Biochemical temperature display sticker for low-temperature food and processing method

Abstract

The invention relates to the technical field of low-temperature food quality monitoring, in particular to a biochemical temperature display sticker for low-temperature food and a processing method. The temperature display sticker comprises a base material, a temperature display layer and a protective layer, wherein the temperature display layer comprises a biochemical reaction system consisting of enzyme and a substrate. When the environment temperature reaches a preset threshold value, the enzymatic reaction causes color change, and visual indication of the temperature state is achieved. The processing method comprises the steps of preparing a biochemical reaction system, preparing printable slurry, printing to form the temperature display layer, covering the protective layer and the like. According to the invention, the problems of insufficient precision and poor stability of the existing temperature monitoring technology are solved, and a temperature monitoring solution with low cost and high reliability is provided.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of low-temperature food quality monitoring, and more particularly, to a biochemical temperature display sticker for low-temperature food and a processing method. BACKGROUND

[0002] Temperature monitoring in the storage and transportation process of low-temperature food is an important technical link in the field of food quality and safety control. At present, electronic temperature recorders, physical time-temperature indicators and chemical color-changing materials are mainly used as monitoring means in this field. In recent years, with the development of biosensing technology, temperature indicating devices based on biomolecular recognition principles have gradually become a research hotspot, and the technology development shows a trend from electronic to biochemical and from complex structure to simple label. In the process of technological evolution, heat-sensitive color-changing paint, liquid crystal temperature indicating sheet and intelligent packaging based on enzyme reaction have appeared successively, and the industry technology development gradually advances towards low cost, high sensitivity and visual detection.

[0003] The existing temperature monitoring technology mainly has the following deficiencies: the physical time-temperature indicator can only accumulate and calculate the temperature exposure time, and cannot accurately reflect the influence of instantaneous temperature fluctuation on food quality; the chemical temperature indicator mostly uses pH-sensitive dyes or metal salts, and its color-changing reaction is irreversible and easily disturbed by environmental humidity, resulting in a high false alarm rate; although some biological indicators have good temperature specificity, the active ingredients are easily inactivated during processing and storage, and the stability is difficult to guarantee; the electronic temperature recording device has high precision, but is expensive and needs special equipment to read data, and is not suitable for whole-process monitoring of single goods; in addition, most of the existing temperature indicating stickers need complex multi-layer isolation structure, which increases the production process difficulty and cost, and affects the flexibility and adhesion of the sticker.

[0004] Therefore, in view of the above problems, a biochemical temperature display sticker for low-temperature food and a processing method are proposed, and the technical problems to be solved include: providing a temperature monitoring scheme that can accurately reflect a specific temperature threshold, has good stability, is cost-effective and easy to use, and overcomes the deficiencies of insufficient temperature indication precision, poor stability, high cost and inconvenient use in the prior art. SUMMARY

[0005] In order to overcome the above-mentioned defects of the prior art, the embodiments of the present application provide a biochemical temperature display sticker for low-temperature food and a processing method to solve the problems proposed in the background art.

[0006] To achieve the above-mentioned purpose, the present application provides the following technical scheme: a processing method of a biochemical temperature display sticker for low-temperature food, comprising the following steps:

[0007] S1: preparing a biochemical reaction system, the biochemical reaction system comprising at least one enzyme and at least one substrate, the enzyme and substrate undergoing an enzymatic reaction resulting in a visible color change when reaching a predetermined low temperature threshold;

[0008] S2: mixing the biochemical reaction system with a carrier material to form a uniform printable paste, the carrier material serving to disperse and stabilize the biochemical reaction system;

[0009] S3: applying the printable paste onto a substrate surface through a printing process to form a temperature display layer, the substrate being a flexible material to allow attachment to food packaging;

[0010] S4: covering the temperature display layer with a protective layer, the protective layer serving to protect the temperature display layer from mechanical damage and environmental contamination while allowing gas permeation to trigger the enzymatic reaction;

[0011] S5: subjecting the temperature display layer to a drying process to solidify and maintain the biochemical activity of the temperature display layer;

[0012] wherein the processing method ensures that the temperature display sticker remains stable in a low temperature environment until the temperature reaches the predetermined low temperature threshold.

[0013] Preferably, in step S1, the enzyme in the biochemical reaction system is selected from the group consisting of oxidoreductases, including at least one of glucose oxidase, peroxidase, the substrate is selected from the group consisting of chromogenic compounds, including at least one of o-dianisidine, tetramethylbenzidine, and the biochemical reaction system further comprises a buffer to maintain the pH stability of the reaction system.

[0014] Preferably, in step S1, the predetermined low temperature threshold is in the range of -20°C to 10°C, the predetermined low temperature threshold is achieved by adjusting the concentration ratio of enzyme and substrate in the biochemical reaction system and the composition of the carrier material.

[0015] Preferably, in step S2, the carrier material comprises a water-soluble polymer selected from at least one of polyvinyl alcohol, hydroxypropyl methyl cellulose, the carrier material forms a homogeneous slurry with the biochemical reaction system during mixing, and the viscosity of the slurry is adjusted to be in the range of 100-5000 mPa·s by controlling the water content.

[0016] Preferably, in step S3, the printing process uses screen printing or inkjet printing, the screen printing uses a screen pattern to control the shape and thickness of the temperature display layer, the inkjet printing precisely deposits the slurry through digital control, and the formed temperature display layer has a thickness of 5-50 μm.

[0017] Preferably, in step S4, the protective layer is a gas-permeable film selected from at least one of porous polyethylene, polyurethane film, which is laminated or coated on the temperature display layer and has a microporous structure to allow oxygen and water vapor to pass through while blocking liquid and solid contaminants, and has a thickness of 10-100 μm.

[0018] Preferably, before step S3, there is also step S2a: applying an adhesive layer on the substrate, which is composed of pressure-sensitive glue or hot-melt glue, for firmly attaching the temperature display sticker to the surface of the food packaging, and the adhesive layer remains adhesive in a low-temperature environment without affecting biochemical reactions.

[0019] A biochemical temperature display sticker for low-temperature food, prepared by the above-mentioned processing method, comprising:

[0020] a substrate made of flexible material;

[0021] a temperature display layer disposed on the substrate, containing a biochemical reaction system, which contains at least one enzyme and at least one substrate;

[0022] a protective layer covering the temperature display layer, allowing gas to pass through;

[0023] wherein the temperature display sticker produces visible color changes through enzymatic reactions when reaching a predetermined low-temperature threshold.

[0024] Preferably, the temperature display layer also contains a carrier material, which includes a water-soluble polymer selected from at least one of polyvinyl alcohol, hydroxypropyl methyl cellulose.

[0025] Preferably, the protective layer is a gas-permeable film selected from at least one of porous polyethylene, polyurethane film, with a thickness of 10-100 μm.

[0026] Technical effects and advantages of the present application:

[0027] Compared with the prior art, the present application realizes accurate response to a specific temperature point by constructing a biochemical reaction system containing specific enzymes and substrates, wherein the enzymes are selected from the oxidoreductase class including glucose oxidase and peroxidase, and the substrates are selected from chromogenic compounds including o-dianisidine and tetramethylbenzidine, the system triggers an enzymatic reaction to produce a color change when a predetermined low temperature threshold is reached, the trigger temperature can be accurately set between-20℃ and 10℃ by adjusting the concentration ratio of the enzyme and the substrate, effectively avoiding the problem that traditional physical indicators can only calculate cumulative time and cannot accurately capture critical temperature, and compared with chemical indicators, the present application has better reversibility and environmental adaptability, significantly improving the accuracy and reliability of temperature monitoring.

[0028] Compared with the prior art, the present application encapsulates the biochemical reaction system in a high molecular capsule by microencapsulation technology, the capsule material is composed of gelatin, gum arabic or polylactic acid, and the microcapsule structure with controllable release characteristics is formed by complex coagulation or interfacial polymerization process. This packaging method effectively isolates the direct contact between the enzyme and the substrate, prevents pre-reaction during storage, and controls the release rate of the reaction material by adjusting the thickness and porosity of the capsule wall material, which not only ensures the timeliness of the reaction when triggered by temperature, but also significantly prolongs the effective shelf life of the product, solving the technical problems of easy inactivation and poor stability of active ingredients of traditional biological indicators.

[0029] Compared with the prior art, the present application forms a printable slurry by mixing the biochemical reaction system with a water-soluble polymer carrier material, the carrier material is selected from polyvinyl alcohol or hydroxypropyl methyl cellulose, the slurry viscosity is adjusted to be in the range of 100-5000 mPa·s by controlling the water content, so that it is suitable for screen printing or inkjet printing process, the slurry formula and processing method enable the temperature display layer to be formed on the surface of the substrate with accurate pattern and thickness, the display layer thickness is controlled between 5-50 μm, which not only ensures the uniformity of the reaction system distribution, but also realizes the feasibility and economy of industrial large-scale production, and at the same time, the design of the air permeable protective layer effectively prevents mechanical damage and pollution while ensuring gas permeability, significantly improving the practicality and durability of the product. BRIEF DESCRIPTION OF DRAWINGS

[0030] Fig. 1 The temperature display sticker structure of the present application is shown in the figure.

[0031] Fig. 2 The temperature display sticker processing method flowchart of the present application is shown in the figure.

[0032] Fig. 3 The temperature trigger and indication working principle diagram of the present application is shown in the figure. DETAILED DESCRIPTION

[0033] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0034] Example 1

[0035] As attached Figs. 1 to 3 The following is a description of a biochemical temperature display sticker for low-temperature foods and its processing method:

[0036] 1. Implementation Step 1

[0037] This step involves the design and preparation of the biochemical reaction system, which determines the functionality of the temperature display sticker. The enzyme-substrate combination is selected based on the principle of redox reaction, employing a dual-enzyme system of glucose oxidase and peroxidase, combined with the chromogen substrate tetramethylbenzidine. The activity temperature range of glucose oxidase is set between -15℃ and 5℃, while peroxidase ensures that catalytic efficiency is maintained at low temperatures.

[0038] The proportions of each component must be precisely controlled: glucose oxidase concentration ranges from 0.5 to 2.0 U / mg, peroxidase concentration ranges from 0.3 to 1.5 U / mg, and substrate tetramethylbenzidine concentration ranges from 1 to 5 mmol / L. All components are dissolved in phosphate buffer at pH 6.0-7.5, with the buffer ionic strength controlled at 0.01-0.1 mol / L. To maintain system stability, protective agents including 5%-15% trehalose and 1%-5% glycerol are added; these components maintain the tertiary structure of the enzyme protein through hydrogen bonding.

[0039] The preparation process is carried out at 4°C using pre-cooled reagents and containers. A stepwise addition method is employed: first, the buffer solution and the protective agent are mixed, then the enzyme preparation is added, and finally the substrate solution is added. After each addition, the mixture is gently stirred for 5-10 minutes to ensure thorough mixing and avoid enzyme molecule shearing. The prepared reaction system is a homogeneous, transparent liquid and can be immediately proceeded to the next step or stored at -20°C.

[0040] 2. Implementation Step 2

[0041] This step transforms the biochemical reaction system into a printable slurry, requiring precise control of the slurry's rheological properties. The carrier material is selected based on the film-forming properties and biocompatibility of water-soluble polymers, using polyvinyl alcohol or hydroxypropyl methylcellulose with a molecular weight of 30,000-100,000. The carrier material concentration is controlled between 5% and 15% (w / v).

[0042] The preparation process first adds the carrier material into deionized water slowly, and stirs for 2-4 hours at 40-60°C water bath until completely dissolved. After the solution is cooled to room temperature, add the biochemical reaction system with a volume ratio of 1:1 to 3:1. To improve the printing adaptability, add 0.1%-1% surfactant Tween-80 to reduce the surface tension, and add 0.5%-2% rheological modifier sodium carboxymethyl cellulose to adjust the thixotropy.

[0043] The final viscosity of the slurry is controlled in the range of 100-5000 mPa·s, which is detected by a rotary viscometer. The mixing process uses a planetary mixer to stir at a speed of 100-500 rpm for 30-60 minutes to ensure uniform dispersion of the bioactive components. The prepared slurry needs to be defoamed, and static or centrifugal defoaming methods are used to remove air bubbles. After treatment, the slurry is in a uniform and delicate state without visible air bubbles or particulate matter, and can be transferred to the printing process or stored in a 4°C environment for no more than 24 hours.

[0044] 3. Implement step 3

[0045] This step realizes the printing and forming of the temperature display layer, and the printing process needs to be selected according to the application requirements. Screen printing is suitable for large-area simple patterns, and a 300-500 mesh polyester screen is used with a screen tension of 20-25 N / cm and a screen distance of 2-5 mm. A polyurethane squeegee is used for printing, the squeegee angle is 60-75°, the printing speed is 10-20 cm / s, and the pressure needs to be uniform and moderate.

[0046] For complex patterns or high-resolution requirements, piezoelectric inkjet printing is used. The nozzle temperature is maintained at 25±2°C, the voltage pulse width is 20-50μs, and the ink droplet size is 10-30pL. The printing environment temperature is controlled at 20-25°C, and the relative humidity is 40%-60%.

[0047] The substrate is selected as a polyester film or coated paper with a thickness of 50-200μm, and the surface is treated by corona to achieve a surface tension of 38-42 dyn / cm. After printing, immediate stepwise temperature curing is performed: first pre-drying at 25-30°C for 5-10 minutes, and then drying at 35-45°C for 10-20 minutes. The pattern integrity, edge definition and thickness uniformity need to be monitored in real time during printing, the dry film thickness is controlled in the range of 5-50μm, and the thickness variation coefficient is not more than 5%. The completed printed substrate is placed in a dust-free environment for cooling, and then the protective layer covering process is performed.

[0048] 4. Implement step 4

[0049] This step ensures the long-term stability of the product through protective layer compounding, and needs to balance the protective performance and gas permeability. The protective layer material is selected as a porous polyethylene or polyurethane film with a pore size of 0.1-1.0 μm and a thickness of 10-100 μm. The protective layer material is pretreated before compounding, and the surface energy is increased to 45-55 mN / m by plasma treatment or ultraviolet irradiation.

[0050] The compounding process is selected according to the production demand: for small batch production, a double roller laminating machine is used, the roller temperature is 60-80℃, the pressure is 0.2-0.5 MPa, and the line speed is 2-5 m / min; for large-scale production, a coating method is used, the protective layer precursor solution is directly coated on the temperature display layer, and a microporous structure is formed by phase separation method.

[0051] To control the gas permeability, the pore forming process parameters need to be optimized: in the thermal induced phase separation method, the polymer concentration is 10%-20%, and the quenching temperature is 10-30℃; in the solvent induced phase separation method, the ratio of non-solvent to solvent is 1:1 to 3:1. The finished protective layer should have a uniform microporous structure, the porosity is 40%-70%, the oxygen permeability is 1000-5000 cm 3 / m 2 ·24h·atm, the water vapor permeability is 500-2000 g / m 2 ·24h. The peeling strength of the protective layer and the temperature display layer needs to be greater than 1.0 N / cm. After compounding, integrity detection is needed, including microscope observation, gas permeability test and sealing test.

[0052] 5. Implement step 5

[0053] This step includes drying and curing, slitting and finishing, and quality detection processes. The drying process uses a stepwise temperature rising process: the first stage is 25-30℃ drying for 30-60 minutes, the second stage is 35-45℃ drying for 20-40 minutes, and finally 50-60℃ drying for 10-20 minutes to make the product moisture content less than 3%. The drying equipment needs to have a program-controlled temperature function and a forced ventilation system, and the wind speed is controlled at 0.5-2.0 m / s.

[0054] The slitting process selects a circular knife slitting machine or a laser slitting device according to the application demand, the slitting accuracy is within ±0.2 mm, and the environmental cleanliness reaches 100,000 level standard. The product is immediately vacuum packaged after slitting, using aluminum foil composite film packaging material, vacuum degree-0.08 to-0.10 MPa, and filled with nitrogen protection.

[0055] Quality verification needs to perform comprehensive testing projects: appearance inspection includes color uniformity, bubble and impurity detection; size measurement includes length, width and thickness specifications; biological activity detection requires enzyme activity retention rate greater than 90%; temperature response test needs to verify the color change time and degree at the set threshold temperature; accelerated aging test is performed at 40 DEG C, 75% RH for 30 days performance evaluation; adhesive strength test checks the peel strength of the protective layer and the substrate. All qualified products are stored in the warehouse, the storage temperature is lower than 25 DEG C, the relative humidity is lower than 60%, direct sunlight and chemical pollution are avoided. The whole process needs to establish a quality traceability system, record the process parameters and detection data of each batch.

[0056] Through the system development of the above five implementation steps, the manufacturing process of the biochemical temperature display sticker from raw material preparation to finished product output is fully described. Each step contains specific technical parameters and process requirements to ensure that the final product can reliably indicate temperature changes during low-temperature food storage and transportation. The process design takes into account the feasibility of industrial production and quality control requirements, and has practicality and application value.

[0057] Finally, it should be noted that in the description of the present application, unless otherwise specified and limited, the terms "installation", "connection", "connection" should be broadly understood, which can be mechanical connection or electrical connection, or the internal communication of two elements, or direct connection, "up", "down", "left", "right" and the like are only used to indicate relative positional relationship, when the absolute position of the described object changes, the relative positional relationship may change;

[0058] Secondly: the disclosure of the present application only involves the structure involved in the disclosure of the present application, other structures can refer to the usual design, in the case of no conflict, the same embodiment and different embodiments of the present application can be combined with each other;

[0059] Finally: the above only describes the preferred embodiments of the present application, and is not used to limit the present application, any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present application should be included in the protection scope of the present application.

Claims

1. A process for the production of a biochemical temperature indicating sticker for low temperature food products, characterized in that, The method comprises the following steps: S1: preparing a biochemical reaction system, which comprises at least one enzyme and at least one substrate, the enzyme and substrate undergo an enzymatic reaction to cause a visible color change when reaching a predetermined low-temperature threshold; S2: mixing the biochemical reaction system with a carrier material to form a uniform printable slurry, the carrier material plays a role in dispersing and stabilizing the biochemical reaction system; S3: applying the printable slurry to the surface of a substrate through a printing process to form a temperature display layer, the substrate is a flexible material to allow attachment to food packaging; S4: covering a protective layer on the temperature display layer, the protective layer is used to protect the temperature display layer from mechanical damage and environmental pollution, while allowing gas to pass through to trigger the enzymatic reaction; S5: drying the temperature display layer to solidify and maintain the biochemical activity of the temperature display layer; Wherein the processing method ensures that the temperature display sticker remains stable in a low-temperature environment until the temperature reaches the predetermined low-temperature threshold.

2. The process for manufacturing a biochemical temperature indicating sticker for low temperature food according to claim 1, wherein, In step S1, the enzyme in the biochemical reaction system is selected from at least one of the redox enzyme class, including glucose oxidase, peroxidase, the substrate is selected from at least one of the chromogenic compound, including o-dianisidine, tetramethyl benzidine, and the biochemical reaction system further comprises a buffer to maintain the pH stability of the reaction system.

3. The processing method of a biochemical temperature display sticker for low-temperature food according to claim 1, wherein in step S1, the predetermined low-temperature threshold is in the range of -20℃ to 10℃, and the predetermined low-temperature threshold is achieved by adjusting the concentration ratio of the enzyme and the substrate in the biochemical reaction system and the composition of the carrier material.

4. The process for manufacturing a biochemical temperature indicating sticker for low temperature food according to claim 1, wherein, In step S2, the carrier material comprises a water-soluble polymer selected from at least one of polyvinyl alcohol, hydroxypropyl methyl cellulose, and the carrier material forms a homogeneous slurry with the biochemical reaction system during the mixing process, and the viscosity of the slurry is adjusted to be in the range of 100-5000 mPa·s by controlling the water content.

5. The method of claim 1, wherein the biochemical temperature indicating sticker for low temperature food is characterized by, In step S3, the printing process uses screen printing or inkjet printing, the screen printing uses a screen pattern to control the shape and thickness of the temperature display layer, and the inkjet printing precisely deposits the slurry through digital control, and the thickness of the formed temperature display layer is 5-50 μm.

6. The method of claim 1, wherein the biochemical temperature indicating sticker for low temperature food is characterized by, In step S4, the protective layer is a gas-permeable film selected from at least one of porous polyethylene, polyurethane film, the protective layer is laminated or coated on the temperature display layer, and has a microporous structure to allow oxygen and water vapor to pass through while blocking liquid and solid pollutants, and the thickness of the protective layer is 10-100 μm.

7. The method of claim 1, wherein the biochemical temperature indicating sticker for low temperature food is characterized by, Before step S3, step S2a is further included: coating an adhesive layer on the substrate, the adhesive layer is composed of pressure-sensitive adhesive or hot melt adhesive, which is used to firmly attach the temperature display sticker to the surface of food packaging, and the adhesive layer remains sticky in a low-temperature environment without affecting the biochemical reaction.

8. A biochemical temperature indicating sticker for low temperature food products, characterized by, manufactured by the processing method as claimed in any one of claims 1-7, comprising: a substrate, which is a flexible material; a temperature display layer disposed on the substrate, comprising a biochemical reaction system, which comprises at least one enzyme and at least one substrate; a protective layer covering the temperature display layer, allowing gas to pass through; wherein the temperature display sticker produces a visible color change by enzymatic reaction when reaching a predetermined low temperature threshold.

9. The biochemical temperature indicating sticker for low temperature food according to claim 8, wherein wherein the temperature display layer further comprises a carrier material, which comprises a water-soluble polymer selected from at least one of polyvinyl alcohol, hydroxypropyl methylcellulose.

10. The biochemical temperature indicating sticker for low temperature food according to claim 8, wherein wherein the protective layer is a gas-permeable film, which is selected from at least one of porous polyethylene, polyurethane film, and has a thickness of 10-100 μm.

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