Soybean protein isolate with low beany flavor and high meat fiber structure and preparation method thereof

Abstract

The application belongs to the technical field of food processing and relates to a kind of low-beany high-imitated meat fiber structure soybean protein isolate and its preparation method. The steps are as follows: low-temperature defatted soybean meal is mixed with water, and bromelain is added for extraction, and the extract and solid residue are obtained by solid-liquid separation; the extract is adjusted to acidic pH for precipitation, and after standing, centrifugal separation is carried out, and the protein solid phase is collected; the protein solid phase is mixed with water, and the pH value of the system is adjusted to alkaline by adding alkali and reacting; hydrochloric acid is added to adjust the pH of the system to neutral; glutelin and protein glutamine enzyme, glutamine transaminase are added and enzymatic reaction is carried out to prepare neutralized enzymatic hydrolysate; the neutralized enzymatic hydrolysate is sequentially sterilized, flash evaporated, dried and surface sprayed with phospholipid to obtain a low-beany high-imitated meat fiber structure soybean protein isolate. The two key problems of traditional soybean protein isolate, i.e. strong beany smell and poor meat fiber structure after extrusion molding, are solved simultaneously by an integrated process.

Description

Technical Field

[0001] This invention belongs to the field of food processing technology, specifically relating to a soy protein isolate with low beany odor and a meat fiber-like structure and its preparation method. Background Technology

[0002] Soy protein isolate is produced from low-temperature defatted soybean meal through an alkali extraction and acid precipitation process. It has a balanced amino acid composition and outstanding nutritional value, and is widely used in the food and health product industries. However, the unsaturated fatty acids in soybean raw materials are prone to oxidation, producing volatile aldehydes and ketones that cause a fishy smell. This gives the finished product a pungent beany odor, affecting the flavor of the final product and significantly limiting the applicable scenarios and dosage of soy protein isolate.

[0003] Currently, methods for reducing the beany odor of soy protein isolate commonly employ physical and chemical methods. However, deodorization processes such as microbial fermentation are time-consuming and prone to generating off-flavor byproducts. Chemical deodorization methods involve the addition of exogenous additives, posing food safety risks and exhibiting poor stability in deodorization effects. Therefore, the industry urgently needs a deodorization process that requires no exogenous microorganisms or additional chemical additives. Furthermore, when soy protein isolate is used in plant-based meat texture processing, its insufficient gelation and water-holding capacity result in loose protein fibers and poor fiber density after extrusion molding, leading to poor finished product appearance and hindering improvements in the taste and texture of plant-based meat.

[0004] While existing technologies have made improvements to address the beany odor and protein functional defects, significant shortcomings remain: for example, using microbial fermentation combined with secondary washing to remove the beany odor is time-consuming, and multiple washings can cause a large loss of protein, reducing product yield and protein content; using superheated steam pretreatment to inactivate lipoxygenase and combining it with compound protease modification to improve solubility is also problematic, as high-temperature superheating can easily cause irreversible denaturation and precipitation of protein, reducing protein purity. Summary of the Invention

[0005] The purpose of this invention is to provide a soy protein isolate with low beany odor and high meat fiber structure and its preparation method, thereby overcoming the shortcomings of the prior art and solving the two key problems of strong beany odor and poor meat fiber structure after extrusion molding of traditional soy protein isolate through an integrated process.

[0006] To achieve the above objectives, the technical solution of the present invention is as follows: On the one hand, the present invention provides a method for preparing soy protein isolate with low beany odor and high imitation meat fiber structure, comprising the following steps: mixing low-temperature defatted soybean meal with water, adding bromelain for extraction, and obtaining the extract and solid filter residue by solid-liquid separation; The pH of the extract was adjusted to acidic for acid precipitation. After standing, the extract was centrifuged and the protein solid phase was collected. After mixing the protein solid phase with water, sodium hydroxide was added to adjust the pH of the system to alkaline and the reaction was carried out; then, hydrochloric acid was added to adjust the pH of the system to neutral; then gluten powder, protein-glutaminase (PG) and transglutaminase (TG) were added to the system and the enzymatic hydrolysis reaction was carried out to obtain a neutralized enzymatic hydrolysate. The neutralized enzymatic hydrolysate was subjected to sterilization, flash evaporation, and drying processes sequentially to obtain a solid powder. Soybean lecithin was then agglomerated onto the solid powder. This yielded soy protein isolate with a low beany odor and a highly meat-fiber-like structure.

[0007] This preparation method first uses bromelain extraction to degrade the fishy smell substances at the source. Small-molecule fishy impurities are then thoroughly removed through a two-step acid precipitation process. Gluten powder, protein glutaminase, and transglutaminase are added to the system for enzymatic hydrolysis. Because gluten powder is rich in glutamine and lysine groups, it can covalently cross-link with soy protein isolate under the catalysis of protein glutaminase and transglutaminase, pre-constructing dense and ordered complex protein aggregates. This allows the powder to form a firm, layered, meat-like fiber after extrusion. Simultaneously, it improves the system's gel strength, water and oil retention properties, optimizes the rheological processing characteristics of the slurry, improves the appearance and juicy texture of the plant-based meat, and its grain aroma can also help weaken the beany smell. Transglutaminase, acting as a protein cross-linking catalyst, catalyzes the covalent cross-linking of soy protein isolate and wheat gluten, pre-constructing stable and ordered complex protein aggregates under liquid-phase conditions. This enables the powder to form a compact, layered, highly meat-like fiber structure after extrusion, while also improving the system's gel strength, water and oil retention properties, optimizing the appearance and texture of the plant-based meat, and enhancing the thermal stability of the protein network. Finally, instantaneous high-temperature sterilization to inactivate enzymes and flash evaporation to deeply remove volatile odors solve the problems of strong beany odor and poor fiber structure in traditional soy protein isolate.

[0008] On the other hand, the present invention provides a soy protein isolate with a low beany odor and a meat fiber-like structure.

[0009] The beneficial effects of this invention are: The bromelain added in this invention can directionally degrade lipoxygenase and hydrophobic fishy-smelling peptides, inhibiting the formation of fishy-smelling precursors such as hexanal at the source. Through a purification process involving acid precipitation, solid-phase washing, and secondary centrifugation, small-molecule soluble fishy-smelling impurities are significantly removed. Then, residual oxidases are inactivated by instantaneous sterilization, and volatile odor components are removed by flash evaporation. Through source suppression of fishy odor, solid-phase purification, and deep deodorization, the beany odor and various unpleasant odors in the finished product are significantly reduced. Simultaneously, in a protein-neutralized liquid phase environment, gluten powder, protein glutaminase, and transglutaminase are used for isothermal in-situ cross-linking enzymatic hydrolysis, pre-constructing ordered protein cross-linked aggregates before drying. These aggregates can then be extruded to form a distinct, meat-like fiber structure. This simultaneously addresses the industry shortcomings of existing products, such as incomplete deodorization and poor fiber formation. The process is seamless and suitable for large-scale, continuous industrial production of plant-based meat. Detailed Implementation

[0010] Those skilled in the art will understand that the following examples are for illustrative purposes only and should not be considered as limiting the scope of the invention. Specific conditions not specified in the examples were performed under conventional conditions or conditions recommended by the manufacturer. Components not specifying their manufacturers are all commercially available conventional products. Specifically, the bromelain activity is 240 GDU, the protein glutaminase activity is 200 U / g, and the transglutaminase activity is 120 U / g.

[0011] Existing soy protein isolate preparation processes suffer from limitations in simultaneously achieving significant deodorization, preserving protein yield and purity, and optimizing protein gelation and water-holding properties. Furthermore, they struggle to balance low beany odor with excellent meat-like fibrous processing performance. This invention employs a soy protein isolate preparation method that improves plant-based meat tissue protein, masks beany odor, and enhances gel strength and water-holding capacity. This results in a soy protein isolate with low beany odor and a highly meat-like fibrous structure, thereby expanding the application range and dosage of soy protein isolate.

[0012] On the one hand, the present invention provides a method for preparing soy protein isolate with low beany odor and high imitation meat fiber structure, comprising the following steps: mixing low-temperature defatted soybean meal with water, adding bromelain for extraction, and obtaining the extract and solid filter residue by solid-liquid separation; The pH of the extract was adjusted to acidic for acid precipitation. After standing, the extract was centrifuged and the protein solid phase was collected. After mixing the protein solid phase with water, sodium hydroxide was added to adjust the pH of the system to alkaline and the reaction was carried out; then, hydrochloric acid was added to adjust the pH of the system to neutral; then gluten powder, protein glutaminase and transglutaminase were added to the system and enzymatic hydrolysis was carried out to obtain a neutralized enzymatic hydrolysate. The neutralized enzymatic hydrolysate was subjected to sterilization, flash evaporation and drying in sequence to obtain a solid powder; soybean lecithin was agglomerated onto the solid powder to obtain soy protein isolate with a low beany odor and a meat-fiber-like structure.

[0013] Furthermore, the mass ratio of low-temperature defatted soybean meal to water is 1:(8-10); the amount of bromelain added is 0.01-0.2% of the mass of low-temperature defatted soybean meal.

[0014] For example, the mass ratio of low-temperature defatted soybean meal to water is any one of 1:8, 1:9, and 1:10; the amount of bromelain added is any one of 0.01%, 0.05%, 0.1%, 0.15%, and 0.2% of the mass of low-temperature defatted soybean meal.

[0015] Furthermore, the extraction temperature for bromelain was 50-58℃, the pH value was 6.8-7.8, and the extraction time was 30-45 min.

[0016] For example, the extraction temperature of bromelain is any value or range of 50°C, 55°C and 58°C, the pH value is any value or range of 6.8, 7.0, 7.5 and 7.8, and the extraction time is any value or range of 30 min, 35 min, 40 min and 45 min.

[0017] By adding bromelain to extract and treat the beany odor, the enzymatic hydrolysis of bromelain disrupts the three-dimensional structure of soybean protein, releasing the beany odor substances, which are more easily removed in subsequent processing. This effectively solves the problem of beany odor affecting application channels and expands the application scope of soy protein isolate.

[0018] Furthermore, the pH during acid precipitation is 4.5-4.7; the pH of the sodium hydroxide-adjusted system is 9.5-12.5. Hydrochloric acid was used to adjust the pH of the system to 7.0-7.6.

[0019] For example, the pH during acid precipitation is any point or range of 4.5, 4.6, and 4.7; the pH of the system is adjusted by sodium hydroxide to any point or range of 9.5, 10, 10.5, 11, 11.5, 12, and 12.5; and the pH of the system is adjusted by hydrochloric acid to any point or range of 7.0, 7.2, 7.4, and 7.6.

[0020] By acid precipitation and centrifugation, followed by solid-phase water washing and centrifugation again, small-molecule fishy-smelling impurities are significantly removed.

[0021] Furthermore, sodium hydroxide is added to adjust the pH of the system to alkaline, the solid content of the system is 7-13%, and the reaction time is 30-60 min.

[0022] Furthermore, the amount of added gluten powder is 0.5-5‰ of the protein solid phase mass; the amount of added protein glutaminase (PG) is 0.1-0.5‰ of the protein solid phase mass; and the amount of added transglutaminase is 0.5-1.5‰ of the protein solid phase mass.

[0023] For example, the amount of gluten added is any one of the following values ​​or ranges of 0.5‰, 1.0‰, 1.5‰, 2‰, 2.5‰, 3‰, 3.5‰, 4‰, 4.5‰, and 5‰ of the protein solid phase mass; the amount of protein glutaminase (PG) added is any one of the following values ​​or ranges of 0.1‰, 0.2‰, 0.3‰, 0.4‰, and 0.5‰ of the protein solid phase mass; and the amount of transglutaminase added is any one of the following values ​​or ranges of 0.5‰, 1.0‰, and 1.5‰ of the protein solid phase mass.

[0024] By employing alkali-shifting neutralization modification technology to impart a specific conformational state to the protein, and through the formation of a covalent hybrid network by binding with gluten and transglutaminase, as well as the synergistic modification of protein glutaminase and transglutaminase, the problem of non-dense and non-firm puffing of plant meat tissue protein was significantly improved, and the appearance and shapeability of the tissue protein were enhanced.

[0025] Furthermore, the enzymatic hydrolysis reaction is carried out at a temperature of 40-60℃ for 20-40 minutes.

[0026] Furthermore, the sterilization temperature is 145-150℃, and the time is 10-15 seconds.

[0027] Furthermore, the flash evaporation temperature is 70-80℃.

[0028] By sterilizing and inactivating residual transglutaminase, and using flash evaporation to remove volatile small molecules of beany odor, the two work synergistically to produce a product with low beany odor. Before drying, ordered protein cross-linked aggregates are pre-constructed, allowing the dried powder to be directly extruded into distinct layers of meat-like fibers.

[0029] Furthermore, the spraying solution contains 0.1-1 wt‰ soybean lecithin.

[0030] On the other hand, the present invention provides a method for preparing soy protein isolate with a low beany odor and a highly meat-fiber-like structure.

[0031] By optimizing process parameters such as temperature and pH, protein extraction and purification were achieved, ensuring high purity and good quality of the product. The formed covalent hybrid network structure enhanced the gel strength and water retention of the protein, effectively solving the problem of protein loss during use and improving product stability.

[0032] The following is a further explanation with reference to specific embodiments and comparative examples: Example 1 A soy protein isolate with low beany odor and a highly meat-fiber-like structure, and its preparation method, comprising the following steps: (1) Mix low-temperature defatted soybean meal with water at a mass ratio of 1:9, add 0.05% of bromelain by weight of soybean meal; control the water temperature at 55℃ and the pH value at 7.0, stir and extract for 40 min; after completion, separate the solid and liquid, and collect the extract and solid filter residue respectively. (2) Adjust the pH of the obtained extract to 4.7, perform acid precipitation and centrifugation, let it stand, and then centrifuge to separate and collect the protein solid phase; (3) After mixing the protein solid phase with water, add sodium hydroxide to adjust the pH of the system to 10.0, react at a constant temperature for 45 min, and control the solid content of the system to be stable at 10%; then, add 10wt% hydrochloric acid to the system to adjust the pH of the system to 7.2; then add 0.5‰ of protein glutamate, 0.2‰ of protein glutaminase PG and 0.6‰ of transglutaminase TG to the system respectively, transfer to an enzymatic hydrolysis tank, and enzymatically hydrolyze at a constant temperature of 45℃ for 30 min to obtain a neutralized enzymatic hydrolysate; (4) The neutralized enzymatic hydrolysate is sent to the instant sterilization equipment and sterilized at 148°C for 12 seconds; the sterilized enzymatic hydrolysate is transferred to the flash evaporation equipment and the flash evaporation temperature is controlled at 75°C; the material after flash evaporation is dried and coated with 0.5 wt‰ phospholipid to obtain soy protein isolate with low beany smell and high imitation meat fiber structure.

[0033] Example 2 A soy protein isolate with low beany odor and a highly meat-fiber-like structure, and its preparation method, comprising the following steps: (1) Mix low-temperature defatted soybean meal with water at a mass ratio of 1:8, add 0.2% of bromelain by weight of soybean meal; control the water temperature at 58℃ and the pH value at 7.5, stir and extract for 35 min; after completion, separate the solid and liquid, and collect the extract and solid filter residue respectively. (2) Adjust the pH of the obtained extract to 4.7, perform acid precipitation and centrifugation, let it stand, and then centrifuge to separate and collect the protein solid phase; (3) After mixing the protein solid phase with water, add sodium hydroxide to adjust the pH of the system to 11.0, react at a constant temperature for 50 min, and control the solid content of the system to be stable at 9%; then, add 10wt% hydrochloric acid to the system to adjust the pH of the system to 7.4; then add 1‰ of protein glutamate, 0.3‰ of protein glutaminase PG and 1.0‰ of glutaminase TG to the system, transfer to an enzymatic hydrolysis tank, and enzymatically hydrolyze at a constant temperature of 45℃ for 30 min to obtain a neutralized enzymatic hydrolysate; (4) The neutralized enzymatic hydrolysate is sent to the instant sterilization equipment and sterilized at 145°C for 15 seconds; the sterilized enzymatic hydrolysate is transferred to the flash evaporation equipment and the flash evaporation temperature is controlled at 75°C; the material after flash evaporation is dried and 0.2wt‰ soybean lecithin is agglomerated to obtain soybean protein isolate with low beany smell and high imitation meat fiber structure.

[0034] Example 3 A soy protein isolate with low beany odor and a highly meat-fiber-like structure, and its preparation method, comprising the following steps: (1) Mix low-temperature defatted soybean meal with water at a mass ratio of 1:10, add 0.01% of bromelain by weight of soybean meal; control the water temperature at 50℃ and the pH value at 7.8, stir and extract for 45 min; after completion, separate the solid and liquid, and collect the extract and solid filter residue respectively. (2) Adjust the pH of the obtained extract to 4.5, perform acid precipitation and centrifugation, let it stand, and then centrifuge to separate and collect the protein solid phase; (3) After mixing the protein solid phase with water, add sodium hydroxide to adjust the pH of the system to 12.5, react at a constant temperature for 60 min, and control the solid content of the system to be stable at 13%. Then, add 10wt% hydrochloric acid to the system and adjust the pH of the system to 7.6. Then add 5‰ of protein gluten powder, 0.2‰ of protein glutaminase PG and 1.5‰ of transglutaminase TG to the system, transfer to an enzymatic hydrolysis tank, and enzymatically hydrolyze at a constant temperature of 45℃ for 30 min to obtain a neutralized enzymatic hydrolysate; (4) The neutralized enzymatic hydrolysate was sent to a flash sterilization device and sterilized at 150°C for 10 seconds. The sterilized enzymatic hydrolysate was then transferred to a flash evaporation device, and the flash evaporation temperature was controlled at 80°C. The material after flash evaporation was dried and agglomerated with 0.8 wt‰ soybean lecithin to obtain soybean protein isolate with a low beany odor and a meat-like fiber structure.

[0035] Comparative Example 1 Unlike Example 1, in step (1), the step of adding bromelain is omitted, while the other steps remain unchanged.

[0036] Comparative Example 2 Unlike Example 1, in step (3), after mixing the protein solid phase with water, the pH value was directly adjusted to 7.2 without alkali shift neutralization modification, while the other steps remained unchanged.

[0037] Comparative Example 3 Unlike Example 1, in step (3), gluten powder is replaced with an equal amount of transglutaminase TG, and protein transglutaminase PG and transglutaminase TG are used for synergistic enzymatic hydrolysis, while other steps remain unchanged.

[0038] Comparative Example 4 Unlike Example 1, in step (3), glutamine transaminase TG is replaced with an equal amount of gluten powder, and enzymatic hydrolysis is performed using gluten powder and protein glutaminase PG. Other steps remain unchanged.

[0039] Comparative Example 5 Unlike Example 1, in step (4), the flash evaporation treatment is omitted, and the sterilized enzymatic hydrolysate is directly dried. The other steps remain unchanged.

[0040] Performance testing 1. The gelation ability of soy protein isolate was determined, and the results are shown in Table 1. The specific test steps are as follows: (1) Preparation: Accurately weigh 12.0g ± 0.1g of soy protein isolate powder and pour it into 88mL ± 1mL of pre-prepared 2.5% sodium chloride solution. Stir thoroughly with a glass rod until no dry powder remains. Transfer the mixture to a Joyoung food processor (JYL-CO22E), install the cross blade, and manually stir at low speed for 5s, then continue stirring for about 30s. The total stirring time should be controlled between 65s and 70s (if the machine runs dry during stirring, stop the machine, invert it, shake it, and then continue stirring). Transfer the entire mixture to a 100mL centrifuge tube, cap it, and weigh it to balance. Place it in a low-speed centrifuge and centrifuge at 2500r / min for 5min to deaerate. After centrifugation, remove the centrifuge tube, remove the upper white floating matter, transfer the gel to a 100mL beaker, insert a straight steel spoon between the beaker wall and the gel, rotate it in the same direction at a uniform speed to remove air bubbles, ensure that there are no air bubbles inside the gel and that the color is uniform, and smooth the front of the gel with the straight steel spoon.

[0041] (2) Heating and cooling of the gel: Cover the beaker with a lid or watch glass to prevent water droplets from falling in during the water bath. Place the beaker in a water bath at 80℃±1℃ (the water level should cover the gel in the beaker) and heat at a constant temperature for 30 minutes. After heating, remove the beaker, remove the watch glass, and immediately place it in cold water at 18℃~20℃ to cool for 30 minutes. After cooling, use the handle of a straight steel spoon to gently rotate along the beaker wall to completely separate the gel from the beaker wall (avoid damaging the gel skin to prevent a severely low subsequent pressure value). Remove the gel intact and place it on a clean plate for measurement.

[0042] (3) Gel property testing: The gel after demolding was tested using a property testing instrument. The instrument parameters were set as follows: calibration height 50 mm, pre-test speed 2.0 mm / s, test speed 1.0 mm / s, post-test speed 10.0 mm / s, pressure distance 25.00 mm, probe type P / 0.5R (or P / 0.5), trigger force 5.0 g. During the test, the peak gel strength, rupture distance, and work done by the gel rupture force were recorded.

[0043] (4) Data processing and recording: Repeat the test 6 times for each parallel group, record the test results, and calculate the mean and standard deviation of each data.

[0044] Table 1. Results of gel performance tests

[0045] As shown in Table 1, the overall gel performance of Examples 1-3 was significantly better than that of Comparative Examples 1-5, with Example 2 exhibiting the best performance. Comparative Example 1, by omitting the extraction step involving the addition of bromelain, could not directionally degrade lipoxygenase and hydrophobic odor-causing peptides. Consequently, the protein molecules did not undergo adequate enzymatic depolymerization, resulting in insufficient subsequent cross-linking sites, leading to a loose protein network structure and reduced rupture strength and gel area.

[0046] Comparative Example 2, due to the lack of alkali shift neutralization modification, did not undergo stretching denaturation of protein molecules under high pH conditions. The disulfide bonds and hydrophobic groups inside the molecules were not fully exposed, and the gluten powder and enzyme preparation could not effectively participate in the cross-linking reaction. The binding force between protein molecules decreased significantly, resulting in a reduction in the final breaking strength and gel area, and a significant decrease in the water-holding capacity of the colloid.

[0047] Comparative Example 3 replaced the gluten powder with additional transglutaminase TG. Lacking the glutamine and lysine active groups provided by the gluten powder, the soybean protein itself could not form a dense three-dimensional network structure by relying solely on its own cross-linking sites. The enzymatic modification direction was deviated, and the final breaking strength and gel area were reduced.

[0048] Comparative Example 4 omitted the addition of transglutaminase TG and only used gluten powder and protein glutaminase PG for treatment. It could not form a covalently cross-linked complex protein network. The protein aggregates had weak binding force, were easy to break when drawn into fibers, and had reduced tensile strength, breaking distance and rehydration rate.

[0049] Comparative Example 5 omitted the flash evaporation step. The enzymatic hydrolysate after sterilization did not undergo the process of removing volatile components. Although the residue of small molecule odor substances did not directly affect the mechanical properties of the gel, the protein molecules did not undergo rapid cooling and component adjustment after high-temperature sterilization. This resulted in partial irreversible aggregation of the protein conformation, leading to a decrease in gel uniformity, tear strength, and gel area.

[0050] 2. The toughness and rehydration properties of textured protein were tested. The results are shown in Table 2. The specific test steps are as follows: Textured soy protein was prepared mainly from soy protein isolate, gluten, soybean meal and starch, and its quality was determined.

[0051] (1) Raw material compounding and mixing: Weigh 30% soy protein isolate, 20% wheat gluten, 40% soybean meal and 10% starch by mass percentage, and put them into a large mixer. Mix them thoroughly for 15 minutes to ensure that the materials are mixed evenly and without lumps.

[0052] (2) Twin-screw extrusion puffing: The well-mixed raw materials are fed into the twin-screw extruder, the temperature control system is started, and the temperature control parameters of the extruder zones one to five are set to 80℃, 190℃, 170℃, 130℃ and 120℃ respectively. After the temperature of each zone stabilizes to the set value, the water injection system is turned on (the water injection frequency is set to 17Hz) to condition the material, and the extruder is turned on for continuous extrusion puffing.

[0053] (3) Cutting and shaping: Pay close attention to the discharge port of the twin-screw extruder. After the extruded material is full and stable, and the expansion is uniform and without abnormalities, pull the extruded continuous strip of textured protein into the cutting machine and cut it into the appropriate length according to the required specifications to obtain the finished textured protein product.

[0054] (4) Determination of tensile toughness of textured protein: Cut the prepared textured protein sample into rectangular strips (or dumbbell shape, recommended length 80 mm, width 10 mm, thickness 5 mm) with uniform cross-sectional area along the fiber direction. Using the dedicated tensile testing fixture of the texture analyzer (such as a spiral or pneumatic clamp), align the two ends of the strip sample and clamp it tightly between the upper and lower clamps to ensure that the sample does not slip during the stretching process and that the force direction is parallel to the fiber. Set the texture analyzer test parameters: pre-test speed 5 mm / s, mid-test speed 1.0 mm / s, post-test speed 10 mm / s, trigger force 5.0 g. Start the instrument and stretch upwards at a constant speed until the sample breaks. The instrument automatically records the maximum tensile force (N) and the maximum tensile deformation distance (mm) at the time of breakage. Divide the maximum tensile force by the initial cross-sectional area of ​​the sample to calculate the tensile strength (MPa) of the textured protein, which is used as the core indicator for measuring its toughness. Perform 6 parallel tests on each group of samples, and take the average value and standard deviation to accurately evaluate the tensile toughness of the textured protein.

[0055] (5) Determination of the rehydration rate of textured protein: Accurately weigh 10.0 g of the prepared dry textured protein sample (denoted as W0), place it in a beaker containing sufficient room temperature water, and let it stand at room temperature for 30 min, ensuring that the sample is completely soaked and has no white or hard core inside. After soaking, remove the sample and transfer it to a bag centrifuge at 2000 r / min for 20 s to dehydrate. Remove the centrifuged sample and immediately weigh its wet weight (denoted as W1). The rehydration rate of textured protein is calculated according to the ratio of wet weight to dry weight, using the formula: Rehydration rate = W1 / W0 × 100%. Six parallel determinations were performed for each group of samples, and the average value and standard deviation were calculated to evaluate the rehydration performance of the samples.

[0056] Table 2. Results of tensile toughness and rehydration rate tests

[0057] As shown in Table 2, the overall textured protein performance of Examples 1-3 was significantly better than that of Comparative Examples 1-5, with Example 2 exhibiting the best performance. Comparative Example 1, by omitting the extraction step with added bromelain, could not directionally degrade lipoxygenase and hydrophobic odor-causing peptides. Consequently, the protein molecules did not undergo adequate enzymatic depolymerization, resulting in insufficient subsequent cross-linking sites, a loose protein network structure, and reduced tensile strength, rupture distance, and rehydration rate.

[0058] Comparative Example 2, due to the lack of alkali shift neutralization modification, did not undergo stretching denaturation in a high pH environment. The disulfide bonds and hydrophobic groups inside the molecules were not fully exposed, and the gluten powder and enzyme preparation could not effectively participate in the cross-linking reaction. The binding force between protein molecules decreased significantly, and when bound to water, it could not lock in moisture through the high-strength network structure. Ultimately, both toughness and water-holding capacity decreased significantly.

[0059] Comparative Example 3 replaced the gluten powder with additional transglutaminase TG. Lacking the glutamine and lysine active groups provided by the gluten powder, the soybean protein itself could not form a dense three-dimensional network structure by relying solely on its own cross-linking sites. The enzymatic modification direction was deviated, resulting in reduced tensile strength, breaking distance, and rehydration rate.

[0060] Comparative Example 4 omitted the addition of transglutaminase TG and only used gluten powder and protein glutaminase PG for treatment. It could not form a covalently cross-linked complex protein network. The protein aggregates had weak binding force, were easy to break when drawn into fibers, and their tensile strength, breaking distance and rehydration rate were reduced.

[0061] Comparative Example 5 omitted the flash evaporation step, and the enzymatic hydrolysate after sterilization did not undergo the process of removing volatile components. The protein molecules did not undergo rapid cooling and component adjustment after high-temperature sterilization, resulting in partial irreversible aggregation of protein conformation. This led to a decrease in the uniformity of the fibrous protein network, as well as a reduction in tensile strength, breaking distance, and rehydration rate.

[0062] 3. Plant-based meat assay The basic composition of plant-based meat is shown in Table 3, and the sensory evaluation criteria for plant-based meat are shown in Table 4. Blind sample sensory evaluation analysis was conducted on the plant-based meats prepared using Examples 1-3 and Comparative Examples 1-5 by 15 sensory evaluators. The final scores of the analysis results are shown in Table 5 below.

[0063] Table 3 Basic Recipe for Plant-Based Meat

[0064] Table 4 Sensory Evaluation Criteria for Plant-Based Meat

[0065] Table 5 Sensory evaluation results of plant-based meat

[0066] As shown in Table 5, Example 2 has the best performance. In Comparative Example 1, the addition of bromelain was omitted in step (1) for extraction, which resulted in the inability to perform targeted enzymatic hydrolysis of the protein. Consequently, the enzymatic hydrolysis products for the flavor of the subsequent product were insufficient, ultimately leading to a decrease in the flavor and aroma scores of the product.

[0067] In Comparative Example 2, the obtained extract was adjusted to pH 6 and subjected to acid precipitation and centrifugation in step (2). This resulted in the overall protein molecules not denaturing under high pH conditions, leading to a decrease in the binding force between protein molecules and the inability to form a strong network structure. Ultimately, this resulted in a decrease in tissue morphology and chewing texture, and a reduction in overall acceptability. In Comparative Example 3, a single transglutaminase (TG) was used for enzymatic hydrolysis in step (3), which altered the direction and target of the enzymatic modification. The lack of gluten powder prevented the formation of a strong gel-like texture, ultimately resulting in a decrease in tissue morphology and chewing texture, and a reduction in overall acceptability.

[0068] Comparative Example 4 used only gluten powder in step (3), which could not form an enzymatic modification and did not obtain a complete reaction system. In the end, it could not obtain a product with strong gelation and specific texture, resulting in a decrease in tissue morphology and chewing texture, and a decrease in overall acceptability.

[0069] In Comparative Example 5, the flash evaporation process was omitted in step (4), and the sterilized enzymatic hydrolysate was directly dried. As a result, the liquid did not pass through the flash evaporation section, and the beany substances could not be removed by the rapid evaporation of water, which ultimately reduced the flavor and aroma scores of the product.

[0070] In summary, this invention achieves the effect of low beany odor in the finished product and high imitation meat fiber structure after extrusion through multi-process collaboration, thus overcoming the shortcomings of existing technologies that only process in a single stage and cannot simultaneously achieve multiple performance characteristics.

[0071] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing a soy protein isolate with low beany odor and a highly meat-fiber-like structure, characterized in that, The process includes the following steps: mixing low-temperature defatted soybean meal with water, adding bromelain for extraction, and then separating the extract and solid residue through solid-liquid separation. The pH of the extract was adjusted to acidic for acid precipitation. After standing, the extract was centrifuged and the protein solid phase was collected. After mixing the protein solid phase with water, sodium hydroxide was added to adjust the pH of the system to alkaline and the reaction was carried out; then, hydrochloric acid was added to adjust the pH of the system to neutral; then gluten powder, protein glutaminase, and transglutaminase were added to the system and enzymatic hydrolysis was carried out to obtain a neutralized enzymatic hydrolysate. The neutralized enzymatic hydrolysate was subjected to sterilization, flash evaporation and drying in sequence to obtain a solid powder; soybean lecithin was agglomerated onto the solid powder to obtain soy protein isolate with a low beany odor and a meat-fiber-like structure.

2. The method for preparing soy protein isolate with low beany odor and highly simulated meat fiber structure as described in claim 1, characterized in that, The mass ratio of the low-temperature defatted soybean meal to water is 1:(8-10); the amount of bromelain added is 0.01-0.2% of the mass of the low-temperature defatted soybean meal.

3. The method for preparing soy protein isolate with low beany odor and highly simulated meat fiber structure as described in claim 1, characterized in that, The extraction temperature for bromelain is 50-58℃, the pH value is 6.8-7.8, and the extraction time is 30-45 min.

4. The method for preparing soy protein isolate with low beany odor and highly simulated meat fiber structure as described in claim 1, characterized in that, The pH for acid precipitation is 4.5-4.7; The pH of the system is adjusted to 9.5-12.5 using sodium hydroxide. Hydrochloric acid was used to adjust the pH of the system to 7.0-7.

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5. The method for preparing soy protein isolate with low beany odor and highly simulated meat fiber structure as described in claim 1, characterized in that, After adding sodium hydroxide to adjust the pH of the system to alkaline, the solid content of the system is 7-13%, and the reaction time is 30-60 minutes.

6. The method for preparing soy protein isolate with low beany odor and highly simulated meat fiber structure as described in claim 1, characterized in that, The amount of added gluten powder is 0.5-5‰ of the protein solid phase mass; the amount of added protein glutaminase is 0.1-0.5‰ of the protein solid phase mass, and the amount of added glutamine transaminase is 0.5-1.5‰ of the protein solid phase mass.

7. The method for preparing soy protein isolate with low beany odor and highly simulated meat fiber structure as described in claim 1, characterized in that, The enzymatic hydrolysis reaction is carried out at a temperature of 40-60℃ for 20-40 minutes.

8. The method for preparing soy protein isolate with low beany odor and highly simulated meat fiber structure as described in claim 1, characterized in that, The sterilization temperature is 145-150℃, and the time is 10-15 seconds.

9. The method for preparing soy protein isolate with low beany odor and highly simulated meat fiber structure as described in claim 1, characterized in that, The flash evaporation temperature is 70-80℃.

10. A soy protein isolate with a low beany odor and a high meat fiber structure prepared by the method of preparing soy protein isolate with a low beany odor and a high meat fiber structure as described in any one of claims 1-9.

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