Fresh-keeping antibacterial material based on food freshness indication and application of fresh-keeping antibacterial material

Abstract

The invention provides a fresh-keeping antibacterial material based on food freshness indication and application of the fresh-keeping antibacterial material. The preparation method comprises the following steps: preparing a multivesicular liposome loaded with L-egg aminoacyl glycine-tannic acid and origanum vulgare essential oil, embedding a volatile amine indicating material and a pectinase response material, preparing a geniposide-bamboo leaf flavonoid solution, and clathrating boric acid ester bond modified hydroxycucurbituril. The invention belongs to the technical field of food fresh-keeping materials. The prepared fresh-keeping antibacterial material can realize first-stage release of geniposide-bamboo leaf flavonoid and second-stage release of multivesicular liposome, boric acid ester bonds in hydroxyl cucurbituril modified by boric acid ester bonds in the outermost layer structure are broken and reconstructed according to pH change in the food storage period, substances in the two stages are selectively released, and the fresh-keeping antibacterial material has the advantages that the fresh-keeping antibacterial effect is good, and the fresh-keeping antibacterial effect is good. Growth and reproduction of pathogenic microorganisms and generation of harmful substances are inhibited in the food storage period, the freshness of the food is guaranteed, the shelf life of the food is prolonged, and a new direction is provided for research of multifunctional materials in the food field.

Description

Technical Field

[0001] The invention belongs to the technical field of food preservation materials, and in particular relates to a food freshness indication-based preservation and antibacterial material and application thereof. Background Art

[0002] Food freshness refers to the ability of food to maintain its original quality, nutritional value, taste and safety during the production, processing, storage and sales process. It involves the color, smell, taste, texture and microbiological indicators of food, and is an important criterion for measuring whether food is suitable for consumption. The level of freshness directly affects the quality of food and the health of consumers. Fresh food usually has a longer shelf life and is in good condition in terms of appearance, taste, smell and color. The method of ensuring the freshness of food in the prior art usually uses freshness indicator materials to react by color change, embed the pigment in the support body, and change the color of the pigment according to the adverse changes produced by the food during storage, and use this as a basis to judge the freshness of the food. The pigments used in food freshness indicator materials include synthetic pigments and natural pigments. Synthetic pigments include cresol red, methyl red, bromocresol purple, bromocresol green, chlorophenol, bromothymol blue and xylenol, etc., but most synthetic pigments are toxic or even carcinogenic, which will cause serious threats to life and the environment. Natural pigments include anthocyanins, alizarin, curcumin, shikonin, anthocyanins, betalains, etc., but the pH response color change sensitivity of natural pigments is low, there is light instability, and in the internal high humidity environment, natural pigments are easily dissolved and leaked from the indicator label, resulting in a decrease in the concentration of the pigment in the indicator label and uneven distribution, which then causes uncontrollable changes in the indicator label's indication performance. Most food freshness indicator materials are pH-responsive and are easily affected by environmental factors such as temperature, humidity, and interfering gases, resulting in inaccurate color development and false positive results. Moreover, most existing food freshness indicator materials can only reflect changes in food freshness, have a single function, and do not have the function of improving food storage quality. Although antibacterial food freshness indicator materials have been developed, their research is still shallow, and their antibacterial effect only works in the early stage of fresh food storage to extend the shelf life of food, but has little effect during the storage of fresh food. Therefore, it is urgent to explore new functional materials that can ensure the quality of fresh food during storage and extend the shelf life of food through the principle of changes in food freshness indication. Summary of the invention

[0003] Technical problems to be solved: In view of the above technical problems, the purpose of the present invention is to provide a fresh-keeping antibacterial material based on food freshness indication and its application, and its preparation method includes the preparation of multivesicular liposomes loaded with L-methionylglycine-tannic acid and oregano essential oil, embedding of volatile amine indicator materials and pectinase response materials, preparation of geniposide-bamboo leaf flavonoids solution, and inclusion of hydroxycucurbituril modified by boronate bonds, belonging to the technical field of food fresh-keeping materials. The fresh-keeping antibacterial material prepared by the present invention can realize the first-stage release of geniposide-bamboo leaf flavonoids and the second-stage release of multivesicular liposomes. According to the pH change during food storage, the boronate bonds in the hydroxycucurbituril modified by boronate bonds in the outermost structure are broken and reconstructed, and the substances in the two stages are selectively released, and the growth and reproduction of pathogenic microorganisms and the generation of harmful substances are inhibited during food storage, so as to ensure the freshness of food and extend the shelf life of food, and provide a new direction for the research of multifunctional materials in the field of food.

[0004] Technical solution: A method for preparing a fresh-keeping and antibacterial material based on food freshness indication, comprising the following steps: S1. Preparation of multivesicular liposomes loaded with L-methionylglycine-tannic acid and oregano essential oil; S2. Weigh 1-5wt% of thorny gum and add water to mix evenly, then add McBride's acid activated furan and high methoxy pectin nanoparticles, stir for 15-30min at 25-45°C and 200-300rpm, then add multivesicular liposomes loaded with L-methionylglycine-tannic acid and oregano essential oil and mix evenly to obtain solution A; S3. Weigh 0.2-0.8wt% geniposide and 0.1-0.2wt% bamboo leaf flavonoids and dissolve them uniformly at 60-75°C to obtain solution B; S4. Add ultrapure water to 1-3 wt % borate-modified hydroxycucurbituril, and ultrasonicate at room temperature for 30-60 min to obtain solution C; S5. Mix solution A and solution B evenly, add solution C and stir at room temperature for 45-60 minutes, cast into a film, and vacuum dry to obtain a fresh-keeping and antibacterial material. Furthermore, the method for preparing multivesicular liposomes loaded with L-methionylglycine-tannic acid and oregano essential oil in step S1 comprises the following steps: Step 1. Weigh 3-5wt% L-methionylglycine and 4-8wt% tannic acid, add water and dissolve them evenly to prepare an L-methionylglycine-tannic acid solution; Step 2. Weigh 2-6 wt% of oregano essential oil, add ethanol to dissolve evenly, and prepare an oregano essential oil solution; Step 3. The L-methionylglycine-tannic acid solution and the oregano essential oil solution are mixed in a ratio of (1-4):(2-5), and ultrasonically treated for 15-20 minutes to obtain a mixed solution; Step 4. Phosphatidylcholine and cholesterol are mixed in a ratio of 1:(2-5), dissolved in ethanol and rotary evaporated to obtain a liposome membrane, and then 10-20wt% of the mixed solution is added, and microfiltration is performed at 5000-7000rpm for 30-45min to obtain multivesicular liposomes loaded with L-methionylglycine-tannic acid and oregano essential oil. Furthermore, in step S2, the amount of the furan activated with McBride's acid added is 5-10 wt %, and the amount of the high methoxyl pectin nanoparticles added is 1-3 wt %. Furthermore, the preparation method of the high methoxy pectin nanoparticles is to dissolve the high methoxy pectin in an acetate buffer, adjust the pH to 4-5, heat at 80-90° C. for 15-30 minutes, immediately immerse in an ice water bath and freeze-dry to obtain the high methoxy pectin nanoparticles. Furthermore, in step S2, the amount of multivesicular liposomes loaded with L-methionylglycine-tannic acid and oregano essential oil is 5-15 wt %. Furthermore, the preparation method of the boronate bond-modified hydroxycucurbituril in step S4 is to dissolve hydroxycucurbituril and phenyldiboronic acid in ethanol in a ratio of 1:(4-8), treat at 30-40° C. for 2-4 h, and vacuum dry to obtain the boronate bond-modified hydroxycucurbituril. Furthermore, in step S5, the ratio of solution A, solution B and solution C is (1-5):(2-4):(1-3). Furthermore, the vacuum drying conditions in step S5 are a drying temperature of 40-50° C. and a drying time of 4-6 hours. A freshness-preserving and antibacterial material based on food freshness indication prepared by any of the methods described above. The application of the above-mentioned freshness-preserving and antibacterial materials based on food freshness indication in improving food storage quality. Beneficial effects: 1. The food freshness indication-based freshness-preserving and antibacterial material prepared in the present invention is prepared by double-layer embedded multivesicular liposomes. The multivesicular liposomes embed L-methionylglycine, tannic acid and oregano essential oil, which can reduce the influence of mutual repulsion between hydrophilic substances and hydrophobic substances due to different molecular polarities, and avoid the mutual collision of the three molecules inside the fresh-keeping and antibacterial material, resulting in a decrease in mechanical properties; at the same time, the gel network structure formed by the thorny tava gum is embedded in the multivesicular liposomes, which can improve the degree of uniform distribution of the multivesicular liposomes inside the material. In addition, geniposide and bamboo leaf flavonoids can also be combined in the gel network of the thorny tava gum, and mutually combine with the hydrophilic groups at the head of the multivesicular liposomes to strengthen the structural strength and stability between the aggregates. The aggregates are embedded in the interior of the hydroxycucurbituril and interact with the groups in the cavity of the cucurbituril, further strengthening the mechanical properties of the fresh-keeping and antibacterial material, ensuring that the fresh-keeping and antibacterial effect of the embedded substances is not affected by external conditions. 2. The fresh-keeping and antibacterial material based on food freshness indication prepared in the present invention has a low pH value of the food matrix due to the glycolysis reaction of the sugar substances in the food in the early stage of storage to produce acidic substances such as lactic acid and pyruvic acid, and the dissolution of carbon dioxide produced by respiration. Therefore, the borate bond modified hydroxycucurbituril in the outermost structure of the fresh-keeping and antibacterial material breaks under low pH conditions, causing the geniposide and bamboo leaf flavonoids embedded in the middle layer to penetrate into the food as the first stage of release; at the same time, geniposide and bamboo leaf flavonoids can inhibit the growth of pathogenic microorganisms in the food and The oxidation reaction can prevent food from spoiling and extend the shelf life of food. In addition, geniposide can cross-link with proteins, polysaccharides, etc. in food to form a stable network structure, enhance the texture and stability of food, and prevent food from deforming or losing during storage. Bamboo leaf flavonoids can also react with acidic substances in food to adjust the pH value of food, keep the food in a suitable acid-base environment, and ensure the freshness of food. In addition, the borate bond contained in the borate bond-modified hydroxycucurbituril is dynamically reversible, and the borate bond is reformed to maintain the stability of the outer layer structure. 3. The freshness-preserving and antibacterial material based on food freshness indication prepared in the present invention releases geniposide and bamboo leaf flavonoids in the first stage. When the effects of geniposide and bamboo leaf flavonoids are fully exerted, for foods with high protein content such as meat and fish, proteins, fats and other substances in the foods produce volatile organic amines under the metabolism of spoilage microorganisms, resulting in an increase in the pH value of the food. The boric acid ester bonds in the hydroxycucurbituril are attacked and broken, causing the multivesicular liposomes encapsulated by the hydroxycucurbituril to lose their restraints and be released, and the tsugae gum loaded with the multivesicular liposomes is The network structure disintegrates due to the reaction between McBride's acidified furan and volatile organic amines, releasing L-methionylglycine and oregano essential oil in the multivesicular liposomes; at the same time, on the one hand, L-methionylglycine contains glycine, which can competitively bind to the active site of the key enzyme in the volatile organic amine synthesis pathway, thereby reducing the catalytic activity of the enzyme; on the other hand, oregano essential oil contains antioxidant and antibacterial ingredients, which inhibit the growth and reproduction of microorganisms that produce key enzymes in the volatile organic amine synthesis pathway. The two work synergistically to ensure the quality of food and extend the shelf life of food. 4. The fresh-keeping and antibacterial material based on food freshness indication prepared in the present invention releases geniposide and bamboo leaf flavonoids in the first stage. When the effects of geniposide and bamboo leaf flavonoids are fully exerted, for foods such as fruits and vegetables, due to the after-ripening effect of fruits and vegetables, the degradation of organic acids and the generation of alcohol substances in the late storage period lead to an increase in the pH of the food, and the boric acid ester bonds in the hydroxycucurbituril are attacked and broken, so that the multivesicular liposomes enclosed by the hydroxycucurbituril lose their restraints and are released, and the network structure of the thorny tsugae gum loaded with the multivesicular liposomes is destroyed due to the decomposition of high methoxyl pectin nanoparticles by pectinase, resulting in the destruction of the gel structure, and tannic acid and oregano essential oil in the multivesicular liposomes; at the same time, tannic acid and oregano essential oil, on the one hand, cross-link with the active sites in pectinase to inhibit the activity of pectinase, prevent pectinase from decomposing pectin and ensure the freshness of fresh-cut fruits and vegetables, and on the other hand, the antioxidant and antibacterial effects of the two can remove free radicals and corrupt microorganisms, ensure the quality of fresh-cut fruits and vegetables, and extend the storage time. 5. The present invention prepares food preservative and antibacterial materials based on the principle of food freshness indication, which can not only maintain the freshness of food for a long time, improve food quality during storage, and extend the shelf life of food, but also increase the functions of food indicator materials, providing new research ideas and data support for multifunctional materials in the food field. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 Changes in the total bacterial count of the fresh-keeping and antibacterial materials prepared in Example 6 and Comparative Examples 1-4 during the storage of chicken; Figure 2 pH changes of the fresh-keeping and antibacterial materials prepared in Example 6 and Comparative Examples 1-4 during the storage of chicken; Figure 3Changes in TBA of the fresh-keeping and antibacterial materials prepared in Example 6 and Comparative Examples 1-4 during chicken storage; Figure 4 Changes in TVB-N of the fresh-keeping and antibacterial materials prepared in Example 6 and Comparative Examples 1-4 during chicken storage; Figure 5 Sensory evaluation of the fresh-keeping and antibacterial materials prepared in Example 6 and Comparative Examples 1-4 in chicken stored for 15 days; Figure 6 Changes in the total number of bacterial colonies of the fresh-keeping and antibacterial materials prepared in Example 6 and Comparative Examples 1-4 during storage of fresh-cut apples; Figure 7 pH changes of the fresh-keeping and antibacterial materials prepared in Example 6 and Comparative Examples 1-4 during storage of fresh-cut apples; Figure 8 Changes in the browning index (BI) of the fresh-keeping and antibacterial materials prepared in Example 6 and Comparative Examples 1-4 during storage of fresh-cut apples; Fig. 9 The hardness changes of the fresh-keeping and antibacterial materials prepared in Example 6 and Comparative Examples 1-4 during the storage of fresh-cut apples; Fig.10 Sensory evaluation of the fresh-keeping and antibacterial materials prepared in Example 6 and Comparative Examples 1-4 on fresh-cut apples after storage for 15 days. DETAILED DESCRIPTION The present invention will be further described below in conjunction with embodiments, which are explanations of the present invention and are not limited to the following embodiments: Example 1 The preparation method of multivesicular liposomes loaded with L-methionylglycine-tannic acid and oregano essential oil comprises the following steps: Step 1. Weigh 4 g L-methionylglycine and 6 g tannic acid, add 90 g water and dissolve evenly to prepare L-methionylglycine solution; Step 2. Weigh 4 g of oregano essential oil, add 96 mL of ethanol and dissolve evenly to prepare an oregano essential oil solution; Step 3. 80 g of L-methionylglycine solution and 120 g of oregano essential oil solution were mixed and ultrasonicated for 20 min to prepare a mixed solution; Step 4. 40 g of phosphatidylcholine and 160 g of cholesterol were mixed, dissolved in ethanol and rotary evaporated to obtain liposome membrane, and then 40 g of the mixed solution was added and microfiltered at 5000 rpm for 45 min to obtain multivesicular liposomes loaded with L-methionylglycine-tannic acid and oregano essential oil. Example 2 The preparation method of multivesicular liposomes loaded with L-methionylglycine-tannic acid and oregano essential oil comprises the following steps: Step 1. Weigh 3 g of L-methionylglycine and 6 g of tannic acid, add 91 g of water and dissolve evenly to prepare an L-methionylglycine solution; Step 2. Weigh 4 g of oregano essential oil, add 96 mL of ethanol and dissolve evenly to prepare an oregano essential oil solution; Step 3. 80 g of L-methionylglycine solution and 120 g of oregano essential oil solution were mixed and ultrasonicated for 20 min to prepare a mixed solution; Step 4. 40 g of phosphatidylcholine and 160 g of cholesterol were mixed, dissolved in ethanol and rotary evaporated to obtain liposome membrane, and then 40 g of the mixed solution was added and microfiltered at 5000 rpm for 45 min to obtain multivesicular liposomes loaded with L-methionylglycine-tannic acid and oregano essential oil. Example 3 The preparation method of multivesicular liposomes loaded with L-methionylglycine-tannic acid and oregano essential oil comprises the following steps: Step 1. Weigh 4 g L-methionylglycine and 6 g tannic acid, add 90 g water and dissolve evenly to prepare L-methionylglycine solution; Step 2. Weigh 6 g of oregano essential oil, add 94 mL of ethanol and dissolve evenly to prepare an oregano essential oil solution; Step 3. 80 g of L-methionylglycine solution and 120 g of oregano essential oil solution were mixed and ultrasonicated for 20 min to prepare a mixed solution; Step 4. 40 g of phosphatidylcholine and 160 g of cholesterol were mixed, dissolved in ethanol and rotary evaporated to obtain liposome membrane, and then 40 g of the mixed solution was added and microfiltered at 5000 rpm for 45 min to obtain multivesicular liposomes loaded with L-methionylglycine-tannic acid and oregano essential oil. Example 4 The preparation method of multivesicular liposomes loaded with L-methionylglycine-tannic acid and oregano essential oil comprises the following steps: Step 1. Weigh 4 g L-methionylglycine and 6 g tannic acid, add 90 g water and dissolve evenly to prepare L-methionylglycine solution; Step 2. Weigh 4 g of oregano essential oil, add 96 mL of ethanol and dissolve evenly to prepare an oregano essential oil solution; Step 3. 40 g of L-methionylglycine solution and 160 g of oregano essential oil solution were mixed and ultrasonicated for 20 min to prepare a mixed solution; Step 4. 40 g of phosphatidylcholine and 160 g of cholesterol were mixed, dissolved in ethanol and rotary evaporated to obtain liposome membrane, and then 40 g of the mixed solution was added and microfiltered at 5000 rpm for 45 min to obtain multivesicular liposomes loaded with L-methionylglycine-tannic acid and oregano essential oil. Example 5 The preparation method of multivesicular liposomes loaded with L-methionylglycine-tannic acid and oregano essential oil comprises the following steps: Step 1. Weigh 4 g L-methionylglycine and 6 g tannic acid, add 90 g water and dissolve evenly to prepare L-methionylglycine solution; Step 2. Weigh 4 g of oregano essential oil, add 96 mL of ethanol and dissolve evenly to prepare an oregano essential oil solution; Step 3. 80 g of L-methionylglycine solution and 120 g of oregano essential oil solution were mixed and ultrasonicated for 20 min to prepare a mixed solution; Step 4. 40 g of phosphatidylcholine and 160 g of cholesterol were mixed, dissolved in ethanol and rotary evaporated to obtain liposome membrane, and then 30 g of the mixed solution was added and microfiltered at 5000 rpm for 45 min to obtain multivesicular liposomes loaded with L-methionylglycine-tannic acid and oregano essential oil. Performance Testing (1) Average particle size The multivesicular liposomes loaded with L-methionylglycine-tannic acid and oregano essential oil prepared in Example 1-5 were diluted 100 times with distilled water, and the average particle size of Example 1-5 was measured using a particle size analyzer. (2) Encapsulation efficiency The embedding efficiency of L-methionylglycine, tannic acid and oregano essential oil in Examples 1-5 was determined as follows: ① Embedding efficiency of L-methionylglycine: After the multivesicular liposomes loaded with L-methionylglycine-tannic acid and oregano essential oil were dissolved in methanol, the content of L-methionylglycine was determined by high performance liquid chromatography, and the embedding efficiency of L-methionylglycine in the multivesicular liposomes was calculated; ② The embedding efficiency of oregano essential oil: accurately weigh 4g of multivesicular liposomes, add 10mL of petroleum ether, stir gently for 2min to dissolve, pour out the filtrate, filter, dry in a drying oven at 30°C until the mass is constant and record it as M1; accurately weigh 4g of multivesicular liposomes and dissolve them in 10mL of petroleum ether, ultrasonicate for 10min at 70% amplitude and 20kHz, filter the extract, rinse the filter cake with 20mL of petroleum ether 2-3 times, and dry the combined filtrate in a drying oven at 30°C until the mass is constant and record it as M2, and calculate the embedding efficiency of oregano essential oil; ③ The embedding efficiency of tannic acid: the multivesicular liposomes are dispersed in 10mL of water, and then ultrasonicated for 20min at an ultrasonic power of 300W, and then the suspension is centrifuged at a speed of 10000r / min for 15min, and 2mL of supernatant is removed and mixed with an equal volume of 0.05M ferric sulfate solution, and after standing for 1min, the absorbance of the mixture at 658nm is measured using a spectrophotometer to calculate the embedding efficiency of tannic acid. Table 1 Average particle size and encapsulation efficiency of multivesicular liposomes prepared in Examples 1-5 As can be seen from Table 1, the average particle size of Example 1 is smaller than that of Examples 2-5, while the embedding efficiency is higher than that of Examples 2-5, indicating that the addition amount and proportion of L-methionylglycine, oregano essential oil, and tannic acid, as well as the membrane material and solution addition amount of the multivesicular liposomes will affect the average particle size and embedding efficiency of the multivesicular liposomes loaded with L-methionylglycine-tannic acid and oregano essential oil. Therefore, the multivesicular liposomes loaded with L-methionylglycine-tannic acid and oregano essential oil in the following examples are obtained by the preparation method in Example 1. Example 6 A method for preparing a fresh-keeping and antibacterial material based on food freshness indication comprises the following steps: S1. Weigh 3 g of thorny gum and add 97 g of water to mix evenly, then add 8 g of furan activated by McBride's acid and 3 g of high methoxy pectin nanoparticles, stir at 30 ° C and 200 rpm for 25 min, then add 10 g of multivesicular liposomes loaded with L-methionylglycine-tannic acid and oregano essential oil and mix evenly to prepare solution A; S2. Weigh 0.6 g of geniposide and 1.5 g of bamboo leaf flavonoids, add 97.9 g and dissolve evenly at 75 ° C to obtain solution B; S3. 2 g of hydroxycucurbituril and 12 g of phenyldiboronic acid were dissolved in 40 mL of ethanol, treated at 40 °C for 3 h, and vacuum dried to obtain boronate bond-modified hydroxycucurbituril; S4. Add 98 g of ultrapure water to 2 g of hydroxycucurbituril modified with borate bond, and ultrasonicate at room temperature for 45 min to obtain solution C. S5. Evenly mix 60 g of solution A and 60 g of solution B, add 40 g of solution C, stir at room temperature for 60 min, cast into film, and vacuum dry at 50°C for 6 h to obtain the fresh-keeping and antibacterial material. Example 7 A method for preparing a fresh-keeping and antibacterial material based on food freshness indication comprises the following steps: S1. Weigh 5 g of thorny gum and add 95 g of water to mix evenly, then add 8 g of furan activated by McBride's acid and 3 g of high methoxy pectin nanoparticles, stir at 30 ° C and 200 rpm for 25 min, then add 10 g of multivesicular liposomes loaded with L-methionylglycine-tannic acid and oregano essential oil and mix evenly to prepare solution A; S2. Weigh 0.6 g of geniposide and 1.5 g of bamboo leaf flavonoids, add 97.9 g and dissolve evenly at 75 ° C to obtain solution B; S3. 2 g of hydroxycucurbituril and 12 g of phenyldiboronic acid were dissolved in 40 mL of ethanol, treated at 40 °C for 3 h, and vacuum dried to obtain boronate bond-modified hydroxycucurbituril; S4. Add 98 g of ultrapure water to 2 g of hydroxycucurbituril modified with borate bond, and ultrasonicate at room temperature for 45 min to obtain solution C. S5. Evenly mix 60 g of solution A and 60 g of solution B, add 40 g of solution C, stir at room temperature for 60 min, cast into film, and vacuum dry at 50°C for 6 h to obtain the fresh-keeping and antibacterial material. Example 8 A method for preparing a fresh-keeping and antibacterial material based on food freshness indication comprises the following steps: S1. Weigh 3 g of thorny gum and add 97 g of water and mix well, then add 5 g of furan activated by McBride's acid and 3 g of high methoxy pectin nanoparticles, stir at 30 ° C and 200 rpm for 25 min, then add 10 g of multivesicular liposomes loaded with L-methionylglycine-tannic acid and oregano essential oil and mix well to prepare solution A; S2. Weigh 0.6 g of geniposide and 1.5 g of bamboo leaf flavonoids, add 97.9 g and dissolve evenly at 75 ° C to obtain solution B; S3. 2 g of hydroxycucurbituril and 12 g of phenyldiboronic acid were dissolved in 40 mL of ethanol, treated at 40 °C for 3 h, and vacuum dried to obtain boronate bond-modified hydroxycucurbituril; S4. Add 98 g of ultrapure water to 2 g of hydroxycucurbituril modified with borate bond, and ultrasonicate at room temperature for 45 min to obtain solution C. S5. Evenly mix 60 g of solution A and 60 g of solution B, add 40 g of solution C, stir at room temperature for 60 min, cast into film, and vacuum dry at 50°C for 6 h to obtain the fresh-keeping and antibacterial material. Example 9 A method for preparing a fresh-keeping and antibacterial material based on food freshness indication comprises the following steps: S1. Weigh 3 g of thorny gum and add 97 g of water to mix evenly, then add 8 g of furan activated by McBride's acid and 3 g of high methoxy pectin nanoparticles, stir at 30 ° C and 200 rpm for 25 min, then add 5 g of multivesicular liposomes loaded with L-methionylglycine-tannic acid and oregano essential oil and mix evenly to prepare solution A; S2. Weigh 0.6 g of geniposide and 1.5 g of bamboo leaf flavonoids, add 97.9 g and dissolve evenly at 75 ° C to obtain solution B; S3. 2 g of hydroxycucurbituril and 12 g of phenyldiboronic acid were dissolved in 40 mL of ethanol, treated at 40 °C for 3 h, and vacuum dried to obtain boronate bond-modified hydroxycucurbituril; S4. Add 98 g of ultrapure water to 2 g of hydroxycucurbituril modified with borate bond, and ultrasonicate at room temperature for 45 min to obtain solution C. S5. Evenly mix 60 g of solution A and 60 g of solution B, add 40 g of solution C, stir at room temperature for 60 min, cast into film, and vacuum dry at 50°C for 6 h to obtain the fresh-keeping and antibacterial material. Example 10 A method for preparing a fresh-keeping and antibacterial material based on food freshness indication comprises the following steps: S1. Weigh 3 g of thorny gum and add 97 g of water to mix evenly, then add 8 g of furan activated by McBride's acid and 3 g of high methoxy pectin nanoparticles, stir at 30 ° C and 200 rpm for 25 min, then add 10 g of multivesicular liposomes loaded with L-methionylglycine-tannic acid and oregano essential oil and mix evenly to prepare solution A; S2. Weigh 0.4 g of geniposide and 1.5 g of bamboo leaf flavonoids, add 98.1 g and dissolve evenly at 75 ° C to obtain solution B; S3. 2 g of hydroxycucurbituril and 12 g of phenyldiboronic acid were dissolved in 40 mL of ethanol, treated at 40 °C for 3 h, and vacuum dried to obtain boronate bond-modified hydroxycucurbituril; S4. Add 98 g of ultrapure water to 2 g of hydroxycucurbituril modified with borate bond, and ultrasonicate at room temperature for 45 min to obtain solution C. S5. Evenly mix 60 g of solution A and 60 g of solution B, add 40 g of solution C, stir at room temperature for 60 min, cast into film, and vacuum dry at 50°C for 6 h to obtain the fresh-keeping and antibacterial material. Embodiment 11 A method for preparing a fresh-keeping and antibacterial material based on food freshness indication comprises the following steps: S1. Weigh 3 g of thorny gum and add 97 g of water to mix evenly, then add 8 g of furan activated by McBride's acid and 3 g of high methoxy pectin nanoparticles, stir at 30 ° C and 200 rpm for 25 min, then add 10 g of multivesicular liposomes loaded with L-methionylglycine-tannic acid and oregano essential oil and mix evenly to prepare solution A; S2. Weigh 0.6 g of geniposide and 1.5 g of bamboo leaf flavonoids, add 97.9 g and dissolve evenly at 75 ° C to obtain solution B; S3. 2 g of hydroxycucurbituril and 12 g of phenyldiboronic acid were dissolved in 40 mL of ethanol, treated at 40 °C for 3 h, and vacuum dried to obtain boronate bond-modified hydroxycucurbituril; S4. Add 98 g of ultrapure water to 2 g of hydroxycucurbituril modified with borate bond, and ultrasonicate at room temperature for 45 min to obtain solution C. S5. Evenly mix 60 g of solution A and 60 g of solution B, add 60 g of solution C, stir at room temperature for 60 min, cast into film, and vacuum dry at 50°C for 6 h to obtain the fresh-keeping and antibacterial material. Comparative Example 1 The difference between this comparative example and Example 6 is that the hydroxycucurbituril modified with boronate bond is not used for embedding, and geniposide and bamboo leaf flavonoids are not added. A method for preparing a fresh-keeping and antibacterial material based on food freshness indication comprises the following steps: S1. Weigh 3 g of thorny gum and add 97 g of water to mix evenly, then add 8 g of furan activated by McBride's acid and 3 g of high methoxy pectin nanoparticles, stir at 30 ° C and 200 rpm for 25 min, then add 10 g of multivesicular liposomes loaded with L-methionylglycine-tannic acid and oregano essential oil and mix evenly to prepare solution A; S2. The solution A was cast into a film, and vacuum dried at 50°C for 6 hours to obtain a fresh-keeping and antibacterial material. Comparative Example 2 The difference between this comparative example and Example 6 is that the taro gum modified with McLaughlin's acid activated furan and high methoxy pectin nanoparticles is not used for embedding, and multivesicular liposomes loaded with L-methionylglycine-tannic acid and oregano essential oil are not added. A method for preparing a food preservation and antibacterial material comprises the following steps: S1. Weigh 0.6 g of geniposide and 1.5 g of bamboo leaf flavonoids, add 97.9 g and dissolve evenly at 75 ° C to obtain solution B; S2. 2 g of hydroxycucurbituril and 12 g of phenyldiboronic acid were dissolved in 40 mL of ethanol, treated at 40 °C for 3 h, and vacuum dried to obtain boronate bond-modified hydroxycucurbituril; S3. Add 98 g of ultrapure water to 2 g of hydroxycucurbituril modified with borate bond, and ultrasonicate at room temperature for 45 min to obtain solution C. S4. Evenly mix 60 g of solution B and 40 g of solution C, stir at room temperature for 60 min, cast into film, and vacuum dry at 50°C for 6 h to obtain the fresh-keeping and antibacterial material. Comparative Example 3 The difference between this comparative example and Example 6 is that geniposide and bamboo leaf flavonoids are not added. A method for preparing a fresh-keeping and antibacterial material based on food freshness indication comprises the following steps: S1. Weigh 3 g of thorny gum and add 97 g of water to mix evenly, then add 8 g of furan activated by McBride's acid and 3 g of high methoxy pectin nanoparticles, stir at 30 ° C and 200 rpm for 25 min, then add 10 g of multivesicular liposomes loaded with L-methionylglycine-tannic acid and oregano essential oil and mix evenly to prepare solution A; S2. 2 g of hydroxycucurbituril and 12 g of phenyldiboronic acid were dissolved in 40 mL of ethanol, treated at 40 °C for 3 h, and vacuum dried to obtain boronate bond-modified hydroxycucurbituril; S3. Add 98 g of ultrapure water to 2 g of hydroxycucurbituril modified with borate bond, and ultrasonicate at room temperature for 45 min to obtain solution C. S4. Evenly mix 60 g of solution A and 40 g of solution C, stir at room temperature for 60 min, cast into film, and vacuum dry at 50°C for 6 h to obtain the fresh-keeping and antibacterial material. Comparative Example 4 The difference between this comparative example and Example 6 is that multivesicular liposomes are not used to load L-methionylglycine-tannic acid and oregano essential oil. A method for preparing a fresh-keeping and antibacterial material based on food freshness indication comprises the following steps: S1. Weigh 3 g of thorny gum and add 97 g of water and mix well, then add 8 g of McBride's acid activated furan and 3 g of high methoxy pectin nanoparticles, stir at 30 ° C, 200 rpm for 25 min, then add 10 g of L-methionyl glycine-oregano essential oil solution and mix well to obtain solution A; S2. Weigh 0.6 g of geniposide and 1.5 g of bamboo leaf flavonoids, add 97.9 g and dissolve evenly at 75 ° C to obtain solution B; S3. 2 g of hydroxycucurbituril and 12 g of phenyldiboronic acid were dissolved in 40 mL of ethanol, treated at 40 °C for 3 h, and vacuum dried to obtain boronate bond-modified hydroxycucurbituril; S4. Add 98 g of ultrapure water to 2 g of borate-modified hydroxycucurbituril and ultrasonicate at room temperature for 45 min to obtain solution C; S5. 60 g of solution A and 60 g of solution B were mixed, and then 40 g of solution C was added and stirred at room temperature for 60 min, cast into a film, and vacuum dried at 50 ° C for 6 h to obtain a fresh-keeping antibacterial material; The preparation method of the L-methionylglycine-oregano essential oil solution comprises the following steps: Step 1. Weigh 4 g L-methionylglycine and 6 g tannic acid, add 90 g water and dissolve evenly to prepare L-methionylglycine solution; Step 2. Weigh 4 g of oregano essential oil, add 96 mL of ethanol and dissolve evenly to prepare an oregano essential oil solution; Step 3. 80 g of L-methionylglycine solution and 120 g of oregano essential oil solution were mixed and ultrasonicated for 20 min to prepare L-methionylglycine-oregano essential oil solution. Performance Testing (1) Mechanical properties The tensile strength (TS) and elongation at break (EAB) of Examples 6-11 and Comparative Examples 1-4 were measured using a universal material testing machine. The film samples were cut into 70 mm×10 mm rectangular strips with an initial clamping spacing of 40 mm and a tensile rate of 200 mm / min. (2) Antioxidant properties Weigh 0.05g of composite membrane sample, soak it in 3mL of anhydrous ethanol for 24h, then take 2mL of membrane sample soaking solution, mix it with 2mL of DPPH solution (0.1mmol / L), and let it stand in the dark for 1h. Measure the absorbance of the solution at 517nm, use anhydrous ethanol as blank control, and calculate the DPPH free radical scavenging rate. The formula is DPPH free radical scavenging rate (%) = (A 0 -A 1 ) / A 1 × 100%, where A 0 is the absorbance of the blank control, A 1 is the absorbance of the sample. (3) Antibacterial activity Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) were selected for testing to determine the antibacterial activity of Examples 6-11 and Comparative Examples 1-4. 100 μL was taken and diluted to 10 6 CFU / mL of bacterial solution was evenly spread on the surface of TSA nutrient agar medium, and then a UV-sterilized membrane disc (6 mm in diameter) was fixed on the medium and cultured at 37°C for 24 h. The diameter of the inhibition zone was observed and measured. Table 2 Tensile strength, elongation at break, DPPH free radical scavenging rate and antibacterial activity of Examples 6-11 and Comparative Examples 1-4 As shown in Table 2, the tensile strength, elongation at break, DPPH free radical scavenging rate and antibacterial activity of Examples 6-11 are better than those of Comparative Examples 1-4, among which Example 6 has the best effect, indicating that the multivesicular liposomes encapsulating L-methionylglycine and oregano essential oil can reduce the influence of polar steric hindrance between hydrophilic and hydrophobic substances, and avoid the violent collision between the two in the material structure, which leads to the reduction of mechanical properties; at the same time, the gel network structure formed by the thorny gum is embedded with multivesicular liposomes, which can make the multivesicular liposomes loaded with L-methionylglycine-tannic acid and oregano essential oil evenly distributed in the material. Inside the material, geniposide and bamboo leaf flavonoids can also be combined in the gel network of taro gum, and combine with the hydrophilic groups at the head of multivesicular liposomes to strengthen the structural strength and stability between aggregates. The aggregates are embedded in the interior of cucurbituril and interact with the groups inside cucurbituril to further strengthen the mechanical strength of the structure. In addition, the embedding of multivesicular liposomes and taro gum gel network can provide a good structural basis for L-methionylglycine, oregano essential oil, geniposide and bamboo leaf flavonoids to exert their effects, ensuring the stable exertion of antioxidant and antibacterial effects without being affected by external conditions. (4) Application of Example 6 and Comparative Examples 1-4 in Preserving Chicken Fresh chicken breast was cut into 20 g pieces under a sterile environment, wrapped with sterilized fresh-keeping and antibacterial materials and stored in a refrigerator at 4°C. Samples were taken at 0, 3, 6, 9, 12 and 15 days to measure the total colony count, pH, thiobarbituric acid reactant value (TBA) and volatile basic nitrogen (TVB-N) of the chicken. The chicken stored for 15 days was sensory evaluated. ① Total colony count: refer to GB4789.2-2022 "Determination of total colony count in food microbiology" to determine the total colony count of chicken; ② pH value: weigh 5g of chicken sample in a centrifuge tube, add 50mL of deionized water and mix and homogenize for 60s, then use a pH meter to determine its pH value; ③Thiobarbituric acid reactant value (TBA): refer to GB5009.181-2016 "National Food Safety Standard Determination of Malondialdehyde in Food" to determine the TBA value of chicken; ④ Volatile basic nitrogen (TVB-N): Refer to GB5009.228-2016 "National Food Safety Standard Determination of Volatile Basic Nitrogen in Food", and use the microdiffusion method to determine the TVB-N content of chicken; ⑤ Sensory evaluation: The sensory evaluation of chicken was conducted with reference to GB2707-2016 "National Food Safety Standard for Fresh (Frozen) Livestock and Poultry Products". The evaluation team consisted of 10 people (5 men and 5 women) and used a 9-point scoring method to evaluate the color, smell, elasticity, viscosity and overall acceptability of the chicken. 9 means "excellent" and 1 means "very poor". Depend on Figure 1 , Figure 2 , Figure 3 , Figure 4 and Figure 5 It can be seen that in the fresh-keeping and antibacterial materials prepared in Example 6 and Comparative Examples 1-4, the fresh-keeping and antibacterial materials prepared in Example 6 were better than Comparative Examples 1-4 in terms of total colony count, TBA and TVB-N during chicken storage, and the sensory quality indicators of chicken stored for 15 days were greater than 5 points, which was within an acceptable range, indicating that anaerobic glycolysis occurred in the early stage of chicken storage, producing a large amount of organic acids such as lactic acid, resulting in a decrease in the pH of the chicken. The decrease in pH will cause the borate bonds in the hydroxycucurbituril modified with borate bonds in the outermost structure of the fresh-keeping and antibacterial materials to be affected by acidic ions. The action breaks, changes the inclusion structure of hydroxycucurbituril, and releases geniposide and bamboo leaf flavonoids (first stage release); both geniposide and bamboo leaf flavonoids can inhibit the growth and reproduction of harmful microorganisms and the generation of harmful substances, scavenge free radicals to prevent the fat in the chicken from oxidizing, and geniposide cross-links with the protein in the chicken to form a stable network structure, reducing the water loss of the chicken during storage. In addition, bamboo leaf flavonoids can also react with acidic substances to adjust the pH value of food, keep the food in a suitable acid-base environment, and ensure the freshness of the food. When the antibacterial and antioxidant effects of geniposide and bamboo leaf flavonoids released in the first stage are over, the protein in the chicken will be metabolized by pathogenic microorganisms to produce volatile organic amines. The organic amines dissolve in the chicken to produce alkaline groups, which increase the pH of the chicken. Because the boronate bond is dynamically reversible, it can be reconstructed after the release of geniposide and bamboo leaf flavonoids to continue to encapsulate the remaining multivesicular liposomes. However, when the pH rises, the boronate bond is attacked by the alkaline groups and breaks again, accompanied by the volatile organic amine index. The ring opening of the indicator substance McBride's acidified furan causes the stability of the gel network structure of the thorny gum to decrease, releasing multivesicular liposomes encapsulating L-methionylglycine and oregano essential oil. The glycine group in L-methionylglycine can competitively inhibit the synthesis site of the key enzyme in the synthesis of volatile organic amines, change the conformation of the enzyme and reduce the catalytic activity of the enzyme. The antibacterial components in oregano essential oil inhibit the growth and reproduction of microorganisms that produce key enzymes in the synthesis pathway of volatile organic amines, thereby ensuring the fresh quality of the chicken and extending the storage time of the chicken. (5) Application of Example 6 and Comparative Examples 1-4 in Preserving Fresh-cut Apples The processed fresh apples were cut into uniform apple pieces under a sterile environment, and all samples were wrapped with sterilized fresh-keeping and antibacterial materials and stored in a refrigerator at 4°C. Samples were taken at 0 days, 3 days, 6 days, 9 days, 12 days, and 15 days, and the total colony count, pH value, browning index, and hardness of the apple slices were measured. A sensory evaluation was also conducted on the apple slices stored for 15 days. ① Total colony count: refer to GB4789.2-2022 "Determination of total colony count in food microbiology examination" to determine the total colony count of apple slices; ② pH value: Weigh 5g of apple slices, chop them completely and pour them into a 100mL Erlenmeyer flask. Add 50mL of normal saline and place them on a magnetic stirrer for 30min. Then filter and measure the pH value with a pH meter. ③ Browning index (BI): Use a handheld colorimeter to measure L*, a* and b* of the cross section of the apple slices and calculate the browning index; ④Hardness: The hardness of the apple slices was measured using the P5 cylindrical test probe of the texture analyzer. The test conditions were: compression ratio 30%, interval time between two times 3s, trigger force 5g, speed before, test and after test 3mm / s, displacement 10mm; ⑤ Sensory evaluation: The evaluation panel consisted of 10 people (5 males and 5 females). A 9-point scoring method was used to evaluate the apple slices in terms of color, smell, hardness and overall acceptability, with 9 representing "excellent" and 1 representing "poor". Depend on Figure 6 , Figure 7 , Figure 8 , Fig. 9 and Fig.10 It can be seen that in the fresh-cut apple preservation storage test of the fresh-cut apple prepared by Example 6 and Comparative Examples 1-4, the total colony count, BI and hardness of the fresh-cut apple prepared by Example 6 during storage were better than those of Comparative Examples 1-4, and the sensory quality indicators of the fresh-cut apples after 15 days of storage were greater than those of Comparative Examples 1-4, indicating that the fresh-cut apples produce CO by aerobic respiration in the early stage of storage. 2 , CO 2It dissolves in water to form carbonic acid, and the polymerization of acidic substances causes the pH value of apples to decrease. The decrease in pH value will cause the borate bonds in the borate-modified hydroxycucurbituril in the outermost structure of the fresh-keeping and antibacterial material to break under the action of acidic ions, changing the inclusion structure of hydroxycucurbituril and releasing geniposide and bamboo leaf flavonoids (first stage release); geniposide and bamboo leaf flavonoids inhibit the growth of harmful microorganisms, and geniposide interacts with polysaccharides in apples to form a stable network structure to ensure the texture of fresh-cut apples. In addition, bamboo leaf flavonoids can also react with acidic substances to adjust the pH value of apples, keep apples in a suitable acid-base environment, and ensure the freshness of apples. When the effects of geniposide and bamboo leaf flavonoids released in the first stage are over, the oxygen in the apple packaging is completely consumed, and anaerobic respiration begins to produce substances such as ethanol, as well as oxidative degradation of organic acids, causing the pH of the apple to rise, causing the dynamically reversible borate bonds to be attacked by alkaline groups and broken again, and the high methoxy pectin nanoparticles embedded in the taro gum network are decomposed by the pectinase in the apple, causing the stability of the taro gum gel network structure to decrease, releasing multivesicular liposomes that embed tannic acid and oregano essential oil. Tannic acid and oregano essential oil can competitively inhibit the active sites of pectinase, change the conformation of the enzyme and reduce the catalytic activity of the enzyme, thereby ensuring the freshness of the fresh-cut apples and extending the storage time. The above is only a preferred embodiment of the present invention and does not limit the present invention in any form. Any technician familiar with the art can make many possible changes and modifications to the technical solution of the present invention by using the above disclosed methods and technical contents without departing from the spirit and technical solution of the present invention, or modify it into an equivalent embodiment of equivalent changes. Therefore, any simple modification, equivalent replacement, equivalent change and modification made to the above embodiments according to the technical essence of the present invention without departing from the content of the technical solution of the present invention still falls within the scope of protection of the technical solution of the present invention.

Claims

1. A method for preparing a fresh-keeping and antibacterial material based on food freshness indication, characterized in that: The following steps are involved: S1. Preparation of multivesicular liposomes loaded with L-methionylglycine-tannic acid and oregano essential oil; S2. Weigh 1-5wt% of thorny gum and add water to mix evenly, then add McBride's acid activated furan and high methoxy pectin nanoparticles, stir for 15-30min at 25-45°C and 200-300rpm, then add multivesicular liposomes loaded with L-methionylglycine-tannic acid and oregano essential oil and mix evenly to obtain solution A; S3. Weigh 0.2-0.8wt% geniposide and 0.1-0.2wt% bamboo leaf flavonoids and dissolve them uniformly at 60-75°C to obtain solution B; S4. Add ultrapure water to 1-3 wt % borate-modified hydroxycucurbituril, and ultrasonicate at room temperature for 30-60 min to obtain solution C; S5. Mix solution A and solution B evenly, add solution C and stir at room temperature for 45-60 minutes, cast into a film, and vacuum dry to obtain a fresh-keeping and antibacterial material.

2. The method for preparing a fresh-keeping and antibacterial material based on food freshness indication according to claim 1, characterized in that: The method for preparing multivesicular liposomes loaded with L-methionylglycine-tannic acid and oregano essential oil in step S1 comprises the following steps: Step 1. Weigh 3-5wt% L-methionylglycine and 4-8wt% tannic acid, add water and dissolve them evenly to prepare an L-methionylglycine-tannic acid solution; Step 2. Weigh 2-6 wt% of oregano essential oil, add ethanol to dissolve evenly, and prepare an oregano essential oil solution; Step 3. The L-methionylglycine-tannic acid solution and the oregano essential oil solution are mixed in a ratio of (1-4):(2-5), and ultrasonically treated for 15-20 minutes to obtain a mixed solution; Step 4. Phosphatidylcholine and cholesterol are mixed in a ratio of 1:(2-5), dissolved in ethanol and rotary evaporated to obtain a liposome membrane, and then 10-20wt% of the mixed solution is added, and microfiltration is performed at 5000-7000rpm for 30-45min to obtain multivesicular liposomes loaded with L-methionylglycine-tannic acid and oregano essential oil.

3. The method for preparing a fresh-keeping and antibacterial material based on food freshness indication according to claim 1, characterized in that: In the step S2, the amount of the furan activated by McBride's acid added is 5-10 wt %, and the amount of the high methoxyl pectin nanoparticles added is 1-3 wt %.

4. The method for preparing a fresh-keeping and antibacterial material based on food freshness indication according to claim 3, characterized in that: The preparation method of the high methoxy pectin nanoparticles comprises dissolving the high methoxy pectin in an acetic acid buffer, adjusting the pH to 4-5, heating at 80-90° C. for 15-30 minutes, immediately immersing in an ice water bath and freeze drying to obtain the high methoxy pectin nanoparticles.

5. The method for preparing a fresh-keeping and antibacterial material based on food freshness indication according to claim 1, characterized in that: The amount of multivesicular liposomes loaded with L-methionylglycine-tannic acid and oregano essential oil added in step S2 is 5-15 wt %.

6. The method for preparing a fresh-keeping and antibacterial material based on food freshness indication according to claim 1, characterized in that: The preparation method of the boronate bond-modified hydroxycucurbituril in step S4 is to dissolve the hydroxycucurbituril and phenyldiboronic acid in ethanol in a ratio of 1:(4-8), treat at 30-40° C. for 2-4 hours, and vacuum dry to obtain the boronate bond-modified hydroxycucurbituril.

7. The method for preparing a fresh-keeping and antibacterial material based on food freshness indication according to claim 1, characterized in that: In step S5, the ratio of solution A, solution B and solution C is (1-5):(2-4):(1-3).

8. The method for preparing a fresh-keeping and antibacterial material based on food freshness indication according to claim 1, characterized in that: The vacuum drying conditions in step S5 are a drying temperature of 40-50° C. and a drying time of 4-6 hours.

9. A fresh-keeping and antibacterial material based on food freshness indication prepared according to the method according to any one of claims 1 to 8.

10. Use of the freshness-preserving and antibacterial material based on food freshness indication according to claim 9 in improving food storage quality.

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