Environment self-adaptive humidity control gel, preparation method and application in food storage

Abstract

The invention belongs to the technical field of new materials and food storage, and discloses environment-adaptive humidity control gel, a preparation method and application in food storage, and the method comprises the following steps: mixing a polymer monomer, an inorganic salt, a cross-linking agent, an initiator and water, and fully stirring until the components are uniformly dissolved; mixing the obtained mixed solution with guar gum, and fully stirring until the mixture is uniformly mixed; and curing to obtain the environment self-adaptive humidity control gel. The material disclosed by the invention has intelligent humidity control capability, can resist the influence caused by temperature fluctuation, and can release water vapor under low humidity and absorb water vapor under high humidity. And the humidity can be accurately controlled within 32%, 77%, 85% and any desired humidity range. The intelligent gradient humidity control is carried out, so that the intelligent gradient humidity control system is suitable for suitable humidity required by storage of different foods, condensation and decay caused by high humidity can be avoided, and water loss caused by low humidity can also be avoided.

Description

Technical Field

[0001] This invention belongs to the fields of new materials and food storage technology, and in particular to an environmentally adaptive humidity-controlled gel, its preparation method, and its application in food storage. Background Technology

[0002] Food is a type of food that is highly sensitive to changes in humidity. This is especially true for moisture-sensitive foods, where moisture absorption and control are crucial, as humidity directly affects food quality, taste, and shelf life. Excessive moisture absorption can lead to spoilage, microbial growth, deterioration of taste, and even mold or rot. Conversely, improper humidity control can cause food to lose its crispness, flavor, or texture. Effective humidity control measures can extend shelf life, maintain optimal taste, ensure flavor stability, and prevent packaging failure and spoilage. Therefore, precise humidity control is essential for ensuring the quality of moisture-sensitive foods. Traditional packaging materials and humidity control technologies struggle to effectively regulate humidity during long-term storage and transportation, limiting food preservation. Furthermore, new intelligent humidity control technologies are not yet widely adopted, and many challenges remain to be addressed. The existing technologies present the following technical problems:

[0003] Question 1: Most current humidity control materials for fruit and vegetable preservation can only absorb moisture, but cannot intelligently control humidity, which ultimately leads to dehydration, wilting, and reduced quality of fruits and vegetables.

[0004] Question 2: Although some materials such as MOF have been developed for humidity control, these materials have a wide humidity control range, mostly within the range of 20% to 30%, which leads to large humidity fluctuations and cannot accurately maintain the humidity required by fruits, vegetables and food.

[0005] Question 3: Although supersaturated salts can precisely control humidity, after absorbing a certain amount of water, granular hygroscopic salts will deliquesce and eventually become salt solutions. Salt solutions do not have self-supporting capabilities and are prone to flow, causing some inconvenience to the use, operation and transportation of materials.

[0006] The search revealed the following patent publications related to this invention's patent application:

[0007] 1. A hygroscopic packaging material and its preparation method and application (CN117487225A) discloses a method for preparing a hygroscopic packaging material. This packaging material has excellent hygroscopicity, good interlayer adhesion and is not easy to fall off, and good antibacterial properties. However, this packaging material only has hygroscopic properties and does not have moisture control properties, and cannot precisely adjust the range to meet the needs of different foods.

[0008] 2. A moisture-controlling, rapid oxygen-reducing, and antibacterial modified atmosphere packaging film for fruits and vegetables, its preparation method, and its application (CN115819819A) discloses a preparation method and application of a moisture-controlling, oxygen-reducing, and antibacterial modified atmosphere packaging film for fruits and vegetables. The polytetrafluoroethylene microporous membrane of this composite film can control the humidity of the storage environment and regulate the transpiration of fruits and vegetables. However, this film increases the water content and moisture permeability of the film through the pore size difference between micropores, water vapor, and liquid water. If the relative humidity of the environment is low, it cannot effectively prevent excessive water loss from fruits and vegetables, easily leading to wrinkling, softening, and wilting.

[0009] 3. A smart humidity-controlled film, its preparation method, and its application (CN111013402B) discloses a smart humidity-controlled film, its preparation method, and its application. The provided smart humidity-controlled film can retain moisture under low humidity conditions, has strong moisture removal capabilities under high humidity conditions, and also has gas barrier properties. However, this film has low moisture permeability at a relative humidity of 50%, but increases moisture permeability at a relative humidity of 90%. Its humidity control capability has a wide range, spanning approximately 40%, and cannot precisely control the humidity required for food storage.

[0010] 4. A humidity-regulating functional material and its preparation method (CN112239521A) discloses an environmental humidity-regulating functional material and its preparation method. This humidity-regulating material is obtained by adding sodium carboxymethyl cellulose, acrylic acid, acrylamide, ammonium persulfate, and N,N-methylenebisacrylamide to an inorganic salt solution and stirring the mixture at 50–60°C for 2–5 hours. However, this process involves two steps, is relatively complex, and has a long reaction time. Furthermore, this humidity-regulating material can only control humidity to around 55%, and the influence of temperature on the humidity control capability of the material is not discussed. Therefore, it cannot accurately adapt to different food requirements and storage / transportation environments to achieve a target humidity range.

[0011] 5. A functional material for automatically regulating ambient humidity and its preparation (CN112175145B) discloses a functional material for automatically regulating ambient humidity and its preparation. It involves compounding inorganic mineral materials with organic polymer-based humidity-regulating materials and dispersing an appropriate amount of inorganic salts in the system to obtain a functional material with high moisture capacity and fast humidity regulation rate. However, the salts used in this material are a mixture of two inorganic salts, requiring more careful management of the salt ratio and interactions, increasing operational complexity. Furthermore, this humidity-regulating material can only stabilize the humidity at around 45%, and it does not discuss the influence of temperature on the humidity control capability of the humidity-regulating material, thus failing to accurately adapt to the target humidity range according to different food requirements and storage and transportation environments.

[0012] By comparison, the present invention patent application is fundamentally different from the aforementioned patent publications. Summary of the Invention

[0013] The purpose of this invention is to overcome the shortcomings of the prior art and provide an environmentally adaptive humidity-controlled gel, its preparation method, and its application in food storage.

[0014] The technical solution adopted by this invention to solve its technical problem is:

[0015] A method for preparing an environmentally adaptive humidity-controlled gel includes the following steps:

[0016] (1) Mix the polymer monomers, inorganic salts, α-ketoglutaric acid, N,N'-methylenebisacrylamide and water, and stir thoroughly until dissolved and homogeneous;

[0017] (2) Mix the mixture obtained in step (1) with guar gum and stir thoroughly until the mixture is homogeneous;

[0018] (3) The mixture obtained in step (2) is cured in a 365nm ultraviolet box to obtain an environmentally adaptive humidity-controlled gel.

[0019] Furthermore, the inorganic salt is one of lithium chloride, magnesium chloride, calcium chloride, sodium chloride, and potassium chloride, and the polymer monomer is acrylamide.

[0020] Furthermore, the specific steps are as follows:

[0021] (1) Add inorganic salts to the acrylamide monomer solution at room temperature until it becomes supersaturated;

[0022] (2) Add α-ketoglutaric acid and N,N'-methylenebisacrylamide to step (1) and stir thoroughly until the mixture is homogeneous;

[0023] (3) Add guar gum to step (2) and stir thoroughly until the mixture is homogeneous;

[0024] (4) Place the mixture obtained in step (3) in a 365nm UV box for 100-120 minutes to obtain an environmentally adaptive humidity-controlled gel.

[0025] Further, the mass ratios of the polymer monomer, α-ketoglutaric acid, and N,N'-methylenebisacrylamide in water are 3%–30% (wt / v), 0.005%–0.05% (wt / v), and 0.004%–0.03% (wt / v), respectively.

[0026] Furthermore, the inorganic salt has a mass ratio in water of 10% to 370% (wt / v), and the resulting environmentally adaptive gel can control humidity within any value between 10% and 95%.

[0027] Furthermore, the concentration of the acrylamide monomer solution in step (1) is 0.5–4 M;

[0028] Alternatively, in step (2), the concentrations of α-ketoglutarate and N,N'-methylenebisacrylamide are 0.0005–0.004 M and 0.00025–0.002 M, respectively.

[0029] Furthermore, in step (2), α-ketoglutaric acid is used as an initiator and N,N'-methylenebisacrylamide is used as a crosslinking agent.

[0030] Furthermore, the guar gum has a mass fraction of 0.1% to 0.5% (wt / v) in water.

[0031] The environmentally adaptive humidity-controlled gel was prepared by the method described above.

[0032] Applications of environmentally adaptive moisture-controlling gels as described above in food preservation and / or transportation.

[0033] The advantages and positive effects of this invention are as follows:

[0034] 1. This invention proposes the synthesis of an adaptive humidity-regulating gel using a supersaturated salt solution and polyacrylamide gel. A supersaturated salt solution contains more solute than its solubility allows for strong interactions between water molecules and solute molecules, causing water molecules to be bound around the solute and thus lowering the chemical potential of water. When ambient humidity is high, the chemical potential of water vapor in the air is high, while the chemical potential of water in the supersaturated salt solution is low. To achieve chemical potential equilibrium, water vapor is adsorbed from the air into the solution until a stable humidity equilibrium is reached. When ambient humidity is low, the chemical potential of water vapor in the air is low, while the chemical potential of water in the supersaturated salt solution is high. Therefore, water evaporates from the solution into the air until the chemical potential of the solution is balanced with that of the surrounding environment. This process gives the environmentally adaptive humidity-regulating gel excellent humidity control capabilities, enabling it to regulate the humidity of the surrounding air under different ambient humidity levels, achieving a relatively stable humidity balance. This avoids excessively dry or humid environments, reduces the risk of microbial growth, and extends the shelf life of food.

[0035] 2. The gel prepared by this invention can sensitively sense changes in environmental humidity and dynamically adjust the absorption and release of moisture, achieving precise adaptation to the target humidity range and effectively preventing the impact of humidity fluctuations on food.

[0036] 3. This invention utilizes different types of inorganic salts to prepare environmentally adaptive gels that can work stably under various humidity conditions. It is suitable for various types of food. Under low humidity, it can release moisture to prevent food from drying out and hardening, such as fresh agricultural products. Under high humidity, it can absorb excess moisture to prevent food from getting damp, moldy, or spoiled, such as grains and dried fruits, thus extending the shelf life and maintaining food quality.

[0037] 4. The environmentally adaptive humidity-controlled gel prepared by this invention can resist the effects of temperature changes. The added guar gum is a natural water-soluble high-molecular-weight polysaccharide with a large number of hydroxyl groups on its molecular chain. These polar groups can form strong bonds with water molecules through hydrogen bonding, thereby helping to maintain the hydration state of the supersaturated environmentally adaptive gel, reducing moisture migration caused by temperature changes, and maintaining humidity stability. On the other hand, guar gum can slow down the precipitation rate of supersaturated salts, thereby reducing the impact of temperature changes on gel performance, allowing it to work stably under temperature fluctuations, increasing temperature adaptability, and making it an ideal humidity control material for food storage and transportation at different temperatures.

[0038] 5. The adaptive humidity regulating gel prepared by this invention is easy to use and operate, avoiding the risk of spillage or contamination that may be caused by liquid humidity regulating materials. At the same time, it has the characteristics of long-lasting effect and reusability, making it suitable for widespread application in food storage and transportation, extending the shelf life of food and improving its quality.

[0039] 7. The intelligent humidity control material of this invention is composed of supersaturated lithium chloride, magnesium chloride, sodium chloride, potassium chloride solution, guar gum, and polyacrylamide gel. This material possesses intelligent humidity control capabilities and can resist the effects of temperature fluctuations. It releases water vapor in low humidity and absorbs water vapor in high humidity. It can precisely control humidity at approximately 32%, 47%, 77%, and 85%. This invention's intelligent gradient humidity control is suitable for the appropriate humidity required for storing different foods, avoiding both condensation and spoilage caused by high humidity and water loss caused by low humidity.

[0040] 8. The specific innovative points of this invention are as follows:

[0041] Innovation Point 1: Adaptive Adjustment: This invention has adaptability and responsiveness, and can automatically adjust its own moisture according to changes in ambient humidity, and can resist temperature fluctuations to ensure stable humidity.

[0042] Innovation Point 2: Precise Control: This invention can precisely control the relative humidity of the environment within a certain range, avoiding changes in food quality caused by large fluctuations in humidity.

[0043] Innovation Point 3: Convenience: This invention is easy to use, easy to control the quantity, stable for long-term use, and simpler to manage storage and transportation. It can be flexibly applied to a variety of occasions, especially in food packaging and storage, and is not prone to leakage.

[0044] Innovation Point 4: Wide range of applications: This invention can effectively regulate humidity by simply adjusting the type of salt, and precisely control the required humidity level. It is suitable for a variety of foods, such as flour products and fruits and vegetables. Attached Figure Description

[0045] Figure 1 The diagram shows the adsorption and desorption of the environmentally adaptive humidity-controlling gel in this invention at room temperature (25°C). (a) shows the hygroscopic behavior of the potassium chloride environmentally adaptive gel under high humidity; (b) shows the desorption behavior of the potassium chloride environmentally adaptive gel under low humidity; (c) shows the hygroscopic behavior of the lithium chloride environmentally adaptive gel under high humidity; and (d) shows the desorption behavior of the lithium chloride environmentally adaptive gel under low humidity. The humidity-controlling gel can control the relative humidity of the environment at approximately 85% and 32%, indicating that it has precise humidity control performance and can work stably under various humidity conditions, making it suitable for various food types.

[0046] Figure 2 Figure (a) shows the pore size distribution of the environmentally adaptive humidity-controlled gel in this invention; and Figure (b) shows the pore size distribution of the potassium chloride environmentally adaptive gel.

[0047] Figure 3 Figure (a) shows the water vapor adsorption isotherm of the environmentally adaptive humidity-controlled gel in this invention; and Figure (b) shows the water vapor adsorption isotherm of the potassium chloride environmentally adaptive gel.

[0048] Figure 4 The graphs show the adsorption kinetics of the environmentally adaptive humidity-controlled gel in this invention; where (a) is the adsorption kinetics curve of the potassium chloride environmentally adaptive gel; and (b) is the adsorption kinetics curve of the lithium chloride environmentally adaptive gel.

[0049] Figure 5 The diagram shows the adsorption and desorption of the environmentally adaptive humidity-controlled gel in this invention at 37°C; where (a) is the hygroscopic behavior of the potassium chloride environmentally adaptive gel under high humidity; (b) is the desorption behavior of the potassium chloride environmentally adaptive gel under low humidity; (c) is the hygroscopic behavior of the lithium chloride environmentally adaptive gel under high humidity; and (d) is the desorption behavior of the lithium chloride environmentally adaptive gel under low humidity.

[0050] Figure 6 The diagram shows the adsorption and desorption of the environmentally adaptive humidity-controlled gel in this invention at 4°C; (a) shows the desorption and adsorption behavior of the potassium chloride environmentally adaptive gel under different humidity levels; (b) shows the desorption and adsorption behavior of the lithium chloride environmentally adaptive gel under different humidity levels.

[0051] Figure 7 The image shows the effect of potassium chloride environmental adaptive humidity control gel on strawberry preservation in this invention; it demonstrates that the potassium chloride humidity control gel can not only control humidity, but also reduce the formation of water droplets, reduce rotting, and extend shelf life.

[0052] Figure 8This is a graph showing the effect of potassium chloride environment adaptive humidity control gel on the rot rate of strawberries as storage time increases in this invention.

[0053] Figure 9 This is a graph showing the effect of potassium chloride environmental adaptive humidity control gel on the hardness of strawberries as storage time increases in this invention; the graph shows that the humidity control gel can delay the softening of strawberries and maintain their texture and taste.

[0054] Figure 10 This is a graph showing the effect of potassium chloride environmental adaptive humidity control gel on the soluble solids (a) and total acid (b) of strawberries as storage time increases in this invention. The graph shows that the potassium chloride humidity control gel can better maintain the sugar-acid ratio, indicating that it can maintain the flavor and quality of strawberries during storage.

[0055] Figure 11 This is a diagram showing the adsorption and desorption of potassium chloride salt gel at 25°C in this invention;

[0056] Figure 12 The diagram shows the adsorption and desorption of gelatin and potassium chloride salt gel at 25°C in this invention; (a) shows the desorption and adsorption behavior of gelatin and potassium chloride salt gel under different humidity levels; (b) shows the desorption and adsorption behavior of gelatin and lithium chloride salt gel under different humidity levels.

[0057] Figure 13 This is a graph showing the effect of lithium chloride environmental adaptive humidity-controlled gel on the rate of rice whitening as storage time increases in this invention.

[0058] Figure 14 This is a graph showing the effect of lithium chloride environmental adaptive humidity-controlled gel on the moisture content of rice as storage time increases in this invention.

[0059] Figure 15 This is a graph showing the effect of lithium chloride environmental adaptive humidity-controlled gel on the fatty acid value of rice as storage time increases in this invention.

[0060] Figure 16 This is an adsorption and desorption diagram of the polyacrylic acid-based environmentally adaptive gel at 25°C in this invention. Detailed Implementation

[0061] The present invention will be further described below with reference to the embodiments. The following embodiments are descriptive and not limiting, and should not be used to limit the scope of protection of the present invention.

[0062] The various experimental operations involved in the specific embodiments are all conventional techniques in the field. For parts not specifically annotated in this document, those skilled in the art can refer to various commonly used reference books, scientific and technological documents or related instructions and manuals prior to the filing date of this invention to carry out the operations.

[0063] A method for preparing an environmentally adaptive humidity-controlled gel includes the following steps:

[0064] (1) Mix the polymer monomers, inorganic salts, α-ketoglutaric acid, N,N'-methylenebisacrylamide and water, and stir thoroughly until dissolved and homogeneous;

[0065] (2) Mix the mixture obtained in step (1) with guar gum and stir thoroughly until the mixture is homogeneous;

[0066] (3) The mixture obtained in step (2) is cured in a 365nm ultraviolet box to obtain an environmentally adaptive humidity-controlled gel.

[0067] Preferably, the inorganic salt is one of lithium chloride, magnesium chloride, calcium chloride, sodium chloride, and potassium chloride, and the polymer monomer is acrylamide.

[0068] Preferably, the specific steps are as follows:

[0069] (1) Add inorganic salts to the acrylamide monomer solution at room temperature until it becomes supersaturated;

[0070] (2) Add α-ketoglutaric acid and N,N'-methylenebisacrylamide to step (1) and stir thoroughly until the mixture is homogeneous;

[0071] (3) Add guar gum to step (2) and stir thoroughly until the mixture is homogeneous;

[0072] (4) Place the mixture obtained in step (3) in a 365nm UV box for 100-120 minutes to obtain an environmentally adaptive humidity-controlled gel.

[0073] Preferably, the mass ratio of the polymer monomer, α-ketoglutaric acid, and N,N'-methylenebisacrylamide is 927.1:1.9:1.

[0074] Preferably, the mass ratio of the polymer monomer, inorganic salt and water is 1:3.9:7, or 1:2.1:7, or 1:1.9:7, and the inorganic salts are lithium chloride, sodium chloride and potassium chloride, respectively, corresponding to a humidity control capability of 32%, 77% or 85% for the environmental adaptive gel.

[0075] Preferably, the concentration of the acrylamide monomer solution in step (1) is 2M;

[0076] Alternatively, in step (2), the concentrations of α-ketoglutarate and N,N'-methylenebisacrylamide are both 0.1 M.

[0077] Preferably, in step (2), α-ketoglutaric acid is used as an initiator and N,N'-methylenebisacrylamide is used as a crosslinking agent.

[0078] Preferably, the guar gum has a mass fraction of 0.1% to 0.5% (wt / v) in water; or, the curing time in step (4) is 120 minutes.

[0079] The environmentally adaptive humidity-controlled gel was prepared by the method described above.

[0080] Applications of environmentally adaptive moisture-controlling gels as described above in food preservation and / or transportation.

[0081] Specifically, the relevant preparation and testing methods are as follows:

[0082] Example 1

[0083] The preparation and characterization of an environmentally adaptive humidity-controlled gel includes the following steps:

[0084] (1) Add 4.3g acrylamide monomer, 8.8mg α-ketoglutarate, 4.6mg N,N'-methylenebisacrylamide, 8.2g potassium chloride and 30.0g deionized water to a beaker and stir at 25℃ for 10 minutes to obtain a homogeneous solution.

[0085] (2) Add 0.09g of guar gum to the homogeneous solution in step (1) and stir at 25°C for 10 minutes to obtain a homogeneous solution.

[0086] (3) Transfer the uniform solution from step (2) into a 30mL syringe, degas it with argon gas 3-4 times, and solidify the sample in a 365nm UV box for 2h to obtain potassium chloride environmental adaptive gel.

[0087] (4) The humidity capability of the environmentally adaptive gel was verified using a temperature and humidity sensor, and the results are as follows: Figure 1 As shown in ab, the potassium chloride environmentally adaptive gel can absorb moisture under high humidity and desorb under low humidity, ultimately controlling the relative humidity of the environment to around 85%.

[0088] (5) The specific surface area and pore size of the environmentally adaptive gel were analyzed using the BET test, and the results are as follows: Figure 2 As shown in a, the main pore size of the potassium chloride environment adaptive gel ranges from 3 to 10 nm, and it has a certain hierarchical pore structure, but it is mainly composed of micropores and small mesopores.

[0089] (6) The water vapor adsorption isotherm and water vapor adsorption kinetics of the environmentally adaptive gel were tested using a dynamic vapor adsorption analyzer (DVS). The results are as follows: Figure 3 a, Figure 4As shown in Figure a, the water vapor adsorption isotherm of the potassium chloride environmental adaptive gel conforms to the IUPAC type III isotherm. The adsorption amount is very small at low humidity, but when the relative humidity is greater than 80%, the adsorption amount increases rapidly. The adsorption and desorption processes are reversible and there is no obvious hysteresis effect. Analysis of the kinetic curves revealed that the adsorption process of water vapor by the potassium chloride environmental adaptive humidity control gel under high humidity belongs to the pseudo-first-order kinetic model, indicating that the adsorption rate is linearly related to the concentration of the adsorbate.

[0090] (7) The humidity control capability of the environmentally adaptive gel at 37℃ was verified using a temperature and humidity sensor, and the results are as follows: Figure 5 As shown in ab, the potassium chloride environmentally adaptive gel can absorb moisture under high humidity and desorb under low humidity, ultimately controlling the relative humidity of the environment to around 81%.

[0091] (8) The humidity control capability of the environmentally adaptive gel at 4℃ was verified using a temperature and humidity sensor, and the results are as follows: Figure 6 As shown in Figure a, the potassium chloride environmentally adaptive gel can absorb moisture under high humidity and desorb under low humidity, ultimately controlling the relative humidity of the environment to around 81%.

[0092] (9) The obtained environmentally adaptive humidity control gel is applied to strawberry preservation as a moisture-absorbing pad or desiccant.

[0093] (10) Tests were conducted on the appearance, rot rate, firmness, sugar-acid ratio, and other indicators of strawberries during the preservation process. The results are as follows: Figure 7 , Figure 8 , Figure 9 , Figure 10 As shown, the potassium chloride environmentally adaptive humidity-controlled gel can significantly reduce the rot rate of strawberries, decreasing from 40.6% to 20.6% on day 4, delaying softening of strawberries, and better maintaining the sugar-acid ratio, indicating that it can maintain the flavor and quality of strawberry fruit during storage.

[0094] Comparative Example 1

[0095] The raw materials and preparation method are the same as in Example 1, except that 8.2g of potassium chloride is replaced with 5.5g of potassium chloride. The resulting potassium chloride salt gel cannot precisely control the humidity to 85%, but can only control it within the range of 79%–85%, as shown in the results. Figure 11 As shown.

[0096] Comparative Example 2

[0097] The raw materials and preparation method are the same as in Example 1, except that guar gum is replaced with gelatin. The resulting gelatin & salt gel cannot adapt to temperature changes; at low temperatures, the supersaturated salt begins to crystallize, causing the gel to transition from a supersaturated state to an unstable state, affecting its ability to regulate humidity. The result is as follows... Figure 12 As shown in a.

[0098] By comparing Example 1, Comparative Example 1 and Comparative Example 2, it can be seen that 8.2g of potassium chloride and 0.09g of guar gum have a synergistic effect in the method of the present invention, which can synergistically improve the relevant properties of the prepared environmentally adaptive humidity-controlled gel.

[0099] Example 2

[0100] The preparation of an environmentally adaptive humidity-controlled gel and its application in rice storage includes the following steps:

[0101] (1) The formulation in Example 1 was changed to 4.3g acrylamide monomer, 8.8mg α-ketoglutarate, 4.6mg N,N'-methylenebisacrylamide, 16.6g lithium chloride, 0.09g guar gum, and 30.0g deionized water to obtain lithium chloride environmental adaptive gel. Other parameters are the same as in Example 1.

[0102] (2) The humidity capability of the environmentally adaptive gel was verified using a temperature and humidity sensor, and the results are as follows: Figure 1 As shown in cd, the lithium chloride environmentally adaptive gel can absorb moisture under high humidity and desorb under low humidity, ultimately controlling the relative humidity of the environment to about 32%.

[0103] (3) The specific surface area and pore size of the environmentally adaptive gel were analyzed using the BET test, and the results are as follows: Figure 2 As shown in b, the main pore size of the lithium chloride environmental adaptive gel is between 15-30 nm, the material has a relatively uniform pore structure, and there are few micropores and macropores on the material surface.

[0104] (4) The water vapor adsorption isotherm and water vapor adsorption kinetics of the environmentally adaptive gel were tested using a dynamic vapor adsorption analyzer (DVS). The results are as follows: Figure 3 b、 Figure 4 As shown in b, the water vapor adsorption isotherm of the lithium chloride environmentally adaptive gel conforms to the IUPAC type IV isotherm. With increasing relative humidity, the adsorption amount initially increases, but the rate of increase is relatively slow. When the relative humidity exceeds 80%, the adsorption amount rises sharply. Analysis of the kinetic curves reveals that the adsorption process of the lithium chloride environmentally adaptive humidity-controlled gel belongs to a pseudo-first-order kinetic model, indicating that the rate of the entire adsorption process is linearly related to the concentration of the adsorbate.

[0105] (5) The humidity control capability of the environmentally adaptive gel at 37℃ was verified using a temperature and humidity sensor, and the results are as follows: Figure 5 As shown in cd, the lithium chloride environmentally adaptive gel can absorb moisture under high humidity and desorb under low humidity, ultimately controlling the relative humidity of the environment to around 50%.

[0106] (6) The humidity control capability of the environmentally adaptive gel at 4℃ was verified using a temperature and humidity sensor, and the results are as follows: Figure 6 As shown in b, the lithium chloride environmentally adaptive gel can absorb moisture under high humidity and desorb under low humidity, ultimately controlling the relative humidity of the environment to around 37%.

[0107] (7) The obtained environmental adaptive humidity control gel was applied to rice storage in the form of a moisture-absorbing bag.

[0108] (8) The characteristics of rice during storage, such as the rate of bad white grains, moisture content, and fatty acids, were measured, and the results are as follows: Figure 13 , Figure 14 , Figure 15 As shown, proper humidity control can reduce the white grains, moisture content, and fatty acid value of rice, thus better maintaining the quality of rice.

[0109] Comparative Example 3

[0110] The raw materials and preparation method are the same as in Example 2, except that 16.6g of lithium chloride is replaced with 8.3g of lithium chloride. The resulting gel cannot precisely control the humidity at 32%, but can only control the humidity within the range of 25% to 32%.

[0111] Comparative Example 4

[0112] The raw materials and preparation method are the same as in Example 2, except that guar gum is replaced with gelatin. The resulting gel cannot adapt to the effects of temperature changes. Increased temperature usually increases the solubility of supersaturated salts, making salt crystals more easily soluble. Furthermore, the physical properties of gelatin are affected, reducing viscosity and elasticity, leading to an unstable gel structure and causing the gel to lose its humidity control ability. The results are as follows... Figure 12 As shown in b.

[0113] By comparing Example 2, Comparative Example 3 and Comparative Example 4, it can be seen that 16.6g of lithium chloride and 0.09g of guar gum have a synergistic effect in the method of the present invention, which can synergistically improve the relevant properties of the prepared environmental adaptive humidity-controlled gel.

[0114] Example 3

[0115] The preparation and characterization of an environmentally adaptive humidity-controlled gel includes the following steps:

[0116] (1) Add 9.6g of acrylic acid monomer, 12mg of N,N'-methylenebisacrylamide, 17.2g of anhydrous magnesium chloride and 30.0g of deionized water to a beaker and stir at 25℃ for 30 minutes to obtain a homogeneous solution.

[0117] (2) Add 0.09g of guar gum to the homogeneous solution in step (1) and stir at 25°C for 10 minutes to obtain a homogeneous solution.

[0118] (3) Add 0.03g of potassium persulfide to the homogeneous solution in step (2) and stir at 25°C for 30 minutes to obtain a homogeneous solution.

[0119] (4) Transfer the uniform solution from step (3) into a 30mL syringe, degas it with argon gas 3-4 times, and cure the sample in a constant temperature oven at 60℃ for 12h to obtain polyacrylic acid-based environmental adaptive gel.

[0120] (5) The humidity capability of the polyacrylic acid-based environmentally adaptive gel was verified using a temperature and humidity sensor, and the results are as follows: Figure 16 As shown, the polyacrylic acid-based environmentally adaptive gel can absorb moisture under high humidity and desorb under low humidity, ultimately controlling the relative humidity of the environment to around 47%.

[0121] Although embodiments of the invention have been disclosed for illustrative purposes, those skilled in the art will understand that various substitutions, variations, and modifications are possible without departing from the spirit and scope of the invention and the appended claims. Therefore, the scope of the invention is not limited to the contents disclosed in the embodiments.

Claims

1. A method for preparing an environment-adaptive humidity control gel, characterized by: The method comprises the following steps: (1) mixing a gel pre-polymer solution, an inorganic salt and water, and stirring thoroughly until dissolved uniformly; (2) mixing the mixture obtained in step (1) with guar gum, and stirring thoroughly until mixed uniformly; (3) solidifying the mixture gel obtained in step (2) to obtain an environment-adaptive humidity-controlling gel.

2. The method of claim 1, wherein: The inorganic salt can be any water-soluble salt, and examples include but are not limited to one or a mixture of several of lithium chloride, magnesium chloride, calcium chloride, sodium chloride and potassium chloride. The gel can be any polymer system capable of polymerization to form a solid state, and specific examples include but are not limited to polyacrylamide hydrogel.

3. The production method according to claim 1 or 2, characterized by: The specific steps are as follows: (1) adding an inorganic salt to an acrylamide monomer aqueous solution at room temperature until supersaturation; (2) adding α-ketoglutaric acid and N,N'-methylene bisacrylamide to the mixture in step (1) and stirring thoroughly until mixed uniformly; (3) adding guar gum to the mixture in step (2) and stirring thoroughly until mixed uniformly; (4) placing the mixture obtained in step (3) in a 365 nm ultraviolet box for 100-120 minutes to obtain an environment-adaptive humidity-controlling gel.

4. The method of claim 3, wherein: The mass fraction of the polymer monomer in water is 3%-30% (wt / v).

5. The method of claim 3, wherein: The mass fraction of the α-ketoglutaric acid in water is 0.005%-0.05% (wt / v). Alternatively, the mass fraction of the N,N'-methylene bisacrylamide in water is 0.004%-0.03% (wt / v).

6. The method of claim 3, wherein: The mass fraction of the inorganic salt in water is 10%-370% (wt / v), and the environment-adaptive gel obtained can control humidity to any value within the range of 10%-95%. Alternatively, the mass fraction of the guar gum in water is 0.1%-0.5% (wt / v).

7. The method of claim 3, wherein: The concentration of the acrylamide monomer aqueous solution in step (1) is 0.5-4 M. Alternatively, the concentrations of the α-ketoglutaric acid and the N,N'-methylene bisacrylamide in step (2) are 0.0005-0.004 M and 0.00025-0.002 M, respectively.

8. The method of claim 3, wherein: The α-ketoglutaric acid in step (2) is an initiator, and the N,N'-methylene bisacrylamide is a crosslinking agent.

9. An environment-adaptive humidity-controlling gel prepared by the method of any one of claims 1 to 8.

10. Use of the environment-adaptive humidity-controlling gel of claim 9 in food preservation and / or transportation.

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