Metal-polyphenol coordination color development system and application thereof in meat freshness monitoring

Abstract

The invention discloses a metal-polyphenol coordination color development system and application thereof in meat freshness monitoring, and belongs to the technical field of intelligent monitoring, a preparation method of the metal-polyphenol coordination color development system comprises the steps that S1, a metal salt solution and a polyphenol solution are mixed, pH is adjusted, and a metal-polyphenol colorimetric solution is obtained; and S2, loading the metal-polyphenol colorimetric solution on a base material, drying and cutting to obtain the metal-polyphenol amine response colorimetric device. According to the metal-polyphenol colorimetric material disclosed by the invention, the defects of potential toxicity, single-stage color change, narrow color change range, single color change and the like of a traditional chemical pigment are overcome, and the problems of low sensitivity, poor stability, high cost, complicated preparation process and the like of a natural pigment are solved; the polyphenols and the metals can be recycled from plant wastes or industrial processing by adopting a water-soluble extraction method, so that the method has good economic benefits and is more environment-friendly, and the prepared materials can be recycled.

Description

Technical Field

[0001] The present invention relates to the field of intelligent detection technology, and in particular to the application of a metal-polyphenol coordination color development system in meat freshness monitoring. Background Art

[0002] Although the shelf life of food is described on food packaging, considering the complexity of the storage environment, the shelf life is often too cautious, resulting in food being edible outside the shelf life, which leads to a lot of waste. At the same time, fresh meat products are often subject to changes in environmental temperature, such as repeated entry and exit from the refrigerator, which makes fresh meat products easily spoiled and corrupted, which seriously threatens human health and social stability. Traditionally, the detection of the freshness of meat products mainly relies on chemical titration, chromatography and electrochemical detection. The complexity, professionalism, time lag and impact on the environment of these methods are no longer in line with the current development trend. Therefore, it is necessary to develop new materials and technologies for monitoring the freshness of meat products that are non-destructive, online, intelligent and green.

[0003] At present, the research on intelligent monitoring of meat freshness is mainly based on the volatile substances generated during the storage of meat, and the response materials such as pH, TVB-N, oxygen, carbon dioxide, and microorganisms are developed in a targeted manner. The application method focuses on intelligent colorimetric packaging, labels, and other electrical sensing methods. However, highly sensitive colorimetric monitoring materials usually use chemical pigments, and their potential toxicity makes consumers worry about monitoring materials prepared with chemical pigments. In addition, chemical pigments with chemical color change mechanisms usually show disadvantages such as single-stage color change, narrow color change range, and single color change, and the color change is easily affected by external factors such as temperature and humidity. Recent hot research uses natural dyes to prepare colorimetric monitoring of meat freshness, but there are shortcomings such as low sensitivity, poor stability, and high cost. Therefore, natural pigments need to be applied in complex ways such as embedding and loading, which is not conducive to practical operation. Summary of the invention

[0004] In view of the above problems existing in the prior art, the present invention provides an application of a metal-polyphenol coordination color development system in monitoring the freshness of meat. The present invention can solve the disadvantages of traditional chemical pigments such as potential toxicity, single-stage color change, narrow color change range, and single color change, as well as the low sensitivity, poor stability, high cost, and complex preparation process of natural pigments. It is a safe, non-toxic, cheap and efficient monitoring method.

[0005] The technical solution of the present invention is as follows:

[0006] The present invention discloses a metal-polyphenol coordination color development system. The preparation method of the metal-polyphenol coordination color development system is as follows:

[0007] S1, mixing a metal salt solution and a polyphenol solution, adjusting the pH, and obtaining a metal-polyphenol colorimetric solution;

[0008] S2, loading the metal-polyphenol colorimetric solution on the substrate, drying and cutting, and obtaining a metal-polyphenol amine responsive colorimetric device.

[0009] In one embodiment of the present invention, in step S1, the concentration of the metal salt solution is 0.5-50 mM; the concentration of the polyphenol solution is 0.1-20 mM; and the molar ratio of the metal salt to the polyphenol substance in the metal-polyphenol colorimetric solution is 1:5-5:1.

[0010] In one embodiment of the present invention, in step S1, the metal salt is one of the hydrochlorides of zinc, iron, ferrous iron, aluminum, copper, cobalt, manganese, vanadium, molybdenum and nickel, the nitrates of zinc, iron, ferrous iron, aluminum, copper, cobalt, manganese, vanadium, molybdenum and nickel, and the sulfates of zinc, iron, ferrous iron, aluminum, copper, cobalt, manganese, vanadium, molybdenum and nickel.

[0011] In one embodiment of the present invention, the polyphenol is one of anthocyanidin, gallic acid, catechin, caffeic acid, curcumin, protocatechuic aldehyde, epicatechin, epigallocatechin, epigallocatechin gallate (EGCG), tea polyphenols, and tannic acid.

[0012] In one embodiment of the present invention, a certain amount of metal salt and polyphenol are weighed using an analytical balance, placed in beakers respectively, a certain amount of ultrapure water is added to dissolve, and ultrasound is used to accelerate the dissolution. After washing the beaker three times, the volume is fixed to a 250 mL brown volumetric flask to prepare metal salt solutions and polyphenol solutions, respectively, which are stored for later use.

[0013] In one embodiment of the present invention, a metal salt solution and a polyphenol solution are mixed and reacted with aqueous ammonia, and a metal-polyphenol-amine multi-stage competitive coordination color development mechanism is obtained and deduced through a series of characterizations, thereby screening out high-sensitivity, sensitive and low-sensitivity metal-polyphenol combinations.

[0014] In one embodiment of the present invention, 0.2 mL of metal-polyphenol solution is taken, diluted 2-20 times with ultrapure water, and then 0.1 ppm-2000 ppm of ammonia is added, and a series of characterizations such as observation, ultraviolet-visible absorption spectrum, infrared spectrum, Raman spectrum, femtosecond transient absorption spectrum and theoretical calculation are obtained and deduced. The metal-polyphenol-amine multi-stage competitive coordination color development mechanism is obtained and deduced. According to the metal-polyphenol and ammonia reaction intensity shown by the ultraviolet-visible absorption spectrum and the theoretical calculation data, a high-sensitivity (0.1-10 ppm ammonia response), a sensitive (11-200 ppm ammonia response) and a low-sensitivity (201-2000 ppm ammonia response) metal-polyphenol combination is obtained.

[0015] In one embodiment of the present invention, 2 mL of the metal-polyphenol solution is taken, diluted 2-10 times with ultrapure water, and then the pH is adjusted to a range of 3-5 with a 0.1 M sulfuric acid solution to obtain a metal-polyphenol colorimetric solution.

[0016] In one embodiment of the present invention, in step S1, the pH is 3-5.

[0017] In one embodiment of the present invention, in step S2, the substrate is one or more of filter paper, PTFE film, PVDF film, pulp board, cellulose-based film, polyvinyl alcohol, chitosan, sodium alginate, and polysaccharide collagen.

[0018] In one embodiment of the present invention, in step S2, the loading method is one or more of spraying, immersion, filtration, printing, coating, 3D printing, and cross-linking.

[0019] In one embodiment of the present invention, in step S2, the drying conditions are: drying in an oven at 30-60°C for 2-20 min; cutting into labels, patterns or combining into arrays.

[0020] An application of a metal-polyphenol coordination color development system in meat freshness monitoring, and the application method is:

[0021] (1) Establish the curve between TVB-N and storage time of meat freshness index;

[0022] (2) Integrate the metal-polyphenol amine responsive colorimetric device into the meat food packaging, and combine the curve in step (1) to establish the relationship between the color change of the metal-polyphenol amine responsive colorimetric device and the freshness of the meat.

[0023] In one embodiment of the present invention, in step (1), fresh meat is simply processed, placed in a food box, and stored in a constant temperature box at 4-25°C. The TVB-N value of the meat is determined according to national standards, and the meat is evaluated as fresh, sub-fresh, and corrupt according to the TVB-N value, and a curve of the change in meat freshness and storage time is established.

[0024] In one embodiment of the present invention, in step (1), in accordance with GB 5009.228-2016 National Food Safety Standard Determination of Volatile Basic Nitrogen in Food, the TVB-N value of the meat is determined every 2-12 hours using a Kjeldahl nitrogen analyzer (SKD-800, Shanghai Peiou Analytical Instruments Co., Ltd.), and in accordance with GB 2707-2016 National Food Safety Standard Fresh (Frozen) Livestock and Poultry Products, the meat is evaluated as fresh, sub-fresh and corrupt according to the TVB-N value.

[0025] In one embodiment of the present invention, in step (2), the metal-polyphenolamine responsive colorimetric device is attached to a plastic wrap, and then the food plate containing the meat is sealed, or it is attached to the inside of a food box, or it is placed in the food without contacting the food, ensuring that the top of the colorimetric device is transparent and clearly visible, and stored in a 4°C-25°C incubator.

[0026] In one embodiment of the present invention, in step (2), three groups of parallel experiments are performed to ensure that the errors of the three groups of experiments are within an acceptable range.

[0027] An intelligent meat freshness monitoring platform based on a metal-polyphenol network colorimetric sensor array is proposed. Images of the metal-polyphenol network colorimetric sensor array are taken to simulate real-life test scenarios by changing angles and lighting conditions. Each sensor takes about 20 images at each time point. PyTorch is used as the deep learning framework. All experiments are performed on a 48GB NVIDIA A40 GPU with a batch size of 32. During training and testing, the images are resized to 224*224 pixels for input.

[0028] The model uses the ResNet-50 backbone and a three-dimensional Softmax layer to predict the freshness status. The learning rate is set to 0.001 and the model is trained for 100 iterations. The ratio of the training set to the test set in deep learning is 4:1. The number of photos used for each type of meat exceeds 5,000. Combined with the freshness and storage time change curves of the four types of meat, the freshness of the meat is monitored online through image recognition or photo scanning.

[0029] The beneficial technical effects of the present invention are:

[0030] The present invention utilizes metal-phenolic networks (MPNs) which are multivalent coordination bonds induced by pH value, supplements the traditional coordination mechanism of metal-polyphenols in different amine environments, and proposes a multi-stage competitive coordination color development mechanism based on the metal-polyphenol-amine system. Different from the previous color change mechanism of chemical or natural pigments, factors such as the type and valence of coordinated metal ions and the number and position of hydroxyl groups on polyphenols can cause the metal-polyphenols to present rich color changes, making the metal-polyphenols extremely sensitive to amines. The multi-stage competitive coordination mechanism also makes the metal-polyphenol system present multiple color changes as the amine concentration increases, and the response range is relatively wide; at the same time, the coordination bonds formed by the metal-polyphenol network can well avoid the oxidative discoloration of polyphenols, and its strong adhesion also makes it practically applicable through a simple loading method, greatly improving the operability of colorimetric monitoring of meat freshness.

[0031] The present invention can screen suitable metal-polyphenol combinations according to factors such as the variety, quality, and storage environment of meat, and prepare colorimetric monitoring materials in a simple manner, including colorimetric labels, colorimetric test strips, colorimetric gels, colorimetric films, and colorimetric sensor arrays, and monitor the freshness of meat by visual inspection, colorimetric cards, code scanning, electrical sensing, and the like.

[0032] The present invention has high safety, environmental benefits and economic feasibility. In addition, polyphenols and metal salts can be recycled from plant waste or industrial processing by water-soluble extraction, which is economically beneficial and more environmentally friendly, and the prepared materials can be recycled repeatedly. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 This is a graph showing the freshness of beef and pork monitored by the ferric chloride-tannic acid colorimetric label prepared in Example 1 of the present invention.

[0034] Figure 2 This is a color response diagram of the metal-polyphenol colorimetric label prepared in Example 2 of the present invention to ammonia, dimethylamine, and trimethylamine.

[0035] Figure 3 This is a graph showing the effect of metal-polyphenol prepared in Example 2 of the present invention on the freshness of fish meat.

[0036] Figure 4 This is a graph showing the freshness of sea bass meat monitored by the polyvinyl alcohol-chitosan-collagen-ferric chloride-anthocyanin colorimetric film prepared in Example 3 of the present invention.

[0037] Figure 5 This is the mold size of the metal-polyphenol network colorimetric sensor array in Example 4 of the present invention.

[0038] Figure 6 This is the color response of different metal-polyphenols to ammonia in Example 4 of the present invention.

[0039] Figure 7 This is the preparation process of the metal-polyphenol network colorimetric sensor array in Example 4 of the present invention.

[0040] Figure 8 This is a diagram of monitoring meat freshness using the metal-polyphenol network colorimetric array in Example 4 of the present invention.

[0041] Fig. 9 The color change of the ferric chloride-tannic acid network colorimetric sensor array prepared by using other substrates in Example 4 of the present invention and the cost of the colorimetric sensor array using the substrate.

[0042] Fig.10 This is a stability test diagram of ferric chloride-tannic acid after the reaction with ammonia in Example 4 of the present invention.

[0043] Fig.11 This is the metal-polyphenol network colorimetric sensor array convolutional neural network training process and the metal-polyphenol network colorimetric sensor array meat freshness intelligent monitoring platform process in Example 5 of the present invention.

[0044] Fig.12 This is a comparison chart of the life cycle analysis of the metal-polyphenol network colorimetric sensor array meat freshness intelligent monitoring platform in Example 5 of the present invention and the three TVB-N detection methods in the national standard.

[0045] Fig.13 It is a schematic diagram of the color development mechanism and intelligent monitoring of the present invention. DETAILED DESCRIPTION

[0046] The present invention is described in detail below in conjunction with the accompanying drawings and embodiments.

[0047] Example 1

[0048] Application of a metal-polyphenol coordination color development system in meat freshness monitoring comprises the following steps:

[0049] S1, preparing ferric chloride and tannic acid solutions: accurately weigh ferric chloride hexahydrate and tannic acid powders, dissolve them in ultrapure water, and prepare 1 mM and 0.5 mM solutions respectively.

[0050] S2, preparing a ferric chloride-tannic acid mixed solution: taking 4 mL of the above ferric chloride solution, adding 2 mL of tannic acid solution, after thorough mixing, using 0.1 M sulfuric acid solution to adjust the pH of the mixed solution to 3, to obtain a ferric chloride-tannic acid colorimetric solution.

[0051] S3, preparing ferric chloride-tannic acid colorimetric labels: using a hole puncher to punch the filter paper into discs with a diameter of 4 mm, soaking the discs in the above ferric chloride-tannic acid colorimetric solution, absorbing excess liquid, and drying to obtain ferric chloride-tannic acid colorimetric labels.

[0052] S4, monitoring the freshness of meat with ferric chloride-tannic acid colorimetric label: weigh 50g of fresh beef or pork and place it in a culture dish, stick the above label on the inside of the culture dish lid, seal it casually, and place it in a constant temperature incubator at 10℃. Observe the color change of the label every 12 hours, and at the same time determine the TVB-N of the meat in the blank group, establish the relationship between TVB-N value and color change, and thus judge the freshness of beef or pork by the ferric chloride-tannic acid colorimetric label.

[0053] Test results such as Figure 1As shown, the results show that, in this storage environment, the TVB-N measurement data of beef indicates that the beef is fresh within 2 days, second-fresh within 2-2.8 days, and then it will deteriorate and be inedible; in this storage environment, the TVB-N measurement data of pork indicates that the pork is fresh within 2.5 days, second-fresh within 2.5-3.5 days, and then it will deteriorate and be inedible; the corresponding ferric chloride-tannic acid colorimetric label color change can well match the freshness change of beef and pork. By using ImageJ software to extract the label colorimetry and establish the ferric chloride-tannic acid meat freshness colorimetric card, the freshness of beef and pork can be effectively judged.

[0054] Example 2

[0055] Application of a metal-polyphenol coordination color development system in meat freshness monitoring comprises the following steps:

[0056] S1, preparing metal salt and polyphenol solutions: accurately weigh ferric chloride hexahydrate, copper sulfate pentahydrate and tannic acid, EGCG, and anthocyanin powder, dissolve them in ultrapure water, and prepare 1 mM metal salt solution and 0.5 mM polyphenol solution respectively.

[0057] S2, prepare a metal-polyphenol colorimetric solution: take 4 mL of the above ferric chloride solution, add 2 mL of tannic acid solution or 4 mL of ferric chloride solution, add 2 mL of EGCG solution or 4 mL of copper sulfate solution, add 2 mL of tannic acid solution or 4 mL of copper sulfate solution, add 2 mL of EGCG solution or 4 mL of copper sulfate solution, add 2 mL of anthocyanin solution, mix thoroughly, and use 0.1 M sulfuric acid solution to adjust the pH of the mixed solution to 3 to obtain a metal-polyphenol colorimetric solution;

[0058] They are respectively recorded as: a: FeCl3 + tannic acid, b: FeCl3 + EGCG, c: CuSO4 + tannic acid, d: CuSO4 + EGCG, e: CuSO4 + anthocyanin.

[0059] S3, preparation of metal-polyphenol colorimetric labels: soak filter paper in the five solutions described in S2 for 30 seconds, then take it out, dry it, and use a punch to punch the filter paper into discs with a diameter of 4 mm to obtain five metal-polyphenol colorimetric labels.

[0060] S4, metal-polyphenol colorimetric label to monitor meat freshness: weigh 50g of fresh fish meat and place it in a culture dish, stick the above label on the inside of the culture dish lid, seal it casually, and place it in a 10℃ refrigerator. Observe the color change of the label every 12 hours, and at the same time measure the TVB-N of the meat in the blank group, establish the relationship between TVB-N value and color change, and thus judge the freshness of the fish meat by the metal-polyphenol colorimetric label.

[0061] Figure 2The color response diagram of the metal-polyphenol colorimetric label prepared in this example to ammonia, dimethylamine and trimethylamine. The results show that the metal-polyphenol label can change with the concentration of amines.

[0062] Figure 3 This is a graph of monitoring the freshness of fish meat by metal-polyphenol prepared in this example. The results show that in this storage environment, the TVB-N measurement data indicates that beef is fresh within 1.8 days, second fresh within 1.8-2.7 days, and then it is spoiled and inedible; the corresponding five metal-polyphenol colorimetric labels change with the storage time. By using ImageJ software to extract the label color, five metal-polyphenol meat freshness colorimetric cards are established, which can effectively judge the freshness of fish meat.

[0063] Example 3

[0064] Application of a metal-polyphenol coordination color development system in meat freshness monitoring comprises the following steps:

[0065] S1, prepare ferric chloride-anthocyanidin colorimetric solution: accurately weigh ferric chloride hexahydrate and anthocyanidin powder, dissolve them in ultrapure water, and prepare 4mM and 1mM solutions respectively. Take 5mL of the above ferric chloride solution and anthocyanidin solution respectively, mix them thoroughly, and use 0.1M sulfuric acid solution to adjust the pH of the mixed solution to 3 to obtain ferric chloride-anthocyanidin colorimetric solution.

[0066] S2, preparation of polyvinyl alcohol-chitosan-collagen matrix: prepare 120 mL of 3 wt% polyvinyl alcohol solution, place in a 95°C oil bath, stir thoroughly to dissolve, lower the temperature to 60°C, add 20 mL of 1 wt% chitosan solution that has been dissolved, continue stirring for 4 h to obtain a polyvinyl alcohol-chitosan-collagen matrix solution.

[0067] S3, preparation of colorimetric film: cool the above solution to 40°C, add 10 mL of ferric chloride-anthocyanin colorimetric mixed solution, continue stirring for 2 hours, and finally pour into a culture dish, prepare a film by casting method, and place in a 40°C incubator to dry for 48 hours to obtain a polyvinyl alcohol-chitosan-collagen-ferric chloride-anthocyanin colorimetric film.

[0068] S5, polyvinyl alcohol-chitosan-collagen-ferric chloride-anthocyanin colorimetric film monitoring meat freshness: weigh 200g of fresh sea bass meat and place it in a beaker. Cut the above colorimetric film into 2*2cm 2 The square was pasted on the inside of the food box and placed in a 4°C refrigerator. The color change of the film was observed every 24 hours. At the same time, the TVB-N of the fish meat was measured in the blank group, and the relationship between the TVB-N value and the color change was established. The freshness of the sea bass meat was judged by the color of the polyvinyl alcohol-chitosan-collagen-ferric chloride-anthocyanin colorimetric film.

[0069] Figure 4 This is a graph of the freshness of sea bass meat monitored by the polyvinyl alcohol-chitosan-collagen-ferric chloride-anthocyanidin colorimetric film prepared in this example. The results show that the color of the polyvinyl alcohol-chitosan-collagen-ferric chloride-anthocyanidin colorimetric film changes with storage time, but due to the strong binding force between the metal-polyphenol and the substrate, the film is covered so that the contact area with the gas is small and the color change is small. By using ImageJ software, the color change of the colorimetric film can be identified within a certain range to detect the freshness of sea bass meat to a certain extent.

[0070] Example 4

[0071] Application of a metal-polyphenol coordination color development system in meat freshness monitoring comprises the following steps:

[0072] S1, prepare metal-polyphenol colorimetric solution: select high-sensitivity group: ferric chloride metal solution + tannic acid, gallic acid, caffeic acid and catechin polyphenol solution; sensitive group: ferrous chloride metal solution + tannic acid, gallic acid, caffeic acid and catechin polyphenol solution; low-sensitivity group: copper sulfate metal solution + tannic acid, gallic acid, caffeic acid and catechin polyphenol solution. Prepare 10mM metal solution and 2mM polyphenol solution respectively, take 2.5mL of metal and polyphenol solution and mix them thoroughly, and get 12 sets of metal-polyphenol colorimetric solution combinations.

[0073] S2, preparation of metal-polyphenol colorimetric sensor array: Pour the above 5 ml of metal-polyphenol colorimetric solution into a vacuum filtration device equipped with a PTFE membrane. After soaking for 30 seconds, filter it and then put the membrane into an oven at 40°C to dry for 10 minutes. Use a 4 mm diameter puncher to punch holes in the above film, and then arrange them in sequence on a laser-etched plastic sheet to prepare a 3*4 metal-polyphenol network colorimetric sensor array.

[0074] S3, visual monitoring of meat freshness using metal-polyphenol network colorimetric sensor array: Weigh 300g of fresh beef, chicken, fish or shrimp and place it in a transparent food box. Use shadowless glue to fix the metal-polyphenol network colorimetric sensor array in the lid of the food box. Seal the box tightly and store it in a refrigerator at 4°C. Observe the color change of the colorimetric sensor array every 12 hours, and measure the TVB-N of the meat in the blank group at the same time. Establish the relationship between TVB-N value and color change, so as to judge the freshness of meat by the color of the metal polyphenol network colorimetric sensor array.

[0075] Figure 5 is the mold size of the metal-polyphenol network colorimetric sensor array in this embodiment; Figure 6For the color responses of different metal-polyphenols to ammonia in this embodiment, a high-sensitivity group, a sensitive group, and a low-sensitivity group were selected, thereby further constructing a metal-polyphenol network colorimetric sensing array; Figure 7 This is the preparation process of the metal-polyphenol network colorimetric sensor array in this embodiment.

[0076] Figure 8 This is a diagram of the metal-polyphenol network colorimetric array monitoring the freshness of meat in this embodiment. The top row of the array is the high-sensitivity group, the middle row is the sensitive group, and the bottom row is the low-sensitivity group. The results show that for each of the three freshness levels of meat, fresh, sub-fresh, and spoiled, the color of the label in at least one hole of the array changes significantly. For example, when beef changes from sub-fresh to spoiled, the color of the ferric chloride-gallic acid label changes significantly, and the spoilage process of chicken is clearly reflected by ferric chloride-tannic acid and ferric chloride-caffeic acid. This shows that the freshness of meat can be well distinguished by visual methods.

[0077] Fig. 9 The color change of the ferric chloride-tannic acid network colorimetric sensor array prepared by other substrates in this embodiment and the cost of the colorimetric sensor array using this substrate. The results show that using ordinary filter paper and pulp board as the array substrate can significantly reduce the cost and the color change is suitable, which will not affect the monitoring effect.

[0078] Fig.10 The stability test diagram of the ferric chloride-tannic acid combination after the reaction with ammonia in the embodiment. The results show that after the ferric chloride-tannic acid is fumigated with ammonia, it will not fall off whether it is soaked or rinsed with water or ethanol, indicating that the application of metal-polyphenol will not be affected by the storage environment, which is helpful for long-term monitoring of food freshness and has higher safety and accuracy.

[0079] Example 5

[0080] An intelligent monitoring platform for meat freshness using a metal-polyphenol network colorimetric sensor array: According to the above method, every 12 hours, a box is taken out of the refrigerator and images of the metal-polyphenol network colorimetric sensor array are taken in a small studio. The angle and lighting conditions are changed to simulate the test scene in real life. Each sensor takes about 20 images at each time point. PyTorch is used as the deep learning framework, and all experiments are performed on a 48GB NVIDIAA40 GPU with a batch size of 32. During training and testing, the image size is resized to 224*224 pixels for input. The model uses a ResNet-50 backbone and a three-dimensional Soffmax layer to predict the freshness state. The learning rate is set to 0.001, and the model is trained for 100 iterations. The training set and test set in deep learning are in a ratio of 4:1, and the number of photos used for each meat is more than 5000. Combining the freshness and storage time change curves of four meats, the meat freshness is monitored online by image recognition or photo scanning.

[0081] Fig.11 This is the training process of the metal-polyphenol network colorimetric sensor array convolutional neural network and the process of the metal-polyphenol network colorimetric sensor array meat freshness intelligent monitoring platform in this embodiment. The results show that after learning through the convolutional neural network, the accuracy rate is greatly improved, and the accuracy rate of judging the freshness of four kinds of meat reaches 99.83%, among which the accuracy of chicken and shrimp reaches 100%.

[0082] Fig.12 This is a comparison chart of the life cycle analysis of the metal-polyphenol network colorimetric sensor array meat freshness intelligent monitoring platform in this embodiment and the three TVB-N detection methods in the national standard (semi-micro method, Semi-micro; micro-diffusion method, Micro-diffusion; instrumental determination method Automated). The results show that the metal-polyphenol network colorimetric sensor array meat freshness intelligent monitoring platform is lower than other detection methods in seven indicators: abiotic consumption (ADP), acidification potential (AP), global warming potential (GWP), eutrophication potential (EP), human toxicity potential (HTP), photochemical ozone generation potential (POCP) and terrestrial ecotoxicity potential (TETP), indicating that the metal-polyphenol network colorimetric sensor array meat freshness intelligent monitoring platform has better environmental effects.

[0083] Fig.13 This is a schematic diagram of the metal-polyphenol multi-stage competitive coordination color development mechanism process and intelligent monitoring proposed in the present invention.

[0084] The embodiments provided above are not intended to limit the scope of the present invention, and the steps described are not intended to limit the execution order thereof. Those skilled in the art may make obvious improvements to the present invention in combination with existing common knowledge, which also fall within the scope of protection defined by the claims of the present invention.

Claims

1. A metal-polyphenol coordination color development system, characterized in that: The preparation method of the metal-polyphenol coordination color development system is: S1, mixing a metal salt solution and a polyphenol solution, adjusting the pH, and obtaining a metal-polyphenol colorimetric solution; S2, loading the metal-polyphenol colorimetric solution on a substrate, drying and cutting, and obtaining a metal-polyphenol amine responsive colorimetric device.

2. The metal-polyphenol coordination color development system according to claim 1, characterized in that: In step S1, the concentration of the metal salt solution is 0.5-50 mM; the concentration of the polyphenol solution is 0.1-20 mM; and the molar ratio of the metal salt to the polyphenol substance in the metal-polyphenol colorimetric solution is 1:5-5:

1.

3. The metal-polyphenol coordination color development system according to claim 1, characterized in that: In step S1, the metal salt is one of the hydrochlorides of zinc, iron, ferrous iron, aluminum, copper, manganese, vanadium, molybdenum and nickel, the nitrates of zinc, iron, ferrous iron, aluminum, copper, cobalt, manganese, vanadium, molybdenum and nickel, and the sulfates of zinc, iron, ferrous iron, aluminum, copper, cobalt, manganese, vanadium, molybdenum and nickel.

4. The metal-polyphenol coordination color development system according to claim 1, characterized in that: In step S1, the polyphenol is one of anthocyanidin, gallic acid, catechin, caffeic acid, curcumin, protocatechuic aldehyde, epicatechin, epigallocatechin, epigallocatechin gallate, tea polyphenols, and tannic acid.

5. The metal-polyphenol coordination color development system according to claim 1, characterized in that: In step S1, the pH is 3-5.

6. The metal-polyphenol coordination color development system according to claim 1, characterized in that: In step S2, the substrate is one or more of filter paper, PTFE film, PVDF film, pulp board, cellulose-based film, polyvinyl alcohol, chitosan, sodium alginate, and polysaccharide collagen.

7. The metal-polyphenol coordination color development system according to claim 1, characterized in that: In step S2, the loading method is one or more of spraying, immersion, filtration, printing, coating, 3D printing, and cross-linking.

8. An application of the metal-polyphenol coordination color development system according to claim 1 in monitoring the freshness of meat, characterized in that: The application method is: (1) Establish the curve between TVB-N and storage time of meat freshness index; (2) Integrate the metal-polyphenol amine responsive colorimetric device into the meat food packaging, and combine the curve in step (1) to establish the relationship between the color change of the metal-polyphenol amine responsive colorimetric device and the freshness of the meat.

9. The use according to claim 8, characterized in that: In step (1), the fresh meat is simply processed and placed in a food box, which is then stored in a constant temperature box at 4-25°C. The TVB-N value of the meat is determined according to national standards, and the meat is rated as fresh, sub-fresh, and corrupt according to the TVB-N value, and a curve of the change in meat freshness and storage time is established.

10. The use according to claim 8, characterized in that: In step (2), the metal-polyphenolamine responsive colorimetric device is attached to a plastic wrap, and then the food plate containing the meat is sealed, or it is attached to the inside of a food box, or it is placed in the food without contacting the food, ensuring that the top of the colorimetric device is transparent and clearly visible, and stored in a constant temperature box at 4°C-25°C.

Images