A water-vapor-permeable, oxygen-permeable β-cyclodextrin polymer preservative film and a preparation method thereof

Abstract

The application discloses a kind of water vapor-permeable, oxygen-permeable β-cyclodextrin polymer preservative film and preparation method, adopt β-cyclodextrin-isoprene-styrene ternary polymer and β-cyclodextrin-acrylamide-styrene ternary polymer after film formation by mixing, both compounding, the preservative film prepared has good water vapor permeability, film is not easy to form water condensation bead, fruit and vegetable can also reduce excessive evaporation of moisture during storage, and the preservative film is good in oxygen permeability, will not cause internal anoxia during fruit and vegetable storage process, guarantee the basic physiological metabolism of fruit and vegetable during storage, important is that preservative film has excellent adsorption effect to hydrophobic bacteriostatic material, can achieve good mildew-proof preservation, reduce the enrichment and internal penetration of bacteriostatic drug on the surface of fruit and vegetable.The preparation method of the application is simple and practical.

Description

Technical Field

[0001] This invention relates to the field of food preservation film technology, and more specifically to a β-cyclodextrin polymer food preservation film that is permeable to water vapor and oxygen, and its preparation method. Background Technology

[0002] Preservation of fruits and vegetables has always been one of the challenges in agricultural product storage and preservation. Due to their high water content and rich nutrients, fruits and vegetables are easily infected by microorganisms, leading to spoilage and deterioration. In addition, the high physiological metabolic intensity of fruits and vegetables after harvest makes them prone to metabolic disorders due to poor ventilation in the storage environment, resulting in quality deterioration.

[0003] Currently, domestic fruits and vegetables are mainly stored using low-temperature controlled atmosphere storage and coating preservation methods. However, the outer packaging materials for these fruits and vegetables are either polyethylene film or no outer packaging film at all. The main problems with this storage method are that either the fruits and vegetables spoil due to the poor permeability of the outer packaging material to water vapor and oxygen, or the quality deteriorates significantly due to excessive moisture loss. Coating preservation also has the problem of preservative residues.

[0004] Therefore, it is necessary to develop a new type of fruit and vegetable preservation film that allows for the infusion of water vapor and oxygen permeability, which can help improve the quality of fruits and vegetables during preservation and reduce post-harvest losses.

[0005] β-Cyclodextrin is a type of cyclodextrin, a cyclic oligosaccharide produced by Bacillus cyclodextrin glucosyltransferase acting on starch. It consists of seven D-glucanose molecules linked by α-1,4 glycosidic bonds. Due to its hydrophobic lumen, β-cyclodextrin provides ideal sites for action, enabling it to encapsulate hydrophobic guests (inorganic and organic small molecules) of certain sizes and shapes to form host-guest inclusion complexes, making it a common carrier for various antibacterial drugs. Therefore, the first step is to prepare several polymers based on β-cyclodextrin and then use a solution coating method to prepare a steam-permeable, oxygen-permeable fruit and vegetable preservation film. Simultaneously, the molecular structure of β-cyclodextrin is utilized to achieve the adsorption of antibacterial drugs, thereby achieving antibacterial and antifungal effects. Summary of the Invention

[0006] In view of this, the present invention provides a β-cyclodextrin polymer preservation film that is permeable to water vapor and oxygen and a method for preparing the same.

[0007] To achieve the above objectives, the present invention adopts the following technical solution:

[0008] A method for preparing a β-cyclodextrin polymer food preservation film that is permeable to water vapor and oxygen includes the following steps:

[0009] (1) Mix β-cyclodextrin-isoprene-styrene terpolymer and β-cyclodextrin-acrylamide-styrene terpolymer, add tetrahydrofuran and shake to dissolve;

[0010] (2) After the solid is fully dissolved, centrifuge at 8000 r / min for 5 min at 20℃ to remove insoluble matter. Then take the supernatant, shake it, and let it stand for 30 min. Take the supernatant again and place it in a mold to evaporate and form a film at 30℃.

[0011] (3) The film-forming product is placed in a 40°C environment and dried for 4 hours to obtain a β-cyclodextrin polymer preservation film that is permeable to water vapor and oxygen.

[0012] Preferably, the mass ratio of the β-cyclodextrin-isoprene-styrene terpolymer to the β-cyclodextrin-acrylamide-styrene terpolymer is (2.5-4.5):(0.5-2.5), and the weight-volume ratio of the tetrahydrofuran to the total amount of the β-cyclodextrin-isoprene-styrene terpolymer and the β-cyclodextrin-acrylamide-styrene terpolymer is 0.1-0.24 g / mL.

[0013] Preferably, the preparation method of the β-cyclodextrin-isoprene-styrene terpolymer is as follows:

[0014] (3.1) Place β-cyclodextrin butenoate in a high-pressure explosion-proof bottle, add dimethyl sulfoxide, and stir to dissolve β-cyclodextrin butenoate;

[0015] (3.2) Add isoprene, styrene, and tert-butyl peroxide, tighten the cap, and stir in an oil bath at 500 r / min.

[0016] (3.3) After the reaction is complete, remove the high-pressure explosion-proof bottle and cool it to room temperature. Pour out the polymer that has been reacted and add pure water to stir and wash until there is no dimethyl sulfoxide residue in the water.

[0017] (3.4) After washing the polymer with water, add anhydrous ethanol to wash twice, then freeze in a refrigerator for 2 hours, take it out, put it in a grinder and add ethanol, stir and wash at 1000 r / min, repeat the washing operation 4-5 times, and then freeze dry in a freeze dryer to obtain β-cyclodextrin-isoprene-styrene terpolymer.

[0018] Preferably, the ratio of β-cyclodextrin butyl ester, dimethyl sulfoxide, isoprene, styrene, and tert-butyl peroxide is (5-15) g: 50 mL: (60-180) mmol: 240 mmol: 12 mmol.

[0019] Preferably, the reaction temperature in step (3.2) is 80-100℃ and the reaction time is 8-48h.

[0020] Preferably, in step (3.4), the vacuum degree of the freeze dryer is ≤100 Pa and the cold well temperature is -80°C; the gradient temperature rise program of the freeze dryer is as follows: -20°C for 2 hours, -10°C for 4 hours, 0°C for 10 hours, and finally rise to 20°C for 6 hours to complete the freeze drying.

[0021] Preferably, the preparation method of the β-cyclodextrin-acrylamide-styrene terpolymer is as follows:

[0022] (7.1) Place β-cyclodextrin butenoate in a high-pressure explosion-proof bottle, add dimethyl sulfoxide, and stir to dissolve β-cyclodextrin butenoate;

[0023] (7.2) Add acrylamide, styrene, and tert-butyl peroxide, tighten the cap, and stir in a 95°C oil bath at 500 r / min for 24 h;

[0024] (7.3) After removing the high-pressure explosion-proof bottle, cool it to room temperature, pour out the polymer that has completed the reaction, add pure water and stir to wash until there is no dimethyl sulfoxide residue in the water;

[0025] (7.4) After washing the polymer with water, add anhydrous ethanol to wash twice, then freeze in a refrigerator for 2 hours, take it out, put it in a grinder and add ethanol, stir and wash at 1000 r / min, repeat the washing operation 4-5 times, and then freeze dry in a freeze dryer to obtain β-cyclodextrin-acrylamide-styrene terpolymer.

[0026] Preferably, the ratio of β-cyclodextrin butyl ester, dimethyl sulfoxide, acrylamide, styrene, and tert-butyl peroxide is (5-15) g: 50 mL: 120 mmol: 240 mmol: 12 mmol.

[0027] Preferably, in step (7.4), the vacuum degree of the freeze dryer is ≤100 Pa and the cold well temperature is -80°C; the gradient temperature rise program of the freeze dryer is as follows: -20°C for 2 hours, -10°C for 4 hours, 0°C for 10 hours, and finally rise to 20°C for 6 hours to complete the freeze drying.

[0028] This invention also claims protection for the β-cyclodextrin polymer preservation film that is permeable to water vapor and oxygen, prepared by the preparation method described above.

[0029] As can be seen from the above technical solution, compared with the prior art, the present invention discloses a β-cyclodextrin polymer preservation film that is permeable to water vapor and oxygen and its preparation method, which has the following beneficial effects:

[0030] 1) Two new β-cyclodextrin polymers were synthesized, and a food preservation film was prepared by combining the two polymers;

[0031] 2) This plastic wrap has good water vapor permeability, and the film is not prone to forming water droplets, which can also reduce excessive moisture evaporation of fruits and vegetables during storage;

[0032] 3) This plastic wrap has good oxygen permeability, which will not cause internal oxygen deficiency in fruits and vegetables during storage, thus ensuring the basic physiological metabolism of fruits and vegetables during storage.

[0033] 4) The polymer film has an excellent adsorption effect on hydrophobic antibacterial substances (carbendazim, natamycin), which can achieve a good purpose of preventing mold and preserving freshness.

[0034] 5) The antibacterial drugs are adsorbed inside the plastic wrap, reducing the accumulation of antibacterial drugs on the surface of fruits and vegetables and their internal penetration. Attached Figure Description

[0035] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0036] Figure 1 The effect of reaction temperature on the synthesis of the β-cyclodextrin-isoprene-styrene terpolymer in Example 1;

[0037] Figure 2 The effect of the styrene / isoprene ratio on the synthesis of the β-cyclodextrin-isoprene-styrene terpolymer in Example 2;

[0038] Figure 3 The effect of β-cyclodextrin butenoate dosage on the synthesis of β-cyclodextrin-isoprene-styrene terpolymer in Example 3;

[0039] Figure 4 The effect of reaction time on the synthesis of the β-cyclodextrin-isoprene-styrene terpolymer in Example 4;

[0040] Figure 5 The adsorption capacity of β-cyclodextrin polymers for carbendazim and natamycin is shown in the graph.

[0041] Figure 6 Infrared chromatogram of the β-cyclodextrin-isoprene-styrene terpolymer;

[0042] Figure 7 The image shows the infrared chromatogram of the β-cyclodextrin-acrylamide-styrene terpolymer. Detailed Implementation

[0043] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0044] In the examples below, the β-cyclodextrin butenoate used was a β-cyclodextrin vinyl derivative prepared in the laboratory. Other suitable β-cyclodextrin vinyl derivatives can also be used in actual production. The initiator used in polymer preparation was tert-butyl peroxide.

[0045] The following examples were prepared using the preparation method disclosed in the specification.

[0046] Example 1

[0047] Weigh 5.0 g of β-cyclodextrin butenoate into a high-pressure explosion-proof bottle and dissolve it in 50 mL of dimethyl sulfoxide. Add 240 mmol of styrene, 60 mmol of isoprene, and 12 mmol of tert-butyl peroxide to the above solution. Place the reaction vessel in an oil bath and react at temperatures of 80, 85, 90, 95, and 100 °C for 24 hours.

[0048] Example 2

[0049] Weigh 5.0 g of β-cyclodextrin butenoate into a high-pressure explosion-proof bottle and dissolve it in 50 mL of dimethyl sulfoxide. The amounts of styrene and isoprene are as follows: styrene 240 mmol, isoprene 60 mmol; styrene 240 mmol, isoprene 100 mmol; styrene 240 mmol, isoprene 145 mmol; styrene 240 mmol, isoprene 180 mmol. The amount of tert-butyl peroxide is 12 mmol. The reaction vessel is placed in an oil bath, the reaction temperature is 95 °C, and the reaction time is 24 hours.

[0050] Example 3

[0051] Weigh 5.0, 7.5, 10.0, 12.5, and 15.0 g of β-cyclodextrin butenoate into high-pressure explosion-proof bottles and dissolve them in 50 mL of dimethyl sulfoxide. Add 240 mmol of styrene, 180 mmol of isoprene, and 12 mmol of tert-butyl peroxide to the solutions respectively. Place the reaction vessel in an oil bath, react at 95 °C for 24 hours.

[0052] Example 4

[0053] Weigh 15.0 g of β-cyclodextrin butenoate into a high-pressure explosion-proof bottle and dissolve it in 50 mL of dimethyl sulfoxide. Add 240 mmol of styrene, 180 mmol of isoprene, and 12 mmol of tert-butyl peroxide to the above solution. Place the reaction vessel in an oil bath and react at 95 °C for 8, 16, 24, 32, and 48 hours.

[0054] Example 5

[0055] Weigh 5.0, 10.0, and 15.0 g of β-cyclodextrin butenoate into high-pressure explosion-proof bottles, respectively, and dissolve them in 50 mL of dimethyl sulfoxide. Add 240 mmol of styrene, 120 mmol of acrylamide, and 12 mmol of tert-butyl peroxide to the solutions, respectively. Place the reaction vessel in an oil bath, react at 95 °C for 24 hours.

[0056] In the following examples, the water vapor and oxygen permeability effects were tested by a third-party testing agency for the β-cyclodextrin polymer plastic wrap in accordance with the requirements of GB / T 1037-2021 and GB / T 19789-2021.

[0057] Example 6

[0058] Weigh 4.5 g of β-cyclodextrin-isoprene-styrene terpolymer (polymer synthesis conditions: 15.0 g β-cyclodextrin butenoate, 240 mmol styrene, 180 mmol isoprene, 12 mmol tert-butyl peroxide, reaction temperature 95℃, reaction time 24 hours) and 0.5 g of β-cyclodextrin-acrylamide-styrene terpolymer (polymer synthesis conditions: 5.0 g β-cyclodextrin butenoate, 240 mmol styrene, 120 mmol acrylamide, 12 mmol tert-butyl peroxide, reaction temperature 95℃, reaction time 24 hours) and dissolve them in 30 mL of tetrahydrofuran. After centrifugation, take the supernatant, shake it, and let it stand for 30 min. Take 7.5, 10.0, and 15.0 mL of the supernatant respectively and evaporate it in a film-forming container at 30℃ to form a film. Place the film-forming product in a 40℃ environment and dry it for 4 h to obtain a β-cyclodextrin polymer preservation film that is permeable to water vapor and oxygen.

[0059] <![CDATA[Water vapor transmission rate g / (m 2 ·24h)]]> 17 18 48 34.6 <![CDATA[Oxygen permeability (cm 3 / (m 2 ·24 h·0.1 MPa))]]> 374 269 158 185

[0060] Example 7

[0061] Weigh 4.5 g of β-cyclodextrin-isoprene-styrene terpolymer (polymer synthesis conditions: 15.0 g β-cyclodextrin butenoate, 240 mmol styrene, 180 mmol isoprene, 12 mmol tert-butyl peroxide, reaction temperature 95℃, reaction time 24 hours) and 0.5 g of β-cyclodextrin-acrylamide-styrene terpolymer (polymer synthesis conditions: 10.0 g β-cyclodextrin butenoate, 240 mmol styrene, 120 mmol acrylamide, 12 mmol tert-butyl peroxide, reaction temperature 95℃, reaction time 24 hours) and dissolve them in 30 mL of tetrahydrofuran. After centrifugation, take the supernatant, shake it, and let it stand for 30 min. Take 7.5, 10.0, and 15.0 mL of the supernatant respectively and evaporate it in a film-forming container at 30℃ to form a film. Place the film-forming product in a 40℃ environment and dry it for 4 h to obtain a β-cyclodextrin polymer preservation film that is permeable to water vapor and oxygen.

[0062] <![CDATA[Water vapor transmission rate g / (m 2 ·24h)]]> 50 25 20 34.6 <![CDATA[Oxygen transmission rate cm 3 / (m 2 ·24h·0.1MPa)]]> 276 189 212 185

[0063] Example 8

[0064] Weigh 4.5 g of β-cyclodextrin-isoprene-styrene terpolymer (polymer synthesis conditions: 15.0 g β-cyclodextrin butenoate, 240 mmol styrene, 180 mmol isoprene, 12 mmol tert-butyl peroxide, reaction temperature 95℃, reaction time 24 hours) and 0.5 g of β-cyclodextrin-acrylamide-styrene terpolymer (polymer synthesis conditions: 15.0 g β-cyclodextrin butenoate, 240 mmol styrene, 120 mmol acrylamide, 12 mmol tert-butyl peroxide, reaction temperature 95℃, reaction time 24 hours) and dissolve them in 30 mL of tetrahydrofuran. After centrifugation, take the supernatant, shake it, and let it stand for 30 min. Take 7.5, 10.0, and 15.0 mL of the supernatant respectively and evaporate it in a film-forming container at 30℃ to form a film. Place the film-forming product in a 40℃ environment and dry it for 4 h to obtain a β-cyclodextrin polymer preservation film that is permeable to water vapor and oxygen.

[0065] <![CDATA[Water vapor transmission rate g / (m 2 ·24 h)]]> 22 19 23 34.6 <![CDATA[Oxygen permeability (cm 3 / (m 2 ·24 h·0.1 MPa))]]> 230 292 210 185

[0066] Adsorption effect of antibacterial drugs: 1.0 g of plastic wrap was broken and placed in an ethanol solution containing carbendazim and natamycin at concentrations of 500 μg / mL, 1000 μg / mL, and 1500 μg / mL. The volume of the antibacterial drug solution was 5 mL, and the adsorption time was 2 hours. The adsorption amount was calculated by the change in the concentration of the antibacterial drugs before and after adsorption. The results are attached. Figure 5 As shown.

[0067] Appendix Figure 6The image shows the infrared chromatogram of the terpolymer β-cyclodextrin-isoprene-styrene. The polymer synthesis conditions were: 15.0 g β-cyclodextrin butenoate, 240 mmol styrene, 180 mmol isoprene, 12 mmol tert-butyl peroxide, reaction temperature 95℃, and reaction time 24 hours.

[0068] Appendix Figure 7 The image shows the infrared chromatogram of the terpolymer β-cyclodextrin-acrylamide-styrene. The polymer synthesis conditions were: 15.0 g β-cyclodextrin butyl ester, 240 mmol styrene, 120 mmol acrylamide, 12 mmol tert-butyl peroxide, reaction temperature 95℃, and reaction time 24 hours.

[0069] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on its differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. For the apparatus disclosed in the embodiments, since it corresponds to the method disclosed in the embodiments, the description is relatively simple; relevant parts can be referred to the method section.

[0070] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for preparing a water vapor and oxygen permeable β-cyclodextrin polymer preservative film, characterized by, Includes the following steps: (1) Take β-cyclodextrin-isoprene-styrene terpolymer and β-cyclodextrin-acrylamide-styrene terpolymer, add tetrahydrofuran and shake to dissolve, the mass ratio of β-cyclodextrin-isoprene-styrene terpolymer to β-cyclodextrin-acrylamide-styrene terpolymer is (2.5-4.5):(0.5-2.5), and the weight-volume ratio of tetrahydrofuran to the total amount of β-cyclodextrin-isoprene-styrene terpolymer and β-cyclodextrin-acrylamide-styrene terpolymer is 0.1-0.24 g / mL; The preparation method of the β-cyclodextrin-isoprene-styrene terpolymer is as follows: (3.1) Place β-cyclodextrin butenoate in a high-pressure explosion-proof bottle, add dimethyl sulfoxide, and stir to dissolve β-cyclodextrin butenoate; (3.2) Add isoprene, styrene, and tert-butyl peroxide, tighten the cap, and stir in an oil bath at 500 r / min. (3.3) After the reaction is complete, remove the high-pressure explosion-proof bottle and cool it to room temperature. Pour out the polymer that has been reacted and add pure water to stir and wash until there is no dimethyl sulfoxide residue in the water. (3.4) After washing the polymer with water, add anhydrous ethanol to wash twice, then freeze in a refrigerator for 2 hours, take it out, put it in a grinder and add ethanol, stir and wash at 1000 r / min, repeat the washing operation 4-5 times, and then freeze dry in a freeze dryer to obtain β-cyclodextrin-isoprene-styrene terpolymer. The ratio of β-cyclodextrin butenoate, dimethyl sulfoxide, isoprene, styrene, and tert-butyl peroxide is: (5-15) g: 50 mL: (60-180) mmol: 240 mmol: 12 mmol; The preparation method of the β-cyclodextrin-acrylamide-styrene terpolymer is as follows: (7.1) Place β-cyclodextrin butenoate in a high-pressure explosion-proof bottle, add dimethyl sulfoxide, and stir to dissolve β-cyclodextrin butenoate; (7.2) Add acrylamide, styrene, and tert-butyl peroxide, tighten the cap, and stir in a 95°C oil bath at 500 r / min for 24 h; (7.3) After removing the high-pressure explosion-proof bottle, cool it to room temperature, pour out the polymer that has completed the reaction, add pure water and stir to wash until there is no dimethyl sulfoxide residue in the water; (7.4) After washing the polymer with water, add anhydrous ethanol to wash twice, then freeze in a refrigerator for 2 hours, take it out, put it in a grinder and add ethanol, stir and wash at 1000 r / min, repeat the washing operation 4-5 times, and then freeze dry in a freeze dryer to obtain β-cyclodextrin-acrylamide-styrene terpolymer. The ratio of β-cyclodextrin butenoate, dimethyl sulfoxide, acrylamide, styrene, and tert-butyl peroxide is (5-15) g: 50 mL: 120 mmol: 240 mmol: 12 mmol; (2) After the solid is fully dissolved, centrifuge at 8000 r / min for 5 min at 20℃ to remove insoluble matter. Then take the supernatant, shake it, and let it stand for 30 min. Take the supernatant again and place it in a mold to evaporate and form a film at 30℃. (3) The film-forming product is dried in an environment of 40°C for 4 hours to obtain a β-cyclodextrin polymer preservation film that is permeable to water vapor and oxygen.

2. The method for preparing a water vapor-permeable and oxygen-permeable β-cyclodextrin polymer preservation film according to claim 1, characterized in that, In step (3.2), the reaction temperature is 80-100℃ and the reaction time is 8-48h.

3. The method for preparing a water vapor-permeable and oxygen-permeable β-cyclodextrin polymer preservation film according to claim 1, characterized in that, In step (3.4), the vacuum degree of the freeze dryer is ≤100 Pa and the temperature of the cold well is -80°C. The gradient temperature rise program of the freeze dryer is as follows: -20°C for 2 hours, -10°C for 4 hours, 0°C for 10 hours, and finally rise to 20°C for 6 hours to complete the freeze drying.

4. The method for preparing a water vapor-permeable and oxygen-permeable β-cyclodextrin polymer preservation film according to claim 1, characterized in that, In step (7.4), the vacuum degree of the freeze dryer is ≤100 Pa and the cold well temperature is -80°C. The gradient temperature rise program of the freeze dryer is as follows: -20°C for 2 hours, -10°C for 4 hours, 0°C for 10 hours, and finally rise to 20°C for 6 hours to complete the freeze drying.

5. A β-cyclodextrin polymer preservation film that is permeable to water vapor and oxygen, prepared by the method according to any one of claims 1-4.

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