Low-carbon fresh-keeping normal-temperature storage, transportation and packaging method for litchis

Abstract

The invention relates to the technical field of fruit fresh-keeping storage, and discloses a low-carbon fresh-keeping litchi normal-temperature storage, transportation and packaging method which comprises the following steps: (1) pretreatment: picking fresh litchis, screening the picked fresh litchis, and then precooling the screened litchis until the temperature of fruit cores is 0-15 DEG C; (2) packaging: carrying out e-commerce packaging in an operation room at the temperature of 15-20 DEG C, firstly putting a phase change cold storage agent at the bottom of an aluminum foil heat preservation bag, then putting a bacteriostatic fresh-keeping water absorption pad, then putting the pretreated fresh litchis, packaging by using the aluminum foil heat preservation bag coated with a macromolecular waterproof layer, and finally putting the litchis into a drying room at the temperature of 15-20 DEG C; the whole aluminum foil heat preservation bag is placed into a foam box made of polypropylene plastic foam materials and then sealed, and the outer layer is a common carton with a trademark; the bacteriostatic fresh-keeping water-absorbing pad contains a water-absorbing bacteriostatic compound (3) for transportation; according to the packaging method, temperature control, bacteriostasis, drying and air permeability are achieved, the fresh-keeping effect on the litchis is effectively achieved, and the method is low-carbon, environmentally friendly, simple, efficient and high in generalization performance.

Description

Technical Field

[0001] The invention belongs to the technical field of fruit storage, and in particular relates to a low-carbon fresh-keeping litchi room-temperature storage and transportation packaging method. Background Art

[0002] Litchi is a representative tropical and subtropical fruit, rich in vitamins, minerals, and carbohydrates. It is nutritious, beautiful, and sweet, and is deeply loved by consumers. However, litchi is easy to rot, brown, and invaded by pathogens after harvest, which seriously affects its shelf life and market value. E-commerce logistics is the most important sales model. It reduces the intermediate links by connecting supply and demand, and has the advantages of wide sales range and high profits. At present, only about 10% of litchis adopt the e-commerce logistics model. The main problems are: 1) Litchi is concentrated in the market period, easy to rot and brown, and difficult to sell over long distances. 2) The cold chain infrastructure is poor, "chain breaks" occur frequently, the cost of cold chain express delivery is high, and the income is difficult to guarantee. 3) The current refrigerated transportation equipment is mainly mechanical refrigerated trucks. In today's high oil prices, it is not only economical and not environmentally friendly, but also may have the phenomenon of "big trucks delivering small goods". Therefore, it is particularly important to maintain the storage temperature of food during transportation through other means. At present, the transportation method adopted by litchi e-commerce logistics is mainly foam boxes with ice, but there are also the following problems: 1) The use of ice or ice bags (cooling agents) is not standardized, and the fruits near the ice bags are frozen and rotten; 2) The weight of the ice bags squeezes the actual transportation weight and transportation space of the fruits, increasing the transportation cost. In view of the above problems, taking into account the actual transportation environment, using composite preservation technology, combined with the development of litchi e-commerce logistics coolers with high latent heat, excellent thermal conductivity, no corrosion and excellent circulation performance, long-term cold storage and environmental protection requirements, the room temperature e-commerce logistics of litchi can be achieved. Long-distance sales, effectively reduce freight costs, improve the quality of litchi fruits, increase the proportion of litchi e-commerce logistics sales, and achieve increased production and income of litchi. Summary of the invention

[0003] In view of the above problems, the object of the present invention is to provide a low-carbon fresh-keeping litchi room-temperature storage and transportation packaging method.

[0004] The technical contents of the present invention are as follows:

[0005] The present invention provides a low-carbon and universal litchi e-commerce logistics normal temperature storage and transportation mode and method, the steps of which include:

[0006] (1) Fruit pretreatment: fresh lychees are picked and screened, and then precooled to a core temperature of 0-15°C;

[0007] The precooling temperature is set to 10-15°C; if the precooling temperature is too low, browning is likely to occur during the e-commerce logistics of litchi; if the precooling temperature is too high, the respiratory heat of litchi generates more water vapor accumulation;

[0008] (2) Packaging: Packaging is performed in an operating room at 15-20° C. First, a phase change coolant with a mass ratio of 1:4-6 to litchi is placed at the bottom of an aluminum foil insulation bag, followed by an antibacterial fresh-keeping absorbent pad, followed by pre-treated fresh litchi, which is then sealed in an aluminum foil insulation bag and then sealed in a foam box made of polypropylene plastic foam;

[0009] The antibacterial and fresh-keeping absorbent pad comprises three layers, an upper layer of water-permeable non-woven fabric, a middle layer of water-absorbing and antibacterial composite material, and a lower layer of water-impermeable film;

[0010] The formula of the composite phase-change coolant is 0.4-0.6% gellan gum, 0.8-1.2% xanthan gum, 0.8-1.2% erythritol, 0.8-1.2% sodium alginate, 2-4% glycerol, 0.8-1.2% NH4Cl, 0.8-1.2% KCl, 0.1-0.3% potassium sorbate, 0.8-1.2% Al2O3 nanoparticles, and the rest is deionized water.

[0011] The phase change temperature of the composite phase change refrigerant is 0-4°C, the phase change latent heat is 130-138J / kg, and there is no supercooling and phase separation phenomenon; the energy released for a long time can keep the packaging environment relatively low temperature, inhibit breathing and decay, and have a long-term cold storage effect;

[0012] The composite phase-change refrigerant is prepared by heating glycerol, NH4Cl, KCl, sodium alginate, composite nanoparticles and water in a water bath at 40-50°C for 40-50 minutes, adding the remaining components and stirring evenly, and then performing an ice bath at 0-3°C for 30-40 minutes.

[0013] The composite nanoparticles are obtained by mixing Al2O3 nanoparticles and nano-titanium dioxide in a mass ratio of 3:1-3; the added composite nanoparticles have a large specific surface area, can promote the heterogeneous nucleation of hydrates, and the synergistic effect of the two nanoparticles can improve the energy storage density and thermal conductivity;

[0014] The water-absorbing antibacterial composite is prepared by heat-treating activated carbon and zeolite in a mass ratio of 11-15:21-27 to prepare a wall material, compounding lemongrass essential oil and eucalyptus essential oil in a mass ratio of 1:1-3 to prepare a wall core, embedding the wall material and the wall core in a mass ratio of 10:1, and then freeze-drying the composite.

[0015] The modified β-cyclodextrin is prepared by adding olefin anhydride to β-cyclodextrin at a mass ratio of 11-14:1-3, stirring for 40-50 minutes, adjusting the pH to 5-7, adding 10-20wt% sodium silicate solution, stirring at 3000-4000rpm for 10-20 minutes, and heating at 70-80°C for 8-12 minutes; the anhydride can improve the cationic performance and introduce sulfhydryl groups, and the sodium silicate solution combined with high-speed stirring can increase the cavity structure of cyclodextrin and improve its inclusion effect.

[0016] The heat treatment is performed at a pressure of 3-6 MPa and a temperature of 90-100° C. for 3-5 hours.

[0017] The water-absorbing antibacterial compound can slowly release substances such as nerol, linalool, citronellal, etc. during transportation, inhibiting the growth of microorganisms in the packaging bag. At the same time, due to the mild release rate, it does not harm the peel; the activated carbon and zeolite can absorb the carbon dioxide gas produced by the respiration of the fruit, reduce the anaerobic respiration of the fruit, reduce odor substances and rot; the antibacterial preservation pad can effectively isolate the fruit from direct contact with the cold storage agent to avoid frostbite of the fruit;

[0018] The aluminum foil insulation bag is an aluminum foil bag with an inner layer of pearl cotton, and the inner layer of the pearl cotton is coated with a polymer waterproof layer with a thickness of 2-4 mm;

[0019] The coating method of the polymer waterproof layer is as follows: hydroxy resin and hydroxy silicone oil are mixed and coated on the pearl cotton in a mass ratio of 1:0.1-0.4, and then the mixture is mixed with hot melt adhesive and cold-sense non-woven fabric to form the inner layer of the pearl cotton through a hot press; the hydroxy silicone oil can improve the water resistance, antibacterial and mechanical properties of the resin with hydroxy properties, and the polymer waterproof layer can be accumulated in a large size in the cotton fiber, and has the ability to absorb water and isolate oxygen; the cold-sense non-woven fabric is water-permeable and breathable, easy to dry, and does not accumulate water, thereby reducing the rot of the contact surface between the fruit and the packaging bag;

[0020] The main material of the foam box is polypropylene plastic foam material, with a wall thickness of ≥20mm;

[0021] (3) Finally, pack into ordinary cartons for transportation.

[0022] The beneficial effects of the present invention are as follows:

[0023] The invention provides a low-carbon fresh-keeping litchi room-temperature storage and transportation method. The litchi is pretreated and then packaged for fresh-keeping using a package containing a phase-change cooling agent, an antibacterial fresh-keeping water-absorbing pad and an aluminum foil insulation bag. The phase-change cooling agent contains an expanded loose component, can carry nanoparticles for synergistic effect, can effectively promote hydrate nucleation, and has good mass transfer performance, high thermal conductivity, and high temperature control ability. The antibacterial fresh-keeping water-absorbing pad contains a water-absorbing and antibacterial composite material, which is compounded with a porous material through modified beta-cyclodextrin and loaded with essential oil, has strong adsorption, can effectively inhibit bacteria and absorb moisture at the same time; the aluminum foil insulation bag is coated with a polymer waterproof layer, which can absorb water vapor and condensed water generated by the respiration of the litchi in the bag, and at the same time increase the air permeability of the pearl cotton to reduce the decay rate of the fruit; the packaging method of the invention can have temperature control, antibacterial and dry air permeability, effectively preserve the litchi, and is low-carbon, environmentally friendly, simple and efficient, and has strong promotion. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 The figure is a schematic structural diagram of a method for packaging litchi according to an embodiment of the present invention. DETAILED DESCRIPTION

[0025] The present invention is further described in detail below through specific implementation cases and accompanying drawings. It should be understood that these embodiments are only used to illustrate the present invention and are not used to limit the scope of protection of the present invention. After reading the present invention, various equivalent forms of modifications to the present invention by those skilled in the art are all within the scope of the claims attached to this application.

[0026] Unless otherwise specified, all raw materials and reagents of the present invention are raw materials and reagents from the conventional market.

[0027] The structural schematic diagram of the packaging method for litchi according to the embodiment of the present invention is as follows Figure 1 shown.

[0028] Example 1

[0029] A low-carbon and universal litchi e-commerce logistics normal temperature storage and transportation mode and method, the steps of which include:

[0030] (1) Fruit pretreatment: fresh "Jinggang Hongnuo" lychees are picked and selected, and then precooled in a cold storage until the fruit core temperature is ≤15°C; the precooling temperature is set to 13°C;

[0031] (2) Packaging: Packaging is performed in an operating room at 18°C. First, a phase change coolant with a mass ratio of 1:5 to litchi is placed at the bottom of an aluminum foil insulation bag, followed by an antibacterial fresh-keeping absorbent pad, followed by pre-treated fresh litchi, which is then sealed in an aluminum foil insulation bag and then sealed in a foam box made of polypropylene plastic foam;

[0032] The composite phase-change refrigerant is prepared by heating 3% of glycerol, 1.0% of NH4Cl, 1.0% of KCl, 1.0% of sodium alginate, 1.0% of composite nanoparticles obtained by mixing Al2O3 nanoparticles and nano-titanium dioxide in a mass ratio of 3:2, and 91.3% of water in a water bath at 45°C for 45 minutes, then adding 1.0% of xanthan gum, 0.5% of gellan gum and 0.2% of potassium sorbate, stirring evenly, and then performing an ice bath at 2°C for 35 minutes to obtain the composite phase-change refrigerant.

[0033] The antibacterial and fresh-keeping absorbent pad comprises three layers, an upper layer of permeable non-woven fabric, a middle layer of an absorbent and antibacterial composite, and a lower layer of an impermeable film; the absorbent and antibacterial composite is prepared by heat treatment of activated carbon and zeolite in a mass ratio of 13:24 to prepare a wall material, lemongrass essential oil and eucalyptus essential oil are compounded in a mass ratio of 1:2 to prepare a wall core, the wall material and the wall core are embedded in a mass ratio of 10:1, and then freeze-dried to prepare the obtained material; the modified β-cyclodextrin is prepared by adding β-cyclodextrin in a mass ratio of 11-14:1-3 to olefin anhydride, stirring for 45 minutes, adjusting the pH to 6, adding 15wt% sodium silicate solution, stirring at 3500rpm for 15 minutes, and heating at 75°C for 10 minutes; the heat treatment is heating at a pressure of 5MPa and a temperature of 95°C for 4 hours;

[0034] The main material of the aluminum foil insulation bag is an aluminum foil bag with an inner layer of pearl cotton, and the inner layer of the pearl cotton is coated with a polymer waterproof layer with a thickness of 3mm; the coating method of the polymer waterproof layer is: hydroxyl resin and hydroxyl silicone oil are mixed in a mass ratio of 1:0.3 and coated on the pearl cotton, and the inner layer of the pearl cotton is formed by a hot press with hot melt adhesive and cold non-woven fabric; the main material of the foam box is polypropylene plastic foam material, and the wall thickness is ≥20mm;

[0035] (3) Finally, pack them into ordinary cartons. The packaged lychees were placed at 25°C for one week. The results showed that the lychees had less browning in the first three days, a small amount of browning in the seventh day, no moldy fruit, no rot, and good appearance.

[0036] Example 2

[0037] A low-carbon and universal litchi e-commerce logistics normal temperature storage and transportation mode and method, the steps of which include:

[0038] (1) Fruit pretreatment: fresh "Jinggang Hongnuo" lychees are picked and screened, and then precooled in a cold storage until the fruit core temperature is ≤12°C; the precooling temperature is set to 10°C;

[0039] (2) Packaging: Packaging is performed in an operating room at 15°C. First, a phase change coolant with a mass ratio of 1:4 to litchi is placed at the bottom of an aluminum foil insulation bag, followed by an antibacterial fresh-keeping absorbent pad, followed by pre-treated fresh litchi, which is then sealed in an aluminum foil insulation bag and then sealed in a foam box made of polypropylene plastic foam;

[0040] The composite phase-change refrigerant is prepared by heating 2% of glycerol, 0.8% of NH4Cl, 0.8% of KCl, 0.8% of sodium alginate, 0.8% of composite nanoparticles obtained by mixing Al2O3 nanoparticles and nano-titanium dioxide in a mass ratio of 3:1, and 93.5% of water in a water bath at 40°C for 40 minutes, then adding 0.8% of xanthan gum, 0.4% of gellan gum and 0.1% of potassium sorbate, stirring evenly, and then performing an ice bath at 0°C for 30 minutes to obtain the composite phase-change refrigerant.

[0041] The antibacterial and fresh-keeping absorbent pad comprises three layers, an upper layer of water-permeable non-woven fabric, a middle layer of a water-absorbing and antibacterial compound, and a lower layer of a water-impermeable film; the water-absorbing and antibacterial compound is a wall material prepared by heat treatment of activated carbon and zeolite in a mass ratio of 11:21, 10wt% of modified β-cyclodextrin, lemongrass essential oil and eucalyptus essential oil in a mass ratio of 1:1 as a wall core, the wall material and the wall core are embedded in a mass ratio of 10:1, and then freeze-dried to prepare the obtained material; the modified β-cyclodextrin is prepared by adding β-cyclodextrin in a mass ratio of 11:1 to olefin anhydride, stirring for 40 minutes, adjusting the pH to 5, adding 10wt% of sodium silicate solution, stirring at 3000rpm for 10 minutes, and heating at 70°C for 8 minutes; the heat treatment is heating at a pressure of 3MPa and a temperature of 90°C for 3h;

[0042] The main material of the aluminum foil insulation bag is an aluminum foil bag with an inner layer of pearl cotton, and the inner layer of the pearl cotton is coated with a polymer waterproof layer with a thickness of 2mm; the coating method of the polymer waterproof layer is: hydroxyl resin and hydroxyl silicone oil are mixed at a mass ratio of 1:0.1 and coated on the pearl cotton, and the inner layer of the pearl cotton is formed by a hot press with hot melt adhesive and cold non-woven fabric; the main material of the foam box is polypropylene plastic foam material, and the wall thickness is ≥20mm;

[0043] (3) Finally, pack them into ordinary cartons. The packaged lychees were placed at 25°C for one week. The results showed that the lychees had little browning in the first three days, a small amount of browning in the seventh day, no mold, no rot, and good appearance.

[0044] Example 3

[0045] A low-carbon and universal litchi e-commerce logistics normal temperature storage and transportation mode and method, the steps of which include:

[0046] (1) Fruit pretreatment: fresh "Jinggang Hongnuo" lychees are picked and screened, and then precooled in a cold storage until the fruit core temperature is 15° C.; the precooling temperature is set to 15° C.;

[0047] (2) Packaging: Packaging is performed in an operating room at 20°C. First, a phase change coolant with a mass ratio of 1:6 to litchi is placed at the bottom of an aluminum foil insulation bag, followed by an antibacterial fresh-keeping absorbent pad, followed by pre-treated fresh litchi, which is then sealed in an aluminum foil insulation bag and then sealed in a foam box made of polypropylene plastic foam;

[0048] The water-absorbing antibacterial composite is prepared by heat-treating activated carbon and zeolite in a mass ratio of 15:27 to prepare a wall material, and compounding lemongrass essential oil and eucalyptus essential oil in a mass ratio of 1:3 to prepare a wall core, embedding the wall material and the wall core in a mass ratio of 10:1, and then freeze-drying; the preparation of the modified β-cyclodextrin is to add β-cyclodextrin in a mass ratio of 14:3 to olefin anhydride and stir for 50 minutes, adjust the pH to 7, add 20wt% sodium silicate solution, stir at 4000rpm for 20 minutes, and heat at 70-80°C for 12 minutes; the heat treatment is heating at a pressure of 6MPa and a temperature of 100°C for 5 hours;

[0049] The composite phase-change refrigerant is prepared by heating 4% of glycerol, 1.2% of NH4Cl, 1.2% of KCl, 1.2% of sodium alginate, 1.2% of composite nanoparticles obtained by mixing Al2O3 nanoparticles and nano-titanium dioxide in a mass ratio of 3:3, and 89.1% of water in a water bath at 50°C for 50 minutes, then adding 1.2% of xanthan gum, 0.6% of gellan gum and 0.3% of potassium sorbate, stirring evenly, and then performing an ice bath at 3°C ​​for 40 minutes to obtain the composite phase-change refrigerant.

[0050] The antibacterial and fresh-keeping absorbent pad comprises three layers, an upper layer of permeable non-woven fabric, a middle layer of absorbent and antibacterial composite, and a lower layer of impermeable film; the absorbent and antibacterial composite is prepared by heat treatment of activated carbon and zeolite in a mass ratio of 15:27 to prepare wall material, lemongrass essential oil and eucalyptus essential oil in a mass ratio of 1:3 to prepare wall core, the wall material and the wall core in a mass ratio of 10:1 are embedded, and then freeze-dried to prepare; the modified β-cyclodextrin is prepared by adding β-cyclodextrin in a mass ratio of 14:3 to olefin anhydride and stirring at a low speed for 50 minutes, adjusting the pH to 7, adding 20wt% sodium silicate solution and stirring at a high speed for 20 minutes; the heat treatment is heating at a pressure of 6MPa and a temperature of 100°C for 5 hours;

[0051] The main material of the aluminum foil insulation bag is an aluminum foil bag with an inner layer of pearl cotton, and the inner layer of the pearl cotton is coated with a polymer waterproof layer with a thickness of 4mm; the coating method of the polymer waterproof layer is: hydroxyl resin and hydroxyl silicone oil are mixed in a mass ratio of 1:0.4 and coated on the pearl cotton, and the inner layer of the pearl cotton is formed by a hot press with hot melt adhesive and cold non-woven fabric;

[0052] (3) Finally, pack them into ordinary cartons. The packaged lychees were placed at 25°C for one week. The results showed that the surface of the lychees had little browning in the first three days, a small amount of browning in the seventh day, no moldy fruit, no rot, and good appearance.

[0053] Comparative Example 1

[0054] The difference between Comparative Example 1 and Example 1 is that the composite phase change coolant in Comparative Example 1 is replaced by an ordinary coolant purchased on the market, and the other aspects remain unchanged; the packaged lychees are placed at 25°C for one week, and the results show that there are a large number of brown fruits on the surface of the lychees, slight mold spots, no rot, and the appearance is normal.

[0055] Comparative Example 2

[0056] The difference between Comparative Example 2 and Example 1 is that the aluminum foil insulation bag of Comparative Example 2 is not coated with a polymer waterproof layer, and the other aspects remain unchanged; the packaged lychees are placed at 25°C for one week, and the results show that there are a large number of brown fruits on the surface of the lychees, some are moldy, there is no rot, and the appearance is normal.

[0057] Comparative Example 3

[0058] The difference between Comparative Example 3 and Example 1 is that the antibacterial fresh-keeping pad of Comparative Example 3 does not add modified β-cyclodextrin, and the other conditions remain unchanged; the packaged lychees are placed at 25°C for one week, and the results show that there are a large number of brown fruits on the surface of the lychees, some are moldy, there is no rot, and the appearance is normal.

[0059] Control group

[0060] The control group picked fresh lychees without pre-cooling, and directly packed them in ordinary plastic bags. Ordinary ice bags on the market were added to the bottom of the box. To prevent the fruit from frostbite, a layer of absorbent paper was placed on the ordinary ice bag and sealed. The packaged lychees were placed at 25°C for one week. The results showed that the lychees were severely browned, with a large number of moldy fruits and a small amount of rot, and the appearance was poor.

[0061] Determination methods of various indicators:

[0062] Browning index: The statistics and calculation of browning index refer to the method described in Wu Dan et al. (2024). The browning of the peel is divided into 4 levels according to the ratio of browning area to peel area: peel without obvious brown spots is level 0, browning area accounting for less than 1 / 4 is level 1, 1 / 4 to 1 / 2 is level 2, 1 / 2 to 3 / 4 is level 3, and more than 3 / 4 is level 4. The calculation of browning index (BI) refers to the method of Zhang et al. (2018).

[0063] Soluble solids: Add 6 to 7 drops of litchi juice into the groove of the digital saccharimeter detection mirror to test the soluble solids.

[0064] Determination of vitamin C content: refer to GB 5009.86-2016 National Food Safety Standard - Determination of ascorbic acid in food for testing.

[0065] During storage and transportation, the litchi of the embodiment and the comparative example were tested regularly. The test results are shown in Table 1.

[0066] Table 1 Changes in the browning rate of litchi peel

[0067]

[0068]

[0069] It can be seen from Table 1 that the browning index of litchi during storage and transportation according to the method of the embodiment of the present invention is low, the appearance is kept high, and the quality of litchi is good.

[0070] Table 2 Changes in soluble solids content of litchi pulp

[0071]

[0072] As shown in Table 2, the soluble solids content of the litchi during storage and transportation according to the method of the embodiment of the present invention is higher. Compared with the control group, the taste of the litchi after storage and transportation according to the present invention is better.

[0073] Table 3 Changes in vitamin C content in litchi pulp

[0074]

[0075] As shown in Table 3, the change in vitamin content of litchi stored and transported by the method of the embodiment of the present invention within 3 days is significantly higher than that of the comparative example, and the nutritional quality of litchi can be better maintained during storage and transportation at room temperature.

[0076] In summary, it can be seen from Comparative Example 1 that the composite nanoparticles added to the composite phase change coolant prepared by the present invention can improve the energy storage density and thermal conductivity of the coolant, have both high phase change latent heat and phase stability, can store cold for a long time, and realize the fresh-keeping storage of litchi at room temperature; it can be seen from Comparative Example 2 that the aluminum foil insulation bag of the present invention is also coated with a polymer waterproof layer, which absorbs water while also having water-resistant and oxygen-permeable adsorption functions, providing litchi with an environment that is not easy to rot and easy to store; it can be seen from Comparative Example 3 that the antibacterial waterproof pad of the present invention is added with porous materials and antibacterial essential oils, and modified β-cyclodextrin with cationic properties and excellent cavity properties is also added, which has excellent antibacterial agent loading effect, can enhance the adsorption performance of the porous material, and has a sustained release effect on the antibacterial essential oil, which can improve the fresh-keeping effect on litchi.

Claims

1. A low-carbon fresh-keeping litchi room temperature storage and transportation packaging method, characterized in that: The steps include include: (1) Fruit pretreatment: fresh lychees are picked and screened, and then precooled to a core temperature of 0-15°C; (2) Packaging: Packaging is performed in an operating room at 15-20° C. First, a composite phase change coolant with a mass ratio of 1:4-6 to litchi is placed at the bottom of an aluminum foil insulation bag, followed by an antibacterial fresh-keeping absorbent pad, followed by pre-treated fresh litchi, which is then sealed in an aluminum foil insulation bag and then sealed in a foam box made of polypropylene plastic foam; The antibacterial and fresh-keeping absorbent pad comprises three layers, an upper layer of water-permeable non-woven fabric, a middle layer of water-absorbing and antibacterial composite material, and a lower layer of water-impermeable film; (3) Finally, pack into ordinary cartons for transportation.

2. A low-carbon fresh-keeping litchi room temperature storage and transportation packaging method according to claim 1, characterized in that: The precooling temperature in step (1) is set to 10-15°C.

3. A low-carbon fresh-keeping litchi room temperature storage and transportation packaging method according to claim 1, characterized in that: The formula of the composite phase change coolant in step (2) is 0.4-0.6% gellan gum, 0.8-1.2% xanthan gum, 0.8-1.2% erythritol, 0.8-1.2% sodium alginate, 2-4% Glycerol, 0.8-1.2% NH4Cl, 0.8-1.2% KCl, 0.1-0.3% potassium sorbate, 0.8-1.2% Al2O3 nanoparticles, and the rest is deionized water.

4. A low-carbon fresh-keeping litchi room temperature storage and transportation packaging method according to claim 3, characterized in that: The preparation method of the composite phase-change refrigerant comprises heating glycerol, NH4Cl, KCl, sodium alginate, composite nanoparticles and water in a water bath at 40-50°C for 40-50 minutes, adding the remaining components and stirring evenly, and then performing an ice bath at 0-3°C for 30-40 minutes to obtain the composite phase-change refrigerant.

5. A low-carbon fresh-keeping litchi room temperature storage and transportation packaging method according to claim 3, characterized in that: The composite nanoparticles are obtained by mixing Al2O3 nanoparticles and nanoparticles in a mass ratio of 3:1-3.

6. A low-carbon fresh-keeping litchi room temperature storage and transportation packaging method according to claim 1, characterized in that: The water-absorbing antibacterial composite is prepared by adding 10-15wt% of modified beta-cyclodextrin to activated carbon and zeolite in a mass ratio of 11-15:21-27 for heat treatment to prepare wall material, compounding lemongrass essential oil and eucalyptus essential oil in a mass ratio of 1:1-3 to form a wall core, embedding the wall material and the wall core in a mass ratio of 10:1, and then freeze-drying to prepare the composite.

7. A low-carbon fresh-keeping litchi room temperature storage and transportation packaging method according to claim 6, characterized in that: The modified β-cyclodextrin is prepared by adding olefin anhydride to β-cyclodextrin at a mass ratio of 11-14:1-3, stirring for 40-50 minutes, adjusting the pH to 5-7, adding 10-20wt% sodium silicate solution, stirring at 3000-4000rpm for 10-20 minutes, and heating at 70-80°C for 8-12 minutes.

8. A low-carbon fresh-keeping litchi room temperature storage and transportation packaging method according to claim 6, characterized in that: The heat treatment is performed at a pressure of 3-6 MPa and a temperature of 90-100° C. for 3-5 hours.

9. A low-carbon fresh-keeping litchi room temperature storage and transportation packaging method according to claim 1, characterized in that: The aluminum foil insulation bag in step (2) is an aluminum foil bag with an inner layer of pearl cotton, and the inner layer of the pearl cotton is coated with a polymer waterproof layer with a thickness of 2-4 mm.

10. A low-carbon fresh-keeping litchi room temperature storage and transportation packaging method according to claim 9, characterized in that: The coating method of the polymer waterproof layer is: hydroxyl resin and hydroxyl silicone oil are mixed in a mass ratio of 1:0.1-0.4 and coated on the pearl cotton, and then formed into the inner layer of the pearl cotton with hot melt adhesive and cold non-woven fabric through a hot press.

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