent viscosity of high-fiber soy milk is shown in the figure. Figure 3The thermodynamic enthalpy change of nano-micro soybean residue dietary fiber is shown in Table 2; the experimental data of zeta potential and stability index of high-fiber soybean milk emulsion are shown in Table 3.

[0097] Table 1. Soybean protein dissolution rate and pulp fiber content in Comparative Examples 1-2 and Examples 1-4

[0098]

[0099] Table 2. Yield and enthalpy change of nano-micronized soybean residue dietary fiber in Comparative Examples 1-2 and Examples 1-4

[0100]

[0101] Table 3. Zeta potential and stability index of high-fiber soy milk emulsions in Comparative Examples 1-2 and Examples 1-4

[0102]

[0103] As shown in Table 1, the improved soybean grinding process increased the protein extraction rate to 94.22% and the total dietary fiber content of the raw pulp to 1.03g / 100g. Figure 1 and Figure 2 The data shows that Comparative Examples 1-2 are soybean residue dietary fibers without nano-micronization treatment. These fibers exhibit a blocky structure with D50 particle sizes of 80.89 μm and 77.94 μm, respectively. Examples 1-4 are soybean residue dietary fibers after nano-micronization treatment. These fibers exhibit a fibrous structure with a median particle size of 20-35 μm, and the diameter of the microfibers reaches the nanometer level. The nanofibers in Example 4 have the smallest size, with a D50 particle size of 20.85 μm. This indicates that using microwave-pressure heating combined with enzymatic degradation technology can effectively reduce the size of soybean residue dietary fibers after low-temperature ultrafine grinding and degrade blocky fibers into fibrous fibers. As shown in Table 2, the peak temperature of enthalpy change of unmodified soybean residue dietary fiber after heating is 72.31℃, and the enthalpy value is 9.24J / g. After modification, the peak temperature and enthalpy change of the dietary fiber are significantly increased, which indicates that the nano-micro modification treatment of soybean residue dietary fiber using the present invention can improve the thermodynamic stability of soybean residue dietary fiber.

[0104] Furthermore, the nano-sized soybean residue dietary fiber is added to the soy milk, and after blending, emulsification, homogenization, and sterilization, soy milk is produced. Figure 3Comparing the apparent viscosity of soy milk without added dietary fiber with that of soy milk with added nano-sized dietary fiber, it was found that the apparent viscosity of soy milk without added dietary fiber was lower, with Comparative Examples 1 and 2 showing apparent viscosities of 19 cp and 36 cp, respectively. However, the apparent viscosity of soy milk with added nano-sized dietary fiber (Examples 1-4) was significantly increased, with Example 4 showing the highest apparent viscosity at approximately 285 cp. This indicates that adding nano-sized soybean pulp dietary fiber can increase the apparent viscosity of soy milk, giving it a smooth, milkshake-like natural texture.

[0105] Finally, the inventors tested the zeta potential and stability index of the high-fiber soy milk emulsion, and the test results are shown in Table 3. Table 3 shows that Comparative Example 1 added untreated soybean residue dietary fiber, which did not exhibit ideal stabilization in the soy milk. Zeta potential measurement revealed a potential of -10.3V and a stability index of 62.3%, indicating significant stratification of the dietary fiber in the soy milk system. Examples 1-4 show that the high-fiber soy milk with added nano-micro soybean residue dietary fiber exhibited a significant decrease in zeta potential, and the dispersion and stabilization of the dietary fiber in the soy milk were significantly improved. Among them, the high-fiber soy milk emulsion in Example 4 had the lowest zeta potential of -28.1V, and the stability index of the soy milk was significantly improved, reaching 94.7%. Soybean residue dietary fiber showed good suspension stability in soy milk, demonstrating that nano-micro soybean residue dietary fiber plays a crucial role in improving the suspension stability of high-fiber soy milk.

[0106] Furthermore, compared to Comparative Example 1, which only used glyceryl monostearate for formulation, this invention uses glyceryl monostearate and xanthan gum together to formulate high-fiber soymilk. The negatively charged anionic polysaccharide xanthan gum improves the suspension stability of high-fiber soymilk after sterilization by increasing the spatial extension specific surface area of ​​dietary fiber and enhancing the electrostatic interaction force of the dietary fiber system. This overcomes the problems of unstable dispersion and easy sedimentation of dietary fiber powder in soymilk beverages, thus significantly improving the apparent viscosity and stability index of the high-fiber soymilk of this invention. Simultaneously, compared to Comparative Example 2, which also added glyceryl monostearate and xanthan gum as formulation additives, the filamentous structure of the nano-microscopic soybean residue dietary fiber has greater spatial extension, effectively reducing the phenomenon of fiber agglomeration and sedimentation caused by hydrogen bonding association during thermal processing due to the exposure of a large number of hydrophilic groups caused by the breakage and size reduction of dietary fiber particles. Therefore, the apparent viscosity and stability index of the high-fiber soymilk of this invention are also superior to those of Comparative Example 2.

[0107] In summary, this invention achieves microfibrillation of dietary fiber by using microwave-pressure heating pretreatment to assist enzymatic hydrolysis, thereby degrading the particle size of dietary fiber and altering its morphology to form microfibrils with a length of micrometers (10-30 μm) and a diameter of nanometers (10-40 nm). These microfibrils exhibit strong thermal stability and significant spatial extensibility, effectively reducing hydrogen bonding and fiber aggregation during thermal processing caused by particle breakage and size reduction. This invention achieves full utilization of soybeans by controlling the grinding and filtration processes and by adding insoluble polysaccharides from processing byproducts to increase the dietary fiber content of soy milk. Furthermore, the use of simple, small-volume food additives (glyceryl monostearate and xanthan gum) mitigates fiber aggregation under thermodynamically unstable conditions through electrostatic repulsion and surface activity, meeting modern consumers' demand for green and clean foods. In addition, testing revealed that the high-fiber soy milk provided by this invention maintains a stability index above 90% after 60 days of storage at room temperature (25°C), with moderate viscosity and a smooth texture.

[0108] It should be noted that the processing method provided by this invention is also applicable to processing other vegetable or fruit residues containing dietary fiber.

[0109] It should be noted that although the above embodiments have been described herein, this does not limit the scope of patent protection of the present invention. Therefore, any changes and modifications made to the embodiments described herein based on the innovative concept of the present invention, or equivalent structural or procedural transformations made using the content of the present invention's specification and drawings, directly or indirectly applying the above technical solutions to other related technical fields, are all included within the scope of patent protection of the present invention.

Claims

1. A processing method for suspension-stabilized high-fiber soy milk with full utilization of dietary fiber, characterized in that, Includes the following steps: Soaking and rehydration: Soak peeled soybeans in food processing water overnight to obtain soaked peeled soybeans; Hot grinding: The soaked and peeled soybeans are added to processing water at 80-85℃ at a mass-to-volume ratio of 1:5-6, and baking soda is added. The mixture is then graded, ground, and filtered. The filtration process includes filtering the graded and ground soybean milk using filters of different mesh sizes. The filtration process uses a combination of 60-mesh, 100-mesh, and 150-mesh filters to obtain raw soy milk and soybean residue. Soybean residue nano-micro processing: After washing and filtering the soybean residue, a suspension with a mass concentration of 10-20 g / L is prepared and subjected to microwave-pressure heating modification treatment to obtain a modified soybean residue suspension. The modified soybean residue suspension was subjected to enzymatic hydrolysis, solid-liquid separation, and freeze-drying to obtain nano-micro soybean residue dietary fiber. The microwave-pressure heating modification treatment conditions were as follows: microwave reactor pressure heating temperature of 125-130℃, microwave power of 800-1000W, and reaction time of 60 min; the enzyme used for enzymatic hydrolysis was cellulase, with a dosage of 0.3-0.5%, a reaction pH of 4.5-5.0, a temperature of 50-55℃, and a reaction time of 12-18 h. Preparation: Adjust the protein concentration of the original pulp to 4.0g / 100g with water, add glyceryl monostearate, xanthan gum, and white sugar, set the speed to 8000-8500rpm, and perform the first emulsification and shearing for 10-20min. Add the nano-micro soybean residue dietary fiber, and perform the second emulsification and shearing for 5-10min at the same speed to obtain the prepared soy milk. Defoaming and high-pressure homogenization: The prepared soy milk is subjected to defoaming and high-pressure homogenization to obtain high-fiber soy milk crude product; The high-fiber soy milk crude product is filled, sterilized, and cooled to obtain the dietary fiber-stable high-fiber soy milk.

2. The high-fiber soy milk processing method according to claim 1, characterized in that, In the preparation step, the amount of glyceryl monostearate added is 0.1-0.15% of the total mass percentage of the high-fiber soy milk, the amount of xanthan gum is 0.03-0.05%, and the amount of nano-micronized soybean residue dietary fiber is 1.5-2.0%.

3. The high-fiber soy milk processing method according to claim 1, characterized in that, In the hot grinding step, the amount of baking soda used is 0.05-0.08% based on the total mass percentage of the soaked, peeled soybeans and the aqueous solution; the graded grinding includes: First-stage grinding: 6000-8000 rpm, grinding time: 10 minutes; and Two-stage grinding, with a speed of 8000-12000 rpm and a grinding time of 15 minutes.

4. The high-fiber soy milk processing method according to claim 1, characterized in that, Cooling is achieved through spray cooling, with the tank temperature controlled at 45±3℃.

5. A suspension-stabilized high-fiber soy milk with full utilization of dietary fiber, characterized in that, It is prepared by the processing method according to any one of claims 1-4.

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