Humidity-resistant environment freshness colorimetric sensor as well as preparation method and application thereof

Abstract

The invention is applicable to the technical field of food freshness monitoring, and provides a moisture-resistant environment freshness colorimetric sensor which comprises a transparent layer, a filter paper array layer and a breathable layer, the invention also provides a preparation method of the humidity-resistant environment freshness colorimetric sensor, which comprises the following steps: manufacturing the filter paper array, and sequentially assembling the transparent layer, the filter paper array and the breathable layer from top to bottom to form the colorimetric sensor. Wherein the step of manufacturing the filter paper array comprises the following steps: screening the concentration of an indicator; preparing an ammonia water solution; dissolving the indicator; determining a printing volume; and spraying an indicator. The invention further provides application of the humidity-resistant environment freshness colorimetric sensor in the field of food freshness monitoring. According to the food freshness colorimetric sensor, the situation of color diffusion of a colorimetric card caused by moisture volatilization is effectively avoided, and the food freshness colorimetric sensor has a good development prospect.

Description

Technical Field

[0001] The present invention belongs to the technical field of food freshness monitoring, and particularly relates to a humidity-resistant freshness colorimetric sensor for a humid environment, a preparation method thereof, and an application thereof. Background Art

[0002] With the improvement of living standards and the enhancement of health awareness, consumers have put forward higher requirements for the quality of food, especially for perishable foods such as meat and vegetables. The freshness of meat and vegetables has become one of the important indicators of the quality of meat and vegetables.

[0003] Meat and vegetables are rich in protein and are extremely vulnerable to the influence of endogenous enzymes and external microorganisms during storage, transportation, sales and other links, resulting in spoilage. Therefore, real-time monitoring of the freshness of meat and vegetables is of great significance for improving the food safety of food and reducing food waste.

[0004] Meat and vegetables are one of the main sources of human nutrition and are essential foods in people's daily lives. However, during storage, transportation and sales, meat and vegetables are prone to spoilage due to enzymatic reactions and microbial contamination. A large number of harmful metabolites are produced during the spoilage of meat and vegetables, seriously damaging the nutritional value and commercial value of meat and vegetables. At the same time, spoiled food is likely to cause foodborne diseases and pose a hazard to human health. There are no related products on the market that can monitor the freshness of meat and vegetables and effectively monitor the freshness of meat and vegetable products in real time. Therefore, developing a freshness-indicating technology for meat and vegetable foods to determine the food safety of meat and vegetables is of great significance for reducing food safety risks and reducing food waste. Summary of the Invention

[0005] An object of an embodiment of the present invention is to provide a humidity-resistant freshness colorimetric sensor for a humid environment, a preparation method thereof, and an application thereof. The present invention can effectively reduce the interference of humidity on the filter paper colorimetric sensing array to monitor the freshness of meat and vegetables, and can effectively monitor the freshness of meat and vegetable products in real time, greatly improving the color development degree of the indicator card.

[0006] To achieve the above object, the present invention provides the following technical solutions.

[0007] In an embodiment of the present invention, a humidity-resistant freshness colorimetric sensor for a humid environment is provided. The sensor includes a transparent layer, a filter paper array layer and a breathable layer. The filter paper array layer is located between the transparent layer and the breathable layer, and the breathable layer is used to contact the sample to be measured; wherein:

[0008] The filter paper array layer is a colorimetric card structure sprayed with an indicator. The colorimetric card uses filter paper as a printing substrate, and a plurality of indicators are printed on the printing substrate according to corresponding printing volumes. The concentrations of different indicators are different, and the concentrations are distributed in a gradient manner.

[0009] As a further limitation of the preferred embodiment of the present invention, the breathable layer includes a waterproof breathable membrane and a water-permeable breathable membrane. The water-permeable breathable membrane is used to contact the sample to be measured, and the waterproof breathable membrane is located between the water-permeable breathable membrane and the filter paper array layer.

[0010] As a further limitation of the preferred embodiment of the present invention, the transparent layer is a transparent plastic, which is used to observe the color change of the filter paper array layer.

[0011] In another embodiment of the present invention, a preparation method of a freshness colorimetric sensor for a humid environment is provided. The preparation method includes the following steps: making a filter paper array, assembling the transparent layer, the filter paper array and the breathable layer from top to bottom in sequence to form a colorimetric sensor; wherein, the step of making the filter paper array includes:

[0012] Indicator concentration screening: respectively screen out indicator solutions with various concentrations, use a UV-visible spectrophotometer to respectively measure the UV-visible spectra of various indicator solutions under various pH concentration conditions, draw a UV spectrum diagram, and simultaneously record the color change with a camera, and screen out the required indicator concentration based on the color change;

[0013] Ammonia water solution preparation: Dilute 1mg / ml ammonia water to prepare 0.1mg / ml ammonia water solution.

[0014] Dissolution of the indicator: Dissolve the indicator at the concentration screened out in the indicator concentration screening step with absolute ethanol.

[0015] Determine the printing volume: Use filter paper as a printing substrate, print gradient concentrations respectively, and screen out the optimal printing volume of each indicator through the color clarity presented by dropping pH buffer solution.

[0016] Spray the indicator: Use filter paper as a substrate, print the indicator onto the substrate to obtain an indicator colorimetric card for food freshness detection, and this indicator colorimetric card is used as the filter paper array.

[0017] As a further limitation of the preferred embodiment of the present invention, in the step of using a UV-visible spectrophotometer to respectively measure the UV-visible spectra of various indicator solutions under various pH concentration conditions, the scanning wavelength of the UV-visible spectrum is 300nm to 800nm; the pH concentration is 5 to 12.

[0018] In yet another embodiment of the present invention, an application of the freshness colorimetric sensor for a humid environment in the field of food freshness monitoring is provided.

[0019] Compared with the prior art, the technical advantages of the present invention are as follows:

[0020] The present invention combines a transparent plastic, a filter paper array, a waterproof and breathable membrane, and a water-permeable and breathable membrane in a "sandwich" manner to reduce the interference of humidity on the colorimetric sensing array; the prepared indicator card is applied to the freshness monitoring of foods such as pork and beans, and stored under different humidities, and whether the color of the colorimetric card diffuses is observed to test the waterproof performance of the freshness colorimetric sensor resistant to a humid environment. It is concluded that the application of the freshness colorimetric sensor resistant to a humid environment of the present invention is indeed feasible, the color is uniform and there is no obvious diffusion phenomenon, and it can still maintain a good colorimetric sensing effect after being stored at room temperature for 14 days;

[0021] In summary, the present invention can prepare a freshness colorimetric sensor for foods with waterproof, breathable, and transparent properties by adopting a combination method including a transparent layer, a filter paper array layer, and a breathable layer, effectively avoiding the occurrence of color diffusion of the colorimetric card caused by water evaporation, having good development prospects and good commercialization prospects. Brief Description of the Drawings

[0022] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following will briefly introduce the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings in the following description are only some embodiments of the present invention.

[0023] Figure 1 It is a schematic diagram of a freshness colorimetric sensor resistant to a humid environment of the present invention;

[0024] Figure 2 It is the colorimetric situation of different groups of freshness colorimetric sensors for the environment (28±3°C, 55±5%RH) stored in 1 mg / ml ammonia water for different days;

[0025] Figure 3 It is the change in the Euclidean distance of different groups of freshness colorimetric sensors in response to 1 mg / ml ammonia water in the environment (28±3°C, 55±5%RH). Detailed Description of the Embodiments

[0026] In order to make the objectives, technical solutions, and advantages of the present invention clearer, the following further details the present invention with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0027] At present, during the spoilage process of meat and vegetable foods, the protein in the meat will decompose and produce volatile amines such as trimethylamine, dimethylamine, and ammonia. The total amount of these volatile amines is directly correlated with the freshness of the meat. Among vegetables, vegetables with high protein content produce alkaline volatile organic compounds (VOCs), and vegetables with high sugar content, such as string beans, can produce acidic volatile organic compounds. The total amount of these volatile organic compounds is directly correlated with the freshness of the vegetables. The accumulation of volatile amines and organic substances will affect the acidity and alkalinity of the environment, prompting the indicator of the pH-responsive intelligent indicator card to undergo a structural change, which macroscopically shows a change in the color of the indicator card, thus realizing the visual conversion of the freshness of meat and vegetables.

[0028] Considering the safety of food, more and more researchers have begun to use natural pigments extracted from plants as indicators. In recent years, natural food dyes, as natural additives or indicators in food packaging, have attracted great interest to meet the growing demand of consumers for healthier and safer foods. Natural dyes are not only safe but also have certain functions, such as antioxidant and antibacterial capabilities. However, since water will be released from meat and vegetables during storage, as the water volatilizes, it may lead to more gas analytes dissolving, water vapor permeating into the hydrophobic plastic film causing plasticization, water vapor participating in chemical reactions, etc., thus affecting the sensitivity of the colorimetric sensor.

[0029] Therefore, the present invention mainly studies a freshness colorimetric sensor for a humid environment. A transparent plastic, a filter paper array, a waterproof and breathable membrane, and a water-permeable and breathable membrane are combined in a "sandwich" manner to reduce the interference of humidity on the colorimetric sensing array. The prepared indicator card is applied to the freshness detection of pork and string beans and stored under different humidities to observe whether the color of the colorimetric card diffuses to test the waterproof performance of the freshness colorimetric sensor for a humid environment. Therefore, it is concluded that the application of the freshness colorimetric sensor for a humid environment is indeed feasible, with uniform color and no obvious diffusion phenomenon. It can be stored at room temperature for 14 days and still maintain good colorimetric sensing effects, having good development prospects and can be commercialized.

[0030] The following describes the specific implementation of the present invention in detail in combination with specific embodiments.

[0031] Example 1

[0032] Please refer to Figure 1 , in the embodiment of the present invention, a freshness colorimetric sensor for a humid environment is provided. The sensor includes a transparent layer, a filter paper array layer, and a breathable layer. The filter paper array layer is located between the transparent layer and the breathable layer, and the breathable layer is used to contact the sample to be measured; wherein:

[0033] In an embodiment of the present invention, the filter paper array layer is a colorimetric card structure sprayed with an indicator. The colorimetric card uses filter paper as a printing substrate, and a plurality of indicators are printed on the printing substrate according to corresponding printing volumes. The concentrations of different indicators are different, and the concentrations are distributed in a gradient manner.

[0034] Further, in an embodiment of the present invention, the breathable layer includes a waterproof breathable membrane and a water-permeable breathable membrane. The water-permeable breathable membrane is used to contact the sample to be measured, and the waterproof breathable membrane is located between the water-permeable breathable membrane and the filter paper array layer.

[0035] Further, in an embodiment of the present invention, the transparent layer is a transparent plastic, which is used to observe the color change of the filter paper array layer.

[0036] Embodiment 2

[0037] In an embodiment of the present invention, a preparation method of a freshness colorimetric sensor resistant to a humid environment is provided;

[0038] The preparation method includes the following steps: fabricating a filter paper array, and assembling a transparent layer, the filter paper array, and the breathable layer in sequence from top to bottom to form a colorimetric sensor;

[0039] Among them, the step of fabricating the filter paper array includes: indicator concentration screening, ammonia water solution preparation, indicator dissolution, determination of printing volume, and spraying of the indicator.

[0040] Among them, in the step of indicator concentration screening of the present invention, indicator solutions with various concentrations are respectively screened out. The ultraviolet-visible spectra of various indicator solutions under various pH concentration conditions are respectively measured by using an ultraviolet spectrophotometer, an ultraviolet spectrum diagram is drawn, and the color change is recorded by using a camera. The required indicator concentration is screened out based on the color change;

[0041] Further, in the step of ammonia water solution preparation of the present invention, a 0.1 mg / ml ammonia water solution is prepared by diluting 1 mg / ml ammonia water;

[0042] Further, in the step of indicator dissolution of the present invention, the indicator at the concentration screened out in the indicator concentration screening step is dissolved with absolute ethanol;

[0043] Further, in the step of determining the printing volume of the present invention, with filter paper as the printing substrate, gradient concentrations are respectively printed, and the optimal printing volume of each indicator is screened out through the color clarity presented by dropping a pH buffer solution;

[0044] Further, in the step of spraying the indicator of the present invention, with filter paper as the substrate, and then the indicator is printed onto the substrate, thereby obtaining an indicator colorimetric card for food freshness detection. The indicator colorimetric card obtained in this step is used as the filter paper array.

[0045] In the embodiments of the present invention, in the step of respectively measuring the ultraviolet-visible spectra of various indicator solutions under various pH concentration conditions by using an ultraviolet spectrophotometer, the scanning wavelength of the ultraviolet-visible spectrum is from 300 nm to 800 nm; the pH concentration is from 5 to 12.

[0046] The freshness colorimetric sensors resistant to humid environment in Examples 1 to 2 were tested, and the test process is as follows:

[0047] Two prepared freshness colorimetric sensors resistant to humid environment (experimental group) and a freshness colorimetric sensor of the environment without humidity resistance treatment (blank group) were placed in an ammonia water solution of 1 mg / ml and stored in an environment (28 ± 3 °C, 55 ± 5% RH) for 28 days. Observe whether the color of the colorimetric card diffuses to test the waterproof performance of the freshness colorimetric sensor resistant to humid environment. During this period, record the color diffusion of the colorimetric sensing array at different days respectively.

[0048] Test results: Compared with the blank group, no obvious color diffusion phenomenon occurred in the experimental group placed in an ammonia water solution of 1 mg / ml under different humidity environments ( Figure 2 ). The fluctuation range of the ED value of the experimental group is smaller than that of the blank group ( Figure 3 ). Among them, the RSD of the ED value of the experimental group is 3.44%, and the RSD of the ED value of the blank group is 12.40% (Table 1). The above results show that the freshness colorimetric sensor resistant to humid environment in the experimental group still maintains good colorimetric sensing effect after long-term storage, effectively reducing the influence of moisture in the humid environment on the response of the freshness colorimetric sensor of the environment (compared with the freshness colorimetric sensor of the environment without humidity resistance treatment in the blank group);

[0049] Table 1 shows the reproducibility of the response of the freshness colorimetric sensors of different groups in an ammonia water solution of 1 mg / ml in an environment (28 ± 3 °C, 55 ± 5% RH)

[0050]

[0051] Taking pork as an example, the freshness colorimetric sensors resistant to humid environment in Examples 1 to 2 were tested:

[0052] The present invention applies the prepared freshness colorimetric sensor resistant to humid environment to the freshness monitoring of pork. Fresh pork was stored in an environment (28 ± 3 °C, 55 ± 5% RH) and a refrigerator (4 °C) for 9 days respectively. Observe whether the color of the colorimetric card diffuses to test the waterproof performance of the freshness colorimetric sensor resistant to humid environment applied in pork. During this period, record the color diffusion of the colorimetric sensing array at different days respectively.

[0053] Test results: When the filter paper colorimetric sensing array was placed in different humidity environments of pork, there was no obvious color diffusion phenomenon in the filter paper colorimetric sensing array, and it still maintained good colorimetric sensing effect, indicating that the freshness colorimetric sensor resistant to humid environment could maintain good and accurate effect in the freshness detection of pork under different humidity environments.

[0054] Taking green beans as an example, the freshness colorimetric sensor resistant to humid environment in Examples 1 to 2 was tested:

[0055] The prepared freshness colorimetric sensor resistant to humid environment of the present invention was applied to the freshness monitoring of green beans. Fresh green beans were stored in an environment (28±3°C, 55±5%RH) and a refrigerator (4°C) for 9 days respectively, and whether the color of the colorimetric card diffused was observed to test the waterproof performance of the freshness colorimetric sensor resistant to humid environment when applied to green beans. During this period, the color diffusion situation of the colorimetric sensing array was recorded respectively at different days.

[0056] Test results: When the filter paper colorimetric sensing array was placed in different humidity environments of green beans, there was no obvious color diffusion phenomenon in the filter paper colorimetric sensing array, and it still maintained good colorimetric sensing effect, indicating that the freshness colorimetric sensor resistant to humid environment could maintain good and accurate effect in the freshness detection of green beans under different humidity environments.

[0057] In summary, the freshness colorimetric sensor resistant to humid environment provided by the present invention is specifically a "sandwich"-type waterproof design, which can effectively reduce the interference of humidity on the filter paper colorimetric sensing array to monitor the freshness of meat and vegetables, and can effectively monitor the freshness of meat and vegetable products in real time, greatly improving the color development degree of the indicator card;

[0058] The present invention can prepare a food freshness colorimetric sensor with waterproof, breathable and transparent properties by adopting a combination method including a transparent layer, a filter paper array layer and a breathable layer, effectively avoiding the occurrence of color diffusion of the colorimetric card caused by water evaporation, having good development prospects and good commercialization prospects.

[0059] The above solutions are only illustrations of a preferred example, but not limited thereto. When implementing the present invention, appropriate substitution and / or modification can be made according to the needs of users.

[0060] Although the embodiments of the present invention have been disclosed as above, it is not limited to the applications listed in the specification and embodiments. It can be fully applied to various fields suitable for the present invention. For those familiar with the field, additional modifications can be easily achieved. Therefore, without departing from the general concept defined by the claims and the equivalent scope, the present invention is not limited to the specific details and the illustrated examples here.

Claims

1. A freshness colorimetric sensor resistant to humid environments, characterized in that: The sensor comprises a transparent layer, a filter paper array layer and a breathable layer, wherein the filter paper array layer is located between the transparent layer and the breathable layer, and the breathable layer is used to contact with the sample to be tested; wherein: The filter paper array layer is a colorimetric card structure sprayed with an indicator. The colorimetric card uses filter paper as a printing substrate, and multiple indicators are printed on the printing substrate according to corresponding printing volumes. Different indicators have different concentrations, and the concentrations are distributed in a gradient.

2. The humid environment resistant freshness colorimetric sensor according to claim 1, characterized in that: The air-permeable layer comprises a waterproof air-permeable membrane and a water-permeable air-permeable membrane. The water-permeable air-permeable membrane is used to contact with the sample to be tested, and the waterproof air-permeable membrane is located between the water-permeable air-permeable membrane and the filter paper array layer.

3. The humid environment resistant freshness colorimetric sensor according to claim 2, characterized in that: The transparent layer is transparent plastic and is used to observe the color change of the filter paper array layer.

4. A method for preparing a freshness colorimetric sensor resistant to humid environments, characterized in that: The preparation method comprises the following steps: making a filter paper array, assembling a transparent layer, a filter paper array and a breathable layer in sequence from top to bottom to form a colorimetric sensor; wherein the step of making the filter paper array comprises: Indicator concentration screening: screen out indicator solutions of various concentrations, use a UV spectrophotometer to measure the UV-visible spectra of various indicator solutions under various pH concentration conditions, draw UV spectra, and use a camera to record color changes, and screen out the required indicator concentration based on the color changes; Preparation of ammonia solution: dilute 1mg / ml ammonia solution to prepare 0.1mg / ml ammonia solution; Dissolving the indicator: using anhydrous ethanol to dissolve the indicator of the concentration selected in the indicator concentration screening step; Determine the printing volume: Use filter paper as the printing substrate, print gradient concentrations respectively, and select the optimal printing volume of various indicators by the color clarity presented by adding pH buffer solution; Spraying indicator: Using filter paper as substrate, the indicator is printed onto the substrate to obtain an indicator colorimetric card for food freshness detection, which is used as a filter paper array.

5. The method for preparing the humid environment resistant freshness colorimetric sensor according to claim 2, characterized in that: In the step of using an ultraviolet spectrophotometer to measure the ultraviolet-visible spectra of various indicator solutions under various pH concentration conditions, the scanning wavelength of the ultraviolet-visible spectrum is 300nm to 800nm; and the pH concentration is 5 to 12.

6. Application of the humid environment resistant freshness colorimetric sensor as claimed in any one of claims 1 to 3, or the humid environment resistant freshness colorimetric sensor prepared by the preparation method of the humid environment resistant freshness colorimetric sensor as claimed in claim 4 or 5 in the field of food freshness monitoring.

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