阅读说明：本技术 一种提高豌豆蛋白功能性质的方法 (Method for improving functional properties of pea protein ) 是由 刘夫国 姜文 刘学波 马翠翠 闫晓佳 于 2021-09-22 设计创作，主要内容包括：本发明公开了一种提高豌豆蛋白功能性质的方法,属于功能性食品加工技术领域；包括以下步骤：将豌豆蛋白和菊粉的混合溶液通过超声和pH偏移联合辅助湿热法制备豌豆蛋白-菊粉复合物,本发明的方法提高了豌豆蛋白与菊粉之间美拉德反应的接枝度,显著改善了豌豆蛋白的溶解性、乳化性、抗氧化性以及热稳定性等功能性质。(The invention discloses a method for improving functional properties of pea protein, belonging to the technical field of functional food processing; the method comprises the following steps: the pea protein-inulin compound is prepared from the mixed solution of the pea protein and the inulin by an ultrasonic and pH shift combined auxiliary wet-heat method.)

1. A method for improving the functional properties of pea proteins, comprising the steps of: and (3) preparing the pea protein-inulin compound by using a mixed aqueous solution of pea protein and inulin through an ultrasonic and pH shift combined auxiliary damp-heat method.

2. Method according to claim 1, characterized in that it comprises the following steps:

(1) dispersing pea protein and inulin in deionized water respectively, and mixing the pea protein and the inulin after completely dissolving to form a colloidal dispersion;

(2) adjusting the pH value of the colloidal dispersion obtained in the step (1) to 10.0, then carrying out ultrasonic treatment under the heating condition of a water bath, terminating the reaction, and adjusting the pH value to 7.0;

(3) and (3) purifying the solution with the pH value of 7.0 obtained in the step (2) to remove salt ions and unreacted inulin to obtain the pea protein-inulin complex.

3. The method according to claim 2, wherein in step (1), the concentration of pea protein in the colloidal dispersion is 1.0 wt% and the concentration of inulin is 0.25-1.25 wt%.

4. The method according to claim 2, wherein, in the step (2), the temperature of the heating condition of the water bath is 80 ℃.

5. The method as claimed in claim 2, wherein in step (2), the power of the ultrasonic treatment is 100-600W, and the treatment time is 20-40 min.

6. The method according to claim 2, wherein in the step (2), the reaction is terminated by lowering the temperature to 0-5 ℃.

7. The method according to claim 2, wherein in step (3), the purification is performed by dialysis.

8. The method of claim 1, wherein the functional properties include solubility, thermal stability, emulsifiability, oxidation resistance, foamability, and/or environmental stability of the prepared emulsion.

Technical Field

The invention belongs to the technical field of functional food processing, and particularly relates to a method for improving functional properties of pea protein.

Background

Pea proteins have been investigated as a substitute for animal proteins in various food categories due to their high yield, low price, balanced amino acid distribution, high lysine content and high nutritional value. Furthermore, pea proteins have various biological activities, such as antioxidant activity, lowering blood pressure, regulating intestinal flora, etc. However, the use of pea protein in food products is still limited, mainly due to its poor water solubility. In particular, it has a relatively high globulin content, whereas its isolation and extraction methods, such as alkaline extraction and acid precipitation, generally promote protein denaturation and aggregation. At the same time, poor solubility also affects other functional properties of pea protein.

The maillard reaction is the most common and important carbonylamino reaction in food products, involving the covalent attachment of the carbonyl group of a sugar to a free amino group in a protein. This reaction is an excellent method for structural modification and functional improvement of proteins and can occur naturally under controlled conditions without the addition of additional chemicals. However, the traditional Maillard reaction method often has the problems of long time consumption, low grafting degree, easy protein denaturation and aggregation and the like. Therefore, there is a need to establish new technical methods to reduce the Maillard reaction time and increase the grafting degree of the reaction, and to form glycosylation products with more enhanced functional properties.

Disclosure of Invention

The invention aims to provide a method for improving the functional properties of pea protein, which aims to solve the problems in the prior art, and the pea protein-inulin compound is prepared by the ultrasonic and pH shift combined auxiliary wet-heat method of the mixed solution of the pea protein and the inulin, so that the grafting degree of the Maillard reaction between the pea protein and the inulin is improved, and the functional properties of the pea protein, such as solubility, emulsibility, oxidation resistance, thermal stability and the like, are obviously improved.

In order to achieve the purpose, the invention provides the following scheme:

the invention provides a method for improving functional properties of pea protein, which comprises the following steps: and (3) preparing the pea protein-inulin compound by using a mixed aqueous solution of pea protein and inulin through an ultrasonic and pH shift combined auxiliary damp-heat method.

Further, the method comprises the steps of:

(1) dispersing pea protein and inulin in deionized water respectively, and mixing the pea protein and the inulin after completely dissolving to form a colloidal dispersion;

(2) adjusting the pH value of the colloidal dispersion obtained in the step (1) to 10.0, then carrying out ultrasonic treatment under the heating condition of a water bath, terminating the reaction, and adjusting the pH value to 7.0;

(3) and (3) purifying the solution with the pH value of 7.0 obtained in the step (2) to remove salt ions and unreacted inulin to obtain the pea protein-inulin complex.

Further, in step (1), the concentration of pea protein in the colloidal dispersion is 1.0 wt%, and the concentration of inulin is 0.25-1.25 wt%.

Further, in the step (2), the temperature of the heating condition of the water bath is 80 ℃.

Further, in the step (2), the power of the ultrasonic treatment is 100-600W, and the treatment time is 20-40 min.

Further, in the step (2), the reaction is terminated by reducing the temperature to 0 to 5 ℃.

Further, in the step (3), the purification is performed by dialysis.

Further, the functional properties include solubility, thermal stability, emulsifiability, oxidation resistance, foamability, and/or environmental stability of the prepared emulsion.

The invention discloses the following technical effects:

(1) sonication can provide unique conditions for the reaction through unique cavitation. The ultrasound can effectively open the closely packed structure of proteins in the aqueous solution and promote the molecular movement and the frequency of mutual collision reaction, thereby effectively promoting the reaction. pH shift is also a simple and effective way to modify the structure and enhance the functional properties of proteins by allowing the proteins to undergo partial unfolding and refolding, ultimately resulting in a different structure and improved functional properties. Strongly basic conditions increase intramolecular electrostatic interactions in polypeptide chains, leading to the formation of more structurally flexible proteins and conformational changes. The combined treatment of ultrasound and pH shift facilitates the development of pea protein molecules, provides more free amino groups and energy for the reaction, and promotes the occurrence of glycosylation reactions, so that more inulin is grafted onto pea proteins.

(2) By using the method, the grafting degree of the Maillard reaction between the pea protein and the inulin can reach 15.64 percent at most, and is improved by 2.3 times compared with the traditional wet-heat method. The incorporation of inulin can result in an effective improvement of the functional properties of pea proteins, including better water solubility, thermostability, antioxidant capacity, emulsifying and foaming properties. In particular, the pea proteins have a significantly increased solubility over a wide pH range after the glycosylation reaction, which increases their range of application in the food industry. Moreover, the hydrophilic inulin can provide good spatial stability, so that the pea protein-inulin complex is endowed with good emulsification property, and the prepared emulsion can be stable at high temperature and under the environmental pressure of salt ions and the like.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings needed in the embodiments will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings without creative efforts.

FIG. 1 is a graph showing the grafting degree and browning index of pea protein-inulin complexes prepared in examples 1 and 2 and comparative examples 1 to 3, wherein A is the effect of different ultrasonic powers on the grafting degree and browning index, B is the effect of different ultrasonic times on the grafting degree and browning index, C is the effect of different inulin concentrations on the grafting degree and browning index, and D is the grafting degree of pea protein-inulin complexes prepared in example 2 and comparative examples 1 to 3;

FIG. 2 shows the results of the solubility measurements of untreated pea protein, of the pea protein-inulin complexes prepared in example 2 and in comparative examples 1 to 3;

FIG. 3 shows the results of thermal stability measurements of untreated pea protein, pea protein-inulin physical mixture, pea protein-inulin complexes prepared in example 2 and comparative examples 1-3;

FIG. 4 shows the results of antioxidant testing of untreated pea protein, pea protein-inulin physical mixture, pea protein-inulin complexes prepared in example 2 and comparative examples 1-3;

FIG. 5 shows the results of measurements of Foaming Capacity (FC) and Foam Stability (FS) of untreated pea protein, pea protein-inulin complexes prepared in example 2 and comparative examples 1-3;

FIG. 6 shows the results of the detection of the Emulsifying Activity Index (EAI) and the Emulsifying Stability Index (ESI) of untreated pea protein, the pea protein-inulin complexes prepared in example 2 and comparative examples 1 to 3;

FIG. 7 shows the stability test results of emulsions prepared from untreated pea protein, a pea protein-inulin physical mixture, and pea protein-inulin complexes prepared in example 2 and comparative examples 1-3, respectively, under different environmental conditions, wherein A is different temperature environments, and B is different NaCl concentration environments.

Detailed Description

Reference will now be made in detail to various exemplary embodiments of the invention, the detailed description should not be construed as limiting the invention but as a more detailed description of certain aspects, features and embodiments of the invention.

It is to be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. Further, for numerical ranges in this disclosure, it is understood that each intervening value, between the upper and lower limit of that range, is also specifically disclosed. Every smaller range between any stated value or intervening value in a stated range and any other stated or intervening value in a stated range is encompassed within the invention. The upper and lower limits of these smaller ranges may independently be included or excluded in the range.

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Although only preferred methods and materials are described herein, any methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present invention. All documents mentioned in this specification are incorporated by reference herein for the purpose of disclosing and describing the methods and/or materials associated with the documents. In case of conflict with any incorporated document, the present specification will control.

It will be apparent to those skilled in the art that various modifications and variations can be made in the specific embodiments of the present disclosure without departing from the scope or spirit of the disclosure. Other embodiments will be apparent to those skilled in the art from consideration of the specification. The description and examples are intended to be illustrative only.

As used herein, the terms "comprising," "including," "having," "containing," and the like are open-ended terms that mean including, but not limited to.

Pea protein and inulin used in the following examples were purchased from Shanghai-derived leaf Biotech, Inc. and were 90% pure.

In the following examples, a pea protein-inulin physical mixture (designated Mix) was prepared: a mixed solution of pea protein and inulin, wherein the concentration of pea protein is 1 wt% and the concentration of inulin is 0.5 wt%, was prepared, and then subjected to dialysis treatment for 48 hours, and freeze-dried to obtain a physical mixture.

Example 1

1. The preparation method of the pea protein-inulin complex comprises the following steps:

(1) pea protein and inulin of different masses were accurately weighed and dispersed in deionized water, which was separately stirred overnight on a magnetic stirrer at 600rpm to ensure their complete dissolution. Equal volumes of pea protein and inulin solution were mixed together and stirred for 5h to form a colloidal dispersion, the concentration of pea protein in the mixed solution being 1 wt% and the concentration of inulin being 0.25-1.25 wt%.

(2) The pH of the mixed solution was adjusted to 10.0 with a 2M NaOH solution. Then treating the mixture in an ultrasonic cell disruptor at the power of 100-.

(3) After sonication, the sample was cooled to 5 ℃ to stop the reaction, and then the pH was adjusted back to 7.0 using 2M HCl solution. The resulting solution was dialyzed for 48h, during which time water was changed 6 times to remove salt ions and unreacted inulin. The solution was subsequently freeze-dried to obtain a pea protein-inulin complex.

2. Performing single factor experiment

A single factor experiment was performed according to table 1 to prepare a pea protein-inulin complex.

TABLE 1

Experiment of	One factor design
		Experiment A	The ultrasonic power is respectively set to be 100, 200, 300, 400, 500 and 600W
Experiment B	The ultrasonic time is respectively set to 20, 25, 30, 35 and 40min
		Experiment C	Inulin concentrations were set to 0.25%, 0.5%, 0.75%, 1%, and 1.25%, respectively

3. The detection method of the grafting degree of the glycosylated protein comprises the following steps:

80mg of an o-phthalaldehyde (OPA) reagent was dissolved in 2mL of methanol, and then mixed with 50mL of 0.1mol/L sodium tetraborate buffer (pH9.7), 5mL of a 20% (w/w) Sodium Dodecyl Sulfate (SDS) solution and 200. mu.L of beta-mercaptoethanol, and the volume was adjusted to 100mL using distilled water. During the measurement, 200. mu.L of the sample solution (5mg/mL) was added to 4mL of OPA reagent and incubated at 35 ℃ for 2 min. The absorbance value of the sample was then measured using an ultraviolet-visible spectrophotometer at 340 nm. Untreated pea protein was used as a control sample and distilled water was used as a blank. The Degree of Grafting (DG) is calculated as follows:

DG＝(Ac-As)/Ac×100％

where Ac is the absorbance of the control (untreated pea protein) and As is the absorbance of the sample.

4. The browning index detection method comprises the following steps:

a pea protein-inulin complex solution (protein concentration 10mg/mL) was prepared and its absorbance at 420nm was determined using a uv-vis spectrophotometer with distilled water as a blank.

The grafting degree and browning index of example 1 are shown in fig. 1. As shown in FIG. 1(A-C), the degree of grafting increased with increasing sonication power, sonication time and inulin concentration, reaching maximum values of 10.9%, 16.9% and 13.8% at 400W sonication power, 25min sonication time and 0.5 wt% inulin concentration, respectively. The increased grafting degree by sonication can be attributed to cavitation effects associated with high intensity ultrasound that promotes partial protein unfolding, thereby promoting the grafting reaction by exposing more reactive amino groups. As the inulin concentration increases, more inulin molecules may interact with the protein, resulting in an increase in the degree of grafting. When the sonication power and time are greater than 400W and 25min, respectively, the degree of grafting decreases, mainly because excessive sonication may lead to protein aggregation. Furthermore, above an inulin concentration of 0.5 wt%, the reduction in the degree of grafting may be due to an increase in the viscosity of the system, thereby reducing the frequency of collisions between proteins and inulin molecules.

The absorbance of the pea protein-inulin complex at 420nm is generally used to characterize the degree of maillard reaction browning, which also allows to detect the progress of the maillard reaction. As shown in FIG. 1(A-C), A420 showed a similar tendency to the degree of grafting. As the sonication power, sonication time and inulin concentration increased, A420 increased and then decreased, reaching a maximum at 400W sonication power, 25min sonication time and 0.5 wt% inulin concentration. This indicates that the highest high molecular weight melanoidins were formed between pea protein and inulin at this time, which is consistent with the results of the degree of grafting discussed above.

Example 2

(1) Pea protein and inulin were accurately weighed and dispersed in deionized water, each stirred overnight on a magnetic stirrer to ensure that they were completely dissolved. Equal volumes of pea protein and inulin solution were mixed together and stirred for 5h to form a colloidal dispersion with a pea protein concentration of 1 wt% and an inulin concentration of 0.5 wt%.

(2) The pH of the mixed solution was adjusted to 10.0 with a 2M NaOH solution. Then treated in an ultrasonic cell disruptor at 400W for 25min under 80 ℃ water bath conditions.

(3) After sonication, the samples were placed in an ice-water bath to stop the reaction, and then the pH was adjusted back to 7.0 using 2M HCl solution. The resulting solution was dialyzed for 48h, during which time water was changed 6 times to remove salt ions and unreacted inulin. The solution was then freeze-dried to give the graft product, which was designated C4.

Comparative example 1

The pea protein-inulin complex sample prepared in the same way as in example 2, except that only the water bath heating treatment, without sonication and pH shift treatment, was named C1.

Comparative example 2

The difference from example 2 is only that only pH shift and water bath heating treatment, without sonication, was performed and the sample of pea protein-inulin complex prepared was named C2.

Comparative example 3

The pea protein-inulin complex sample obtained was named C3, as in example 2, with the only difference that the ultrasound and water bath heating treatment was carried out, without pH shift treatment.

Performance detection

1. Comparing the effects of different treatments on the degree of grafting of the pea protein-inulin complex

The grafting degree test of example 2 and comparative examples 1 to 3 was carried out to compare the effect of the different treatment methods on the grafting degree of the pea protein-inulin complex, and the results are shown in FIG. 1 (D). C4 has the greatest degree of grafting, indicating that the use of both pH shift and sonication is more effective in promoting maillard reactions than either of them alone. This is mainly because sonication at a pH well above the isoelectric point of the protein more effectively promotes the development of pea protein molecules, exposing more free amino groups and thus enhancing the maillard reaction.

2. Solubility in water

Solubility detection method:

pea protein and pea protein-inulin complex solutions were prepared with a total protein concentration of 1 mg/mL. The pH of these solutions was then adjusted to 2-11 using 2M HCl or NaOH solutions. After stirring at room temperature for 2h, the sample was centrifuged at 6000rpm for 20 min. The protein concentration of the supernatant was then measured using the forskol method. The solubility was calculated according to the following formula:

solubility (%) ═ 100 × C_S/C_T

Wherein Cs is the concentration of protein in the supernatant, C_TIs the concentration of total protein in the solution.

The solubility of untreated pea protein (designated PPI), the pea protein-inulin complexes prepared in example 2 and comparative examples 1-3 was examined and the results are shown in fig. 2. The solubility of PPIs is highly pH dependent, decreasing and increasing with increasing pH, reaching a minimum around pH 4-5. This is primarily because proteins tend to aggregate near the isoelectric point. After binding with inulin, the solubility of the protein is greatly increased in the pH range of 2-11. This can be attributed to the covalent linkage of the hydrophilic inulin to the pea protein molecules, which increases the steric repulsion between them and hinders their aggregation. The solubility of C4 is best compared to other complexes, especially around the isoelectric point, mainly due to the higher degree of grafting of C4 relative to other complexes. Therefore, the ultrasonic and pH shift combined auxiliary wet-heat method can effectively improve the solubility of the pea protein.

3. Thermal stability

The detection method of the thermal stability comprises the following steps:

the thermal behavior of the sample was measured using a differential scanning calorimeter. Approximately 3.0mg of the sample was weighed into a solid aluminum pan and then sealed with an aluminum lid. Meanwhile, an empty sample pan was used as a reference. The sample was heated from 50 ℃ to 200 ℃ at a rate of 10 ℃/min and nitrogen flow rate was 50 mL/min. Differential Scanning Calorimetry (DSC) thermograms were recorded and the peak denaturation temperature (Ta) was calculated.

The heat stability tests were carried out on untreated pea protein (designated PPI), pea protein-inulin physical mixture (designated Mix), pea protein-inulin complexes prepared in example 2 and comparative examples 1-3, and the results are shown in fig. 3. The denaturation temperature of the pea protein-inulin complex (101.92-109.13 ℃) was higher than that of pure PPI (101.59 ℃) and the physical mixture (90.40 ℃). These results indicate that the Maillard reaction significantly improved the thermostability of pea proteins, probably because the glycosylation products limited the spreading of the proteins by steric effects. In addition, C4 has the highest denaturation temperature and therefore the best thermal stability compared to other complexes.

4. Oxidation resistance

The method for detecting the oxidation resistance comprises the following steps:

the antioxidant capacity of pea proteins, pea protein-inulin physical mixtures and pea protein-inulin complexes was evaluated using DPPH free radical scavenging. First, a DPPH solution (0.1mM) was prepared with absolute ethanol, and then samples at different concentrations (0.2, 0.4, 0.6, 0.8, 1.0mg/mL) were prepared with distilled water. 0.5mL of the sample was mixed with 2.5mL of DPPH solution and reacted for 30min at room temperature in the dark. Subsequently, the absorbance of the sample was measured at 517nm using an ultraviolet-visible spectrophotometer. The DPPH radical scavenging activity (%) of the sample was calculated as follows:

DPPH radical scavenging Activity (%) [1- (As-Ac)/Ab ]. times.100%

Where As is the absorbance of the sample, Ac is the absorbance of the control (ethanol added instead of DPPH), and Ab is the absorbance of the blank (ethanol added instead of sample).

The oxidation resistance measurements were carried out on untreated pea protein (designated PPI), pea protein-inulin physical mixture (designated Mix), pea protein-inulin complexes prepared in example 2 and comparative examples 1-3, and the results are shown in fig. 4. When the sample concentration is 0.2-1.0mg/mL, the radical scavenging activity decreases in the following order: c4> C3> C2> C1> Mix > PPI. Furthermore, the antioxidant capacity of all samples was increased in a dose-dependent manner. At a concentration of 1.0mg/mL, the free radical scavenging capacity of the four complexes was 1.31, 1.45, 1.57 and 1.88 times that of PPI, respectively. This phenomenon is mainly due to the fact that the conjugates produced in the Maillard reaction form stable DPPH-H molecules by supplying hydrogen, which serves the purpose of scavenging free radicals. In addition, melanoidin produced in the later stage of the Maillard reaction has good antioxidant activity. In all complexes, C4 exhibited the highest antioxidant activity, indicating that the combined pH shift and sonication treatment was effective in accelerating the maillard reaction, thereby promoting the formation of antioxidant reaction products.

5. Nature of the foam

Method for measuring Foaming Capacity (FC) and Foam Stability (FS):

different samples (2mg/mL protein) were placed in vials and the height (H) of the sample solution was measured and recorded₁). The sample was sheared using a high speed shear at 12000rpm for 5min, and the height of the sample solution (H) was measured and recorded immediately thereafter (H)₂). After 30min, the sample height (H) was recorded₃). The Foaming Capacity (FC) and Foam Stability (FS) of the sample are calculated as follows:

FC(％)＝(H₂-H₁)/H₁×100％

FS(％)＝(H₃-H₁)/H₁×100％

the Foaming Capacity (FC) and Foam Stability (FS) of the untreated pea protein (designated PPI), the pea protein-inulin complexes prepared in example 2 and comparative examples 1-3 were examined and the results are shown in fig. 5. The foaming capacity and foam stability of the untreated pea protein were 31.2% and 26.8%, respectively. Foaming capacity and foaming stability are improved after glycosylation, with the magnitude of increase in C4 being greatest, about 3.4 and 3.3 times greater than pure PPI, respectively. This indicates that the combined ultrasound and pH shift treatment is effective in improving the foaming properties of pea protein.

6. Emulsifying Properties

Detection method of Emulsion Activity Index (EAI) and Emulsion Stability Index (ESI):

a sample solution (2mg/mL protein) was prepared using 0.01M phosphate buffer (pH 7), then 2mL corn oil was mixed with 8mL sample solution and sheared at 13000rpm for 3min with a high speed shearer. Immediately after the shearing was complete, 50. mu.L of the emulsion was removed from the bottom of the vessel and added to 5mL of 0.1% (w/v) SDS solution. After standing for 10min, the same treatment was carried out, and the absorbance of the sample was measured at 500nm with an ultraviolet-visible spectrophotometer. EAI and ESI were calculated as follows:

EAI(m₂/g)＝(2×2.303×A₀)/(C×10⁴×Φ)×100

ESI(％)＝A₁₀/A₀×100％

wherein A is₀And A₁₀Absorbance at 0min and 10min, respectively; c is protein concentration (g/mL); Φ is the proportion of the oil phase (0.2).

The untreated pea protein (designated PPI), the pea protein-inulin complexes prepared in example 2 and comparative examples 1-3 were tested for Emulsion Activity Index (EAI) and Emulsion Stability Index (ESI), and the results are shown in fig. 6. The EAI and ESI values of the pea protein-inulin complex are increased compared to pea protein, and the emulsifying properties are improved, possibly due to the increased water solubility thereof. Furthermore, the covalent attachment of hydrophilic inulin chains to the pea protein surface may reduce the tendency of the oil droplets to aggregate with each other by increasing the steric repulsion between them. C4 showed the best emulsification properties compared to other compounds. Therefore, the ultrasonic and pH shift combined auxiliary wet-heat method can effectively improve the emulsifying property of the pea protein.

7. Environmental stability

The emulsion was prepared to improve its environmental stability as follows:

(1) preparation of the emulsion

0.27g of the sample was dissolved in 54mL of deionized water and stirred overnight on a magnetic stirrer at 600rpm to dissolve it sufficiently as an aqueous phase. Algal oil containing 0.6 wt% of lemon essential oil was used as the oil phase. Adding 6mL of oil phase into water phase, and shearing at 10000rpm for 3min by using a high-speed shearing machine to obtain coarse emulsion. And (3) carrying out high-pressure homogenization treatment on the crude emulsion by using a high-pressure homogenizer under the treatment condition of 50MPa, and circulating for 3 times to obtain different emulsions.

(2) Evaluation of emulsion environmental stability

Untreated pea protein (designated PPI), pea protein-inulin physical mixture (designated Mix), pea protein-inulin complexes prepared in example 2 and comparative examples 1-3 were prepared as emulsions, respectively, according to the above-described method and stability measurements were performed under different environmental conditions. 3mL of the emulsion was placed in a measuring flask and different emulsions were treated separately in water baths at different temperatures (40 ℃, 60 ℃ and 80 ℃) for 20min or with an equal volume of NaCl solution (0.2, 0.4, 0.6M). After the treatment, the emulsion was left at room temperature and the particle size of the emulsion was measured the next day, and the results are shown in FIG. 7. The particle size of PPI emulsions increases significantly with increasing processing temperature and salt ion concentration, which may be due to aggregation of emulsion droplets under adverse environmental conditions, and the like. The particle size of the physical mixture and the four compounds also increased, but the magnitude of the increase decreased. This is probably because the introduction of inulin increases the spatial repulsion between droplets, thereby inhibiting the aggregation of droplets. The emulsion prepared with complex C4 remained almost relatively stable, which was associated with its higher degree of grafting, i.e. more inulin attachment.

In summary, protein-stabilized emulsions are highly sensitive to environmental stresses (e.g., ionic strength, heat). The emulsion prepared by the compound can effectively improve the stability of the emulsion under different environmental pressures.

The above-described embodiments are merely illustrative of the preferred embodiments of the present invention, and do not limit the scope of the present invention, and various modifications and improvements of the technical solutions of the present invention can be made by those skilled in the art without departing from the spirit of the present invention, and the technical solutions of the present invention are within the scope of the present invention defined by the claims.