WO2023155217A1 - 一种机械驱动力作用下的温度控释三层果蔬保鲜膜及其制备方法 - Google Patents

一种机械驱动力作用下的温度控释三层果蔬保鲜膜及其制备方法 Download PDF

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WO2023155217A1
WO2023155217A1 PCT/CN2022/077358 CN2022077358W WO2023155217A1 WO 2023155217 A1 WO2023155217 A1 WO 2023155217A1 CN 2022077358 W CN2022077358 W CN 2022077358W WO 2023155217 A1 WO2023155217 A1 WO 2023155217A1
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layer
temperature
solution
release
fruit
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PCT/CN2022/077358
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English (en)
French (fr)
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邹小波
张俊俊
石吉勇
张佳凝
黄晓玮
刘黎
胡雪桃
翟晓东
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江苏大学
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Priority to GB2302115.7A priority Critical patent/GB2618644A/en
Publication of WO2023155217A1 publication Critical patent/WO2023155217A1/zh

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    • A—HUMAN NECESSITIES
    • A23—FOODS OR FOODSTUFFS; TREATMENT THEREOF, NOT COVERED BY OTHER CLASSES
    • A23B—PRESERVING, e.g. BY CANNING, MEAT, FISH, EGGS, FRUIT, VEGETABLES, EDIBLE SEEDS; CHEMICAL RIPENING OF FRUIT OR VEGETABLES; THE PRESERVED, RIPENED, OR CANNED PRODUCTS
    • A23B7/00—Preservation or chemical ripening of fruit or vegetables
    • A23B7/16—Coating with a protective layer; Compositions or apparatus therefor
    • A—HUMAN NECESSITIES
    • A23—FOODS OR FOODSTUFFS; TREATMENT THEREOF, NOT COVERED BY OTHER CLASSES
    • A23V—INDEXING SCHEME RELATING TO FOODS, FOODSTUFFS OR NON-ALCOHOLIC BEVERAGES AND LACTIC OR PROPIONIC ACID BACTERIA USED IN FOODSTUFFS OR FOOD PREPARATION
    • A23V2002/00—Food compositions, function of food ingredients or processes for food or foodstuffs
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02W—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO WASTEWATER TREATMENT OR WASTE MANAGEMENT
    • Y02W90/00—Enabling technologies or technologies with a potential or indirect contribution to greenhouse gas [GHG] emissions mitigation
    • Y02W90/10—Bio-packaging, e.g. packing containers made from renewable resources or bio-plastics

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  • the invention belongs to the technical field of intelligent controlled-release antibacterial packaging, and in particular relates to a temperature-controlled antibacterial three-layer film under the action of a mechanical driving force and a preparation method thereof.
  • active ingredients such as natural extracts, chitosan, metal nanoparticles, etc. are coated on the surface or directly added to polymer materials such as renewable substances (polysaccharides, polypeptides, lipids), polylactic acid, and polyhydroxyalkanoate.
  • polymer materials such as renewable substances (polysaccharides, polypeptides, lipids), polylactic acid, and polyhydroxyalkanoate.
  • the polymer substrate of controlled-release packaging usually has strong resistance to the release path of antibacterial agents, resulting in no release of antibacterial packaging in the early stage; and when stimulation occurs, the polymer substrate will undergo conformational or structural changes, directly reducing its release path. At this time, the antimicrobial agent is released into the package according to the law of diffusion release kinetics.
  • thermosensitive polymers can be used for food temperature-controlled release antibacterial cling film.
  • patent CN110724295A discloses a temperature-sensitive polyurethane gas-phase controlled release anti-oxidation composite film, which controls the temperature to change the size of its free volume cavity, reduces the release resistance to antibacterial agents, and finally can control the release of antibacterial agents at different temperatures;
  • NIPAM temperature-responsive polymer
  • NIPAM N-isopropylacrylamide
  • Destruction reduces the resistance of the polymer to the active molecule, directly "opens" the release path of the antibacterial agent, and is macroscopically manifested in the controlled release of the active ingredient from the temperature of the polymer surface.
  • the above technologies provide a basis for the development of temperature-controlled release packaging films, but the existing published temperature-sensitive antibacterial packaging relies on temperature stimulation to change the conformation of the polymer. Although this change after stimulation can reduce the resistance to the release path of antibacterial agents , but its release kinetics is still poor in concentration and the direction of the active ingredient release is uncontrollable.
  • the present invention proposes a controlled-release mechanism of a three-layer fruit and vegetable plastic wrap, which is specifically assembled from a temperature-sensitive inner layer, a deformable middle layer and a mechanical outer layer.
  • the three-layer film can effectively improve the power of the release path of the antibacterial active ingredient on the basis of controlling the direction of the release path of the antibacterial active ingredient, so as to optimize the preservation effect.
  • the three-layer membrane combines the hydrogen bond interaction between the hydrogel layers through layer-by-layer assembly technology, which significantly improves the compatibility of the membrane.
  • the present invention overcomes the fact that the ambient temperature cannot quickly respond to the temperature particle layer of the inner film due to the film thickness of the three-layer film , making Smart Response insensitive to issues.
  • the present invention aims to solve technical problems such as insufficient power in the release path of the antibacterial active ingredient and uncontrollable diffusion direction of the active ingredient after the stimulation "switch" is generated in the existing controlled-release packaging.
  • the present invention provides a mechanical driving force The temperature-controlled release antibacterial three-layer film preparation method under the following conditions.
  • the temperature-controlled release antibacterial three-layer film under the action of mechanical driving force is composed of an inner layer, a middle layer and an outer layer;
  • the inner layer is a temperature-sensitive layer, which can change the release path of the antibacterial active ingredient of the polymer at different temperatures Resistance, macroscopically manifested as the "switch" release of antibacterial active ingredients;
  • the middle layer is a deformable layer, which has the characteristics of thermal expansion and contraction, and will expand as the temperature rises, thereby directly generating extrusion stress on the inner and outer layers;
  • the outer layer is rigid Layer (mechanical outer layer), with excellent mechanical properties, can not only serve as the barrier layer of the three-layer film, but also provide a centripetal driving force for the release of the active ingredients of the inner film.
  • the final performance is based on controlling the direction of the release path of the antibacterial active ingredient, effectively improving the release path dynamics of the antibacterial active ingredient, so as to optimize the preservation effect.
  • Step 1 preparation of temperature-sensitive inner layer solution
  • the dosage ratio of chitosan, monomer N-isopropylacrylamide, ammonium cerium nitrate and acetic acid solution in step S1 is 5 ⁇ 10g:5 ⁇ 2g:1g:20 ⁇ 50mL; the acetic acid solution The volume concentration is 2%-5%; the adjustment to a certain temperature is 40-50°C; the reaction period is 24-48h.
  • the organic solution described in step S1 is any one or multiple composite solutions in any proportion of acetone, dichloromethane, chloroform, N-N dimethylacetamide, ethyl acetate, or dihydrofuran;
  • the volume ratio of the mixed solution to the organic solvent is 1:5-15, and the drying temperature is 25-40°C.
  • the essential oil described in step S2 is any one of oregano essential oil, cinnamon essential oil, japonica essential oil, clove essential oil or thyme essential oil; the volume concentration of the ethanol solution is 50%; the essential oil in the mixed solution A The mass concentration is 1.5% to 3%.
  • the mass concentration of the temperature-sensitive particle dispersion in step S2 is 1-3 g/mL; the mixed solution A is added to the temperature-sensitive particle dispersion, and the volume ratio of the two is 1:5-10;
  • the reaction temperature under the above-mentioned certain temperature condition is 18-25° C., and the time is 6-8 hours; the time of the dialysis is 6-18 hours.
  • Step 2 preparation of deformable intermediate layer solution
  • the dosage ratio of gelatin, sodium alginate and distilled water in step 2 is 1-2g:2-4g:100mL; the certain temperature condition is 40-60°C; the nano-zinc oxide is compounded in the hydrogel
  • the mass concentration in the solution is 0.01-0.03%; the volume concentration of the glycerin in the hydrogel composite solution is 1-2%.
  • Step 3 preparation of rigid outer layer solution
  • the dosage ratio of polyvinyl alcohol, agar, and distilled water in step 3 is 2-4g:0.5-2g:100mL; the heating to a certain temperature is 90-100°C, and the stirring time is 1-2h; The mass concentration of the titanium dioxide in the composite solution is 0.01-0.05%, and the volume concentration of the glycerin in the composite solution is 1-4%.
  • Step 4 layer-by-layer assembled fruit and vegetable surface coating
  • the temperature-sensitive inner layer solution, the deformable middle layer solution and the rigid outer layer solution are sprayed layer by layer on the surface of fruits and vegetables through spray-type layer-by-layer assembly, so that three layers of plastic wrap are produced successively, which is the temperature control under the action of mechanical driving force. Release three layers of fruit and vegetable plastic wrap.
  • the fruits and vegetables described in Step 4 are specifically spherical fruits and vegetables, including apples, citrus fruits, peaches, cherry tomatoes, tomatoes, round pears or round eggplants.
  • the chitosan at the chain end of the temperature-sensitive particle in the temperature-sensitive layer solution is a polycation, and the amino group in its structure is easily protonated into -NH 3 + in the solution, which is positively charged; the sodium alginate contained in the deformation intermediate layer It is a polyanion, and the carboxyl group (-COOH) in its structure forms a large number of -COO - in the solution, which is negatively charged.
  • connection method of the temperature-sensitive inner layer and the middle layer is assembled layer by layer through the electrostatic force between positive and negative charges;
  • the deformable middle layer adopts gelatin and sodium alginate hydrogel and contains a large amount of hydrogen bonds between the agar of the rigid outer layer, and the hydrogen bonds can improve the binding force between the two membranes;
  • the ZnONPs in the deformable middle layer has high thermal conductivity, good thermal stability and antibacterial properties; the TiO 2 in the rigid outer layer has high thermal conductivity and has a certain resistance to ultraviolet rays.
  • the CS-PNIPAM temperature-sensitive particles in the inner film of the present invention have a low critical solution temperature (LCST) close to the temperature of the human body.
  • the inner temperature-sensitive layer can respond to temperature changes, change the conformation of the polymer, and reduce the resistance of the polymer to the release path of essential oils, thereby effectively improving the rapid growth of microorganisms caused by abnormal changes in ambient temperature during the storage and sale of fruits and vegetables.
  • the intermediate hydrogel layer of the present invention is an expansion layer, which can produce extrusion stress after the ambient temperature changes and act on the rigid outer layer and the temperature-sensitive inner layer simultaneously, while the spherical fruit and vegetable rigid outer layer has a stronger Mechanical properties, it will resist the extrusion stress brought by the expansion layer, so all the deformation forces will be applied to the temperature-sensitive inner layer, and finally act as centripetal force.
  • the centripetal force can directly increase the power of the release path of the essential oil in the temperature-sensitive particles, effectively accelerating the release rate of the essential oil; and the existence of the centripetal force can effectively control the direction of the release path of the antibacterial active ingredients, and promote the effective release of the antibacterial active ingredients to the surface of fruits and vegetables , rather than a random outward diffusion release. Therefore, finally, on the basis of controlling the direction of the release path of the antibacterial active ingredient, the present invention can also effectively improve the power of the release path of the antibacterial active ingredient, thereby optimizing the preservation effect.
  • Both the TiO2 nanoparticles in the outer layer and the ZnONPs nanoparticles in the middle layer have good thermal conductivity, which can overcome the defect that the temperature response is not timely due to the thickness of the multi-layer film, so that the change of the ambient temperature is quickly transmitted to the inner layer
  • the film promotes the rapid temperature response of the temperature-sensitive inner layer film, and promptly responds to the problem of accelerated spoilage of fruits and vegetables caused by changes in the external environment temperature.
  • TiO 2 also has excellent anti-ultraviolet properties, which can improve the photostability of the three-layer film, thereby protecting the stability of the active ingredients
  • the ZnONPs in the middle layer also has antibacterial properties, and can directly treat the surface of fruits and vegetables without external temperature stimulation. Initial sterilization, thereby further reducing the damage of microbial infection to fruits and vegetables, and prolonging the storage period of fruits and vegetables themselves.
  • the present invention adopts the film-forming mode of layer-by-layer assembly to prepare a three-layer film, and effectively improves the adsorption force between the two-layer films by the electrostatic force between the polyelectrolyte cation in the inner layer film and the anion in the middle layer film;
  • the hydrogen bond force between the hydrogel polymer of the membrane and the polymer of the outer membrane effectively improves the binding force between the two membranes.
  • Fig. 1 is the schematic diagram of the controlled-release three-layer fruit and vegetable fresh-keeping film prepared by the present invention.
  • Fig. 2 is a graph showing the release rates of the temperature-sensitive particles in the inner layer in Example 1 of the present invention at 25°C and 37°C respectively.
  • A is a diagram of the thermal expansion rate of the middle layer of the fresh-keeping film in Example 2 of the present invention at different temperatures;
  • B is a diagram of the thermal expansion rate of the comparative example of the plastic wrap without adding ZnONPs at different temperatures.
  • A is the anti-ultraviolet barrier characteristic curve of the outer layer film in Example 3 of the present invention
  • B is the anti-ultraviolet barrier curve of the comparative example without adding TiO
  • illustrations a and b are respectively embodiment 3 and corresponding comparative examples Photo transmittance diagram of the outer film.
  • Fig. 5 is a zeta potential diagram of the inner film and the outer film in Example 3 of the present invention.
  • a method for preparing a temperature-controlled antibacterial three-layer film under the action of a mechanical driving force which is specifically assembled from an inner layer, a middle layer, and an outer layer;
  • the inner layer is a temperature-sensitive layer, which can change the antibacterial activity of polymers at different temperatures The resistance of the release path of the ingredients, so that the macroscopic performance is the "switch" release of the antibacterial active ingredients;
  • the middle layer is a deformable layer, which has the characteristics of thermal expansion and cold contraction, and will expand as the temperature rises, thereby directly generating extrusion stress on the inner and outer layers ;
  • the outer layer is a rigid layer (mechanical outer layer) with excellent mechanical properties, which can not only be used as a barrier layer of the three-layer film, but also provide a centripetal driving force for the release of the active ingredients of the inner film.
  • the final expression is that on the basis of controlling the direction of the release path of the antibacterial active ingredient, the power of the release path of the antibacterial active ingredient is effectively improved,
  • Step 1 preparation of temperature-sensitive inner layer solution
  • step S2 3g of cinnamon essential oil is completely dissolved in 20mL of ethanol solution with a volume concentration of 50% to obtain a mixed solution A for subsequent use; 1g of the temperature-sensitive particles prepared in step S1 is completely dissolved in 100mL of distilled water, and then the mixed solution A is added to the temperature In the sensitive particle dispersion solution, fully react and adsorb at 18°C for 6 hours, and then dialyze through distilled water for 6 hours to remove uncoated free cinnamon essential oil.
  • the dialyzed solution is the temperature-sensitive inner layer solution loaded with active substances.
  • the inner layer solution was formed into a film by casting drying method, and the essential oil of the inner layer film in 0.1M PBS buffer solution at 25°C and 37°C was tested by the shaking table method
  • the cumulative release rate was further calculated by testing the concentration of the essential oil in the simulated solution. As shown in Figure 2, the cumulative release rate of the temperature-sensitive inner layer solution was significantly higher at 37°C.
  • Step 2 preparation of deformable intermediate layer solution
  • the interlayer hydrogel composite solution which is the deformable interlayer solution.
  • the mass concentration of nano-zinc oxide in the hydrogel composite solution is 0.01%
  • the volume concentration of glycerin in the hydrogel composite solution is 1%
  • the added nano-zinc oxide has a high thermal conductivity, good thermal conductivity Stability and antibacterial properties can quickly sense changes in the external temperature environment to the inner film, so that the "switch" path of the inner film can be opened in time, reducing the resistance of the release path, and quickly releasing active substances;
  • Step 3 preparation of rigid outer layer solution
  • Step 4 layer-by-layer assembled fruit and vegetable surface coating
  • the temperature-sensitive inner layer solution, the deformable middle layer solution and the rigid outer layer solution are sprayed onto the surface of the orange in sequence through a spray-type layer-by-layer assembly method, so that three layers of plastic wrap are successively produced on the surface of the orange, which are temperature-sensitive from the inside to the outside.
  • An inner layer, a deformable middle layer and a rigid outer layer can be used to preserve the freshness of oranges.
  • the chitosan at the end of the temperature-sensitive particles in the solution of the temperature-sensitive layer is a polycation, and the amino group in its structure is easily protonated into -NH 3 + in the solution, which is positively charged; the sodium alginate contained in the deformable middle layer is a polyanion, and its The carboxyl group (-COOH) in the structure forms a large number of -COO - in the solution, which is negatively charged, so the connection mode of the temperature-sensitive inner layer and the middle layer film is assembled layer by layer through the electrostatic force between positive and negative charges; while the middle layer There are a lot of hydration hydrogen bonds between the gelatin and sodium alginate hydrogel and the agar (gel) and polyvinyl alcohol of the outer membrane, and the hydrogen bonds can improve the binding force between the two membranes, and finally make the three layers
  • the fresh-keeping films are firmly combined with each other, which can more effectively play the specific functions of the three layers of films.
  • a method for preparing a temperature-controlled release antibacterial three-layer film under the action of a mechanical driving force which is specifically assembled from an inner layer, a middle layer and an outer layer.
  • the inner layer is a temperature-sensitive layer, which can change the resistance of the polymer to the release path of the antibacterial active ingredient at different temperatures, and the macroscopic performance is the "switch" release of the antibacterial active ingredient;
  • the outer layer is a rigid layer (mechanical outer layer), which has excellent mechanical properties, and can be used as a barrier layer for a three-layer film and as an inner layer.
  • the release of membrane active components provides the centripetal drive.
  • the final performance is based on controlling the direction of the release path of the antibacterial active ingredient, effectively improving the release path dynamics of the antibacterial active ingredient, so as to optimize the preservation effect. Including the following steps:
  • Step 1 preparation of temperature-sensitive inner layer solution
  • Step 2 preparation of deformable intermediate layer solution
  • the middle layer hydrogel composite solution Dissolve 1.5g of gelatin and 2.5g of sodium alginate in 100mL of distilled water and stir evenly at 50°C, then add ZnONPs and glycerol to obtain the middle layer hydrogel composite solution.
  • the mass concentration of nano-zinc oxide in the hydrogel composite solution is 0.03%, and the volume concentration of glycerin in the hydrogel composite solution is 1.5%;
  • the added nano-zinc oxide has a higher thermal conductivity, good thermal conductivity Stability and antibacterial properties can quickly sense changes in the external temperature environment to the inner film, so that the "switch" path of the inner film can be opened in time, reducing the resistance of the release path, and quickly releasing active substances;
  • the middle layer hydrogel composite solution into a film by casting drying method.
  • the expansion rate of the middle layer of plastic wrap in PBS buffer solution was tested at different temperatures.
  • the present invention also sets up a deformed intermediate layer solution without adding ZnONPs to form a film.
  • the operation steps are the same as step 2, the only difference is that ZnONPs are not added.
  • Step 3 preparation of rigid outer layer solution
  • Step 4 layer-by-layer assembled fruit and vegetable surface coating
  • the temperature-sensitive inner layer solution, the deformable middle layer solution and the rigid outer layer solution are sprayed on the surface of the apple in a spray-type layer-by-layer assembly form, so that three layers of plastic wrap are produced successively, from the inside to the outside.
  • a sensitive inner layer, a deformable middle layer and a rigid outer layer can be used for fresh-keeping of apples.
  • the chitosan at the end of the temperature-sensitive particles in the solution of the temperature-sensitive layer is a polycation, and the amino group in its structure is easily protonated into -NH 3 + in the solution, which is positively charged; the sodium alginate contained in the deformable middle layer is a polyanion, and its The carboxyl group (-COOH) in the structure forms a large number of -COO - in the solution, which is negatively charged, so the temperature-sensitive inner layer and the middle layer film are assembled layer by layer through the electrostatic force between the positive and negative charges; while the gelatin and the middle layer There are a lot of hydration hydrogen bonds between the sodium alginate hydrogel and the agar (gel) and polyvinyl alcohol of the outer membrane, and the hydrogen bonds can improve the binding force between the two membranes, and finally make the three layers of plastic wrap mutually The combination between them is firm, and the specific functions of the three layers of films can be played more effectively.
  • a method for preparing a temperature-controlled release antibacterial three-layer film under the action of a mechanical driving force which is specifically assembled from an inner layer, a middle layer and an outer layer.
  • the inner layer is a temperature-sensitive layer, which can change the resistance of the release path of the polymer to the antibacterial active ingredient at different temperatures, and the macroscopic performance is the "switch" release of the antibacterial active ingredient; It expands as the temperature rises, thereby directly generating compressive stress on the inner and outer layers;
  • the outer layer is a rigid layer (mechanical outer layer) with excellent mechanical properties, which can be used as a barrier layer of a three-layer film and as an inner layer
  • the release of membrane active components provides the centripetal drive.
  • the final performance is based on controlling the direction of the release path of the antibacterial active ingredient, effectively improving the release path dynamics of the antibacterial active ingredient, so as to optimize the preservation effect. Including the following steps:
  • Step 1 preparation of temperature-sensitive inner layer solution
  • Step 2 preparation of deformable intermediate layer solution
  • the middle layer hydrogel composite solution can be obtained.
  • the mass concentration of nano-zinc oxide in the hydrogel composite solution is 0.02%
  • the volume concentration of glycerin in the hydrogel composite solution is 2%
  • the added nano-zinc oxide has a high thermal conductivity, good thermal conductivity Stability and antibacterial properties can quickly sense changes in the external temperature environment to the inner film, so that the "switch" path of the inner film can be opened in time, reducing the resistance of the release path, and quickly releasing active substances;
  • Step 3 preparation of rigid outer layer solution
  • Step 4 layer-by-layer assembled fruit and vegetable surface coating
  • the temperature-sensitive inner layer solution, the deformable middle layer solution and the rigid outer layer solution are sprayed on the surface of the cherry tomato by spraying the multi-layer film solution in the form of layer-by-layer assembly, so that three layers of preservative films are successively produced on the surface of the cherry tomato, From the inside to the outside are the temperature-sensitive inner layer, the deformable middle layer and the rigid outer layer, which can be used for the preservation of cherry tomatoes.
  • the chitosan at the end of the temperature-sensitive particles in the solution of the temperature-sensitive layer is a polycation, and the amino group in the structure is easily protonated into -NH 3 + in the solution, which is positively charged; the sodium alginate contained in the deformable middle layer is a polyanion, and its The carboxyl group (-COOH) in the structure forms a large number of -COO - in the solution, which is negatively charged, so the temperature-sensitive inner layer and the middle layer film are assembled layer by layer through the electrostatic force between the positive and negative charges; while the gelatin and the middle layer There are a large number of hydration hydrogen bonds between the sodium alginate hydrogel and the agar (gel) and polyvinyl alcohol of the outer membrane, and the hydrogen bonds can improve the binding force between the two membranes, and finally make the three layers of plastic wrap mutually The combination between them is firm, and the specific functions of the three layers of films can be played more effectively.
  • the Zeta potential of the two solutions was characterized. The results are shown in Figure 5. Because the temperature-sensitive inner layer contains chitosan polycations, its Zeta potential value is positive, which is 21.65mV; while the deformable middle layer contains sodium alginate polyanions, its Zeta potential value is negative. is 25.15mV.
  • the mechanical properties of the temperature-sensitive inner layer solution, the deformable middle layer solution and the rigid outer layer solution were prepared by casting and drying.
  • the results in Table 1 verify that the rigid outer layer film has a higher
  • the mechanical properties further prove that it can act as the resistance of the deformation interlayer, which increases the path dynamics of antimicrobial agent release, and finally can increase the effective release rate of essential oil.

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Abstract

属于智能控释抗菌包装技术领域，具体涉及一种机械驱动力作用下的温度控释抗菌三层膜及其制备方法。首先制备温敏内层溶液、形变中间层溶液和刚性外层溶液，并逐层喷涂到果蔬表面，使其先后产生三层保鲜膜，可用于果蔬保鲜；采用层层组装的成膜方式制备三层膜，可以使得在控制抗菌活性成分释放路径方向的基础上，有效提高抗菌活性成分的释放路径动力，从而使得保鲜效果的最佳化；通过在刚性外层溶液和形变中间层溶液中分别添加导热粒子，克服因多层膜厚造成温度响应不及时的缺陷；解决了现有控释包装在刺激"开关"产生后，仍然存在抗菌活性成分释放路径动力不足以及活性成分的扩散方向不可控性的技术问题。

Description

[根据细则37.2由ISA制定的发明名称]　一种机械驱动力作用下的温度控释三层果蔬保鲜膜及其制备方法 技术领域
本发明属于智能控释抗菌包装技术领域，具体涉及一种机械驱动力作用下的温度控释抗菌三层膜及其制备方法。
背景技术
目前将活性成分如天然提取物、壳聚糖、金属纳米粒子等在表面涂覆或者直接加入可再生物质(多糖、多肽、脂类)、聚乳酸、聚羟基脂肪酸酯等聚合物材料是活性包装技术的重大进展之一。其中，抗菌包装膜中活性成分的释放规律可以从动力和阻力相互拮抗的观点来验证，通常来说活性成分的浓度差可作为其释放的传质动力，而聚合物基材的物理化学性质则成为抗菌剂释放的路径阻力。常见抗菌包装中聚合物对抗菌剂释放的路径阻力较小，因而传质动力就占主要优势，使得抗菌活性成分从聚合物表面以扩散的形式释放到包装体系内部，有效杀灭食品表面的微生物，最终可达到杀菌的效果。然而这种传统抗菌包装的释放规律与食品的保鲜需求不一致，且容易使细菌产生耐药性。因此，按需释放的食品抗菌包装新要求应运而生。基于此，控释抗菌包装体系成为近年来的研究热点。控释包装聚合物基材通常对抗菌剂的释放路径有较强的阻力，造成抗菌包装在初期不释放；而当刺激发生后，聚合物基材会发生构象或者结构变化，直接降低其释放路径阻力，此时才使得抗菌剂再按照扩散释放动力学规律释放到包装内部。
不同的刺激信号匹配不同的聚合物，其中温敏型聚合物可用于食品温度控释抗菌保鲜膜。其中专利CN110724295A公布了一种温敏聚氨酯气相控释的抗氧化复合膜，控制温度改变其自由体积空洞的尺寸大小，降低对抗菌剂的释放阻力，最终可以控制不同温度下抗菌剂的释放量；还有文献公布了一种温度响应性的高分子聚合物(N～异丙基丙烯酰胺)(NIPAM)材料，其大分子侧链上同时含有亲水性的酰胺基和疏水性的异丙基，具有独特温度响应性机制：在温度低于LCST时，聚合物链处于伸展状态，周围聚集着大量的水分子，形成一层厚厚的水合壳，致使聚合物“开关”关闭，直接增加抗菌活性成分释放的路径阻力；温度高于LCST时，其聚合物结构中的疏水性异丙基脱水，触发了疏水基团间的疏水相互作用，聚合物链卷曲收缩明显且周围水合层也遭到破坏，降低了聚合物对活性分子的阻碍，直接“打开”抗菌剂的释放路径通道，宏观表现在活性成分从聚合物表面的温度“开关”控释。以上技术为温度控释包装膜的开发提供了基础，但现有公布的温敏抗菌包装均是依靠温度刺激改变聚合物的构象，这种刺激后的变化虽然可以降低对抗菌剂的释放路径阻力，但其释放动力仍然是浓度差且活性成分释放后的方向不可控。因此这种控释智能包装存在两个问题：一是控释作用发生后，抗菌剂释放的扩散方向仍然具有不可控性，表现在包装环境中的无序扩散，导致 一部分抗菌活性成分没有扩散到食品表面，产生抗菌剂浪费的现象；另一个问题是抗菌剂释放后的传质动力还仅仅依靠浓度差，动力较小且伴随着释放时间的增加，其动力会越来越小，最终会造成扩散到食品表面的抗菌剂作用不及时带来的保鲜效果差等问题发生。
基于此，本发明提出一种三层果蔬保鲜膜的控释机制，具体由温敏内层、形变中间层和机械外层组装而成。三层膜可实现控制抗菌活性成分释放路径方向的基础上，有效提高抗菌活性成分的释放路径动力，使得保鲜效果的最佳化。三层膜通过层层组装技术结合水凝胶层间的氢键相互作用，显著提高膜的相容性。现有技术中未见有研究公开关于为抗菌活性成分的释放提供路径方向及动力的方法；此外本发明克服了由于三层膜的膜厚造成环境温度无法快速响应到内层膜的温度粒子层，使得智能响应不灵敏问题。
发明内容
本发明旨在解决现有控释包装在刺激“开关”产生后，仍然存在抗菌活性成分释放路径动力不足以及活性成分的扩散方向不可控性等技术问题，本发明提供了一种机械驱动力作用下的温度控释抗菌三层膜制备方法。其中机械驱动力作用下的温度控释抗菌三层膜，具体由内层、中间层和外层组装而成；内层为温敏层，可改变不同温度下聚合物对抗菌活性成分的释放路径阻力，宏观表现为抗菌活性成分的“开关”释放；中间层为形变层，具有热胀冷缩特性，会随着温度升高而膨胀，从而直接对内外层产生挤压应力；外层为刚性层(机械外层)，具有优良的机械性能，既能作为三层膜的阻隔层，又可为内层膜活性成分的释放提供向心驱动力。最终表现在控制抗菌活性成分释放路径方向的基础上，有效提高抗菌活性成分的释放路径动力，使得保鲜效果的最佳化。
本发明通过以下技术手段实现上述技术目的，具体制备包括如下步骤：
步骤一、温敏内层溶液的制备；
S1.取壳聚糖(CS)溶于乙酸溶液中，然后加入单体N-异丙基丙烯酰胺(NIPAM)并搅拌均匀，将得到的溶液调整至一定温度后再加入硝酸铈铵(CAN)溶液作为引发剂，然后通氮气保护，在反应一段时间后的混合溶液中加入有机溶剂进行沉淀析出得到粗产物，再经抽提得到细分物，然后经干燥后得到终产物，即为CS-PNIPAM温敏粒子；
进一步的，步骤S1中所述壳聚糖、单体N-异丙基丙烯酰胺、硝酸铈铵和乙酸溶液的用量比为5～10g:5～2g:1g:20～50mL；所述乙酸溶液的体积浓度为2％～5％；所述调整至一定温度为40～50℃；所述反应一段时间为24～48h。
进一步的，步骤S1中所述有机溶液为丙酮、二氯甲烷、三氯甲烷、N-N二甲基乙酰胺、乙酸乙酯、或者二氢呋喃的任意一种或者多种任意比例的复合溶液；所述混合溶液与有机溶剂的体积比为1:5-15，所述干燥的温度为25～40℃。
S2.取精油溶于乙醇溶液中得到混合溶液A；再将步骤S1制备的温敏粒子溶解在蒸馏水中配制成一定质量浓度的温敏粒子分散液；然后将混合溶液A添加到温敏粒子分散液中得到混合溶液B，在一定温度条件下反应后，再将混合溶液B经蒸馏水进行透析去除未被包覆的游离肉桂精油，获得透析后的溶液即为装载有活性物质的温敏内层溶液；
进一步的，步骤S2中所述精油为牛至精油、肉桂精油、按叶精油、丁香精油或百里香精油中的任意一种；所述乙醇溶液的体积浓度为50％；所述混合溶液A中精油的质量浓度为1.5％～3％。
进一步的，步骤S2中所述温敏粒子分散液的质量浓度为1～3g/mL；所述混合溶液A添加到温敏粒子分散液中，两者的体积比为1：5～10；所述一定温度条件下反应的温度为18～25℃，时间为6～8h；所述透析的时间为6～18h。
步骤二、形变中间层溶液的制备；
将明胶和海藻酸钠溶于蒸馏水中，并在一定温度条件下搅拌均匀，然后添加的纳米氧化锌(ZnONPs)和甘油，得到水凝胶复合溶液，即为形变中间层溶液；
进一步的，步骤二中所述明胶、海藻酸钠和蒸馏水的用量比为1～2g:2～4g:100mL；所述一定温度条件为40～60℃；所述纳米氧化锌在水凝胶复合溶液中的质量浓度为0.01～0.03％；所述甘油在水凝胶复合溶液中的体积浓度为1～2％。
步骤三、刚性外层溶液的制备；
取聚乙烯醇和琼脂溶于蒸馏水中，加热至一定温度搅拌后，再添加纳米二氧化钛(TiO 2)和甘油，搅拌均匀后得到复合溶液，即为刚性外层溶液：
进一步的，步骤三中所述聚乙烯醇、琼脂、蒸馏水的用量比为2～4g:0.5～2g:100mL；所述加热至一定温度为90～100℃，搅拌的时间为1～2h；所述二氧化钛在复合溶液中的质量浓度为0.01～0.05％，所述甘油在复合溶液中的体积浓度为1～4％。
步骤四、层层组装的果蔬表面涂覆；
将温敏内层溶液、形变中间层溶液和刚性外层溶液通过喷雾式的层层组装形式逐层喷涂到果蔬表面，使其先后产生三层保鲜膜，即为机械驱动力作用下的温度控释三层果蔬保鲜膜。
进一步的，步骤四中所述果蔬具体为球形果蔬，包括苹果、柑橘类、桃子、圣女果、西红柿、圆梨或圆茄子。
其中，所述温敏层溶液中温敏粒子链端的壳聚糖是聚阳离子，其结构中的氨基在溶液中容易发生质子化为-NH 3 +，带正电荷；形变中间层包含的海藻酸钠是聚阴离子，其结构中的羧基(-COOH)在溶液中形成大量-COO -，带负电荷，因此温敏内层和中间层的连接方式通过正负电荷间的静电作用力层层组装；所述形变中间层采用明胶和海藻酸钠水凝胶与所述刚性 外层的琼脂之间含有大量的氢键，而氢键可以提高两层膜之间的结合力；
所述形变中间层的ZnONPs，具有较高的导热系数，良好的热稳定性和抗菌性；所述刚性外层的TiO 2具有较高的导热系数，且对紫外线具有一定的抵御作用。
采用上述方案，本发明的有益效果：
(1)本发明的内层膜中CS-PNIPAM温敏粒子具有接近人体温度的低临界溶解温度(LCST)。内层温敏层可以响应温度变化，改变聚合物的构象，降低聚合物对精油的释放路径阻力，从而可有效改善果蔬在储藏到销售过程中因环境温度异常变化而导致的微生物快速生长问题。
(2)本发明的中间水凝胶层为膨胀层，可在环境温度发生改变后产生挤压应力并同时作用于刚性外层和温敏内层，而球型果蔬刚性外层具有较强的机械性能，会抵抗膨胀层带来的挤压应力，因此所有的形变力都会施加到温敏内层，最终表现为向心作用力。该向心作用力可以直接增大温敏粒子中精油的释放路径动力，有效加快精油的释放速率；且向心力的存在可以有效控制抗菌活性成分的释放路径方向，促使抗菌活性成分有效释放到果蔬表面，而非随机向外扩散释放。因此，最终本发明在控制抗菌活性成分释放路径方向的基础上，也能有效提高抗菌活性成分的释放路径动力，从而使得保鲜效果的最佳化。
(3)外层中TiO 2纳米粒子和中间层的ZnONPs纳米粒子均具有较好的导热系数，可以克服因多层膜厚造成温度响应不及时的缺陷，使得环境温度的变化迅速传递至内层膜，促进温敏内层膜的快速温度响应，及时应对因为外界环境温度变化而造成的果蔬加速腐败的问题。同时TiO 2还具有优异的抗紫外特性，可提高三层膜的光稳定性，进而保护活性成分的稳定性；中间层的ZnONPs还具有抗菌的特性，可以在没有外界温度刺激下直接对果蔬表面初始杀菌，从而进一步降低微生物对果蔬的侵染危害，延长果蔬自身的储藏期。
(4)本发明采用层层组装的成膜方式制备三层膜，通过内层膜中聚电解质阳离子和中间层膜中阴离子间的静电作用力有效提高两层膜间的吸附力；通过中间层膜的水凝胶聚合物与外层膜聚合物间的氢键作用力有效提高两层膜间的结合力。
附图说明
图1为本发明制备的控释三层果蔬保鲜膜的示意图。
图2为本发明的实施例1中的内层温敏粒子分别在25℃和37℃下的释放速率图。
图3中A为本发明的实施例2中的中间层保鲜膜在不同温度下的热膨胀率图；B为不添加ZnONPs的保鲜膜对比例在不同温度下的热膨胀率图。
图4中A为本发明的实施例3中外层膜的抗紫外屏障特性曲线图，B为不添加TiO 2对比例的抗紫外屏障曲线，其中插图a和b分别为实施例3和相应对比例的外层膜照片透过率 图。
图5为本发明的实施例3中内层膜和外层膜的zeta电位图。
具体实施方式
为使本发明的目的、技术方案和优点更加清楚明白，以下结合具体实施例，并结合附图，对本发明进一步详细说明。
实施例1：
一种机械驱动力作用下的温度控释抗菌三层膜制备方法，具体由内层、中间层和外层组装而成；其中内层为温敏层，可改变不同温度下聚合物对抗菌活性成分的释放路径阻力，从而宏观表现为抗菌活性成分的“开关”释放；中间层为形变层，具有热胀冷缩特性，会随着温度升高而膨胀，从而直接对内外层产生挤压应力；外层为刚性层(机械外层)，具有优良的机械性能，既能作为三层膜的阻隔层，又可为内层膜活性成分的释放提供向心驱动力。最终表现在控制抗菌活性成分释放路径方向的基础上，有效提高抗菌活性成分的释放路径动力，从而使得保鲜效果的最佳化。包括如下步骤：
步骤一、温敏内层溶液的制备；
S1.取1g壳聚糖溶于20mL体积浓度为的2％乙酸溶液中，然后加入1g的NIPAM单体并搅拌均匀，完全溶解后调整溶液温度为40℃加入0.2g硝酸铈铵(CAN)溶液作用引发剂，然后立即通氮气进行保护，反应24h后用丙酮沉淀析出得到粗产物，再通过100mL的甲醇进一步抽提得到细分物后，最后在25℃下的真空干燥箱中除去残余的有机溶液；即可得到CS-PNIPAM温敏粒子。
S2.将3g肉桂精油完全溶解于20mL体积浓度为50％的乙醇溶液中，得到混合溶液A备用；取1g步骤S1制备的温敏粒子完全溶解于100mL蒸馏水中，再将混合溶液A添加到温敏粒子分散溶液中，在18℃下充分反应吸附6h，然后经蒸馏水透析6h后去除未被包覆的游离肉桂精油，透析好的溶液即为装载有活性物质的温敏内层溶液。
为了进一步表征温敏内层溶液的温度敏感性，将内层溶液通过流延干燥法成膜，采用摇床法分别测试25℃和37℃下内层膜在0.1M的PBS缓冲溶液中的精油释放率，通过测试模拟液里的精油浓度进一步计算其累积释放率，结果如图2所示，在37℃下，温敏内层溶液的累积释放率明显更高。
步骤二、形变中间层溶液的制备；
取1g明胶和2g海藻酸钠溶于100mL蒸馏水中并在40℃下搅拌均匀，然后添加纳米氧化锌和甘油即可得到中间层水凝胶复合溶液，即为形变中间层溶液。其中，纳米氧化锌在水凝胶复合溶液中的质量浓度为0.01％，甘油在水凝胶复合溶液中的体积浓度为1％；所添加的纳 米氧化锌具有较高的导热系数，良好的热稳定性和抗菌性，可以及时将外界温度环境变化快速感知给内层膜，从而及时让内层膜的“开关”路径开启，降低释放路径阻力，快速释放活性物质；
步骤三、刚性外层溶液的制备；
取2g聚乙烯醇和0.5g琼脂溶于100mL蒸馏水中，在90℃下加热搅拌2h后，再添加二氧化钛和甘油，搅拌均匀后得到复合溶液，即为刚性外层溶液；其中氧化钛在复合溶液中的质量浓度为0.01％，甘油在复合溶液中的体积浓度为2％。
步骤四、层层组装的果蔬表面涂覆；
将温敏内层溶液、形变中间层溶液和刚性外层溶液通过喷雾式的层层组装形式依次喷涂到橙子表面，使其在橙子表面先后产生三层保鲜膜，由内到外分别为温敏内层、形变中间层和刚性外层，可用于橙子的保鲜。温敏层溶液中温敏粒子端的壳聚糖是聚阳离子，其结构中的氨基在溶液中容易发生质子化为-NH 3 +，带正电荷；形变中间层包含的海藻酸钠是聚阴离子，其结构中的羧基(-COOH)在溶液中形成大量-COO -，带负电荷，因此温敏内层和中间层膜的连接方式通过正负电荷间的静电作用力进行层层组装；而中间层的明胶和海藻酸钠水凝胶与外层膜的琼脂(凝胶)和聚乙烯醇之间含有大量的水合氢键，而氢键可以提高两层膜间的结合力，最终可使得三层保鲜膜互相之间结合牢固，可以更有效发挥三层膜各自的特定功能。
实施例2：
一种机械驱动力作用下的温度控释抗菌三层膜制备方法，具体由内层、中间层和外层组装而成。其中内层为温敏层，可改变不同温度下聚合物对抗菌活性成分的释放路径阻力，宏观表现为抗菌活性成分的“开关”释放；中间层为形变层，具有热胀冷缩特性，会随着温度升高而膨胀，从而直接对内外层产生挤压应力；外层为刚性层(机械外层)，具有优良的机械性能，既能作为三层膜的阻隔层，又可为内层膜活性成分的释放提供向心驱动力。最终表现在控制抗菌活性成分释放路径方向的基础上，有效提高抗菌活性成分的释放路径动力，使得保鲜效果的最佳化。包括如下步骤：
步骤一、温敏内层溶液的制备；
S1.取1.2g壳聚糖溶于20mL体积浓度为3％的乙酸溶液中，然后加入1gNIPAM单体搅拌均至完全溶解后，设定温度为45℃，加入0.2g硝酸铈铵(CAN)溶液作用引发剂，然后立即通氮气进行保护，反应36h后用二氯甲烷进行沉淀，析出后的粗产物再通过200mL甲醇进一步抽提得到细分物后，在30℃下的真空干燥箱中除去残余的有机溶液，即可得到CS-PNIPAM温敏粒子。
S2.将3g肉桂精油完全溶于15mL体积浓度为50％的乙醇溶液后备用；取上述步骤S1 制备的温敏粒子2g溶解于100mL蒸馏水，再将上述溶解好的精油添加到温敏粒子分散溶液中，在20℃下充分反应吸附7h后，经蒸馏水透析12h去除未被包覆的游离肉桂精油，获得透析好的溶液即为装载有活性物质的温敏内层溶液。
步骤二、形变中间层溶液的制备；
取1.5g明胶和2.5g海藻酸钠溶于100mL蒸馏水中并在50℃下搅拌均匀，然后添加ZnONPs和甘油即可得到中间层水凝胶复合溶液。其中，纳米氧化锌在水凝胶复合溶液中的质量浓度为0.03％，甘油在水凝胶复合溶液中的体积浓度为1.5％；所添加的纳米氧化锌具有较高的导热系数，良好的热稳定性和抗菌性，可以及时将外界温度环境变化快速感知给内层膜，从而及时让内层膜的“开关”路径开启，降低释放路径阻力，快速释放活性物质；
为了进一步验证形变中间层的膨胀特性，我们将中间层水凝胶复合溶液通过流延干燥法制备成膜。测试不同温度下，中间层保鲜膜在PBS缓冲液下的膨胀率。同时为了验证ZnONPs导热粒子的加入是否影响中间层的膨胀特性，本发明还设置了不添加ZnONPs的形变中间层溶液成膜，操作步骤与步骤二一致，区别仅在于不添加ZnONPs。结果如附图3所示，无论中间层保鲜膜是否添加氧化锌，其膨胀率都会随着温度的升高而增加，添加了氧化锌的实验组比空白组的热膨胀率还略高，这与氧化锌的高传热系数特性具有一致性，因此可以证明中间形变层会随着温度升高而膨胀。
步骤三、刚性外层溶液的制备；
取3g聚乙烯醇和1g琼脂溶于100mL蒸馏水，在95℃下加热搅拌1.5h后，再添加二氧化钛和甘油，搅拌均匀后得到复合溶液；其中二氧化钛在复合溶液中的质量浓度为0.03％，甘油在复合溶液中的体积浓度为3％。
步骤四、层层组装的果蔬表面涂覆；
将温敏内层溶液、形变中间层溶液和刚性外层溶液通过喷雾式的层层组装形式将多层膜溶液喷涂到苹果表面，使其先后产生三层保鲜膜，由内到外分别为温敏内层、形变中间层和刚性外层，可用于苹果的保鲜。温敏层溶液中温敏粒子端的壳聚糖是聚阳离子，其结构中的氨基在溶液中容易发生质子化为-NH 3 +，带正电荷；形变中间层包含的海藻酸钠是聚阴离子，其结构中的羧基(-COOH)在溶液中形成大量-COO -，带负电荷，因此温敏内层和中间层膜通过正负电荷间的静电作用力进行层层组装；而中间层的明胶和海藻酸钠水凝胶与外层膜的琼脂(凝胶)和聚乙烯醇之间含有大量的水合氢键，而氢键可以提高两层膜间的结合力，最终可使得三层保鲜膜互相之间结合牢固，可以更有效发挥三层膜各自的特定功能。
实施例3：
一种机械驱动力作用下的温度控释抗菌三层膜制备方法，具体由内层、中间层和外层组 装而成。其中内层为温敏层，可改变不同温度下聚合物对抗菌活性成分的释放路径阻力，宏观表现为抗菌活性成分的“开关”释放；中间层为形变层，具有热胀冷缩特性，会随着温度升高而膨胀，从而直接对内外层产生挤压应力；外层为刚性层(机械外层)，具有优良的机械性能，既能作为三层膜的阻隔层，又可为内层膜活性成分的释放提供向心驱动力。最终表现在控制抗菌活性成分释放路径方向的基础上，有效提高抗菌活性成分的释放路径动力，使得保鲜效果的最佳化。包括如下步骤：
步骤一、温敏内层溶液的制备；
S1.取3g壳聚糖溶于20mL 5％乙酸溶液中，然后加入0.6gNIPAM单体搅拌均匀至完全溶解后，设定温度为50℃，加入0.3g的硝酸铈铵(CAN)溶液作用引发剂，然后立即通氮气进行保护，反应48h后用三氯甲烷沉淀，析出后得到粗产物，再通过300mL甲醇进一步抽提得到细分物，在40℃下的真空干燥箱中除去残余的有机溶液；即可得到CS-PNIPAM温敏粒子。
S2.将3g肉桂精油完全溶于10mL浓度为50％的乙醇溶液中备用；取上述步骤S1制备的温敏粒子3g溶于100mL的蒸馏水，再将上述溶解好的精油添加到温敏粒子分散溶液中，在25℃下充分反应吸附8h，经蒸馏水透析18h后去除未被包覆的游离肉桂精油，获得透析好的溶液即为装载有活性物质的温敏内层溶液。
步骤二、形变中间层溶液的制备；
取2g明胶和4g海藻酸钠溶于100mL蒸馏水中并在60℃下搅拌均匀，添加纳米氧化锌和甘油后即可得到中间层水凝胶复合溶液。其中，纳米氧化锌在水凝胶复合溶液中的质量浓度为0.02％，甘油在水凝胶复合溶液中的体积浓度为2％；所添加的纳米氧化锌具有较高的导热系数，良好的热稳定性和抗菌性，可以及时将外界温度环境变化快速感知给内层膜，从而及时让内层膜的“开关”路径开启，降低释放路径阻力，快速释放活性物质；
步骤三、刚性外层溶液的制备；
取4g聚乙烯醇和2g琼脂溶于100mL蒸馏水并在100℃下加热搅拌1h后，再添加的二氧化钛和的甘油，搅拌均匀后得到复合溶液；其中二氧化钛在复合溶液中的质量浓度为0.05％，甘油在复合溶液中的体积浓度为4％。
为了进一步验证TiO 2的紫外屏障性，我们将外层溶液通过流延干燥法成膜；同时设置了不添加二氧化钛的流延膜作为空白对比例，操作步骤与步骤三一致，区别仅在于不添加TiO 2，比较二氧化钛添加前后外层膜的紫外吸收特性，结果如附图4所示，添加了TiO 2的外层膜具有较高的吸光度，且如图4插图外层膜的照片所示，明显发现添加TiO 2的外层保鲜膜具有较低的光透过率，且在紫外区有明显的峰值变化，从而验证了外层膜的紫外屏障特性。
步骤四、层层组装的果蔬表面涂覆；
将温敏内层溶液、形变中间层溶液和刚性外层溶液通过喷雾式的层层组装形式将多层膜溶液喷涂到圣女果表面，使其在圣女果表面先后产生三层保鲜膜，由内到外分别为温敏内层、形变中间层和刚性外层，可用于圣女果的保鲜。温敏层溶液中温敏粒子端的壳聚糖是聚阳离子，其结构中的氨基在溶液中容易发生质子化为-NH 3 +，带正电荷；形变中间层包含的海藻酸钠是聚阴离子，其结构中的羧基(-COOH)在溶液中形成大量-COO -，带负电荷，因此温敏内层和中间层膜通过正负电荷间的静电作用力进行层层组装；而中间层的明胶和海藻酸钠水凝胶与外层膜的琼脂(凝胶)和聚乙烯醇之间含有大量的水合氢键，而氢键可以提高两层膜间的结合力，最终可使得三层保鲜膜互相之间结合牢固，可以更有效发挥三层膜各自的特定功能。
为了进一步表征内层温敏层溶液和中间层溶液的聚电性质，对两种溶液的Zeta电位进行了表征。结果如附图5所示，温敏内层因为包含壳聚糖聚阳离子，其Zeta电位值为正数，为21.65mV；而形变中间层包含海藻酸钠聚阴离子，其Zeta电位值为负数，为25.15mV。
最后还比较了温敏内层溶液、形变中间层溶液和刚性外层溶液通过流延干燥法制备成膜后的机械性能，以实施例3为例，表1结果验证刚性外层膜具有较高的机械特性，进一步证明了其可以作为形变中间层的抵抗力，增加了抗菌剂释放的路径动力，最终可以增加精油的有效释放速率。
表1 三层膜的机械性能结果
Figure PCTCN2022077358-appb-000001
注:同一列上标字母相同的数据表示差异有统计学意义(p<0.05).式中:TS:抗拉强度；EB:断裂伸长率；
说明：以上实施例仅用以说明本发明而并非限制本发明所描述的技术方案；因此，尽管本说明书参照上述的各个实施例对本发明已进行了详细的说明，但是本领域的普通技术人员应当理解，仍然可以对本发明进行修改或等同替换；而一切不脱离本发明的精神和范围的技术方案及其改进，其均应涵盖在本发明的权利要求范围内。

Claims (10)

  1. 一种机械驱动力作用下的温度控释三层果蔬保鲜膜制备方法，其特征在于，包括以下步骤：
    步骤一、温敏内层溶液的制备；
    S1.温敏粒子的制备：取壳聚糖溶于乙酸溶液中，然后加入单体N-异丙基丙烯酰胺并搅拌均匀，将得到的溶液调整至一定温度后再加入硝酸铈铵溶液，然后通氮气保护，在反应一段时间后的混合溶液中加入有机溶剂进行沉淀析出得到粗产物，再经抽提得到细分物，然后经干燥后得到终产物，即为CS-PNIPAM温敏粒子；
    S2.温敏内层溶液的制备：取精油溶于乙醇溶液中得到混合溶液A；再将步骤S1制备的温敏粒子溶解在蒸馏水中配制成一定质量浓度的温敏粒子分散液；然后将混合溶液A添加到温敏粒子分散液中得到混合溶液B，在一定温度条件下反应后，再将混合溶液B经蒸馏水进行透析，获得透析后的溶液即为装载有活性物质的温敏内层溶液；
    步骤二、形变中间层溶液的制备；
    将明胶和海藻酸钠溶于蒸馏水中，并在一定温度条件下搅拌均匀，然后添加的纳米氧化锌和甘油，得到水凝胶复合溶液，即为形变中间层溶液；
    步骤三、刚性外层溶液的制备；
    取聚乙烯醇和琼脂溶于蒸馏水中，加热至一定温度搅拌后，再添加纳米二氧化钛和甘油，搅拌均匀后得到复合溶液，即为刚性外层溶液：
    步骤四、层层组装的果蔬表面涂覆；
    将温敏型内层溶液、形变中间层溶液和刚性外层溶液通过喷雾式的层层组装形式逐层喷涂到果蔬表面，使其先后产生三层保鲜膜，即为机械驱动力作用下的温度控释三层果蔬保鲜膜。
  2. 根据权利要求1所述的机械驱动力作用下的温度控释三层果蔬保鲜膜制备方法，其特征在于，步骤S1中所述壳聚糖、单体N-异丙基丙烯酰胺、硝酸铈铵和乙酸溶液的用量比为5～10g:5～2g:1g:20～50mL；所述乙酸溶液的体积浓度为2％～5％；所述调整至一定温度为40～50℃；所述反应一段时间为24～48h。
  3. 根据权利要求1所述的机械驱动力作用下的温度控释三层果蔬保鲜膜制备方法，其特征在于，步骤S1中所述有机溶液为丙酮、二氯甲烷、三氯甲烷、N-N二甲基乙酰胺、乙酸乙酯、或者二氢呋喃的任意一种或者多种任意比例的复合溶液；所述混合溶液与有机溶剂的体积比为1:5-15；所述干燥的温度为25～40℃。
  4. 根据权利要求1所述的机械驱动力作用下的温度控释三层果蔬保鲜膜制备方法，其特征在于，步骤S2中所述精油为牛至精油、肉桂精油、按叶精油、丁香精油或百里香精油中的 任意一种；所述乙醇溶液的体积浓度为50％；所述混合溶液A中精油的质量浓度为1.5％～3％。
  5. 根据权利要求1所述的机械驱动力作用下的温度控释三层果蔬保鲜膜制备方法，步骤S2中所述温敏粒子分散液的质量浓度为1～3g/mL；所述混合溶液A添加到温敏粒子分散液中，两者的体积比为1：5～10；所述一定温度条件下反应的温度为18～25℃，时间为6～8h；所述透析的时间为6～18h。
  6. 根据权利要求1所述的机械驱动力作用下的温度控释三层果蔬保鲜膜制备方法，其特征在于，步骤二中所述明胶、海藻酸钠和蒸馏水的用量比为1～2g:2～4g:100mL；所述一定温度条件为40～60℃；所述纳米氧化锌在水凝胶复合溶液中的质量浓度为0.01～0.03％；所述甘油在水凝胶复合溶液中的体积浓度为1～2％。
  7. 根据权利要求1所述的机械驱动力作用下的温度控释三层果蔬保鲜膜制备方法，其特征在于，步骤三中所述聚乙烯醇、琼脂、蒸馏水的用量比为2～4g:0.5～2g:100mL；所述加热至一定温度为90～100℃，搅拌的时间为1～2h；所述二氧化钛在复合溶液中的质量浓度为0.01～0.05％，所述甘油在复合溶液中的体积浓度为1～4％。
  8. 根据权利要求1所述的机械驱动力作用下的温度控释三层果蔬保鲜膜制备方法，其特征在于，步骤四中所述果蔬具体为球形果蔬，包括苹果、柑橘类、桃子、圣女果、西红柿、圆梨或圆茄子。
  9. 一种根据权利要求1～8任一项所述方法制备的机械驱动力作用下的温度控释三层果蔬保鲜膜，其特征在于，所述温度控释三层果蔬保鲜膜由内到外依次为温敏内层、形变中间层和机械外层。
  10. 根据权利要求9所述的机械驱动力作用下的温度控释三层果蔬保鲜膜用于果蔬保鲜的用途。
PCT/CN2022/077358 2022-02-16 2022-02-23 一种机械驱动力作用下的温度控释三层果蔬保鲜膜及其制备方法 WO2023155217A1 (zh)

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