Preparation method and application of colorimetric sensor array based on time-temperature indication and pH response dual information fusion

Abstract

The invention discloses a preparation method and application of a colorimetric sensor array based on time-temperature indication and pH response dual information fusion. The colorimetric sensor array is composed of a pH response sensor array and a TTI sensor array, methyl cellulose is adopted as a substrate material, the pH response sensor array uses a mixed indicator prepared from methyl red and bromocresol green according to different proportions as a dye, and the mixed indicator is sensitive to pH and displays different colors in different pH environments. According to the TTI sensor array, HAuCl4 solutions with different concentrations are added into a substrate, L-ascorbic acid is added for a reduction reaction after a label is prepared, and metal nanoparticles are generated to change the color of the label. The colorimetric sensor array not only overcomes the limitation that a single sensor cannot comprehensively monitor the freshness of fruits, but also improves the accuracy of freshness classification through multiple data feedback, and ensures high precision and high reliability of a monitoring system.

Description

Technical Field

[0001] The present invention relates to the technical field of intelligent food packaging, and in particular to a preparation method and application of a colorimetric sensor array based on the dual information fusion of time-temperature indication and pH response. Background Art

[0002] In the field of food quality control, the monitoring of fruit freshness plays a crucial role. Especially in modern agriculture and the food supply chain, the quality status of fruits during storage, transportation, and sales directly affects consumers' health and food safety. Cold chain logistics can effectively delay the ripening and decay process of fruits by maintaining a low-temperature environment during transportation and storage. However, temperature fluctuations, transportation delays, and improper cold chain management often lead to fruit quality losses. Therefore, how to real-time and accurately evaluate whether there are temperature fluctuations during the cold chain process and the freshness of fruits to ensure their best quality before consumption has become a key issue that urgently needs in-depth study.

[0003] Colorimetric sensor arrays can dynamically track the freshness of fruits by detecting color changes caused by chemical reactions (such as acid-base changes or gas release) during fruit storage, showing great potential in fruit quality monitoring. Among them, pH-responsive sensors are widely used because they can monitor changes in environmental pH values to reflect fruit spoilage. However, during the gradual change of fruits from "fresh" to "sub-fresh", due to their weak respiration and less carbon dioxide production, the pH change is not obvious, making it difficult for the sensor to capture this subtle difference. In addition, the accuracy of pH-responsive sensors is also easily affected by environmental factors such as temperature and humidity. For example, the adjustment of the respiration rate of fruits to temperature changes has a lag, which further reduces the ability of the sensor to accurately reflect freshness in a complex storage environment. Therefore, relying solely on pH-responsive colorimetric sensors is difficult to meet the requirements of high-precision freshness monitoring.

[0004] TTI sensors can infer the freshness of fruits to a certain extent by recording the changes in temperature and time during storage. However, the changes in temperature and time are only partial factors affecting fruit freshness and cannot fully reflect the complex internal physiological state of fruits, such as the acceleration of respiration. Therefore, relying solely on TTI sensors is difficult to accurately achieve multi-level freshness judgment or real-time feedback.

[0005] Fruit freshness is affected by a variety of factors. A single-index sensor array is difficult to comprehensively capture the gradual change process of fruits from fresh to spoiled and is also difficult to adapt to the influence of complex environmental factors. Therefore, developing a colorimetric sensor array that combines multiple indicators can provide a more comprehensive and accurate evaluation method and is expected to become an important research direction for solving the problem of fruit freshness monitoring. Summary of the Invention

[0006] In view of the deficiencies of the prior art, the present invention provides a preparation method and application of a colorimetric sensor array based on the dual information fusion of time-temperature indication and pH response. The colorimetric sensor arrays of the present invention all use methylcellulose as the substrate material. Among them, the pH response sensor array uses a mixed indicator configured with methyl red and bromocresol green in different proportions as the dye. The mixed indicator is sensitive to pH and shows different colors in different pH environments. The TTI sensor array adds HAuCl4 solutions with different concentrations to the substrate. After making the label and adding L-ascorbic acid (L-AA), a reduction reaction occurs, generating metal nanoparticles (AuNPs) to change the color of the label. By simultaneously monitoring the temperature-time and pH changes of the environment, the dual sensor array provides more comprehensive information and overcomes the deficiencies of a single indicator. The TTI sensor can effectively monitor the temperature fluctuations and storage time during the cold chain process, while the pH response sensor captures the internal physiological activities of fruits, especially the impact of CO2 generated by respiration on acidity. Using this sensor array for freshness detection on fruits such as mangoes has achieved good results.

[0007] The technical solution of the present invention is as follows:

[0008] A preparation method of a colorimetric sensor array based on the dual information fusion of time-temperature indication and pH response, wherein the colorimetric sensor array is composed of a pH response sensor array and a TTI sensor array; the preparation method includes the following steps:

[0009] (1) Dissolve methylcellulose in distilled water and perform ultrasonic treatment to obtain a substrate solution;

[0010] (2) Prepare HAuCl4 solutions with a concentration of 0.005 - 0.13 g / L, methyl red solutions with a concentration of 0.1 ± 0.05 g / mL, and bromocresol green solutions with a concentration of 0.1 ± 0.05 g / mL;

[0011] (3) Mix the methyl red solution and the bromocresol green solution according to a volume ratio of 1:0.4 - 2.3 to obtain a mixed solution, and then add it to the substrate solution and dry to obtain a pH response sensor array;

[0012] (4) Add the HAuCl4 solution to the substrate solution and dry to obtain a TTI sensor array.

[0013] Further, in step (1), the concentration of methylcellulose in the substrate solution is 25 - 30 g / L; the temperature of dissolution is 50 - 60 °C, the rotation speed is 800 - 1000 rpm, and the time is 1 - 1.2 h.

[0014] Further, in step (1), the frequency of the ultrasound is 40 - 50 kHz, and the time is 50 - 60 min.

[0015] Further, in step (2), the concentration of the HAuCl4 solution is 0.005 g / L, 0.03 g / L, 0.05 g / L, 0.01 g / L or 0.013 g / L.

[0016] Further, in step (3), the volume ratio of the methyl red solution to the bromocresol green solution is 3:7, 4:6, 5:5, 6:4 or 7:3; the volume ratio of the mixed solution to the substrate solution is 1:10.

[0017] Further, in step (3), the drying temperature is 40 - 50 °C, and the time is 24 - 24.5 h.

[0018] Further, in step (4), the volume ratio of the HAuCl4 solution to the substrate solution is 1:50.

[0019] Further, in step (4), the drying temperature is 40 - 50 °C, and the time is 24 - 24.5 h.

[0020] An application of a colorimetric sensor array prepared by the described preparation method, wherein the colorimetric sensor array is applied to evaluate the freshness of fruits.

[0021] The beneficial technical effects of the present invention are as follows:

[0022] (1) The present invention selects methylcellulose (CMC-Na) as the substrate material of the sensor array, which has excellent biocompatibility and environmental friendliness, and can provide good support and protection. Its polymer structure enables it to form a stable thin film in an aqueous solution and effectively avoid the failure of the sensor. The CMC-Na substrate has a strong hydration effect, which can maintain the stability and continuous reaction activity of the sensor. At the same time, by improving the oxygen barrier property of the thin film, the occurrence of oxidation reactions is delayed, thereby enhancing the long-term stability of the sensor. Its good film-forming property and adhesiveness enable the indicator to be evenly dispersed on the surface of the thin film, further improving the sensitivity and response speed of the sensor.

[0023] (2) The present invention selects a mixed indicator of methyl red and bromocresol green. By utilizing its unique pH response characteristics, the sensitivity and monitoring accuracy of the sensor array are significantly improved. Methyl red and bromocresol green have different pKa values, corresponding to different acid-base environments respectively, and can respond rapidly when the internal acidity of fruits changes. Methyl red undergoes a color change in the pH range of 4.4 - 6.2, turning from red to yellow, while bromocresol green changes from yellow to blue in the pH range of 3.8 - 5.4. By optimizing the ratio between methyl red and bromocresol green, the present invention enables these two indicators to cover a wider pH change range, effectively enhancing the ability to detect acid-base changes in fruit freshness monitoring and ensuring high-precision monitoring results.

[0024] (3) The present invention prepares the TTI sensor based on the reduction reaction principle of HAuCl4 solution and L-ascorbic acid. Metal nanoparticles (AuNPs) are generated through this reaction. In this process, L-ascorbic acid acts as a reducing agent, capable of reducing the metal ions (Au 3+ ) in HAuCl4 to metal nanoparticles (AuNPs). Due to their unique surface plasmon resonance (SPR) characteristics, these metal nanoparticles are very sensitive to the absorption and scattering of light and can respond significantly to temperature changes. As the temperature changes, the size and distribution of the metal nanoparticles will change, resulting in changes in their optical properties and color, thereby realizing the dynamic monitoring of temperature. This nanoparticle-based temperature response mechanism ensures the rapid and accurate monitoring of temperature changes during cold chain transportation. By optimizing the concentration of the HAuCl4 solution, the present invention improves the accuracy of the detection results of the TTI sensor array.

[0025] (4) The present invention combines the temperature-time indicator (TTI) with the pH response sensor for the first time to construct a system for multi-dimensional monitoring of fruit freshness. The TTI sensor utilizes the temperature-time accumulation effect to reflect the temperature changes in the cold chain environment through color changes, thereby monitoring the impact of temperature fluctuations during cold chain transportation on fruit freshness. At the same time, the pH response sensor can capture in real time the acidity changes caused by CO2 generated by the respiration of fruits. The combination of the two not only overcomes the limitation that a single sensor cannot comprehensively monitor fruit freshness but also improves the accuracy of freshness classification through multiple data feedback, ensuring the high precision and high reliability of the monitoring system.

[0026] (5) By combining a temperature-time indicator with a pH-responsive sensor, the sensor array of the present invention exhibits obvious comprehensive advantages. First, the TTI sensor can accurately monitor temperature fluctuations in the cold chain environment and feedback the historical cumulative information of temperature changes through color changes; at the same time, the pH-responsive sensor reflects the freshness and physiological state of the fruit by detecting the change of internal acidity of the fruit in real time. Such a dual monitoring mechanism can provide more comprehensive data support and scientific basis for the quality control of fruits. The sensor array not only has excellent stability and response sensitivity, but also can maintain long-term reliability in practical applications, solving the problems of slow response speed and poor sensitivity of single sensors in the prior art, and greatly improving the accuracy and practicality of freshness monitoring. Description of the Drawings

[0027] Figure 1 It is a color change diagram of the TTI sensor array prepared in Example 1 of the present invention at 0 °C.

[0028] Figure 2 It is a color change diagram of the TTI sensor array prepared in Example 1 of the present invention at 10 °C.

[0029] Figure 3 It is a color change diagram of the pH-responsive sensor array prepared in Example 1 of the present invention at different pH values.

[0030] Figure 4 It is a change diagram of CO2 concentration and titratable acidity of mangoes in the fresh-keeping box obtained in Application Example 1 of the present invention during storage.

[0031] Figure 5 It is a change diagram of total soluble solids and weight loss of mangoes in the fresh-keeping box obtained in Application Example 1 of the present invention during storage.

[0032] Figure 6 It is a change diagram of sensory evaluation of mangoes in the fresh-keeping box obtained in Application Example 1 of the present invention during storage. Detailed Embodiments

[0033] The present invention will be specifically described below in conjunction with the drawings and embodiments.

[0034] In the following embodiments of the present invention, the ultrasonic instrument used for ultrasonic treatment is purchased from Shanghai Zhixin Instrument Co., Ltd., model DL-360E, and the power is 50W.

[0035] Example 1

[0036] A preparation method of a colorimetric sensor array based on the dual information fusion of time-temperature indication and pH response includes the following steps:

[0037] (1) Dissolve 3 g of methylcellulose in 100 mL of distilled water and perform ultrasonic treatment to obtain a substrate solution with a concentration of 30 g / L;

[0038] (2) Prepare HAuCl4 solutions with concentrations of 0.005 g / L, 0.03 g / L, 0.05 g / L, 0.01 g / L, and 0.013 g / L in sequence; prepare a methyl red solution with a concentration of 0.1 g / mL and a bromocresol green solution with a concentration of 0.1 g / mL for standby;

[0039] (3) Mix the prepared methyl red solution and bromocresol green solution in sequence according to volume ratios of 3:7, 4:6, 5:5, 6:4, and 7:3 to obtain mixed solutions with different volume ratios. Take 10 mL of each of the prepared mixed solutions and add them to 100 mL of the substrate solution, and dry at 40 °C for 24 h to obtain a pH-responsive sensor array;

[0040] (4) Take 2 mL of HAuCl4 solutions with different concentrations and add them to 100 mL of the substrate solution, and dry at 40 °C for 24 h to obtain a TTI sensor array.

[0041] Application Example

[0042] An application of a colorimetric sensor array based on the dual information fusion of time-temperature indication and pH response. Apply the colorimetric sensor array prepared in Example 1 to the detection of mango freshness, including the following steps:

[0043] (1) Select mangoes without damage, flaws and close to the mature state. After washing the fruits, peel and slice the mangoes, and divide each portion of the fruit into 200 g portions;

[0044] (2) Place each portion of the fruit in a fresh-keeping box, attach the pH-responsive sensor array and the TTI sensor array (1 mL of a 100 mM L-ascorbic acid solution is added to the TTI sensor array) to the inner side of the fresh-keeping box lid, ensuring that they are above the fruit;

[0045] (3) Stick a layer of breathable filter paper on the surface of the sensor array;

[0046] (4) Place all the fresh-keeping boxes in a constant temperature environment of 15 °C for storage, and lay them flat in sequence to avoid stacking.

[0047] Comparative Example 1

[0048] A preparation method of an enzyme-based TTI sensor, including the following steps:

[0049] (1) Prepare a phosphate buffer solution with a pH of 7.4.

[0050] (2) Mix 6.67 ml of copper sulfate solution with a concentration of 120 mmol / L with 500 mL of phosphate buffer solution (pH 7.4) of amylase with different mass concentrations (0.025 mg / mL, 0.05 mg / mL, 0.075 mg / mL, 0.1 mg / mL, 0.2 mg / mL, 0.5 mg / mL) to obtain an amylase-Cu mixed solution.

[0051] (3) Leave the mixed solution obtained in step (2) to stand in a water bath at 25 °C for 3 days, then centrifuge it, wash the precipitate with high-purity water, and freeze-dry it to obtain amylase@Cu hybrid nanoflower materials (mark the corresponding amylase@Cu hybrid nanoflowers according to the increasing concentration of amylase in the phosphate buffer solution, namely NF-1, NF-2, NF-3, NF-4, NF-5, NF-6).

[0052] (4) Dissolve 1 g of natural amylase and 1 g of amylase@Cu nanoflowers (NF-1, NF-2, NF-3, NF-4, NF-5, NF-6) in 1 L of phosphate buffer solution with pH 7.4 respectively.

[0053] (5) Prepare 15 mL of soluble starch solutions with different mass concentrations (10 g / L, 20 g / L, 30 g / L, 40 g / L, 50 g / L) in sequence, add 4.5 mL of iodine solution with a concentration of 1 g / L and 40 mg of amylase@Cu nanoflowers, measure the change in absorbance, and determine that the optimal mass concentration of soluble starch is 40 g / L.

[0054] (6) Prepare 4.5 mL of iodine solutions with different mass concentrations (0.5 g / L, 0.75 g / L, 1.0 g / L, 1.25 g / L, 1.5 g / L) in sequence. Set 6 groups for each concentration of iodine solution. Add 15 mL of soluble starch solution with a concentration of 40 g / L to each group. Add NF-1, NF-2, NF-3, NF-4, NF-5, NF-6 amylase@Cu nanoflowers (the addition amount is 40 mg each) to the iodine solutions with the same concentration respectively, measure the change in absorbance, and determine that the optimal mass concentration of iodine solution is 1.0 g / L.

[0055] (7) Prepare 36 test tubes, and add 15 mL of a 40 g / L soluble starch solution and 4.5 mL of a mixed solution of 1.0 g / L iodine solution to each tube. Add 10 mg of NF-1, NF-2, NF-3, NF-4, NF-5, and NF-6 amylase@Cu nanoflowers to the 1st - 6th tubes in sequence; add 20 mg of NF-1, NF-2, NF-3, NF-4, NF-5, and NF-6 amylase@Cu nanoflowers to the 7th - 12th tubes in sequence; add 30 mg of NF-1, NF-2, NF-3, NF-4, NF-5, and NF-6 amylase@Cu nanoflowers to the 13th - 18th tubes in sequence; add 40 mg of NF-1, NF-2, NF-3, NF-4, NF-5, and NF-6 amylase@Cu nanoflowers to the 19th - 24th tubes in sequence; add 50 mg of NF-1, NF-2, NF-3, NF-4, NF-5, and NF-6 amylase@Cu nanoflowers to the 25th - 30th tubes in sequence; add 60 mg of NF-1, NF-2, NF-3, NF-4, NF-5, and NF-6 amylase@Cu nanoflowers to the 31st - 36th tubes in sequence, thus obtaining an enzyme-based TTI sensor.

[0056] The temperature applicable range of the enzyme-based TTI sensor prepared in this comparative example is limited by enzyme activity (5 - 35 °C), and extreme temperatures may cause failure; the activation energy coverage range is relatively narrow (14.84 - 33.03 kJ / mol), and it is only applicable to foods with specific spoilage mechanisms such as enzymatic reactions and lipid oxidation; the nanoflower preparation process is complex, time-consuming, and has a low enzyme loading rate, resulting in a high cost; and it is not easy to form a film.

[0057] Comparative Example 2

[0058] A preparation method of an electrical signal-based TTI sensor includes the following steps:

[0059] (1) Use p-type crystalline silicon (Topsil Semiconductor Materials SA, USA), boron-doped,

[100] crystal orientation, resistivity 1 - 5 mΩ·cm, for preparing a distributed Bragg reflector (DBR).

[0060] (2) Use the crystalline silicon as the anode of an electrochemical cell, and use a mixed solution prepared by mixing hydrogen fluoride (50%) and ethanol in a volume ratio of 1:2 as the electrolyte.

[0061] (3) Perform anodic oxidation using a dual current density (59 mA / cm 2 and 106 mA / cm 2 ) to form porosities of 78% and 86% respectively, thereby obtaining a multi-layer structure (DBR) with alternating porosities. The designed reference wavelength is 530 nm.

[0062] (4) Place the DBR on the temperature control board with a temperature resolution of 0.1 K.

[0063] (5) Deposit a layer of polymer (polyvinyl acetate, pEVA) on the surface of the DBR and collect the reflection spectrum regularly (every 2 seconds).

[0064] (6) By adjusting the pore structure (rmin and rmax) of the DBR and the properties of the polymer (such as activation energy), the response characteristics of the sensor can be fine-tuned to meet the requirements of different food and drug quality monitoring.

[0065] Although the electro-signal type TTI sensor prepared in this comparative example has a high sensitivity, its operating temperature range may be limited by the activation energy of the polymer, resulting in inaccurate responses at extreme temperatures; the pore structure may be unstable under long-term or extreme environments, affecting the sensor performance; and it is difficult to calibrate and standardize, which affects the feasibility of its large-scale application.

[0066] Test Example

[0067] (1) Sensitivity test of the TTI sensor array

[0068] Drop 1 mL of 100 mM L-ascorbic acid sequentially onto the TTI sensor array made of different concentrations of HAuCl4 solution in Example 1, and conduct tests under storage conditions at 0 °C and 10 °C respectively. Use a camera to record the color changes of the sensor at different HAuCl4 concentrations. The results are shown in Figure 1 and Figure 2 respectively. It can be seen from Figure 1 and Figure 2 that whether stored at 0 °C or 10 °C, with the passage of time, the label color gradually deepens and finally turns purple. For the TTI sensors with the same HAuCl4 concentration, the color change speed is faster at higher temperatures; at the same temperature, the sensors with higher HAuCl4 concentrations also show faster color changes.

[0069] (2) Sensitivity test of the pH response sensor array

[0070] The pH response colorimetric sensor array selects methyl red and bromocresol green as pH response indicators. Among them, the pH color change range of methyl red is from 4.4 to 6.2, and the pH color change range of bromocresol green is from 3.8 to 5.4. To evaluate the sensitivity of the pH response colorimetric sensor array to color changes, in the experiment, the sensor samples were placed in a buffer solution with a pH value range of 3.8 - 6.2, left to stand for 1 min at 25 °C, and then a camera was used to record the color changes of the sensor array. The results are shown in Figure 3 respectively. It can be seen from Figure 3As can be seen from the results, the mixed indicator shows high sensitivity to pH changes, and the indicator label exhibits obvious color changes when the pH changes. Especially when the ratio of methyl red to bromocresol green is 6:4 and 5:5, the color changes are particularly significant.

[0071] (3) Evaluation of fruit freshness

[0072] For the evaluation of the fruit freshness in the fresh-keeping box obtained in Application Example 1 of the present invention, it specifically refers to the weight loss, respiration rate, total soluble solids, titratable acidity, sensory evaluation and the detection results of the colorimetric sensor array. The specific experimental time is 7 days, and the color changes of the sensor array are observed every day to detect the freshness of the fruit.

[0073] Weight loss: During the storage of the fruit, the weight loss was measured by a laboratory-grade weighing balance (Precision Balance XPE303S, METTLER TOLEDO INTERNATIONAL INC., Switzerland) and expressed on a wet weight basis (g / kg). The calculation method is the difference between the initial weight of the sample and the weight measured on the same day.

[0074] Respiration rate: Since the fruit releases CO2 due to respiration, the CO2 concentration in the package was detected by a gas detector (DK-190 Headspace Gas Analyzer, Jinan Saicheng Electronic Technology Co., Ltd.), and then the respiration rate of the fruit was obtained.

[0075] Content of total soluble solids (TSS): The TSS content of the fruit was measured using a hand-held refractometer (ATAGO PAL-1, ATAGO Co., Ltd., Japan). Every day, 6 fresh-keeping box fruits were selected from the fruit samples, peeled and the juice was extracted. Each sample was measured three times, and the values measured every day were recorded and the average value was calculated as the TSS value of the day.

[0076] Titratable acidity: A certain amount of fruit was juiced and filtered. 25 ml of the juice was taken, diluted with 75 ml of distilled water, and 2-3 drops of phenolphthalein indicator were added after mixing evenly. It was titrated with a standard 0.1N NaOH solution, and the solution was added drop by drop to the mixture until the solution changed from colorless to light pink and remained unchanged for 30 seconds. The volume (V) of the consumed NaOH solution was recorded, and the titratable acidity was calculated.

[0077] Sensory evaluation: During the storage of the fruit, 15 volunteers (8 males and 7 females, aged 20-25) were invited to evaluate multiple sensory characteristics of the fruit. All volunteers had received professional sensory evaluation training and signed an informed consent form when participating. The evaluation content mainly included aspects such as the color, smell, pulp fiber and residue of the fruit. Each evaluator scored independently, and the final score would be used as an important basis for evaluating the quality change of the fruit during storage.

[0078] The detection results of respiration rate and titratable acidity are as follows Figure 4 shown. From Figure 4 the results, it can be seen that as the storage time increases, the CO2 concentration of mangoes rises rapidly to about 30% within the first 0 - 3 days, and then the growth rate slows down. Respiration is the main reason for the generation of CO2 during the storage of mangoes, and it gradually increases over time. The titratable acidity drops rapidly within the first 2 days and then the decline rate slows down. The titratable acidity reflects the acidity of the fruit. As the storage time increases, the organic acids in the mangoes are consumed, resulting in a gradual decrease in acidity.

[0079] The results of total soluble solids content and weight loss are as follows Figure 5 shown. From Figure 5 the results, it can be seen that the total soluble solids (TSS) increase rapidly on the 2nd day and the growth is very slow after the 4th day, indicating that the sugars in the mangoes accumulate over time. The weight of the mangoes remains almost unchanged in the first 2 days, and the weight loss increases significantly starting from the 3rd day and the growth rate slows down after the 4th day. The weight loss is mainly due to water evaporation, respiration, and microbial activities.

[0080] The results of sensory evaluation are as follows Figure 6 shown. From Figure 6 the results, it can be seen that the sensory evaluation shows obvious changes. In terms of appearance, texture, sweetness, acidity, and overall acceptance, the scores are the highest on the 0 - 1st days, decrease during the 2 - 3rd days, and drop rapidly after the 4th day.

[0081] Detection results of the colorimetric sensor array: The mango fresh - keeping box with the TTI - pH response dual - colorimetric sensor array attached was stored in an environment of 15°C, and the color changes of the sensor array were recorded daily using a camera. The experimental results show that in the initial stage of storage, the fruit is in the pre - climacteric stage with weak respiration, resulting in small changes in the environmental pH and insignificant color changes in the pH - responsive sensor, while the color of the TTI sensor changes gradually and uniformly, which can be used to assist in judging freshness. As the fruit enters the climacteric stage, respiration intensifies, releasing a large amount of CO2, causing significant changes in the environmental pH and obvious color changes in the pH - responsive sensor, which can effectively reflect the changes in fruit freshness.

[0082] The above - mentioned is only the preferred embodiment of the present invention, and the present invention is not limited to the above examples. It can be understood that other improvements and changes directly derived or associated by those skilled in the art without departing from the spirit and concept of the present invention should be considered to be included within the protection scope of the present invention.

Claims

1. A preparation method of a colorimetric sensor array based on the dual information fusion of time-temperature indication and pH response, characterized in that, The colorimetric sensor array consists of a pH-responsive sensor array and a TTI sensor array; the preparation method includes the following steps: (1) Dissolve methylcellulose in distilled water and perform ultrasonic treatment to obtain a substrate solution; (2) Prepare HAuCl4 solutions with concentrations of 0.005 - 0.13 g / L, methyl red solutions with a concentration of 0.1 ± 0.05 g / mL, and bromocresol green solutions with a concentration of 0.1 ± 0.05 g / mL; (3) Mix the methyl red solution and the bromocresol green solution according to a volume ratio of 1:0.4 - 2.3 to obtain a mixed solution, and then add it to the substrate solution and dry to obtain a pH-responsive sensor array; (4) Add the HAuCl4 solution to the substrate solution and dry to obtain a TTI sensor array.

2. The preparation method according to claim 1, characterized in that, In step (1), the concentration of methylcellulose in the substrate solution is 25 - 30 g / L; the temperature of dissolution is 50 - 60 °C, the rotation speed is 800 - 1000 rpm, and the time is 1 - 1.2 h.

3. The preparation method according to claim 1, wherein In step (1), the frequency of ultrasonic treatment is 40 - 50 kHz, and the time is 50 - 60 min.

4. The preparation method according to claim 1, characterized in that, In step (2), the concentration of the HAuCl4 solution is 0.005 g / L, 0.03 g / L, 0.05 g / L, 0.01 g / L, or 0.013 g / L.

5. The preparation method according to claim 1, characterized in that, In step (3), the volume ratio of the methyl red solution to the bromocresol green solution is 3:7, 4:6, 5:5, 6:4, or 7:3; the volume ratio of the mixed solution to the substrate solution is 1:

10.

6. The preparation method according to claim 1, wherein In step (3), the drying temperature is 40 - 50 °C, and the time is 24 - 24.5 h.

7. The preparation method according to claim 1, characterized in that, In step (4), the volume ratio of the HAuCl4 solution to the substrate solution is 1:

50.

8. The preparation method according to claim 1, characterized in that, In step (4), the drying temperature is 40 - 50 °C, and the time is 24 - 24.5 h.

9. Use of the colorimetric sensor array prepared by the preparation method according to any one of claims 1-8, characterized in that, The colorimetric sensor array is applied to evaluate the freshness of fruits.

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