Biogenic amine response type intelligent food packaging material based on Co-MOF / ortho-dihydroxy compound and preparation method of biogenic amine response type intelligent food packaging material

Abstract

The invention discloses a biogenic amine response type intelligent food packaging material based on a Co-MOF / ortho-dihydroxy compound and a preparation method of the biogenic amine response type intelligent food packaging material, and belongs to the technical field of new food packaging materials. The biogenic amine response type intelligent food packaging material based on the Co-MOF / ortho-dihydroxy compound is prepared from the following raw materials: 80 to 90 parts of starch, 10 to 20 parts of hydrophilic colloid, 35 to 40 parts of plasticizer, 1 to 5 parts of Co-MOF material and 1 to 10 parts of ortho-dihydroxy compound. The biogenic amine response type intelligent food packaging material is prepared through a solution casting method, and production is efficient and stable. The biogenic amine response type intelligent food packaging material has excellent biogenic amine response performance, antibacterial performance and mechanical performance, the storage period of food can be remarkably prolonged, and the function of intelligently indicating the freshness of the food is achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of new food packaging materials, and in particular to a biogenic amine-responsive intelligent food packaging material based on Co-MOF / ortho-dihydroxy compounds and a preparation method thereof. Background Art

[0002] As an emerging technology in the packaging field, smart packaging has broad application prospects. Among them, monitoring-sensing smart packaging can introduce monitoring systems into the food supply chain, sensing environmental changes inside and outside the packaging in real time. When meat begins to spoil, the protein, under the action of microorganisms, produces a variety of biogenic amines, such as ammonia, trimethylamine, and dimethylamine. These volatile biogenic amines are called total volatile basic nitrogen (TVB-N) and are important physical and chemical indicators for assessing the freshness of meat. Generally, an increase in TVB-N levels will gradually turn the environment inside the package into an alkaline one. Monitoring-sensing smart packaging, which is highly sensitive to volatile biogenic amines, is expected to achieve real-time, non-destructive, and dynamic monitoring of meat product quality.

[0003] Among the existing technologies, the Chinese invention patent with application number 202111592359.9 uses the self-assembly of Artemisia selengensis gum-soy protein isolate to achieve rapid response of monitoring-sensing smart packaging containing anthocyanins; the Chinese invention patent with application number 202410746586.X uses the co-coloring effect of chitosan quaternary ammonium salt and anthocyanins to improve the response performance of starch / anthocyanin composite film; the Chinese invention patent with application number 202211608639.9 uses a layer-by-layer casting method to prepare a double-layer smart packaging film covered with a beeswax hydrophobic layer. However, the above-mentioned technology is still based on the development of monitoring-sensing smart packaging based on anthocyanins, which has great limitations and cannot simultaneously overcome the many shortcomings of natural pigments such as poor light / heat stability, easy migration, low response sensitivity, and high detection limit, making it difficult to meet the needs of actual applications. In view of this, it is indeed necessary to provide a new technical solution to overcome the many problems existing in the existing technology. Summary of the Invention

[0004] The present invention aims to provide a biogenic amine-responsive smart food packaging material based on Co-MOF / ortho-dihydroxy compounds and a method for preparing the same, in order to address the aforementioned problems in the prior art. The present invention creatively uses Co-MOF and ortho-dihydroxy compounds as mixed indicators, replacing traditional natural pigment indicators, to achieve a rapid, stable, and highly sensitive response to volatile biogenic amines. During use, the biogenic amine-responsive smart food packaging material of the present invention exhibits excellent mechanical properties, high antibacterial properties, and a low detection limit, effectively preventing monitoring failure and cross-contamination.

[0005] To achieve the above object, the present invention provides the following solutions:

[0006] One of the technical solutions of the present invention: a biogenic amine-responsive smart food packaging material based on Co-MOF / ortho-dihydroxy compound, wherein the raw materials include, by weight, 80 to 90 parts of starch, 10 to 20 parts of hydrophilic colloid, 35 to 40 parts of plasticizer, 1 to 5 parts of Co-MOF material and 1 to 10 parts of ortho-dihydroxy compound.

[0007] The Co ions in Co-MOF can form hydrogen bonds between Co-O groups and ammonia molecules, causing their coordination environment to change, thereby causing color changes, allowing Co-MOF to produce hue changes under an ammonia environment; the phenolic hydroxyl structure in the ortho-dihydroxy compound is easily combined with the ammonia molecule under an ammonia environment and oxidized to cause its structure to change, thereby causing a change in its own color; and the unique molecular structure of the ortho-dihydroxy compound can also chelate Co ions, thereby increasing the degree of change in the Co-MOF coordination environment, producing a co-coloring effect with Co-MOF, causing a more significant hue change, and achieving visual recognition and sensitive response to volatile ammonia. Therefore, the present invention uses Co-MOF and ortho-dihydroxy compounds as mixed indicators, replacing traditional natural pigment indicators, and achieving a fast, stable, and highly sensitive response to volatile biogenic amines.

[0008] Furthermore, Co-MOF can exert a synergistic antibacterial effect with ortho-dihydroxy compounds, making the Co-MOF / ortho-dihydroxy compound-based biogenic amine-responsive smart food packaging material of the present invention also possess excellent antiseptic and mildew resistance. In summary, the present invention uses Co-MOF and ortho-dihydroxy compounds as active components to simultaneously achieve multifunctional label freshness indication, antiseptic properties, and mildew resistance. This means it possesses the dual functional properties of "self-cleaning" and "ammonia response."

[0009] Furthermore, the preparation steps of the Co-MOF material include:

[0010] A Co-MOF stock solution is prepared using a cobalt source, lauric acid and trimesic acid as raw materials; the Co-MOF stock solution is centrifuged, and the obtained precipitate is crystallized under heating conditions to obtain the Co-MOF material.

[0011] Furthermore, the preparation of the Co-MOF stock solution using a cobalt source, lauric acid and trimesic acid as raw materials includes: mixing the cobalt source, lauric acid and solvent 1 to obtain a mixed solution; mixing trimesic acid and solvent 2 to obtain a trimesic acid solution; and mixing the mixed solution with the trimesic acid solution to obtain the Co-MOF stock solution.

[0012] Furthermore, the cobalt source includes cobalt acetate tetrahydrate.

[0013] Furthermore, the solvent 1 includes ethanol.

[0014] Furthermore, the mass ratio of the cobalt source to the lauric acid is 1:5-7.

[0015] Furthermore, the ratio of the sum of the masses of the cobalt source and the lauric acid to the volume of the solvent 1 is 1 g:90-100 mL.

[0016] Furthermore, the solvent 2 includes N,N-dimethylformamide.

[0017] Furthermore, the mass volume ratio of the trimesic acid to the solvent 2 is 1 g:650-700 mL.

[0018] Furthermore, the volume ratio of the mixed solution to the trimesic acid solution is 1:1.

[0019] Furthermore, the method further includes washing the obtained precipitate before crystallizing the obtained precipitate under heating conditions.

[0020] Furthermore, the heating temperature is 50-55°C.

[0021] Furthermore, the crystallization is carried out under light-proof conditions.

[0022] Furthermore, the crystallization time is 10-12 hours.

[0023] Furthermore, the Co-MOF material has a hexahedral microstructure and a size of 200 to 1000 nm.

[0024] Furthermore, the starch includes one or more of cassava starch, acid-hydrolyzed cassava starch, oxidized cassava starch, hydroxypropyl distarch phosphate and octenyl succinic anhydride modified starch.

[0025] Furthermore, the hydrophilic colloid includes one or more of agar, sodium alginate, xanthan gum, carrageenan, sodium carboxymethyl cellulose and polyvinyl alcohol.

[0026] Furthermore, the plasticizer includes glycerol.

[0027] Furthermore, the vicinal dihydroxy compound includes one or more of catechin, gallic acid, caffeic acid, ferulic acid, chlorogenic acid, epigallocatechin gallate and tannic acid.

[0028] The second technical solution of the present invention is a method for preparing the above-mentioned biogenic amine-responsive smart food packaging material based on Co-MOF / ortho-dihydroxy compound, comprising the following steps:

[0029] The starch is mixed with the hydrophilic colloid and water, and after heating and stirring, the plasticizer, the Co-MOF material and the ortho-dihydroxy compound are added and continued to heat and stir to obtain a film-forming liquid; the film-forming liquid is prepared into a film to obtain the Co-MOF / ortho-dihydroxy compound-based biogenic amine-responsive smart food packaging material.

[0030] Furthermore, the ratio of the sum of the masses of the starch and the hydrophilic colloid to the volume of the water is 3g:100mL.

[0031] Furthermore, the heating and stirring are performed at a temperature of 90-100° C. and for a time of 30-40 minutes.

[0032] Furthermore, the step of preparing the film-forming liquid into a thin film includes:

[0033] The film-forming liquid is dispersed, filtered, and then poured onto a mold. After drying, the film is demoulded to obtain a film, which is the biogenic amine-responsive smart food packaging material based on Co-MOF / ortho-dihydroxy compound.

[0034] The Co-MOF / ortho-dihydroxy compound-based biogenic amine-responsive smart food packaging material of the present invention has antibacterial function, with inhibition rates against Escherichia coli and Staphylococcus aureus both ≥99%; after 24 hours of contact with Caco-2 and Hep G2 cells, the cell survival rates are both ≥90%; it has ammonia response characteristics, with an ammonia detection limit of <0.5ppm; and it can withstand 10 cycles of exposure to a tolerable "ammonia-acetic acid" environment without cracking or shrinking.

[0035] When the Co-MOF / vicinal dihydroxy compound-based biogenic amine-responsive smart food packaging material of the present invention is placed in an 800 μM ammonia environment, the total color difference can reach 24 within 10 minutes.

[0036] The inventors initially used Co-MOF as an indicator, but found that Co-MOF could not give the film sensitive ammonia response performance (the detection limit that can be achieved when the response time is ≥30min is ≥8ppm), and the film performance deteriorated. During the optimization process of the film formula, the inventors found that the unique molecular structure of the ortho-dihydroxy compound can bind to volatile biogenic amines and chelate Co ions, thereby producing a co-color effect with Co-MOF, which greatly reduced the ammonia detection limit (ammonia response detection limit <0.5ppm) and unexpectedly improved the ammonia response speed of the film (the total color difference within 10min of ammonia response time can reach 24), allowing the biogenic amine-responsive smart food packaging material to quickly respond to changes in food quality. Furthermore, the inventors unexpectedly found that Co-MOF can exert a synergistic antibacterial effect with the ortho-dihydroxy compound, which can ensure that the biogenic amine-responsive smart food packaging material is not contaminated by microorganisms during storage and application, and avoid the packaging itself from becoming a source of cross-contamination.

[0037] The present invention discloses the following technical effects:

[0038] Compared with the prior art, the advantages of the biogenic amine-responsive smart food packaging material based on Co-MOF / ortho-dihydroxy compound and its preparation method provided by the present invention are:

[0039] (1) The biogenic amine-responsive smart food packaging material based on Co-MOF / ortho-dihydroxy compounds of the present invention has excellent ammonia responsiveness. The ortho-dihydroxy compounds change the hue change of Co-MOF when responding to ammonia. The mixture of Co-MOF and ortho-dihydroxy compounds is used instead of natural pigments as an indicator, and the ammonia response speed is fast and the detection limit is low.

[0040] (2) The biogenic amine-responsive smart food packaging material based on Co-MOF / ortho-dihydroxy compounds of the present invention has efficient antibacterial and anti-mildew functions, can keep the label itself clean, and has an inhibition rate of ≥99% against representative pathogenic microorganisms (Escherichia coli, Staphylococcus aureus) and mold.

[0041] (3) As a bio-based plastic, the Co-MOF / ortho-dihydroxy compound-based biogenic amine-responsive smart food packaging material of the present invention has excellent mechanical properties and can ensure the integrity of the label during application.

[0042] (4) The biogenic amine-responsive smart food packaging material based on Co-MOF / ortho-dihydroxy compounds of the present invention has good biocompatibility, a cell survival rate of ≥90%, and high safety.

[0043] In summary, the technical solution provided by the present invention solves many shortcomings of the existing technology and innovatively manufactures a biogenic amine-responsive smart food packaging material based on Co-MOF / ortho-dihydroxy compounds. It has excellent ammonia response ability, antibacterial / antifungal ability, and physical and chemical properties. It can be applied to a variety of food packaging scenarios to achieve dynamic and real-time monitoring of food quality. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0045] Figure 1 This is the SEM image of the Co-MOF prepared in Example 1;

[0046] Figure 2 The univariate linear curves of ΔE and ammonia concentration of the food packaging materials prepared in Example 1, Example 2, Example 3, Comparative Example 1, Comparative Example 2, and Comparative Example 3 are fitted;

[0047] Figure 3 The ammonia detection limit of the food packaging materials prepared in Example 1, Example 2, Example 3, Comparative Example 1, Comparative Example 2 and Comparative Example 3;

[0048] Figure 4 The ammonia response sensitivity changes of the food packaging materials prepared in Example 1 and Comparative Example 1;

[0049] Figure 5 The antibacterial performance test results of the food packaging materials prepared in Example 1, Comparative Example 1 and Comparative Example 2 are shown;

[0050] Figure 6 The mechanical properties test results of the food packaging materials prepared in Example 1 and Comparative Example 1;

[0051] Figure 7 The test process of the deformation test and load test on the food packaging material prepared in Example 1, wherein A is the deformation test and B is the load test;

[0052] Figure 8 The color reversibility test results of the food packaging materials prepared in Example 1 and Comparative Example 1;

[0053] Figure 9 Effect of the food packaging material prepared in Example 1 on cell viability;

[0054] Figure 10Effect of the food packaging material prepared in Example 1 on cell morphology;

[0055] Figure 11 The food packaging materials prepared in Example 1, Example 2 and Comparative Example 1 have an indication effect on the freshness of shrimp. DETAILED DESCRIPTION

[0056] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as limiting the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0057] It should be understood that the terms described herein are intended only to describe particular embodiments and are not intended to limit the present invention. In addition, for numerical ranges herein, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. The intermediate value within any stated value or stated range, and each smaller range between any other stated value or intermediate value within the stated range, is also encompassed within the present invention. The upper and lower limits of these smaller ranges may be independently included or excluded within the scope.

[0058] Unless otherwise indicated, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art. Although only preferred methods and materials are described herein, any methods and materials similar or equivalent to those described herein may also be used in the practice or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials associated with the documents. In the event of any conflict with any incorporated document, the contents of this specification shall prevail.

[0059] It will be apparent to those skilled in the art that various modifications and variations may be made to the specific embodiments described herein without departing from the scope or spirit of the invention. Other embodiments will be apparent to those skilled in the art from the description of the invention. The description and examples are intended to be exemplary only.

[0060] The words “include,” “including,” “have,” “contain,” etc. used in this document are open-ended terms, meaning including but not limited to.

[0061] It should be pointed out that the matters not described in detail in the present invention are conventional operating means in this field and are not the focus of the present invention.

[0062] When referring to room temperature or normal temperature in the specific embodiments of the present invention, it specifically refers to 20-30°C.

[0063] Unless otherwise specified, all raw materials and reagents used in the embodiments of the present invention are common commercial products.

[0064] Example 1

[0065] A biogenic amine-responsive smart food packaging material based on Co-MOF / ortho-dihydroxy compound is prepared as follows:

[0066] (1) Synthesis of Co-MOF materials:

[0067] A mixture of cobalt acetate tetrahydrate and lauric acid was dissolved in anhydrous ethanol to obtain a mixed solution, wherein the mass ratio of cobalt acetate tetrahydrate to lauric acid was 1:6, and the mass / volume ratio of the mixture to anhydrous ethanol was 1 g:90 mL; pyromellitic acid was dissolved in N,N-dimethylformamide to obtain a pyromellitic acid solution, wherein the mass / volume ratio of pyromellitic acid to N,N-dimethylformamide was 1 g:667 mL; the above two solutions were mixed at a volume ratio of 1:1 at 25°C for 5 minutes to obtain a Co-MOF stock solution; the above Co-MOF stock solution was centrifuged at 4000 rpm for 15 minutes to separate a purple-red precipitate, and the supernatant was poured off; the above purple-red precipitate was washed with anhydrous ethanol for more than 3 times to remove unreacted organic matter and residual solvent; the washed purple-red precipitate was crystallized at 55°C in the dark for 12 hours to obtain a Co-MOF material powder.

[0068] The SEM image of the Co-MOF material powder prepared in this step is as follows Figure 1 As shown (the left side is a SEM image of multiple Co-MOF particles at low magnification, and the right side is an enlarged image of a single Co-MOF particle at high magnification), it can be seen that the Co-MOF material has a hexahedral micromorphology and a size of about 800 nm.

[0069] (2) Preparation of biogenic amine-responsive smart food packaging materials based on Co-MOF / ortho-dihydroxy compounds:

[0070] 5.4 g of hydroxypropyl distarch phosphate and 0.6 g of agar were placed in 200 mL of water, stirred in a 90°C water bath for 30 min, then 2.1 g of glycerol, 180 mg of Co-MOF material and 300 mg of tannic acid (ortho-dihydroxy compound) were added, and stirred again in a 90°C water bath for 30 min to obtain a film-forming liquid; the above film-forming liquid was dispersed at high speed at 12000 rpm for 1 min, filtered through gauze and poured onto a plastic culture dish, dried for 48 h, and demolded to obtain a film material (average thickness of the film was 0.07 mm), which is a biogenic amine-responsive smart food packaging material based on Co-MOF / ortho-dihydroxy compound.

[0071] Example 2

[0072] A biogenic amine-responsive smart food packaging material based on Co-MOF / ortho-dihydroxy compound is prepared as follows:

[0073] (1) Synthesis of Co-MOF materials: same as in Example 1.

[0074] (2) Preparation of biogenic amine-responsive smart food packaging materials based on Co-MOF / ortho-dihydroxy compounds:

[0075] 5.4 g of hydroxypropyl distarch phosphate and 0.6 g of agar were placed in 200 mL of water, stirred in a 90°C water bath for 30 min, then 2.1 g of glycerol, 180 mg of Co-MOF material and 180 mg of tannic acid (ortho-dihydroxy compound) were added, and stirred again in a 90°C water bath for 30 min to obtain a film-forming liquid; the above film-forming liquid was dispersed at high speed at 12000 rpm for 1 min, filtered through gauze and poured into a plastic petri dish, dried for 48 h, and demolded to obtain a film material (the average thickness of the film was 0.07 mm), which is a biogenic amine-responsive smart food packaging material based on Co-MOF / ortho-dihydroxy compound.

[0076] Example 3

[0077] A biogenic amine-responsive smart food packaging material based on Co-MOF / ortho-dihydroxy compound is prepared as follows:

[0078] (1) Synthesis of Co-MOF materials: same as in Example 1.

[0079] (2) Preparation of biogenic amine-responsive smart food packaging materials based on Co-MOF / ortho-dihydroxy compounds:

[0080] 5.4 g of hydroxypropyl distarch phosphate and 0.6 g of agar were placed in 200 mL of water, stirred in a 90°C water bath for 30 min, then 2.1 g of glycerol, 180 mg of Co-MOF material and 300 mg of caffeic acid (ortho-dihydroxy compound) were added, and stirred again in a 90°C water bath for 30 min to obtain a film-forming liquid; the above film-forming liquid was dispersed at high speed at 12000 rpm for 1 min, filtered through gauze and poured into a plastic petri dish, dried for 48 h, and demolded to obtain a film material (the average thickness of the film was 0.07 mm), which is a biogenic amine-responsive smart food packaging material based on Co-MOF / ortho-dihydroxy compound.

[0081] Comparative Example 1

[0082] A food packaging material is prepared by the same steps as in Example 1, except that tannic acid (an vicinal dihydroxy compound) is omitted.

[0083] Comparative Example 2

[0084] A food packaging material is prepared in the same manner as in Example 1, except that the synthesis and use of Co-MOF are omitted.

[0085] Comparative Example 3

[0086] A food packaging material is prepared by the same steps as in Example 1, except that 300 mg of tannic acid (an ortho-dihydroxy compound) is replaced by 300 mg of sorbitol (a non-ortho-dihydroxy compound).

[0087] Test Example 1

[0088] The ammonia response performance of the food packaging materials (ie, film materials) prepared in each example and comparative example was measured by the volatilization ammonia method.

[0089] (1) Detection limit test

[0090] The food packaging material was cut into 2cm×3cm strips and the color parameters of the sample before ammonia response (including lightness L * 、Redness a * Yellow and blue b * ), each group of samples was measured three times and the average value was taken. Take 14 culture dishes with a diameter of 15 cm, stick the samples on the culture dish cover respectively, and drop different volumes of 0.5 mol / L ammonia solution into the bottom of the culture dish respectively to construct a volatile ammonia environment of 5, 20, 30, 40, 50, 100, 150, 200, 250, 300, 350, 400, 800, and 1200 μM. Seal and react in the dark for 2 hours. After the reaction is completed, continue to measure the color parameters of the sample. Each group of samples was measured three times and the average value was taken. The total color difference (ΔE) was calculated by the color parameters of the sample before and after ammonia response, that is, the color parameters of the film before and after response in the CIE color space and the total color difference calculation formula (1). The ammonia detection limit was calculated by the linear relationship between ΔE and ammonia concentration.

[0091]

[0092] Where, L 前 * is the brightness before ammonia response, L 后 * is the brightness after ammonia response, a 前 * is the redness and greenness before ammonia response, a 后 * is the redness and greenness after ammonia response, b 前 * is the yellow-blue degree before ammonia response, b 后 * is the yellow-blue degree after ammonia response.

[0093] Figure 2 The following are the fitted linear curves of ΔE and ammonia concentration of the food packaging materials prepared in Example 1, Example 2, Example 3, Comparative Example 1, Comparative Example 2, and Comparative Example 3 (some curves are discontinuous because when the ammonia response of the film is more sensitive, the curves can be fitted in the low concentration range and the high concentration range respectively). Figure 3 The ammonia detection limit is obtained according to the unary linear curve. It can be seen that the ammonia detection limit of Comparative Example 1 is 8 ppm, the ammonia detection limit of Comparative Example 2 is 2 ppm, the ammonia detection limit of Comparative Example 3 is 12.1 ppm, the ammonia detection limit of Example 1 is 0.1 ppm, the ammonia detection limit of Example 2 is 0.3 ppm, and the ammonia detection limit of Example 3 is 0.35 ppm, indicating that the biogenic amine-responsive smart food packaging material based on Co-MOF / ortho-dihydroxy compound has good ammonia response performance.

[0094] (2) Sensitivity test

[0095] Food packaging materials were cut into 2cm x 3cm strips. The color parameters of the samples before ammonia response were measured using a CR-400 colorimeter. The measurements were repeated three times for each sample group, and the average value was taken. Five 15cm diameter Petri dishes were placed on the top of each dish. A specific volume of 0.5 mol / L ammonia solution was dripped into the bottom of each dish to create an 800μM volatile ammonia environment. The dishes were sealed and reacted in the dark for 10 minutes, 20 minutes, 30 minutes, 40 minutes, and 50 minutes. After the reaction, the color parameters of the samples were measured again. The measurements were repeated three times for each sample group, and the average value was taken. The total color difference (ΔE) was calculated to explore the sensitivity of the film's ammonia response.

[0096] Figure 4 The ammonia response sensitivity of the food packaging materials prepared in Example 1 and Comparative Example 1 is shown. After 10 minutes of ammonia response, Example 1 exhibits a significant color change, with a ΔE of 24, while Comparative Example 1 exhibits a less pronounced color change, with a ΔE of 0.9. Furthermore, after 30 minutes of ammonia response, the ΔE of Comparative Example 1 improves to 1.1, but is still far less than that of Example 1 (generally speaking, a color change can be observed with the naked eye when ΔE > 5, indicating a sensitive response). This demonstrates that the biogenic amine-responsive smart food packaging material based on Co-MOF / ortho-dihydroxy compounds of the present invention has excellent ammonia response sensitivity.

[0097] Test Example 2

[0098] The antibacterial properties of the food packaging materials prepared in each embodiment and comparative example were tested using the total colony formation method. The specific testing steps are as follows:

[0099] The film material was made into a 6 mm diameter disc and placed at the bottom of a 10 mL centrifuge tube (the disc must be sterilized under UV light for 6 hours on both sides). 6 Add a bacterial solution (Staphylococcus aureus or Escherichia coli) containing 500 CFU / mL of bacteria to a centrifuge tube, ensuring that the solution just covers the membrane sample. Wrap the junction between the tube mouth and the lid with plastic wrap to prevent contamination. After incubation at 37°C for 4 hours, add 5 mL of PBS buffer solution to the centrifuge tube and shake thoroughly to fully elute the bacterial solution on the membrane. Apply 100 μL of the mixture of bacterial solution and PBS to the membrane and incubate at 37°C for 24 hours. Count the colonies and calculate the inhibition rate.

[0100] The antibacterial performance test results (colony growth) of the food packaging materials prepared in Example 1, Comparative Example 1 and Comparative Example 2 against Staphylococcus aureus are as follows: Figure 5 As shown, it can be seen that the total number of colonies generated in Comparative Example 2 is about 120, and the antibacterial rate is 75.95%. The total number of colonies generated in Comparative Example 1 is about 47, and the antibacterial rate is 90.52%. The total number of colonies generated in Example 1 is 0, and the antibacterial rate is 100%. The antibacterial rate statistics of the food packaging materials of other embodiments or comparative examples when acting on Staphylococcus aureus, and the antibacterial rate statistics of the food packaging materials of various embodiments and comparative examples when acting on Escherichia coli are shown in Table 1 (wherein a negative antibacterial rate indicates that the growth of bacteria is promoted). Figure 5 As shown in Table 1, the biogenic amine-responsive smart food packaging material based on Co-MOF / ortho-dihydroxy compound of the present invention has strong antibacterial properties.

[0101] Table 1

[0102]

[0103] Test Example 3

[0104] The mechanical properties of the food packaging materials prepared in each embodiment and comparative example were measured. The specific test methods are as follows:

[0105] Cut the film into 8 cm x 1 cm strips and measure their tensile strength and elongation at break. Initially, the grip distance was 50 mm and the tensile speed was set at 100 mm / min. Five replicates were tested for each sample, and the average value was calculated.

[0106] The mechanical properties test results of the food packaging materials prepared in Example 1 and Comparative Example 1 are as follows: Figure 6 As shown, it can be seen that the tensile strength and elongation at break of Example 1 are both higher than those of Comparative Example 1. The tensile strengths of Example 1 and Comparative Example 1 are 14.65 MPa and 6.18 MPa, respectively, and the elongations at break are 42.8% and 21.7%, respectively. The tensile strength and elongation at break of other Examples and Comparative Examples are shown in Table 2.

[0107] In addition, the food packaging material prepared in Example 1 was subjected to deformation test and load test. The test process is as follows: Figure 7 As shown, A is the deformation test and B is the load test. Figure 7 It can be more intuitively felt that Example 1 has good mechanical properties. The mechanical property test results show that the biogenic amine responsive smart food packaging material based on Co-MOF / ortho-dihydroxy compound of the present invention has good mechanical properties.

[0108] Table 2

[0109] sample Tensile strength (Mpa) Elongation at break (%) Example 1 14.65 42.8 Example 2 11.83 29.53 Example 3 9.27 27.8 Comparative Example 1 6.18 21.7 Comparative Example 2 7.78 24.2 Comparative Example 3 5.36 19.8

[0110] Test Example 4

[0111] The color reversibility of the food packaging materials prepared in each embodiment and comparative example was measured. The specific test method is as follows:

[0112] The film material was cut into 3cm×1.5cm strips and attached to the top of a Petri dish containing 15mL ammonia (2mol / L) for 10 minutes, and then attached to the top of a Petri dish containing 15mL acetic acid (2mol / L) for 10 minutes, and the cycle was repeated several times. A portable colorimeter was used to measure the a of the film sample after exposure to ammonia and acetic acid environments. * 、b * Value (where a * represents redness and greenness, b * The change of yellow-blue degree is used to judge the color change of the film.

[0113] The color reversibility test results of the food packaging materials prepared in Example 1 and Comparative Example 1 are as follows: Figure 8 As shown (wherein the odd number indicates the case of ammonia, and the even number indicates the case of acetic acid), it can be seen that after 10 cycles of exposure to the "ammonia-acetic acid" environment, Example 1 exhibits obvious color reversible behavior. * 、b * The value repeatedly increases and decreases. Comparative Example 1 has basically no color reversible behavior. * 、b * The experimental results show that the biogenic amine responsive smart food packaging material based on the Co-MOF / ortho-dihydroxy compound of the present invention has good color reversibility.

[0114] In addition, after 10 cycles of exposure to the "ammonia-acetic acid" environment, the film morphology of Example 1 was observed to be neither broken nor shrunk, while the film of Comparative Example 1 shrunk and part of the film was broken and incomplete.

[0115] Test Example 5

[0116] Determination of the biocompatibility of the Co-MOF / ortho-dihydroxy compound-based biogenic amine-responsive smart food packaging material of the present invention:

[0117] To verify the biocompatibility of the food packaging material (i.e., film material) obtained in Example 1, human colon cancer cells (Caco-2 cells) and human liver cancer cells (Hep G2 cells) were selected for cytotoxicity evaluation. The film material obtained in Example 1 was cut into 2 cm × 2 cm square pieces, and the square pieces were soaked in a Caco-2 cell-specific culture medium or a Hep G2 cell-specific culture medium for 24 hours to obtain a film soaking solution. Caco-2 or Hep G2 cells were incubated with the corresponding film soaking solution at 37°C in a 5 vol% CO2 atmosphere for 24 hours. The cell viability was determined using the CCK-8 method. The drug-containing culture medium in the well was aspirated, and 100 μL of a pre-prepared cell culture medium containing 10 wt% CCK-8 was added. The cells were incubated at 37°C for 0.5 hours, and the absorbance at 450 nm was measured. Cell viability was expressed as the absorbance relative to the control, where the control group contained only culture medium and cells. In addition, the cells were stained with crystal violet to observe changes in cell morphology. Specifically, the cells were fixed with 4 wt % paraformaldehyde, stained with 0.5 wt % crystal violet solution, washed with PBS to remove excess dye, and observed and imaged under an inverted fluorescence microscope.

[0118] The effect of the food packaging material prepared in Example 1 on cell viability is as follows Figure 9 As shown in the figure, it can be seen that when cells were treated with the film soaking solution of Example 1, the cell viability of Caco-2 was 91% and that of Hep G2 was 93%. A cell viability higher than 80% can be considered as a material with good cell compatibility. Figure 10 As shown, compared with the control group, the number of cells treated in Example 1 decreased, the number of cell fragments increased, and the changes in cell morphology were consistent with the cell survival rate results. The experimental results show that the biogenic amine-responsive smart food packaging material based on Co-MOF / ortho-dihydroxy compounds of the present invention has good safety.

[0119] Test Example 6

[0120] The shrimp freshness indication test was conducted on the biogenic amine-responsive smart food packaging material based on Co-MOF / ortho-dihydroxy compound prepared by the present invention. The specific test method is as follows:

[0121] Fresh white shrimp were purchased from a supermarket. After the surface moisture of the shrimp was wiped dry, the shrimp was placed in a culture dish. The film materials prepared in Example 1, Example 2, and Comparative Example 1 were attached to the upper cover of the culture dish. The dish was sealed with plastic wrap and placed in a cold storage at 0-4°C for 10 days. During this period, the color change of the film was observed every 2 days and photographed and recorded.

[0122] The test results are as follows Figure 11 As shown, it can be seen that as the storage time increases, the shrimp gradually turns red, and mucus and a foul odor appear on the surface. The films of Examples 1 and 2 also gradually change from light yellow to dark brown, with obvious hue changes, while the hue change of Comparative Example 1 is not obvious, indicating that the food packaging materials prepared in Examples 1 and 2 can well indicate the freshness of shrimp.

[0123] In summary, the present invention provides a biogenic amine-responsive smart food packaging material based on Co-MOF / ortho-dihydroxy compounds and a method for preparing the same. The biogenic amine-responsive smart food packaging material based on Co-MOF / ortho-dihydroxy compounds exhibits excellent ammonia response, antibacterial, and mechanical properties, significantly extending the shelf life of food and providing an intelligent indicator of food freshness. This biogenic amine-responsive smart food packaging material based on Co-MOF / ortho-dihydroxy compounds has the potential for large-scale commercial production and possesses high application value in the food packaging field.

[0124] The embodiments described above are merely descriptions of preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Without departing from the spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by persons skilled in the art shall fall within the scope of protection defined by the claims of the present invention.

Claims

1. A biogenic amine-responsive smart food packaging material based on Co-MOF / ortho-dihydroxy compounds, characterized in that: Calculated by mass, the raw materials include: 80 to 90 parts of starch, 10 to 20 parts of hydrophilic colloid, 35 to 40 parts of plasticizer, 1 to 5 parts of Co-MOF material and 1 to 10 parts of ortho-dihydroxy compound.

2. The biogenic amine-responsive smart food packaging material based on Co-MOF / ortho-dihydroxy compound according to claim 1, characterized in that: The preparation steps of the Co-MOF material include: A Co-MOF stock solution is prepared using a cobalt source, lauric acid and trimesic acid as raw materials; the Co-MOF stock solution is centrifuged, and the obtained precipitate is crystallized under heating conditions to obtain the Co-MOF material.

3. The biogenic amine-responsive smart food packaging material based on Co-MOF / ortho-dihydroxy compound according to claim 2, characterized in that: The method of preparing a Co-MOF stock solution using a cobalt source, lauric acid, and trimesic acid as raw materials includes: mixing the cobalt source, lauric acid, and solvent 1 to obtain a mixed solution; mixing trimesic acid and solvent 2 to obtain a trimesic acid solution; and mixing the mixed solution with the trimesic acid solution to obtain a Co-MOF stock solution.

4. The biogenic amine-responsive smart food packaging material based on Co-MOF / ortho-dihydroxy compound according to claim 3, characterized in that: The cobalt source includes cobalt acetate tetrahydrate; and / or, the solvent 1 comprises ethanol; And / or, the mass ratio of the cobalt source to the lauric acid is 1:5-7; and / or, the ratio of the sum of the mass of the cobalt source and the lauric acid to the volume of the solvent 1 is 1 g:90-100 mL; and / or, the solvent 2 comprises N,N-dimethylformamide; and / or, the mass volume ratio of the trimesic acid to the solvent 2 is 1 g:650-700 mL; And / or, the volume ratio of the mixed solution to the trimesic acid solution is 1:

1.

5. The biogenic amine-responsive smart food packaging material based on Co-MOF / ortho-dihydroxy compound according to claim 2, wherein: The heating temperature is 50-55°C; And / or, the crystallization is carried out under light-proof conditions; And / or, the crystallization time is 10-12 hours.

6. The biogenic amine-responsive smart food packaging material based on Co-MOF / ortho-dihydroxy compound according to claim 1, wherein: The starch comprises one or more of cassava starch, acid-hydrolyzed cassava starch, oxidized cassava starch, hydroxypropyl distarch phosphate and octenyl succinic anhydride modified starch; And / or, the hydrophilic colloid comprises one or more of agar, sodium alginate, xanthan gum, carrageenan, sodium carboxymethyl cellulose and polyvinyl alcohol; And / or, the plasticizer comprises glycerol.

7. The biogenic amine-responsive smart food packaging material based on Co-MOF / ortho-dihydroxy compound according to claim 1, wherein: The vicinal dihydroxy compound includes one or more of catechin, gallic acid, caffeic acid, ferulic acid, chlorogenic acid, epigallocatechin gallate and tannic acid.

8. A method for preparing a biogenic amine-responsive smart food packaging material based on Co-MOF / ortho-dihydroxy compound according to any one of claims 1 to 7, characterized in that: The following steps are involved: The starch is mixed with the hydrophilic colloid and water, and after heating and stirring, the plasticizer, the Co-MOF material and the ortho-dihydroxy compound are added and continued to heat and stir to obtain a film-forming liquid; the film-forming liquid is prepared into a film to obtain the Co-MOF / ortho-dihydroxy compound-based biogenic amine-responsive smart food packaging material.

9. The method for preparing a biogenic amine-responsive smart food packaging material based on Co-MOF / ortho-dihydroxy compound according to claim 8, wherein: The ratio of the sum of the mass of the starch and the hydrophilic colloid to the volume of the water is 3g:100mL; And / or, the heating and stirring are performed at a temperature of 90-100° C. and for a time of 30-40 min.

10. The method for preparing a biogenic amine-responsive smart food packaging material based on Co-MOF / ortho-dihydroxy compound according to claim 8, wherein: The steps of preparing the film-forming liquid into a thin film include: The film-forming liquid is dispersed, filtered, and then poured onto a mold. After drying, the film is demoulded to obtain a film, which is the biogenic amine-responsive smart food packaging material based on Co-MOF / ortho-dihydroxy compound.

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