Preparation method of antibacterial, edible and degradable composite film

Abstract

The invention relates to the technical field of films, in particular to a preparation method of a bacteriostatic, edible and degradable composite film, which comprises the following steps: S1, cellulose extraction: cleaning straws, crushing and sieving, adding 5% (W / W) NaOH solution according to a solid-to-liquid ratio of 1: (20-50), stirring in a water bath kettle at 80 DEG C, centrifuging at 8000rpm, stirring in the water bath kettle at 80 DEG C, centrifuging at 8000rpm, stirring in the water bath kettle at 75 DEG C, and filtering to obtain filtrate; the method comprises the following steps: (1) extracting cellulose by using wheat straw as a raw material so as to prepare CMC (Carboxymethyl Cellulose), so that value-added utilization of the straw can be realized; (2) the wheat straw based CMC-glycerol-PMA film is a novel antibacterial film, and is not reported; (3) the film is an edible and degradable film, and has the characteristics of being edible by a human body and having no pollution to the environment; and (4) the shelf life of fruits and vegetables can be effectively prolonged.

Description

Technical Field

[0001] The invention relates to the technical field of composite films, and in particular to a method for preparing an antibacterial, edible and degradable composite film. Background Art

[0002] my country produces a large amount of straw waste every year. Straw contains a large amount of cellulose, which can be made into cellulose ether derivatives, namely carboxymethyl cellulose (CMC), by replacing hydroxyl groups with carboxymethyl. This substance has the characteristics of strong film-forming ability and easy degradation, but does not have antibacterial properties. Polymalic acid (PMA) is an ester compound formed by the polymerization of malic acid, which has antibacterial, safe, non-toxic and degradable properties. In order to give CMC antibacterial properties, the present invention prepares a wheat straw-based carboxymethyl cellulose-glycerol-polymalic acid antibacterial, edible and degradable composite film.

[0003] As a major consumer of fruits and vegetables, my country suffers huge economic losses every year due to the problem of fruit and vegetable rot. Mechanical damage and microbial infection during transportation are the main reasons for the shortened shelf life of fruits and vegetables. Grapes, as a nutritious fruit containing bioactive compounds, are very susceptible to pathogen infection and mechanical damage and deterioration. At present, the methods used for grape preservation mainly include refrigeration preservation, atmosphere conditioning preservation, and preservation using plastic films. The above preservation methods have the disadvantages of high cost, high facility requirements, poor environmental protection and low safety, which not only bring potential harm to humans, but also cause great environmental pollution. Using composite films to coat grapes can not only reduce the consumption of grape fruit nutrients, effectively extend the shelf life of grapes, but also realize the high-value utilization of wheat straw and reduce environmental pollution. That is, the composite film prepared by the present invention has the characteristics of antibacterial, edible, and degradable, and has a good preservation effect on fruits and vegetables. Summary of the invention

[0004] The purpose of the present invention is to solve the shortcomings of the prior art and to propose a method for preparing an antibacterial, edible and degradable composite film.

[0005] In order to achieve the above object, the present invention adopts the following technical scheme: a method for preparing an antibacterial, edible and degradable composite film, comprising the following steps:

[0006] S1: Cellulose extraction, the straw is cleaned, crushed and sieved, 5% (W / W) NaOH solution is added according to the solid-liquid ratio of 1:20-50, placed in an 80°C water bath and stirred, then centrifuged at 8000 rpm, placed in an 80°C water bath and stirred, then centrifuged at 8000 rpm, then placed in a 75°C water bath and stirred, the obtained precipitate is washed with distilled water, and dried to obtain straw cellulose;

[0007] S2: Preparation of carboxymethyl cellulose, using the straw fiber obtained above as raw material to prepare carboxymethyl cellulose by solvent method;

[0008] S3: Preparation of antibacterial film, wheat straw-based carboxymethyl cellulose (2%-5%), glycerol (30%-50%) and polymalic acid (1%-3%) were used to prepare the film;

[0009] S4: The inhibitory effect of the antibacterial film on Escherichia coli and Bacillus subtilis. The cell morphology of Escherichia coli and Staphylococcus aureus was observed using a scanning electron microscope to determine the inhibitory effect of PMA on the two strains;

[0010] S5: Observe the surface and cross section of the prepared film using a scanning electron microscope;

[0011] S6: Fourier transform infrared spectroscopy measurement: the prepared film was measured using an infrared spectrometer, and the test wave number range was 4000-400cm -1 , scanning resolution is 4cm -1 , 32 scans were performed;

[0012] S7: Biodegradation determination, the film samples were placed on the soil surface in a tray, the tray was placed at room temperature, and photos were taken regularly every 7 days;

[0013] S8: Evaluation of the appearance and performance of the film. The prepared film was covered on white paper printed with a grape pattern, and it was observed that the film was colorless and transparent.

[0014] Preferably, the method further comprises comparing the appearance of the coated grapes, obtaining the coated grapes by the immersion method, and photographing the appearance of the coated grapes.

[0015] Preferably, the preservation effect of the coating treatment on grapes is also included, and the control group and the coating group grapes are stored at room temperature (26° C.) for 10 days to observe the changes in their appearance, and to measure their decay rate and weight loss rate.

[0016] Preferably, the stirring time in S1 is 2 hours, and the centrifugation time is 5 minutes.

[0017] Preferably, the size of the film sample of S7 is 10 cm×10 cm.

[0018] Preferably, the relative humidity of the soil in S7 is 85%.

[0019] Compared with the prior art, the advantages and positive effects of the present invention are:

[0020] In the present invention, (1) wheat straw is used as a raw material to extract cellulose and prepare CMC, thereby realizing the value-added utilization of straw; (2) the wheat straw-based CMC-glycerol-PMA film is a new type of antibacterial film, which has not been reported before; (3) the film is an edible and degradable film, which has the characteristics of being edible by humans and having no pollution to the environment; and (4) the shelf life of fruits and vegetables can be effectively extended. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 Schematic diagram of Escherichia coli and Staphylococcus aureus for the preparation method of the antibacterial, edible and degradable composite film proposed by the present invention;

[0022] Figure 2 The surface electron microscope image of the film of the method for preparing the antibacterial, edible and degradable composite film proposed by the present invention;

[0023] Figure 3 The cross-sectional electron microscope image of the method for preparing an antibacterial, edible and degradable composite film proposed by the present invention;

[0024] Figure 4 The infrared spectrum measurement diagram of the preparation method of the antibacterial, edible and degradable composite film proposed by the present invention;

[0025] Figure 5 A biodegradation determination diagram of a method for preparing an antibacterial, edible, degradable composite film proposed by the present invention;

[0026] Figure 6 The present invention provides a method for preparing an antibacterial, edible and degradable composite film, wherein the film is covered on a white paper with a grape pattern printed on it;

[0027] Figure 7 Figure 2 shows uncoated grapes and coated grapes for which the present invention proposes a method for preparing an antibacterial, edible and degradable composite film;

[0028] Figure 8 Observation diagram of grapes in the control group and the coating group of the method for preparing an antibacterial, edible and degradable composite film proposed by the present invention;

[0029] Fig. 9 A schematic diagram of the effect of the film on grapes in a method for preparing an antibacterial, edible and degradable composite film proposed in the present invention. DETAILED DESCRIPTION

[0030] In the description of the present invention, it should be understood that the terms "length", "width", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, in the description of the present invention, "multiple" means two or more, unless otherwise clearly and specifically defined.

[0031] See also Figure 1-8 , the present invention provides a technical solution: a method for preparing an antibacterial, edible and degradable composite film, S1: cellulose extraction, the straw is cleaned, crushed and sieved, 5% (W / W) NaOH solution is added according to a solid-liquid ratio of 1:20-50, placed in an 80°C water bath and stirred, then centrifuged at 8000rpm, placed in an 80°C water bath and stirred, then centrifuged at 8000rpm, then placed in a 75°C water bath and stirred, the obtained precipitate is washed with distilled water, and dried to obtain straw cellulose;

[0032] S2: Preparation of carboxymethyl cellulose, using the straw fiber obtained above as raw material to prepare carboxymethyl cellulose by solvent method;

[0033] S3: Preparation of antibacterial film, wheat straw-based carboxymethyl cellulose (2%-5%), glycerol (30%-50%) and polymalic acid (1%-3%) were used to prepare the film;

[0034] S4: The inhibitory effect of the antibacterial film on Escherichia coli and Bacillus subtilis. The cell morphology of Escherichia coli and Staphylococcus aureus was observed using a scanning electron microscope to determine the inhibitory effect of PMA on the two strains;

[0035] refer to Figure 1 , A: Escherichia coli; B: Staphylococcus aureus. The left picture shows the intact cell morphology, and the right picture shows the cell morphology after PMA treatment

[0036] Depend on Figure 1 It can be observed that PMA can destroy the cell structure of Escherichia coli and Staphylococcus aureus and has a good antibacterial effect on them.

[0037] S5: The surface and cross section of the prepared membrane were observed using a scanning electron microscope, referring to Figure 2 , the surface of the prepared membrane is smooth and flat, and the structure is dense;

[0038] S6: Fourier transform infrared spectroscopy, the prepared film was measured using an infrared spectrometer, and the test wave number range was 4000-400cm -1, scanning resolution is 4cm -1 , 32 scans were performed, and after analysis, it was found that the interactions between CMC, glycerol, and PMA in the film were connected by physical bonds;

[0039] S7: Biodegradation test: the film samples were placed on the soil surface in a tray, and the tray was placed at room temperature. Pictures were taken regularly every 7 days. It was found that the film could be completely degraded in 28 days, indicating that the film had good degradability.

[0040] S8: Appearance and performance evaluation of the film. The prepared film was covered on white paper printed with a grape pattern. The film was observed to be colorless and transparent. The mechanical properties and barrier properties of the film were measured. The TS of the film was 28.3-32.8MPa, the EB was 140.3-289.1%, and the WVP was 0.55-1.17*10 -12 g·m / m 2 ·s·Pa, PV is 8.44-10.09mmol / kg, which shows that the film has good mechanical properties and barrier properties and meets the conditions for being used as a film for preserving fruits and vegetables.

[0041] It also includes comparing the appearance of the coated grapes. The coated grapes are obtained by the immersion method and photographed. A is the uncoated grapes; B is the coated grapes. It is found that the coated grapes are crystal clear and have a good appearance.

[0042] It also includes the preservation effect of coating treatment on grapes. The control group and coating group grapes were stored at room temperature (26°C) for 10 days to observe their appearance changes, and their decay rate and weight loss rate were measured.

[0043] The stirring time in S1 is 2 h, and the centrifugation time is 5 min.

[0044] The size of the S7 film sample is 10 cm×10 cm.

[0045] The relative humidity of the soil in S7 is 85%

[0046] Through the above preparation method, cellulose is extracted from wheat straw as raw material to prepare CMC, which can realize the value-added utilization of straw; wheat straw-based CMC-glycerol-PMA film is a new type of antibacterial film, which has not been reported; the film is an edible and degradable film, which has the characteristics of being edible by humans and pollution-free to the environment; it can effectively extend the shelf life of fruits and vegetables.

[0047] The above are only preferred embodiments of the present invention and are not intended to limit the present invention in other forms. Any technician familiar with the profession may use the technical contents disclosed above to change or modify them into equivalent embodiments with equivalent changes and apply them to other fields. However, any simple modification, equivalent change and modification made to the above embodiments based on the technical essence of the present invention without departing from the technical solution of the present invention still falls within the protection scope of the technical solution of the present invention.

Claims

1. A method for preparing an antibacterial, edible, degradable composite film, comprising the following steps: S1: Cellulose extraction, the straw is cleaned, crushed and sieved, 5% (W / W) NaOH solution is added according to the solid-liquid ratio of 1:20-50, placed in an 80°C water bath and stirred, then centrifuged at 8000 rpm, placed in an 80°C water bath and stirred, then centrifuged at 8000 rpm, then placed in a 75°C water bath and stirred, the obtained precipitate is washed with distilled water, and dried to obtain straw cellulose; S2: Preparation of carboxymethyl cellulose, using the straw fiber obtained above as raw material to prepare carboxymethyl cellulose by solvent method; S3: Preparation of antibacterial film, wheat straw-based carboxymethyl cellulose (2%-5%), glycerol (30%-50%) and polymalic acid (1%-3%) were used to prepare the film; S4: The inhibitory effect of the antibacterial film on Escherichia coli and Bacillus subtilis. The cell morphology of Escherichia coli and Staphylococcus aureus was observed using a scanning electron microscope to determine the inhibitory effect of PMA on the two strains; S5: Observe the surface and cross section of the prepared film using a scanning electron microscope; S6: Fourier transform infrared spectroscopy measurement: the prepared film was measured using an infrared spectrometer, and the test wave number range was 4000-400cm -1 , scanning resolution is 4cm -1 , 32 scans were performed; S7: Biodegradation determination, the film samples were placed on the soil surface in a tray, the tray was placed at room temperature, and photos were taken regularly every 7 days; S8: Evaluation of the appearance and performance of the film. The prepared film was covered on white paper printed with a grape pattern, and it was observed that the film was colorless and transparent.

2. The method for preparing the antibacterial, edible and degradable composite film according to claim 1, characterized in that: It also includes comparing the appearance of coated grapes, obtaining coated grapes by immersion method, and taking photos of their appearance.

3. The method for preparing the antibacterial, edible and degradable composite film according to claim 1, characterized in that: It also includes the preservation effect of coating treatment on grapes. The control group and coating group grapes were stored at room temperature (26°C) for 10 days to observe their appearance changes, and their decay rate and weight loss rate were measured.

4. The method for preparing the antibacterial, edible and degradable composite film according to claim 1, characterized in that: The stirring time in S1 is 2 h, and the centrifugation time is 5 min.

5. The method for preparing the antibacterial, edible and degradable composite film according to claim 1, characterized in that: The size of the S7 film sample is 10 cm×10 cm.

6. The method for preparing the antibacterial, edible and degradable composite film according to claim 1, characterized in that: The relative humidity of the soil in S7 is 85%.

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