Preparation method of high-protein soymilk containing soybean peptides

Abstract

The present invention relates to the technical field of soy milk preparation, and discloses a method for preparing high-protein soy milk containing soybean peptides, comprising the following steps: (1) roasting and peeling soybeans; (2) grinding: adding water to the peeled soybeans for dry grinding to obtain a milled paste; (3) first enzymatic hydrolysis: adding a mixed solution of cellulase, xylanase, pectinase, and saccharifying enzyme to the milled paste for enzymatic hydrolysis to obtain an enzymatic hydrolysis solution I; (4) second enzymatic hydrolysis: adding a composite enzyme to the enzymatic hydrolysis solution I for enzymatic hydrolysis to obtain an enzymatic hydrolysis solution II; (5) boiling the enzymatic hydrolysis solution II to inactivate the enzymes, thereby obtaining high-protein soy milk containing soybean peptides. The high-protein soy milk containing soybean peptides prepared by the present invention has high nutritional value, is delicate and fragrant, has no beany smell or bitterness, has a slight natural sweetness, is in a stable emulsified state, and is not prone to stratification.

Description

Technical Field

[0001] The invention relates to the technical field of soy milk preparation, in particular to a method for preparing high-protein soy milk containing soybean peptides. Background Art

[0002] Soy protein is a plant-based protein. In terms of amino acid content, it is the only plant protein reported to contain all nine essential amino acids required by the human body at levels that meet human requirements. Its amino acid profile is similar to that of milk protein, making it a recognized complete protein. Soy protein has a digestibility of only 65%. Processing methods such as soaking, grinding, heating, fermentation, and germination can generally improve protein absorption. Soy milk, a common soy product, is highly nutritious and popular among consumers. Traditional soy milk production methods result in low soy protein dissolution rates, reducing both the nutritional value and market value of soy milk products. They also impart a distinctive beany and bitter flavor, which affects the taste. Consequently, the protein content of currently available soy milk is low, typically ranging from 1 to 4 grams per 100 grams. Furthermore, the soy protein in soy milk is encapsulated by a fibrous membrane, resulting in a digestibility of only 70% to 80%. Improving the extraction and digestibility of soy protein during soy milk production is a key challenge for soy milk manufacturers.

[0003] Soy peptides are the hydrolyzed products of soy protein and are composed of a mixture of polypeptide molecules arranged in different amino acid sequences. Their amino acid composition is almost identical to that of soy protein, with a good balance and rich content of essential amino acids. Compared to soy protein, soy peptides are easier to digest and absorb, have low antigenicity, and contain certain physiologically active substances that have multiple physiological functions in the body. Currently, there are three main raw materials for preparing soy peptides: soy protein isolate, soy flour, and soy meal. The methods and technologies used to produce soy peptides primarily include chemical hydrolysis, enzymatic hydrolysis, and microbial fermentation. The preparation of soy milk products containing soy peptides requires the addition of soy peptide powder, which not only increases costs for the company, but also the bitterness of commercially available soy peptide raw materials affects the flavor of the soy milk, restricting the market development of soy milk containing soy peptides. Summary of the Invention

[0004] In order to solve the above technical problems, the present invention provides a method for preparing high-protein soy milk containing soybean peptides. The prepared soy milk not only contains soybean peptides but also contains a high content of protein, which greatly improves the nutritional value of soybeans and eliminates the beany smell and bitterness. The soy milk product has excellent flavor and improved market competitiveness. It is suitable for people who need to supplement high-quality protein.

[0005] The object of the present invention is achieved by the following technical solution: A method for preparing high-protein soymilk containing soybean peptides, characterized by comprising the following steps:

[0006] (1) Roasting and peeling of soybeans;

[0007] (2) Refining: Dry grinding of dehulled soybeans with water to obtain a paste;

[0008] (3) First enzymatic hydrolysis: adding a mixture of cellulase, xylanase, pectinase, and saccharifying enzyme to the milled paste for enzymatic hydrolysis to obtain enzymatic hydrolyzate I;

[0009] (4) Second enzymatic hydrolysis: adding a complex enzyme to the enzymatic hydrolysis solution I to obtain enzymatic hydrolysis solution II;

[0010] (5) The enzymatic hydrolysate II is boiled to inactivate the enzyme, thereby obtaining high-protein soy milk containing soybean peptides.

[0011] The present invention provides a method for preparing high-protein soymilk containing soybean peptides. The method comprises roasting, peeling, grinding, enzymatic hydrolysis, micro-pressure cooking, extrusion filtration, secondary filtration, cooling, blending, homogenization, sterilization, and aseptic filling of soybeans to obtain high-protein soymilk containing soybean peptides. The method employs a dry grinding process without the need for soaking equipment, saving water and costs, making product quality easier to control, reducing quality issues that may occur during the soaking process, significantly shortening pre-treatment time, and avoiding the potential risk of microbial growth that may occur during the soaking process. Furthermore, since dry beans are more accurately measured than wet beans, the material-to-water ratio is easier to control.

[0012] Under the action of cellulase and pectinase, the outer fiber film of soy protein is effectively destroyed, effectively reducing the viscosity of the product; under the action of xylanase and saccharifying enzyme, the sweetness of the product is increased; under the micro-hydrolysis of the complex enzyme, some proteins are converted into peptides and free amino acids. Depending on the product requirements, cellulase, pectinase, xylanase, and saccharifying enzyme can be added together or enzyme preparations can be added in batches and time periods for enzymatic hydrolysis. Both processes have their advantages and disadvantages. Adding enzyme preparations together eliminates the need for multiple feedings, is simple to operate, and has a fast reaction speed and short reaction time. Adding enzyme preparations in batches can effectively control various product indicators and meet different market requirements.

[0013] The processed soy milk not only removes the components in soybeans that are not conducive to nutrient absorption, but also breaks down the soy protein to make it easier to digest and absorb. The digestion and absorption rate can reach more than 95%, greatly improving the nutritional value of soybeans. It is especially suitable for the elderly, children and other people with weak digestion who need to supplement high-quality protein.

[0014] Preferably, the second enzymatic hydrolysis comprises the following steps:

[0015] i. Add sodium tripolyphosphate to the enzymatic hydrolysate I for phosphorylation treatment;

[0016] ii. adding alkaline protease for enzymatic hydrolysis to obtain an enzymatic hydrolyzate;

[0017] iii. adding lysine to the xanthan gum aqueous solution under high-speed shear conditions to obtain a mixed solution; then mixing the mixed solution with an enzymatic hydrolyzate under high-speed shear conditions, and then adding transglutaminase for cross-linking;

[0018] iv. Cool and adjust the pH to 7 to obtain enzymatic hydrolyzate II.

[0019] Protein phosphorylation utilizes specific oxygen or nitrogen atoms on the active groups of protein side chains to form an esterification reaction, thereby introducing a large number of phosphate groups. The negative charge increases the repulsive force between droplets, thereby improving dispersibility. Subsequent enzymatic hydrolysis with alkaline protease facilitates hydrolysis into peptides and amino acids, reducing the protein's astringency and improving its taste. This also exposes the fishy groups, facilitating odor removal.

[0020] Adding xanthan gum to soy protein facilitates protein emulsification. High-speed shearing dramatically reduces the viscosity of the xanthan gum solution and allows small lysine molecules to diffuse evenly throughout the xanthan gum molecules. The mutual attraction between positively and negatively charged atoms / groups enhances structural stability. Furthermore, lysine is an essential amino acid, enhancing the added value of soy milk. Furthermore, xanthan gum swells further after addition to the alkaline enzymatic hydrolysate. Further high-speed shearing further enhances the dispersion between the mixture and the enzymatic hydrolysate, further enhancing the xanthan gum's high emulsifying and stabilizing properties and preventing delamination. The addition of transglutaminase catalyzes covalent crosslinking between proteins. This crosslinking of the hydrolyzed proteins prevents the release of bitter peptides from excessive hydrolysis and reduces the protein's gel-forming properties, which can affect the soy milk's taste. Furthermore, transglutaminase catalyzes the binding of ε-amino groups on lysine in xanthan gum to γ-amide groups on glutamic acid in the protein, enhancing binding stability. Covalent crosslinking also alters the amino acid composition and improves the protein's functional properties.

[0021] Preferably, in step i, the amount of sodium tripolyphosphate added is 1.5-2% of the mass of the enzymatic hydrolysis solution I; the conditions for the phosphorylation treatment are: pH 8-9, reaction at a temperature of 25-35°C for 30-60 minutes.

[0022] Preferably, in step ii, the amount of alkaline protease added is 0.7-0.9% of the mass of the enzymatic hydrolysis solution I; the enzymatic hydrolysis conditions are: pH 9.0-9.5, reaction at a temperature of 45-55° C. for 30-40 minutes.

[0023] Preferably, in step iii, the high-speed shearing condition is 2000-4000 rpm; the mass concentration of the xanthan gum aqueous solution is 1-1.5%; the added amount of lysine is 0.2-0.3% of the mass of the xanthan gum aqueous solution; and the mass ratio of the mixed solution to the enzymatic hydrolyzate is 1:10-12.

[0024] The high-speed shearing process can also make small-molecule volatile fishy compounds escape more easily, reducing the beany smell.

[0025] Preferably, in step iii, the amount of transglutaminase added is 0.05-0.06% of the mass of the enzymatic hydrolysate.

[0026] Preferably, in step iii, the cross-linking condition is to react at a temperature of 35 to 45° C. for 30 to 40 minutes.

[0027] By combining double-enzyme hydrolysis with phosphorylation, not only can the degree of hydrolysis be limited, so as to avoid the complete destruction of the secondary structure of natural soy protein and the production of a large amount of bitter peptides due to excessive hydrolysis and polymerization, resulting in an unpleasant bitter taste and affecting product quality, but also moderate cross-linking can be controlled by controlling conditions to avoid the production of larger aggregated proteins that affect the dispersibility of the product, ensuring that the molecular weight of the product is within a controllable range, and improving the emulsification stability, ultimately producing soy milk with a high protein concentration, delicate taste, and non-stratification.

[0028] Preferably, the temperature of the first enzymatic hydrolysis is 45-70°C, and the time is 10-30 min; the amount of the cellulase added is 0.1-0.3% of the mass of the ground paste; the amount of the xylanase added is 0.3-0.5% of the mass of the ground paste; the amount of the pectinase added is 0.3-0.5% of the mass of the ground paste; and the amount of the saccharifying enzyme added is 0.2-0.4% of the mass of the ground paste.

[0029] Preferably, the temperature of the dry grinding is 50-70° C., and the material-water ratio is 1:4-1:6.

[0030] Preferably, the soybean roasting comprises the following steps: screening and removing impurities from the soybeans, and roasting them at 60-85° C. for 2-6 hours; and the peeling rate of the soybean peeling is above 85%.

[0031] Compared with the prior art, the present invention has the following beneficial effects:

[0032] (1) The processed soy milk not only removes the components in soybeans that are not conducive to nutrient absorption, but also makes the soybean protein easier to digest and absorb. The digestion and absorption rate can reach more than 95%, which greatly improves the nutritional value of soybeans. It is especially suitable for people with weak digestion, such as the elderly and children, who need to supplement high-quality protein.

[0033] (2) The combination of double enzyme hydrolysis and phosphorylation can not only limit the degree of hydrolysis, but also control the appropriate cross-linking by controlling the conditions, and also improve the emulsification stability, ultimately producing soy milk with high protein concentration, delicate taste, and non-stratification;

[0034] (3) High-protein soy milk containing soybean peptides is delicate and fragrant, has no beany smell or bitterness, has a slight natural sweetness, is stable, has no stratification, and has a shelf life of about 9 months. DETAILED DESCRIPTION

[0035] The technical solutions of the present invention are described below with specific embodiments, but the protection scope of the present invention is not limited thereto:

[0036] A method for preparing high-protein soymilk containing soybean peptides comprises the following steps:

[0037] (1) Soybean baking and peeling: Soybeans are screened and impurities removed, and baked at 60-85°C for 2-6 hours. The moisture content of the soybeans is controlled below 10%. The baked soybeans are peeled in a peeling machine with a peeling rate of more than 85%. The peeled soybeans are placed in a bean storage tank for no more than 5 days.

[0038] (2) Grinding: After dehulling, add water to the soybeans for dry grinding at a temperature of 50-70°C and a material-water ratio of 1:4-1:6 to obtain a paste.

[0039] (3) First enzymatic hydrolysis: Add a mixture of cellulase, xylanase, pectinase and saccharifying enzyme to the mill paste, wherein the amount of cellulase added is 0.1-0.3% of the mass of the mill paste; the amount of xylanase added is 0.3-0.5% of the mass of the mill paste; the amount of pectinase added is 0.3-0.5% of the mass of the mill paste; and the amount of saccharifying enzyme added is 0.2-0.4% of the mass of the mill paste. Perform enzymatic hydrolysis at a temperature of 45-70°C and a time of 10-30 min to obtain enzymatic hydrolyzate I.

[0040] (4) Second enzymatic hydrolysis:

[0041] i. Add sodium tripolyphosphate to the enzymatic hydrolysate I in an amount of 1.5-2% by mass of the enzymatic hydrolysate I, perform phosphorylation treatment, adjust the pH to 8.0-9.0, and react at a temperature of 25-35° C. for 30-60 minutes;

[0042] ii. adding alkaline protease for enzymatic hydrolysis, wherein the amount of alkaline protease added is 0.7-0.9% of the mass of the enzymatic hydrolysis solution I, the pH is 9.0-9.5, and the reaction is carried out at a temperature of 45-55° C. for 30-40 minutes to obtain an enzymatic hydrolysis solution;

[0043] iii. Adding lysine to a xanthan gum aqueous solution having a mass concentration of 1 to 1.5% under high shear conditions (2000 to 4000 rpm), wherein the amount of lysine added is 0.2 to 0.3% by mass of the xanthan gum aqueous solution, to obtain a mixed solution; then, mixing the mixed solution and an enzymatic hydrolysate at a mass ratio of 1:10 to 12 under high shear conditions (2000 to 4000 rpm), and then adding transglutaminase, wherein the amount of transglutaminase added is 0.05 to 0.06% by mass of the enzymatic hydrolysate, and performing a cross-linking reaction at a temperature of 35 to 45° C. for 30 to 40 minutes;

[0044] iv. Cool and adjust the pH to 7 to obtain enzymatic hydrolyzate II.

[0045] (5) The enzymatic hydrolysate II is boiled to inactivate the enzyme at a temperature of 105-115°C, so that the bean paste is thoroughly cooked and the enzyme is inactivated, thereby producing the unique aroma and taste of soy milk; the boiled bean paste is extruded and filtered, the mesh size of the metal filter is controlled at 80-120 meshes, the moisture content of the bean dregs is controlled below 83%, the bean dregs squeezed once are added with water for a second extrusion, the second soy milk is refluxed for grinding, the moisture content of the second extruded bean dregs is ≤83%, and the protein content is ≤3%; the extruded soy milk is filtered twice through a 180-300 mesh vibrating screen to obtain the soy milk pulp, and after cooling, blending, homogenizing, sterilizing, and aseptic filling, high-protein soy milk containing soybean peptides is obtained.

[0046] Example 1

[0047] (1) Soybean roasting and peeling: Soybeans are screened and impurities removed, and roasted at 80°C for 4 hours. The moisture content of the soybeans is controlled below 10%. The roasted soybeans are peeled in a peeling machine with a peeling rate of 93%. The peeled soybeans are placed in a bean storage tank and left for 3 days.

[0048] (2) Grinding: After dehulling, add water to the soybeans and perform dry grinding at a temperature of 65°C and a material-water ratio of 1:5 to obtain a paste.

[0049] (3) First enzymatic hydrolysis: A mixture of cellulase (accounting for 0.2% of the mass of the milled paste), xylanase (accounting for 0.4% of the mass of the milled paste), pectinase (accounting for 0.4% of the mass of the milled paste), and saccharifying enzyme (accounting for 0.3% of the mass of the milled paste) was added to the milled paste for enzymatic hydrolysis at a temperature of 55°C for 25 min to obtain enzymatic hydrolyzate I.

[0050] (4) Second enzymatic hydrolysis:

[0051] i. Add 1.8% sodium tripolyphosphate by weight of enzymatic hydrolysate I to the enzymatic hydrolysate I for phosphorylation treatment, with the pH value being 8.0 to 9.0, and react at 35°C for 45 minutes;

[0052] ii. adding alkaline protease accounting for 0.9% by weight of the enzymatic hydrolysate I for enzymatic hydrolysis at a pH of 9.0 to 9.5, reacting at a temperature of 50° C. for 30 minutes to obtain an enzymatic hydrolysate;

[0053] iii. Lysine (0.2% by mass of the xanthan gum solution) was added to a 1.2% xanthan gum aqueous solution under high shear conditions (3000 rpm) to obtain a mixed solution; the mixed solution and the enzymatic hydrolysate were then mixed at a mass ratio of 1:10 under high shear conditions (3000 rpm), and 0.053% transglutaminase by mass of the enzymatic hydrolysate was added, and the mixture was cross-linked at 45°C for 30 minutes;

[0054] iv. Cool and adjust the pH to 7 to obtain enzymatic hydrolyzate II.

[0055] (5) The enzymatic hydrolysate II is boiled and the enzyme is inactivated at a temperature of 110°C, so that the bean paste is thoroughly cooked and the enzyme is inactivated, thereby producing the unique aroma and taste of soy milk; the boiled bean paste is extruded and filtered, the metal filter mesh is 100 mesh, and the moisture content of the bean dregs is controlled below 83%. The bean dregs squeezed once are added with water for a second extrusion, and the second soy milk is refluxed for grinding. The moisture content of the second extruded bean dregs is ≤83%, and the protein content is ≤3%; the extruded soy milk is filtered twice through a 250-mesh vibrating screen to obtain the soy milk pulp, and after cooling, blending, homogenizing, sterilizing, and aseptic filling, high-protein soy milk containing soybean peptides is obtained.

[0056] Example 2

[0057] The difference from Example 1 is that the second enzymatic hydrolysis process is different.

[0058] i. Add 2% sodium tripolyphosphate by weight of enzymatic hydrolysate I to the enzymatic hydrolysate I for phosphorylation treatment, with the pH value being 8.0 to 9.0, and react at 35°C for 35 minutes;

[0059] ii. adding alkaline protease accounting for 0.8% by weight of the enzymatic hydrolysate I for enzymatic hydrolysis at a pH of 9.0 to 9.5 and reacting at a temperature of 55° C. for 35 minutes to obtain an enzymatic hydrolysate;

[0060] iii. Lysine (0.3% by mass of the xanthan gum solution) was added to a 1.5% xanthan gum aqueous solution under high shear conditions (4000 rpm) to obtain a mixed solution; the mixed solution and the enzymatic hydrolysate were then mixed at a mass ratio of 1:10 under high shear conditions (4000 rpm), and 0.06% transglutaminase by mass of the enzymatic hydrolysate was added, and the mixture was cross-linked at 40°C for 35 minutes;

[0061] iv. Cool and adjust the pH to 7 to obtain enzymatic hydrolyzate II.

[0062] Example 3

[0063] The difference from Example 1 is that the second enzymatic hydrolysis process is different.

[0064] i. Add 1.5% sodium tripolyphosphate by weight of enzymatic hydrolysate I to the enzymatic hydrolysate I for phosphorylation treatment, with the pH value being 8.0 to 9.0, and react at 25°C for 60 minutes;

[0065] ii. adding 0.7% by weight of alkaline protease to the enzymatic hydrolysis solution I for enzymatic hydrolysis at a pH of 9.0 to 9.5 and reacting at a temperature of 45° C. for 40 minutes to obtain an enzymatic hydrolysis solution;

[0066] iii. Lysine (0.25% by mass of the xanthan gum solution) was added to a 1.2% xanthan gum aqueous solution under high shear conditions (2000 rpm) to obtain a mixed solution; the mixed solution and the enzymatic hydrolysate were then mixed at a mass ratio of 1:12 under high shear conditions (2000 rpm), and 0.055% transglutaminase by mass of the enzymatic hydrolysate was added, and the mixture was cross-linked at 45°C for 40 minutes;

[0067] iv. Cool and adjust the pH to 7 to obtain enzymatic hydrolyzate II.

[0068] Example 4

[0069] (1) Soybean roasting and peeling: Soybeans are screened and impurities removed, and roasted at 70°C for 6 hours. The moisture content of the soybeans is controlled below 10%. The roasted soybeans are peeled in a peeling machine with a peeling rate of 93%. The peeled soybeans are placed in a bean storage tank and left for 3 days.

[0070] (2) Grinding: After dehulling, add water to the soybeans and perform dry grinding at a temperature of 70°C and a material-water ratio of 1:6 to obtain a paste.

[0071] (3) First enzymatic hydrolysis: A mixture of cellulase (accounting for 0.3% of the mass of the milled paste), xylanase (accounting for 0.3% of the mass of the milled paste), pectinase (accounting for 0.3% of the mass of the milled paste), and saccharifying enzyme (accounting for 0.4% of the mass of the milled paste) was added to the milled paste for enzymatic hydrolysis at a temperature of 55°C for 25 min to obtain enzymatic hydrolyzate I.

[0072] (4) Second enzymatic hydrolysis:

[0073] i. Add 1.8% sodium tripolyphosphate by weight of enzymatic hydrolysate I to the enzymatic hydrolysate I for phosphorylation treatment, with the pH value being 8.0 to 9.0, and react at 35°C for 45 minutes;

[0074] ii. adding alkaline protease accounting for 0.9% by weight of the enzymatic hydrolysate I for enzymatic hydrolysis at a pH of 9.0 to 9.5, reacting at a temperature of 50° C. for 30 minutes to obtain an enzymatic hydrolysate;

[0075] iii. Lysine (0.2% by mass of the xanthan gum solution) was added to a 1.2% xanthan gum aqueous solution under high shear conditions (3000 rpm) to obtain a mixed solution; the mixed solution and the enzymatic hydrolysate were then mixed at a mass ratio of 1:10 under high shear conditions (3000 rpm), and 0.053% transglutaminase by mass of the enzymatic hydrolysate was added, and the mixture was cross-linked at 45°C for 30 minutes;

[0076] iv. Cool and adjust the pH to 7 to obtain enzymatic hydrolyzate II.

[0077] (5) The enzymatic hydrolysate II is boiled and the enzyme is inactivated at a temperature of 110°C, so that the bean paste is thoroughly cooked and the enzyme is inactivated, thereby producing the unique aroma and taste of soy milk; the boiled bean paste is extruded and filtered, the metal filter mesh is 100 mesh, and the moisture content of the bean dregs is controlled below 83%. The bean dregs squeezed once are added with water for a second extrusion, and the second soy milk is refluxed for grinding. The moisture content of the second extruded bean dregs is ≤83%, and the protein content is ≤3%; the extruded soy milk is filtered twice through a 250-mesh vibrating screen to obtain the soy milk pulp, and after cooling, blending, homogenizing, sterilizing, and aseptic filling, high-protein soy milk containing soybean peptides is obtained.

[0078] Comparative Example 1

[0079] The difference from Example 1 is that in the second enzymatic hydrolysis process, only double-enzyme enzymatic hydrolysis is performed.

[0080] i. Adding 0.9% of alkaline protease by weight of the enzymatic hydrolyzate I to the enzymatic hydrolyzate I for enzymatic hydrolysis at a pH of 9.0 to 9.5 and reacting at a temperature of 50° C. for 30 minutes to obtain an enzymatic hydrolyzate;

[0081] ii. adding 0.053% of transglutaminase by weight of the enzymatic hydrolysate, and carrying out a cross-linking reaction at 45° C. for 30 minutes; iii. cooling, and adjusting the pH value to 7 to obtain enzymatic hydrolysate II.

[0082] Comparative Example 2

[0083] The difference from Example 1 is that neutral protease is added during the second enzymatic hydrolysis process.

[0084] i. Add 1.8% sodium tripolyphosphate by weight of enzymatic hydrolysate I to the enzymatic hydrolysate I for phosphorylation treatment, with the pH value being 8.0 to 9.0, and react at 35°C for 45 minutes;

[0085] ii. adding 0.9% by weight of neutral protease to the enzymatic hydrolysate I for enzymatic hydrolysis at a pH of 6.5 to 7.0, reacting at a temperature of 50° C. for 30 minutes to obtain an enzymatic hydrolysate;

[0086] iii. Lysine (0.2% by mass of the xanthan gum solution) was added to a 1.2% xanthan gum aqueous solution under high shear conditions (3000 rpm) to obtain a mixed solution; the mixed solution and the enzymatic hydrolysate were then mixed at a mass ratio of 1:10 under high shear conditions (3000 rpm), and 0.053% transglutaminase by mass of the enzymatic hydrolysate was added, and the mixture was cross-linked at 45°C for 30 minutes;

[0087] iv. Cool and adjust the pH to 7 to obtain enzymatic hydrolyzate II.

[0088] Comparative Example 3

[0089] The difference from Example 1 is that phosphorylation is not performed during the second enzymatic hydrolysis process.

[0090] i. Adding 0.9% of alkaline protease by weight of the enzymatic hydrolyzate I to the enzymatic hydrolyzate I for enzymatic hydrolysis at a pH of 9.0 to 9.5 and reacting at a temperature of 50° C. for 30 minutes to obtain an enzymatic hydrolyzate;

[0091] ii. Lysine (0.2% by mass of the xanthan gum solution) was added to a 1.2% xanthan gum aqueous solution under high shear conditions (3000 rpm) to obtain a mixed solution; the mixed solution and the enzymatic hydrolysate were then mixed at a mass ratio of 1:10 under high shear conditions (3000 rpm), and 0.053% transglutaminase by mass of the enzymatic hydrolysate was added, and the mixture was cross-linked at 45°C for 30 minutes;

[0092] iii. Cool and adjust the pH to 7 to obtain enzymatic hydrolyzate II.

[0093] Comparative Example 4

[0094] The difference from Example 1 is that high-speed shearing was not performed during the second enzymatic hydrolysis process.

[0095] i. Add 1.8% sodium tripolyphosphate by weight of enzymatic hydrolysate I to the enzymatic hydrolysate I for phosphorylation treatment, with the pH value being 8.0 to 9.0, and react at 35°C for 45 minutes;

[0096] ii. adding alkaline protease accounting for 0.9% by weight of the enzymatic hydrolysate I for enzymatic hydrolysis at a pH of 9.0 to 9.5, reacting at a temperature of 50° C. for 30 minutes to obtain an enzymatic hydrolysate;

[0097] iii. adding lysine (0.2% by weight of the xanthan gum aqueous solution) to a 1.2% xanthan gum aqueous solution to obtain a mixed solution; then mixing the mixed solution and the enzymatic hydrolysate at a mass ratio of 1:10, and then adding 0.053% transglutaminase (0.053% by weight of the enzymatic hydrolysate) and carrying out a cross-linking reaction at 45° C. for 30 minutes;

[0098] iv. Cool and adjust the pH to 7 to obtain enzymatic hydrolyzate II.

[0099] Comparative Example 5

[0100] The difference from Example 1 is that no lysine was added during the second enzymatic hydrolysis.

[0101] i. Add 1.8% sodium tripolyphosphate by weight of enzymatic hydrolysate I to the enzymatic hydrolysate I for phosphorylation treatment, with the pH value being 8.0 to 9.0, and react at 35°C for 45 minutes;

[0102] ii. adding alkaline protease accounting for 0.9% by weight of the enzymatic hydrolysate I for enzymatic hydrolysis at a pH of 9.0 to 9.5, reacting at a temperature of 50° C. for 30 minutes to obtain an enzymatic hydrolysate;

[0103] iii. A 1.2% xanthan gum aqueous solution was stirred under high shear conditions (3000 rpm) to obtain a mixed solution; the mixed solution and the enzymatic hydrolysate were then mixed at a mass ratio of 1:10 under high shear conditions (3000 rpm), and 0.053% transglutaminase by mass of the enzymatic hydrolysate was added, and the mixture was cross-linked at 45° C. for 30 minutes;

[0104] iv. Cool and adjust the pH to 7 to obtain enzymatic hydrolyzate II.

[0105] Comparative Example 6

[0106] The difference from Example 1 is that during the second enzymatic hydrolysis process, the cross-linking condition control leads to excessive cross-linking.

[0107] i. Add 1.8% sodium tripolyphosphate by weight of enzymatic hydrolysate I to the enzymatic hydrolysate I for phosphorylation treatment, with the pH value being 8.0 to 9.0, and react at 35°C for 45 minutes;

[0108] ii. adding alkaline protease accounting for 0.9% by weight of the enzymatic hydrolysate I for enzymatic hydrolysis at a pH of 9.0 to 9.5, reacting at a temperature of 50° C. for 30 minutes to obtain an enzymatic hydrolysate;

[0109] iii. Lysine (0.2% by mass of the xanthan gum solution) was added to a 1.2% xanthan gum aqueous solution under high shear conditions (3000 rpm) to obtain a mixed solution; the mixed solution and the enzymatic hydrolysate were then mixed at a mass ratio of 1:10 under high shear conditions (3000 rpm), and 0.075% transglutaminase by mass of the enzymatic hydrolysate was added, and the mixture was cross-linked at 45°C for 60 minutes;

[0110] iv. Cool and adjust the pH to 7 to obtain enzymatic hydrolyzate II.

[0111] Table 1

[0112] project Qualified indicators Color Milky white or light yellow Taste and smell No beany or bitter taste, with the natural sweetness and aroma of soy milk state Homogeneous liquid Protein (g / 100g) ≥6.0 Total free amino acids (g / 100g) ≥0.3 Acid-soluble protein (g / 100g) ≥0.6 Peptide content (g / 100g) ≥0.3

[0113] Note: Acid-soluble protein content = total free amino acid content + peptide content.

[0114] Table 2

[0115]

[0116] Table 3

[0117]

[0118]

[0119] Table 1 shows the qualified indicators for evaluating soy milk. As shown in Table 2, the soy milk of the present invention not only contains a high content of soybean peptides and free amino acids, but also contains a high content of protein, has rich nutritional value, has no beany smell or bitterness, and has the natural sweetness and aroma of soy milk.

[0120] As shown in Table 3, Comparative Example 1 shows that only simple double enzyme enzymolysis can not achieve the technical effect of the present invention, and in Comparative Example 2, alkaline protease is replaced by neutral protease, which does not have an alkaline environment and will not induce the swelling effect of xanthan gum, thereby affecting dispersibility and emulsification. Comparative Example 3 shows that phosphorylation is not carried out, resulting in poor dispersibility, but the excessive degree of phosphorylation also affects subsequent enzymolysis and cross-linking process. Comparative Example 4 shows that high-speed shearing is not carried out. Because the viscosity of the xanthan gum solution is too large, the dispersibility between it and the protein is not good, and the xanthan gum after high-speed shearing can be better with the protein, forming a small amount of polysaccharide-protein Maillard reaction in the subsequent thermal reaction process, which can also improve emulsification effect, and give fragrance to a certain extent, eliminating beany smell. Comparative Example 5 shows that lysine can participate in cross-linking, promotes and promotes emulsification stability, is difficult for stratification, and Comparative Example 6 shows that the parameters of the cross-linking process need to be controlled to avoid producing larger polymerized protein and affecting the dispersibility of the product.

[0121] The above are only preferred embodiments of the present invention and are not intended to limit the patent scope of the present invention. Any equivalent structure or equivalent process transformation made using the description of the present invention, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. A method for preparing high-protein soymilk containing soybean peptides, characterized in that: The steps include: (1) Roasting and peeling of soybeans; (2) Grinding: After dehulling, the soybeans are added with water and dry-grinded to obtain a paste; (3) First enzymatic hydrolysis: Add a mixture of cellulase, xylanase, pectinase, and saccharifying enzyme to the milled paste for enzymatic hydrolysis to obtain enzymatic hydrolyzate I; (4) Second enzymatic hydrolysis: i. Add sodium tripolyphosphate to the enzymatic hydrolysate I, pH 8.0-9.0, and react at 25-35°C for 30-60 minutes; ii. adding alkaline protease for enzymatic hydrolysis to obtain an enzymatic hydrolyzate; iii. adding lysine to the xanthan gum aqueous solution under high-speed shear conditions at 2000-4000 rpm to obtain a mixed solution; then mixing the mixed solution with the enzymatic hydrolyzate under high-speed shear conditions, adding transglutaminase, and carrying out a cross-linking reaction at a temperature of 35-45° C. for 30-40 minutes; iv. cooling, and adjusting the pH to 7 to obtain enzymatic hydrolyzate II; (5) The enzymatic hydrolysate II is boiled to inactivate the enzymes, thereby obtaining high-protein soy milk containing soybean peptides.

2. The method for preparing high-protein soymilk containing soybean peptides according to claim 1, wherein: In step i, the amount of sodium tripolyphosphate added is 1.5-2% of the mass of the enzymatic hydrolyzate I. The conditions for the phosphorylation treatment are: pH 8.0-9.0, and reaction at a temperature of 25-35° C. for 30-60 minutes.

3. The method for preparing high-protein soymilk containing soybean peptides according to claim 1, wherein: In step ii, the amount of alkaline protease added is 0.7-0.9% of the mass of the enzymatic hydrolysis solution I; the enzymatic hydrolysis conditions are: pH 9.0-9.5, reaction temperature 45-55° C. for 30-40 minutes.

4. The method for preparing high-protein soymilk containing soybean peptides according to claim 1, wherein: In step iii, the mass concentration of the xanthan gum aqueous solution is 1-1.5%; the amount of lysine added is 0.2-0.3% of the mass of the xanthan gum aqueous solution; and the mass ratio of the mixed solution to the enzymatic hydrolyzate is 1:10-12.

5. The method for preparing high-protein soymilk containing soybean peptides according to claim 1 or 4, characterized in that: In step iii, the amount of transglutaminase added is 0.05-0.06% of the mass of the enzymatic hydrolyzate.

6. The method for preparing high-protein soymilk containing soybean peptides according to claim 1 or 4, characterized in that: In step iii, the cross-linking condition is to react at a temperature of 40-45° C. for 30-40 minutes.

7. The method for preparing high-protein soymilk containing soybean peptides according to claim 1, wherein: The temperature of the first enzymatic hydrolysis is 45-70° C., and the time is 10-30 min. The amount of cellulase added is 0.1-0.3% of the mass of the milled paste; the amount of xylanase added is 0.3-0.5% of the mass of the milled paste; the amount of pectinase added is 0.3-0.5% of the mass of the milled paste; and the amount of saccharifying enzyme added is 0.2-0.4% of the mass of the milled paste.

8. The method for preparing high-protein soymilk containing soybean peptides according to claim 1 or 7, characterized in that: The temperature of the dry grinding is 50-70° C., and the material-water ratio is 1:4-1:

6.

9. The method for preparing high-protein soymilk containing soybean peptides according to claim 1 or 7, characterized in that: The soybean roasting comprises the following steps: screening and removing impurities from the soybeans, and roasting the soybeans at 60-85° C. for 2-6 hours; and the peeling rate of the peeling is above 85%.

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