Fruit and vegetable modified atmosphere preservative paper and preparation method thereof
By using chitin and polyethylene glycol as raw materials and coating technology to prepare air conditioning fresh paper, the existing problems of high air conditioning packaging costs and environmental pollution are solved, and the low-cost and large-scale fruit and vegetable preservation effect is achieved.
Patent Information
- Application Number
- CN202510473097.6
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-04-16
- Publication Date
- 2025-08-22
AI Technical Summary
The existing air conditioning packaging technology is costly, complex in preparation, difficult to apply on a large scale, and has environmental pollution problems, which limits the popularity of fruits and vegetables preservation.
Chitin and polyethylene glycol are used as raw materials to prepare air-regulated fresh-preserving paper through coating technology, and the affinity of nanochitin is used to regulate gas permeability to achieve fresh-preservation of fruits and vegetables.
It is simple to prepare, low cost, can be produced on a large scale, and does not pollute the environment. It has good gas selection permeability and fresh preservation effect. It is suitable for fresh preservation of fruits and vegetables with different breathing strengths.
Smart Images
Figure CN120520113A_ABST
Abstract
Description
Technical Field
[0001] This article discloses a modified atmosphere fresh-keeping paper for fruits and vegetables and a preparation method thereof, which relates to a modified atmosphere fresh-keeping paper for fruits and vegetables prepared with biomass material, namely chitosan, as raw material, and belongs to the intersection of high value-added utilization of biomass resources and fruit and vegetable preservation technology. Background Art
[0002] According to the 2024 Food Waste Index Report, nearly one-fifth of all food produced globally is wasted or lost before it is consumed each year. Among all types of food waste, fruit and vegetable waste is the most prominent due to the lack of cost-effective, safe, and reliable preservation technologies and their perishable nature. Therefore, the development of fruit and vegetable preservation technologies is particularly important.
[0003] Modified atmosphere packaging (MAP) is widely recognized as one of the safest methods of preserving food, with significant preservation effects. However, current MAP technologies all have some problems. For example, MAP equipment, such as MAP warehouses, is expensive and difficult to popularize at the point of sale. Laser microporous MAP and silicon window MAP, on the other hand, have high costs, demanding membrane material requirements, and environmental pollution. Consequently, research on degradable MAP is increasing both domestically and internationally. These methods typically involve modifying biofilm materials such as proteins and polysaccharides, as well as degradable plastics such as polylactic acid, to form microporous structures or embed them into microporous materials, or by introducing groups such as amino groups, sulfonic acid groups, and ethoxy groups that react with carbon dioxide, thereby completing the design of MAP and achieving fruit and vegetable freshness preservation. However, these reactions are often complex processes, making large-scale production difficult, which limits the practical application of this technology. Therefore, developing a safe, reliable, low-cost, scalable, and sustainable paper-based MAP plays an important role in preserving fruit and vegetables. Summary of the Invention
[0004] In order to overcome the problems of modified atmosphere packaging mentioned in the above background technology, such as high cost, complex preparation, difficulty in large-scale application, and environmental pollution, the purpose of the present invention is to provide a modified atmosphere fresh-keeping paper for fruits and vegetables and a preparation method thereof. The present invention uses paper, chitin and polyethylene glycol as raw materials, has low cost and is biodegradable, and will not cause environmental problems. More importantly, the present invention adopts coating technology to prepare the modified atmosphere fresh-keeping paper, which is simple to prepare and can be produced on a large scale.
[0005] A modified atmosphere fresh-keeping paper for fruits and vegetables and a preparation method thereof. The raw materials of the modified atmosphere fresh-keeping paper for fruits and vegetables are: base paper, nano-chitin, and polyethylene glycol; the preparation method of the modified atmosphere fresh-keeping paper for fruits and vegetables comprises the following steps:
[0006] S1: preparing a coating liquid; adding 100-200 parts by weight of nano-chitin and 1-200 parts of polyethylene glycol to a stirred reactor, mixing at a temperature of 20-80°C and a stirring speed of 300-500 rpm. When the viscosity of the mixed liquid reaches 8000-42000 cps / 25°C, heating is stopped to obtain a crude coating liquid;
[0007] S2 coating liquid pretreatment: defoaming the crude coating liquid by ultrasonication, standing or centrifugation to obtain a refined coating liquid;
[0008] S3 coating: The refined coating liquid is coated on the surface of the base paper using a coating machine. The thickness of the coating liquid is 0.5mm to 3mm. The base paper coated with the coating liquid is then dried to obtain the modified atmosphere preservation paper for fruits and vegetables.
[0009] In some embodiments, the method for preparing nano-chitosan comprises the following steps:
[0010] S4: soaking 40 to 400 parts by weight of chitosan powder in 1 wt% to 10 wt% NaOH, mechanically stirring at 300 to 1000 rpm for 0.5 to 2 h at room temperature, and washing the chitosan suspension with deionized water until the pH is neutral to remove protein from the chitosan powder;
[0011] S5 then places the chitosan suspension in a 1wt% to 10wt% HCl solution, mechanically stirs at a speed of 300 to 1000 rpm at room temperature for 1 to 4 hours, and washes the reacted chitosan suspension with deionized water until the pH is neutral to remove minerals in the chitosan powder;
[0012] S6 then drying the chitosan obtained in S5 at 30-80° C. for 12-24 hours to obtain pure chitosan powder, further soaking the dried chitosan powder in 10wt%-70wt% NaOH, and adding 0.01%-0.1% w / v NaBH4 to the NaOH to prevent depolymerization of the chitosan, and mechanically stirring at 50-90° C. at a stirring speed of 300-1000 rpm for 2-6 hours to perform deacetylation treatment, and washing the partially deacetylated chitosan suspension with distilled water until it is neutral;
[0013] S7 then adds 0.5-2M acetic acid to adjust the pH of the deacetylated chitin suspension to 2-4, homogenizes, and finally obtains the nano-chitin solution, and tests its solid content.
[0014] In some embodiments, the polyethylene glycol can be a combination of one or more of polyethylene glycol 200, polyethylene glycol 300, polyethylene glycol 400, polyethylene glycol 600, polyethylene glycol 1000, polyethylene glycol 2000, polyethylene glycol 4000, polyethylene glycol 6000, polyethylene glycol 10000, and polyethylene glycol 20000.
[0015] In some embodiments, the specific ultrasonic treatment method in S2 is: ultrasonic treatment at 20-40° C. and an ultrasonic power of 200-800 W for 20-60 min.
[0016] In some embodiments, the specific treatment method of the standing still in S2 is: standing still at 4-30° C. for 12-48 hours.
[0017] In some embodiments, the specific treatment method of the centrifugation in S2 is: centrifugation at a speed of 1000-6000 rpm at 4-30° C. for 1-6 min.
[0018] In some embodiments, the specific drying treatment method in S3 is: drying temperature is 20-50° C., and drying time is 12-24 hours.
[0019] The present invention has the following advantages:
[0020] 1. The present invention utilizes a simple coating technology to prepare coated paper with modified atmosphere preservation function, and the coating technology can be used for large-scale production of products;
[0021] 2. The raw materials used in the present invention are all degradable and low-cost, will not cause environmental pollution, and have the potential for wide application;
[0022] 3. The modified atmosphere fresh-keeping paper prepared by the present invention can be recycled and re-made into paper, and has good recycling performance;
[0023] 4. The present invention utilizes the affinity of chitin and polyethylene glycol for carbon dioxide gas molecules to prepare modified atmosphere fresh-keeping paper with good carbon dioxide / oxygen gas selective permeability. By adjusting the coating thickness, the gas permeation rate can be controlled, thereby achieving the preservation of fruits and vegetables with different respiration intensities, with good preservation effect. BRIEF DESCRIPTION OF THE DRAWINGS
[0024] Figure 1 From left to right are nano-chitin prepared in Example 1, nano-chitin prepared in Example 2, and nano-chitin prepared in Example 3;
[0025] Figure 2 From left to right are uncoated base paper, modified atmosphere fresh-keeping paper for fruits and vegetables prepared in Example 5, modified atmosphere fresh-keeping paper for fruits and vegetables prepared in Example 6, and modified atmosphere fresh-keeping paper for fruits and vegetables prepared in Example 7;
[0026] Figure 3 From left to right are the microscopic surface structure of the uncoated base paper, the microscopic surface structure of the modified atmosphere fresh-keeping paper for fruits and vegetables prepared in Example 5, the microscopic surface structure of the modified atmosphere fresh-keeping paper for fruits and vegetables prepared in Example 6, and the microscopic surface structure of the modified atmosphere fresh-keeping paper for fruits and vegetables prepared in Example 7;
[0027] Figure 4 From left to right are the paper made from the modified atmosphere fresh-keeping paper for fruits and vegetables prepared in Example 5, the paper made from the modified atmosphere fresh-keeping paper for fruits and vegetables prepared in Example 6, and the paper made from the modified atmosphere fresh-keeping paper for fruits and vegetables prepared in Example 7. DETAILED DESCRIPTION
[0028] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the drawings, technical process steps, specific implementation conditions and materials in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.
[0029] Example 1
[0030] By weight, 40 parts of chitosan powder were immersed in 1 wt% NaOH and mechanically stirred at 300 rpm for 2 h at room temperature. The chitosan suspension after reaction was washed with deionized water until the pH was neutral to remove the protein in the chitosan powder. The chitosan suspension was then placed in a 1 wt% HCl solution and mechanically stirred at 300 rpm for 4 h at room temperature. The chitosan suspension after reaction was washed with deionized water until the pH was neutral to remove the minerals in the chitosan powder. The obtained chitosan was then dried at 30°C for 24 h to obtain pure chitosan powder. The dried chitosan powder was further immersed in 10 wt% NaOH and 0.01% w / v HBr was added to the NaOH. NaBH4 was added to prevent chitin from depolymerizing. The mixture was mechanically stirred at 300 rpm for 6 h at 50°C. The partially deacetylated chitin suspension was washed with distilled water until it was neutral. 0.5 M acetic acid was then added to adjust the pH of the deacetylated chitin suspension to 2-4. The mixture was homogenized to obtain a nano-chitosan solution. The solid content of the solution was 0.72 wt %. The prepared nano-chitosan was characterized by scanning electron microscopy. Figure 1 As shown in middle a, nano-chitosan is in the shape of a long column with a length of 100 to 700 nm and a width of 5 to 17 nm.
[0031] Example 2
[0032] 40 to 400 parts by weight of chitosan powder are immersed in 1 wt% to 10 wt% NaOH, mechanically stirred at 300 to 1000 rpm for 0.5 to 2 h at room temperature, and the chitosan suspension after the reaction is washed with deionized water until the pH is neutral to remove the protein in the chitosan powder; the chitosan suspension is then placed in a 1 wt% to 10 wt% HCl solution, mechanically stirred at 300 to 1000 rpm for 1 to 4 h at room temperature, and the chitosan suspension after the reaction is washed with deionized water until the pH is neutral to remove the minerals in the chitosan powder; the chitosan obtained in S5 is then dried at 30 to 80°C for 12 to 24 h. , obtaining pure chitosan powder, further soaking the dried chitosan powder in 10wt% to 70wt% NaOH, and adding 0.01% to 0.1% w / v NaBH4 to the NaOH to prevent chitosan from depolymerizing, and mechanically stirring at 50 to 90°C and 300 to 1000 rpm for 2 to 6 hours for deacetylation, and washing the partially deacetylated chitosan suspension with distilled water to neutrality; then adding 0.5 to 2M acetic acid to adjust the pH of the deacetylated chitosan suspension to 2 to 4, and homogenizing to finally obtain a nano-chitosan solution, the solid content of which was 0.76wt%; the prepared nano-chitosan was characterized by scanning electron microscopy, and the results are as follows: Figure 1 As shown in b, the nano-chitosan is in the shape of a long column with a length of 100 to 800 nm and a width of 6 to 20 nm.
[0033] Example 3
[0034] 40 to 400 parts by weight of chitosan powder are immersed in 1 wt% to 10 wt% NaOH, mechanically stirred at 300 to 1000 rpm for 0.5 to 2 h at room temperature, and the chitosan suspension after the reaction is washed with deionized water until the pH is neutral to remove the protein in the chitosan powder; the chitosan suspension is then placed in a 1 wt% to 10 wt% HCl solution, mechanically stirred at 300 to 1000 rpm for 1 to 4 h at room temperature, and the chitosan suspension after the reaction is washed with deionized water until the pH is neutral to remove the minerals in the chitosan powder; the chitosan obtained in S5 is then dried at 30 to 80°C for 12 to 24 h. , obtaining pure chitosan powder, further soaking the dried chitosan powder in 10wt% to 70wt% NaOH, and adding 0.01% to 0.1% w / v NaBH4 to the NaOH to prevent chitosan from depolymerizing, and mechanically stirring at 50 to 90°C at a stirring speed of 300 to 1000 rpm for 2 to 6 hours for deacetylation, and washing the partially deacetylated chitosan suspension with distilled water to neutrality; then adding 0.5 to 2M acetic acid to adjust the pH of the deacetylated chitosan suspension to 2 to 4, and homogenizing to finally obtain a nano-chitosan solution, the solid content of which was tested to be 0.79wt%. The prepared nano-chitosan was characterized by scanning electron microscopy, and the results are as follows: Figure 1 As shown in middle c, nano-chitosan is in the shape of a long column with a length of 100 to 900 nm and a width of 7 to 23 nm.
[0035] Example 4
[0036] The deacetylation degree of the nano-chitin samples prepared in Examples 1 to 3 was determined using a conductivity meter in combination with a pH meter. 25 g of nano-chitin suspension was weighed and the mass of the nano-chitin was calculated based on the solid content described in the examples. Standard solutions of 1 mol / L HCl and 0.1 mol / L NaOH were then prepared respectively. HCl solution (1 M) was then added dropwise to the nano-chitin suspension until the pH value dropped to <2, and the resulting suspension was stirred for 24 hours to completely protonate the surface groups. NaOH solution (0.1 M) was added to the protonated nano-chitin suspension at 100 microliters each time, and the conductivity and pH values were measured after mixing. During the titration process, the changes in the conductivity and pH values of the solution and the volume of the NaOH standard solution consumed were recorded, and the titration volume of the NaOH standard solution was plotted against the conductivity and pH values of the solution to obtain conductivity-V NaOH and pH-V NaOH Titration curve. The curve is pH versus V NaOH The first derivative curve is ΔpH-ΔV NaOH Double jump titration curve. According to the definition of deacetylation degree, the deacetylation degree is calculated according to the following formula:
[0037]
[0038] Where DD (%) is the degree of deacetylation, m is the mass of deacetylated chitin; V1 and V2 represent the volumes consumed by 0.1 mol / L NaOH at the two inflection points, respectively; c represents the NaOH concentration; and each sample was tested three times and the average value was taken. The degree of deacetylation described in this patent is the average of the deacetylation values calculated using conductivity and pH. The degrees of deacetylation of the nano-chitin prepared in Examples 1, 2, and 3 were 30.8%, 32.8%, and 34.7%, respectively.
[0039] Example 5
[0040] By weight, 100 parts of polyethylene glycol 10000 were added to 100 parts of the nano-chitin suspension prepared in Example 1, and the reaction was stirred at a temperature of 25 ° C and a stirring speed of 500 rpm until the viscosity of the mixed solution was 8000-42000 cps / 25 ° C, and the reaction was stopped to obtain a crude coating liquid; the crude coating liquid was treated at 25 ° C and an ultrasonic power of 600 W for 40 minutes to obtain a refined coating liquid; the refined coating liquid was applied to the surface of the base paper to a thickness of 1.5 mm and dried at 25 ° C for 24 hours to obtain a modified atmosphere fresh-keeping paper for fruits and vegetables, the optical photograph of which is as shown. Figure 2 As shown in b, the scanning electron microscope microscopic picture is as follows Figure 3 As shown in a, the optical photograph of the paper that was remade after use is as shown in Figure 4 As shown in a.
[0041] Example 6
[0042] By weight, 200 parts of polyethylene glycol 20000 were added to 200 parts of the nano-chitin suspension prepared in Example 2, and the mixture was stirred at a temperature of 50 ° C and a stirring speed of 400 rpm until the viscosity of the mixture was 8000-42000 cps / 25 ° C, and the reaction was stopped to obtain a crude coating liquid; the crude coating liquid was allowed to stand at 30 ° C for 30 h to obtain a refined coating liquid; the refined coating liquid was applied to the surface of the base paper to a thickness of 2 mm, and dried at 35 ° C for 18 hours to obtain a modified atmosphere fresh-keeping paper for fruits and vegetables, the optical photograph of which is as shown. Figure 2 As shown in c, the scanning electron microscope microscopic picture is as follows Figure 3 As shown in b, the optical photograph of the paper that was remade after use is as shown in Figure 4 As shown in b.
[0043] Example 7
[0044] By weight, 150 parts of polyethylene glycol 20000 were added to 150 parts of the nano-chitin suspension prepared in Example 2, and the reaction was stirred at a temperature of 80 ° C and a stirring speed of 300 rpm until the viscosity of the mixture was 8000-42000 cps / 25 ° C, and the reaction was stopped to obtain a crude coating liquid; the crude coating liquid was centrifuged at 15 ° C and 25 ° C at a speed of 3000 rpm for 3 min to obtain a refined coating liquid; the refined coating liquid was applied to the surface of the base paper to a thickness of 3 mm and dried at 25 ° C for 18 hours to obtain a modified atmosphere preservation paper for fruits and vegetables, the optical photograph of which is as shown. Figure 2 d, the scanning electron microscope microscopic picture is as follows Figure 3 c shows an optical photograph of the paper that was remade after use. Figure 4 As shown in c.
[0045] Example 8
[0046] The performance tests of the modified atmosphere fresh-keeping paper for fruits and vegetables prepared in Examples 5 to 7 were conducted, mainly including thickness, carbon dioxide permeability, oxygen permeability, water vapor permeability, water contact angle, tensile stress and tensile strain. The results are shown in Table 1.
[0047] Table 1 Performance of modified atmosphere fresh-keeping paper for fruits and vegetables prepared in Examples 5 to 7
[0048]
[0049]
[0050] Example 9
[0051] The modified atmosphere fresh-keeping paper for fruits and vegetables prepared in Examples 5 to 7 was applied to a litchi preservation test. The specific method was as follows: the surface moisture of purchased fresh litchi was dried with absorbent paper, and then the litchi was wrapped with the modified atmosphere fresh-keeping paper prepared in Examples 5 to 7 and the base paper, respectively. The weight loss of the litchi was tested after 8 days. Three parallel experiments were conducted for each sample in the entire experiment, and the litchi was placed in air as a blank experiment. The test results are shown in Table 2.
[0052] Table 2 Physical and chemical indicators of litchi after storage for 8 days
[0053]
[0054] The above results show that the modified atmosphere fresh-keeping paper for fruits and vegetables prepared in Examples 5 to 7 have good fresh-keeping effects and can effectively maintain the weight of litchi. Among them, the modified atmosphere fresh-keeping paper for fruits and vegetables prepared in Example 7 has the best effect, which can provide guidance for practical application production.
[0055] Technical personnel should note: Although the present invention has been described according to the above specific implementation methods, the inventive concept of the present invention is not limited to this invention. Any modification using the inventive concept will be included in the scope of protection of this patent.
Claims
1. A modified atmosphere fresh-keeping paper for fruits and vegetables and a preparation method thereof, characterized in that: The raw materials of the modified atmosphere fresh-keeping paper for fruits and vegetables are: base paper, nano-chitin, and polyethylene glycol; the preparation method of the modified atmosphere fresh-keeping paper for fruits and vegetables comprises the following steps: S1: preparing a coating solution; adding 100-200 parts by weight of nano-chitin and 1-200 parts of polyethylene glycol to a stirred reactor, mixing at a temperature of 20-80°C and a stirring speed of 300-500 rpm. When the viscosity of the mixed solution is 8000-42000 cps / 25°C, heating is stopped to obtain a crude coating solution; S2 coating liquid pretreatment: defoaming the crude coating liquid by ultrasonication, standing or centrifugation to obtain a refined coating liquid; S3 coating: The refined coating liquid is coated on the surface of the base paper using a coating machine. The thickness of the coating liquid is 0.5 mm to 3 mm. The base paper coated with the coating liquid is then dried to obtain the modified atmosphere preservation paper for fruits and vegetables.
2. A modified atmosphere fresh-keeping paper for fruits and vegetables and a preparation method thereof as claimed in claim 1, characterized in that: The preparation method of the nano-chitoxin comprises the following steps: S4: 40 to 400 parts by weight of chitosan powder are immersed in 1 wt% to 10 wt% NaOH, and mechanically stirred at 300 to 1000 rpm for 0.5 to 2 h at room temperature. The chitosan suspension after the reaction is washed with deionized water until the pH is neutral to remove protein from the chitosan powder. S5 then places the chitosan suspension obtained in S4 into a 1 wt% to 10 wt% HCl solution, mechanically stirring at a speed of 300 to 1000 rpm at room temperature for 1 to 4 h, and washing the reacted chitosan suspension with deionized water until the pH is neutral to remove minerals in the chitosan powder; S6 then drying the chitosan obtained in S5 at 30-80°C for 12-24 hours to obtain pure chitosan powder, further soaking the dried chitosan powder in 10 wt%-70 wt% NaOH, and adding 0.01%-0.1% w / v NaBH4 to the NaOH to prevent depolymerization of the chitosan, and mechanically stirring at 50-90°C at a stirring speed of 300-1000 rpm for 2-6 hours to perform deacetylation treatment, and washing the partially deacetylated chitosan suspension with distilled water to neutrality; S7 then adds 0.5~2 M acetic acid to adjust the pH of the deacetylated chitin suspension to 2~4, homogenizes, and finally obtains the nano-chitin solution, and tests its solid content.
3. The modified atmosphere fresh-keeping paper for fruits and vegetables and the preparation method thereof according to claim 1, characterized in that: The polyethylene glycol can be a combination of one or more of polyethylene glycol 200, polyethylene glycol 300, polyethylene glycol 400, polyethylene glycol 600, polyethylene glycol 1000, polyethylene glycol 2000, polyethylene glycol 4000, polyethylene glycol 6000, polyethylene glycol 10000, and polyethylene glycol 20000.
4. The modified atmosphere fresh-keeping paper for fruits and vegetables and the preparation method thereof according to claim 1, characterized in that: The specific ultrasonic treatment method in S2 is: ultrasonic treatment at 20-40° C. and an ultrasonic power of 200-800 W for 20-60 min.
5. The modified atmosphere fresh-keeping paper for fruits and vegetables and the preparation method thereof according to claim 1, characterized in that: The specific treatment method of the standing still described in S2 is: standing still at 4-30°C for 12-48 hours.
6. The modified atmosphere fresh-keeping paper for fruits and vegetables and the preparation method thereof according to claim 1, characterized in that: The specific treatment method of the centrifugation in S2 is: centrifugation at a speed of 1000-6000 rpm at 4-30°C for 1-6 minutes.
7. The modified atmosphere fresh-keeping paper for fruits and vegetables and the preparation method thereof according to claim 1, characterized in that: The specific treatment method of the drying in S3 is: the drying temperature is 20-50° C., and the drying time is 12-24 hours.