A degradable packaging film for preserving fruits and vegetables and a preparation method and application thereof

Abstract

This invention discloses a biodegradable packaging film for preserving fruits and vegetables, its preparation method, and its application, belonging to the technical field of food packaging materials. The preparation of the biodegradable packaging film for preserving fruits and vegetables involves: dissolving chitosan in an acetic acid solution, adding soy protein isolate, adjusting the pH of the solution to 2-4, and stirring at 80-90°C to obtain a soy protein fiber solution; then adding plant essential oil to the soy protein fiber solution, stirring at high speed, and then adding konjac glucomannan solution, continuing stirring to obtain a film-forming solution. This solution is then poured onto a plate and dried to obtain the biodegradable packaging film for preserving fruits and vegetables. The biodegradable packaging film for preserving fruits and vegetables prepared by this invention is biodegradable, gas-barrier, antibacterial, antioxidant, and possesses strong mechanical properties. It can effectively maintain the freshness of packaged fruits and vegetables and can be used as a fruit and vegetable preservation packaging film to extend shelf life.

Description

Technical Field

[0001] This invention relates to a biodegradable packaging film for preserving fruits and vegetables, its preparation method and application, belonging to the field of food packaging materials technology. Background Technology

[0002] Fresh fruits and vegetables are prone to spoilage during storage and transportation, resulting in a serious waste of food resources. The spoilage of fresh foods such as fruits and vegetables involves processes such as microbial contamination and respiration. Reducing microbial invasion and decreasing respiration during preservation can extend the shelf life of most fruits. Low oxygen concentrations and low water content have been shown to slow down plant physiological metabolism and inhibit microbial proliferation.

[0003] Konjac glucomannan is a natural, bio-rich polysaccharide with biodegradability and biocompatibility, as well as excellent film-forming properties, making it an ideal food packaging material. However, existing technologies for preparing food preservation films using konjac glucomannan as the base film suffer from low mechanical strength and a lack of antioxidant and antibacterial properties. Adding functional fillers, such as natural active substances (plant polyphenols, organic essential oils) or nanoparticles, can enhance the antibacterial and antioxidant properties of food preservation films.

[0004] Plant essential oils are rich in phenols and terpenes, and are non-toxic, biodegradable natural antibacterial and antioxidant agents. Adding plant essential oils as functional fillers can enhance the antioxidant and antibacterial properties of plastic wrap. Current technology typically involves directly adding essential oils to the base film. However, direct addition of essential oils often leads to phase separation during film formation and disrupts the continuity of the matrix network, thereby reducing the cohesion of the base film and further degrading the mechanical properties of the plastic wrap. Summary of the Invention

[0005] [Technical Issues]

[0006] Existing preservation films based on konjac glucomannan have poor mechanical strength and lack antioxidant and antibacterial properties. While using plant essential oils as functional fillers can enhance the antioxidant and antibacterial properties of konjac glucomannan-based films to some extent, it usually leads to a further decline in the mechanical properties of the film.

[0007] [Technical Solution]

[0008] In view of the defects and deficiencies of the existing technology, the present invention provides a biodegradable packaging film for fruit and vegetable preservation, its preparation method and application. Specifically, it uses soybean protein fiber as a surfactant to improve the compatibility of konjac glucomannan and plant essential oils, while also improving the mechanical strength and barrier properties of the packaging film.

[0009] Chitosan-induced soy protein isolate forms soy protein fibers with a high aspect ratio and ordered fiber structure, exhibiting high emulsifying activity and emulsion stability indices, as well as high mechanical properties. Its stable essential oil emulsion can compensate for the loss of cohesion caused by the direct addition of essential oils. The essential oil emulsion stabilized by soy protein fibers simultaneously enhances the mechanical properties, barrier properties, and antioxidant and antibacterial properties of konjac glucomannan-based preservation films, reducing the oxygen content in the fruit and vegetable storage environment and inhibiting the growth of pathogenic microorganisms, thus achieving the purpose of preservation.

[0010] To achieve the above objectives, the following technical solution is provided:

[0011] This invention provides a method for preparing a biodegradable packaging film for preserving fruits and vegetables, the method comprising the following steps:

[0012] (1) Dissolve chitosan in acetic acid solution, add soy protein isolate, adjust the pH of the solution to 2-4, stir at 80-90℃ to obtain soy protein fiber solution;

[0013] (2) Dissolve konjac glucomannan in water, add plasticizer, stir well to obtain konjac glucomannan solution;

[0014] (3) Add plant essential oil to the soybean protein fiber solution obtained in step (1), stir at high speed, and then add it to the konjac glucomannan solution in step (2), continue stirring to obtain film-forming solution;

[0015] (4) Pour the film-forming liquid obtained in step (3) onto a flat plate and dry it to obtain a biodegradable packaging film for fruit and vegetable preservation.

[0016] In one embodiment, the acetic acid solution in step (1) is an aqueous solution of acetic acid with a volume fraction of 30-60%.

[0017] In one embodiment, the chitosan mass concentration in the solution of step (1) is 2-5%, and the soybean protein isolate mass concentration is 5-10%.

[0018] In one embodiment, the mass fraction of konjac glucomannan in the konjac glucomannan solution in step (2) is 0.5-1.2%.

[0019] In one embodiment, the mass fraction of the plasticizer in the konjac glucomannan solution in step (2) is 0.1-0.5%.

[0020] In one embodiment, the mass ratio of the plasticizer to konjac glucomannan in step (2) is 0.1 to 0.3:1.

[0021] In one embodiment, the plasticizer in step (2) includes one or more of glycerol, epoxidized soybean oil, citrate esters, and sorbitol.

[0022] In one embodiment, the stirring conditions in step (2) are: stirring at 40-60°C and 300-500 rpm for 2-24 hours.

[0023] In one embodiment, the plant essential oil in step (3) includes one or more of tea tree oil, cinnamon oil, thyme oil, oregano oil, and clove oil.

[0024] In one embodiment, the volume ratio of soybean protein fiber solution: plant essential oil: konjac glucomannan solution in step (3) is 2-10:1:100, wherein in the preparation of soybean protein fiber solution, the mass ratio of chitosan and soybean protein isolate is 2-5:5-10, and the mass fraction of konjac glucomannan in konjac glucomannan solution is 0.5-1.2%.

[0025] In one embodiment, the volume ratio of soybean protein fiber solution: plant essential oil: konjac glucomannan solution in step (3) is 2-10:1:100, wherein in the preparation of soybean protein fiber solution, the mass ratio of chitosan and soybean protein isolate is 2:5, and the mass fraction of konjac glucomannan in konjac glucomannan solution is 1%.

[0026] In one embodiment, the volume ratio of soybean protein fiber solution: plant essential oil: konjac glucomannan solution in step (3) is 2-5:1:100, wherein in the preparation of soybean protein fiber solution, the mass ratio of chitosan and soybean protein isolate is 2:5, and the mass fraction of konjac glucomannan in konjac glucomannan solution is 1%.

[0027] In one embodiment, the volume ratio of soybean protein fiber solution: plant essential oil: konjac glucomannan solution in step (3) is 4-5:1:100, preferably 4:1:100; wherein in the preparation of soybean protein fiber solution, the mass ratio of chitosan to soybean protein isolate is 2:5, and the mass fraction of konjac glucomannan in konjac glucomannan solution is 1%.

[0028] In one embodiment, the high-speed stirring conditions in step (3) are: 10,000 to 15,000 rpm for 3 to 5 minutes.

[0029] The present invention also provides a biodegradable packaging film for preserving fruits and vegetables prepared by the method described above.

[0030] In one embodiment, the biodegradable packaging film for preserving fruits and vegetables has an oxygen permeability of (4.62–4.79) g / (m·s·Kpa) and a water vapor permeability of (0.269–0.326) g·mm / (m 2 The tensile strength is 15.61 MPa to 35.02 MPa, and the elongation at break is 46.6% to 71.8%.

[0031] In one embodiment, the biodegradable packaging film for preserving fruits and vegetables has a DPPH radical scavenging rate of approximately 27%, a hydroxyl radical scavenging rate of approximately 21-25%, and an ABTS radical scavenging rate of 42-75%.

[0032] The present invention also provides the application of the above-described biodegradable packaging film for fruit and vegetable preservation in the field of food packaging.

[0033] Beneficial effects:

[0034] The biodegradable packaging film material for fruit and vegetable preservation provided by this invention specifically involves introducing a soybean protein fiber-stabilized plant essential oil emulsion into the preparation of food packaging film material, thereby preparing a biodegradable, gas-barrier, antibacterial, and antioxidant food packaging film that effectively maintains the freshness of packaged fruits and vegetables and can be used as a fruit and vegetable preservation packaging film to extend shelf life.

[0035] (1) Compared with pure konjac glucomannan packaging base film, the water vapor permeability and oxygen permeability of the packaging film prepared by the present invention are significantly reduced, indicating that it has strong barrier properties; among them, the water vapor permeability and oxygen permeability can be significantly reduced by 43.3% and 88.2%, respectively.

[0036] (2) Compared with pure konjac glucomannan packaging base film, the mechanical properties of the packaging film prepared by the present invention are significantly enhanced, wherein the tensile strength and elongation at break can be increased by 210.5% and 82.7%, respectively.

[0037] (3) Compared with pure konjac glucomannan packaging film, the packaging film prepared by the present invention has enhanced antioxidant and antibacterial properties. In particular, the total antioxidant capacity of the packaging film prepared by the present invention can reach 9.92 times that of pure konjac glucomannan packaging film, and it can also completely inhibit the growth of Escherichia coli and Staphylococcus aureus. Attached Figure Description

[0038] Figure 1 Transmission electron microscopy image of the soybean protein fiber solution prepared in this invention;

[0039] Figure 2 This is a transmission electron microscope image of the soybean protein isolate and chitosan complex of Comparative Example 2 of the present invention.

[0040] Figure 3This is a comparison chart of the antibacterial capabilities of different embodiments 1-4 of the present invention with Comparative Example 1;

[0041] Figure 4 This is a scanning electron microscope image of the surface of the packaging film prepared in Example 1 of the present invention;

[0042] Figure 5 This is a scanning electron microscope image of the surface of the packaging film prepared in Example 2 of the present invention;

[0043] Figure 6 This is a scanning electron microscope image of the surface of the packaging film prepared in Example 3 of the present invention;

[0044] Figure 7 This is a scanning electron microscope image of the surface of the packaging film prepared in Example 4 of the present invention. Detailed Implementation

[0045] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. The specific embodiments described below further illustrate the present invention.

[0046] The testing method involved in this invention:

[0047] 1. Oxygen permeability

[0048] Add 1g of activated carbon, 1.5g of sodium chloride, and 0.5g of reduced iron powder to a weighing bottle, seal it with packaging film, weigh it, and then place it in a desiccator under constant temperature and humidity (temperature 25±5℃, relative humidity = 90%). Measure the weight of the bottle after 48 hours and calculate the oxygen permeability using the following formula:

[0049]

[0050] In the formula, Δm(g) is the weight gain of the weighing bottle, t(h) is the test time, X(mm) is the thickness of the packaging film, and S(m 2 ) is the area of ​​the bottle opening.

[0051] 2. Water vapor transmission rate

[0052] Accurately weighed 3.0 ± 0.1 g of CaCl2 was spread evenly at the bottom of a weighing bottle, and the bottle opening was sealed with packaging film. The weighing bottle was then placed in a desiccator (temperature 25 ± 5℃, relative humidity 75 ± 5%), and the weight of each bottle was recorded after 24 hours. The water vapor transmission rate was calculated using the following formula:

[0053]

[0054] In the formula, Δm(g) is the weight gain of the weighing bottle, Δt(h) is the test time, X(mm) is the thickness of the packaging film, and A(m 2 ) represents the area of ​​the weighing bottle opening, and Δp (kPa) represents the water vapor pressure difference across the packaging film.

[0055] 3. Tensile strength and elongation at break

[0056] The testing procedure is as follows: Following the standard method of the American Society for Testing and Materials (ASTM), the packaging film was cut into strips of 10mm × 50mm, and the tensile strength and elongation at break of the packaging film were measured. The tensile strength and elongation at break were calculated using the following formulas:

[0057]

[0058] In the formula, F(N) is the tensile force when the packaging film breaks, T(mm) is the thickness of the packaging film, W(mm) is the width of the packaging film, L(mm) is the final length of the packaging film, and L0(mm) is the initial length of the packaging film.

[0059] 4. DPPH free radical scavenging ability test

[0060] Chop each membrane into small pieces, and mix 10 mg of each membrane with 1 mL of 0.1 mM DPPH solution. Prepare a separate blank control with the same DPPH solution, without any membrane added. After reacting in the dark for 30 minutes, measure the absorbance at 517 nm. Calculate the DPPH radical scavenging rate using the following formula:

[0061]

[0062] In the formula, A0 and A1 are the absorbance of each test sample and blank, respectively.

[0063] 5. Hydroxyl radical scavenging ability test

[0064] Chop each membrane into small pieces, and take 10 mg of each packaging membrane and mix them separately with 0.6 mL of salicylic acid ethanol solution (9 mM), 0.6 mL of FeSO4 aqueous solution (9 mM), and 0.6 mL of H2O2 solution (9.8 mM). Take another portion of the same mixture without adding any membrane as a blank control. After heating in a water bath at 37°C for 30 minutes, measure the absorbance at a wavelength of 510 nm. Calculate the hydroxyl radical scavenging rate using the following formula:

[0065]

[0066] In the formula, A c and A h These are the absorbance values ​​of each test sample and the blank, respectively.

[0067] 6. ABTS Free Radical Scavenging Capacity Test

[0068] A solution was prepared by mixing 7 mM ABTS and 2.45 mM K₂O₈S₂ in a 1:1 ratio. After standing for 12 hours, the solution was diluted with anhydrous ethanol to a absorbance of 0.70 ± 0.02 at 734 nm, yielding the ABTS working solution. Each membrane was shredded, and 10 mg of each packaged membrane was mixed with 10 mL of 0.1 mM ABTS working solution. A separate portion of the same ABTS working solution, without any membrane added, served as a blank control. After reacting in the dark for 30 minutes, the absorbance was measured at 734 nm. The ABTS radical scavenging rate was calculated using the following formula:

[0069]

[0070] In the formula, A b and A s These are the absorbance values ​​of each test sample and the blank, respectively.

[0071] 7. Antibacterial performance test

[0072] The testing procedure was as follows: Two typical bacteria—Gram-positive bacteria (Staphylococcus aureus) and Gram-negative bacteria (Escherichia coli)—were selected to test antibacterial activity. First, single colonies of Escherichia coli and Staphylococcus aureus were inoculated into sterile LB medium and shaken in a thermostat (37°C, 200 rpm) for 12 hours. Then, the medium was diluted with physiological saline to a concentration of 1×10⁻⁶. 7 CFU / mL. 400 mg of the packaging film was added to 20 mL of E. coli solution and 20 mL of Staphylococcus aureus solution, respectively, and incubated for 2 hours with magnetic stirring. After incubation at 37°C for 24 hours, the mixture was plated and the colony growth was observed and recorded.

[0073] Example 1

[0074] A method for preparing a biodegradable packaging film for preserving fruits and vegetables includes the following steps:

[0075] (1) Chitosan was dissolved in a 40% acetic acid solution, and soy protein isolate was added; wherein the chitosan concentration was 2 wt% and the soy protein isolate concentration was 5 wt%; the pH of the solution was adjusted to 2.0, and the solution was stirred at 85℃ for 8 hours to obtain a soy protein fiber solution. Figure 1 );

[0076] (2) Dissolve konjac glucomannan in deionized water, stir at 60℃ and 300 rpm for 6 h, add glycerol and continue stirring for 0.5 h to obtain konjac glucomannan solution; wherein, the mass fraction of konjac glucomannan is 1% and the mass fraction of glycerol is 0.3%;

[0077] (3) Take 2 mL of the soybean protein fiber solution prepared in step (1) and add 1 mL of tea tree essential oil. Stir at 10000 rpm for 3 minutes. Then add it to 100 mL of the konjac glucomannan solution in step (2) and stir at 10000 rpm for 5 minutes to obtain the film-forming solution.

[0078] (4) The film-forming liquid obtained in step (3) is poured onto a plate and dried at 40°C for 24 hours to obtain a packaging film.

[0079] Example 2

[0080] A method for preparing a biodegradable packaging film for preserving fruits and vegetables includes the following steps:

[0081] (1) Chitosan was dissolved in a 40% acetic acid solution and soy protein isolate was added; wherein the mass concentration of chitosan was 2 wt% and the mass concentration of soy protein isolate was 5 wt%; the pH of the solution was adjusted to 2.0 and stirred at 85°C for 8 h to obtain a soy protein fiber solution.

[0082] (2) Dissolve konjac glucomannan in deionized water, stir at 60℃ and 300 rpm for 6 h, add glycerol and continue stirring for 0.5 h to obtain konjac glucomannan solution; wherein, the mass fraction of konjac glucomannan is 1% and the mass fraction of glycerol is 0.3%;

[0083] (3) Take 3 mL of the soybean protein fiber solution prepared in step (1) and add 1 mL of tea tree essential oil. Stir at 10000 rpm for 3 minutes. Then add it to 100 mL of the konjac glucomannan solution in step (2) and stir at 10000 rpm for 5 minutes to obtain the film-forming solution.

[0084] (4) The film-forming liquid obtained in step (3) is poured onto a plate and dried at 40°C for 24 hours to obtain a packaging film.

[0085] Example 3

[0086] A method for preparing a biodegradable packaging film for preserving fruits and vegetables includes the following steps:

[0087] (1) Chitosan was dissolved in a 40% acetic acid solution and soy protein isolate was added; wherein the mass concentration of chitosan was 2 wt% and the mass concentration of soy protein isolate was 5 wt%; the pH of the solution was adjusted to 2.0 and stirred at 85°C for 8 h to obtain a soy protein fiber solution.

[0088] (2) Dissolve konjac glucomannan in deionized water, stir at 60℃ and 300 rpm for 6 h, add glycerol and continue stirring for 0.5 h to obtain konjac glucomannan solution; wherein, the mass fraction of konjac glucomannan is 1% and the mass fraction of glycerol is 0.3%;

[0089] (3) Take 4 mL of the soybean protein fiber solution prepared in step (1) and add 1 mL of tea tree essential oil. Stir at 10000 rpm for 3 minutes. Then add it to 100 mL of the konjac glucomannan solution in step (2) and stir at 10000 rpm for 5 minutes to obtain the film-forming solution.

[0090] (4) The film-forming liquid obtained in step (3) is poured onto a plate and dried at 40°C for 24 hours to obtain a packaging film.

[0091] Example 4

[0092] A method for preparing a biodegradable packaging film for preserving fruits and vegetables includes the following steps:

[0093] (1) Chitosan was dissolved in a 40% acetic acid solution and soy protein isolate was added; wherein the mass concentration of chitosan was 2 wt% and the mass concentration of soy protein isolate was 5 wt%; the pH of the solution was adjusted to 2.0 and stirred at 85°C for 8 h to obtain a soy protein fiber solution.

[0094] (2) Dissolve konjac glucomannan in deionized water, stir at 60℃ and 300 rpm for 6 h, add glycerol and continue stirring for 0.5 h to obtain konjac glucomannan solution; wherein, the mass fraction of konjac glucomannan is 1% and the mass fraction of glycerol is 0.3%;

[0095] (3) Take 5 mL of the soybean protein fiber solution prepared in step (1) and add 1 mL of tea tree essential oil. Stir at 10000 rpm for 3 minutes. Then add it to 100 mL of the konjac glucomannan solution in step (2) and stir at 10000 rpm for 5 minutes to obtain the film-forming solution.

[0096] (4) The film-forming liquid obtained in step (3) is poured onto a plate and dried at 40°C for 24 hours to obtain a packaging film.

[0097] Comparative Example 1

[0098] A method for preparing a biodegradable packaging film for preserving fruits and vegetables includes the following:

[0099] Konjac glucomannan was dissolved in deionized water and stirred at 60°C and 300 rpm for 6 hours. Glycerin was added and stirring was continued for 0.5 hours to form a film-forming solution, wherein the mass fraction of konjac glucomannan was 1% and the mass fraction of glycerin was 0.3%. The obtained film-forming solution was poured onto a plate and dried at 40°C for 24 hours to obtain a packaging film.

[0100] Comparative Example 2

[0101] A method for preparing a biodegradable packaging film for preserving fruits and vegetables includes the following:

[0102] (1) Chitosan was dissolved in a 40% acetic acid solution, and soy protein isolate was added, wherein the chitosan concentration was 2 wt% and the soy protein isolate concentration was 5 wt%. The mixture was stirred to obtain a soy protein isolate-chitosan complex. Figure 2 );

[0103] (2) Dissolve konjac glucomannan in deionized water, stir at 60℃ and 300 rpm for 6 h, add glycerol and continue stirring for 0.5 h to obtain konjac glucomannan solution; wherein, the mass fraction of konjac glucomannan is 1% and the mass fraction of glycerol is 0.3%;

[0104] (3) Take 4 mL of the soybean protein isolate-chitosan complex prepared in step (1) and add 1 mL of tea tree oil. Stir at 10,000 rpm for 3 minutes. Then add it to 100 mL of the konjac glucomannan solution in step (2) and stir at 10,000 rpm for 5 minutes to obtain the film-forming solution.

[0105] (4) The film-forming liquid obtained in step (3) is poured onto a plate and dried at 40°C for 24 hours to obtain a packaging film.

[0106] Comparative Example 3

[0107] A method for preparing a biodegradable packaging film for preserving fruits and vegetables includes the following:

[0108] (1) Chitosan was dissolved in a 40% acetic acid solution and soy protein isolate was added; wherein the mass concentration of chitosan was 2 wt% and the mass concentration of soy protein isolate was 5 wt%; the pH of the solution was adjusted to 2.0 and stirred at 85°C for 8 h to obtain a soy protein fiber solution.

[0109] (2) Dissolve konjac glucomannan in deionized water, stir at 60℃ and 300 rpm for 6 h, add glycerol and continue stirring for 0.5 h to obtain konjac glucomannan solution; wherein, the mass fraction of konjac glucomannan is 1% and the mass fraction of glycerol is 0.3%;

[0110] (3) Take 4 mL of the soybean protein fiber solution prepared in step (1), 100 mL of the konjac glucomannan solution in step (2) and 1 mL of tea tree essential oil, mix them, and stir at high speed at 10000 rpm for 5 minutes to obtain the film-forming solution.

[0111] (4) The film-forming liquid obtained in step (3) is poured onto a plate and dried at 40°C for 24 hours to obtain a packaging film.

[0112] Results Analysis

[0113] 1. The barrier properties of the packaging films prepared in Examples 1-4 and Comparative Examples 1-2 were tested, including oxygen permeability and water vapor permeability. The results are shown in Tables 1 and 2:

[0114] Table 1. Oxygen permeability of biodegradable packaging films for fruit and vegetable preservation prepared under different conditions.

[0115]

[0116] As shown in Table 1, the oxygen permeability of Examples 1 to 4 is lower than that of Comparative Example 1, indicating that the food packaging films prepared in Examples 1 to 4 have stronger oxygen barrier properties.

[0117] Table 2. Water vapor transmission rate of biodegradable packaging films for fruit and vegetable preservation prepared under different conditions.

[0118]

[0119] As shown in Table 2, the water vapor permeability of Examples 1 to 4 was significantly lower than that of Comparative Example 1 and Comparative Example 2, indicating that the food packaging film prepared by the present invention has stronger water vapor barrier properties.

[0120] 2. The packaging films prepared in Examples 1-4 and Comparative Examples 1-3 were subjected to mechanical property tests, including tensile strength and elongation at break. The results are shown in Table 3.

[0121] Table 3 Mechanical properties of biodegradable packaging films for fruit and vegetable preservation prepared under different conditions

[0122]

[0123] As shown in Table 3, the tensile strength and elongation at break of Examples 1-4 are significantly higher than those of Comparative Examples 1 and 2, indicating that the food packaging films prepared in Examples 1-4 have stronger mechanical properties. Meanwhile, although Comparative Example 3 has high tensile strength, it has almost no stretchability and is very brittle.

[0124] 3. The antioxidant properties of the packaging films prepared in Examples 1-4 and Comparative Example 1 were tested.

[0125] Three methods were used to test the antioxidant capacity of each packaging film: DPPH free radical scavenging capacity test, hydroxyl free radical scavenging capacity test, and ABTS free radical scavenging capacity test; the results are shown in Tables 4-6.

[0126] Table 4. DPPH free radical scavenging rate of biodegradable packaging films for fruit and vegetable preservation prepared under different conditions.

[0127]

[0128] Table 5. Hydroxyl radical scavenging rate of biodegradable packaging films for fruit and vegetable preservation prepared under different conditions.

[0129]

[0130] Table 6. ABTS radical scavenging rate of biodegradable packaging films for fruit and vegetable preservation prepared under different conditions.

[0131]

[0132] As shown in Tables 4-6, the packaging films prepared in Examples 1-4 have higher DPPH radical scavenging capacity, hydroxyl radical scavenging rate, and ABTS radical scavenging capacity than Comparative Example 1, indicating that the food packaging films prepared in Examples 1-4 have stronger antioxidant capacity.

[0133] 4. The antibacterial properties of the packaging films prepared in Examples 1-4 and Comparative Example 1 were tested.

[0134] The results are as follows Figure 3 As shown, by Figure 3 The results showed that the antibacterial ability of the packaging films prepared in Examples 1-4 against Escherichia coli and Staphylococcus aureus was significantly higher than that of Comparative Example 1, indicating that the food packaging films prepared in Examples 1-4 had stronger antibacterial ability.

[0135] The embodiments provided above are not intended to limit the scope of the invention, nor are the described steps intended to limit the order of execution. Any obvious modifications made to the invention by those skilled in the art based on existing common knowledge also fall within the scope of protection defined by the claims.

Claims

1. A method for preparing a biodegradable packaging film for preserving fruits and vegetables, characterized in that, The preparation method includes the following steps: (1) Dissolve chitosan in acetic acid solution, add soy protein isolate, adjust the pH of the solution to 2-4, stir at 80-90℃ to obtain soy protein fiber solution; The solution contains 2-5% chitosan by mass and 5-10% soybean protein by mass. (2) Dissolve konjac glucomannan in water, add plasticizer, and stir evenly to obtain konjac glucomannan solution; the mass fraction of konjac glucomannan in the konjac glucomannan solution is 0.5~1.2%; The mass ratio of the plasticizer to konjac glucomannan is 0.1~0.3:1; (3) Add plant essential oil to the soybean protein fiber solution obtained in step (1), stir at high speed, and then add it to the konjac glucomannan solution in step (2), and continue stirring to obtain a film-forming solution; The volume ratio of the soybean protein fiber solution: plant essential oil: konjac glucomannan solution is 2~10:1:100; (4) Pour the film-forming liquid obtained in step (3) onto a flat plate and dry it to obtain a biodegradable packaging film for preserving fruits and vegetables.

2. The preparation method according to claim 1, characterized in that, The plasticizer in step (2) includes one or more of glycerol, epoxidized soybean oil, citrate esters, and sorbitol.

3. The preparation method according to claim 1, characterized in that, The plant essential oils mentioned in step (3) include one or more of the following: tea tree oil, cinnamon oil, thyme oil, oregano oil, and clove oil.

4. The preparation method according to claim 1, characterized in that, The volume ratio of soybean protein fiber solution, plant essential oil and konjac glucomannan solution in step (3) is 2~5:1:

100. In the preparation of soybean protein fiber solution, the mass ratio of chitosan and soybean protein isolate is 2:5, and the mass fraction of konjac glucomannan in konjac glucomannan solution is 1%.

5. The biodegradable packaging film for preserving fruits and vegetables prepared by the preparation method according to any one of claims 1 to 4.

6. The application of the biodegradable packaging film for fruit and vegetable preservation as described in claim 5 in the field of food packaging.

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