Preparation method of cellulose antibacterial cushion packaging material for fruits and vegetables and product

Abstract

The invention provides a preparation method of a cellulose antibacterial cushion packaging material for fruits and vegetables and a product. The preparation method comprises the following steps: (1) extracting cellulose from plant straws and / or leaf sheaths; (2) weighing cellulose and polyvinyl alcohol in a mass ratio of (1: 1)-(8: 1), uniformly mixing, adding distilled water of which the mass is 10-30 times that of the cellulose and the polyvinyl alcohol, dissolving and stirring to prepare mixed slurry; (3) adding sodium laurate accounting for 0.2%-1.0% of the mass of the cellulose and the polyvinyl alcohol and plant essential oil accounting for 3%-15% of the mass of the cellulose and the polyvinyl alcohol into the mixed slurry obtained in the step (2), and fully stirring to enable the cellulose and the polyvinyl alcohol to be uniformly dispersed in the mixed slurry; and (4) adding 0.5%-1.5% of sodium borate decahydrate into the mixed slurry obtained in the step (3), stirring and the like. The material disclosed by the invention not only has good buffer performance and can remarkably reduce mechanical damage of fruits and vegetables in the transportation process, but also can inhibit growth of microorganisms through natural antibacterial components and prolong the fresh-keeping period of the fruits and vegetables.

Description

Technical Field

[0001] This application belongs to the field of agricultural product storage and packaging. Specifically, this application provides a preparation method and product of a cellulose antibacterial buffer packaging material for fruits and vegetables. Background Art

[0002] In recent years, the development of e-commerce has significantly accelerated the growth of fresh fruit and vegetable logistics. Mechanical damage to fresh agricultural products during transportation is an important cause of post-harvest losses. During various links such as harvesting, logistics handling, grading and packaging, storage, transportation, and sales, fruits and vegetables are easily subjected to mechanical damage such as extrusion, dropping, collision, and friction, resulting in fruit deformation, peel and pulp damage, etc. Mechanical damage will directly cause the destruction of the cell structure at the damaged part of the fruit, leading to the loss of water and juice, and the rapid softening of the pulp tissue. At the same time, the generation of wounds accelerates the invasion of microorganisms into fruits and vegetables, resulting in fruit mildew, further reducing the quality of fruits and vegetables and causing a large amount of waste. Therefore, using buffer packaging is the main solution to reduce mechanical damage during fruit transportation. When fruits and vegetables are subjected to external forces such as impact and vibration during transportation and loading and unloading, by placing flexible buffer materials, the destructive energy generated by the external force during transmission to the fruit can be absorbed, thereby reducing fruit damage. Research also shows that implementing various buffer packagings for berries is an effective way to solve their transportation vibration damage.

[0003] Traditional buffer packaging mainly relies on petroleum-based materials such as polyurethane, polystyrene (PS), and polyethylene (PE). However, as is well known, these materials will cause waste accumulation and environmental pollution, having harmful effects on organisms and ecosystems. With the current enhancement of consumers' environmental awareness, people are becoming more and more interested in researching degradable buffer packaging materials. Currently, various biological materials, including polysaccharides, proteins, and polyesters, have been used in the preparation of bio-based degradable buffer materials. Cellulose is an important natural biological material derived from plants such as wood and straw. Cellulose has been widely used in the preparation of packaging materials due to its low cost, biodegradability, renewability, and abundance. Cellulose-based foam materials have great potential to replace traditional petroleum-based packaging materials and are often used as environmentally friendly packaging in the food industry. In China, about 900 million tons of plant straw and other waste are generated in the fields every year, and the burning ratio exceeds 30%, resulting in a large amount of pollutants and wasting resources. A large amount of cellulose is contained in plant straw waste. If cellulose is extracted from waste such as straw and leaf sheaths in advance, this will help reduce environmental pollution, realize the resource utilization of straw, replace traditional raw materials as a renewable resource, and alleviate the current shortage situation. Secondly, plant fiber packaging materials have good biodegradability and mechanical properties, with high strength and plasticity, and can meet different packaging requirements. Therefore, it is of great significance to develop cellulose-based materials with excellent buffer performance for the food packaging industry.

[0004] The main method for developing buffer materials is foaming, including chemical foaming, freeze casting, CO2 supercritical foaming, and mechanical foaming. However, due to chemical residues, time-consuming, and high costs, some of these technologies may not be suitable for practical applications. Mechanical foaming involves generating bubbles in a slurry through high-speed stirring and then performing hot air drying to remove moisture and form a porous structure. Compared with freeze drying and supercritical drying, this method uses water and air as foaming agents, making it safer, more environmentally friendly, and easier to operate in industrial production. However, when the connection points of the fiber network separate under mechanical stress, the integrity of the foam may be damaged, resulting in poor mechanical and water instability. Therefore, it is crucial to utilize various reinforcement methods, such as adding crosslinking agents or adding a second polymer, to improve the mechanical and buffer properties of cellulose foam materials.

[0005] Polyvinyl alcohol (PVA) is an environmentally friendly polymer with advantages such as good mechanical properties, non-toxicity, biodegradability, and biocompatibility. When used as a crosslinking agent, PVA can enhance the mechanical properties of packaging materials. Due to its abundant hydroxyl groups, PVA can form intermolecular hydrogen bonds with cellulose, significantly improving the mechanical properties of the composite material. By adding polyvinyl alcohol, the tensile strength and bending properties of cellulose materials can be enhanced, making them more suitable for the preparation of packaging products that require higher mechanical properties. Polyvinyl alcohol can improve the interfacial compatibility between cellulose and other polymers, enabling better bonding between different components. This good interfacial compatibility is one of the key factors ensuring the stability of the overall properties of the composite material. Summary of the Invention

[0006] Aiming at the problem that fruits and vegetables are easily damaged mechanically during the logistics process, resulting in spoilage and deterioration, the present invention provides a cellulose-based shock-absorbing packaging material with antibacterial function. This material not only has significant antibacterial properties, can inhibit the growth and reproduction of microorganisms, and maintain the quality of fruits and vegetables during the circulation process. It effectively absorbs and disperses external impact forces through physical foaming design, greatly reducing the damage to fruits and vegetables caused by mechanical stress, and achieving the effect of reducing post-harvest losses. It provides a green and degradable functional packaging material for maintaining the quality of fruits and vegetables during transportation. The material of the present invention is a dual-functional cellulose-based buffer packaging material infused with essential oils, which is made by extracting cellulose from by-products such as plant straws; this material aims to reduce vibration and antibacterial activity through mechanical foaming and PVA blend reinforcement. The developed cellulose-based packaging material shows great potential in the application of fruit and vegetable buffer packaging.

[0007] On the one hand, the present application provides a preparation method of a cellulose antibacterial buffer packaging material for fruits and vegetables, and the preparation method includes:

[0008] (1) Extract cellulose from plant straws and / or leaf sheaths;

[0009] (2) Weigh cellulose and polyvinyl alcohol with a mass ratio of 1:1 - 8:1, mix them evenly, add distilled water with a mass 10 - 30 times that of the mixture, dissolve and then stir to prepare a mixed slurry.

[0010] (3) Add sodium laurate accounting for 0.2% - 1.0% of the mass of cellulose and polyvinyl alcohol, and 3% - 15% of plant essential oil to the mixed slurry obtained in step (2), stir well to make them evenly dispersed in the mixed slurry.

[0011] (4) Add 0.5% - 1.5% of sodium borate decahydrate to the mixed slurry obtained in step (3), stir to make sodium borate decahydrate evenly distributed in the mixed slurry.

[0012] (5) Pour the slurry prepared from the mixed slurry obtained in step (4) into a mold, dry the mold containing the slurry to fully cure and form the slurry, and obtain a cellulose antibacterial buffer packaging material for fruits and vegetables.

[0013] Further, in step (2), weigh cellulose and polyvinyl alcohol with a mass ratio of 2:1 - 4:1, mix them evenly, add distilled water with a mass 15 - 20 times that of the mixture, dissolve and then stir for 5 - 20 min to prepare a mixed slurry.

[0014] Further, in step (3), add sodium laurate accounting for 0.5% - 0.8% of the mass of cellulose and polyvinyl alcohol, and 5% - 10% of plant essential oil to the mixed slurry obtained in step (2), stir well for 5 - 20 min to make them evenly dispersed in the mixed slurry.

[0015] Further, in step (4), add 0.8% - 1.2% of sodium borate decahydrate to the mixed slurry obtained in step (3), stir at 800 - 1000 rpm for 10 - 20 min after adding to make sodium borate decahydrate evenly distributed in the mixed slurry.

[0016] Further, in step (5), slowly pour the slurry prepared from the mixed slurry obtained in step (4) into a mold, place the mold containing the slurry in an oven, dry at 70 - 100 °C for 10 - 15 hours to fully cure and form the slurry, and obtain a cellulose antibacterial buffer packaging material for fruits and vegetables.

[0017] Further, in step (1), use the hydrothermal method to extract cellulose from plant straws and / or leaf sheaths.

[0018] Further, in step (1), dry the plant straws and / or leaf sheaths and then grind them into powder, add an equal - proportion mixture of 6% - 10% NaOH and 5% - 15% Na2SO3 according to a solid - liquid ratio of 1:4 - 1:20, heat and react at a temperature of 120 - 200 °C for 1 - 5 h, filter, wash with distilled water until neutral, and dry and store to obtain cellulose.

[0019] Further, in step (1), the plant straws and / or sheaths are dried and ground into powder, and an equal proportion mixture of 4%-8% NaOH and 5%-10% Na2SO3 is added according to a material-liquid ratio of 1:8 - 1:12. Then it is put into a pressure reactor and heated and reacted at a temperature of 140 - 180 °C for 1 - 3 h. After filtration, it is washed with distilled water until neutral, dried and stored to obtain cellulose.

[0020] The plant essential oil used in step (3) is preferably a mixture of allyl isothiocyanate and cinnamaldehyde, such as a mixture with a volume ratio of 1 - 2:1 - 2, and more preferably a mixture with a volume ratio of 1:1.

[0021] On the other hand, the present application provides a cellulose antibacterial buffer packaging material for fruits and vegetables prepared by the above preparation method.

[0022] On the other hand, the present application provides the application of the above cellulose antibacterial buffer packaging material for fruits and vegetables in the storage and / or transportation of fruits and vegetables.

[0023] The packaging material of the present application can be used for the transportation of various agricultural products such as fruits and vegetables that need to be fresh-preserved and buffered, not limited to the bayberries shown in the examples.

[0024] The beneficial effects of the present invention include:

[0025] Traditional buffer packaging has a single function and only has the effect of buffering and shock absorption. However, in this invention patent, natural plant essential oil is added as an antibacterial component to the buffer material. Through an emulsification technique, the mixture of allyl isothiocyanate and cinnamaldehyde is dispersed in polyvinyl alcohol, and in a slow-release manner, the natural essential oil is released into the packaging environment, effectively inhibiting the growth of microorganisms, enabling the material to have an antibacterial function, reducing the microbial infection caused by mechanical damage to fruits and vegetables, and maintaining the logistics quality of fruits and vegetables. In this material, allyl isothiocyanate and cinnamaldehyde used as antibacterial agents are both derived from natural plants, and have a synergistic antibacterial effect on Gram-negative / positive bacteria and fungi, making up for the problem of the narrow antibacterial spectrum of a single essential oil, and having high safety for the human body. Compared with chemical antibacterial agents, the essential oil antibacterial agent reduces the risk of food safety while ensuring the antibacterial property of the packaging material.

[0026] Cellulose, as an abundant organic polymer in nature, is usually regarded as the waste after crop harvesting. The main component of this invention, cellulose, is derived from plant wastes such as crop straws, leaf sheaths, etc. Through the hydrothermal extraction technology, cellulose is extracted from agricultural wastes and converted into a practical buffer packaging material, realizing the effective utilization of resources and reducing the environmental burden caused by agricultural wastes. It has far-reaching significance for promoting circular economy and sustainable development of resources. In addition, both cellulose and polyvinyl alcohol are degradable materials with good biodegradability. Compared with traditional petroleum-based packaging materials, the cellulose buffer packaging material can naturally degrade after use and will not cause long-term pollution to the environment. This characteristic makes the material of this invention an ideal choice to replace traditional petrochemical materials.

[0027] The buffer packaging material of this invention is prepared by mechanical foaming method. Compared with traditional extrusion and chemical foaming methods, it has the advantages of safety, greenness and simplicity. No chemical foaming agent is needed during the mechanical foaming process, avoiding the potential harm of chemical residues to the environment and human health. At the same time, the mechanical foaming operation is simple, avoiding the high-temperature and high-pressure preparation process and reducing the loss of antibacterial agents during the preparation process. In addition, the mechanical foaming technology can effectively control the density and structure of the foam, making the buffer material have better performance.

[0028] In terms of buffer performance, the material of this invention has significant advantages. Compared with traditional corrugated cardboard, the buffer coefficient of the material of this invention is reduced by about 50%, which means that when subjected to impact, the material can more effectively disperse and absorb energy, providing more reliable protection for the packaged contents. At the same time, the material of this invention has a high resilience rate, indicating that the material can quickly return to its original state after being compressed, maintaining the integrity and functionality of the structure, thus extending the service life of the material. In practical applications, this efficient buffer performance can provide more reliable protection for perishable items such as fruits and vegetables, significantly reducing the damage risk caused by vibration, collision or extrusion during transportation. Description of the Drawings

[0029] Figure 1 Showing the inhibitory effects of cellulose antibacterial buffer packaging on Penicillium citrinum (Part A) and Escherichia coli (Part B). Detailed Description of the Invention

[0030] Example 1 Material Preparation 1

[0031] Pulverize 30 g of water bamboo leaf sheaths, add an equal-volume mixture of 8% NaOH and 10% Na2SO3 according to a solid-liquid ratio of 1:8, put it into a pressure reactor, heat and react at 145 °C for 3 h, filter, wash with distilled water until neutral, dry and store to obtain cellulose. Weigh 6 g of cellulose and 3 g of polyvinyl alcohol, add 180 ml of distilled water, fully dissolve PVA and stir well for 10 min. Add 0.072 g of sodium laurate, 0.9 g of plant essential oil, stir at 500 rpm for 10 min, then add 0.1 g of sodium borate decahydrate, and continue to stir at 800 rpm for 20 min. Slowly pour the prepared slurry into a pre-prepared mold. Subsequently, place the mold containing the slurry in an oven and dry at 100 °C for 10 hours to fully cure and form the slurry, obtaining a cellulose antibacterial and shock-absorbing material. The plant essential oil is a 1:1 volume ratio mixture of allyl isothiocyanate and cinnamaldehyde (the same below).

[0032] Example 2 Material Preparation 2

[0033] Pulverize 30 g of water bamboo leaf sheaths, add an equal-volume mixture of 8% NaOH and 10% Na2SO3 according to a solid-liquid ratio of 1:10, put it into a pressure reactor, heat and react at 160 °C for 2 h, filter, wash with distilled water until neutral, dry and store to obtain cellulose. Weigh 6 g of cellulose and 2 g of polyvinyl alcohol, add 150 ml of distilled water, fully dissolve PVA and stir well for 10 min. Add 0.052 g of sodium laurate, 0.56 g of plant essential oil, stir at 500 rpm for 10 min, then add 0.08 g of sodium borate decahydrate, and continue to stir at 900 rpm for 15 min. Slowly pour the prepared slurry into a pre-prepared mold. Subsequently, place the mold containing the slurry in an oven and dry at 80 °C for 12 hours to fully cure and form the slurry, obtaining a cellulose antibacterial and shock-absorbing material.

[0034] Example 3 Material Preparation 3

[0035] Pulverize 30 g of water bamboo leaf sheaths, add an equal-volume mixture of 8% NaOH and 10% Na2SO3 according to a solid-liquid ratio of 1:12, put it into a pressure reactor, heat and react at 180 °C for 1 h, filter, wash with distilled water until neutral, dry and store to obtain cellulose. Weigh 8 g of cellulose and 2 g of polyvinyl alcohol, add 150 ml of distilled water, fully dissolve PVA and stir well for 10 min. Add 0.05 g of sodium laurate, 0.5 g of plant essential oil, stir well for 10 min, then add 0.08 g of sodium borate decahydrate, and continue to stir at 1000 rpm for 10 min. Slowly pour the prepared slurry into a pre-prepared mold. Subsequently, place the mold containing the slurry in an oven and dry at 70 °C for 15 hours to fully cure and form the slurry, obtaining a cellulose antibacterial and shock-absorbing material.

[0036] Example 4: Buffer performance test of the cellulose antibacterial buffer packaging of the present invention

[0037] Test method: Under a constant temperature environment of 25 °C, the static compression performance test was carried out on Example 3 (buffer material with a diameter of 80 mm and a thickness of 35 mm).

[0038] The static buffer coefficient of the example was calculated to be 5.44 through the stress-strain curve; when the deformation was 25%, the energy absorption was 3977 J / m 3 . It is proved that the cellulose antibacterial buffer packaging of the present invention has excellent buffer performance and can effectively absorb and disperse external impact forces. Tested by the same method, the static buffer coefficients of the materials of Example 1 and Example 2 were 5.86 and 5.52 respectively, and the energy absorption values were 3650 J / m 3 and 3860 J / m 3 .

[0039] Example 5: Antibacterial experiment of the cellulose antibacterial buffer packaging of the present invention

[0040] Test method: Penicillium citrinum and Escherichia coli were used as test objects. The Penicillium citrinum and Escherichia coli bacterial solutions were respectively spread in the center of the petri dish. A round hole with a diameter of 1 cm was punched from the cellulose antibacterial buffer material prepared in Example 1 using a sterile punch and placed in the center of the petri dish cover. The petri dish was inverted and placed in a biochemical incubator at 37 °C (Penicillium citrinum) and 28 °C (Escherichia coli) for 5 d (Penicillium citrinum) and 3 d (Escherichia coli) respectively.

[0041] The antibacterial results are shown in Figure 1 . The antibacterial zone diameters of the material of Example 1 against Penicillium citrinum and Escherichia coli reached 16.34 mm and 21.67 mm respectively. Tested by the same method, the materials of Example 2 and 3 also had similar antibacterial properties. It is proved that the cellulose antibacterial buffer packaging of the present invention has an obvious inhibitory effect on Penicillium citrinum and Escherichia coli.

[0042] Example 6: Application of the cellulose antibacterial buffer packaging of the present invention in the storage and transportation of waxberries

[0043] Test materials: Dongkui waxberries, purchased from Xianju, Zhejiang.

[0044] Test treatment: After precooling, select mature, non-rotten and uniform-sized fruits, divide them into three groups, with 40 waxberries in each group, and place them in portable plastic baskets respectively. The cellulose antibacterial buffer packaging prepared in Example 2 was placed at the bottom of the basket, and ordinary corrugated cardboard was used as the control group. The material sizes were all 300 mm × 200 mm × 10 mm. The two groups of samples were simultaneously placed on a vibration table to simulate the mechanical damage of waxberries during storage and transportation. After vibration, they were stored at 4 °C.

[0045] Compared with the two treatments, the rotting rates after 15 days of storage were: 44.45% for the example group and 88.13% for the control group. It is proved that the cellulose antibacterial buffer packaging of the present invention has a good fresh-keeping effect.

Claims

1. A preparation method of a cellulose antibacterial buffer packaging material for fruits and vegetables, characterized in that, The preparation method includes the following steps: (1) Extract cellulose from plant straws and / or leaf sheaths; (2) Weigh cellulose and polyvinyl alcohol at a mass ratio of 1:1 - 8:1, mix them evenly, add 10 - 30 times the mass of distilled water, stir after dissolution, and prepare a mixed slurry; (3) Add sodium laurate at 0.2% - 1.0% of the mass of cellulose and polyvinyl alcohol and 3% - 15% of plant essential oil to the mixed slurry obtained in step (2), and stir well to make them evenly dispersed in the mixed slurry; (4) Add 0.5% - 1.5% of sodium borate decahydrate to the mixed slurry obtained in step (3), and stir to make sodium borate decahydrate evenly distributed in the mixed slurry; (5) Pour the prepared slurry of the mixed slurry obtained in step (4) into a mold, dry the mold containing the slurry to fully cure and form the slurry, and obtain a cellulose antibacterial buffer packaging material for fruits and vegetables.

2. According to the preparation method described in claim 1, in step (2), weigh cellulose and polyvinyl alcohol at a mass ratio of 2:1 - 4:1, mix them evenly, add 15 - 20 times the mass of distilled water, stir for 5 - 20 min after dissolution, and thus prepare a mixed slurry.

3. According to the preparation method described in claim 1 or 2, in step (3), add sodium laurate at 0.5% - 0.8% of the mass of cellulose and polyvinyl alcohol and 5% - 10% of plant essential oil to the mixed slurry obtained in step (2), and stir well for 5 - 20 min to make them evenly dispersed in the mixed slurry.

4. According to the preparation method described in any one of claims 1 - 3, in step (4), add 0.8% - 1.2% of sodium borate decahydrate to the mixed slurry obtained in step (3), and stir at 800 - 1000 rpm for 10 - 20 min after addition to make sodium borate decahydrate evenly distributed in the mixed slurry.

5. According to the preparation method described in any one of claims 1 - 4, in step (5), slowly pour the prepared slurry of the mixed slurry obtained in step (4) into a mold, place the mold containing the slurry in an oven, dry at 70 - 100 °C for 10 - 15 hours to fully cure and form the slurry, and obtain a cellulose antibacterial buffer packaging material for fruits and vegetables.

6. According to the preparation method described in any one of claims 1 - 5, in step (1), dry the plant straws and / or leaf sheaths and grind them into powder, add an equal - proportion mixture of 6% - 10% NaOH and 5% - 15% Na2SO3 according to a solid - liquid ratio of 1:4 - 1:20, heat and react at a temperature of 120 - 200 °C for 1 - 5 h, filter, wash with distilled water until neutral, and dry and store to obtain cellulose.

7. According to the preparation method described in claim 6, in step (1), dry the plant straws and / or leaf sheaths and grind them into powder, add an equal - proportion mixture of 4% - 8% NaOH and 5% - 10% Na2SO3 according to a solid - liquid ratio of 1:8 - 1:12, put them into a pressure reactor, heat and react at a temperature of 140 - 180 °C for 1 - 3 h, filter, wash with distilled water until neutral, and dry and store to obtain cellulose.

8. According to the preparation method described in any one of claims 1-7, the plant essential oil used in step (3) is a mixture of allyl isothiocyanate and cinnamaldehyde in a volume ratio of 1-2:1-2, preferably a mixture of allyl isothiocyanate and cinnamaldehyde in a volume ratio of 1:

1.

9. A cellulose antibacterial buffer packaging material for fruits and vegetables prepared by using the preparation method described in any one of claims 1-8.

10. Application of the cellulose antibacterial buffer packaging material for fruits and vegetables according to claim 9 in the storage and / or transportation of fruits and vegetables.

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