Method for improving functional characteristics of walnut protein based on L-arginine combined acoustic resonance technology and application

Abstract

The invention discloses a method for improving functional characteristics of walnut protein based on L-arginine combined acoustic resonance technology and application, and belongs to the technical field of plant protein modification processing. The invention discloses a method for improving functional characteristics of walnut protein based on L-arginine (L-Arg) combined with an acoustic resonance technology. The method comprises the following steps: preparing a walnut protein suspension; adding L-Arg into the walnut protein suspension, and then carrying out acoustic resonance treatment; and performing vacuum freeze drying on the treated walnut protein suspension to obtain modified walnut protein powder. In order to solve the problems that walnut protein is low in solubility and poor in functional characteristic, the walnut protein is treated through an L-Arg combined acoustic resonance technology, so that the solubility, emulsibility, water holding capacity, oil holding capacity and foamability of the walnut protein are improved, the walnut protein can meet food processing requirements, and the application value of the walnut protein in the food industry is improved.

Description

Technical Field

[0001] The invention belongs to the technical field of plant protein improvement, and particularly relates to a method and application of improving the functional properties of walnut protein based on L-arginine combined with acoustic resonance technology. Background Art

[0002] With the rapid development of society and the significant improvement in people's living standards, healthy eating has become a core issue in modern society. Consumers are increasingly demanding healthy foods, particularly those rich in high-quality protein. Compared to animal proteins, plant proteins are increasingly becoming a preferred choice for healthy eating due to their rapid digestion and absorption, high bioavailability, and low fat and cholesterol content. Walnut protein, a leading plant protein, exhibits significant advantages in the food industry, including a comprehensive amino acid profile, a balanced composition, and high nutritional value. Despite its numerous advantages, walnut protein faces numerous challenges in its practical application. Among these, low solubility and poor functional properties are the main factors limiting its widespread use in the food industry. These deficiencies not only affect walnut protein's processing performance and product quality, but also hinder its development in functional foods and nutritional supplements. Therefore, how to effectively improve the solubility and functional properties of walnut protein has become a key issue currently under investigation in food science.

[0003] In order to overcome the application bottleneck of walnut protein, researchers are constantly exploring various methods for modifying plant proteins. Currently, the main modification methods include physical modification, chemical modification, and enzymatic modification. Among them, physical modification has attracted much attention due to its advantages such as fast speed and high safety. Acoustic resonance technology, as a new physical modification method that has emerged in recent years, generates high-intensity vibrations through the resonance of a mechanical vibration system, so that the material is excited by low-frequency, high-acceleration acoustic waves in a multiphase flow to achieve the purpose of uniform dispersion, thereby effectively improving the functional properties of the protein. The Chinese patent with publication number CN115836706A discloses a method for improving the solubility and emulsification properties of pea protein isolate based on acoustic resonance technology. This method improves the solubility and emulsification properties of pea protein isolate by controlling the acoustic resonance treatment of pea protein isolate for different lengths. Although acoustic resonance technology has certain application potential in improving the solubility and functional properties of plant proteins, the modification effect of acoustic resonance technology alone is limited and it is difficult to meet the needs of large-scale industrial production.

[0004] L-arginine (L-Arg) is a natural, green, alkaline, small molecule with advantages such as low price and good biocompatibility. It has been widely used in the functional modification of animal proteins, but has been less studied in the modification of plant proteins. Although L-Arg has shown certain effects in inhibiting protein aggregation, improving protein solubility and functional properties in plant protein modification, its modification effect is poor, limiting its application and promotion in the field of plant protein modification. Both acoustic resonance technology and L-Arg used alone have certain advantages in improving the functional properties of plant proteins. However, in actual production and application, whether the two technologies can be used in combination, whether the combination has synergistic effects, and how to ensure the stability and repeatability of the modification process are key to whether the technology can be applied to large-scale industrial production. At present, there are no patents or literature reports on the use of L-Arg combined with acoustic resonance technology to improve the functional properties of plant proteins. Summary of the Invention

[0005] In view of the problems existing in the prior art of modifying walnut protein, such as high cost, low safety, poor modification effect, and difficulty in significantly improving the modification effect by optimizing acoustic resonance treatment parameters or L-Arg modification conditions alone, the purpose of the present invention is to provide a method and application for improving the functional properties of walnut protein based on L-arginine combined with acoustic resonance technology.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions: The present invention provides a method for improving the functional properties of walnut protein based on L-Arg combined with acoustic resonance technology, comprising the following steps: Step 1, adding L-Arg to the walnut protein suspension, and mixing by magnetic stirring to obtain a mixed solution; Step 2, subjecting the mixed solution to an acoustic resonance treatment to obtain an acoustic resonance treated mixed solution; Step 3: vacuum freeze-drying the mixed solution after the acoustic resonance treatment to obtain modified walnut protein.

[0007] In step 1, the solvent used for the walnut protein suspension is any one of water, buffer solution or physiological saline.

[0008] The concentration of the walnut protein suspension is 50 mg / mL.

[0009] The L-Arg accounts for 0.15% to 0.35% by volume of the walnut protein suspension.

[0010] In step 2, the acoustic resonance temperature is 15° C. to 25° C., the acoustic resonance frequency is 60 Hz to 65 Hz, the amplitude is 30% to 40%, the acceleration is 60 g to 80 g, and the acoustic resonance treatment time is 10 min to 30 min.

[0011] In step 3, the vacuum freeze drying pre-freezing temperature is -75°C to -80°C, and the vacuum freeze drying time is 36h to 48h.

[0012] The present invention provides modified walnut protein obtained by the method for improving the functional properties of walnut protein based on L-Arg combined with acoustic resonance technology.

[0013] The solubility of the modified walnut protein is greater than 60%, and the emulsification activity is greater than 14 m 2 / g, water holding capacity>7%, oil holding capacity>7%, foaming capacity>50%.

[0014] The present invention provides application of the modified walnut protein in preparing functional foods.

[0015] The above method for improving the functional properties of walnut protein based on L-Arg combined with acoustic resonance technology is applied to improving the functional properties of plant protein, wherein the plant protein is any one or a combination of soy protein, pea protein and rice protein.

[0016] Compared with the prior art, the present invention has the following beneficial effects: The present invention provides a method for improving the functional properties of walnut protein using L-Arg combined with acoustic resonance technology. Through the synergistic effect of L-Arg addition and acoustic resonance technology, the solubility and other functional properties of walnut protein are significantly enhanced. L-Arg, a naturally alkaline amino acid, not only helps improve the dispersibility of walnut protein in solution but also improves its solubility and interfacial activity through its specific chemical properties. Acoustic resonance technology utilizes high-intensity vibrations generated by a mechanical vibration system to uniformly disperse the walnut protein under low-frequency, high-acceleration acoustic excitation. This physical effect effectively disrupts the protein's aggregated structure, thereby improving its spatial conformation and functional properties. Through the combined treatment of L-Arg and acoustic resonance, the solubility, emulsification, water-holding capacity, oil-holding capacity, and foaming properties of walnut protein are significantly improved. This synergistic effect is significantly superior to that achieved using acoustic resonance or L-Arg alone, demonstrating the unique advantages of L-Arg combined with acoustic resonance technology in improving the functional properties of walnut protein. This method is expected to be applied in the food industry to enhance the application value of high-quality plant proteins.

[0017] Furthermore, when the addition amount of L-Arg is 0.25%, the two synergistically improve the solubility, emulsification, water retention, oil retention and foaming properties of walnut protein to the best effect.

[0018] The modified walnut protein of the present invention has higher solubility, emulsification, water holding capacity and foaming property, indicating that the modified walnut protein has broad application prospects in the fields of food, health care products and the like.

[0019] The method provided by the present invention is not only applicable to walnut protein, but can also be extended to the modification of other plant proteins, and has broad application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 The effects of different addition amounts of L-Arg combined with acoustic resonance technology on the solubility of walnut protein in Comparative Example 1, Comparative Example 2, Comparative Example 3 and Examples 1-5 of the present invention are shown; Figure 2 The effects of different addition amounts of L-Arg combined with acoustic resonance technology on the emulsifying activity and emulsification stability of walnut protein in Comparative Example 1, Comparative Example 2, Comparative Example 3 and Examples 1-5 of the present invention are shown; Figure 3 The effects of different addition amounts of L-Arg combined with acoustic resonance technology on the water holding capacity of walnut protein in Comparative Example 1, Comparative Example 2, Comparative Example 3 and Examples 1-5 of the present invention are shown; Figure 4 The effects of different addition amounts of L-Arg combined with acoustic resonance technology on the oil retention of walnut protein in Comparative Example 1, Comparative Example 2, Comparative Example 3 and Examples 1-5 of the present invention are shown; Figure 5 The effects of different addition amounts of L-Arg combined with acoustic resonance technology on the foaming property and foaming stability of walnut protein in Comparative Example 1, Comparative Example 2, Comparative Example 3 and Examples 1-5 of the present invention are shown; in, Figures 1 to 5 Comparative Example 1 is untreated walnut protein, Comparative Example 2 is walnut protein treated with only 0.25% L-Arg, and Comparative Example 3 is walnut protein treated with acoustic resonance alone. Different lowercase letters (a-g) on the bar graph indicate significant differences between the groups ( P <0.05). DETAILED DESCRIPTION

[0021] To facilitate understanding of the features and effects of the present invention by those skilled in the art, the following provides a general description and definition of the terms and expressions used in the specification and claims. Unless otherwise indicated, all technical and scientific terms used herein have the ordinary meanings as understood by those skilled in the art regarding the present invention. In the event of conflict, the definitions in this specification shall prevail.

[0022] Below in conjunction with specific embodiment, further set forth the present invention.Should be understood that these embodiments are only used to illustrate the present invention and are not used in limiting the scope of the present invention.In addition, should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms fall equally within the scope limited by the appended claims of the application.

[0023] The following examples utilize conventional instruments and equipment in the art. Experimental methods in the following examples, where specific conditions are not specified, were generally performed under conventional conditions or as recommended by the manufacturer. The various raw materials used in the following examples, unless otherwise specified, were conventional commercially available products, with specifications conventional in the art.

[0024] The present invention provides a method for improving the functional properties of walnut protein based on L-Arg combined with acoustic resonance technology, the steps of which are as follows: Step 1: Prepare walnut protein into a suspension with a concentration of 50 mg / mL at 20-25°C.

[0025] Step 2: Add L-Arg to the walnut protein suspension in an amount of 0.15% to 0.35%.

[0026] Step 3: After adding L-Arg to the walnut protein suspension, the mixture was magnetically stirred for 2 h and then placed in a refrigerator at 4°C overnight.

[0027] Step 4: subjecting the walnut protein suspension containing L-Arg to an acoustic resonance treatment and then to vacuum freeze-drying, specifically comprising the following steps: Step 4-1: Take 40 mL of the walnut protein suspension containing L-Arg and place it in an acoustic resonance glass sample jar with a capacity of 100 mL.

[0028] Step 4-2: Under the condition of 20-25°C, set the operating parameters and start the acoustic resonance instrument to perform acoustic resonance treatment on the sample; the operating parameters of the acoustic resonance instrument are: frequency 62 Hz, amplitude 30%-40%, acceleration 70 g, and treatment time 20 min.

[0029] Step 4-3: After the acoustic resonance treatment is completed, the walnut protein suspension is collected.

[0030] Step 4-4: Pre-freeze the collected walnut protein suspension at -70~-80°C and then place it in a vacuum freeze dryer for 36~48 hours.

[0031] In addition to the above steps, the specific implementation also includes step 4: analyzing the functional properties of the modified walnut protein samples in terms of solubility, emulsification, water retention, oil retention, and foaming. 1. Specific embodiments Example 1 This embodiment provides a method for improving the functional properties of walnut protein based on L-Arg combined with acoustic resonance technology, comprising the following steps: Walnut protein was prepared into a suspension with a concentration of 50 mg / mL at 25°C.

[0033] L-Arg was added to the above walnut protein suspension at an addition amount of 0.15% (mass / volume), magnetically stirred for 2 h, and then placed in a refrigerator at 4°C overnight.

[0034] 40 mL of walnut protein suspension containing 0.15% L-Arg was placed in a 100 mL acoustic resonance glass sample jar. The acoustic resonance instrument was started at 25°C after setting the operating parameters. The operating parameters of the acoustic resonance instrument were: frequency 62 Hz, amplitude 40%, acceleration 70 g, and treatment time 20 min.

[0035] After the acoustic resonance treatment, the walnut protein sample suspension was collected and pre-frozen at -80°C, and then placed in a vacuum freeze dryer for 48 h to obtain modified walnut protein powder.

[0036] Example 2 This embodiment provides a method for improving the functional properties of walnut protein based on L-Arg combined with acoustic resonance technology, comprising the following steps: Walnut protein was prepared into a suspension with a concentration of 50 mg / mL at 25°C.

[0037] L-Arg was added to the above walnut protein suspension at an addition amount of 0.2% (mass / volume), magnetically stirred for 2 h, and placed in a refrigerator at 4°C overnight.

[0038] A 40 mL suspension of walnut protein containing 0.2% L-Arg was placed in a 100 mL acoustic resonance glass sample jar. The acoustic resonance instrument was started at 25°C after setting the operating parameters. The operating parameters of the acoustic resonance instrument were: frequency 62 Hz, amplitude 40%, acceleration 70 g, and treatment time 20 min.

[0039] After the acoustic resonance treatment, the walnut protein sample suspension was collected, pre-frozen at -80°C, and then dried in a vacuum freeze dryer for 48 h to obtain modified walnut protein powder.

[0040] Example 3 This embodiment provides a method for improving the functional properties of walnut protein based on L-Arg combined with acoustic resonance technology, comprising the following steps: Walnut protein was prepared into a suspension with a concentration of 50 mg / mL at 25°C.

[0041] L-Arg was added to the above walnut protein suspension at an amount of 0.25% (mass / volume), magnetically stirred for 2 h, and placed in a refrigerator at 4°C overnight.

[0042] A 40 mL suspension of walnut protein containing 0.25% L-Arg was placed in a 100 mL acoustic resonance glass sample jar. The acoustic resonance instrument was started at 25°C after setting the operating parameters. The operating parameters of the acoustic resonance instrument were: frequency 62 Hz, amplitude 40%, acceleration 70 g, and treatment time 20 min.

[0043] After the acoustic resonance treatment, the walnut protein sample suspension was collected and pre-frozen at -80°C, and then placed in a vacuum freeze dryer for 48 h to obtain modified walnut protein powder.

[0044] Example 4 This embodiment provides a method for improving the functional properties of walnut protein based on L-Arg combined with acoustic resonance technology, comprising the following steps: Walnut protein was prepared into a suspension with a concentration of 50 mg / mL at 25°C.

[0045] L-Arg was added to the above walnut protein suspension at an addition amount of 0.3% (mass / volume), magnetically stirred for 2 h, and then placed in a refrigerator at 4°C overnight.

[0046] A 40 mL suspension of walnut protein containing 0.3% L-Arg was placed in a 100 mL acoustic resonance glass sample jar. The acoustic resonance instrument was started at 25°C after setting the operating parameters. The operating parameters of the acoustic resonance instrument were: frequency 62 Hz, amplitude 40%, acceleration 70 g, and treatment time 20 min.

[0047] After the acoustic resonance treatment, the walnut protein sample suspension was collected and pre-frozen at -80°C, and then placed in a vacuum freeze dryer for 48 h to obtain modified walnut protein powder.

[0048] Example 5 This embodiment provides a method for improving the functional properties of walnut protein based on different addition amounts of L-Arg combined with acoustic resonance technology, comprising the following steps: Walnut protein was prepared into a suspension with a concentration of 50 mg / mL at 25°C.

[0049] L-Arg was added to the above walnut protein suspension at an amount of 0.35% (mass / volume), magnetically stirred for 2 h, and then placed in a refrigerator at 4°C overnight.

[0050] Take 40 mL of the walnut protein suspension containing 0.35% L-Arg and place it in a 100 mL acoustic resonance glass sample jar. At 25°C, set the operating parameters and start the acoustic resonance instrument to perform acoustic resonance treatment on the sample; wherein the operating parameters of the acoustic resonance instrument are: frequency 62 Hz, amplitude 40%, acceleration 70 g, and treatment time 20 min.

[0051] After the acoustic resonance treatment, the walnut protein sample suspension was collected and pre-frozen at -80°C, and then placed in a vacuum freeze dryer for 48 h to obtain modified walnut protein powder.

[0052] Comparative Example 1 A control method for improving the functional properties of walnut protein based on L-Arg combined with acoustic resonance technology is provided, comprising the following steps: Walnut protein was prepared into a 50 mg / mL suspension at 25°C. No L-Arg was added to the walnut protein suspension, and no acoustic resonance treatment was performed. This suspension, designated as control 1, was magnetically stirred for 2 hours, placed in a 4°C refrigerator overnight, pre-frozen at -80°C, and dried in a vacuum freeze dryer for 48 hours to obtain control 1 walnut protein powder.

[0053] Comparative Example 2 A control method for improving the functional properties of walnut protein based on L-Arg combined with acoustic resonance technology is provided, comprising the following steps: Walnut protein was prepared into a 50 mg / mL suspension at 25°C. Only L-Arg was added to the walnut protein suspension at a concentration of 0.25% (mass / volume), without acoustic resonance treatment. This suspension, designated as control 2, was magnetically stirred for 2 hours, placed in a 4°C refrigerator overnight, pre-frozen at -80°C, and dried in a vacuum freeze dryer for 48 hours to obtain control 2 walnut protein powder.

[0054] Comparative Example 3 Provided is a control method for improving the functional properties of walnut protein based on L-Arg combined with acoustic resonance technology, comprising the following steps: Walnut protein was prepared into a 50 mg / mL suspension at 25°C. L-Arg was not added to the walnut protein suspension, which was treated with acoustic resonance alone. This suspension, designated as control 3, was magnetically stirred for 2 hours and then placed in a 4°C refrigerator overnight.

[0055] 40 mL of the above walnut protein suspension was placed in a 100 mL acoustic resonance glass sample jar. The acoustic resonance instrument was started at 25°C after setting the operating parameters to perform acoustic resonance treatment on the sample. The operating parameters of the acoustic resonance instrument were: frequency 62 Hz, amplitude 40%, acceleration 70 g, and treatment time 20 min.

[0056] After the acoustic resonance treatment, the walnut protein sample suspension was collected and pre-frozen at -80°C, and then placed in a vacuum freeze dryer for 48 h to obtain control 3 walnut protein powder.

[0057] 2. Performance Testing 1. Determination of walnut protein solubility Accurately weigh 100 mg of modified walnut protein and disperse it in deionized water to prepare a sample solution with a concentration of 4 mg / mL. After magnetic stirring for 1 h at room temperature, centrifuge at 4000 r / min for 20 min, take 1 mL of the supernatant and add it to 4 mL of biuret reagent, mix well, react at 37°C for 30 min, and measure the absorbance at a wavelength of 540 nm using a UV-visible spectrophotometer. The measured absorbance value is substituted into the drawn standard curve (y = 0.0854x - 0.0053, R 2 =0.9979), calculate the soluble protein content. The total protein content was determined by the Kjeldahl method. The formula for calculating the solubility of walnut protein is as follows:

[0058] 2. Determination of walnut protein emulsification properties A walnut protein suspension was prepared in deionized water at a concentration of 2 mg / mL. The suspension was magnetically stirred for 1 hour to fully dissolve the protein. 3 mL of food-grade soybean oil was added to 9 mL of the walnut protein suspension and homogenized using a high-speed shear dispersing emulsifier for 3 minutes. Immediately, 50 μL was removed from the bottom of the sample and added to 5 mL of SDS (0.1%, w / v) solution. The sample was vortexed for 5 seconds and the absorbance at 500 nm was measured using a UV-visible spectrophotometer. The sample was allowed to stand at room temperature for 10 minutes before being sampled again for measurement. The emulsifying activity (EAI) and emulsion stability (ESI) of walnut protein were calculated using the following formulas:

[0059]

[0060] Where: DF is the dilution factor (100); c is the sample concentration (g / mL); φ is the dispersion coefficient of the oil phase in the emulsion (0.25); A0 and A 10 are the absorbance values of the sample at 0 min and 10 min, respectively.

[0061] 3. Determination of water holding capacity of walnut protein Weigh 0.2 g of walnut protein sample and disperse it in 4 mL of deionized water. Mix thoroughly, let it stand for 30 min, and then centrifuge it at 4000 rpm for 15 min. Remove the supernatant and weigh it. Calculate the water holding capacity of the walnut protein using the following formula:

[0062] Wherein: M is the mass of the walnut protein sample, g; M1 is the total mass of the centrifuge tube and sediment, g; M2 is the total mass of the centrifuge tube and sample, g.

[0063] 4. Determination of oil holding capacity of walnut protein Accurately weigh 0.2 g of protein sample into a centrifuge tube and record the total mass of the sample and centrifuge tube at this time, recorded as M3 (g). Add 4 mL of soybean oil to the centrifuge tube, vortex and shake, let it stand for 1 hour, centrifuge at 4000 r / min for 15 minutes, remove the supernatant, and weigh the total mass of the centrifuge tube and the remaining sample at this time, recorded as M4 (g). The formula for calculating the oil retention of walnut protein is as follows:

[0064] 5. Determination of foaming properties and foaming stability of walnut protein A walnut protein suspension was prepared at a concentration of 5 mg / mL. After magnetic stirring for 1 hour, 25 mL of the solution was homogenized at 16,000 r / min for 2 minutes. The volume of the sample at this time was recorded as V1 (mL). After standing for 10 minutes, the volume of the sample was recorded again as V2 (mL). The foaming property and foam stability of walnut protein were calculated as follows:

[0065]

[0066] Solubility is one of the important functional properties of proteins and is a key physical and chemical property that affects protein functional properties and determines protein applications. Figure 1As shown, the solubility of walnut protein was improved after treatment with either 0.25% L-Arg (Control 2) or acoustic resonance (Control 3), with acoustic resonance treatment being more effective than L-Arg in improving walnut protein solubility. The guanidine group in the L-Arg molecule may interact with polar amino acids or negatively charged regions of the protein, thereby enhancing the solubility of walnut protein. Acoustic resonance, on the other hand, may alter non-covalent interactions within the protein, such as hydrogen bonds and hydrophobic interactions, causing the protein molecules to shift from a compact state to a more loose state, thereby increasing the protein's surface hydrophilicity. Furthermore, the macroscopic vibrations and microscopic acoustic-fluidic coupling generated during acoustic resonance treatment can break up protein aggregation, reduce the size of protein particles, increase surface area, and promote interaction between the protein and the solvent. When walnut protein was treated with L-Arg combined with acoustic resonance, the solubility of walnut protein was significantly improved, and when the L-Arg addition amount was 0.25%, the solubility of walnut protein reached the maximum (68.43%), which was 39.94% higher than the control 1, 35.69% higher than the control 2, and 23.13% higher than the control 3, indicating that the combined treatment of the two was synergistic in improving the solubility of walnut protein.

[0067] Emulsifying ability is an important functional property of protein. The emulsifying ability of protein is usually measured by emulsifying activity (EAI) and emulsion stability (ESI). EAI reflects the ability of protein to form emulsions, while ESI refers to the ability of emulsions to resist stratification or flocculation. Figure 2 It can be seen that compared with the control group 1, the emulsification of walnut protein treated with only 0.25% L-Arg (control 2) increased by 61.92%, and the emulsification stability increased by 3.69%. This may be because L-Arg promotes the partial unfolding or unfolding of the protein molecular structure, exposing more hydrophobic areas, and promoting the formation of a stable and orderly structure of the protein at the oil-water interface, thereby improving the emulsification properties of walnut protein. The emulsification of walnut protein treated with acoustic resonance alone (control 3) increased by 38.59%, and the emulsification stability increased by 3.87%. This may be because acoustic resonance increases the flexibility of protein molecules and the exposure of hydrophobic groups, which helps the protein adsorb at the oil-water interface, thereby improving the emulsification ability of the protein. When L-Arg is combined with acoustic resonance to treat walnut protein, its emulsification ability is further improved, and the emulsification can reach 17.83 m 2 / g, the emulsification stability can reach 85.26%, which is better than L-Arg (control group 2) and the group treated with acoustic resonance alone (control group 3), indicating that the two have a synergistic effect in improving the emulsification properties of walnut protein. It is worth noting that when the L-Arg addition amount is too high (0.3% and 0.35%), the cavitation effect caused by acoustic resonance may aggravate the excessive dispersion or aggregation of protein particles, affecting the emulsification and emulsification stability of walnut protein.

[0068] Water holding capacity is another important functional property of protein, which refers to the ability of protein to absorb and retain water under certain conditions. This functional property is of great significance in the food industry. Figure 3 It can be seen that compared with control group 1, the water holding capacity of walnut protein treated with 0.25% L-Arg (control group 2) and the group treated with acoustic resonance alone (control group 3) was improved. When walnut protein was treated with L-Arg combined with acoustic resonance, its water holding capacity increased significantly. This is because L-Arg increases the number of water-binding sites in walnut protein and enhances hydration, while acoustic resonance can produce a uniform shear force field, making the protein molecules more flexible and the structure loose, which promotes the exposure of internal hydrophilic groups. The combined effect of the two greatly improves the water holding capacity of walnut protein. When the L-Arg addition amount was 0.25%, the water holding capacity of walnut protein increased by 25.15% compared with control group 1, increased by 15.80% compared with the group treated with 0.25% L-Arg alone (control group 2), and increased by 18.27% compared with the group treated with acoustic resonance alone (control group 3), indicating that L-Arg and acoustic resonance treatment have a synergistic effect in improving the water holding capacity of walnut protein.

[0069] The oil-holding capacity of protein refers to the ability of protein to absorb and retain oil under certain conditions. This property is widely used in the development of emulsifiers and improvement of food texture. The oil-holding capacity of protein is affected by the structural characteristics of the protein itself and the interaction between proteins. Its interaction with lipids mainly depends on factors such as hydrophobic interaction, electrostatic interaction, protein structure and conformation. Figure 4 Compared with control group 1, the oil-holding capacity of walnut protein in the 0.25% L-Arg treatment group (control group 2) increased by 24.29%, the oil-holding capacity of walnut protein in the acoustic resonance treatment group (control group 3) increased by 22.39%, and the oil-holding capacity of walnut protein in the L-Arg combined with acoustic resonance treatment group increased by 45.54%. This may be because the addition of L-Arg partially unfolds the walnut protein structure, exposing more hydrophobic groups, while acoustic resonance enhances the flexibility of protein molecules and also promotes the exposure of hydrophobic groups. The combined effect of the two significantly improves the oil-holding capacity of walnut protein. The results indicate that L-Arg and acoustic resonance treatments have a synergistic effect in improving the oil-holding capacity of walnut protein. It is worth noting that with increasing the amount of L-Arg added, the protein may over-unfold, resulting in a weakening of the interaction between protein molecules, making it impossible to form a stable emulsion layer, resulting in a decrease in the oil-holding capacity of walnut protein.

[0070] Depend on Figure 5It can be seen that compared with control group 1, the foaming property of walnut protein increased by 25.31% and the foaming stability increased by 6.91% after treatment with 0.25% L-Arg alone (control group 2). After treatment with acoustic resonance alone (control group 3), the foaming property of walnut protein increased by 26%. When walnut protein was treated with L-Arg combined with acoustic resonance, its foaming property was significantly improved, increasing by 37.23%, 27.12%, and 20.73% compared with control groups 1, 2, and 3, respectively. This may be because the addition of L-Arg improved the solubility and flexibility of walnut protein, enhanced the diffusion and adsorption capacity of protein at the air-water interface, formed a film with excellent interfacial viscoelasticity, which is conducive to bubble formation and foam stability, and acoustic resonance can improve the solubility of walnut protein and promote the expansion of protein structure, making it exhibit strong interfacial activity. The two synergistically improved the foaming property of walnut protein. In addition, L-Arg combined with acoustic resonance treatment can also improve the foaming stability of walnut protein to a certain extent. When the L-Arg addition amount is 0.25%, the combined treatment of the two can increase the foaming stability of walnut protein to 91.35%. This may be because the combined treatment of the two can enable the protein molecules to better adsorb to the gas-liquid interface and form a more uniform and compact protein layer, making the foam more stable.

[0071] These experiments demonstrate that the L-Arg combined with acoustic resonance technology disclosed herein can improve the solubility, emulsification, water-holding capacity, oil-holding capacity, and foaming properties of walnut protein, significantly outperforming L-Arg and acoustic resonance alone. This combined L-Arg and acoustic resonance technology is expected to be applied in the food industry to enhance the value of high-quality plant proteins.

[0072] The above content is only for explaining the technical idea of the present invention and cannot be used to limit the protection scope of the present invention. Any changes made on the basis of the technical solution in accordance with the technical idea proposed by the present invention shall fall within the protection scope of the claims of the present invention.

Claims

1. A method for improving the functional properties of walnut protein based on L-Arg combined with acoustic resonance technology, characterized in that: The steps include: Step 1, adding L-Arg to the walnut protein suspension, and mixing by magnetic stirring to obtain a mixed solution; Step 2, subjecting the mixed solution to an acoustic resonance treatment to obtain an acoustic resonance treated mixed solution; Step 3: vacuum freeze-drying the mixed solution after the acoustic resonance treatment to obtain modified walnut protein.

2. The method for improving the functional properties of walnut protein based on L-Arg combined with acoustic resonance technology according to claim 1, characterized in that: In step 1, the solvent used for the walnut protein suspension is any one of distilled water, buffer solution or physiological saline.

3. The method for improving the functional properties of walnut protein based on L-Arg combined with acoustic resonance technology according to claim 2, characterized in that: The concentration of the walnut protein suspension is 50 mg / mL.

4. The method for improving the functional properties of walnut protein based on L-Arg combined with acoustic resonance technology according to claim 2, characterized in that: In step 1, the mass volume percentage of the L-Arg in the walnut protein suspension is 0.15% to 0.35%.

5. The method for improving the functional properties of walnut protein based on L-Arg combined with acoustic resonance technology according to claim 1, characterized in that: In step 2, the acoustic resonance temperature is 15° C. to 25° C., the acoustic resonance frequency is 60 Hz to 65 Hz, the amplitude is 30% to 40%, the acceleration is 60 g to 80 g, and the acoustic resonance treatment time is 10 min to 30 min.

6. The method for improving the functional properties of walnut protein based on L-Arg combined with acoustic resonance technology according to claim 1, characterized in that: In step 3, the vacuum freeze drying pre-freezing temperature is -75°C to -80°C, and the vacuum freeze drying time is 36h to 48h.

7. The modified walnut protein obtained by the method for improving the functional properties of walnut protein based on L-Arg combined with acoustic resonance technology according to any one of claims 1 to 6.

8. The modified walnut protein according to claim 7, characterized in that The solubility of the modified walnut protein is greater than 60%, and the emulsification activity is greater than 14 m 2 / g, water holding capacity>7%, oil holding capacity>7%, foaming capacity>50%.

9. Use of the modified walnut protein according to any one of claims 7 to 8 in the preparation of functional foods.

10. Application of the method for improving the functional properties of walnut protein based on L-Arg combined with acoustic resonance technology according to any one of claims 1 to 6 in improving the functional properties of plant proteins, wherein the plant protein is any one or a combination of soy protein, pea protein and rice protein.

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