阅读说明：本技术 乙酰化可溶性大豆多糖及其在提高奶茶稳定性中的应用 (Acetylated soluble soybean polysaccharide and application thereof in improving milk tea stability ) 是由 童群义 徐洁茹 耿子蔚 于 2020-12-30 设计创作，主要内容包括：本发明涉及一种乙酰化可溶性大豆多糖及其在提高奶茶稳定性中的应用。本发明按照可溶性大豆多糖与乙酸酐的质量体积比为1:10～25,向可溶性大豆多糖溶液中交替加入氢氧化钠和乙酸酐,在30～50℃下,搅拌反应1～3h,反应过程中,控制反应体系pH在8.0～10.0内,反应结束后调节pH至中性,分离得到乙酰化可溶性大豆多糖。本发明制备得到的乙酰化可溶性大豆多糖,乙酰取代度高,在1.0～1.3范围,具有较可溶性大豆多糖更高的乳化性和起泡性,应用在奶茶中,能够有效提高奶茶稳定性,尤其是高分子量乙酰化可溶性大豆多糖,具有较高的乳化性和起泡性,并能显著提高奶茶的稳定性。(The invention relates to acetylated soluble soybean polysaccharide and application thereof in improving the stability of milk tea. According to the method, sodium hydroxide and acetic anhydride are alternately added into a soluble soybean polysaccharide solution according to the mass-to-volume ratio of 1: 10-25 of the soluble soybean polysaccharide to the acetic anhydride, the mixture is stirred and reacted for 1-3 hours at the temperature of 30-50 ℃, the pH of a reaction system is controlled within 8.0-10.0 in the reaction process, the pH is adjusted to be neutral after the reaction is finished, and the acetylated soluble soybean polysaccharide is obtained through separation. The acetylated soluble soybean polysaccharide prepared by the invention has high acetyl substitution degree within the range of 1.0-1.3, has higher emulsibility and foamability than the soluble soybean polysaccharide, can effectively improve the stability of milk tea when being applied to milk tea, and particularly has higher emulsibility and foamability when being applied to high molecular weight acetylated soluble soybean polysaccharide, and can obviously improve the stability of milk tea.)

1. The preparation method of the acetylated soluble soybean polysaccharide is characterized by comprising the following steps: according to the mass-to-volume ratio of the soluble soybean polysaccharide to the acetic anhydride of 1: 10-25, alternately adding sodium hydroxide and the acetic anhydride into a soluble soybean polysaccharide solution, stirring and reacting for 1-3 hours at 30-50 ℃, controlling the pH of a reaction system within 8.0-10.0 in the reaction process, adjusting the pH to be neutral after the reaction is finished, and separating to obtain the acetylated soluble soybean polysaccharide.

2. The method according to claim 1, wherein the concentration of the soluble soybean polysaccharide solution is 10 to 30 mg/mL.

3. The method according to claim 1, wherein the concentration of the sodium hydroxide is 3-5 mol/L.

4. The method of claim 1, wherein said separating comprises steps of dialysis, concentration under reduced pressure, alcohol precipitation and centrifugation.

5. The method of claim 4, wherein the dialysis is performed for 24-72 hours by using a dialysis membrane with a cut-off of 3000-4000 Da.

6. The method of claim 4, wherein the centrifugation is performed at 3500-4500 r/min for 4-6 min.

7. The method of claim 1, further comprising separating the acetylated soluble soy polysaccharide by ultrafiltration to produce a high molecular weight acetylated soluble soy polysaccharide; the ultrafiltration is carried out by adopting an ultrafiltration membrane with the aperture of 15-25 nm under the pressure of 0.1-0.15 mPa.

8. An acetylated soluble soybean polysaccharide produced by the method of any one of claims 1 to 7.

9. The use of acetylated soluble soy polysaccharide of claim 8 to improve milk tea stability.

10. The use of claim 9, wherein the acetylated soluble soybean polysaccharide is added to milk tea at a concentration of 1-5 mg/mL, and homogenized at 40-80 ℃ and 10-20 MPa.

Technical Field

The invention relates to the technical field of food, in particular to acetylated soluble soybean polysaccharide and application thereof in improving the stability of milk tea.

Background

Polysaccharides are natural high molecular polymers containing aldehyde groups or ketone groups and formed by connecting more than 10 monosaccharides linearly or in a branched way through glycosidic bonds, and are important bioactive macromolecular substances existing in animals, plants and microorganisms. It is widely involved in the regulation of various vital phenomena and physiological processes of cells, and polysaccharide has the physiological activities of resisting virus, infection, tumor, oxidation and radiation, reducing blood sugar, protecting liver, regulating immunity, etc. A large number of pharmacological and clinical researches show that the polysaccharide is an immunomodulator, can activate an immunoreceptor, improve the immune function of an organism and realize an anti-tumor function.

The physicochemical property and the biological activity of the polysaccharide are closely related to the structure of the polysaccharide, the structural factors of the polysaccharide comprise the main chain property, the branched chain property and the high-level structure of polysaccharide molecules, wherein the sugar unit composition and the glycosidic bond type of the main chain of the polysaccharide directly determine the property and the activity of the polysaccharide, and the type, the polymerization degree, the distribution of the branched chain on the polysaccharide chain and the substitution degree of the branched chain determine the property difference and the activity magnitude of the polysaccharide, so the molecular modification and the structural modification of the polysaccharide have important significance for optimizing the physicochemical property and the biological activity.

Soluble Soybean Polysaccharides (SSPS) is a water-soluble anionic polysaccharide extracted from bean dregs, and numerous researches show that the SSPS has abundant dietary fibers and unique functional characteristics, such as the capability of stabilizing protein under an acidic condition, good emulsification stability, foamability, starch adhesion resistance, film-forming property and other functional characteristics and biological activity such as oxidation resistance, so that the soybean polysaccharides have increasingly wide application in the food industry.

The milk tea is a liquid milk product which takes fresh milk or milk powder as a raw material and is added with a certain amount of tea powder or tea water, and is one of popular drinks at present. The milk tea is a complex emulsion system consisting of fat, protein, carbohydrate and the like, wherein the milk protein is easy to react with tea polyphenols in the tea soup to generate macromolecular complex insoluble substances, and the milk fat is easy to float upwards to form a top floating layer. Therefore, in order to maintain a uniform and stable system of milk tea for a certain period of time, it is necessary to add an appropriate emulsion stabilizer.

Disclosure of Invention

In order to solve the technical problems, the invention provides acetylated soluble soybean polysaccharide and application thereof in improving the stability of milk tea.

The first purpose of the invention is to provide a preparation method of acetylated soluble soybean polysaccharide, which comprises the following steps: according to the mass-to-volume ratio of the soluble soybean polysaccharide to the acetic anhydride of 1: 10-25, alternately adding sodium hydroxide and the acetic anhydride into a soluble soybean polysaccharide solution, stirring and reacting for 1-3 hours at 30-50 ℃, controlling the pH of a reaction system within 8.0-10.0 in the reaction process, adjusting the pH to be neutral after the reaction is finished, and separating to obtain the acetylated soluble soybean polysaccharide.

Further, the concentration of the soluble soybean polysaccharide solution is 10-30 mg/mL.

Further, the concentration of the sodium hydroxide is 3-5 mol/L.

Further, the separation comprises the steps of dialysis, concentration under reduced pressure, alcohol precipitation and centrifugation.

Further, the dialysis is carried out for 24-72 hours by adopting a dialysis membrane with the interception amount of 3000-4000 Da.

Further, the reduced pressure concentration is carried out under the conditions that the temperature is 50-70 ℃ and the vacuum degree is 0.08-0.095 mPa.

Further, the alcohol precipitation is to add 3-5 times of absolute ethyl alcohol and carry out alcohol precipitation for 10-15 hours.

Further, the centrifugation is carried out for 4-6 min at 3500-4500 r/min.

Further, the method also comprises the steps of separating the acetylated soluble soybean polysaccharide by ultrafiltration to prepare high molecular weight acetylated soluble soybean polysaccharide; the ultrafiltration is carried out by adopting an ultrafiltration membrane with the aperture of 15-25 nm under the pressure of 0.1-0.15 mPa.

The second purpose of the invention is to provide the acetylated soluble soybean polysaccharide prepared by the method.

The third purpose of the invention is to provide the application of the acetylated soluble soybean polysaccharide in improving the stability of the milk tea.

Further, the acetylated soluble soybean polysaccharide is added into milk tea according to the proportion of 1-5 mg/mL, and the milk tea is homogenized under the conditions of 40-80 ℃ and 10-20 MPa.

By the scheme, the invention at least has the following advantages:

the acetylated soluble soybean polysaccharide prepared by the invention has high acetyl substitution degree within the range of 1.0-1.3, has higher emulsibility and foamability than the soluble soybean polysaccharide, can effectively improve the stability of milk tea when being applied to milk tea, and particularly has higher emulsibility and foamability when being applied to high molecular weight acetylated soluble soybean polysaccharide, and can obviously improve the stability of milk tea.

The foregoing description is only an overview of the technical solutions of the present invention, and in order to make the technical solutions of the present invention more clearly understood and to implement them in accordance with the contents of the description, the following description is made with reference to the preferred embodiments of the present invention and the accompanying detailed drawings.

Drawings

FIG. 1 is a graph showing the effect of feed-solution ratio on the degree of substitution of acetylated soluble soybean polysaccharides;

FIG. 2 is a graph showing the effect of reaction temperature on the degree of substitution of acetylated soluble soybean polysaccharides;

FIG. 3 is a graph showing the effect of reaction time on the degree of substitution of acetylated soluble soybean polysaccharides;

FIG. 4 is a chart of infrared spectroscopic measurements before and after acetylation of soluble soybean polysaccharides;

FIG. 5 is a graph of infrared spectroscopic measurements before and after separation of acetylated soluble soybean polysaccharides.

Detailed Description

The following examples are given to further illustrate the embodiments of the present invention. The following examples are intended to illustrate the invention but are not intended to limit the scope of the invention.

The Soluble Soybean Polysaccharide (SSPS) in the present invention was purchased from weibo food ltd, quanzhou, fujian, with a soluble polysaccharide content of 81.4%, crude protein (on a dry basis) of 0.92%, crude ash (on a dry basis) of 7.2%, and crude fat (on a dry basis) of 0.2%. Other raw materials, unless otherwise specified, are commonly commercially available.

Determination of degree of substitution of acetylated soluble Soybean polysaccharide

The invention adopts a hydroxylamine colorimetric method to measure the substitution degree of acetylated soluble soybean polysaccharide, and the specific operation steps are as follows:

(1) preparing a beta-D-pentaacetylglucose stock solution: 0.6978g of beta-D-pentaacetylglucose is precisely weighed, added into 20mL of ethanol, heated in a water bath at 60 ℃ for dissolution, placed into a 100mL volumetric flask for cooling to room temperature, diluted to a scale by adding water, and shaken uniformly to obtain the beta-D-pentaacetylglucose.

(2) Preparing a beta-D-pentaacetylglucose series standard solution: precisely sucking 2mL, 4mL, 6 mL, 8 mL, 10mL and 12mL of beta-D-pentaacetylglucose reference substance stock solutions, respectively placing in 50mL volumetric flasks, adding water to dilute to a scale, shaking up to obtain the reference substance solution, and sequentially marking as No. 1-6 reference substance solutions.

(3) Preparing a sample solution: accurately weighing 0.02901g of acetylated soluble soybean polysaccharide, dissolving with distilled water, and diluting to 10 mL.

(4) A sample determination step: accurately sucking a certain amount of polysaccharide solution into a 50mL brown volumetric flask, accurately adding 5mL of newly prepared hydroxylamine hydrochloride solution of 0.1mol/L, adding 5mL of sodium hydroxide solution of 1.5mol/L, uniformly mixing, standing for 20min, adding 3.5mL of hydrochloric acid of 2mol/L to neutralize excessive alkali, standing for 20min after uniformly mixing, dropwise adding 10mL of ferric trichloride solution of 0.37mol/L, uniformly mixing, using deionized water to fix the volume, standing for 10min, taking 2.5mL, placing in a 1cm quartz cell, and measuring the absorbance value at 500 nm. The same procedure was used to replace the polysaccharide solution with the same amount of deionized water as a blank and the absorbance was measured over a period of time.

(5) Precisely sucking 5mL of No. 1-6 reference substance solution into a 50mL brown volumetric flask, and measuring the absorbance value at 500nm according to the method in the step (4). And drawing an acetyl mass concentration standard curve by taking the acetyl concentration as an abscissa and the absorbance as an ordinate.

(6) Calculation method of acetyl substitution degree: the acetyl substitution degree refers to the number of hydroxyl groups substituted by acetyl groups on average per anhydroglucose unit, and the specific numerical value is obtained according to the following formula:

W₂(％)＝W₂/W₁×100

DS＝162×W₂％/[4300-(43-1)×W₂％]

in the formula: w₁Mass of polysaccharide (mg), W₂Mass of acetyl groups in polysaccharide (mg), relative molecular mass of one monosaccharide group in 162-acetylated soluble soybean polysaccharide, relative molecular mass of 43-acetyl groups, relative molecular mass of 1-hydrogen atoms.

Since the soluble soybean polysaccharide itself contains a small amount of acetyl groups, the degree of acetyl substitution of the present invention will be expressed in terms of relative degree of substitution.

Example 1: preparation of acetylated soluble soybean polysaccharide

Single-factor experiment of feed-liquid ratio, reaction temperature and reaction time

1. Effect of feed liquid ratio on degree of substitution of acetylated soluble Soybean polysaccharide

Mixing soluble soybean polysaccharide and distilled water according to a mass ratio of 1: 50, and preparing the soluble soybean polysaccharide solution with the concentration of 20 mg/mL. Adjusting the pH value of the solution to 8.0 by using 0.1mol/L sodium hydroxide solution, alternately adding 0.5mol/L sodium hydroxide solution and acetic anhydride into the solution at 40 ℃, controlling the pH value of the system to be within the range of 8.0-10.0, and adding the acetic anhydride according to the volume ratio of the soluble soybean polysaccharide in the solution to the acetic anhydride, namely the material-liquid ratio is 1:5, 1:10, 1:15, 1:20 and 1:25 respectively until the addition is finished. In this example, the content of soluble soybean polysaccharide in the solution was 0.2g, so the amount of acetic anhydride added was 1mL, 2mL, 3mL, 4mL, 5mL for different feed-to-solution ratios. After stirring the reaction for 1.5 hours, the reaction was terminated by adjusting the system pH to 7.0 with 0.1mol/L hydrochloric acid. Dialyzing the reaction solution for 48h by using distilled water of a dialysis bag with the molecular weight cutoff of 3500Da, concentrating the dialyzate to 1/4 of the original volume under the condition of vacuum degree of 0.08-0.095 mPa and 60 ℃, adding 4 times of volume of absolute ethyl alcohol, precipitating with ethanol at 4 ℃ overnight, and freeze-drying to obtain the acetylated soluble soybean polysaccharide.

The substitution degree of the acetylated soluble soybean polysaccharide under different material-to-liquid ratios is shown in fig. 1, and it can be seen from fig. 1 that the substitution degree of the acetylated soluble soybean polysaccharide increases and then decreases with the increase of the addition amount of acetic anhydride, and the substitution degree reaches the maximum value when the addition amount of acetic anhydride is 3mL, namely the material-to-liquid ratio is 1: 15.

2. Effect of reaction temperature on degree of substitution of acetylated soluble Soybean polysaccharide

The experimental steps are carried out in the same way, the material-liquid ratio is fixed to be 1:15, the reaction temperature is controlled to be 30 ℃, 40 ℃, 50 ℃, 60 ℃ and 70 ℃ respectively, the pH value of the system is adjusted to be 7.0 after stirring and reacting for 1.5h, and the acetylated soluble soybean polysaccharide is obtained after dialyzing, concentrating, alcohol precipitating and freeze drying the reaction solution.

The degree of substitution of acetylated soluble soybean polysaccharides under different reaction temperature conditions is shown in fig. 2, and it can be seen from fig. 2 that the degree of substitution of acetylated soluble soybean polysaccharides increases and then decreases with the increase of the reaction temperature, and reaches the maximum value at a reaction temperature of 40 ℃.

3. Effect of reaction time on degree of substitution of acetylated soluble Soybean polysaccharide

And (3) carrying out the experimental steps, fixing the material-liquid ratio to be 1:15, respectively stirring and reacting for 0.5h, 1.0h, 1.5h, 2.0h and 2.5h at the reaction temperature of 40 ℃, then adjusting the pH of the system to be 7.0, dialyzing the reaction liquid, concentrating, precipitating with ethanol and freeze-drying to obtain the acetylated soluble soybean polysaccharide.

The degree of substitution of acetylated soluble soybean polysaccharides under different reaction time conditions is shown in fig. 3, and it can be seen from fig. 3 that the degree of substitution of acetylated soluble soybean polysaccharides increases and then decreases with the increase of the reaction time, and the degree of substitution reaches the maximum value when the reaction time is 1.5 h.

Orthogonal experiment of feed-liquid ratio, reaction temperature and reaction time

The experiment was performed according to the orthogonal analysis table shown in table 1, and the degree of substitution of acetylated soluble soybean polysaccharides was measured.

TABLE 1L₉(3³) Level of design of orthogonal experiments

The degree of substitution and the very poor analytical results of acetylated soluble soybean polysaccharides are shown in table 2:

TABLE 2L₉(3³) Design results of orthogonal experiments

As can be seen from Table 2, the influence of the three experimental factors on the degree of substitution is as follows: the material-liquid ratio is greater than the reaction temperature and greater than the reaction time, the optimal conditions obtained by orthogonal experiments are that the mass ratio of the soluble soybean polysaccharide to the volume of acetic anhydride is 1:15, the reaction temperature is 40 ℃, the reaction time is 1.5h, and a verification experiment is carried out under the optimal conditions to obtain the acetylated soluble soybean polysaccharide with the substitution degree of 2.257, which shows that the optimal conditions are stable and feasible and have good repeatability. The acetylated soluble soybean polysaccharide prepared under the condition is taken for subsequent experiments.

Example 2: fractionation of acetylated soluble soybean polysaccharides

Fully dissolving the acetylated soluble soybean polysaccharide in deionized water to prepare an acetylated soluble soybean polysaccharide solution with the mass fraction of 1%. And adding the solution into a charging basket of an ultrafiltration device for ultrafiltration, wherein the ultrafiltration membrane is a ceramic composite membrane with the aperture of 20nm, and the working pressure is 0.1-0.15 mPa. The low molecular weight acetylated soluble soybean polysaccharide which permeates through the ultrafiltration membrane is collected at a discharge port, and the solution which is not filtered is returned to a charging bucket. When the volume of the solution in the bucket decreased to 25% of the volume of the initial solution, 25% of the initial volume of deionized water was added to the bucket, and after repeating 3 times, the ultrafiltration was terminated when the volume of the solution in the bucket decreased to 25% of the volume of the initial solution. And respectively concentrating the filtrate and the non-filtrate under reduced pressure for 48H, and freeze-drying to obtain high-molecular-weight acetylated soluble soybean polysaccharide (Ac-SSPS-H) and low-molecular-weight acetylated soluble soybean polysaccharide (Ac-SSPS-L).

Example 3: acetylated soluble Soybean polysaccharide analysis

1. Infrared spectroscopic analysis before and after acetylation of soluble soybean polysaccharide and before and after separation of acetylated soluble soybean polysaccharide

The infrared measurement was performed on the sample using fourier infrared spectroscopy. Under a drying lamp, 1mg of soluble soybean polysaccharide, acetylated soluble soybean polysaccharide, high molecular weight acetylated soluble soybean polysaccharide and low molecular weight acetylated soluble soybean polysaccharide samples are respectively accurately weighed, 100mg of KBr is added into an agate mortar for gentle grinding and uniform grinding, the mixture is pressed into transparent sheets by a tablet press, and the transparent sheets are pressed at 4000 plus 400cm^-1And (5) scanning, and deducting the blank background of air to obtain an infrared scanning spectrum of the polysaccharide of the sample.

As can be seen from FIGS. 4 and 5, 3430cm^-1The broad absorption peak at (B) represents O-H stretching vibration, 2927cm^-1The weak absorption at (A) represents a characteristic peak of C-H. After acetylation modification, the soluble soybean polysaccharide has two characteristic absorption peaks: 1740cm^-1The peaks appearing on the left and right sides are estimated as stretching vibration peaks of the acetylester group C ═ O; 1245cm^-1The weak peak appears on the left and right, which is deduced to be the C-O stretching vibration peak of the ester group, and the two characteristic absorption peaks also appear in the infrared spectrum of the separated high and low molecular weight acetylated soluble soybean polysaccharide. The above results confirmed that acetyl groups were present in the acetylated soluble soybean polysaccharide before and after separation. Furthermore, the infrared absorption spectra of the four panels are very close, indicating that acetylation modification and ultrafiltration separation do not alter the general structure of soluble soybean polysaccharides.

2. Determination of molecular weight and mean square rotation radius before and after acetylation of soluble soybean polysaccharide

The molecular weight and the mean square radius of rotation of the samples were determined by means of a high performance gel permeation chromatograph with a multi-angle laser light scattering and refractive index detector using a Shodex OHpak SB-805HQ column. Respectively dissolving 25mg of soluble soybean polysaccharide, acetylated soluble soybean polysaccharide, high molecular weight acetylated soluble soybean polysaccharide and low molecular weight acetylated soluble soybean polysaccharide in 5mL of ultrapure water, filtering the solution with a 0.45um filter, loading the filtered solution on a column, wherein the sample injection volume is 150 mu L, and the mobile phase is 0.1mol/L NaNO₃The solution was at a flow rate of 0.5mL/min and a column temperature of 50 ℃.

The results of measuring the molecular weight and the mean square radius of rotation of Soluble Soybean Polysaccharide (SSPS), acetylated soluble soybean polysaccharide (Ac-SSPS), high molecular weight acetylated soluble soybean polysaccharide (Ac-SSPS-H) and low molecular weight acetylated soluble soybean polysaccharide (Ac-SSPS-L) are shown in table 3:

TABLE 3 molecular weights and mean square radii of rotation for SSPS and Ac-SSPS

As can be seen from table 3, the molecular weight of the acetylated modified soluble soybean polysaccharide was increased, and the acetylated soluble soybean polysaccharide was successfully separated into high molecular weight acetylated soluble soybean polysaccharide having a weight average molecular weight of 586kDa and low molecular weight acetylated soluble soybean polysaccharide having a weight average molecular weight of 57.9kDa by the ultrafiltration membrane having a pore size of 20 nm. Rz represents the degree of stretching of the polymer chain in space, and the Rz of Ac-SSPS is significantly larger than SSPS, which may be caused by electrostatic repulsion between substituents of adjacent chains.

Example 4: determination of emulsifiability of soluble soybean polysaccharide and acetylated soluble soybean polysaccharide

Emulsifiability mainly refers to the Emulsifying Activity (EAI) and Emulsion Stability (ES) of an emulsifier. Respectively dissolving 0.15g of soluble soybean polysaccharide, acetylated soluble soybean polysaccharide, high molecular weight acetylated soluble soybean polysaccharide and low molecular weight acetylated soluble soybean polysaccharide in 15mL of distilled water, respectively adding 5mL of corn oil into the polysaccharide solution, shearing at 15000rpm for 10min at high speed, respectively adding 100 μ L of 0min and 10min standing emulsion bottom layer sample into 10mL of 0.1% Sodium Dodecyl Sulfate (SDS) solution, oscillating uniformly, and measuring absorbance (A) at 500nm wavelength with ultraviolet spectrophotometer₅₀₀) A0.1% SDS solution was used as a blank. Wherein the content of the first and second substances,

in the formula: EAI is the emulsifying surface area (m) per unit mass of polysaccharide²(iv)/g); a is the absorbance value at the wavelength of 500 nm; DF is the dilution multiple of the emulsion in 0.1 percent SDS solution to 100; c is the mass concentration of polysaccharide in the sample solution of-10000 g/m³；The proportion of the oil phase in the emulsion is-0.25; l is the optical path of the cuvette, minus 0.01 m; ES is the stable value of the emulsion after standing for 10 min.

The emulsifiability before and after acetylation of the soluble soybean polysaccharide is shown in Table 4

TABLE 4 emulsifiability of SSPS and Ac-SSPS

As can be seen from table 4, the emulsification activity and the emulsification stability of the acetylated and modified soluble soybean polysaccharide are both significantly improved, and the improvement of the emulsification may be due to the hydrophobic acetyl groups grafted on the soluble soybean polysaccharide, which improves the amphipathy thereof, and the emulsification activity and the emulsification stability of the acetylated soluble soybean polysaccharide with high molecular weight are higher than those of the non-separated acetylated soluble soybean polysaccharide.

Example 5: measurement of foaming Properties of soluble Soybean polysaccharide and acetylated soluble Soybean polysaccharide

Foamability mainly refers to the foam expansion ratio and foam stability of the foaming agent. 0.1g of soluble soybean polysaccharide, acetylated soluble soybean polysaccharide, high molecular weight acetylated soluble soybean polysaccharide and low molecular weight acetylated soluble soybean polysaccharide samples are respectively dissolved in 10mL of distilled water, transferred into a 50mL plastic measuring cylinder, and stirred for 2min by a homogenizer at the speed of 17500 r/min. Wherein:

foam Stability (FS) ═ V2V1

In the formula: FE is foam expansion,%; FS is foam stability,%; v₀Initial volume of solution, mL; v₁The volume of foam immediately after whipping, mL; v₂Foam volume after 30min standing, mL.

Foaming properties before and after acetylation of soluble soybean polysaccharide are shown in Table 5

TABLE 5 foaming Properties of SSPS and Ac-SSPS

As can be seen from table 5, the foam expansion rate and foam stability of the acetylated and modified soluble soybean polysaccharide are both significantly improved, and the improvement of the foaming property may be due to the fact that the hydrophobic acetyl groups are grafted on the soluble soybean polysaccharide, the molecular weight is increased, the amphipathy of the soluble soybean polysaccharide is enhanced, so that the soluble soybean polysaccharide can better generate foam at the air-water interface and keep stable, and the foaming property and foam stability of the acetylated soluble soybean polysaccharide with high molecular weight are higher than those of the acetylated soluble soybean polysaccharide without separation.

Example 6: influence of acetylated soluble soybean polysaccharide on milk tea stability

The emulsion stability of milk tea is expressed by the centrifugal precipitation rate, the oil precipitation rate and the viscosity of milk tea. Weighing 1g of green tea leaves, adding the green tea leaves into 30ml of water, carrying out water bath at 95 ℃ for 20 minutes, filtering the tea leaves by using gauze, and cooling the tea leaves to 60-70 ℃ to obtain tea soup. Respectively weighing 0.08g of soluble soybean polysaccharide, acetylated soluble soybean polysaccharide, high molecular weight acetylated soluble soybean polysaccharide and low molecular weight acetylated soluble soybean polysaccharide, dissolving in a mixed solution of 10mL of tea soup and 30mL of fresh milk, homogenizing at 65 ℃ and 15MPa, and preparing milk tea without soybean polysaccharide as a blank control. After cooling to room temperature, the milk tea viscosity was measured with a viscometer. The centrifugal precipitation rate and the oil precipitation rate of the milk tea are measured by centrifugation, and the milk tea is centrifuged for 10 minutes at 3000 r/min. Wherein:

in the formula, M₁G is the mass of the precipitate; m₂Sample mass before centrifugation, g.

In the formula, N₁The volume of the top floating layer is mL; n is a radical of₂Sample volume before centrifugation, mL.

The effect of acetylated soluble soybean polysaccharide on the stability of milk tea is shown in table 6

TABLE 6 influence of SSPS and Ac-SSPS on milk tea stability

As can be seen from table 6, the addition of SSPS and Ac-SSPS to the milk tea can lower the centrifugal precipitation rate and the oil precipitation rate of the milk tea, and the milk tea with the addition of Ac-SSPS has less centrifugal precipitation and oil precipitation; the addition of both SSPS and Ac-SSPS increases the viscosity of the milk tea, and the milk tea with Ac-SSPS has higher viscosity. Therefore, the milk tea can be improved in stability by adding the soybean polysaccharide or the acetylated soluble soybean polysaccharide into the milk tea, and the milk tea stabilizer prepared by adding the acetylated soluble soybean polysaccharide with high molecular weight has a better effect.

The above is only a preferred embodiment of the present invention, and is not intended to limit the present invention, it should be noted that, for those skilled in the art, many modifications and variations can be made without departing from the technical principle of the present invention, and these modifications and variations should also be regarded as the protection scope of the present invention.