Chlorine dioxide slow-release fresh-keeping card and preparation method and application thereof

Abstract

The application discloses a chlorine dioxide slow-release fresh-keeping card and a preparation method and application thereof, and belongs to the technical field of fruit and vegetable fresh-keeping. The ClO2 slow-release fresh-keeping card is a first water-absorbing card paper layer, a water-based adhesive layer and a second water-absorbing card paper layer which are sequentially and layer by layer arranged. In a certain proportion, the first water-absorbing card paper layer comprises first water-absorbing card paper, sodium chlorite and a first water-absorbing agent loaded on the first water-absorbing card paper; the second water-absorbing card paper layer comprises second water-absorbing card paper, an organic weak acid and a second water-absorbing agent loaded on the second water-absorbing card paper; the organic weak acid is selected from one or more of oxalic acid, citric acid and tartaric acid; and the first water-absorbing agent and the second water-absorbing agent are respectively selected from one or more of calcium chloride, sodium sulfate and magnesium sulfate. The ClO2 slow-release fresh-keeping card has good bacteriostatic fresh-keeping effect in fruit and vegetable fresh-keeping application, ClO2 release is more stable and durable, powder leakage is avoided, and the card can also have the characteristics of visualization and the like.

Description

Technical Field

[0001] This invention relates to the field of fruit and vegetable preservation technology, and in particular to a chlorine dioxide slow-release preservation card, its preparation method, and its application. Background Technology

[0002] Chlorine dioxide (ClO2) is an inorganic compound with broad-spectrum and highly efficient sterilization properties, making it a novel preservative for fruits and vegetables. It can disrupt the electron transport chain of microorganisms, oxidize their amino acids, and render them inactive, thus achieving sterilization and disinfection of the fruit and vegetable surface. Secondly, ClO2 can prevent methionine from decomposing into ethylene and destroy existing ethylene formation, thereby delaying the spoilage of fruits and vegetables without damaging their structure. Therefore, ClO2 is considered a highly efficient and safe preservative for fruits and vegetables. However, there are still some technical challenges and difficulties in the application of ClO2 in fruit and vegetable preservation, such as how to more conveniently produce gaseous ClO2 and how to stably control the concentration of gaseous ClO2.

[0003] In recent years, slow-release preservatives that automatically release ClO2 without requiring large-scale equipment have attracted widespread attention. The core of this process lies in the conversion of sodium chlorite (NaClO2) to chlorite (HClO2), thereby generating ClO2. To achieve this process, hydrogen ions (H+) need to be provided to sodium chlorite. + Most reported ClO2 slow-release preservatives are in powder form, primarily composed of NaClO2 and weak organic acids, and are packaged in non-woven bags for use. Although various weak organic acids have been used as H... + The donor, but during use, the powdered ClO2 preservative in the non-woven bag will instantly initiate a reaction upon contact with water droplets, resulting in a high concentration of H... + This can easily lead to a large initial release of ClO2, causing an explosive release and bleaching effect on fruits and vegetables, thus affecting their shelf life. Therefore, ClO2 slow-release preservatives urgently need to improve their reliability to meet the higher demands of the fruit and vegetable preservation market. Summary of the Invention

[0004] To address the problem of explosive release of existing ClO2 slow-release preservatives when used for fruit and vegetable preservation, this invention provides a safe and efficient ClO2 slow-release preservation card, as well as its preparation method and application. This ClO2 slow-release preservation card has a good antibacterial and preservation effect in fruit and vegetable preservation applications, and the ClO2 release is more stable and lasting, without powder leakage.

[0005] This invention provides a chlorine dioxide slow-release preservation card, comprising a first absorbent cardboard layer, a water-based adhesive layer, and a second absorbent cardboard layer that are sequentially stacked and covered.

[0006] The first absorbent paper layer comprises: a first absorbent paper and sodium chlorite and a first absorbent agent loaded on the first absorbent paper; the second absorbent paper layer comprises: a second absorbent paper and an organic weak acid and a second absorbent agent loaded on the second absorbent paper;

[0007] The organic weak acid is selected from one or more of oxalic acid, citric acid, and tartaric acid; the first water-absorbing agent and the second water-absorbing agent are respectively selected from one or more of calcium chloride, sodium sulfate, and magnesium sulfate; the molar ratio of sodium chlorite to the first water-absorbing agent is 20:1 to 2, the molar ratio of the organic weak acid to the second water-absorbing agent is 20:1 to 2, and the molar ratio of sodium chlorite to the organic weak acid is 2:1 to 2.

[0008] Preferably, the water-based adhesive layer is a gelatin layer.

[0009] Preferably, the first absorbent paper and the second absorbent paper have the same specifications.

[0010] Preferably, the second absorbent paper also contains a pH-sensitive colorimetric indicator.

[0011] Preferably, the colorimetric indicator is a compound of natural pigment and β-cyclodextrin in a mass ratio of 10 to 15:1.

[0012] Preferably, the non-adhesive surfaces of the first absorbent cardboard layer and the second absorbent cardboard layer are respectively covered with a microporous plastic film layer.

[0013] This invention provides a method for preparing the chlorine dioxide slow-release preservation card as described above, which includes the following steps:

[0014] S1. Immerse a piece of absorbent cardboard in a mixed solution containing sodium chlorite and a first absorbent agent, and dry it after a certain period of time to obtain a first absorbent cardboard loaded with sodium chlorite and a first absorbent agent; immerse another piece of absorbent cardboard in a mixed solution containing an organic weak acid and a second absorbent agent, and dry it after a certain period of time to obtain a second absorbent cardboard loaded with an organic weak acid and a second absorbent agent.

[0015] S2. The first absorbent card and the second absorbent card are laminated and bonded together with a water-based adhesive, pressed and dried to obtain a chlorine dioxide slow-release preservation card.

[0016] Preferably, in step S1, the immersion time for forming the first absorbent card and the second absorbent card is 1 to 2 hours, and the drying is carried out at 40 to 60°C for 3 to 5 hours.

[0017] Preferably, in step S2, the pressure for pressing is 0.5–0.8 MPa and the time is 1–5 min; the drying is carried out at 40–60°C for 1–2 h.

[0018] Furthermore, this invention provides the application of the chlorine dioxide slow-release preservation card as described above in the preservation of fruits and vegetables.

[0019] Compared with existing technologies, this invention provides a novel ClO2 slow-release preservation card, which mainly consists of three parts: a first absorbent paper layer, a water-based adhesive layer, and a second absorbent paper layer. Both the first and second absorbent paper layers use absorbent paper as a carrier for the reaction reagents. Sodium chlorite and a first absorbent agent are uniformly adsorbed and loaded on the surface and interior of the first absorbent paper in a specific ratio, while an organic weak acid and a second absorbent agent are uniformly adsorbed and loaded on the surface and interior of the second absorbent paper in a specific ratio. Furthermore, the organic weak acid is one or more of oxalic acid, citric acid, and tartaric acid; the first and second absorbent agents are one or more of calcium chloride, sodium sulfate, and magnesium sulfate, respectively. The ClO2 slow-release preservation card of this invention adds a certain proportion of absorbent agent, which can continuously and slowly absorb trace amounts of moisture in the air and initiate the chemical reaction between sodium chlorite and the organic weak acid to produce ClO2, avoiding the explosive release of ClO2 in the powdered reaction system. Moreover, the absorbent paper also provides good isolation between water droplets and chemical reagents, further preventing the explosive release of ClO2.

[0020] Furthermore, the reagent carrier of the present invention is a paper card, and the reaction reagent is loaded in the absorbent cardboard, which can avoid the risk of chemical reagents coming into direct contact with fruits and vegetables due to powder leakage, making it safer.

[0021] Furthermore, to achieve visualization, a color indicator is added to the ClO2 slow-release preservation card of the present invention. The preferred natural pigment is pH sensitive and easily oxidized and faded, which can visualize the colorless and odorless ClO2 slow-release process, making it convenient for consumers to use. Attached Figure Description

[0022] Figure 1 The diagram shows the ClO2 release rate of the ClO2 slow-release preservation cards in Examples 1-3 of this invention. Detailed Implementation

[0023] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. Unless otherwise defined, all technical terms used herein have the same meaning as commonly understood by those skilled in the art. The technical terms used herein are for the purpose of describing specific embodiments only and are not intended to limit the scope of protection of this invention. Unless otherwise specified, all reagents and raw materials used in this invention are commercially available products or products that can be prepared by recognized methods.

[0024] This invention provides a chlorine dioxide slow-release preservation card, comprising a first absorbent cardboard layer, a water-based adhesive layer, and a second absorbent cardboard layer stacked and covered sequentially; the first absorbent cardboard layer comprises: a first absorbent cardboard and sodium chlorite and a first absorbent agent loaded on the first absorbent cardboard; the second absorbent cardboard layer comprises: a second absorbent cardboard and an organic weak acid and a second absorbent agent loaded on the second absorbent cardboard;

[0025] The organic weak acid is selected from one or more of oxalic acid, citric acid, and tartaric acid; the first water-absorbing agent and the second water-absorbing agent are respectively selected from one or more of calcium chloride, sodium sulfate, and magnesium sulfate; the molar ratio of sodium chlorite to the first water-absorbing agent is 20:1 to 2, the molar ratio of the organic weak acid to the second water-absorbing agent is 20:1 to 2, and the molar ratio of sodium chlorite to the organic weak acid is 2:1 to 2.

[0026] In fruit and vegetable preservation applications, the chlorine dioxide (ClO2) slow-release preservation card provided by this invention has a good antibacterial and preservation effect, and the release of ClO2 is more stable and longer-lasting, without problems such as powder leakage.

[0027] This invention relates to a novel ClO2 slow-release preservation card for fruits and vegetables. The main reaction system components of this card are sodium chlorite, a weak organic acid, and a desiccant; preferably, it also includes a colorimetric indicator. The sodium chlorite (NaClO2) serves as a precursor, primarily providing the ClO2 precursor to the reaction system. - The organic weak acid is one or more of oxalic acid, citric acid, and tartaric acid, preferably oxalic acid, which mainly provides H₂ for the reaction system. + The desiccant primarily provides solvent water to the reaction system and initiates the ionic reaction. It includes one or more of sodium sulfate (Na₂SO₄), calcium chloride (CaCl₂), and magnesium sulfate (MgSO₄), with calcium chloride being preferred. The reaction system reacts as follows: 4NaClO₂ + 2H₂O + =4Na + +2ClO2↑+ClO3 - +Cl - +H2O.

[0028] Its working principle is as follows: on the one hand, desiccant such as calcium chloride absorbs trace amounts of moisture in the air, and on the other hand, weak organic acids such as oxalic acid slowly ionize H+. +This promotes the continuous and stable chemical reaction of NaClO2 to produce ClO2. On the other hand, in a preferred embodiment of the invention, the colorimetric indicator is a compound of natural pigment and β-cyclodextrin in a mass ratio of 10–15:1; further, a red natural pigment (64.5% glycerol, 5% red yeast rice, 2.8% carmine, 27.7% water) and β-cyclodextrin are used, compounded in a ratio of 15:1 to 10:1 to form the colorimetric indicator. The preferred natural pigment exhibits different colors at different pH levels and is easily oxidized and faded, ensuring more sensitive and safer color development; β-cyclodextrin, as an encapsulating agent, enhances the antioxidant capacity of the natural pigment, resulting in more stable color development.

[0029] Low-concentration ClO2 is colorless and odorless, making it impossible for consumers to visually determine the concentration of the prepared ClO2. In some preferred embodiments of this invention, the color indicator is pH-sensitive and easily oxidized and fades. During use, as the pH gradually increases and ClO2 continuously oxidizes the natural pigments, the color indicator changes from a deep yellow after drying to a light yellow, and eventually becomes colorless. This invention preferably provides a visual ClO2 slow-release preservation card that can slowly absorb moisture under different temperature and humidity conditions, continuously and stably providing H2O to NaClO2. + It is used in the ClO2 generation reaction to achieve a more stable and sustained ClO2 release, while also making it convenient for consumers to observe the ClO2 slow-release process.

[0030] Furthermore, the ClO2 slow-release preservation card of this invention uses absorbent paper as the reagent carrier. The main card structure consists of a first absorbent paper layer loaded with sodium chlorite and a first absorbent agent, a second absorbent paper layer loaded with an organic weak acid and a second absorbent agent, and an aqueous adhesive layer between the two. Two absorbent papers of the same specifications can be used to load the chemical reagents; for easy distinction, they are respectively referred to as the first absorbent paper and the second absorbent paper, and the absorbent agents on the two absorbent paper layers are respectively referred to as the first absorbent agent and the second absorbent agent.

[0031] The absorbent cardboard (2mm thick, 40*40mm) described in this embodiment of the invention can not only uniformly absorb the loaded reaction system, but also has a certain strength and hardness, making it less likely to be damaged and cause direct contact between chemical reagents and food. It can also provide good isolation between water droplets and chemical reagents, further preventing the explosive release of ClO2 and making it safer.

[0032] In embodiments of the present invention, the first absorbent paper layer is loaded with sodium chlorite and a first absorbent agent, and the second absorbent paper layer is loaded with an organic weak acid and a second absorbent agent; preferably, the first and second absorbent agents are of the same type. For the reaction system, the molar ratio of sodium chlorite to the first absorbent agent is 20:1 to 2, preferably 20:1; the molar ratio of the organic weak acid to the second absorbent agent is 20:1 to 2, preferably 20:1; the molar ratio of sodium chlorite to the organic weak acid is 2:1 to 2, preferably 2:1. This reaction system works synergistically to continuously and slowly release chlorine dioxide.

[0033] In addition, the second absorbent card also contains a pH-sensitive colorimetric indicator; the slow release of ClO2 can be visualized through the color change of the indicator on the preservation card, making the chemical reaction visible. As mentioned earlier, the colorimetric indicators are all natural products, safe for direct contact with fruits and vegetables, and pose no food safety risk.

[0034] In this embodiment of the invention, a water-based adhesive layer completely covers the first and second absorbent paperboards, bonding them together to form a single unit. This provides a certain degree of fixation for the reagents inside the absorbent paperboards. Preferably, the water-based adhesive layer is a gelatin layer with a mass fraction of 50%.

[0035] Furthermore, the non-adhesive surfaces of the first absorbent cardboard layer and the second absorbent cardboard layer are preferably also covered with a microporous plastic film layer, which can ensure the slow release of ClO2 while effectively preventing direct contact between chemical reagents and food.

[0036] This invention provides a method for preparing the ClO2 slow-release preservation card as described above, comprising the following steps:

[0037] S1. Immerse a piece of absorbent cardboard in a mixed solution containing sodium chlorite and a first absorbent agent, and dry it after a certain period of time to obtain a first absorbent cardboard loaded with sodium chlorite and a first absorbent agent; immerse another piece of absorbent cardboard in a mixed solution containing an organic weak acid and a second absorbent agent, and dry it after a certain period of time to obtain a second absorbent cardboard loaded with an organic weak acid and a second absorbent agent.

[0038] S2. The first absorbent card and the second absorbent card are laminated and bonded together with a water-based adhesive, pressed and dried to obtain a ClO2 slow-release preservation card.

[0039] In some preferred embodiments of the present invention, the specific steps of the preparation method of the visualized ClO2 slow-release preservation card are as follows: 2 mol / L sodium chlorite is mixed with an equal volume of 0.1-0.2 mol / L first desiccant to obtain a sodium chlorite mixed solution for later use; 2 mol / L organic weak acid, 0.1-0.2 mol / L second desiccant, and colorimetric indicator are mixed with an equal volume to obtain an organic weak acid mixed solution for later use;

[0040] First, two absorbent paper sheets (2mm thick, 40*40mm) are immersed in a sodium chlorite mixed solution and an organic weak acid mixed solution, respectively, for 1-2 hours to ensure that the components of the reaction system are completely adsorbed onto the absorbent paper sheets. Then, they are dried at 40-60℃ for 3-5 hours. Next, the two dried absorbent paper sheets are bonded together with 50% gelatin by mass and squeezed under a pressure of 0.5-0.8MPa for 1-5 minutes. After being pressed and formed, the ClO2 slow-release preservation card is dried at 40-60℃ to obtain the final product.

[0041] In this invention, all reagent raw materials are commercially available conventional products; the pressure for pressurization is preferably 0.6 MPa, and the time is 3 min. The ClO2 slow-release preservation card described in this invention has a simple composition, is easy to prepare, and has a low cost, making it suitable for industrial production and widespread application.

[0042] The embodiments of the present invention also provide the application of the ClO2 slow-release preservation card in the preservation of fruits and vegetables as described above; for example, the visualized ClO2 slow-release preservation card is placed in a foam box containing 2 kg of fruits and vegetables (such as lychees and longans) and stored in a sealed container.

[0043] Testing showed that the ClO2 slow-release preservation card of this invention slowly releases ClO2 for over 96 hours, exhibiting good stability and effectively extending the shelf life of fruits and vegetables. It also allows for convenient monitoring by consumers. The preparation process of the ClO2 slow-release preservation card described in this invention is simple, possesses excellent ClO2 slow-release and preservation effects, is safe, efficient, and highly operable, meeting the needs of e-commerce distribution of fruits and vegetables and possessing high commercial value.

[0044] To better illustrate the present invention, further examples are provided below. In the following examples, the main raw materials and reagents used are commercially available and conventional.

[0045] Example 1

[0046] A visualized ClO2 slow-release preservation card, its preparation method, and its application, specifically including the following steps:

[0047] (1) Preparation of colorimetric indicator: Red natural pigment (mass ratio: 64.5% glycerol, 5% red yeast rice, 2.8% carmine, 27.7% water) and β-cyclodextrin are mixed in a ratio of 15:1 to form a solution.

[0048] (2) Preparation of reaction system: Sodium chlorite mixed solution: Mix 2 mol / L sodium chlorite and 0.1 mol / L calcium chloride in equal volumes for later use; Oxalic acid mixed solution: Mix 2 mol / L oxalic acid, 0.1 mol / L calcium chloride and color indicator in equal volumes for later use.

[0049] (3) Preparation and use of the visualized ClO2 slow-release preservation card: First, two absorbent paper sheets (2mm thick, 40*40mm) were immersed in the reaction system of sodium chlorite mixed solution and oxalic acid mixed solution for 1 hour respectively; then dried at 60℃ for 4 hours. The two dried absorbent paper sheets were glued together with 50% gelatin and pressed under 0.6MPa pressure for 3 minutes to form the shape. Finally, the ClO2 slow-release preservation card was dried at 60℃ for 2 hours to complete the preparation.

[0050] The visual ClO2 slow-release preservation card was placed in a foam box containing 2 kg of fruits and vegetables, sealed, and the preservation effect was evaluated.

[0051] Example 2

[0052] A visualized ClO2 slow-release preservative, its preparation method and application, specifically including the following steps:

[0053] (1) Preparation of colorimetric indicator: Red natural pigment (mass ratio: 64.5% glycerol, 5% red yeast rice, 2.8% carmine, 27.7% water) and β-cyclodextrin are mixed in a ratio of 15:1 to form a solution.

[0054] (2) Preparation of reaction system: Sodium chlorite mixed solution: Mix 2 mol / L sodium chlorite and 0.1 mol / L calcium chloride in equal volumes for later use; Citric acid mixed solution: Mix 2 mol / L citric acid, 0.1 mol / L calcium chloride and color indicator in equal volumes for later use.

[0055] (3) Preparation and use of the visualized ClO2 slow-release preservation card: First, two absorbent paper sheets (2mm thick, 40*40mm) were immersed in the sodium chlorite mixed solution and citric acid mixed solution of the reaction system for 1 hour respectively; then dried at 60℃ for 4 hours. The two dried absorbent paper sheets were glued together with 50% gelatin and pressed under 0.6MPa pressure for 3 minutes to form the shape. Finally, the ClO2 slow-release preservation card was dried at 60℃ for 2 hours to complete the preparation.

[0056] The visual ClO2 slow-release preservation card was placed in a foam box containing 2 kg of fruits and vegetables, sealed, and the preservation effect was evaluated.

[0057] Example 3

[0058] A visualized ClO2 slow-release preservation card, its preparation method, and its application, specifically including the following steps:

[0059] (1) Preparation of colorimetric indicator: Red natural pigment (mass ratio: 64.5% glycerol, 5% red yeast rice, 2.8% carmine, 27.7% water) and β-cyclodextrin are mixed in a ratio of 10:1 to form a solution.

[0060] (2) Preparation of reaction system: Sodium chlorite mixed solution: Mix 2 mol / L sodium chlorite and 0.1 mol / L Na2SO4 in equal volumes for later use; Oxalic acid mixed solution: Mix 2 mol / L oxalic acid, 0.1 mol / L Na2SO4 and color indicator in equal volumes for later use.

[0061] (3) Preparation and use of the visualized ClO2 slow-release preservation card: First, two absorbent paper sheets (2mm thick, 40*40mm) were immersed in the reaction system of sodium chlorite mixed solution and oxalic acid mixed solution for 1 hour respectively; then dried at 60℃ for 4 hours. The two dried absorbent paper sheets were glued together with 50% gelatin and pressed under 0.6MPa pressure for 3 minutes to form the shape. Finally, the ClO2 slow-release preservation card was dried at 60℃ for 2 hours to complete the preparation.

[0062] The visual ClO2 slow-release preservation card was placed in a foam box containing 2 kg of fruits and vegetables, sealed, and the preservation effect was evaluated.

[0063] Comparative Example

[0064] A ClO2 slow-release preservative with no display function and citric acid as the main raw material, specifically including the following steps:

[0065] (1) Preparation of reaction system: Weigh a certain amount of dried precursor (NaClO2), citric acid, desiccant (silica gel), and stabilizer (diatomaceous earth), and vortex mix them at 1500r / min for 2 minutes in a mass ratio of 3:1:1:1, and set aside.

[0066] (2) Preparation and use of ClO2 slow-release preservative: The reaction system was placed in a non-woven bag and sealed. The ClO2 slow-release preservative was placed in a foam box containing 2 kg of fruits and vegetables, sealed and stored, and the preservation effect was evaluated.

[0067] The ClO2 release rates of the above three embodiments and one comparative example are as follows: Figure 1As shown in the figure, the test conditions were the same. The comparative example showed a maximum ClO2 release rate of 0.81 mg / h at 24 hours, which then dropped sharply to 0.29 mg / h at 36 hours, with a longest release period of 72 hours. All three examples effectively suppressed the explosive release of ClO2 (Example 1 showed the best effect), and all exhibited two release peaks, with the longest release period exceeding 96 hours, providing a more stable and longer-lasting ClO2 gas supply for fruit and vegetable preservation.

[0068] One ClO2 slow-release preservation card from each of Examples 1, 2, and 3 was used to preserve 2 kg of lychees. A ClO2 slow-release preservative with no display function and citric acid as the main raw material was used as a control. Quality indicators were measured every 3 days during storage. Determination of peel brightness (L*): Ten fruits were taken from each group, and the surface of the fruit was measured diagonally in four directions from the equator using an NS800 spectrophotometer. The larger the L* value, the brighter the sample surface. Determination of peel respiration rate: Five fruits were taken from each group, and the respiration rate of each fruit was measured 5 times using a fruit and vegetable respiration rate meter. The average value was calculated. Determination of soluble solids (TSS) in pulp: Five fruits were taken from each group, and the refractometer method was used for determination according to NY / T2637-2014 "Determination of Soluble Solids Content in Fruits and Vegetables". Each fruit was measured twice, for a total of 10 measurements, and the average value was calculated.

[0069] The testing indicators are shown in the table below:

[0070] Table 1. Test results of lychee preservation using slow-release preservation cards in the embodiments of the present invention.

[0071]

[0072] As shown in the table above, the luminance L* values ​​of the litchi treated in each example were all greater than those of the comparative example during storage, indicating that the ClO2 slow-release preservation card can effectively reduce the occurrence of fruit browning. After 9 days of storage, the respiration rates of all three examples were lower than those of the comparative example, and the increase in TSS was also smaller than that of the comparative example, indicating that the ClO2 slow-release preservation card can effectively maintain the stable quality of the fruit, especially the fruit and vegetable rot caused by respiration and the increase in TSS of the pulp caused by dehydration. The indicators in all three examples were deep yellow on day 0, gradually turning light yellow or colorless on days 3 and 6, and becoming colorless by day 9, which effectively visualized the ClO2 slow-release process. However, the comparative example did not show this color change.

[0073] As can be seen from the above embodiments, the ClO2 slow-release preservation card described in this invention contains a certain proportion of absorbent material, which can continuously and slowly absorb trace amounts of moisture in the air, initiate the chemical reaction between sodium chlorite and a weak organic acid to produce ClO2, and slowly and persistently release ClO2, making it suitable for preserving fruits and vegetables. Furthermore, the absorbent paper also provides good isolation between water droplets and chemical reagents, further preventing the explosive release of ClO2. In addition, the reagent carrier of this invention is a paper card, with the reaction reagent loaded in the absorbent cardstock, making it safer. Furthermore, the natural pigments preferred in this invention are pH sensitive and easily oxidized and faded, allowing the colorless and odorless ClO2 slow-release process to be visualized, making it convenient for consumers to use.

[0074] The embodiments described above are merely preferred solutions of the present invention. All equivalent changes and modifications made within the scope of the claims of the present invention shall fall within the scope of the present invention.

Claims

1. A chlorine dioxide slow-release preservation card, characterized in that, It includes a first absorbent cardboard layer, a water-based adhesive layer, and a second absorbent cardboard layer that are sequentially stacked and covered. The first absorbent paper layer comprises: a first absorbent paper and sodium chlorite and a first absorbent agent loaded on the first absorbent paper; the second absorbent paper layer comprises: a second absorbent paper and an organic weak acid and a second absorbent agent loaded on the second absorbent paper; The organic weak acid is selected from one or more of oxalic acid, citric acid, and tartaric acid; the first absorbent and the second absorbent are selected from one or more of calcium chloride, sodium sulfate, and magnesium sulfate, respectively; the molar ratio of sodium chlorite to the first absorbent is 20:1~2, the molar ratio of the organic weak acid to the second absorbent is 20:1~2, and the molar ratio of sodium chlorite to the organic weak acid is 2:1~2; the second absorbent card is also loaded with a pH-sensitive colorimetric indicator, which is a compound of natural pigment and β-cyclodextrin in a mass ratio of 10~15:

1.

2. The chlorine dioxide slow-release preservation card according to claim 1, characterized in that, The water-based adhesive layer is a gelatin layer.

3. The chlorine dioxide slow-release preservation card according to claim 1, characterized in that, The first absorbent paper and the second absorbent paper have the same specifications.

4. The chlorine dioxide slow-release preservation card according to any one of claims 1-3, characterized in that, The non-adhesive surfaces of the first absorbent cardboard layer and the second absorbent cardboard layer are respectively covered with a microporous plastic film layer.

5. The method for preparing the chlorine dioxide slow-release preservation card according to any one of claims 1-4, characterized in that, Includes the following steps: S1. Immerse a sheet of absorbent paper in a mixed solution containing sodium chlorite and a first absorbent agent, and dry it after a certain period of time to obtain a first absorbent paper loaded with sodium chlorite and the first absorbent agent; immerse another sheet of absorbent paper in a mixed solution containing an organic weak acid and a second absorbent agent, and dry it after a certain period of time to obtain a second absorbent paper loaded with an organic weak acid and a second absorbent agent; the second absorbent paper is also loaded with a pH-sensitive colorimetric indicator, which is a compound of natural pigment and β-cyclodextrin in a mass ratio of 10~15:1; S2. The first absorbent card and the second absorbent card are laminated and bonded together with a water-based adhesive, pressed and dried to obtain a chlorine dioxide slow-release preservation card.

6. The method for preparing the chlorine dioxide slow-release preservation card according to claim 5, characterized in that, In step S1, the immersion time for forming the first absorbent card and the second absorbent card is 1-2 hours, and the drying is carried out at 40-60°C for 3-5 hours.

7. The method for preparing the chlorine dioxide slow-release preservation card according to claim 5, characterized in that, In step S2, the pressure for pressing is 0.5~0.8MPa and the time is 1~5min; the drying is carried out at 40~60℃ for 1~2h.

8. The application of the chlorine dioxide slow-release preservation card as described in any one of claims 1-4 in the preservation of fruits and vegetables.

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