阅读说明：本技术 一种防迁移水凝胶基新鲜度比色指示标签及其制备方法 (Migration-resistant hydrogel-based freshness colorimetric indication label and preparation method thereof ) 是由 安宁丽 方长青 薛文娜 秦靖萱 马利娥 姜涛 于 2021-10-08 设计创作，主要内容包括：本发明公开了一种防迁移水凝胶基新鲜度比色指示标签及其制备方法,属于食品智能包装技术领域。包括透明包装盒盖、海藻酸钠-指示剂复合薄膜、支架和PVDF多孔薄膜,PVDF多孔薄膜一面亲水一面疏水,小孔亲水测牢固贴合亲水的海藻酸钠指示剂层,大孔疏水侧直接接触包装物内部环境,将生物胶制备成水凝胶固体基体负载染料,提供良好的离子通道,提高了染料的化学响应速度。然而水凝胶通常易溶胀使得染料析出,对智能标签的稳定性造成不良影响,利用本发明方法能够得到具有显色响应快、透气疏水的抗菌智能标签。(The invention discloses an anti-migration hydrogel based freshness colorimetric indication label and a preparation method thereof, and belongs to the technical field of intelligent food packaging. The hydrogel solid matrix load dye is prepared from the biogel, provides a good ion channel, and improves the chemical response speed of the dye. However, the hydrogel is usually easy to swell so that the dye is separated out, the stability of the intelligent label is adversely affected, and the antibacterial intelligent label with quick chromogenic response, air permeability and hydrophobicity can be obtained by using the method provided by the invention.)

1. An anti-migration hydrogel-based freshness colorimetric indication label is characterized by comprising a transparent packaging box cover (1), a sodium alginate-indicator composite film (2), a bracket (3) and a PVDF porous film (4);

the support (3) is arranged at the outer edge of the upper surface of the transparent packaging box cover (1), the sodium alginate-indicator composite film (2) is assembled on the upper surface of the transparent packaging box cover (1) and is positioned inside the support (3), and the PVDF porous film (4) is positioned on the upper surface of the sodium alginate-indicator composite film (2);

the height of the sodium alginate-indicator composite film (2) is the same as that of the bracket (3).

2. The anti-migration hydrogel-based freshness colorimetric indication label according to claim 1, wherein the PVDF porous film (4) is of a sponge structure, the sponge structure further comprises a plurality of conical through holes inside, and each conical through hole is arranged along a vertical direction;

one end of the conical through hole is provided with a large hole, the other end of the conical through hole is provided with a small hole, the small hole is positioned on the lower surface of the PVDF porous film (4) and is contacted with the sodium alginate-indicator composite film (2), and the large hole is positioned on the upper surface of the PVDF porous film (4).

3. A method of making the anti-migration hydrogel-based freshness colorimetric indicator label of claim 1 or 2, comprising the steps of:

step 1) mixing PVDF powder, an additive and a solvent, adding silver nitrate after heating reaction, and stirring for reaction to obtain a casting solution;

step 2) standing the casting solution, performing reverse phase film formation, and drying to obtain a PVDF porous film (4);

step 3) mixing sodium alginate, plasticizer and deionized water to obtain a mixed solution, adding an indicator into the mixed solution to obtain an indicating solution, and placing the indicating solution in CaCL₂Performing cross-linking reaction in the solution to obtain a sodium alginate-indicator composite film (2);

step 4), uniformly coating GG glue solution on the transparent packaging box cover (1) to obtain a support (3);

and 5) encapsulating the sodium alginate-indicator composite film (2) in the support (3), and encapsulating the PVDF porous film (4) on the upper surface of the sodium alginate-indicator composite film (2).

4. The preparation method of the migration-proof hydrogel-based freshness colorimetric indication label according to claim 3, wherein the additive is any one of polyvinylpyrrolidone, polyethylene glycol, polymethyl methacrylate, titanium dioxide, silicon dioxide, and cyanoethyl cellulose;

the solvent is DMF;

the plasticizer is glycerol;

the indicator is a biological indicator, bromothymol blue or methyl red;

the biological indicator is anthocyanin, alizarin or curcumin.

5. The preparation method of the anti-migration hydrogel-based freshness colorimetric indicator label according to claim 4, wherein when the indicator is a biological indicator, the mass percentage of the indicator in the indicator solution is 1-5%;

when the indicator is bromothymol blue or methyl red, the mass percentage of the indicator in the indicating solution is 0.1-0.2%.

6. The preparation method of the anti-migration hydrogel-based freshness colorimetric indication label according to claim 3, wherein the mass fraction of PVDF in the casting solution is 6-10%;

the mass ratio of the additive to PVDF is (10-30): 100, respectively;

the mass ratio of the sodium alginate to the plasticizer is 5: (0.1 to 1).

7. The preparation method of the anti-migration hydrogel based freshness colorimetric indication label according to claim 3, wherein the mass percentage of the GG gel solution is 1-3%.

8. The preparation method of the anti-migration hydrogel-based freshness colorimetric indicator label according to claim 3, wherein the heating reaction condition in the step 1) is heating at 50-60 ℃ for 12 hours.

Technical Field

The invention belongs to the technical field of intelligent food packaging, and relates to an anti-migration hydrogel-based freshness colorimetric indication label and a preparation method thereof.

Background

Fresh food is easily affected by physical, chemical and biological aspects in the processes of transportation, sale and storage, and is slightly decayed, so that the quality of the product is affected. The traditional package can not monitor the quality change of the product in real time, which causes the waste of the product. Therefore, the problem which is urgently solved in the field of intelligent packaging is that the change of the food quality and state is visually monitored and detected. Factors such as how to balance functions, sizes and preparation cost of the sensor are technical limits of application of the intelligent indicator label for realizing visual food freshness in packaged products.

The colorimetric sensor is a solution for realizing visualization of food freshness parameters simply, efficiently and at low cost. Colorimetric sensors are typically constructed of two parts, a solid substrate and a chemical/biological dye supported on the solid substrate. By correlating the color change of the chemically responsive dye with the freshness and spoilage of the food product.

The current research for solid matrix materials has mainly focused on polyvinyl alcohol, polysaccharides (cellulose, biogum, chitosan, etc.) and protein degradable materials. Dyes are directly incorporated into these solid substrates by hydrogen bonding or ionic reactions. The hydrogen bond between polysaccharide and anthocyanin plays a stabilizing role in anthocyanin. The biological glue is a natural polysaccharide biological material and has the characteristics of environmental friendliness, unique optical performance, good rheological property and the like. The biological gel is prepared into hydrogel solid matrix loaded with dye, so that a good ion channel is provided, and the chemical response speed of the dye is improved. However, hydrogels are generally very swelling, which causes dyes to precipitate, which adversely affects the stability of the smart tag.

PVDF is a material with biocompatibility, easy processing, polarity and stable performance. PVDF can be prepared into specific porous materials through process regulation. The Ag nano-particle composite PVDF porous material, the sodium alginate and other materials have the antibacterial effect.

Disclosure of Invention

In order to overcome the defect that the freshness indication label in the prior art cannot develop color due to dissolution failure of an indicator caused by the fact that the freshness indication label is poor in hydrophobicity and easy to absorb water, the invention aims to provide a hydrophilic-hydrophobic PVDF freshness indication label and a preparation method thereof.

In order to achieve the purpose, the invention adopts the following technical scheme to realize the purpose:

a migration-proof hydrogel-based freshness colorimetric indication label comprises a transparent packaging box cover, a sodium alginate-indicator composite film, a bracket and a PVDF porous film;

the support is arranged at the outer edge of the upper surface of the transparent packaging box cover, the sodium alginate-indicator composite film is assembled on the upper surface of the transparent packaging box cover and is positioned inside the support, and the PVDF porous film is positioned on the upper surface of the sodium alginate-indicator composite film;

the height of the sodium alginate-indicator composite film is the same as that of the bracket.

Preferably, the PVDF porous film is of a sponge structure, the sponge structure further comprises a plurality of conical through holes inside, each conical through hole is arranged along the vertical direction,

one end of the conical through hole is provided with a large hole, the other end of the conical through hole is provided with a small hole, the small hole is positioned on the lower surface of the PVDF porous film and is in contact with the sodium alginate-indicator composite film, and the large hole is positioned on the upper surface of the PVDF porous film.

A preparation method of the migration-proof hydrogel based freshness colorimetric indication label comprises the following steps:

step 1) mixing PVDF powder, an additive and a solvent, adding silver nitrate after heating reaction, and stirring for reaction to obtain a casting solution;

step 2) standing the casting solution, performing reverse phase film formation, and drying to obtain a PVDF porous film;

step 3) mixing sodium alginate, plasticizer and deionized water to obtain a mixed solution, adding an indicator into the mixed solution to obtain an indicating solution, and placing the indicating solution in CaCL₂Performing crosslinking reaction in the solution to obtain a sodium alginate-indicator composite film;

step 4), uniformly coating the GG glue solution on a transparent packaging box cover to obtain a support;

and 5) encapsulating the sodium alginate-indicator composite film in the bracket, and encapsulating the PVDF porous film on the upper surface of the sodium alginate-indicator composite film.

Preferably, the additive is any one of polyvinylpyrrolidone, polyethylene glycol, polymethyl methacrylate, titanium dioxide, silicon dioxide and cyanoethyl cellulose;

the solvent is DMF;

the plasticizer is glycerol;

the indicator is a biological indicator, bromothymol blue or methyl red;

the biological indicator is anthocyanin, alizarin or curcumin.

Preferably, when the indicator is a biological indicator, the mass percentage of the indicator in the indicating solution is 1-5%;

when the indicator is bromothymol blue or methyl red, the mass percentage of the indicator in the indicating solution is 0.1-0.2%.

Preferably, the mass fraction of PVDF in the casting solution is 6-10 wt%;

the mass ratio of the additive to PVDF is (10-30): 100, respectively;

the mass ratio of the sodium alginate to the plasticizer is 5: (0.1 to 1);

preferably, the GG glue solution is 1-3% by mass.

Preferably, the heating reaction condition of the step 1) is heating for 50-60 ℃ for 12 h.

Compared with the prior art, the invention has the following beneficial effects:

the invention discloses a hydrophilic-hydrophobic PVDF freshness indication label, which comprises a transparent packaging box cover, a sodium alginate-indicator composite film, a bracket and a PVDF porous film, wherein one surface of the PVDF porous film is hydrophilic and the other surface is hydrophobic, a hydrophilic sodium alginate indicator layer is firmly attached to a hydrophilic pore hydrophilic side, and the hydrophobic side of a macropore is directly contacted with the internal environment of a packaging material, so that the antibacterial intelligent label with quick chromogenic response, air permeability and hydrophobicity is obtained.

The invention also discloses a preparation method of the hydrophilic-hydrophobic PVDF freshness indication label, which prepares the biogel into hydrogel solid matrix loaded dye, provides a good ion channel and improves the chemical response speed of the dye. However, hydrogels are generally very swelling, which causes dyes to precipitate, which adversely affects the stability of the smart tag. PVDF is a material with biocompatibility, easy processing, polarity and stable performance. PVDF can be prepared into a specific porous material through process regulation, and specifically, a certain amount of pore-forming agent is added into PVDF membrane casting solution, uniformly stirred, spread on a hydrophobic substrate, placed into a coagulating bath together with the substrate for reverse phase film formation, taken out, dried and demoulded to obtain a regularly-arranged tapered-pore spongy porous structure film.

Drawings

FIG. 1 is a schematic representation of a porous PVDF membrane;

FIG. 2 is a schematic view of a sodium alginate indicator layer poured on a package box;

FIG. 3 is a schematic view of a package box spin-on adhesive poured with a sodium alginate indicator layer;

FIG. 4 is a schematic structural view of a porous PVDF film sealed and adhered to a packaging box poured with a sodium alginate indicator layer and an adhesive;

FIG. 5 is an SEM image of a PVDF porous membrane, which is a through hole section (a), an upper surface (b) and a lower surface (c) in this order;

FIG. 6 is a graph showing contact angles of the upper surface (a) and the lower surface (b) of a PVDF porous membrane;

FIG. 7 is a stress-strain curve of a PVDF porous film.

Wherein: 1-transparent packing box cover; 2-sodium alginate-indicator composite film; 3-a scaffold; 4-PVDF porous film.

Detailed Description

The invention is described in further detail below with reference to the accompanying drawings:

the first embodiment is as follows:

the preparation method of the PVDF hydrophilic-hydrophobic film/biological hydrogel double-layer colorimetric type intelligent label in the experimental mode comprises the following steps: the assembly is performed according to the flow structure as shown in figures 2, 3 and 4,

firstly, dissolving 3.6g of PVDF in 55.8g of DMF solvent to obtain a membrane casting solution;

secondly, 0.6g of PVP is weighed and dissolved in the membrane casting solution obtained in the first step;

thirdly, measuring 2ml AgNO₃Slowly dripping into the solution in the second step, and ultrasonically stirring for 12h under the conditions that the rotating speed is 400r/min, the heating temperature is 50 ℃ and the power is 100%;

fourthly, standing the casting film liquid chamber, pouring the casting film liquid chamber into a polytetrafluoroethylene hydrophobic mold, uniformly spreading the casting film liquid chamber, putting the casting film liquid chamber and the casting film liquid chamber into a deionized water coagulating bath at 50 ℃ together for reverse phase film forming, taking out the casting film liquid chamber, and performing vacuum drying at 50 ℃ for 8 hours to obtain the PVDF porous antibacterial film;

fifthly, 3.6g of sodium alginate and 0.48g of glycerol are weighed and dissolved in 60ml of deionized water, and the mixture is stirred at the temperature of 35 ℃ until the mixture is dissolved;

sixthly, mixing 0.2% methyl red and 0.1% bromothymol blue solution 1: 1 to obtain a mixed indicator, adding 0.1ml of the mixed indicator into the fifth step to obtain an indicating solution, spreading the indicating solution on the porous membrane obtained in the fourth step, and using 5% w/vCaCl₂Crosslinking for 5min in the solution to obtain a double-layer indicating label;

seventhly, weighing 3% of gellan gum (GG gum) and dissolving in deionized water to be uniformly stirred to obtain a bracket;

and eighthly, assembling the double-layer indicating label obtained in the step six and the bracket obtained in the step seven on the surface of the transparent plastic packaging box.

Example two

The difference between the embodiment and the embodiment one is that the additive added in the step two is PMMA, and the mass ratio of PMMA to PVDF is 2.5: 10, the mass ratio of sodium alginate to glycerol is 5: 0.1, the temperature of the coagulation bath in the fourth step is room temperature, the mass fraction of PVDF in the casting solution is 10%, and the mass percentage of GG gel solution is 2.5%, and the rest is the same as that of the first embodiment.

EXAMPLE III

The difference between the embodiment and the embodiment one is that the additive added in the step two is PEG, and the mass ratio of the PEG to the PVDF is 1.5: 10, the mass ratio of sodium alginate to glycerol is 5: 1, heating the third step to 60 ℃, wherein the mass fraction of PVDF in the casting solution is 7%, the mass fraction of GG colloidal solution is 1.5%, and the GG colloidal solution is prepared by heating at 60 ℃, and the rest is the same as the first step in the example.

Example four

The difference between the embodiment and the embodiment one is that the additive added in the step two is titanium dioxide, and the mass ratio of the titanium dioxide to the PVDF is 2: 10, the mass ratio of sodium alginate to glycerol is 5: 0.3, the glycerol amount added in the step five is 0.3g, the mass fraction of PVDF in the membrane casting solution is 8%, the mass fraction of GG gum solution is 3%, and the GG gum solution is prepared by heating at 100 ℃, and the rest is the same as the embodiment one.

EXAMPLE five

The difference between the embodiment and the embodiment one is that the additive added in the step two is silicon dioxide, and the mass ratio of the silicon dioxide to the PVDF is 1: 10, the mass ratio of sodium alginate to glycerol is 5: 0.5, the amount of the mixed indicator in the sixth step is 0.2ml, the mass fraction of PVDF in the casting solution is 9%, the mass fraction of GG gum solution is 2%, and the GG gum solution is prepared by heating at 80 ℃, and the rest is the same as that in the first embodiment.

EXAMPLE six

The difference between the embodiment and the embodiment one is that the additive added in the step two is CEC, the mass ratio of CEC to PVDF is 3: 10, the mass ratio of sodium alginate to glycerol is 5: 0.8, the amount of the gellan gum in the step seven is 1%, the mass fraction of PVDF in the casting solution is 6.5%, the mass fraction of GG gum solution is 1%, and the GG gum solution is prepared by heating at 90 ℃, and the other steps are the same as those in the first embodiment.

The migration-proof hydrogel-based freshness colorimetric indication label prepared by the method comprises a transparent packaging box cover 1, a sodium alginate-indicator composite film 2, a bracket 3 and a PVDF porous film 4; the bracket 3 is arranged at the outer edge of the upper surface of the transparent packaging box cover 1, the sodium alginate-indicator composite film 2 is assembled on the upper surface of the transparent packaging box cover 1 and is positioned inside the bracket 3, and the PVDF porous film 4 is positioned on the upper surface of the sodium alginate-indicator composite film 2; the height of the sodium alginate-indicator composite film 2 is the same as that of the bracket 3.

The PVDF porous film 4 is of a sponge structure, a plurality of conical through holes are further arranged inside the sponge structure, each conical through hole is arranged in the vertical direction, one end of each conical through hole is a large hole, the other end of each conical through hole is a small hole, the small holes are located on the lower surface of the PVDF porous film 4 and are in contact with the sodium alginate-indicator composite film 2, and the large holes are located on the upper surface of the PVDF porous film 4.

The prepared PVDF porous film is shown in fig. 1, and SEM characterization of the PVDF porous film prepared in example 1 is performed, and the result is shown in fig. 5, from which it can be seen that tapered pores and sponge-like pores can be seen in the cross-sectional structure in fig. 5a, fig. 5b is a uniform small pore structure on the upper surface, and fig. 5c is a uniform large pore structure on the lower surface. Adding a pore-forming agent and blending with PVDF to obtain a casting solution, and performing reverse phase drying film formation by a tape casting method to obtain the porous film with special hydrophilicity and hydrophobicity. The successful fabrication of tapered pore structures can be seen by cross-sectional and top and bottom surface views. The contact angles of the upper surface and the lower surface of the PVDF porous film prepared in example 1 are detected, and the result is shown in fig. 6, where fig. 6a is a hydrophilic upper surface, fig. 6b is a hydrophobic lower surface, and the result of electron microscope images shows that the upper surface has a small pore structure to obtain hydrophilic performance, and the lower surface has a large pore structure to obtain hydrophobic performance. The strain properties of the PVDF porous film prepared in example 1 were investigated, and the results are shown in fig. 7, which shows that the mechanical properties of the film are excellent.

The above-mentioned contents are only for illustrating the technical idea of the present invention, and the protection scope of the present invention is not limited thereby, and any modification made on the basis of the technical idea of the present invention falls within the protection scope of the claims of the present invention.