Fresh-keeping material and application thereof, fresh-keeping paper and preparation method thereof and application thereof

Abstract

The present invention provides a fresh-keeping material and its application, a fresh-keeping paper and its preparation method and application, and belongs to the technical field of fruit and vegetable fresh-keeping. The present invention combines a fresh-keeping material with ethylene decomposition ability with a papermaking process to prepare a fresh-keeping paper with ethylene decomposition ability. The obtained fresh-keeping paper also has efficient bactericidal, antibacterial and mildew-proof abilities, has a simple preparation process, low cost, and does not contain toxic and harmful substances. The technical problems of the prior art that the fresh-keeping material has poor bactericidal and antibacterial ability, does not have ethylene decomposition effect, has poor mildew-proof performance, is high in cost, and has a complicated process are solved.

Description

Technical Field

[0001] The invention relates to the technical field of fruit and vegetable preservation, and in particular to a preservation material and application thereof, a preservation paper and a preparation method and application thereof. Background Art

[0002] In order to reduce the loss and waste of crops, ensure food quality, and meet consumers' requirements for food safety, the research and development and application of preservation technology have received widespread attention. Traditional fresh-keeping paper mainly relies on physical barriers to slow down the growth of microorganisms and the oxidation process of food. However, with the improvement of people's living standards, consumers have higher requirements for food quality and safety. Although traditional preservation methods, such as refrigeration and vacuum packaging, can extend the shelf life of food to a certain extent, they can often only play a simple barrier role. The effect of preventing mold growth is limited, and there are still problems such as easy to be affected by moisture and easy to breed mold. There are some existing antibacterial fresh-keeping papers, which are usually dedicated to a single fruit and vegetable, with poor universality, and the production process is complicated, the production efficiency is low, and it is not easy to form industrial production. In addition, there are also antibacterial fresh-keeping papers with single functions. Hot melt adhesives or organic solvents are used in the manufacturing process, and the glue coating process is complicated, resulting in uneven distribution of internal preservatives. In places where there are few preservatives, the antibacterial and ethylene decomposition effects are very weak, causing fruits and vegetables to rot and age. In addition, due to the uneven distribution of the preservative and the small preservation area, uneven sterilization is likely to occur and the preservation effect cannot be guaranteed.

[0003] At present, SO2 preservative paper has been widely used. A higher concentration of SO2 can inhibit intracellular oxidative aging processes such as polyphenol oxidase, peroxide oxidation, and respiration. However, the ingredients of the preservative are not matched properly, resulting in the failure to slowly release the preservative gas and uncontrollable release time, causing excessive local release of the preservative gas, which contaminates fruits and vegetables and affects human health.

[0004] The Chinese invention patent with the publication number CN 118461363 A discloses a process for making mildew-proof fresh-keeping paper. Although it avoids the risk of excessive SO2, it has a high cost and the processing steps are refined, which is not conducive to large-scale production. The Chinese invention patent with the publication number CN102953294 B discloses a vegetable preservative, which uses vegetables and their waste as a skeleton to prepare fresh-keeping paper, adsorbs fermentation gases such as ethylene and ethanol through activated carbon, and kills the pathogens on the surface of vegetables through the combination of bactericides and bactericidal slow-release agents, but the adsorption capacity of activated carbon is limited, and it can only achieve the adsorption of fermentation gases but not decomposition, the shelf life is short, and the paper quality is poor, and it is easy to break during transportation, which is not conducive to long-distance transportation. The Chinese invention patent with the authorization announcement number CN105904796 B discloses a longan fresh-keeping paper with a multi-layer structure, which specifically discloses spraying the preservative on the carrier layer. Although this method is simple in process, it has the problem of uneven distribution of the preservative and the risk of excessive SO2, which endangers human health. Therefore, the prior art lacks a fresh-keeping paper which has the functions of high-efficiency sterilization and antibacterial, decomposition of ethylene, and mildew prevention, and has a simple manufacturing process and low cost.

[0005] In the prior art, polylactic acid is often used as a raw material for fruit and vegetable fresh-keeping bags because of its significant water-blocking properties. It can effectively prevent the entry of external moisture and effectively slow down the respiration of fruits and vegetables. However, it is precisely because of the excellent water-blocking properties of polylactic acid that the water vapor produced cannot be absorbed or discharged as fruits and vegetables naturally mature, which in turn accelerates the maturity and even corruption of fruits and vegetables. This is also an important reason why polylactic acid fresh-keeping bags cannot achieve long-term fresh-keeping and can only be used for transportation or short-term storage. The Chinese invention patent with publication number CN112832058A uses wood fiber to prepare stretchable paper, and then mixes the fresh-keeping ingredients with polylactic acid in the form of microcapsules to obtain a glue solution, which is applied to the stretchable paper to obtain a composite fresh-keeping paper. Although this technical solution has a certain fresh-keeping effect, it is far from meeting the fresh-keeping needs. Summary of the invention

[0006] The purpose of the present invention is to provide a fresh-keeping material and its application, a fresh-keeping paper and its preparation method and application, which are used to solve the technical problems in the prior art that the fresh-keeping materials have poor bactericidal and antibacterial abilities, do not have ethylene decomposition effects, have poor mildew resistance, are high in cost and have complicated processes.

[0007] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0008] The present invention provides a fresh-keeping material, which is composed of the following components in parts by weight: 75 to 95 parts of polylactic acid and 3 to 8 parts of a fresh-keeping agent;

[0009] The preservative is prepared from an active component precursor, a carrier and an oxidant;

[0010] The active component precursor includes a main active component precursor and an auxiliary active component precursor, wherein the main active component precursor is a chloride of a transition metal element, and the auxiliary active component precursor is a chloride of a rare earth element; the carrier is one or a combination of two or more selected from porous alumina, titanium oxide, montmorillonite, kaolin, and molecular sieves; the oxidant is one or a combination of two or more selected from sodium hypochlorite, sodium chlorite, and hexadecyl trichloroacetate;

[0011] The number average molecular weight of the polylactic acid is 100 to 20,000.

[0012] Furthermore, the content of the active component is 0.1-20% of the weight of the carrier; the molar ratio of the main active component to the auxiliary active component is 1:0-0.5; and the content of the oxidant is 2-10% of the weight of the carrier.

[0013] The present invention provides a method for preparing fresh-keeping paper from the fresh-keeping material, comprising the following steps:

[0014] Step 1), crushing, boiling, washing, beating, papermaking and drying the bamboo segments and bagasse in sequence to obtain the sealing material;

[0015] Step 2), mixing the fresh-keeping material, inorganic filler, adhesive and dispersant, and subjecting the mixture to banburying, extrusion and paper-like treatment to obtain a fresh-keeping paper substrate;

[0016] Step 3), using an adhesive to bond the sealing material, the cling paper substrate and the sealing material in the structural order, and then calendering to obtain the cling paper;

[0017] The inorganic filler includes wollastonite and / or calcium carbonate;

[0018] The adhesive comprises one or more of chitosan, gelatin and gum arabic.

[0019] Furthermore, in step 1), the mass ratio of the bamboo segments to the bagasse is 30-40:25-50;

[0020] The viscosity of the slurry is 3 to 6 mPa / s;

[0021] The drying temperature is 70-110° C., and the drying time is 3-8 hours.

[0022] Furthermore, in step 2), the mass ratio of the inorganic filler to the polylactic acid in the fresh-keeping material is 30-40:75-95;

[0023] The added amount of the dispersant is 0.1 to 5 wt % of the fresh-keeping paper base material;

[0024] The added amount of the adhesive is 10-30wt% of the fresh-keeping paper base material.

[0025] Furthermore, in step 2), the particle size of the fresh-keeping material is 250-300 mesh, the banburying temperature is 150-190° C., the banburying time is 5-40 min, and the banburying speed is 20-60 rpm;

[0026] The extrusion temperature is 160-190°C.

[0027] Furthermore, in step 3), the calendering temperature is 50-70° C., and the calendering line pressure is 20-60 kN / m.

[0028] The invention provides a fresh-keeping paper prepared by the above-mentioned preparation method.

[0029] The present invention also provides an application of fresh-keeping paper in preparing fresh-keeping paper boxes, which can be achieved by bonding the paper to the inner surface of the corrugated paper box.

[0030] The present invention also provides an application of the fresh-keeping material in preparing a fresh-keeping film. The fresh-keeping material is mixed with dichloromethane, and then subjected to defoaming, film casting and drying to obtain the fresh-keeping film.

[0031] In the fresh-keeping material, the mass ratio of polylactic acid with a number average molecular weight of 100 to 300 to polylactic acid with a number average molecular weight of 300 to 20000 is 0.01 to 0.2:1 。

[0032] Beneficial effects of the present invention:

[0033] The present invention uses a preservative with ethylene decomposition function, and utilizes the synergistic effect of chlorine dioxide and a metal catalyst carrier to kill bacteria and decompose ethylene. No sulfur-containing substances are added to the preservative material of the present invention, thereby avoiding the harm to the human body caused by excessive sulfur dioxide. The preservative of the present invention decomposes ethylene into carbon dioxide and water, and the generated carbon dioxide can reversely inhibit the respiration of fruits and vegetables, thereby slowing down the ripening of fruits and vegetables.

[0034] The fresh-keeping paper prepared by the present invention is provided with sealing materials on both sides, and the sealing materials are made of relatively coarse bamboo fibers and sugar cane fibers. The present invention is provided with light pulping, so that the bamboo fibers and sugar cane fibers are well dispersed and not cut or overly thinned. The relatively coarse fibers have good water absorption and air permeability, and can absorb trace water vapor generated by the respiration of fruits and vegetables in the fresh-keeping environment, and reduce the environmental humidity.

[0035] The present invention uses polylactic acid with good air permeability as a matrix to coat the preservative. The polylactic acid has hydrophobic properties, which can prevent the preservative wrapped inside from having a large-area contact with water molecules, thereby preventing the ethylene decomposition effect from being reduced.

[0036] In terms of raw material selection, the present invention selects relatively coarse fibers to prepare the fresh-keeping paper sealing material, and at the same time adds a certain mass of inorganic fillers and fresh-keeping materials to the fresh-keeping paper substrate, thereby enhancing the mechanical strength of the fresh-keeping paper; in terms of preparation process, the present invention controls the calendering line pressure, beating degree, and filler particle size in the papermaking process, and multiple factors work together to reduce the surface smoothness of the fresh-keeping paper, greatly increase the water absorption effect, effectively absorb the water vapor generated by the respiration of fruits and vegetables during the fresh-keeping process, reduce the humidity around the fruits and vegetables, and at the same time have a certain structural strength, and will not cause hair loss, residue loss, etc., greatly reducing the risk of poor fresh-keeping effect caused by hard spikes such as fruit stalks and fruit shells of fruits and vegetables piercing the fresh-keeping paper.

[0037] The fresh-keeping material of the present invention is filled in the structure of the fresh-keeping paper, which can greatly improve the fresh-keeping effect; the fresh-keeping paper of the present invention has a simple structure and excellent fresh-keeping effect. Compared with the paper form with a multi-layer structure, its production process is simpler, the technical effect is more excellent, and a large amount of manpower and material resources are saved. DETAILED DESCRIPTION

[0038] The present invention provides a fresh-keeping material, which is composed of the following components in parts by weight: 75 to 95 parts of polylactic acid and 3 to 8 parts of a fresh-keeping agent;

[0039] The preservative is prepared from an active component precursor, a carrier and an oxidant;

[0040] The active component precursor includes a main active component precursor and an auxiliary active component precursor, wherein the main active component precursor is a chloride of a transition metal element, and the auxiliary active component precursor is a chloride of a rare earth element; the carrier is one or a combination of two or more selected from porous alumina, titanium oxide, montmorillonite, kaolin, and molecular sieves; the oxidant is one or a combination of two or more selected from sodium hypochlorite, sodium chlorite, potassium permanganate, and hexadecyl trichloroacetate;

[0041] The number average molecular weight of the polylactic acid is 100 to 20,000.

[0042] In the present invention, the amount of the polylactic acid used is preferably 80 to 90 parts by mass, and more preferably 85 parts by mass.

[0043] In the present invention, the amount of the preservative is preferably 4 to 7 parts by mass, more preferably 6 parts.

[0044] In the present invention, the number average molecular weight of the polylactic acid is preferably 500 to 10,000, more preferably 1,000 to 5,000.

[0045] In the present invention, the chloride of the transition metal element is preferably one or more of cobalt chloride, molybdenum chloride, copper chloride, nickel chloride and manganese chloride, further preferably one or more of cobalt chloride, cobalt dichloride, molybdenum chloride and copper chloride, more preferably copper chloride.

[0046] In the present invention, the chloride of the rare earth element is preferably one or more of lanthanum chloride, cerium chloride and neodymium chloride, and more preferably cerium chloride.

[0047] In the present invention, the molecular sieve is preferably one or a combination of two or more of 13X molecular sieve, 5A molecular sieve, mordenite, Y-type molecular sieve or other molecular sieves with a pore structure, and more preferably Y-type molecular sieve.

[0048] In the present invention, the oxidant is preferably sodium chlorite, potassium permanganate, hexadecyl trichloroacetate, or a combination of two or more thereof.

[0049] In the present invention, the preservative is prepared by adding water to the active component to form an active component impregnation solution, and then the carrier is impregnated in the impregnation solution, and then dried and roasted to prepare an active component precursor, and the oxidant is added to water to prepare an oxidant impregnation solution, and then the active component precursor is impregnated in the oxidant impregnation solution and dried.

[0050] In the present invention, the preservative decomposes ethylene into carbon dioxide and water, effectively slowing down the ripening effect of the ripening gas on the fruit.

[0051] In the present invention, the content of the active component is 0.1-20% of the weight of the carrier, preferably 5-15%, and more preferably 10%; the molar ratio of the main active component to the auxiliary active component is 1:0-0.5, preferably 1:0.3; the content of the oxidant is 2-10% of the weight of the carrier, preferably 3-8%, and more preferably 5%.

[0052] The present invention provides a method for preparing fresh-keeping paper from the fresh-keeping material, comprising the following steps:

[0053] Step 1), crushing, boiling, washing, beating, papermaking and drying the bamboo segments and bagasse in sequence to obtain the sealing material;

[0054] Step 2), mixing the fresh-keeping material, inorganic filler, adhesive and dispersant, and subjecting the mixture to banburying, extrusion and paper-like treatment to obtain a fresh-keeping paper substrate;

[0055] Step 3), using an adhesive to bond the sealing material, the cling paper substrate and the sealing material in the structural order, and then calendering to obtain the cling paper;

[0056] The inorganic filler includes wollastonite and / or calcium carbonate;

[0057] The adhesive comprises one or more of chitosan, gelatin and gum arabic.

[0058] In the present invention, the inorganic filler is preferably wollastonite and calcium carbonate. In the present invention, the average particle size of the inorganic filler is preferably 8 to 32 μm, more preferably 10 to 20 μm, and more preferably 15 μm.

[0059] In the present invention, the binder is preferably chitosan, gelatin or gum arabic.

[0060] In the present invention, the inorganic filler and the preservative in the preservative material cooperate with each other to jointly improve the mechanical properties and processability of the polylactic acid matrix.

[0061] In the present invention, starch is not recommended as the adhesive because there is a certain amount of moisture in the sealing material. In the subsequent bonding, drying and calendering processes, the starch may form irreversible gelatinization when it meets water at a certain temperature, affecting the paper structure and air and water permeability.

[0062] In the present invention, the dispersant is preferably ethylene bisstearoyl.

[0063] In the present invention, in step 1), the mass ratio of the bamboo segments to the bagasse is 30-40:25-50, preferably 32-38:30-45, and more preferably 35:40;

[0064] The viscosity of the slurry is 3-6 mPa / s, preferably 4 mPa / s.

[0065] The drying temperature is 70-80° C., preferably 75° C., and the drying time is 3-8 hours, preferably 4-7 hours, and more preferably 6 hours.

[0066] In the present invention, in step 1), after the beating, the fiber length of the bamboo fiber in the obtained pulp is preferably 3-6 mm, and the length of the bagasse fiber is preferably 1.2-2 mm.

[0067] In the present invention, bamboo fiber is a natural high molecular compound composed of cellulose, hemicellulose, lignin and extracts, with a cellulose content of 40-45%. Each base ring of cellulose contains hydroxyl groups, and the hydroxyl groups in the molecule have strong water absorption and strong polarity.

[0068] In the present invention, in step 1), the beating is viscous beating, so that the fibers are evenly separated while the fibers are kept from being cut short and over-thinned as much as possible, and the beating time is 15 to 30 minutes, preferably 20 minutes.

[0069] In the present invention, the mass ratio of the inorganic filler to the polylactic acid in the fresh-keeping material is 30-40:75-95, preferably 35:80;

[0070] The amount of the dispersant added is 0.1 to 5 wt % of the fresh-keeping paper substrate, preferably 1 to 3 wt %, and more preferably 2 wt %;

[0071] The amount of the adhesive added is 10-30 wt % of the fresh-keeping paper substrate, preferably 15-25 wt %, and more preferably 20 wt %.

[0072] In the present invention, in step 2), the particle size of the fresh-keeping material is 250-300 mesh, preferably 280 mesh;

[0073] The banburying temperature is 150-190°C, preferably 170°C, the banburying time is 5-40 min, preferably 10-20 min, more preferably 15 min, and the banburying speed is 20-60 rpm, preferably 40 rpm;

[0074] The extrusion temperature is 160-190°C, preferably 180°C.

[0075] In the present invention, in step 3), the calendering temperature is 50-70°C, preferably 55-65°C, and more preferably 60°C, and the calendering line pressure is 20-60 kN / m, preferably 30-50 kN / m, and more preferably 40 kN / m.

[0076] The invention provides a fresh-keeping paper prepared by the preparation method.

[0077] In the present invention, the combination of long and short fibers makes the cling paper have better flexibility, the preservative in the cling paper base material also has the function of filler, and the combination of the base material and the sealing material enhances the structural strength of the cling paper to a certain extent, effectively preventing the shell of fruits and vegetables from piercing the cling paper.

[0078] The present invention also provides an application of the fresh-keeping material in preparing a fresh-keeping paper box. The fresh-keeping material and chitosan are dispersed in dichloromethane to obtain a coating liquid, and the coating liquid is applied to the inner surface of a corrugated paper box and then dried.

[0079] In the present invention, the concentration of the coating solution is preferably 20 to 60 wt %.

[0080] The present invention also provides an application of the fresh-keeping material in preparing a fresh-keeping film. The fresh-keeping material is mixed with dichloromethane, and then subjected to defoaming, film casting and drying to obtain the fresh-keeping film.

[0081] In the fresh-keeping material, the mass ratio of polylactic acid with a number average molecular weight of 100 to 300 to polylactic acid with a number average molecular weight of 300 to 20000 is 0.01 to 0.2:1, preferably 0.05 to 0.15:1, and more preferably 0.1:1.

[0082] In the present invention, when the fresh-keeping material is used to prepare the fresh-keeping film, the small molecule polylactic acid is mixed with the large molecule polylactic acid, so that the long chain segment is separated by the small block segment. After the solvent evaporates, micropores are generated in the fresh-keeping film structure, and the air permeability of the fresh-keeping film is relatively improved. The air permeability of polylactic acid is good, and it is suitable for the preservation of fruits and vegetables. The polylactic acid and the fresh-keeping material cooperate with each other, which not only creates a good fresh-keeping environment, but also improves the water vapor permeability, and also avoids the excessively high concentration of carbon dioxide generated by the decomposition of ethylene, which leads to physiological disorders and quality deterioration of fruits and vegetables.

[0083] In the present invention, the number and size of tiny pores in the cling film structure are controlled by controlling the ratio of polylactic acid with different molecular weights, achieving a good balance between oxygen blocking and carbon dioxide emission, and maintaining the concentration of carbon dioxide under the most suitable preservation conditions.

[0084] The technical solutions provided by the present invention are described in detail below in conjunction with the embodiments, but they should not be construed as limiting the protection scope of the present invention.

[0085] Example 1

[0086] A preservative is prepared with copper chloride and lanthanum chloride as the main active component and the auxiliary active component respectively in a molar ratio of 1:0.27, kaolin as a carrier, and sodium hypochlorite as an oxidant component, wherein the content of the catalyst active component is 18.98% of the weight of the carrier, and the content of the oxidant component is 5.0% of the weight of the carrier.

[0087] 35 parts of bamboo segments and 50 parts of bagasse were crushed, boiled, washed and pulped to obtain a slurry with a viscosity of 4 mPa / s, which was then paper-formed and dried to obtain a sealing material with a moisture content of 10%;

[0088] 8 parts of a preservative with a particle size of 300 mesh, 80 parts of polylactic acid, 20 parts of calcium carbonate, 20 parts of wollastonite, 25 parts of chitosan and 3 parts of ethylene distearate are added to an internal mixer, and the mixture is internally kneaded at 180° C. and 50 rpm for 30 min to form granules, and then extruded at 160° C. to obtain a masterbatch, and the obtained masterbatch is sequentially passed through a paper machine and a stretching machine for paper sample treatment, and cooled naturally to obtain a fresh-keeping paper substrate;

[0089] A chitosan aqueous solution with a concentration of 10 wt% is coated on a fresh-keeping paper substrate, and sealing materials are bonded to both sides of the fresh-keeping paper substrate respectively, and calendered at 70° C. at a line speed of 50 kN / m to obtain the fresh-keeping paper.

[0090] Example 2

[0091] In this embodiment, the preservative is the same as that in Embodiment 1.

[0092] Take 50 parts of bamboo segments and 40 parts of bagasse, crush, cook, wash and pulp them in sequence to obtain a slurry with a viscosity of 6 mPa / s, then paper-make and dry them in sequence to obtain a sealing material with a moisture content of 10%;

[0093] 5 parts of preservative, 75 parts of polylactic acid, 17 parts of calcium carbonate, 28 parts of wollastonite, 20 parts of chitosan and 6 parts of ethylene distearate are added to an internal mixer, and granulated at 150° C. and 20 rpm for 40 minutes, and then extruded at 180° C. to obtain a masterbatch, and the obtained masterbatch is sequentially passed through a paper machine and a stretching machine for paper sample treatment, and cooled naturally to obtain a fresh-keeping paper substrate;

[0094] An 8 wt % chitosan-gelatin aqueous solution (the mass ratio of chitosan to gelatin is 1:1) is coated on a cling paper substrate, and sealing materials are bonded to both sides of the cling paper substrate, and calendered at 50° C. at a line speed of 60 kN / m to obtain the cling paper.

[0095] Example 3

[0096] In this embodiment, the preservative of Example 1 is selected.

[0097] Take 30 parts of bamboo segments and 50 parts of bagasse, crush, cook, wash and pulp them in sequence to obtain a slurry with a viscosity of 3mPa / s, then paper-make and dry them in sequence to obtain a sealing material with a moisture content of 10%;

[0098] 3 parts of preservative, 80 parts of polylactic acid, 15 parts of calcium carbonate, 20 parts of wollastonite, 17 parts of gum arabic and 4 parts of ethylene distearate were added to an internal mixer, and granulated at 150° C. and 60 rpm for 10 min, and then extruded at 160° C. to obtain a masterbatch, and the obtained masterbatch was sequentially passed through a paper machine and a stretching machine for paper sample treatment, and naturally cooled to obtain a fresh-keeping paper substrate;

[0099] A chitosan-gelatin aqueous solution with a concentration of 15wt% (the mass ratio of chitosan to gelatin is 1:1) is coated on the cling paper substrate, and the sealing material is bonded to both sides of the cling paper substrate respectively, and calendered at 60°C at a line speed of 20kN / m to obtain the cling paper.

[0100] Example 4

[0101] The fresh-keeping paper obtained in Example 1 is bonded to the inner surface of a Class A corrugated paper box to obtain a fresh-keeping paper box.

[0102] Example 5

[0103] Mix 8 parts of preservative, 80 parts of polylactic acid and dichloromethane solvent, stir at 820r / min at 60℃ for 30min to remove bubbles, pour into a clean glass plate, naturally cast into a film, and then ventilate and dry for 2h to obtain a preservative film.

[0104] Application Example 1

[0105] In this application example, the fresh-keeping paper of Example 1 is selected.

[0106] The most suitable preservation temperature for ripe cherries is generally -1 to 1°C. They can be preserved for about 6 to 10 weeks under reduced pressure conditions. If the cherries are selected as storage-resistant varieties, the shelf life will be extended. The present invention selects Chinese cherries with poor storage resistance as experimental subjects. The method of using cling film to preserve cherries is as follows: take a Class A corrugated cardboard box of appropriate size, and the bottom of the cardboard box is composed of a layer of soft lining and a layer of cling film from bottom to top. The Chinese cherry variety, which is produced in abundance in Zhengzhou, is used as the experimental object. Healthy, ripe cherries with stalks are picked and placed in the cardboard box. The volume of the cherries accounts for about one-third of the cardboard box. The cherries are covered with cling film and stored at -1°C. The relative humidity of the environment is 90% and the carbon dioxide concentration is 20%.

[0107] Application Example 2

[0108] Different from Application Example 1, in this application example, the Class A corrugated paper box is replaced with the fresh-keeping paper box of Example 4.

[0109] Comparative Example 1

[0110] Different from Application Example 1, in this comparative example, sulfur dioxide cling paper commonly available on the market is used.

[0111] Comparative Example 2

[0112] Different from Application Example 1, in this comparative example, snow pear paper was used.

[0113] Table 1 shows the changes in the ripe cherries preserved in Application Example 1, Application Example 2, Control Example 1 and Control Example 2, respectively, and the corresponding preservation days when the changes occur.

[0114] Table 1 Changes in the fresh-keeping conditions and the fresh-keeping days of ripe cherries in Application Examples 1-2 and Control Examples 1-2

[0115]

[0116]

[0117] As shown in Table 1, the fresh-keeping period of Application Example 1 far exceeds that of Reference Example 1, which indicates that the fresh-keeping paper of the present invention has a better fresh-keeping ability than the sulfur dioxide fresh-keeping paper sold on the market. Moreover, according to the changes in fruit morphology and taste, when the cherry color is dark red, the compactness is reduced, and the taste is sweet and acid-free, it indicates that the fruit maturity is high. At this time, the ethylene generation ability of the fruit begins to have a trend of substantial growth. The fruit changes of Reference Examples 1 and 2 gradually accelerate, proving that it cannot decompose ethylene. Although the fresh-keeping ability is good, it cannot further inhibit the ripening of the fruit in the middle and late stages of fruit ripening; Reference Example 2 uses snow pear paper for fresh-keeping, and the fruit fresh-keeping ability is poor. This is because the snow pear paper does not have a fresh-keeping component, and the water absorption capacity is poor. The moisture produced by the respiration of the fruit cannot be absorbed or eliminated, and the ripening of the cherry is accelerated in the middle and late stages of fresh-keeping. In contrast, Application Examples 1 and Application Examples 2 effectively inhibit the further ripening of the fruit. This is because the fresh-keeping material of the present invention has the ability to decompose ethylene and the ability to absorb water, and can be used together with the fresh-keeping paper box to further extend the fresh-keeping period.

[0118] As can be seen from the above embodiments, the present invention provides a fresh-keeping material and its application, a fresh-keeping paper and its preparation method and application. The present invention combines a fresh-keeping material with ethylene decomposition ability with a papermaking process to prepare fresh-keeping paper and fresh-keeping paper boxes with ethylene decomposition ability, with a simple preparation process and low cost, and solves the technical problems in the prior art that fresh-keeping materials have poor bactericidal and antibacterial abilities, do not have ethylene decomposition effects, have poor mildew resistance, are high in cost, and have complicated processes.

[0119] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A fresh-keeping material, characterized in that: The invention is composed of the following components in parts by weight: 75 to 95 parts of polylactic acid and 3 to 8 parts of a preservative; The preservative is prepared from an active component precursor, a carrier and an oxidant; The active component precursor includes a main active component precursor and an auxiliary active component precursor, wherein the main active component precursor is a chloride of a transition metal element, and the auxiliary active component precursor is a chloride of a rare earth element; the carrier is one or a combination of two or more selected from porous alumina, titanium oxide, montmorillonite, kaolin, and molecular sieves; the oxidant is one or a combination of two or more selected from sodium hypochlorite, sodium chlorite, and hexadecyl trichloroacetate; The number average molecular weight of the polylactic acid is 100 to 20,000.

2. A fresh-keeping material according to claim 1, characterized in that: The content of the active component is 0.1-20% of the weight of the carrier; the molar ratio of the main active component to the auxiliary active component is 1:0-0.5; and the content of the oxidant is 2-10% of the weight of the carrier.

3. A method for preparing fresh-keeping paper from the fresh-keeping material according to claim 1 or 2, characterized in that: The following steps are involved: Step 1), crushing, boiling, washing, beating, papermaking and drying the bamboo segments and bagasse in sequence to obtain the sealing material; Step 2), mixing the fresh-keeping material, inorganic filler, adhesive and dispersant, and subjecting the mixture to banburying, extrusion and paper-like treatment to obtain a fresh-keeping paper substrate; Step 3), using an adhesive to bond the sealing material, the cling paper substrate and the sealing material in the structural order, and then calendering to obtain the cling paper; The inorganic filler includes wollastonite and / or calcium carbonate; The adhesive comprises one or more of chitosan, gelatin and gum arabic.

4. The method for preparing a cling film according to claim 3, characterized in that: In step 1), the mass ratio of the bamboo segments to the bagasse is 30-40:25-50; The viscosity of the slurry is 3 to 6 mPa / s; The drying temperature is 70-110° C., and the drying time is 3-8 hours.

5. The method for preparing a cling film according to claim 4, characterized in that: In step 2), the mass ratio of the inorganic filler to the polylactic acid in the fresh-keeping material is 30-40:75-95; The added amount of the dispersant is 0.1 to 5 wt % of the fresh-keeping paper base material; The added amount of the adhesive is 10-30wt% of the fresh-keeping paper base material.

6. A method for preparing a cling film according to claim 4 or 5, characterized in that: In step 2), the particle size of the fresh-keeping material is 250-300 mesh, the banburying temperature is 150-190° C., the banburying time is 5-40 min, and the banburying speed is 20-60 rpm; The extrusion temperature is 160-190°C.

7. The method for preparing a cling film according to claim 6, characterized in that: In step 3), the calendering temperature is 50-70° C., and the calendering line pressure is 20-60 kN / m.

8. Fresh-keeping paper prepared by the preparation method according to any one of claims 3 to 7.

9. Use of the fresh-keeping paper according to claim 8 in preparing fresh-keeping paper boxes, characterized in that: Just glue the paper to the inner surface of the corrugated box.

10. Use of the fresh-keeping material according to claim 1 or 2 in preparing fresh-keeping film, characterized in that: The fresh-keeping material is mixed with dichloromethane, and then the fresh-keeping film is obtained after degassing, film casting and drying; In the fresh-keeping material, the mass ratio of the polylactic acid with a number average molecular weight of 100 to 300 to the polylactic acid with a number average molecular weight of 300 to 20000 is 0.01 to 0.2:1.

Images