A slow-release antibacterial / antioxidant smart preservation card, its preparation method and application

Abstract

This invention discloses a slow-release antibacterial / antioxidant smart preservation card, its preparation method, and its application, belonging to the field of food preservation technology. The preservation card includes a slow-release functional material layer, a freshness indicator layer, and a barrier layer; the freshness indicator layer and the barrier layer are sequentially stacked on the upper and lower surfaces of the slow-release functional material layer. The preparation method of the preservation card includes the following steps: (1) preparation of the slow-release functional material layer; (2) preparation of the freshness indicator layer; (3) preparation of the barrier layer. This invention also provides the application of the above-mentioned preservation card in food preservation. This invention addresses the phenomenon of food oxidation and spoilage by enhancing the preservation effect, improving the functionality of the preservation card, and extending the shelf life of food through the slow-release structure design of the preservation card and the addition of active substances supplemented by a smart freshness indicator effect. All materials used are food-grade, ensuring food safety.

Description

Technical Field

[0001] This invention belongs to the field of food preservation technology, and particularly relates to a slow-release antibacterial / antioxidant smart preservation card, its preparation method, and its application. Background Technology

[0002] Food spoilage is a major problem that plagues people in daily life. The main causes can be attributed to food oxidation and the proliferation of microorganisms such as mold and bacteria, leading to decay. How to extend the shelf life of food while preserving its original flavor, and reduce economic losses caused by spoilage and food safety hazards resulting from improper preservation methods, is a direction we need to consider and address.

[0003] Currently, common food preservation products on the market include preservatives, plastic wrap, and external preservation devices. Among these, chemical and biological preservatives have not been widely adopted due to cost and migration safety concerns. While widely used petroleum-based plastic wrap has demonstrated excellent preservation effects, its non-biodegradability after use places a burden on the environment. Common external preservation devices include desiccants, oxygen absorbers, and food preservation cards. In existing technologies, most food preservation cards utilize composite paper substrates impregnated with alcohol to absorb moisture within the food packaging, thus achieving antibacterial and drying effects. However, these preservatives have complex manufacturing processes, limited functionality, short shelf life, and unreliable preservation effects.

[0004] Therefore, how to provide a preservation card that is simple to prepare, has a long shelf life, and extends the shelf life of food is a technical problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention proposes a slow-release antibacterial / antioxidant smart preservation card, its preparation method, and its application.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] A slow-release antibacterial / antioxidant smart preservation card includes a slow-release functional material layer, a freshness indicator layer, and a barrier layer;

[0008] The freshness indicator layer and the barrier layer are sequentially stacked on both the upper and lower surfaces of the sustained-release functional material layer.

[0009] A method for preparing a slow-release antibacterial / antioxidant smart preservation card includes the following steps:

[0010] (1) Using bagasse fiber as the base material, and adding modified inorganic fillers and active substances, the slow-release functional material layer is prepared by papermaking technology.

[0011] (2) The active substance solution, chitosan solution, carrageenan solution and glycerin are mixed to prepare a coating liquid, which is then uniformly coated on the front and back of the sustained-release functional material layer to obtain the freshness indicator layer.

[0012] (3) Preparation of barrier layer: A uniformly perforated PE film is laminated on the surface of the freshness indicator layer as a barrier layer, and then pressed to obtain a preservation card.

[0013] Beneficial Effects: This invention utilizes active substances (such as antibacterial, antioxidant, and color-developing active substances) and a slow-release structure design to obtain a preservation card with antibacterial and antioxidant functions, extending the shelf life of food while providing a direct indication of food freshness. The core layer of the preservation card incorporates an adjustable concentration of antibacterial / antioxidant active substances, and a slow-release structure is designed for the card. The internal pore characteristics and card shape are flexibly adjustable. Therefore, the preservation card provided by this invention can achieve long-lasting and controllable antibacterial and antioxidant functions through flexible adjustment of its total active substance concentration and slow-release rate, such as adjusting porosity, card thickness / perimeter, and PE surface perforation density. This can meet the specific preservation and shelf-life requirements of different foods. In particular, the freshness indicator layer is sensitive to environmental pH; that is, when changes in food quality cause changes in the pH value of the packaging environment, the card surface can show a clear and irreversible color change in real time. Therefore, this card device also has the function of directly indicating the freshness of packaged food.

[0014] Preferably, the mass ratio of bagasse fiber, modified inorganic filler and active substance in step (1) is (20-25):(1-1.5):(0.04-0.4).

[0015] Beneficial effects: The modified inorganic filler described above can be physically adsorbed and bound into the pores of bagasse fibers, complicating the release pathway of active substances, prolonging the release time of active substances, and improving the preservation effect. Simultaneously, this invention allows for adjustment of the preservation card device structure by varying the proportions of raw materials, thereby controlling the slow-release efficiency.

[0016] Preferably, the bagasse fiber in step (1) is bagasse oven-dried pulp, which is obtained by directly cooking fresh bagasse into pulp, followed by pulping, papermaking, and filtration.

[0017] The active substances include one of curcumin, tea polyphenols, anthocyanins, rosemary extract, and basil extract;

[0018] The modified inorganic filler includes one of modified diatomaceous earth, modified kaolin, and modified bentonite.

[0019] Beneficial effects: Bagasse fiber is a medium-length fiber with moderate strength and toughness. Its internal honeycomb-like porous microstructure provides good adsorption for active substances. The rough, raised surface enhances its stability when combined with modified inorganic fillers. Furthermore, bagasse fiber is fully biodegradable within 90 days in the natural environment, making it environmentally friendly. In addition, the slow-release functional material layer of this invention contains active substances with antibacterial and antioxidant functions. The slow-release period can be controlled through the porous structure of the material and the combined effect of the slow-release agent. Moreover, the selected active substances are sensitive to changes in pH within the food packaging environment, serving as an indicator of freshness. Furthermore, the invention also incorporates modified inorganic fillers, which, as a slow-release component, effectively achieve the slow-release effect of the functional material layer.

[0020] Preferably, the preparation method of the modified inorganic filler includes the following steps:

[0021] The aqueous solution of silane coupling agent was slowly and evenly added to the inorganic filler slurry. After stirring for 1 hour, the mixture was placed in a 90°C oven and dried for 8 hours. The slurry was then passed through a 200-mesh standard sieve to obtain the modified inorganic filler.

[0022] Preferably, it is γ-aminopropyltriethoxysilane (also known as silane coupling agent KH-550).

[0023] The silane coupling agent aqueous solution has a mass fraction of 0.8%;

[0024] The inorganic filler slurry has a mass fraction of 30%.

[0025] More preferably, the inorganic filler is one of diatomaceous earth, kaolin, and bentonite.

[0026] Beneficial Effects: The inorganic fillers selected in this invention, such as diatomaceous earth, are safe, harmless, inexpensive, porous with high porosity, large specific surface area, and high adsorption capacity. After modification with a silane coupling agent, the hydroxyl groups on its surface undergo a cross-linking reaction with the silane coupling agent, enhancing its compatibility with the paper substrate. Modified kaolin possesses ion exchange capacity, adsorption capacity, a large internal surface area, and surface energy. The reduced number of hydroxyl groups in the modified kaolin after modification indicates the formation of hydrogen bonds and chemical bonding between the silane coupling agent and the modified kaolin. Modified bentonite exhibits strong hygroscopicity and swelling properties, as well as a large internal surface area. After modification with a silane coupling agent, the surface properties of the inorganic filler can be changed from hydrophilic and oleophobic to oleophilic and hydrophobic, enhancing its filling performance and compatibility with the paper substrate, thereby improving the performance of the slow-release functional material.

[0027] Its natural porosity not only allows it to bind well with fibers, maintaining paper dimensional stability and reducing paper expansion and contraction caused by humidity changes, but also provides a larger adhesion area for active substances, thus achieving a better slow-release effect. Furthermore, due to its high adsorption capacity, it can adsorb ethylene gas during the preservation process, enhancing the functionality of the preservation card. This invention modifies inorganic fillers such as diatomaceous earth, causing the silane coupling agent to undergo a certain degree of cross-linking reaction with the hydroxyl groups on the surface of diatomaceous earth, producing a coupling effect, improving compatibility with paper substrate pulp, and simultaneously improving the dispersibility of inorganic fillers.

[0028] Preferably, the papermaking technology in step (1) includes one of the vacuum filtration papermaking process and the hot pressing process;

[0029] The hot pressing process is performed at a temperature of 160°C and a pressure of 100 MPa.

[0030] Beneficial effects: By controlling the temperature and pressure parameters of the molding machine, this invention can ensure the stability of the card's mechanical properties and make the card's central slow-release functional material layer have high porosity, thus ensuring its slow-release performance.

[0031] Preferably, the ratio of the amount of carrageenan solution, chitosan solution, glycerol and active substance solution added in step (2) is 20:100:2:10;

[0032] The concentration of the carrageenan solution is 2%, the concentration of the chitosan solution is 1.5%, and the concentration of the active substance solution is 0.8%.

[0033] Beneficial effects: The combination of curcumin and chitosan in the coating solution provided by this invention greatly improves the water solubility and stability of curcumin. Furthermore, carrageenan and chitosan, due to their opposite ionic charges, easily form polyelectrolyte complexes. This composite coating has the potential to alter the permeability or mechanical properties of single-layer coatings and can delay water vapor loss. Additionally, since both curcumin and chitosan possess good antibacterial properties, they can exert a certain degree of antibacterial effect during use.

[0034] Preferably, the active substance in step (2) includes one of curcumin, tea polyphenols, anthocyanins, rosemary extract and basil extract.

[0035] Application of a slow-release antibacterial / antioxidant smart preservation card in food preservation.

[0036] This invention discloses a slow-release antibacterial / antioxidant smart preservation card, its preparation method, and its application. The invention uses bagasse as the main raw material for the slow-release functional layer of the preservation card, allowing for the reuse of bagasse resources and reducing manufacturing costs. Through the design of the device structure, the slow-release rate can be flexibly adjusted (adjusting porosity, card thickness / perimeter, PE surface perforation density, etc.), achieving long-lasting and controllable antibacterial and antioxidant functions to meet the specific preservation and shelf-life requirements of different foods. Secondly, the modified inorganic filler added in this invention improves the controllability of the slow-release of the active substances added to the preservation card, extending the card's action time. Combined with the active substance / chitosan / carrageenan composite coating, it provides a direct indication of the freshness of packaged food, enhancing the functionality of the preservation card. Furthermore, this invention addresses food oxidation and spoilage by using a slow-release structure design and the addition of active substances, supplemented by a smart freshness indicator, to enhance the preservation effect, improve the functionality of the preservation card, and extend the shelf life of food. All materials used are food-grade, ensuring food safety. Attached Figure Description

[0037] The accompanying drawings, which form part of this application, are used to provide a further understanding of this application. The illustrative embodiments and descriptions of this application are used to explain this application and do not constitute an undue limitation of this application. In the drawings:

[0038] Figure 1 The structure of the slow-release antibacterial / antioxidant smart preservation card obtained in Example 1 of this invention;

[0039] Figure 2 This describes the working principle of the sustained-release antibacterial / antioxidant smart preservation card obtained in Example 1 of the present invention.

[0040] Figure 3 This is a graph showing the weight loss rate of mangoes.

[0041] Figure 4 The image shows the results of the mango hardness test.

[0042] Figure 5 This is a graph showing the test results for the soluble solids content of mangoes. Detailed Implementation

[0043] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0044] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0045] All raw materials used in the embodiments of this invention were purchased through commercial channels;

[0046] Rosemary extract was purchased from Shanghai Maclean Biochemical Technology Co., Ltd.

[0047] Basil extract was purchased from Shaanxi Xintianyu Biotechnology Co., Ltd.

[0048] Example 1

[0049] A method for preparing a slow-release antibacterial / antioxidant smart preservation card includes the following steps:

[0050] (1) Preparation of sustained-release functional material layer

[0051] (1-1) Inorganic filler modification: Weigh 1.5g of diatomaceous earth and prepare a diatomaceous earth slurry with deionized water at a mass fraction of 30%. Heat the slurry in a water bath at 100℃ and stir at a constant speed for 15min. Then weigh 1g of silane coupling agent KH-550 (γ-aminopropyltriethoxysilane) and prepare a silane coupling agent aqueous solution with a mass fraction of 0.8%. Stir at a constant speed for 20min at room temperature. Slowly and evenly add the obtained silane coupling agent aqueous solution to the diatomaceous earth slurry and continue stirring for 1h. Then dry the slurry in a 90℃ oven for 8h and pass it through a 200-mesh standard sieve to obtain modified diatomaceous earth.

[0052] (1-2) Weigh 0.04g of curcumin and dissolve it in 10ml of anhydrous ethanol. Stir for 2h at 25℃ in the dark to prepare two curcumin solutions.

[0053] Mix 20g of bagasse oven-dried pulp with 500ml of deionized water to prepare a 4% pulp mix. Then add 1.5g of modified diatomaceous earth and 10ml of curcumin solution. After stirring the mixed pulp evenly, paper substrate is obtained by vacuum filtration papermaking process.

[0054] (1-3) Remove the paper substrate, let it dry, and cut it into cards of the same size and specifications to obtain a slow-release functional material layer (about 0.5mm).

[0055] (2) Preparation of freshness indicator layer and antioxidant smart preservation card:

[0056] (2-1) Prepare a 2% carrageenan solution at 80℃ and stir for 30 min. Mix chitosan with water at room temperature and acidify with 1.0% acetic acid. Stir until completely dissolved to prepare a 1.5% chitosan aqueous solution. Take 20 ml of carrageenan solution and add it to 100 ml of chitosan solution, 2 ml of glycerol and 10 ml of curcumin solution obtained in step (1-2). Stir the mixture thoroughly for 1 h to obtain the coating solution.

[0057] (2-2) The air bubbles in the obtained coating liquid were removed by ultrasonic oscillation. Then, the coating liquid was evenly coated on the obtained slow-release functional material layer paper with the same size and a thickness of 0.5 mm by coating method. After drying, it was placed in a constant temperature and humidity chamber for equilibration for 48 hours. The upper and lower sides were laminated with perforated PE film and pressed to obtain a slow-release antibacterial / antioxidant smart preservation card.

[0058] The resulting preservation card structure is as follows Figure 1 As shown, its working principle is as follows Figure 2 As shown.

[0059] The working principle is as follows: Figure 1 and 2 As shown, in the composite preservation card device, the active substances added in different structures will be released from different locations. The active substances in the slow-release functional material layer will be slowly released from all sides of the card, while the active substances contained in the freshness indicator layer, while exhibiting a color-developing function, can also be released through the PE film with a certain number of pores on its surface.

[0060] Example 2

[0061] A method for preparing a slow-release antibacterial / antioxidant smart preservation card differs from Example 1 in that, in step (1-2), the mixed slurry is stirred evenly and then subjected to a hot pressing molding process (160℃, 100mpa) to obtain a paper substrate.

[0062] Paper made directly from bagasse pulp in the vacuum filtration papermaking process is more brittle than pulp molded products. Therefore, the hot pressing process is chosen to form the substrate of the food preservation card, which has relatively high mechanical strength and a relatively simple manufacturing process.

[0063] Example 3

[0064] A method for preparing a slow-release antibacterial / antioxidant smart preservation card, differing from Example 1 in that the modified inorganic filler in step (1-1) is modified kaolin. The specific preparation method includes the following steps:

[0065] Inorganic filler modification: Weigh 1.5g of kaolin and prepare a 30% (w / w) kaolin slurry using deionized water. Heat the slurry in a water bath at 100℃ and stir at a constant speed for 15min. Then weigh 1g of silane coupling agent KH-550 (γ-aminopropyltriethoxysilane) and prepare a 0.8% (w / w) silane coupling agent aqueous solution. Stir at a constant speed at room temperature for 20min. Slowly and evenly add the obtained silane coupling agent aqueous solution to the kaolin slurry and continue stirring for 1h. Then dry the slurry in a 90℃ oven for 8h and pass it through a 200-mesh standard sieve to obtain modified kaolin.

[0066] Example 4

[0067] A method for preparing a slow-release antibacterial / antioxidant smart preservation card, differing from Example 1 in that the modified inorganic filler selected in step (1-1) is modified bentonite, and the specific preparation method includes the following steps:

[0068] Inorganic filler modification: Weigh 1.5g of bentonite and prepare a 30% bentonite slurry using deionized water. Heat the slurry in a water bath at 100℃ and stir at a constant speed for 15min. Then weigh 1g of silane coupling agent KH-550 (γ-aminopropyltriethoxysilane) and prepare a 0.8% silane coupling agent aqueous solution. Stir at a constant speed at room temperature for 20min. Slowly and evenly add the obtained silane coupling agent aqueous solution to the bentonite slurry and continue stirring for 1h. Then dry the slurry in a 90℃ oven for 8h and pass it through a 200-mesh standard sieve to obtain modified bentonite.

[0069] Example 5

[0070] A method for preparing a slow-release antibacterial / antioxidant smart preservation card includes the following steps:

[0071] (1) Preparation of sustained-release functional material layer

[0072] (1-1) Inorganic filler modification: Weigh 1.5g of diatomaceous earth and prepare a diatomaceous earth slurry with deionized water at a mass fraction of 30%. Heat the slurry in a water bath at 100℃ and stir at a constant speed for 15min. Then weigh 1g of silane coupling agent KH-550 (γ-aminopropyltriethoxysilane) and prepare a silane coupling agent aqueous solution with a mass fraction of 0.8%. Stir at a constant speed for 20min at room temperature. Slowly and evenly add the obtained silane coupling agent aqueous solution to the diatomaceous earth slurry and continue stirring for 1h. Then dry the slurry in a 90℃ oven for 8h and pass it through a 200-mesh standard sieve to obtain modified diatomaceous earth.

[0073] (1-2) Mix 20g of bagasse dry pulp with 500ml of deionized water to prepare 4% pulp, then add 1.5g of modified diatomaceous earth and 0.05g of tea polyphenols. After stirring the mixed pulp evenly, paper substrate is obtained by vacuum filtration papermaking process.

[0074] (1-3) Remove the paper substrate, let it dry, and cut it into cards of the same size and specifications to obtain a slow-release functional material layer (thickness of about 0.5mm).

[0075] (2) Preparation of freshness indicator layer and antioxidant smart preservation card:

[0076] (2-1) Weigh 0.04g of curcumin and dissolve it in 10ml of anhydrous ethanol. Stir for 2h at 25℃ in the dark to prepare curcumin solution. Prepare 100ml of 2% carrageenan solution at 80℃ and stir for 30min. Add 2ml of glycerol and 10ml of the obtained curcumin solution and stir the mixture thoroughly for 1h to obtain the coating solution.

[0077] (2-2) The air bubbles in the obtained coating liquid were removed by ultrasonic oscillation. The coating liquid was then evenly coated onto the obtained slow-release functional material layer paper of the same size by coating method. After drying, it was placed in a constant temperature and humidity chamber for equilibration for 48 hours. The upper and lower sides were laminated with perforated PE film and pressed to obtain a slow-release antibacterial / antioxidant smart preservation card.

[0078] Example 6

[0079] A method for preparing a slow-release antibacterial / antioxidant smart preservation card includes the following steps:

[0080] (1) Preparation of sustained-release functional material layer

[0081] (1-1) Inorganic filler modification: Weigh 1.5g of diatomaceous earth and prepare a diatomaceous earth slurry with deionized water at a mass fraction of 30%. Heat the slurry in a water bath at 100℃ and stir at a constant speed for 15min. Then weigh 1g of silane coupling agent KH-550 (γ-aminopropyltriethoxysilane) and prepare a silane coupling agent aqueous solution with a mass fraction of 0.8%. Stir at a constant speed for 20min at room temperature. Slowly and evenly add the obtained silane coupling agent aqueous solution to the diatomaceous earth slurry and continue stirring for 1h. Then dry the slurry in a 90℃ oven for 8h and pass it through a 200-mesh standard sieve to obtain modified diatomaceous earth.

[0082] (1-2) Weigh 0.04g of rosemary extract and dissolve it in 10ml of deionized water to prepare a rosemary extract solution; mix 20g of bagasse dry pulp with 500ml of deionized water to prepare a 4% pulp mix, then add 1.5g of modified diatomaceous earth and 10ml of rosemary extract solution, and then stir the mixed pulp evenly and obtain paper substrate by vacuum filtration papermaking process.

[0083] (1-3) Take out the paper substrate, let it dry, and cut it into cards of the same size and specifications to obtain the slow-release functional material layer.

[0084] (2) Preparation of freshness indicator layer and antioxidant smart preservation card:

[0085] (2-1) Weigh 0.05g of anthocyanin and dissolve it in 10ml of deionized water to prepare anthocyanin solution; prepare 100ml of carrageenan solution with a mass concentration of 2% at 80℃ and stir with a stirrer for 30min. Then add 2ml of glycerol and 10ml of the obtained anthocyanin solution and stir the mixture thoroughly for 1h to obtain the coating solution.

[0086] (2-2) The air bubbles in the obtained coating liquid were removed by ultrasonic oscillation. The coating liquid was then evenly coated onto the obtained slow-release functional material layer paper of the same size by coating method. After drying, it was placed in a constant temperature and humidity chamber for equilibration for 48 hours. The upper and lower sides were laminated with perforated PE film and pressed to obtain a slow-release antibacterial / antioxidant smart preservation card.

[0087] Example 7

[0088] A method for preparing a slow-release antibacterial / antioxidant smart preservation card includes the following steps:

[0089] (1) Preparation of sustained-release functional material layer

[0090] (1-1) Inorganic filler modification: Weigh 1.5g of diatomaceous earth and prepare a diatomaceous earth slurry with deionized water at a mass fraction of 30%. Heat the slurry in a water bath at 100℃ and stir at a constant speed for 15min. Then weigh 1g of silane coupling agent KH-550 (γ-aminopropyltriethoxysilane) and prepare a silane coupling agent aqueous solution with a mass fraction of 0.8%. Stir at a constant speed for 20min at room temperature. Slowly and evenly add the obtained silane coupling agent aqueous solution to the diatomaceous earth slurry and continue stirring for 1h. Then dry the slurry in a 90℃ oven for 8h and pass it through a 200-mesh standard sieve to obtain modified diatomaceous earth.

[0091] (1-2) Weigh 0.04g of basil extract and dissolve it in 10ml of deionized water to prepare basil extract solution; mix 20g of bagasse dry pulp with 500ml of deionized water to prepare 4% pulp, then add 1.5g of modified diatomaceous earth and 10ml of basil extract solution, and then stir the mixed pulp evenly and obtain paper substrate by vacuum filtration papermaking process.

[0092] (1-3) Take out the paper substrate, let it dry, and cut it into cards of the same size and specifications to obtain the slow-release functional material layer.

[0093] (2) Preparation of freshness indicator layer and antioxidant smart preservation card:

[0094] (2-1) Weigh 0.05g of anthocyanin and dissolve it in 10ml of deionized water to prepare anthocyanin solution; prepare 100ml of carrageenan solution with a mass concentration of 2% at 80℃ and stir with a stirrer for 30min. Then add 2ml of glycerol and 10ml of the obtained anthocyanin solution and stir the mixture thoroughly for 1h to obtain the coating solution.

[0095] (2-2) The air bubbles in the obtained coating liquid were removed by ultrasonic oscillation. The coating liquid was then evenly coated onto the obtained slow-release functional material layer paper of the same size by coating method. After drying, it was placed in a constant temperature and humidity chamber for equilibration for 48 hours. The upper and lower sides were laminated with perforated PE film and pressed to obtain a slow-release antibacterial / antioxidant smart preservation card.

[0096] Comparative Example 1

[0097] A method for preparing a food preservation card includes the following steps:

[0098] (1) Preparation of sustained-release functional material layer

[0099] (1-1) Weigh 0.4g of curcumin and dissolve it in 10ml of anhydrous ethanol to prepare a curcumin solution; mix 20g of bagasse dry pulp with 500ml of deionized water to prepare a 4% pulp mix, then add 10ml of curcumin solution, and then stir the mixed pulp evenly and obtain paper substrate by vacuum filtration papermaking process.

[0100] (1-2) Take out the paper substrate, let it dry, and cut it into cards of the same size and specifications to obtain the slow-release functional material layer.

[0101] (2) Preparation of preservation cards:

[0102] (2-1) Prepare a 2% carrageenan solution at 80℃ and stir for 30 min. Mix chitosan with water at room temperature and acidify with 1.0% acetic acid. Stir until completely dissolved to prepare a 1.5% chitosan aqueous solution. Take 20 ml of carrageenan solution and add it to 100 ml of chitosan solution, 2 ml of glycerol and 10 ml of curcumin solution obtained in step (1-1). Stir the mixture thoroughly for 1 h to obtain the coating solution.

[0103] (2-2) The air bubbles in the obtained coating liquid were removed by ultrasonic oscillation. The coating liquid was then evenly coated onto the obtained slow-release functional material layer paper of the same size by coating method. After drying, it was placed in a constant temperature and humidity chamber for equilibration for 48 hours. The upper and lower sides were laminated with perforated PE film and pressed to obtain a slow-release antibacterial / antioxidant smart preservation card.

[0104] The difference between Comparative Example 1 and Example 1 is that no modified inorganic filler was added as a slow-release agent for the preservation card, in order to demonstrate that the modified inorganic filler can significantly improve the adsorption and slow-release capacity of the preservation card for active substances.

[0105] Comparative Example 2

[0106] A method for preparing food preservation cards, the specific steps of which are as follows:

[0107] (1) Preparation of sustained-release functional material layer

[0108] (1-1) Inorganic filler modification: Weigh 1.5g of diatomaceous earth and prepare a diatomaceous earth slurry with deionized water at a mass fraction of 30%. Heat the slurry in a water bath at 100℃ and stir at a constant speed for 15min. Then weigh 1g of silane coupling agent KH-550 (γ-aminopropyltriethoxysilane) and prepare a silane coupling agent aqueous solution with a mass fraction of 0.8%. Stir at a constant speed for 20min at room temperature. Slowly and evenly add the obtained silane coupling agent aqueous solution to the diatomaceous earth slurry and continue stirring for 1h. Then dry the slurry in a 90℃ oven for 8h and pass it through a 200-mesh standard sieve to obtain modified diatomaceous earth.

[0109] (1-2) Weigh 0.16g of curcumin and dissolve it in 10ml of anhydrous ethanol to prepare a curcumin solution; mix 20g of bagasse dry pulp with 500ml of deionized water to prepare a 4% pulp slurry, then add 1.5g of modified diatomaceous earth and 10ml of curcumin solution, and then stir the mixed slurry evenly and obtain paper substrate by hot pressing molding process (160℃, 100mpa).

[0110] (1-3) Take out the paper substrate, let it dry, and cut it into cards of the same size and specifications to obtain the slow-release functional material layer.

[0111] (2) Preparation of preservation cards:

[0112] (2-1) Prepare a 2% carrageenan solution at 80℃ and stir for 30 min. Mix chitosan with water at room temperature and acidify with 1.0% acetic acid. Stir until completely dissolved to prepare a 1.5% chitosan aqueous solution. Take 20 ml of carrageenan solution and add it to 100 ml of chitosan solution, 2 ml of glycerol and 10 ml of curcumin solution obtained in step (1-2). Stir the mixture thoroughly for 1 h to obtain the coating solution.

[0113] (2-2) The air bubbles in the obtained coating liquid were removed by ultrasonic oscillation. The coating liquid was then evenly coated onto the obtained slow-release functional material layer paper of the same size by coating method. After drying, it was placed in a constant temperature and humidity chamber for equilibration for 48 hours. The upper and lower sides were laminated with perforated PE film and pressed to obtain a slow-release antibacterial / antioxidant smart preservation card.

[0114] The difference between Comparative Example 2 and Example 2 is that the amount of active substance added is different, thus proving that the antioxidant and antibacterial ability of the preservation card is related to the amount of active substance added. Within a certain range, the more active substance added, the better the antioxidant and antibacterial effect.

[0115] Technical effects:

[0116] The sustained-release antibacterial / antioxidant smart preservation cards prepared in Examples 1-2 and 5-7 were compared with the preservation cards obtained in Comparative Examples 1 and 2, as well as commercially available alcohol preservation cards (purchased from Shanghai Yuejie Desiccant Products Co., Ltd., size 15*20, 5g / piece, cut to the required size by the user) in terms of sustained-release antioxidant capacity, freshness indication, etc.

[0117] Determination of sustained-release antioxidant capacity

[0118] A certain quantity of fresh mangoes, free from mechanical damage, pests, and diseases, and of roughly the same size and color, were purchased and packaged in equal quantities into self-sealing transparent PE bags. These bags were designated as Examples 1-2, 5-7, Comparative Examples 1-2, a commercially available alcohol-based preservation card group, and a cardless group. The five groups of samples were placed under identical environmental conditions, and the weight loss rate, firmness, and soluble solids content of the mangoes were measured over periods of 0 days, 3 days, 6 days, 9 days, and 12 days to evaluate the slow-release antioxidant preservation effect.

[0119] (1) The weight loss rate of mangoes is calculated as shown in Formula 1:

[0120] Weight loss rate (%) = [(weight before treatment - weight after treatment) / weight before treatment] × 100% (1)

[0121] The results of the weight loss rate test are as follows Figure 3 As shown, by Figure 3 It was observed that all mangoes showed no significant weight loss during the first three days of storage. From the fourth day onwards, noticeable black spots appeared on the mangoes, and the weight loss increased significantly with continued transpiration. Comparative Example 1, the group without the slow-release agent, showed the least weight loss before day 6, indicating the best storage effect. This was due to the large release of curcumin from the preservation card in the early stages. However, the storage effect of the mangoes without the slow-release agent deteriorated after day 9, with noticeable spoilage on the mango skin, and large areas of black spots appearing on day 12. These phenomena can be attributed to poor slow-release effect. The mangoes in the group using the preservation card obtained in Example 2 of this invention showed the best appearance and the least weight loss compared to other groups on day 12, indicating a better storage effect. This effect can be attributed to the optimal combination of the preservation card's structure and the active substances' action in maintaining mango quality.

[0122] (2) Effect on mango firmness

[0123] Five mangoes were selected from each treatment group. The skin of each mango was first removed from both the front and back equatorial regions. Then, two locations were selected for hardness testing using a GY-3 hardness tester. The average of ten measurements was taken as one test. The mango hardness was calculated using Equation 2:

[0124] P = N / S (2)

[0125] Where: P - the firmness value of the fruit being tested (Kg / cm) 2 or Kgf);

[0126] N - The weight of the force-measuring spring pressing on the fruit, kg;

[0127] S - The area of ​​the fruit subjected to force, in square meters or square centimeters;

[0128] Hardness results as follows Figure 4 As shown, the firmness of fruit gradually decreases with increasing ripeness during storage; that is, the riper the fruit, the softer it becomes, eventually leading to spoilage. Therefore, the firmness of fruit is one of the indicators of its freshness. Figure 4 It can be seen that the firmness of mangoes gradually decreased with prolonged storage time. After 6 days of storage, the mangoes in the treatment group of Example 1 and Comparative Example 2 were significantly firmer than the mangoes in the control group without preservatives. Before the 6th day, the mangoes in Comparative Example 1 were firmer than the other groups, but because their preservatives did not contain slow-release agents, the active substances were released more quickly, resulting in a significant decrease in mango firmness after the 6th day.

[0129] (3) Effect on the soluble solids content of mango

[0130] Soluble solids content is one of the important indicators for judging the freshness and storage resistance of fruit. For each mango whose firmness was measured, the flesh from both sides near the equator was taken, cut into small pieces, mashed, and filtered through two layers of gauze to extract the juice. Soluble solids content was determined according to the National Food Safety Standard "Determination of Soluble Solids Content in Fruits and Vegetables - Refractometer Method" NY / T2637-2014. Each fruit was measured twice, with the average of 10 measurements serving as one replicate. Each treatment was repeated three times.

[0131] The results are as follows Figure 5 As shown, the soluble solids content of mangoes in the control group without the card consistently increased, reaching its highest value. Under the same storage time, the soluble solids content in Example 2 of this invention was lower than that in Comparative Examples 1-2, as well as the commercially available alcohol-based preservation card and the cardless group. This indicates that the preservation card of this invention can significantly inhibit the rate of increase in soluble solids in mangoes, thus extending the shelf life of the mangoes.

[0132] The above are merely preferred embodiments of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A method for preparing a slow-release antibacterial and antioxidant smart preservation card, characterized in that, Includes the following steps: (1) Using bagasse fiber as the base material, modified inorganic fillers and active substances are added, and a slow-release functional material layer is prepared by papermaking technology. The modified inorganic filler includes one of modified diatomaceous earth, modified kaolin, and modified bentonite; The active substances include one of curcumin, tea polyphenols, anthocyanins, rosemary extract, and basil extract; The mass ratio of bagasse fiber, modified inorganic filler, and active material is (20-25):(1-1.5):(0.04-0.4). The preparation method of the modified inorganic filler includes the following steps: The aqueous solution of silane coupling agent was slowly and evenly added to the inorganic filler slurry and stirred. After stirring, the slurry was dried and then sieved to obtain the modified inorganic filler. (2) The active substance solution, chitosan solution, carrageenan solution and glycerin are mixed to prepare a coating solution, which is then uniformly coated on the front and back sides of the sustained-release functional material layer to obtain a freshness indicator layer; The active substances include one of curcumin, tea polyphenols, anthocyanins, rosemary extract, and basil extract; (3) Preparation of barrier layer: A PE film with uniform perforation is laminated on the surface of freshness indicator layer as a barrier layer, and then pressed to obtain a freshness card.

2. The method for preparing a slow-release antibacterial and antioxidant smart preservation card according to claim 1, characterized in that, The bagasse fiber mentioned in step (1) is bagasse oven-dried pulp, which is obtained by directly cooking fresh bagasse into pulp, followed by pulping, papermaking, and filtration.

3. The method for preparing a slow-release antibacterial and antioxidant smart preservation card according to claim 1, characterized in that, The stirring time in step (1) is 1 hour; The drying process involves placing the item in a 90℃ oven for 8 hours. The sieving process involves passing through a 200-mesh standard sieve.

4. The method for preparing a slow-release antibacterial and antioxidant smart preservation card according to claim 1, characterized in that, The silane coupling agent mentioned in step (1) is γ-aminopropyltriethoxysilane; The silane coupling agent aqueous solution has a mass fraction of 0.8%; The inorganic filler slurry has a mass fraction of 30%.

5. The method for preparing a slow-release antibacterial and antioxidant smart preservation card according to claim 1, characterized in that, The papermaking technology mentioned in step (1) includes one of the following: vacuum filtration papermaking process and hot pressing forming process; The hot pressing process is performed at a temperature of 160°C and a pressure of 100 MPa.

6. The method for preparing a slow-release antibacterial and antioxidant smart preservation card according to claim 1, characterized in that, The ratio of the amount of carrageenan solution, chitosan solution, glycerol and active substance solution added in step (2) is 20:100:2:10; The concentration of the carrageenan solution is 2%; The concentration of the chitosan solution is 1.5%; The concentration of the active substance solution is 0.8%.

7. A slow-release antibacterial and antioxidant smart preservation card prepared by the preparation method according to any one of claims 1-6.

8. The application of the slow-release antibacterial and antioxidant smart preservation card as described in claim 7 in food preservation.

Images