Preparation method of starch film for inhibiting postharvest fungi

Abstract

The invention relates to the technical field of starch films, in particular to a preparation method of a starch film for inhibiting postharvest fungi. The preparation method comprises the following steps: 1) drying treatment; 2) preparing a treating fluid; 3) mixing and reacting to prepare a modified raw material, and S2) gelatinization treatment: mixing the modified raw material with distilled water, and heating to prepare gelatinized starch. In the processing process of the starch film for inhibiting the postharvest fungi, the starch raw material is pretreated, so that the microporous corn starch is subjected to enzymolysis reaction, the microporous corn starch subjected to the enzymolysis reaction is changed, the molecular chain is shortened, the molecular weight is reduced, and the molecular chain of the microporous corn starch becomes looser; in the subsequent film forming treatment, the enzymolysis-improved microporous corn starch can be better combined with turpentine with a plasticizing function, so that starch molecules are relatively stable in structure in the plastic film forming process, and the strength performance of the starch film for inhibiting postharvest fungi is effectively improved.

Description

Technical Field

[0001] The invention relates to the technical field of starch films, in particular to a method for preparing a starch film capable of inhibiting postharvest fungi. Background Art

[0002] The starch film that inhibits post-harvest fungi is a film made of starch as the main raw material. The starch film can cover the surface of agricultural products such as fruits and vegetables to prevent fungal spores in the external environment from contacting the agricultural products, reduce the chance of fungal infection, and increase the shelf life of post-harvest crops.

[0003] In the prior art, starch films that inhibit postharvest fungi are mainly prepared using starch as a raw material. Although they have the advantages of safety, environmental protection, and degradability, the molecular chains of starch are arranged relatively tightly. When subjected to a tensile external force, they are easily broken, which affects the strength performance of the starch films that inhibit postharvest fungi. Based on this, the present invention provides a method for preparing a starch film that inhibits postharvest fungi. Summary of the invention

[0004] The object of the present invention is to provide a method for preparing a starch film for inhibiting postharvest fungi. The starch film for inhibiting postharvest fungi prepared by the present invention not only has good tensile strength, but also has excellent elongation at break performance, thereby effectively improving the performance of the starch film for inhibiting postharvest fungi.

[0005] To achieve the above object, the present invention provides the following technical solution: a method for preparing a starch film for inhibiting postharvest fungi, comprising the following steps:

[0006] S1: raw material preparation, wherein the raw material is microporous corn starch, and the microporous corn starch is pretreated to obtain a modified raw material. The preparation method of the modified raw material includes:

[0007] 1) Drying treatment;

[0008] 2) Preparation of treatment solution;

[0009] 3) Mixing reaction to obtain modified raw materials;

[0010] S2: gelatinization treatment, wherein the modified raw material is mixed with distilled water and heated to obtain gelatinized starch;

[0011] S3: preparing a mixture, wherein the mixture is a mixture of chitosan, sodium alginate, glycerol and acetic acid solution;

[0012] S4: preparing an additive, wherein the raw materials of the additive are composed of erythritol, lotus root starch, tea tree essential oil, turpentine and pectin, and the mass ratio of erythritol, lotus root starch, tea tree essential oil, turpentine and pectin is 1: (0.2-0.4): (0.1-0.3): (0.4-0.6): (0.1-0.3);

[0013] S5: starch film preparation, the starch film preparation method comprising:

[0014] Step 1: Preparation of film-forming solution;

[0015] Step 2: Forming treatment: the film-forming liquid obtained in step 1 is subjected to forming treatment to obtain a starch film that inhibits post-harvest fungi.

[0016] Furthermore, the drying method is as follows: the microporous corn starch is broken up, spread flat and sent into an oven, the oven is set at 38-42° C. and dried at 40-50° C. to complete the drying process.

[0017] Furthermore, the treatment liquid is prepared by the following method: disodium hydrogen phosphate dodecahydrate and deionized water are added to a beaker and mixed, the mass ratio of disodium hydrogen phosphate dodecahydrate to deionized water is 1:(4-6), citric acid is added after mixing, the mass of the citric acid is 8-10% of the mass of the deionized water, and the treatment liquid is prepared after further mixing.

[0018] Furthermore, the method of the mixing reaction is as follows: the microporous corn starch and the treatment liquid are mixed in a water bath, the temperature is raised to 84-88°C, and the reaction is kept warm for 22-26 minutes. During the above-mentioned insulation process, a stirring device is used to continuously stir, and the stirring device is set to 120-160r / min. After the insulation reaction is completed, the temperature is cooled to 50°C, and amylase is added. The mass of the amylase is equal to the mass of the microporous corn starch. The insulation reaction is carried out for 1-3 hours. After the insulation reaction is completed, the temperature is raised to a boiling water state and kept warm for 2-4 hours to complete the mixing reaction and obtain a modified raw material.

[0019] Furthermore, the gelatinization treatment method is: the modified raw material is mixed with distilled water in a water bath, heated to 80-90° C., and kept warm for 12-16 minutes to obtain gelatinized starch, wherein the mass of the distilled water is 20-60 times the mass of the modified raw material.

[0020] Furthermore, the mass ratio of the chitosan, sodium alginate, glycerol and acetic acid solution is 1: (0.6-0.8): (0.6-0.8): (40-60), and the mass of the mixture is 1.1-1.3 times the mass of the gelatinized starch.

[0021] Furthermore, the additive is prepared by the following method: the erythritol, lotus root powder, tea tree essential oil, turpentine and pectin are added into a mixer, the stirring process is set at 120-160 r / min for 8-12 minutes, then distilled water is added, the mass of the distilled water is 50-60% of the mass of the mixture in the mixer, the stirring process is set at 320-360 r / min for 16-20 minutes, and the additive is prepared.

[0022] Furthermore, the preparation method of the film-forming liquid is as follows: gelatinized starch, mixed material and additives are added into a mixer, and stirred at 220-260 r / min for 20-30 min. The obtained mixture is homogenized and emulsified at a pressure of 40-60 MPa for 20-30 min, and then ultrasonically treated at a power of 300-400 W for 20-30 min to obtain a film-forming liquid.

[0023] Furthermore, the molding treatment method is: the film-forming liquid is cast onto a polytetrafluoroethylene flat plate, and then put into an oven, and dried at 40 to 50° C. for 20 to 30 hours to obtain a film.

[0024] Furthermore, the film is placed in an environment with a temperature of 36 to 40° C. and a humidity of 30 to 50% and allowed to stand for 10 to 20 hours, and then packaged to obtain a starch film that inhibits postharvest fungi.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] 1. In the present invention, during the processing of the starch film for inhibiting postharvest fungi, the pretreatment step of the starch raw material can cause the microporous corn starch to undergo an enzymatic hydrolysis reaction. After the enzymatic hydrolysis reaction, the microporous corn starch changes, its molecular chain shortens, the molecular weight decreases, and the molecular chain of the microporous corn starch becomes looser. In the subsequent film-forming treatment, the enzymatically improved microporous corn starch can be better combined with turpentine with a plasticizing function, so that the structure of the starch molecules is relatively stable during the plastic film-forming process, thereby effectively improving the strength performance of the starch film for inhibiting postharvest fungi.

[0027] 2. In the present invention, by adding lotus root powder, the lotus root powder can fill the gaps between the microporous corn starch molecules, and pectin can improve the overall viscosity of the starch film. Under the combined effect of filling and viscosity improvement, it supports the structure of the starch film and further improves the strength performance of the starch film.

[0028] 3. In the present invention, by adding tea tree essential oil in the preparation of starch film for inhibiting post-harvest fungi, the active ingredients contained in the tea tree essential oil can destroy the cell membrane structure of the fungus, thereby inhibiting the growth and reproduction of the fungus. The addition of erythritol can change the osmotic pressure around the microbial cells, inhibit the growth of microorganisms, and further enhance the antibacterial effect of the starch film. DETAILED DESCRIPTION

[0029] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0030] It should be noted that the raw materials used in the following examples are all commercially available raw materials.

[0031] Embodiment 1:

[0032] S1: Raw material preparation, the raw material is microporous corn starch, the microporous corn starch is pretreated to obtain a modified raw material, and the preparation method of the modified raw material includes:

[0033] 1) Drying treatment: the method of drying treatment is as follows: the microporous corn starch is scattered, spread flat and sent into an oven, the oven is set at 38°C and dried at 40°C to complete the drying treatment;

[0034] 2) Preparation of treatment liquid, the treatment liquid is prepared by the following method: disodium hydrogen phosphate dodecahydrate and deionized water are added into a beaker and mixed, the mass ratio of disodium hydrogen phosphate dodecahydrate to deionized water is 1:(4), citric acid is added after mixing, the mass of citric acid is 8% of the mass of deionized water, and after further mixing, the treatment liquid is prepared;

[0035] 3) Mixing reaction, the mixing reaction method is: the microporous corn starch and the treatment liquid are mixed in a water bath, the temperature is raised to 84°C, and the temperature is kept for 22 minutes. During the above-mentioned temperature keeping process, a stirring device is used to continuously stir, and the stirring device is set to 120r / min. After the temperature keeping reaction is completed, wait for the temperature to drop to 50°C, add amylase, the mass of amylase is equal to the mass of microporous corn starch, and the temperature is kept for 1 hour. After the temperature keeping reaction is completed, the temperature is raised to a boiling water state and kept for 2 hours to complete the mixing reaction and obtain the modified raw material;

[0036] S2: gelatinization treatment, the gelatinization treatment method is: the modified raw material and distilled water are mixed in a water bath, heated to 80°C, and kept warm for 12 minutes to obtain gelatinized starch, wherein the mass of distilled water is 20 times the mass of the modified raw material;

[0037] S3: preparing a mixture, wherein the mixture is a mixture of chitosan, sodium alginate, glycerol and acetic acid solution, the mass ratio of chitosan, sodium alginate, glycerol and acetic acid solution is 1:(0.6):(0.6):(40), and the mass of the mixture is 1.1 times the mass of gelatinized starch;

[0038] S4: Preparation of additives. The raw materials of the additives are composed of erythritol, lotus root starch, tea tree essential oil, turpentine and pectin. The mass ratio of erythritol, lotus root starch, tea tree essential oil, turpentine and pectin is 1:(0.2):(0.1):(0.4):(0.1). The additives are prepared by the following method: erythritol, lotus root starch, tea tree essential oil, turpentine and pectin are added into a mixer, and stirred at 120 r / min for 8 min. Then, distilled water is added, and the mass of the distilled water is 50% of the mass of the mixture in the mixer. The mixture is stirred at 320 r / min for 16 min to prepare the additives.

[0039] S5: Preparation of starch film, the preparation method of starch film comprises:

[0040] Step 1, preparation of film-forming liquid, the preparation method of film-forming liquid is as follows: gelatinized starch, mixed material and additive are added into a mixer, set to 220r / min stirring for 20min, the obtained mixture is homogenized and emulsified, the treatment pressure is 40MPa, the time is 20min, and then ultrasonic treatment is performed, the treatment power is 300W, the time is 20min, and the film-forming liquid is obtained;

[0041] Step 2, molding treatment, the film-forming liquid obtained in step 1 is subjected to molding treatment, and the molding treatment method is: the film-forming liquid is cast onto a polytetrafluoroethylene flat plate, sent into an oven, set at 40° C. for drying for 20 hours to obtain a film, and the film is placed in an environment with a temperature of 36° C. and a humidity of 30% for standing for 10 hours, and then packaged to obtain a starch film that inhibits post-harvest fungi.

[0042] Embodiment 2:

[0043] S1: Raw material preparation, the raw material is microporous corn starch, the microporous corn starch is pretreated to obtain a modified raw material, and the preparation method of the modified raw material includes:

[0044] 1) Drying treatment: the method of drying treatment is as follows: the microporous corn starch is scattered, spread flat and sent into an oven, the oven is set at 40°C and dried at 45°C to complete the drying treatment;

[0045] 2) Preparation of treatment liquid, the treatment liquid is prepared by the following method: disodium hydrogen phosphate dodecahydrate and deionized water are added into a beaker and mixed, the mass ratio of disodium hydrogen phosphate dodecahydrate to deionized water is 1:(5), citric acid is added after mixing, the mass of citric acid is 9% of the mass of deionized water, and after further mixing, the treatment liquid is prepared;

[0046] 3) Mixing reaction, the mixing reaction method is: the microporous corn starch and the treatment liquid are mixed in a water bath, the temperature is raised to 86°C, and the temperature is kept for 24 minutes. During the above-mentioned temperature keeping process, a stirring device is used to continuously stir, and the stirring device is set to 140r / min. After the temperature keeping reaction is completed, wait for the temperature to drop to 50°C, add amylase, the mass of amylase is equal to the mass of microporous corn starch, and the temperature is kept for 2 hours. After the temperature keeping reaction is completed, the temperature is raised to a boiling water state and kept for 3 hours to complete the mixing reaction and obtain the modified raw material;

[0047] S2: Gelatinization treatment. The gelatinization treatment method is as follows: the modified raw material is mixed with distilled water in a water bath, heated to 85°C, and kept warm for 14 minutes to obtain gelatinized starch, wherein the mass of the distilled water is 40 times the mass of the modified raw material;

[0048] S3: preparation of a mixture, wherein the mixture is a mixture of chitosan, sodium alginate, glycerol and acetic acid solution, the mass ratio of chitosan, sodium alginate, glycerol and acetic acid solution is 1:(0.7):(0.7):(50), and the mass of the mixture is 1.2 times the mass of gelatinized starch;

[0049] S4: Preparation of additives. The raw materials of the additives are composed of erythritol, lotus root starch, tea tree essential oil, turpentine and pectin. The mass ratio of erythritol, lotus root starch, tea tree essential oil, turpentine and pectin is 1:(0.3):(0.2):(0.5):(0.2). The additives are prepared by the following method: erythritol, lotus root starch, tea tree essential oil, turpentine and pectin are added into a mixer, and the stirring process is set at 140r / min for 10min. Then, distilled water is added, and the mass of the distilled water is 55% of the mass of the mixture in the mixer. The stirring process is set at 340r / min for 18min to prepare the additives.

[0050] S5: Preparation of starch film, the preparation method of starch film comprises:

[0051] Step 1, preparing the film-forming liquid. The preparation method of the film-forming liquid is as follows: gelatinized starch, mixed material and additives are added into a mixer, and stirred at 240 r / min for 25 min. The obtained mixture is homogenized and emulsified at a pressure of 50 MPa for 25 min, and then ultrasonically treated at a power of 350 W for 25 min to obtain the film-forming liquid.

[0052] Step 2, molding treatment, the film-forming liquid obtained in step 1 is molded, and the molding method is as follows: the film-forming liquid is cast onto a polytetrafluoroethylene plate, sent into an oven, set at 45° C. for drying for 25 hours to obtain a film, and the film is placed at a temperature of 38° C. and a humidity of 40% for 15 hours, and then packaged to obtain a starch film that inhibits post-harvest fungi.

[0053] Embodiment three:

[0054] S1: Raw material preparation, the raw material is microporous corn starch, the microporous corn starch is pretreated to obtain a modified raw material, and the preparation method of the modified raw material includes:

[0055] 1) Drying treatment: the method of drying treatment is as follows: the microporous corn starch is scattered, spread flat and sent into an oven, the oven is set at 42°C and dried at 50°C to complete the drying treatment;

[0056] 2) Preparation of treatment liquid, the treatment liquid is prepared by the following method: disodium hydrogen phosphate dodecahydrate and deionized water are added into a beaker and mixed, the mass ratio of disodium hydrogen phosphate dodecahydrate to deionized water is 1:(6), citric acid is added after mixing, the mass of citric acid is 10% of the mass of deionized water, and after further mixing, the treatment liquid is prepared;

[0057] 3) Mixing reaction, the mixing reaction method is as follows: the microporous corn starch and the treatment liquid are mixed in a water bath, the temperature is raised to 88° C., and the temperature is kept for 26 minutes. During the above-mentioned temperature keeping process, a stirring device is used to continuously stir, and the stirring device is set at 160r / min. After the temperature keeping reaction is completed, the temperature is cooled to 50° C., and amylase is added. The mass of amylase is equal to that of the microporous corn starch. The temperature is kept for 3 hours. After the temperature keeping reaction is completed, the temperature is raised to a boiling water state and kept for 4 hours to complete the mixing reaction and obtain the modified raw material;

[0058] S2: Gelatinization treatment. The gelatinization treatment method is as follows: the modified raw material is mixed with distilled water in a water bath, heated to 90°C, and kept warm for 16 minutes to obtain gelatinized starch, wherein the mass of the distilled water is 60 times the mass of the modified raw material;

[0059] S3: preparation of a mixture, wherein the mixture is a mixture of chitosan, sodium alginate, glycerol and acetic acid solution, the mass ratio of chitosan, sodium alginate, glycerol and acetic acid solution is 1:(0.8):(0.8):(60), and the mass of the mixture is 1.3 times the mass of gelatinized starch;

[0060] S4: Preparation of additives. The raw materials of the additives are composed of erythritol, lotus root starch, tea tree essential oil, turpentine and pectin. The mass ratio of erythritol, lotus root starch, tea tree essential oil, turpentine and pectin is 1:(0.4):(0.3):(0.6):(0.3). The additives are prepared by the following method: erythritol, lotus root starch, tea tree essential oil, turpentine and pectin are added into a mixer, and the stirring process is set at 160r / min for 12min. Then, distilled water is added, and the mass of the distilled water is 60% of the mass of the mixture in the mixer. The stirring process is set at 360r / min for 20min to prepare the additives.

[0061] S5: Preparation of starch film, the preparation method of starch film comprises:

[0062] Step 1, preparing the film-forming liquid. The preparation method of the film-forming liquid is as follows: gelatinized starch, mixed material and additives are added into a mixer, and stirred at 260 r / min for 30 min. The obtained mixture is homogenized and emulsified at a pressure of 60 MPa for 30 min, and then ultrasonically treated at a power of 400 W for 30 min to obtain the film-forming liquid.

[0063] Step 2, molding treatment, the film-forming liquid obtained in step 1 is subjected to molding treatment, and the molding treatment method is: the film-forming liquid is cast onto a polytetrafluoroethylene flat plate, sent into an oven, set at 50° C. for drying for 30 hours to obtain a film, and the film is placed at a temperature of 40° C. and a humidity of 50% for standing for 20 hours, and then packaged to obtain a starch film that inhibits post-harvest fungi.

[0064] Comparative Example 1: The difference between this comparative example and Example 1 is that this comparative example does not contain turpentine.

[0065] Comparative Example 2: The difference between this comparative example and Example 1 is that this comparative example does not contain tea tree essential oil.

[0066] Comparative Example 3: The difference between this comparative example and Example 1 is that this comparative example does not contain any additives.

[0067] Comparative Example 4: The difference between this comparative example and Example 1 is that the microporous corn starch is not pretreated in this comparative example.

[0068] Performance test: The performance of the starch films for inhibiting postharvest fungi prepared in Example 1, Example 2, Example 3, Comparative Example 1, Comparative Example 2, Comparative Example 3 and Comparative Example 4 was tested.

[0069] The test data obtained are recorded in the following table:

[0070]

[0071] Among them, the tensile strength properties of the starch films for inhibiting postharvest fungi prepared in Example 1, Example 2, Example 3, Comparative Example 1, Comparative Example 2, Comparative Example 3 and Comparative Example 4 were 25.3 MPa, 26.1 MPa, 25.4 MPa, 18.5 MPa, 18.4 MPa, 13.5 MPa and 12.1 MPa, respectively;

[0072] The elongation at break properties of the starch films for inhibiting postharvest fungi prepared in Example 1, Example 2, Example 3, Comparative Example 1, Comparative Example 2, Comparative Example 3 and Comparative Example 4 are 193.9%, 194.5%, 193.5%, 156.2%, 153.5%, 148.4% and 146.1%, respectively.

[0073] It can be seen that the tensile strength performance and elongation at break performance of the starch films for inhibiting postharvest fungi prepared in Comparative Examples 1, 2, 3 and 4 are lower than those in Examples 1, 2 and 3; this shows that: by pretreating the starch raw materials during the processing of the starch film for inhibiting postharvest fungi, the microporous corn starch can undergo an enzymatic hydrolysis reaction, and the microporous corn starch after the enzymatic hydrolysis reaction changes, its molecular chain shortens, the molecular weight decreases, and the molecular chain of the microporous corn starch becomes looser. In the subsequent film-forming treatment, the enzymatically improved microporous corn starch can be better combined with turpentine with a plasticizing function, so that the structure of the starch molecules is relatively stable during the plastic film-forming process, thereby effectively improving the strength performance of the starch film for inhibiting postharvest fungi.

[0074] By comparing and analyzing the relevant data in the table, it can be seen that the starch film for inhibiting postharvest fungi prepared by the present invention not only has good tensile strength, but also has excellent elongation at break performance. This shows that the method for preparing a starch film for inhibiting postharvest fungi provided by the present invention has a broader market prospect and is more suitable for promotion.

[0075] In the description of this specification, the description with reference to the terms "one embodiment", "example", "specific example", etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0076] The preferred embodiments of the present invention disclosed above are only used to help illustrate the present invention. The preferred embodiments do not describe all the details in detail, nor do they limit the invention to the specific implementation methods described. Obviously, many modifications and changes can be made according to the content of this specification. This specification selects and specifically describes these embodiments in order to better explain the principles and practical applications of the present invention, so that those skilled in the art can understand and use the present invention well. The present invention is limited only by the claims and their full scope and equivalents.

Claims

1. A method for preparing a starch film for inhibiting postharvest fungi, characterized in that: The following steps are involved: S1: Raw material preparation, wherein the raw material is microporous corn starch, and the microporous corn starch is pretreated to obtain a modified raw material. The preparation method of the modified raw material includes: 1) Drying treatment; 2) Preparation of treatment solution; 3) Mixing reaction to obtain modified raw materials; S2: gelatinization treatment, wherein the modified raw material is mixed with distilled water and heated to obtain gelatinized starch; S3: preparing a mixture, wherein the mixture is a mixture of chitosan, sodium alginate, glycerol and acetic acid solution; S4: preparing an additive, wherein the raw materials of the additive are composed of erythritol, lotus root starch, tea tree essential oil, turpentine and pectin, and the mass ratio of erythritol, lotus root starch, tea tree essential oil, turpentine and pectin is 1: (0.2-0.4): (0.1-0.3): (0.4-0.6): (0.1-0.3); S5: starch film preparation, the starch film preparation method comprising: Step 1: Preparation of film-forming solution; Step 2: Forming treatment: the film-forming liquid obtained in step 1 is subjected to forming treatment to obtain a starch film that inhibits post-harvest fungi.

2. The method for preparing a starch film for inhibiting postharvest fungi according to claim 1, characterized in that: The drying method is as follows: the microporous corn starch is broken up, spread flat and sent into an oven, the oven is set at 38-42° C. and dried at 40-50° C. to complete the drying process.

3. The method for preparing a starch film for inhibiting postharvest fungi according to claim 1, characterized in that: The treatment liquid is prepared by the following method: disodium hydrogen phosphate dodecahydrate and deionized water are added into a beaker and mixed, wherein the mass ratio of disodium hydrogen phosphate dodecahydrate to deionized water is 1:(4-6), citric acid is added after mixing, wherein the mass of the citric acid is 8-10% of the mass of the deionized water, and the treatment liquid is prepared after further mixing.

4. The method for preparing a starch film for inhibiting postharvest fungi according to claim 1, characterized in that: The mixing reaction method is as follows: the microporous corn starch and the treatment liquid are mixed in a water bath, the temperature is raised to 84-88° C., and the mixture is kept warm for 22-26 minutes. During the above-mentioned warming process, a stirring device is used to continuously stir, and the stirring device is set at 120-160 r / min. After the warming reaction is completed, the temperature is cooled to 50° C., and amylase is added. The mass of the amylase is equal to that of the microporous corn starch. The mixture is kept warm for 1-3 hours. After the warming reaction is completed, the temperature is raised to a boiling water state, and the mixture is kept warm for 2-4 hours to complete the mixing reaction and obtain the modified raw material.

5. The method for preparing a starch film for inhibiting postharvest fungi according to claim 1, characterized in that: The gelatinization treatment method is: the modified raw material is mixed with distilled water in a water bath, heated to 80-90° C., and kept warm for 12-16 minutes to obtain gelatinized starch, wherein the mass of the distilled water is 20-60 times the mass of the modified raw material.

6. The method for preparing a starch film for inhibiting postharvest fungi according to claim 1, characterized in that: The mass ratio of the chitosan, sodium alginate, glycerol and acetic acid solution is 1: (0.6-0.8): (0.6-0.8): (40-60), and the mass of the mixture is 1.1-1.3 times the mass of gelatinized starch.

7. The method for preparing a starch film for inhibiting postharvest fungi according to claim 1, characterized in that: The additive is prepared by the following method: the erythritol, lotus root powder, tea tree essential oil, turpentine and pectin are added into a mixer, the mixture is stirred at 120-160 r / min for 8-12 min, distilled water is added, the mass of the distilled water is 50-60% of the mass of the mixture in the mixer, the mixture is stirred at 320-360 r / min for 16-20 min, and the additive is prepared.

8. The method for preparing a starch film for inhibiting postharvest fungi according to claim 1, characterized in that: The preparation method of the film-forming liquid is as follows: gelatinized starch, mixed material and additives are added into a mixer, and stirred at 220-260 r / min for 20-30 min, the obtained mixture is homogenized and emulsified at a pressure of 40-60 MPa for 20-30 min, and then ultrasonically treated at a power of 300-400 W for 20-30 min to obtain the film-forming liquid.

9. The method for preparing a starch film for inhibiting postharvest fungi according to claim 1, characterized in that: The molding method is as follows: the film-forming liquid is cast onto a polytetrafluoroethylene plate, and then placed into an oven, and dried at 40 to 50° C. for 20 to 30 hours to obtain a film.

10. The method for preparing a starch film for inhibiting postharvest fungi according to claim 9, characterized in that: The film is placed in an environment with a temperature of 36-40°C and a humidity of 30-50% and allowed to stand for 10-20 hours, and then packaged to obtain a starch film capable of inhibiting post-harvest fungi.

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