CN113278178A

CN113278178A - Method for preparing edible film by using soybean protein isolate and chitosan

Info

Publication number: CN113278178A
Application number: CN202110664794.1A
Authority: CN
Inventors: 郑志; 聂鹏; 麻志刚; 罗水忠; 李兴江; 姜绍通
Original assignee: Hefei University of Technology
Current assignee: Hefei University of Technology
Priority date: 2021-06-16
Filing date: 2021-06-16
Publication date: 2021-08-20

Abstract

A method of making an edible film from soy protein isolate and chitosan, comprising: (1) preparing a modified soy protein isolate solution, (2) preparing chitosan, (3) preparing a chitosan solution, (4) preparing a mixed membrane solution, (5) plasticizing and degassing, and (6) forming a membrane. The invention utilizes the soybean protein isolate and the chitosan as raw materials and is supplemented with the glycerol to develop the edible film, the performance of the single-attribute edible film can be improved, and the chitosan can be extracted from the shrimp and crab shells, thereby achieving the recycling of resources and improving the comprehensive utilization value of wastes.

Description

Method for preparing edible film by using soybean protein isolate and chitosan

Technical Field

The invention belongs to the technical field of deep processing of agricultural products, and relates to a method for preparing an edible film by using soybean protein isolate and chitosan.

Background

Soybean is one of the most economically and economically valuable agricultural products in the world because of its unique chemical composition. In cereals and other legumes, the protein content in soybeans is highest, about 40%. The soybean protein isolate is a complete protein food additive produced by using low-temperature desolventized soybean meal as a raw material. The isolated soy protein has a protein content of above 90%, and approximately 20 kinds of amino acids, and contains essential amino acids for human body. The proper addition of soy protein isolate in the food product can improve the protein efficiency ratio. Soy protein isolates are classified into 2S, 7S, 11S and 15S proteins according to the rate of protein sedimentation, with the two components with the highest content being the 7S and 11S proteins.

Soy protein isolates have a range of functional properties and are widely used in the food industry, the main functional properties including: (1) emulsibility, (2) gel property, (3) foamability, and (4) film-forming property. The clinical application shows that the isolated soy protein also has the health care function: (1) removing excess sterols from the blood; (2) significantly reducing cholesterol content in blood; (3) lipids and linoleic acid can prevent cardiovascular diseases.

Chitin, also known as chitin and chitin, is a polysaccharide substance extracted from the shells of marine crustaceans, has a chemical formula of (C8H13O5N) n, is light beige to white, is soluble in concentrated hydrochloric acid, phosphoric acid, sulfuric acid and acetic acid, is insoluble in alkali and other organic solvents, and is also insoluble in water. The chitin has wide application range, and can be used for cloth, clothes, dye, paper, water treatment and the like in industry; the medical articles can be used as contact lenses, artificial skin, suture lines, artificial dialysis membranes, artificial blood vessels and the like; as cosmetic, hair protection, moisturizer, etc.; in addition, it can be used as fish feed, plant antiviral agent, etc.

The chitosan is a primary derivative of chitin, and the chemical component is polyglucosamine, which is obtained by removing acetyl in molecules of the chitin through NaOH solution. Chitosan is also called chitosan deacetylation since it is a derivative of chitin, and its chemical name is called polyglucosamine (1-4) -2-amino-B-D glucose, a chemical product obtained from chitin through deacetylation process. Chitosan has excellent properties such as biological functionality, compatibility, blood compatibility, safety, and microbial degradability, and is also a natural polymer, so it has attracted extensive attention in various industries, and is mainly embodied in the following fields: medicine, food, chemical engineering, biochemical engineering, biomedicine engineering and other fields. Chitosan is fully utilized in the food industry at present, and the chitosan has high viscosity and is insoluble in water, so that the chitosan reacts with soybean protein isolate by utilizing the characteristics of the chitosan, and the preparation of the edible film is carried out.

Disclosure of Invention

The invention aims to provide a method for preparing an edible film by using isolated soy protein and chitosan.

In order to achieve the above objects and other related objects, the present invention provides the following technical solutions: a method for preparing edible film by using soybean protein isolate and chitosan comprises the following steps:

step 1: dissolving 1-10g of soybean protein isolate in 150-250mL of distilled water, heating in a water bath at 80-90 ℃ for 25-35min after dissolving to modify the soybean protein isolate, cooling to 40-48 ℃, and preserving heat for 0.8-1.2h to obtain solution A;

step 2: cleaning shrimp shells, putting the cleaned shrimp shells into an oven, and drying the shrimp shells for 2-3 hours at the temperature of 60-70 ℃; crushing the dried shrimp shell powder to 40-60 meshes to obtain the shrimp shell powder; mixing the shrimp shell powder with an HCl solution with the mass fraction of 4-6% according to the mass ratio of 1:5.0-10.0, stirring for reaction to remove calcium in the shrimp shell powder, filtering the obtained reaction material, and collecting filter residues; washing the filter residue with purified water, and draining;

mixing the filter residue after water removal with purified water according to the mass ratio of 1:10-25, uniformly stirring, adjusting the pH value to 3.0-3.2, adding acid protease, keeping the temperature at 50-51 ℃, stirring at the rotating speed of 30-60r/min, performing enzymolysis for 90-120min, filtering the obtained enzymolysis material, and collecting enzymolysis filter residue;

placing the enzymolysis filter residue into purified water, performing ultrasonic treatment, filtering, and collecting to obtain ultrasonic cleaning filter residue; mixing the ultrasonic cleaning filter residue with 40-45% NaOH solution according to the mass ratio of 1:2.5-5.0, heating to 90-92 ℃ and reacting for 1-2 h; filtering the reaction solution, and collecting the obtained alkali treatment filter residue; washing the alkali-treated filter residue with purified water, and drying the filter residue to obtain chitosan;

and step 3: weighing 1-6g of chitosan, dissolving the chitosan in 400mL of acetic acid solution with the mass fraction of 0.4-0.6%, stirring to dissolve the chitosan, adjusting the pH value to 2.9-3.1, and stirring for 3.5-4.5h at the rotating speed of 50-100r/min to obtain solution B;

and 4, step 4: adding the solution A into the solution B, and stirring while adding to obtain a mixed solution, wherein the mass fraction of the total substrate in the mixed solution is controlled to be 2%;

and 5: adding glycerol into the mixed solution, and uniformly stirring for plasticizing; placing the plasticized mixed solution in a vacuum environment, standing for 5-10min, and removing bubbles;

step 6: pouring the degassed mixed solution into a mold to prepare a film with the thickness of 0.04-0.06mm, putting the film and the mold into a drying device, and drying at 40-60 ℃ until the film is fixed and molded to obtain the finished product of the edible film.

The preferable technical scheme is as follows: in the step 2, HCl solution with the mass fraction of 0.5-5.0% is used for adjusting the pH value.

The preferable technical scheme is as follows: the enzyme activity of the acid protease is 5-20 ten thousand U, and the addition amount is 1.0-5.0% of the mass of the filter residue.

The preferable technical scheme is as follows: the technological parameters during ultrasonic treatment are as follows: ultrasonic frequency of 25-35KHz and power density of 0.25-0.50W/cm²And the ultrasonic treatment time is 10-20 min.

The preferable technical scheme is as follows: in the mixed solution, the mass ratio of the chitosan to the modified soybean protein isolate is 2: 1-1: 2.

due to the application of the technical scheme, compared with the prior art, the invention has the advantages that:

1. the invention utilizes the soybean protein isolate and the chitosan as raw materials and is supplemented with the glycerol to develop the novel edible film, the performance of the single-attribute edible film can be improved, and the chitosan can be extracted from the shrimp and crab shells, thereby achieving the recycling of resources and improving the comprehensive utilization value of wastes.

2. The invention can develop a new idea for solving the existing biological preservation problem by developing a novel edible film, and can improve the application of the soybean protein isolate.

3. Compared with the traditional film, the novel edible film can greatly improve the physicochemical property and enhance the fresh-keeping effect, does not produce pollution on the edible application level, does not produce any garbage and secondary pollution, and can meet the requirements of environmental protection.

Detailed Description

The following description of the embodiments of the present invention is provided for illustrative purposes, and other advantages and effects of the present invention will become apparent to those skilled in the art from the present disclosure.

Example 1: method for preparing edible film by using soybean protein isolate and chitosan

A method for preparing edible films by utilizing soy protein isolate and chitosan is characterized by comprising the following technical steps.

(1) Preparation of modified isolated Soy protein

Weighing 5g of soybean protein isolate, dissolving in 200mL of distilled water, fully dissolving, heating in water bath at 85 ℃ for 30min, modifying the soybean protein isolate, cooling to 45 ℃, and preserving heat for 1h to obtain solution A.

(2) Preparation of Chitosan

The raw material of the shrimp shell is fresh crayfish shell without mildew or rot.

Pulverizing and decalcifying. Cleaning shrimp shells, putting the cleaned shrimp shells into an oven, and drying the shrimp shells for 2.5 hours at the temperature of 65 ℃ until the water content of the shrimp shells is lower than 10%; crushing the dried shrimp shell to 50 meshes to obtain shrimp shell powder; mixing the shrimp shell powder and an HCl solution with the mass fraction of 5% according to the mass ratio of 1:7.5, fully stirring for reaction, and removing calcium in the shrimp shell powder; filtering the reaction material by adopting medium-speed filter paper, and collecting acidolysis filter residues; washing the filter residue with sufficient food-grade purified water, and draining off water for later use.

And (4) carrying out enzymolysis to remove protein. Mixing acidolysis filter residues and food-grade purified water according to the mass ratio of 1:18, putting the mixture into enzyme treatment equipment with stirring and heat preservation functions, fully stirring the mixed materials, and then dropwise adding an HCl solution with the mass fraction of 2% to adjust the pH of the mixed solution to 3; adding acid protease into the mixed solution, keeping the temperature at 50.5 ℃, stirring at the rotating speed of 45r/min, and performing enzymolysis for 110 min; and filtering the enzymolysis material by adopting medium-speed filter paper, and collecting enzymolysis filter residues for later use. The enzyme activity of the acid protease is 10 ten thousand U, and the addition amount of the acid protease is 2.16 percent of the mass of the acidolysis filter residue.

And (4) deacetylating. At room temperature, the enzymolysis filter residue is put into sufficient food grade purified water, and the ultrasonic frequency is 30KHz, and the power density is 0.35W/cm²Fully treating for 15min by using ultrasonic waves, filtering by using medium-speed filter paper, and collecting ultrasonic cleaning filter residues; mixing the ultrasonic cleaning filter residue and a NaOH solution with the mass fraction of 42% according to the mass ratio of 1:3, putting the mixture into thermal reaction equipment with a condensed water reflux device, and reacting for 1.5 hours at the temperature of 91 ℃; filtering the reaction solution by adopting medium-speed filter paper, and collecting alkali treatment filter residues; and fully washing the alkali-treated filter residue by using sufficient food-grade purified water, and drying the filter residue to obtain chitosan for later use.

(3) Preparation of Chitosan solution

Weighing 3.5g of chitosan in the step (2), dissolving the chitosan in 300mL of acetic acid solution with the mass fraction of 0.5%, fully stirring to dissolve the chitosan, adjusting the pH value by using 0.1mol/L NaOH to be 3.0, stirring for 4 hours at a rotation speed of 75r/min under the condition to prepare a chitosan solution with a more stable property and structure, and preparing a solution B;

(4) preparing mixed membrane liquid

And (2) weighing the prepared modified soybean protein isolate solution and modified chitosan solution for later use, slowly adding the solution A into the solution B, stirring while adding, and on the premise that the pH value of the modified chitosan solution is 3.0, better dissolving the soybean protein isolate solution into the chitosan solution. The total substrate in the mixed solution is controlled to be 2% (namely m soybean protein isolate + m chitosan is 2% membrane solution). In the mixed membrane liquid, the approximate range of the mass ratio of the chitosan to the modified soybean protein isolate is 2: 1-1: 2, and the optimal proportion is researched in the range.

(5) Plasticization and degassing

Adding a proper amount of 1.5g of glycerol into the mixed solution in the step (4), fully and uniformly stirring, and performing plasticizing treatment; and placing the plasticized mixed solution into a vacuum environment, standing for 7min in an environment with vacuum gauge pressure of-0.09 to-0.10 MPa, and removing bubbles.

(6) Film formation

And (3) pouring the degassed mixed solution in the step (5) into a mould to form a film with the thickness of 0.05mm, putting the film and the mould into a drying device, and drying at 50 ℃ until the film is fixed and formed to obtain the finished edible film. The die is in a frame shape with a closed bottom and a certain frame height, and is made of food-grade plastic or stainless steel with certain high-temperature-resistant materials. When the enzymolysis process of the shrimp shell protein is optimized as follows: the enzyme addition amount is 2.16%, the enzymolysis temperature is 50.5 ℃, and the pH value is 3.0. Under the condition, the deproteinization rate of the shrimp shell is 78.9%. The chitosan is prepared by using the deproteinized shrimp shells, the extraction rate of the chitin is 62.6 percent, the chitosan yield is 34.2 percent, and the deproteinization rate of the shrimp shells in the embodiment is 78.9 percent. The chitosan is prepared by using the deproteinized shrimp shells, the extraction rate of the chitin is 62.6 percent, and the yield of the chitosan is 34.2 percent.

TABLE 1 influence of SPI: CS on membrane performance.

SPI:CS	TS(MPa)	E(％)	WVP
				3:0	5.05±0.25	2.51±0.13	1.3021±0.0651
2:1	8.08±0.41	6.13±0.31	0.9324±0.0462
				1:1	8.76±0.44	8.77±0.44	0.7843±0.0391
1:2	9.47±0.47	4.46±0.22	1.0453±0.0521
				0:3	11.34±0.57	3.32±0.17	1.1578±0.0578

As can be seen from Table 1, the tensile strength of the film is significantly different (p is less than or equal to 0.05) in the five film-forming materials, and the tensile strength is determined by the following formula: the decrease in CS gradually increases the tensile strength of the film. This is because when the dosage of SPI is low, the dosage of CS is relatively high, and the weaker binding force between protein and polysaccharide is replaced by the stronger binding force between polysaccharide, and therefore, the tensile strength of the composite membrane increases with the increase of the CS ratio; the elongation at break of the film tends to be obvious (p is less than or equal to 0.05) along with the increase of the proportion of the chitosan, and the change trend is that the elongation at break of the film increases firstly and then decreases.

Note:

(1) SPI: isolated soy protein.

(2) CS: and (3) chitosan.

(3) TS: tensile strength.

(4) E: elongation at break.

(5) WVP: water vapor transmission coefficient.

(6) The detection method of the tensile strength and the elongation at break is carried out according to the national standard, and is GB 13022-91;

(7) the water vapor transmission coefficient is measured according to GB1037-1988 by using a moisture permeable cup and a temperature and humidity regulating box.

TABLE 2 Effect of Glycerol addition on film Performance

Amount of glycerin added (%)	TS(MPa)	E(％)	WVP
				0.5	11.08±0.56	9.51±0.45	1.1521±0.0551
1.0	9.76±0.49	11.13±0.56	1.0934±0.0546
				1.5	8.45±0.41	13.77±0.69	0.9843±0.0491
2.0	7.17±0.36	16.46±0.83	0.8453±0.0421
				2.5	6.34±0.32	23.32±1.17	0.7128±0.0357

As can be seen from Table 2, the greater the concentration of glycerol, the more pronounced the effect on tensile strength (p.ltoreq.0.05). The tensile strength of the film gradually decreased with increasing glycerol addition. The reason is that the addition of glycerol destroys the structure of the original macromolecular chain in the membrane, reduces the polymerization degree of macromolecules, increases the free space of molecules in the membrane structure, causes the reduction of the crystallinity of the membrane, influences the order of the molecules, weakens the interaction between the molecules, and macroscopically shows that the tensile strength of the membrane is reduced. The influence of the concentration of the glycerol on the elongation at break is remarkable (P is less than or equal to 0.05), the larger the addition amount of the glycerol is, the higher the plasticity of the film is, the larger the elongation at break is, and the remarkable difference (P is less than or equal to 0.05) exists only when the difference of the addition amount of the glycerol is large. The film shape decreased and then increased with the increase in the amount of glycerin added, which is related to the difference in the optimum amount of glycerin addition required for the single component of the two film-forming materials at the time of film formation.

Note:

(1) TS: tensile strength.

(2) E: elongation at break.

(3) WVP: water vapor transmission coefficient.

(4) The detection method of tensile strength and elongation at break is carried out according to the national standard and is GB 13022-91.

(5) The water vapor transmission coefficient is measured according to GB1037-1988 by using a moisture permeable cup and a temperature and humidity regulating box.

TABLE 3 influence of pH on Membrane Performance

As can be seen from table 3, there is a significant difference in pH versus tensile strength (p ≦ 0.05), with increasing pH the tensile strength of the film increasing first and then decreasing, and at pH3 the tensile strength reaches a maximum. When the pH value is 4-5, the elongation at break of the film is changed most obviously (p is less than or equal to 0.05); the WVP of the membrane did not change significantly with increasing pH (P > 0.05).

Note:

(1) TS: tensile strength.

(2) E: elongation at break.

(3) WVP: water vapor transmission coefficient.

TABLE 4 Effect of drying temperature on film Performance

Drying temperature	TS(MPa)	E(％)	WVP
				50	12.88±0.66	16.51±0.85	0.8621±0.0451
55	11.26±0.54	15.53±0.76	0.9934±0.0546
				60	10.45±0.51	14.27±0.69	1.2843±0.0591
65	9.17±0.46	13.46±0.63	1.4753±0.0621
				70	8.34±0.42	12.12±0.61	1.5128±0.0757

As can be seen from Table 4, the tensile strength of the film decreased with increasing drying temperature and the trend of change was significant (p.ltoreq.0.05). This is because the higher the temperature, the faster the solvent evaporates, so that the film-forming macromolecules are prematurely fixed before they form a more regular aggregated structure by intermolecular ordered crosslinking, and the higher the temperature, the more irregular the film surface will have cracks or uneven thickness. When the temperature difference is more than 10 ℃, the changes of the elongation at break and the WVP of the membrane are more obvious (p is less than or equal to 0.05), and the elongation at break of the membrane is reduced along with the increase of the drying temperature. As the drying temperature increased, the WVP of the membrane increased.

Note:

(1) TS: tensile strength.

(2) E: elongation at break.

(3) WVP: water vapor transmission coefficient.

Example 2: method for preparing edible film by using soybean protein isolate and chitosan

A method for preparing edible film by using soybean protein isolate and chitosan comprises the following steps:

step 1: dissolving 1g of soybean protein isolate in 150mL of distilled water, heating the soybean protein isolate in water bath at 80 ℃ for 25min after dissolving to modify the soybean protein isolate, cooling to 40 ℃, and preserving heat for 0.8h to obtain solution A;

step 2: cleaning shrimp shells, putting the cleaned shrimp shells into an oven, and drying the shrimp shells for 2 hours at the temperature of 60 ℃; crushing the dried shrimp shell to 40 meshes to obtain shrimp shell powder; mixing the shrimp shell powder with an HCl solution with the mass fraction of 4% according to the mass ratio of 1:5.0, stirring for reaction to remove calcium in the shrimp shell powder, filtering the obtained reaction material, and collecting filter residues; washing the filter residue with purified water, and draining;

mixing the filter residue after water removal with purified water according to the mass ratio of 1:10, uniformly stirring, adjusting the pH value to 3.0, then adding acid protease, keeping the temperature at 50 ℃, stirring at the rotating speed of 30r/min, performing enzymolysis for 90min, filtering the obtained enzymolysis material, and collecting enzymolysis filter residue;

placing the enzymolysis filter residue into purified water, performing ultrasonic treatment, filtering, and collecting to obtain ultrasonic cleaning filter residue; mixing the ultrasonic cleaning filter residue with a NaOH solution with the mass fraction of 40% according to the mass ratio of 1:2.5, and heating to 90 ℃ for reaction for 1 h; filtering the reaction solution, and collecting the obtained alkali treatment filter residue; washing the alkali-treated filter residue with purified water, and drying the filter residue to obtain chitosan;

and step 3: weighing 1g of chitosan, dissolving the chitosan in 150mL of acetic acid solution with the mass fraction of 0.4%, stirring to dissolve the chitosan, adjusting the pH value to 2.9, and stirring for 3.5 hours at the rotating speed of 50r/min to obtain a solution B;

and 5: adding glycerol into the mixed solution, and uniformly stirring for plasticizing; placing the plasticized mixed solution in a vacuum environment, standing for 5min, and removing bubbles;

step 6: pouring the degassed mixed solution into a mould to prepare a film with the thickness of 0.04mm, putting the film and the mould into a drying device, and drying at 40 ℃ until the film is fixed and formed to obtain the finished product of the edible film.

The preferred embodiment is: in step 2, an HCl solution with a mass fraction of 0.5% is used to adjust the pH.

The preferred embodiment is: the enzyme activity of the acid protease is 5 ten thousand U, and the addition amount of the acid protease is 5.0 percent of the mass of the filter residue.

The preferred embodiment is: the technological parameters during ultrasonic treatment are as follows: ultrasonic frequency 25KHz, power density 0.25W/cm²And the ultrasonic treatment time is 10 min.

The preferred embodiment is: in the mixed solution, the mass ratio of the chitosan to the modified isolated soy protein is 2-1.

Example 3: method for preparing edible film by using soybean protein isolate and chitosan

step 1: dissolving 10g of soybean protein isolate in 250mL of distilled water, heating the soybean protein isolate in water bath at 90 ℃ for 35min after dissolving to modify the soybean protein isolate, cooling to 48 ℃, and preserving heat for 1.2h to obtain solution A;

step 2: cleaning shrimp shells, putting the cleaned shrimp shells into an oven, and drying the shrimp shells for 3 hours at the temperature of 70 ℃; crushing the dried shrimp shell powder to 40-60 meshes to obtain the shrimp shell powder; mixing the shrimp shell powder with an HCl solution with the mass fraction of 6% according to the mass ratio of 1:10.0, stirring for reaction to remove calcium in the shrimp shell powder, filtering the obtained reaction material, and collecting filter residues; washing the filter residue with purified water, and draining;

mixing the filter residue after water removal with purified water according to a mass ratio of 1:25, uniformly stirring, adjusting the pH value to 3.2, adding acid protease, keeping the temperature at 51 ℃, stirring at a rotating speed of-60 r/min, performing enzymolysis for 120min, filtering the obtained enzymolysis material, and collecting enzymolysis filter residue;

placing the enzymolysis filter residue into purified water, performing ultrasonic treatment, filtering, and collecting to obtain ultrasonic cleaning filter residue; mixing the ultrasonic cleaning filter residue with a NaOH solution with the mass fraction of 45% according to the mass ratio of 1:5.0, heating to 92 ℃, and reacting for 2 hours; filtering the reaction solution, and collecting the obtained alkali treatment filter residue; washing the alkali-treated filter residue with purified water, and drying the filter residue to obtain chitosan;

and step 3: weighing 6g of chitosan, dissolving the chitosan in 400mL of acetic acid solution with the mass fraction of 0.6%, stirring to dissolve the chitosan, adjusting the pH value to 3.1, and stirring for 4.5 hours at the rotating speed of 100r/min to obtain a solution B;

and 5: adding glycerol into the mixed solution, and uniformly stirring for plasticizing; placing the plasticized mixed solution in a vacuum environment, standing for 10min, and removing bubbles;

step 6: pouring the degassed mixed solution into a mold to prepare a film with the thickness of 0.06mm, putting the film and the mold into a drying device, and drying at 60 ℃ until the film is fixed and molded to obtain the finished edible film.

The preferred embodiment is: in step 2, a 5.0% by mass HCl solution was used to adjust the pH.

The preferred embodiment is: the enzyme activity of the acid protease is 20 ten thousand U, and the addition amount of the acid protease is 1.0 percent of the mass of the filter residue.

The preferred embodiment is: the technological parameters during ultrasonic treatment are as follows: the ultrasonic frequency is 35KHz, and the power density is 0.50W/cm²And the ultrasonic treatment time is 20 min.

The preferred embodiment is: in the mixed solution, the mass ratio of the chitosan to the modified soybean protein isolate is 1:2.

the foregoing is illustrative of the preferred embodiment of the present invention and is not to be construed as limiting thereof in any way, and any modifications or variations thereof that fall within the spirit of the invention are intended to be included within the scope thereof.

Claims

1. A method for preparing edible film by using soybean protein isolate and chitosan is characterized in that: comprises the following steps:

2. The method of preparing an edible film using soy protein isolate and chitosan as claimed in claim 1, wherein: in the step 2, HCl solution with the mass fraction of 0.5-5.0% is used for adjusting the pH value.

3. The method of preparing an edible film using soy protein isolate and chitosan as claimed in claim 1, wherein: the enzyme activity of the acid protease is 5-20 ten thousand U, and the addition amount is 1.0-5.0% of the mass of the filter residue.

4. The method of preparing an edible film using soy protein isolate and chitosan as claimed in claim 1, wherein: the technological parameters during ultrasonic treatment are as follows: ultrasonic frequency of 25-35KHz and power density of 0.25-0.50W/cm²And the ultrasonic treatment time is 10-20 min.

5. The method of preparing an edible film using soy protein isolate and chitosan as claimed in claim 1, wherein: in the mixed solution, the mass ratio of the chitosan to the modified soybean protein isolate is 2: 1-1: 2.