Method for preparing high-nutrition type bean flour by combining ion regulation with spray drying

Abstract

The invention discloses a method for preparing high-nutrition bean flour through ion regulation combined with spray drying, and belongs to the technical field of bean product processing. The method comprises the following steps: spraying soybeans, drying and peeling; grinding into thick liquid; carrying out enzyme deactivation and inactivation; centrifugally discharging slag; sterilizing and deodorizing; performing composite enzymolysis; adjusting metal ions; sterilizing and concentrating; performing spray drying; the high-nutrition type bean flour is obtained. According to the method, soybeans are rapidly sprayed, drying and peeling of the soybeans are facilitated, a compound enzyme enzymolysis technology is adopted, the soybean enzymolysis degree is improved, more binding sites are exposed, a chelation reaction with ferric salt can be carried out to obtain a novel iron supplement agent polypeptide iron chelate, the bioavailability is high, meanwhile, a calcium supplement is supplemented, calcium ions can be combined with carboxyl of soybean peptide, and the calcium supplement effect is good. Meanwhile, the solubility and the heat stability are improved, and the limitations that the calcium content and the iron content of a traditional bean beverage are low and the bean beverage inhibits calcium and iron absorption are broken through.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of soybean product processing, and particularly relates to a method for preparing high-nutrition soybean powder by ion regulation combined with spray drying. BACKGROUND

[0002] Soybean is an important plant protein resource, and its protein content is as high as 30-40%, the fat content is 15-20%, and the carbohydrate content is 20-30%. In addition, it is also rich in minerals, vitamins, dietary fiber and various bioactive substances, and is an important source of human nutrition. Because the soybean protein content is high and does not contain cholesterol, it is widely used as an ingredient for various types of nutritional food or directly processed into high-protein nutritional food, and is particularly suitable for people with lactose intolerance as a nutritional supplement. With the improvement of the national living standard, consumers' requirements for the nutritional value and taste of soybean beverage are gradually increasing.

[0003] For example, the patent application document with the publication number CN117752047A discloses a high-nutrition high-calcium multi-element soybean powder and a preparation method thereof in the technical field of soybean powder processing, which comprises the following components: modified composite fermented soybean powder, composite modified starch, sweet potato leaf extract, oat powder, nut powder, fruit juice powder, calcium carbonate, soybean lecithin and seasoning. The application proposes a method of mixing and fermenting the composite soybean milk by hydrolysis, enzymolysis and beta-cyclodextrin glycosylation modification, and mixing with activated probiotics, to realize the technical effects of improving the nutrient content of soybean powder and the absorption of soybean powder by the human body. The composite modified starch obtained by hydrolysis of beta-amylase, oxidation of hexose oxidase, addition of konjac glucomannan and L-arginine improves the stability of the soybean powder and prolongs its shelf life. The addition of sweet potato leaf extract and oat powder further improves the nutritional value of the soybean powder, and helps to remove free radicals in the body, enhance immunity, antioxidant, anti-inflammatory and hypoglycemic functions.

[0004] For another example, the patent document with the publication number CN113907268B discloses a method for preparing low-bitterness soybean peptide powder from soybean hydrolysate, which comprises the following steps: soybean pretreatment, Alcalase 2.4L protease enzymolysis, oil preparation, sucrose enzyme hydrolysis, Maillard reaction, and preparation of soybean peptide powder. The method can prepare soybean peptide powder with low bitterness and high nutrition. The method not only reduces the bitterness of the hydrolysate, but also increases the value of by-products, reduces resource waste, protects the environment, and is suitable for actual continuous production. The substrate for the Maillard reaction comes from the hydrolysate system, without the need for additional addition of reducing sugar, which is low in production cost, simple and convenient to operate, high in efficiency, and suitable for actual continuous production. Moreover, the soybean peptide powder prepared by the Maillard reaction has high nutritional value. The method of preparing low-bitterness high-nutrition freeze-dried soybean peptide powder by the Maillard reaction lays a foundation for the popularization of biological dissociation technology and the application of hydrolysate in the food industry.

[0005] However, calcium iron chelation in soybean powder is a key factor limiting nutrition, for example, the calcium content in soybean powder is low, only 1 / 5 of milk, and after the soybean powder is brewed, the main calcium component exists in the form of calcium oxalate or calcium phytate, which is difficult to be absorbed by the intestinal tract, and the calcium absorption rate is only about 15-25%. The iron in the soybean powder product mainly exists in the form of Fe 3+ After brewing into soy milk, iron phytate precipitates, and the absorption rate is only 3-7% (about 15-35% of animal hematin iron); at the same time, due to the chelation of calcium, iron ions and soybean components (especially phytic acid and protein), the drinking of soybean beverage directly affects the absorption of calcium, iron ions and other ions by the human body.

[0006] With the rapid growth of demand for soybean powder in China, nutrition fortification has become a key factor in the quality of soybean powder. Consumers' awareness of health and nutrition is constantly improving, and the demand for functional food ingredients is increasing, which stimulates the demand for soybean powder industry. With the improvement of consumers' health awareness, the demand for nutritional soybean powder is also growing, especially in the context of the popularization of healthy diet concepts, the market demand for healthy drinks such as soybean milk powder is expanding. Therefore, how to solve the low content of calcium and iron in soybean beverage and the inhibition of calcium and iron absorption by soybean beverage has become a problem to be solved. SUMMARY

[0007] In view of the deficiencies of the prior art, the present application provides a method for preparing high-nutrition soybean powder by ion regulation combined with spray drying, which aims to solve the problems of low calcium and iron content in traditional soybean beverage and the inhibition of calcium and iron absorption by soybean beverage.

[0008] To achieve the above-mentioned purpose, the present application adopts the following technical solutions:

[0009] A method for preparing high-nutrition soybean powder by ion regulation combined with spray drying, comprising the following steps:

[0010] S1: soybean pretreatment: the process of soybean pretreatment comprises spraying the soybean quickly, and then drying and peeling the soybean subjected to the quick spraying;

[0011] S2: grinding: adding hot water and sodium bicarbonate aqueous solution to the pretreated soybean in step S1 to grind, to obtain a slurry with a pH value of 7.0-7.4;

[0012] S3: enzyme inactivation: adding hot water to the obtained slurry in S2, and passing steam to inactivate the enzyme, to obtain enzyme-inactivated slurry;

[0013] S4: centrifugal dewatering: putting the enzyme-inactivated slurry obtained in step S3 into a centrifugal separator, and centrifugal dewatering to obtain slurry for standby;

[0014] S5: sterilization and deodorization: the slurry obtained in step S4 is heated for sterilization and deodorization, and after the sterilization and deodorization is completed, the slurry is cooled;

[0015] S6: enzymolysis: the slurry obtained in step S5 after the sterilization and deodorization is placed in a water bath, and alkaline protease and papain are added for heating and enzymolysis, to obtain the slurry after the enzymolysis;

[0016] S7: metal ion solution adjustment: FeCl2 solution and CaCl2 solution are added to the slurry after the enzymolysis in step S6 for stirring, to obtain the ion-adjusted slurry;

[0017] S8: sterilization and concentration: the ion-adjusted slurry obtained in step S7 is subjected to high-temperature sterilization and then heated for concentration, to obtain the concentrated material;

[0018] S9: spray drying: the concentrated material obtained in step S8 is subjected to spray drying, to obtain the high-nutrition soybean powder.

[0019] Preferably, in step S1, the soybeans are quickly sprayed with hot water, the temperature of the hot water is 40-60℃, and the spraying time is 10-20s.

[0020] Preferably, in step S2, the mass ratio of the soybeans to the hot water is 1:(9-10), the temperature of the hot water is 80-85℃, and the concentration of the sodium bicarbonate aqueous solution is 2.0-3.5wt%.

[0021] Preferably, in step S3, the temperature of the added hot water is 80℃.

[0022] Preferably, in step S4, the centrifuge speed for the centrifugal dewatering is 3000-5000rpm, and the separation time is 3-5min.

[0023] Preferably, in step S5, the heating temperature for the sterilization and deodorization is 125℃, the duration of the deodorization is 5s, and after the sterilization and deodorization is completed, the slurry is cooled to 50℃.

[0024] Preferably, in step S6, the enzymolysis temperature is 50-55℃, the enzymolysis time is 20-25min, and the mass fraction of the added alkaline protease and papain is both 5wt%.

[0025] Preferably, in step S7, the mass fraction of the added FeCl2 in the slurry after the enzymolysis is 0.5-1.0wt%, and the mass fraction of the added CaCl2 is 3.0-5.0wt%.

[0026] Preferably, in step S8, the high-temperature sterilization temperature is 90℃, and the high-temperature sterilization time is 2min.

[0027] Preferably, in step S9, the inlet air temperature of the spray drying is 160-175 DEG C, and the exhaust air temperature is 70-80 DEG C.

[0028] Advantages:

[0029] Compared with the prior art, the present application can achieve at least the following technical effects:

[0030] 1、The present application obtains a novel iron supplement polypeptide iron chelate by chelating reaction of soybean protein hydrolysis and iron salt, which has high bioavailability, little odor, and also has antioxidant activity, immune activity, antibacterial activity and other biological activities.

[0031] 2、The present application adds appropriate amount of alkaline protease and papain to decompose proteins and other components in soybeans.

[0032] 3、The present application adds appropriate amount of alkaline protease and papain to decompose proteins and other components in soybeans, which not only can improve the flavor, but also can help to improve the digestibility and active site of proteins, providing a prerequisite for subsequent metal chelation.

[0033] 4、The present application uses hot water rapid spraying method for soybean pretreatment, which improves the moisture content of soybeans, helps to quickly carry out the drying and peeling process, reduces the loss of nutritional components in the peeling process, and improves the yield.

[0034] 5. The present invention optimizes the solid-liquid ratio during the refining process, and the mass ratio of soybeans to hot water is controlled at 1:(9-10), which can ensure a protein concentration of 3.2-3.5g / 100mL, form a stable emulsified system, and prevent stratification.

[0035] 6. The present invention adds sodium bicarbonate solution during the refining process. Sodium bicarbonate is an alkaline substance that helps reduce unpleasant odors in soybeans, such as beany smell.

[0036] 7. The present invention optimizes the high-temperature sterilization process. 90°C for 2 minutes can not only effectively destroy the cell structure of pathogenic bacteria in soy milk, making them inactive or dead; it can also kill a large number of yeasts, molds and most heat-sensitive spoilage bacteria that cause food spoilage, delaying the spoilage process of food and retaining the original fresh flavor of soy milk to the greatest extent. It also has a relatively mild effect on protein denaturation and colloidal structure, helping to maintain the taste, viscosity and texture of the food.

[0037] 8. This invention optimizes spray drying parameters, spray drying soy milk at 160-175°C inlet air and 70-80°C exhaust air, achieving efficient dehydration, microbial inactivation, and anti-nutritional factor passivation while maximally protecting protein functionality and heat-sensitive nutrients. Balancing drying efficiency and quality protection within a very short heating time, the resulting product is high-quality soy flour with excellent solubility, natural color and flavor, high nutrient retention, and a long shelf life. Controlling the exhaust air temperature (70-80°C) avoids excessive protein denaturation and Maillard reaction, improving the soy flour's mixing experience and nutritional value. DETAILED DESCRIPTION

[0038] The present invention is further described below with reference to specific implementation examples. In the description of the present invention, the terms "one embodiment," "some embodiments," "specific embodiments," etc., mean that the specific features, structures, materials, or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In the present invention, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described may be combined in any appropriate manner in any one or more embodiments or examples.

[0039] The present invention provides a method for preparing high-nutrition soybean powder by ion adjustment combined with spray drying, comprising the following steps:

[0040] S1: Soybean pretreatment: The pretreatment process includes rapid spraying of the soybeans, followed by drying and peeling of the rapidly sprayed soybeans;

[0041] The specific process is:

[0042] S1-1: Soybeans are screened, de-stoned, and cleaned to remove moldy, damaged, and impurities grains;

[0043] S1-2: Using a continuous spray blanching machine or a steam blanching tunnel, the soybeans are continuously passed through one or more spray chambers on a conveying mesh belt (such as a stainless steel mesh belt). Warm water is sprayed from above (and sometimes also from the side) onto the surface of the soybeans through pressure nozzles to form a uniform water curtain or dense water mist;

[0044] S1-3: Using a fluidized bed dryer, the soybeans are brought into a fluidized state using hot air, which has high heat and mass transfer efficiency, fast drying speed, and short drying time. In a short time, the moisture content of the soybeans can be reduced to the ideal range of 9.5%-10.5% for peeling. At this moisture content, the binding force between the endosperm (cotyledon) and the seed coat inside the soybean kernel is weakest, while the bean skin itself becomes dry and brittle, easily breaking and peeling off, while the cotyledon remains somewhat tough and is not easily broken.

[0045] In the above steps, the soybeans are pretreated using hot water rapid spraying method to increase the moisture content of the soybeans, which helps to quickly perform the drying and peeling process and reduces the loss of nutritional components in the soybeans during the peeling process, thereby improving the yield.

[0046] S2: Milling: The pretreated soybeans from step S1 are added to hot water and a sodium bicarbonate aqueous solution for milling to obtain a slurry with a pH value of 7.0-7.4;

[0047] The specific process is as follows:

[0048] S2-1: Hot water and a sodium bicarbonate solution are added to the soybeans, and the mixing ratio of the soybeans to the hot water is controlled through a quantitative feeder (such as a screw feeder), a flow meter, or a proportional mixer.

[0049] S2-2: A hammer mill or a toothed disc mill is used to preliminarily crush the whole grains or soybean pieces into coarse slurry, which reduces the burden of fine grinding and improves the overall efficiency.

[0050] S2-3: A colloidal mill is used to further grind the particles in the coarse slurry to the micron level (10-50 μm), which completely destroys the cell wall and releases protein bodies, oil, and other substances to form a stable emulsion.

[0051] The addition of sodium bicarbonate increases the pH to 7.0-7.4, which makes the protein negatively charged, increases the intermolecular repulsive force, and improves the solubility.

[0052] S3: Enzyme inactivation: Hot water is added to the slurry obtained in S2 and steam is introduced for enzyme inactivation to obtain an enzyme-inactivated slurry;

[0053] After grinding, a certain amount of endogenous enzymes remains in the soybean milk, mainly including lipoxidase,

[0054] Lipoxygenase is a naturally occurring enzyme in soybean, which, when the soybean tissue is damaged (such as soaking, grinding), contacts with polyunsaturated fatty acids (such as linoleic acid, linolenic acid) and oxygen in the cell, generates unstable hydroperoxide, and destroys essential fatty acids (linoleic acid, linolenic acid) and fat-soluble vitamins (such as vitamin E)

[0055] Since lipoxygenase is not heat-resistant, the present application realizes instant temperature rise of soybean milk by directly injecting hot water and high-temperature steam, completely passivates endogenous enzymes such as lipoxygenase, eliminates beany flavor, and kills microorganisms.

[0056] S4: Centrifugal dewatering: the enzyme-inactivated slurry obtained in step S3 is pumped into a decanter centrifuge, and dewatering is performed by centrifugation, to obtain slurry for standby;

[0057] In this step, the solid soybean dregs in the soybean milk are separated from the liquid soybean milk by centrifugal force, and the process is as follows:

[0058] S4-1: The raw soybean milk (containing soybean dregs) after grinding is pumped into the rotating drum of a high-speed centrifuge;

[0059] S4-2: Under the action of strong centrifugal force, the soybean dregs particles with relatively large density rapidly settle down to the drum wall or the gap between the discs and are gathered;

[0060] S4-3: The clarified soybean milk flows upward at the center of the drum or inside the discs and is collected and discharged; the gathered soybean dregs (wet dregs) are periodically or continuously discharged from the dreg discharge port.

[0061] S5: Sterilization and deodorization: the slurry obtained in step S4 is heated for sterilization and deodorization treatment and then cooled;

[0062] In the present application, ultra-high temperature instant sterilization (UHT-Ultra High Temperature Treatment) is adopted, direct steam injection UHT, indirect plate UHT or tube UHT is used, and a sterile filling system is used, so that the soybean milk is instantaneously heated to high temperature and stays for a short time, thereby killing pathogenic bacteria (such as Salmonella, Escherichia coli), spoilage bacteria and heat-resistant spores in the soybean milk, and ensuring food safety.

[0063] S6: Enzymolysis: the slurry obtained after sterilization and deodorization in step S5 is placed in a water bath, and alkaline protease and papain are added for heating and enzymolysis, to obtain the slurry after enzymolysis;

[0064] Although soybean protein is of high quality, it has a complex structure and contains some factors (such as trypsin inhibitor) that hinder digestion. Enzymolysis can decompose macromolecular proteins into small molecular peptides and amino acids.

[0065] Enzymatic hydrolysis can produce peptides with specific biological activities (such as antioxidant peptides, antihypertensive peptides ACE inhibitory peptides, immunomodulatory peptides, etc.), endowing soy milk with additional health functional properties.

[0066] The present application decomposes the proteins and other components in soybeans by adding an appropriate amount of alkaline protease and papain. Among them, alkaline protease is good at cutting the carboxyl end peptide bond of hydrophobic amino acids (such as phenylalanine, tyrosine, tryptophan), and has high hydrolysis efficiency of soybean protein; papain belongs to sulfhydryl protease, and has wide specificity, and can cut the peptide bond of various amino acids (especially arginine, lysine, phenylalanine). It has the ability to remove bitterness and can further hydrolyze the bitter peptides produced by alkaline protease.

[0067] The pre-decomposition of macromolecular proteins in soy milk into small molecular peptides and amino acids improves the value and application range of soy milk (soy protein), not only improves the flavor, but also helps to improve the digestibility and active site of protein, and provides a prerequisite for subsequent metal chelation.

[0068] S7: Metal ion solution adjustment: adding FeCl2 solution and CaCl2 solution to the slurry subjected to enzymatic hydrolysis in step S6 and stirring to obtain an ion adjusted slurry;

[0069] The core purpose of this step is mineral fortification (iron, calcium) and ion environment regulation, and the final "ion adjusted slurry" has more balanced nutritional composition and potential functional property optimization. Among them, the iron content of soy milk itself is low, the addition of FeCl2 can significantly improve the content of bioavailable divalent iron (Fe 2+ ), and chelate with soybean protein after hydrolysis to form polypeptide iron chelates with high bioavailability, little off-flavor, low price, and biological activities such as antioxidant activity, immune activity, and antibacterial activity. At the same time, calcium is supplemented, Ca 2+ can be combined with the carboxyl group (-COOH) of soybean peptide to improve solubility and thermal stability. At the same time, calcium combines with carbon dioxide in the air to form part of calcium carbonate, which can improve the flavor and digestibility of soy powder, make its taste more delicate, increase its digestibility, maintain the acid-base balance of soy powder, ensure its quality and taste, ensure the subsequent volume expansion of soy powder particles, enhance the stability, and prolong the shelf life.

[0070] S8: sterilization and concentration: sterilizing the ion adjusted slurry obtained in step S7 at high temperature, then heating and concentrating to obtain a concentrated material;

[0071] The sterilization and concentration of soybean milk is a key step of combining sterilization process with concentration process, mainly used for producing concentrated soybean milk (liquid) or providing pretreated slurry for subsequent spray drying to make soybean milk powder. The core goal is to significantly improve the concentration of soybean milk solids while ensuring food safety and extending shelf life, and to improve product economy and application convenience.

[0072] S9: Spray drying: the concentrated material obtained in step S8 is subjected to spray drying to obtain high-nutrition soybean powder.

[0073] The process is as follows: air is converted into hot air by a heater, enters a hot air distributor at the top of a drying chamber of a spray drying device, then uniformly enters the drying chamber and rotates in a spiral shape, while the material (soybean milk) is sent to a centrifugal atomizer at the top of the drying chamber, so that the material liquid is atomized into extremely small atomized droplets, the material liquid and hot air are in parallel contact, and the water is rapidly evaporated to be dried into a finished product in a very short time.

[0074] In this step, air flow type spray drying is adopted, and the wet material (soybean milk) and the heated natural air enter the dryer at the same time through the conveyor, and the two are fully mixed, so that the evaporation and drying purpose is achieved in a very short time due to the large heat exchange area. The finished product after drying is discharged from the cyclone separator, and a small part of the flying powder is recovered by the cyclone dust collector or the bag dust collector

[0075] Further, in step S1, hot water is used for rapid spraying of soybeans, the temperature of the hot water is 40-60℃, and the spraying time is 10-20s;

[0076] The main component of the seed coat is hemicellulose (glass transition temperature about 35℃), and 40℃ is just above the glass transition starting temperature, so that the seed coat is converted from glassy state to high-elastic state, and the water penetration rate can be increased by 3 times at this time; and 60℃ is lower than the critical point of protein denaturation, and the spraying time must be controlled to be ≤20s to prevent surface protein aggregation.

[0077] Further, in step S2, the mass ratio of soybeans to hot water is 1:(9-10), the temperature of the hot water is 80-85℃, and the concentration of the sodium bicarbonate aqueous solution is 2.0-3.5wt%.

[0078] The basis for the solid-liquid ratio of 1:9-10 is that a ratio lower than 1:9 will result in too high protein concentration (>3.8g / 100mL), and shear heat accumulation during grinding will cause protein denaturation; and a ratio higher than 1:10 will result in insufficient solids (<8.2%), and the subsequent concentration energy consumption will increase by 35%. The mass ratio of soybeans to hot water of 1:(9-10) can ensure the protein concentration of 3.2-3.5g / 100mL, form a stable emulsion system, and prevent delamination.

[0079] The temperature of the hot water is controlled at 80-85℃, which improves the efficiency of breaking the cell wall and the protein dissolution rate.

[0080] Further, in step S3, the temperature of the added hot water is 80℃.

[0081] Based on the thermal stability data of the target enzyme, a temperature and time combination is selected that can ensure complete inactivation (enzyme activity residue <1%) and maximize the retention of product quality (nutrition, flavor, color). For protease and amylase in soy milk, the present application selects 80℃ hot water heating and maintains or adjusts the enzyme inactivation temperature by steam.

[0082] Further, in step S4, the centrifuge speed of the centrifuge for removing residues is 3000-5000 rpm, and the separation time is 3-5 min.

[0083] Through the above settings, it can be ensured that the soybean residue particles with a particle size of ≥20μm (accounting for 85% of the total amount) are efficiently settled, avoiding the turbidity of the slurry caused by the escape of fine particles, and capturing 5-10μm fine residue particles (calcium phytate complex), reducing the residual anti-nutritional factors; the centrifuge speed needs to be controlled within 5000 rpm to prevent high shear force from damaging the protein micelle structure.

[0084] Further, in step S5, the heating temperature for sterilization and deodorization is 125℃, the duration of sterilization and deodorization is 5s, and after sterilization and deodorization, it is cooled to 50℃.

[0085] The purpose of 125℃ ultra-high temperature instantaneous (UHT) treatment is: the D value of microorganisms decreases sharply at 125℃, such as heat-resistant spores D125=1.2s (D121=12s), 5s can achieve 12D sterilization, and the killing rate of Bacillus subtilis is >4D. At the same time, since the high-temperature inactivation time is controlled within 5s, the retention rate of vitamin B1 is increased to 92%, and the loss rate of isoflavones is reduced to 7%.

[0086] The purpose of precise control of cooling to 50℃ is: 50℃ is the critical point of Maillard reaction (<50℃ reaction rate decreases by 90%), which prevents residual heat from causing browning, Fe 2+ The oxidation rate is lowest at 50-60℃ (0.05% / min), which is 16 times lower than the oxidation rate at 80℃ environment;

[0087] At the same time, the optimum temperature for papain is 50-55℃, and the cooling endpoint is the starting temperature of the subsequent enzyme hydrolysis process.

[0088] Further, in step S6, the temperature for enzyme hydrolysis is 50-55℃, the enzyme hydrolysis time is 20-25 min, and the mass fraction of the added alkaline protease and papain is both 5wt%.

[0089] The optimal temperature of the alkaline protease is 50-60℃ (the enzyme activity is ≥95% at 55℃), and it specifically cuts hydrophobic amino acids (phenylalanine and tyrosine) to expose iron chelation sites and generate Fe 2+ chelate peptide fragments. The optimal temperature is 55-65℃ (90% of the enzyme activity is retained at 55℃), and it efficiently hydrolyzes the bitter peptides generated by the alkaline protease.

[0090] The enzymatic hydrolysis temperature is 50-55℃, and the total activity of the two enzymes can reach the maximum value.

[0091] During the enzymatic hydrolysis, the first 0-10 min is the rapid hydrolysis period, during which the macromolecular proteins are depolymerized into polypeptides. The next 10-20 min is the site exposure period, during which the iron / calcium chelation active sites are generated. The last 20-25 min is the bitter taste elimination period, during which the bitter peptides are degraded by the papain.

[0092] If the enzymatic hydrolysis time exceeds 30 min, the excessive release of amino acids will cause the bitter taste to rise again and the chelation rate to decrease. Therefore, the enzymatic hydrolysis time should be controlled within 30 min.

[0093] Further, in step S7, the mass fraction of FeCl2 added to the enzymatic hydrolysis slurry is 0.5-1.0wt%, and the mass fraction of CaCl2 added is 3.0-5.0wt%.

[0094] The mass fraction of FeCl2 is controlled at 0.5-1.0wt%. When the mass fraction of FeCl2 is 0.5wt%, it can meet the daily iron requirement of 18% (based on the daily intake of 20g of soybean powder). When the mass fraction of FeCl2 reaches 1.0wt%, the iron content of the final product reaches 35mg / 100g, which exceeds that of animal liver (30mg / 100g). When the mass fraction of FeCl2 exceeds 1.0wt%, it will exceed the chelation capacity of the peptide (Fe 2+ The free Fe 2+ The oxidation rate increases.

[0095] Further, in step S8, the temperature for high-temperature sterilization is 90℃, and the time for high-temperature sterilization is 2min.

[0096] There may still be pathogens such as Salmonella and Listeria in the ion-adjusted soybean milk. 90℃ for 2min can effectively damage the cell structure of these pathogens (such as protein denaturation, enzyme inactivation, and cell membrane damage), making them lose activity or die. At the same time, it can kill a large number of yeasts, molds, and most heat-sensitive spoilage bacteria that cause food spoilage and deterioration, delaying the spoilage and deterioration process of food and significantly prolonging the shelf life.

[0097] In addition, compared with higher temperature (such as UHT above 135℃) or longer time of heat treatment, it can maximize the retention of the original fresh flavor of soy milk, and has a relatively mild effect on protein denaturation and colloid structure, which helps to maintain the mouthfeel, viscosity and texture of the food.

[0098] The residual enzymes (such as peroxidase, lipase, pectinase, etc.) in soy milk can catalyze chemical reactions, causing problems such as off-flavor, discoloration, poor texture, and nutrient loss during storage. The high temperature of 0℃ / 2min can effectively passivate or inactivate these endogenous enzymes, maintaining the quality stability of the food.

[0099] Further, in step S9, the inlet air temperature of spray drying is 160-175℃, and the exhaust air temperature is 70-80℃.

[0100] The high-temperature inlet air (160-175℃) provides a large amount of heat energy, causing the surface water of the atomized soy milk droplets (diameter about 50-100μm) to evaporate instantaneously, and the internal water to migrate to the surface rapidly, thereby converting the soy milk from liquid to dry powder (moisture content ≤5%) in a very short time (a few seconds to tens of seconds);

[0101] At the same time, high temperature can effectively kill the residual bacteria, yeast and mold (including heat-resistant spores) in soy milk, significantly reduce the microbial load, prolong the shelf life of soy powder, and meet the food safety standards. Soybeans naturally contain antinutritional factors and enzymes such as trypsin inhibitors and lipoxidase. High temperature above 160℃ can quickly inactivate these substances, improve the digestibility and absorption rate of soy powder, and prevent the generation of "beany flavor" caused by oil oxidation during storage.

[0102] Controlling the exhaust air temperature (70-80℃) ensures that the soy powder is not overheated, avoids the severe denaturation and aggregation of soy protein, and maintains its key functions such as solubility, emulsification and gelation, which is the basis for the smooth taste and non-caking of the rehydrated soy powder.

[0103] In addition, the exhaust air temperature of 70-80℃ ensures that the powder is not excessively dried or heat denatured, and the protein particles maintain a loose and porous structure, optimizing the solubility and brewing properties of the product.

[0104] The use of 160-175℃ inlet air and 70-80℃ exhaust air for spray drying of soy milk aims to achieve efficient dehydration, microbial inactivation, and antinutritional factor passivation while maximizing the protection of protein function and heat-sensitive nutrients. Its core advantage lies in balancing drying efficiency and quality protection in a very short heating time, resulting in high-quality soy powder with good solubility, natural color and flavor, high nutrient retention rate, and long shelf life. Precise control of the exhaust air temperature (70-80℃) is the key to avoiding excessive protein denaturation and Maillard reaction, which directly determines the brewing experience and nutritional value of the soy powder.

[0105] Example 1:

[0106] The steps and related parameters prepared in this example are as follows:

[0107] S1: Pretreatment of soybeans: The soybeans were quickly sprayed with hot water at a temperature of 40°C for 10s. After spraying, drying was performed at a temperature of 95°C, and the discharge temperature was 50°C;

[0108] A continuous spray scalding machine or a steam scalding tunnel was used, and the soybeans were continuously passed through one or more spray chambers on a conveying mesh belt (such as a stainless steel mesh belt). Hot water at a temperature of 40°C was sprayed from above (sometimes also from the side) to the surface of the soybeans through pressure nozzles to form a uniform water curtain or dense water mist, and the spraying time was controlled at 10s.

[0109] S2: Refining: The pretreated soybeans were added to hot water and sodium bicarbonate aqueous solution for refining, with a mass ratio of soybeans to hot water of 1:9, a hot water temperature of 80°C, and a sodium bicarbonate aqueous solution concentration of 2.5wt%, to obtain a slurry with a pH value of 7.0-7.4;

[0110] S3: Enzyme inactivation: The refined slurry was added to 80°C hot water and steam was introduced for enzyme inactivation;

[0111] S4: Centrifugal dewatering: The enzyme-inactivated slurry was fed into a centrifugal separator for centrifugal dewatering, and the slurry was prepared for use;

[0112] S5: Sterilization and deodorization: The slurry was heated to 125°C for 5s for sterilization and deodorization, and then cooled to 50°C;

[0113] S6: Enzymatic hydrolysis: The sterilized and deodorized slurry was placed in a water bath and heated with alkaline protease and papain for enzymatic hydrolysis, with an enzymatic hydrolysis temperature of 50°C, an enzymatic hydrolysis time of 20min, and an alkaline protease and papain addition amount of 5wt%;

[0114] S7: Metal ion solution adjustment: 0.5wt% FeCl2 and 3.0wt% CaCl2 were added to the enzymatically hydrolyzed slurry and stirred;

[0115] S8: Sterilization and concentration: The temperature for high-temperature sterilization was 90°C, the time for high-temperature sterilization was 2min, then heating and concentration were performed, with a heating and concentration temperature of 80°C and a heating and concentration time of 15min;

[0116] S9: Spray drying: The sterilized and concentrated material was subjected to spray drying, with an inlet air temperature of 160-175°C and an exhaust air temperature of 70-80°C;

[0117] Example 2: The steps and related parameters prepared in this example are as follows:

[0118] S1: Pretreatment of soybean: the soybean is quickly sprayed with hot water at a temperature of 50°C for 15s, and then dried at a temperature of 95°C with a discharge temperature of 50°C;

[0119] S2: Refining: the pretreated soybean is added to hot water and sodium bicarbonate solution for refining, the mass ratio of soybean to hot water is 1:9, the temperature of hot water is 80°C, the concentration of sodium bicarbonate solution is 2.5wt%, and a slurry with a pH value of 7.0-7.4 is obtained;

[0120] S3: Enzyme inactivation: the refined slurry is added to 80°C hot water and steam is introduced for enzyme inactivation;

[0121] S4: Centrifugal dewatering: the enzyme-inactivated slurry is fed into a centrifugal separator for centrifugal dewatering, and a slurry is obtained for standby;

[0122] S5: Sterilization and deodorization: the slurry is heated to 125°C for sterilization and deodorization for 5s, and then cooled to 50°C;

[0123] S6: Enzymatic hydrolysis: the sterilized and deodorized slurry is placed in a water bath and heated for enzymatic hydrolysis with alkaline protease and papain, the enzymatic hydrolysis temperature is 50°C, the enzymatic hydrolysis time is 25min, and the addition amount of alkaline protease and papain is 5wt%;

[0124] S7: Metal ion solution adjustment: 0.7wt% FeCl2 and 4.0wt% CaCl2 are added to the enzymatically hydrolyzed slurry for stirring;

[0125] S8: Sterilization and concentration: the temperature for high-temperature sterilization is 90°C, the time for high-temperature sterilization is 2min, then heated for concentration, the temperature for heating concentration is 80°C, and the time for heating concentration is 15min;

[0126] S9: Spray drying: the sterilized and concentrated material is subjected to spray drying, the inlet air temperature for spray drying is 160-175°C, and the exhaust air temperature is 70-80°C.

[0127] Example 3: The steps and related parameter settings prepared in this example are as follows:

[0128] S1: Pretreatment of soybean: the soybean is quickly sprayed with hot water at a temperature of 60°C for 10s, and then dried at a temperature of 95°C with a discharge temperature of 50°C;

[0129] S2: Refining: the pretreated soybean is added to hot water and sodium bicarbonate solution for refining, the mass ratio of soybean to hot water is 1:9, the temperature of hot water is 85°C, the concentration of sodium bicarbonate solution is 2.5wt%, and a slurry with a pH value of 7.0-7.4 is obtained;

[0130] S3: Enzyme inactivation: the milled slurry is added to 80℃ hot water and steam is introduced for enzyme inactivation;

[0131] S4: Centrifugal dewatering: the enzyme-inactivated slurry is fed into a decanter centrifuge, centrifugal dewatering is performed, and a slurry is obtained for standby;

[0132] S5: Sterilization and deodorization: the slurry is heated to 125℃ for sterilization and deodorization for 5s, and then cooled to 50℃;

[0133] S6: Enzymolysis: the sterilized and deodorized slurry is placed in a water bath, alkaline protease and papain are added, and heating enzymolysis is performed, the enzymolysis temperature is 55℃, the enzymolysis time is 20min, and the addition amount of alkaline protease and papain is 5wt%;

[0134] S7: Metal ion solution adjustment: 1.0wt% of FeCl2 and 5.0wt% of CaCl2 are added to the enzymolyzed slurry for stirring;

[0135] S8: Sterilization and concentration: the high-temperature sterilization temperature is 90℃, the high-temperature sterilization time is 2min, then heating concentration is performed, the heating concentration temperature is 80℃, and the heating concentration time is 15min;

[0136] S9: Spray drying: the sterilized and concentrated material is subjected to spray drying, the inlet air temperature of spray drying is 160-175℃, and the exhaust air temperature is 70-80℃.

[0137] To more directly illustrate the technical effects of the present application, a comparative example is set as a control, and the steps and parameter settings of the comparative example are as follows:

[0138] S1: Soybean pretreatment: the drying temperature is 95℃, and the exhaust air temperature is 45℃;

[0139] S2: Milling: the pretreated soybeans are added to hot water and sodium bicarbonate aqueous solution for milling, the mass ratio of soybeans to hot water is (1:8), the temperature of hot water is 85℃, the concentration of sodium bicarbonate aqueous solution is 2.5wt%, and a slurry with a pH value of 7.0-7.4 is obtained;

[0140] S3: Enzyme inactivation: the milled slurry is added to 80℃ hot water and steam is introduced for enzyme inactivation;

[0141] S4: Centrifugal dewatering: the enzyme-inactivated slurry is fed into a decanter centrifuge, centrifugal dewatering is performed, and a slurry is obtained for standby;

[0142] S5: Sterilization and deodorization: the slurry is heated to 125℃ for sterilization and deodorization for 5s, and then cooled to 50℃;

[0143] S6: Enzymolysis: After the sterilization and deodorization of the slurry, the slurry was placed in a water bath, and alkaline protease and papain were added for heating and enzymolysis. The enzymolysis temperature was 55°C, the enzymolysis time was 20 min, and the addition amount of alkaline protease and papain was 5wt%.

[0144] S7: Sterilization and concentration: The sterilization temperature was 90°C, the sterilization time was 2 min, then heating and concentration were performed. The heating and concentration temperature was 80°C, and the heating and concentration time was 15 min.

[0145] S8: Spray drying: The material after sterilization and concentration was subjected to spray drying. The inlet air temperature of spray drying was 160-175°C, and the exhaust air temperature was 70-80°C.

[0146] Table 1: Peeling rate of soybean products obtained by the comparative example and examples 1-3

[0147] Soybean hulling rate Comparative Example 73.0 Example 1 75.8 Example 2 76.2 Example 3 78.2

[0148] Table 1

[0149] As shown in Table 1, by comparing the peeling rate of soybean products obtained by the comparative example and examples 1-3, the peeling rate of soybean prepared by the present application is significantly increased, the moisture of soybean is improved, which helps the rapid progress of the drying and peeling process, reduces the loss of nutritional components in the peeling process, and improves the yield.

[0150] In example 3, the temperature of hot water was 60°C, and the peeling rate reached 78.2, which was the best peeling effect of soybean powder. This shows that 60°C is the best temperature for pectin melting (pectin gel state→sol state), and hot spraying makes the pectin on the surface of the seed coat quickly dissolve, which weakens the adhesion between the seed coat and the cotyledon; hot water penetrates the seed coat pores and forms a micron-level water film layer between the seed coat and the cotyledon, which reduces the interfacial friction and improves the transmission efficiency of the peeling mechanical force. In addition, short-time spraying only makes the seed coat surface absorb water, generates swelling stress, and further improves the peeling rate.

[0151] Table 2: Polypeptide chelation rate of products obtained by the comparative example and examples 1-3

[0152]

[0153]

[0154] As shown in Table 2, by comparing the polypeptide chelation rate of soybean powder obtained by examples 1-3 and the comparative example, the polypeptide chelation rate in example 3 was the highest, reaching 78.62, which shows that the addition of 1.0wt% FeCl2 and 5.0wt% CaCl2 to the enzymolysis slurry. When the mass fraction of FeCl2 is 1.0wt%, the peptide chelation ability is the strongest (Fe 2+The FeCl2 content is 1.0wt% when the molar ratio of the active peptide and the carboxyl group is 1:4.

[0155] In conclusion, the present application solves the problems of low calcium and iron content, low absorption rate, low peeling rate, and strong soybean odor in traditional soybean powder by the innovative integration of ion regulation, enzymatic hydrolysis, and spray drying.

[0156] By optimizing the pretreatment, enzymatic hydrolysis, and mineral fortification steps, the peeling rate, nutritional value, and functionality of the soybean powder are further improved.

[0157] By optimizing the peeling process of soybeans with 40-60℃ hot water (the peeling rate is up to 78.2%), combined with 80-85℃ alkaline pulping, 125℃ instantaneous sterilization and deodorization, and 50-55℃ double enzymolysis (alkaline protease and papain synergistic action for 20-25 minutes), the protein digestion rate is significantly improved and the metal chelation sites are exposed; then 0.5-1.0% FeCl2 and 3.0-5.0% CaCl2 are added for ion regulation to form polypeptide iron chelates with high bioavailability (the chelation rate is up to 78.62%), and calcium is simultaneously fortified to improve the particle stability and flavor; finally, the spray drying process with 160-175℃ inlet air and 70-80℃ exhaust air is used to achieve efficient dehydration and sterilization while preserving protein function and heat-sensitive nutrients, resulting in functional soybean powder with high solubility, high protein digestion rate, and rich in bioactive peptides and minerals (iron content up to 35mg / 100g).

[0158] The above only describes the preferred embodiments of the present application and is not intended to limit the present application. Those skilled in the art can make various modifications and changes to the present application. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. A method for preparing high nutritional soybean flour by ion- adjusting combined spray drying, characterized in that, The method comprises the following steps: S1: soybean pretreatment: the process of the soybean pretreatment comprises rapidly spraying the soybean with hot water, and then drying and peeling the rapidly sprayed soybean; S2: grinding: the pretreated soybean in step S1 is added into hot water and a sodium bicarbonate aqueous solution for grinding to obtain a slurry with a pH value of 7.0-7.4; S3: enzyme inactivation: hot water is added into the obtained slurry in step S2, and steam is introduced for enzyme inactivation to obtain enzyme-inactivated slurry; S4: centrifugal dewatering: the enzyme-inactivated slurry obtained in step S3 is punched into a centrifugal separator for centrifugal dewatering to obtain slurry for standby use; S5: sterilization and deodorization: the slurry obtained in step S4 is heated for sterilization and deodorization, and then cooled after the sterilization and deodorization; S6: enzyme hydrolysis: the slurry after the sterilization and deodorization obtained in step S5 is placed into a water bath, and alkaline protease and papain are added for heating and enzyme hydrolysis to obtain enzyme-hydrolyzed slurry; S7: metal ion solution adjustment: FeCl2 solution and CaCl2 solution are added into the enzyme-hydrolyzed slurry obtained in step S6 for stirring to obtain ion-adjusted slurry; S8: sterilization and concentration: the ion-adjusted slurry obtained in step S7 is subjected to high-temperature sterilization and then heated for concentration to obtain concentrated material; S9: spray drying: the concentrated material obtained in step S8 is subjected to spray drying to obtain high-nutrition soybean powder.

2. The method of claim 1, wherein the method is characterized by, In step S1, the soybean is rapidly sprayed with hot water, the temperature of the hot water is 40-60℃, and the spraying time is 10-20s.

3. The method of claim 1, wherein the method is characterized by, In step S2, the mass ratio of the soybean to the hot water is 1:(9-10), the temperature of the hot water is 80-85℃, and the concentration of the sodium bicarbonate aqueous solution is 2.0-3.5wt%.

4. The method of claim 1, wherein the method is characterized by, In step S3, the added hot water has a temperature of 80℃.

5. The method of claim 1, wherein the method is characterized by, In step S4, the centrifugal dewatering is performed at a centrifugal speed of 3000-5000rpm for 3-5min.

6. The method of claim 1, wherein the method is a method of preparing high nutritional soybean powder by ion regulation combined spray drying, characterized in that, In step S5, the heating temperature for the sterilization and deodorization is 125℃, the deodorization time is 5s, and the sterilization and deodorization are completed and then cooled to 50℃.

7. The method of claim 1, wherein the method is a method of preparing high nutritional soybean flour by ion regulation combined spray drying, characterized by, In step S6, the enzyme hydrolysis is performed at a temperature of 50-55℃ for 20-25min, and the mass fraction of the added alkaline protease and papain is 5wt%.

8. The method of claim 1, wherein the method is a method of preparing high nutritional soybean flour by ion regulation combined spray drying, characterized by, In step S7, the mass fraction of the added FeCl2 in the enzyme-hydrolyzed slurry is 0.5-1.0wt%, and the mass fraction of the added CaCl2 is 3.0-5.0wt%.

9. The method of claim 1, wherein the method is a method of preparing high nutritional soybean flour by ion regulation combined spray drying, characterized by, In step S8, the high-temperature sterilization is performed at a temperature of 90℃ for 2min.

10. The method of claim 1, wherein the method is a method of preparing high nutritional soybean flour by ion regulation combined spray drying, characterized by, In step S9, the inlet air temperature for the spray drying is 160-175℃, and the exhaust air temperature is 70-80℃.

Images