Starch-based nano-smart label, preparation method and application thereof in visual monitoring of freshness of meat

Abstract

The application discloses a starch-based nano intelligent label, a preparation method and application thereof in visual monitoring of meat freshness. The method uses debranched starch, prolamin and anthocyanin as raw materials, fully stirs and mixes, and then is ultrasonically homogenized. After centrifugation, the composite coagulation layer is taken as a spinning solution, and then the starch-based nano intelligent label is prepared through electrospinning. The average fiber diameter of the starch-based nano intelligent label is 450-600 nm, and the water contact angle is 100-120 DEG. After the starch-based nano intelligent label is applied to meat product freshness monitoring after volatile acid fumigation, the color of the starch-based nano intelligent label presents color changes of red, pink and purple corresponding to the aggravation of the meat product corruption degree, the ΔE value is greater than 5, and the visual monitoring of the meat freshness is realized in a food-grade safe and reliable manner.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of food non-destructive monitoring, and relates to a starch-based nano intelligent label, a preparation method and application thereof in visual monitoring of meat freshness. BACKGROUND

[0002] Meat products are prone to spoilage during storage due to their high protein and fat content, which can lead to food safety problems, so it is necessary to monitor the freshness of meat. Among the common methods for monitoring the freshness of meat (sensory evaluation, total volatile nitrogen, and total bacterial count), visual monitoring is one of the simplest, most convenient, and real-time intelligent methods.

[0003] During the spoilage process of meat products, some volatile amine gases (dimethylamine, ammonia, and trimethylamine) are produced, which causes changes in the pH of the storage environment. These changes can be visually displayed using pH indicators, achieving intelligent and visual monitoring of meat freshness. However, current intelligent labels for visual monitoring of meat freshness are mostly polymeric cast films, such as polyvinyl alcohol and polypropylene (Feng Qingxia et al., Packaging Engineering, 2019, 40(19): 138-144), resulting in low sensitivity and high detection limit of the indicator label. Moreover, chemical indicators such as methyl red and bromothymol blue are often chosen (Dong Yue et al., Packaging Engineering, 2021, 42(19): 129-135), limiting their application and development in the food industry.

[0004] Starch, as a natural biopolymer, is widely available, safe, and cost-effective, biodegradable, and biocompatible, making it an excellent food packaging substrate with excellent performance. Starch nanofiber membranes prepared by electrospinning technology have a large specific surface area and porosity, which can greatly improve the efficiency of contact reactions, making them a potential nano-scale indicator label (Sun Wuliang et al., Transactions of the Chinese Agricultural Engineering Society, 2021, 37(04): 24-30). Compared to "wet" starch electrospinning, "dry" starch electrospinning reduces the use of organic solvents and long drying times (Li et al., Carbohydrate Polymers, 2021, 258: 116933). Although Li et al. used high amylose starch as a raw material and water as a solvent, and after high-speed shear dispersion, they could directly electrospun starch nanofibers (Patent CN113882024B), but the surface of the product still has many hydrophilic groups of hydroxyl groups, which have poor hydrophobicity, making it difficult to apply to the field of hydrophobic food intelligent labels. SUMMARY

[0005] The purpose of this invention is to provide a starch-based nano-smart tag, its preparation method, and its application in visually monitoring meat freshness. The method uses debranched starch, prolyl protein, and anthocyanins as raw materials. After thorough mixing and ultrasonic homogenization, the composite aggregate layer is collected after centrifugation and used as a spinning solution. Starch-based nano-smart tags are then prepared by electrospinning, with an average fiber diameter of 450–600 nm and a water contact angle of 100–120°. After fumigation with volatile acid, the tags are applied to meat product freshness monitoring. The tags exhibit a color change from red to pink to purple, with ΔE values ​​all greater than 5, achieving the effect of visually monitoring meat freshness.

[0006] The technical solution for achieving the objective of this invention is as follows:

[0007] The preparation method of starch-based nano-smart tags includes the following specific steps:

[0008] (1) Preparation of electrospinning solution: The anthocyanin solution is added dropwise to the mixture of starch debranching solution and alcohol-soluble protein solution, and stirred thoroughly until a homogeneous mixture is formed. The mixture is then homogenized by ultrasonication, centrifuged, and the middle composite coagulated layer is taken. In the mixture, the concentration of anthocyanin is 0.01-0.03 g / mL, the concentration of starch debranching solution is 0.2-0.3 g / mL, the concentration of alcohol-soluble protein is 0.15-0.25 g / mL, and the volume ratio of acetic acid, ethanol and water is 0.5-1.5:9-7.5:0.5-1.

[0009] (2) Preparation of starch-based nano-smart tags by electrospinning: Using the composite cohesive layer as the electrospinning solution, starch-based nano-smart tags were obtained by electrospinning technology. The electrospinning conditions were: voltage of 15-25kV, spinning distance of 10-20cm, spinning needle size of 18-23G, flow rate of 0.6-1mL / h, and roller speed of 50-100rpm.

[0010] Preferably, in step (1), the anthocyanins are derived from one or two of blueberries, purple sweet potatoes, or mulberries; the starch is derived from one or two of corn, potatoes, or cassava; and the prolysin is derived from one or two of corn or wheat.

[0011] Preferably, in step (1), the solvent for the anthocyanin solution is a 60-80% aqueous ethanol solution, the solvent for the starch debranching solution is a 3-6% aqueous acetic acid solution, and the solvent for the alcohol-soluble protein solution is a 70-90% aqueous ethanol solution.

[0012] In step (1), the starch debranching solution is prepared using existing conventional methods, specifically: placing the starch solution in a water bath at 60–70°C, adding 20–40 U / g starch debranching enzyme, and enzymatically hydrolyzing for 6–8 hours to obtain the starch debranching solution. The starch debranching enzyme is one or two of pullulanase, saccharifying enzyme, or β-amylase; the molecular weight of the starch debranching solution is 1–3 × 10⁻⁶. 5 g / mol.

[0013] Preferably, in step (1), the ultrasonic homogenization time is 1 to 2 minutes.

[0014] Preferably, in step (2), the electrospinning time is 24 hours or more.

[0015] Preferably, in step (2), the electrospinning temperature is 20-30°C and the electrospinning humidity is 45-55%.

[0016] Preferably, in step (2), the average fiber diameter of the starch-based nano-smart tag is 450-600 nm; the water contact angle of the starch-based nano-smart tag is 100-120°.

[0017] This invention provides starch-based nano-smart tags prepared by the above-described method.

[0018] Furthermore, the present invention provides the application of the above-mentioned starch-based nano-smart tags in the visual monitoring of meat freshness.

[0019] Specifically, the application method is as follows: the starch-based nano-smart tags are fumigated with volatile acid, and then pasted on the top of the inside of a transparent food storage box. Fresh meat products are placed in the food storage box and refrigerated. During this period, the color change of the starch-based nano-smart tags is recorded and the color value of the starch-based nano-smart tags is analyzed to achieve visual monitoring of the freshness of fresh meat.

[0020] Furthermore, the volatile acid is one or both of hydrochloric acid and acetic acid; the fumigation distance is 5-8 cm; and the fumigation time is 1-3 min.

[0021] Furthermore, fresh meat products include pork, beef, or fish.

[0022] Furthermore, chromaticity values ​​include luminance values ​​(L). * ), redness value (a * ), yellowness value (b) * ).

[0023] Furthermore, the method for monitoring and analyzing the freshness of fresh meat products is as follows: record the color values ​​under the corresponding storage conditions, and calculate the total color difference ΔE of the starch-based nano-smart label under the corresponding storage conditions according to the following formula:

[0024]

[0025] In the formula, L * a * and b * The brightness, redness, and yellowness values ​​of the starch-based nano-smart tags under corresponding storage conditions; L0 * a0 * and b0 * The initial brightness, redness, and yellowness values ​​of the starch-based nano-smart label are ΔE; the larger the ΔE, the higher the degree of spoilage.

[0026] Compared with the prior art, the advantages of this invention are:

[0027] (1) The raw materials used in this invention are all food-grade biological raw materials, such as anthocyanins, debranched starch and alcohol-soluble protein. The starch-based nano-smart labels prepared by them have the characteristics of "safe and non-toxic" and "environmentally friendly", and can be applied to food packaging and non-destructive visual monitoring.

[0028] (2) This invention solves the problem of poor hydrophobicity of starch-based materials by cross-linking the interaction between alcohol-soluble protein and debranched starch, and organically combines it with electrospinning technology to solve the problem of excessively large size of starch-based materials. The average fiber diameter of the starch-based nano-smart tag in this invention is 450-600 nm, and its water contact angle is 100-120°, exhibiting excellent hydrophobicity.

[0029] (3) In this invention, the solutions of debranched starch, alcohol-soluble protein, and anthocyanins are thoroughly stirred and mixed, then ultrasonically homogenized. After centrifugation, they can be separated into three layers: an upper solvent layer (transparent), a middle composite coagulation layer (pink and translucent), and a lower precipitate layer (a mixture of insoluble substances of various colors). The middle composite coagulation layer is formed by the "physical cross-linking" of debranched starch and alcohol-soluble protein to form a network structure, thereby loading anthocyanins and forming a stable three-dimensional network structure. This invention uses the composite coagulation layer as the spinning solution, resulting in good spinning effect.

[0030] (4) After being treated with volatile acid, the anthocyanins in the starch-based nano-smart tag of the present invention are in an "acidic" state (corresponding color is red). Therefore, it is highly sensitive to amine gases produced by the spoilage of meat products. As the refrigeration time of meat products is extended, the degree of spoilage of meat products intensifies, and the anthocyanins show a color change of red → pink → purple. The ΔE values ​​are all greater than 5, realizing the effect of visually monitoring the freshness of meat. Attached Figure Description

[0031] Figure 1 The image shows a scanning electron microscope (SEM) image of the starch-based nano-smart tag in Comparative Example 3.

[0032] Figure 2The contact angle diagram of the starch-based nano-smart tag in Comparative Example 3;

[0033] Figure 3 The image shows a scanning electron microscope (SEM) image of the starch-based nano-smart tag in Comparative Example 4.

[0034] Figure 4 The image shows a scanning electron microscope (SEM) image of the starch-based nano-smart tag in Comparative Example 5.

[0035] Figure 5 The image shows a scanning electron microscope (SEM) image of the starch-based nano-smart tag in Comparative Example 6.

[0036] Figure 6 The fiber diameter distribution of the starch-based nano-smart tag in Comparative Example 6;

[0037] Figure 7 The contact angle diagram of the starch-based nano-smart tag in Comparative Example 6;

[0038] Figure 8 To visualize and monitor the colorimetric and color difference values ​​of meat freshness using starch-based nano-smart tags in Comparative Example 6;

[0039] Figure 9 This is a scanning electron microscope image of the starch-based nano-smart tag in Example 1;

[0040] Figure 10 This is a fiber diameter distribution diagram of the starch-based nano-smart tag in Example 1;

[0041] Figure 11 This is a contact angle diagram of the starch-based nano-smart tag in Example 1;

[0042] Figure 12 The starch-based nano-smart tag in Example 1 is used for visual monitoring of color and color difference values ​​in meat freshness;

[0043] Figure 13 This is a scanning electron microscope image of the starch-based nano-smart tag in Example 2;

[0044] Figure 14 This is a fiber diameter distribution diagram of the starch-based nano-smart tag in Example 2;

[0045] Figure 15 This is a contact angle diagram of the starch-based nano-smart tag in Example 2;

[0046] Figure 16 The starch-based nano-smart tag in Example 2 is used to visually monitor the color and color difference values ​​in meat freshness.

[0047] Figure 17 This is a scanning electron microscope image of the starch-based nano-smart tag in Example 3;

[0048] Figure 18 This is a fiber diameter distribution diagram of the starch-based nano-smart tag in Example 3;

[0049] Figure 19 This is a contact angle diagram of the starch-based nano-smart tag in Example 3;

[0050] Figure 20 The starch-based nano-smart tag in Example 3 is used to visualize and monitor the color and color difference values ​​in the freshness of meat. Detailed Implementation

[0051] To better understand the present invention, the present invention will be further described below with reference to the accompanying drawings and embodiments, but the scope of protection of the present invention is not limited to the scope described in the embodiments.

[0052] The test methods described in the following examples are as follows:

[0053] 1) Microscopic morphology testing

[0054] The sample was fixed on a metal stage with conductive adhesive, and after vacuum sputtering gold for 90 seconds, the microstructure of the starch-based nano-smart label was observed and photographed using a scanning electron microscope (S-4800Ⅱ, Hitachi, Japan).

[0055] 2) Fiber diameter analysis

[0056] The scanning electron microscope images of starch-based nano-smart tags were analyzed using ImageJ software. Five to ten images were taken for each sample, and each image was sampled 50 to 100 times. After obtaining all fiber diameter data, the average diameter was analyzed.

[0057] 3) Water contact angle test

[0058] The water contact angle of the starch-based nano-smart label was determined using a contact angle meter (JY-82C, Chengde Dingsheng Testing Machine Equipment Co., Ltd.). The "seat drop method" was used to add 10 μL of water droplets to the smooth surface of the starch-based nano-smart label, and images of the water droplets in contact with the starch-based nano-smart label were taken and the corresponding water contact angle values ​​were calculated.

[0059] 4) Colorimetric test

[0060] The colorimetric values ​​of the starch-based nano-smart tags were tested using a colorimeter (ColorMeter SE, Hangzhou Caipu Technology Co., Ltd.). In the colorimetric values, L... * a is the brightness value. * b is the redness value. * This represents the yellowness value.

[0061] 5) Color difference analysis

[0062] Using the initial chromaticity value of the starch-based nano-smart label as a blank control, the total color difference ΔE of the starch-based nano-smart label under the corresponding storage conditions was calculated according to the following formula:

[0063]

[0064] In the formula, L * a * and b * The colorimetric value of the starch-based nano-smart label under the corresponding storage conditions (meat freshness at a spoilage state); L0 * a0 * and b0 * The initial chromaticity value is for the starch-based nano-smart label.

[0065] The corn starch debranching solution used in Comparative Examples 1-6 and Example 1 below was prepared by the following steps: The starch solution was placed in a 60°C water bath, 20 U / g starch debranching enzyme was added, and enzymatic hydrolysis was performed for 8 hours to obtain a solution with a molecular weight of 2 × 10⁻⁶. 5 A g / mol corn starch debranching solution, with pullulanase and β-amylase as the starch debranching enzymes.

[0066] Comparative Example 1

[0067] (1) Preparation of electrospinning solution: Blueberry anthocyanin solution (solvent is 80% ethanol aqueous solution) is added dropwise to a mixed solution of corn starch debranching solution (solvent is 3% acetic acid aqueous solution) and zein solution (solvent is 90% ethanol aqueous solution). In the mixed system, the concentration of blueberry anthocyanin is 0.03 g / mL, the concentration of corn starch debranching solution is 0.1 g / mL, the concentration of zein solution is 0.15 g / mL, and the volume ratio of acetic acid: ethanol: water is 0.5:9:0.5. After thorough mixing, the mixture is ultrasonically homogenized for 2 min. After centrifugation, the composite coagulated layer (the opaque middle layer) is taken, which is the electrospinning solution.

[0068] Tests showed that a mixed solution of debranched corn starch / corn gliadin / blueberry anthocyanins with an excessively low debranching concentration only accounted for about 20% of the entire system in the composite coagulated layer after centrifugation, resulting in low production efficiency and hindering subsequent electrospinning.

[0069] Comparative Example 2

[0070] (1) Preparation of electrospinning solution: Blueberry anthocyanin solution (solvent is 80% ethanol aqueous solution) is added dropwise to a mixed solution of corn starch debranching solution (solvent is 3% acetic acid aqueous solution) and zein solution (solvent is 90% ethanol aqueous solution). In the mixed system, the concentration of blueberry anthocyanin is 0.03 g / mL, the concentration of corn starch debranching solution is 0.4 g / mL, the concentration of zein solution is 0.15 g / mL, and the volume ratio of acetic acid: ethanol: water is 0.5:9:0.5. After thorough mixing, the mixture is ultrasonically homogenized for 2 min. After centrifugation, the composite coagulated layer (the opaque middle layer) is taken, which is the electrospinning solution.

[0071] Tests showed that the electrospinning solution of debranched corn starch / corn gliadin / blueberry anthocyanins with an excessively high starch debranching concentration had too high viscosity and exhibited a gel-like state, making subsequent electrospinning impossible.

[0072] Comparative Example 3

[0073] (1) Preparation of electrospinning solution: Blueberry anthocyanin solution (solvent is 80% ethanol aqueous solution) is added dropwise to corn starch debranching solution (solvent is 3% acetic acid aqueous solution). In the mixed system formed, the concentration of blueberry anthocyanin is 0.03 g / mL, the concentration of corn starch debranching is 0.2 g / mL, and the volume ratio of acetic acid: ethanol: water is 0.5:9:0.5. After thorough mixing, the mixture is ultrasonically homogenized for 2 min. After centrifugation, the composite coagulated layer (the middle opaque layer) is taken, which is the electrospinning solution.

[0074] (2) Preparation of starch-based nano-smart tags by electrospinning: The electrospinning solution in step (1) is loaded into a syringe and connected to an 18G spinning needle. The electrospinning parameters are: voltage of 15kV, spinning distance of 15cm, syringe flow rate of 0.8mL / h, and roller speed of 50rpm. Starch-based nano-smart tags can be obtained after electrospinning (temperature of 25℃ and humidity of 45%) for 24h.

[0075] Tests showed that debranched corn starch / blueberry anthocyanin composite solution without added alcohol-soluble protein could still be electrospun to obtain a nanofiber network structure. Figure 1 The starch-based nano-smart tag has a water contact angle of 40°. Figure 2 This indicates that it has good hydrophilicity but poor hydrophobicity, and cannot achieve the ideal hydrophobic effect of starch-based nano-smart tags.

[0076] Comparative Example 4

[0077] (1) Preparation of electrospinning solution: Blueberry anthocyanin solution (solvent is 80% ethanol aqueous solution) is added dropwise to a mixed solution of corn starch debranching solution (solvent is 3% acetic acid aqueous solution) and zein solution (solvent is 90% ethanol aqueous solution). In the mixed system, the concentration of blueberry anthocyanin is 0.03 g / mL, the concentration of corn starch debranching solution is 0.2 g / mL, the concentration of zein solution is 0.2 g / mL, and the volume ratio of acetic acid: ethanol: water is 0.5:9:0.5. After thorough mixing, the mixture is sonicated for 2 min, centrifuged, and the solution layer is taken, which is the electrospinning solution.

[0078] (2) Preparation of starch-based nano-smart tags by electrospinning: The electrospinning solution in step (1) is loaded into a syringe and connected to an 18G spinning needle. The electrospinning parameters are: voltage of 25kV, spinning distance of 18cm, syringe flow rate of 0.6mL / h, and roller speed of 80rpm. Starch-based nano-smart tags can be obtained after electrospinning (temperature of 30℃ and humidity of 55%) for 24h.

[0079] Testing revealed that the poor spinning effect was due to the failure to collect the composite coagulated layer (the opaque middle layer) after centrifugation of the corn starch debranching / zeadrin / blueberry anthocyanin mixed solution in step (1). The microstructure showed a large number of particles with varying shapes, and no fibers were found. Figure 3 As shown.

[0080] Comparative Example 5

[0081] (1) Preparation of electrospinning solution: Add blueberry anthocyanin solution (solvent is 80% ethanol aqueous solution) dropwise to a mixed solution of corn starch debranching solution (solvent is 3% acetic acid aqueous solution) and zein solution (solvent is 90% ethanol aqueous solution). In the mixed system, the concentration of blueberry anthocyanin is 0.03 g / mL, the concentration of corn starch debranching solution is 0.2 g / mL, the concentration of zein is 0.2 g / mL, and the volume ratio of acetic acid: ethanol: water is 0.5:9:0.5. Stir and mix thoroughly, and after centrifugation, take the composite coagulated layer (the middle opaque layer), which is the electrospinning solution.

[0082] (2) Preparation of starch-based nano-smart tags by electrospinning: The electrospinning solution in step (1) is loaded into a syringe and connected to a 23G spinning needle. The electrospinning parameters are: voltage of 20kV, spinning distance of 15cm, syringe flow rate of 0.8mL / h, and roller speed of 100rpm. Starch-based nano-smart tags can be obtained after electrospinning (temperature of 25℃ and humidity of 50%) for 24h.

[0083] Testing revealed that because the corn starch debranching / zeaxanthin / blueberry anthocyanin mixture in step (1) was not ultrasonically homogenized before centrifugation, the degree of "physical cross-linking" of the three components was low, resulting in poor spinning effect. Its microstructure exhibited a coexistence of nanofibers and "beads," such as... Figure 4 As shown.

[0084] Comparative Example 6

[0085] (1) Preparation of electrospinning solution: Blueberry anthocyanin solution (solvent is 80% ethanol aqueous solution) is added dropwise to a mixed solution of corn starch debranching solution (solvent is 3% acetic acid aqueous solution) and zein solution (solvent is 90% ethanol aqueous solution). In the mixed system, the concentration of blueberry anthocyanin is 0.03 g / mL, the concentration of corn starch debranching solution is 0.2 g / mL, the concentration of zein solution is 0.25 g / mL, and the volume ratio of acetic acid: ethanol: water is 0.5:9:0.5. After thorough mixing, the mixture is ultrasonically homogenized for 2 min. After centrifugation, the composite coagulated layer (the opaque middle layer) is taken, which is the electrospinning solution.

[0086] (2) Preparation of starch-based nano-smart tags by electrospinning: The electrospinning solution in step (1) is loaded into a syringe and connected to a 20G spinning needle. The electrospinning parameters are: voltage of 15kV, spinning distance of 10cm, syringe flow rate of 0.8mL / h, and roller speed of 100rpm. Starch-based nano-smart tags can be obtained after electrospinning (temperature of 25℃ and humidity of 45%) for 24h.

[0087] (3) Visual monitoring of beef freshness using starch-based nano-smart tags: The starch-based nano-smart tags from step (2) were directly affixed to the top of the inside of a transparent food storage container. 100g of fresh beef was placed in the container and refrigerated. During this period, color changes were recorded and analyzed using a smartphone. * a * b * and ΔE value.

[0088] Testing revealed that the starch-based nano-smart tags obtained in step (2) exhibited a network structure composed of interwoven nanofibers. Figure 5 The average fiber diameter is 575 nm. Figure 6 ), and its water contact angle is 118°. Figure 7 It has good hydrophobicity, but no obvious color change occurred during the fresh beef preservation and refrigeration process in step (3), and its ΔE was 2.6 ( Figure 8 The color change is within the range that is not visible to the naked eye, which may be related to the fact that the starch-based nano-smart label has not undergone volatile acid fumigation treatment.

[0089] Example 1

[0090] The preparation method of starch-based nano-smart tags and their application in visual monitoring of meat freshness includes the following steps:

[0091] (1) Preparation of electrospinning solution: Blueberry anthocyanin solution (solvent is 80% ethanol aqueous solution) is added dropwise to a mixed solution of corn starch debranching solution (solvent is 3% acetic acid aqueous solution) and zein solution (solvent is 90% ethanol aqueous solution). In the mixed system, the concentration of blueberry anthocyanin is 0.01 g / mL, the concentration of corn starch debranching solution is 0.25 g / mL, the concentration of zein solution is 0.15 g / mL, and the volume ratio of acetic acid: ethanol: water is 0.5:9:0.5. After thorough mixing, the mixture is ultrasonically homogenized for 2 min. After centrifugation, the composite coagulated layer (the opaque middle layer) is taken, which is the electrospinning solution.

[0092] (2) Preparation of starch-based nano-smart tags by electrospinning: The electrospinning solution in step (1) is loaded into a syringe and connected to an 18G spinning needle. The electrospinning parameters are: voltage of 15kV, spinning distance of 20cm, syringe flow rate of 1mL / h, and roller speed of 80rpm. Starch-based nano-smart tags can be obtained after electrospinning (temperature of 25℃ and humidity of 45%) for 24h.

[0093] (3) Visual monitoring of fish freshness using starch-based nano-smart tags: The starch-based nano-smart tags from step (2) were fumigated with hydrochloric acid (fumigation distance 8cm; fumigation time 1min), and then pasted onto the top of the inside of a transparent food storage box. 100g of fresh fish was placed in the food storage box and refrigerated. During this period, the color change was recorded using a smartphone and the L value was analyzed. * a * b * and ΔE value.

[0094] Testing revealed that the starch-based nano-smart tags obtained in step (2) exhibited a network structure composed of interwoven nanofibers. Figure 9 The average fiber diameter is 450 nm. Figure 10 ), and its water contact angle is 100°. Figure 11 ), with good hydrophobicity; and during the fresh fish meat preservation and refrigeration process in step (3), a significant color change of red → pink → purple appeared, with a ΔE value of 5.8 (>5; Figure 12 This allows for the visual monitoring of meat freshness.

[0095] Example 2

[0096] The preparation method of starch-based nano-smart tags and their application in visual monitoring of meat freshness includes the following steps:

[0097] (1) Preparation of electrospinning solution: Blueberry anthocyanin solution (solvent: 80% ethanol aqueous solution) was added dropwise to potato starch debranching solution (solvent: 3% acetic acid aqueous solution; preparation conditions: starch debranching enzymes were pullulanase and β-amylase; starch debranching enzyme concentration was 20 U / g; enzymatic hydrolysis temperature was 60℃; enzymatic hydrolysis time was 8 h; the molecular weight of the resulting starch debranching solution was 3 × 10⁻⁶. 5 In a mixed solution of acetic acid, ethanol, and water (90% ethanol aqueous solution), the concentration of blueberry anthocyanins was 0.03 g / mL, the concentration of debranched potato starch was 0.3 g / mL, the concentration of wheat gliadin was 0.2 g / mL, and the volume ratio of acetic acid:ethanol:water was 1.5:7.5:1. After thorough mixing, the mixture was ultrasonically homogenized for 1.5 min, centrifuged, and the composite coagulated layer (the opaque middle layer) was taken, which is the electrospinning solution.

[0098] (2) Preparation of starch-based nano-smart tags by electrospinning: The electrospinning solution in step (1) is loaded into a syringe and connected to a 23G spinning needle. The electrospinning parameters are: voltage of 20kV, spinning distance of 10cm, syringe flow rate of 0.6mL / h, and roller speed of 50rpm. Starch-based nano-smart tags can be obtained after electrospinning (temperature of 30℃ and humidity of 55%) for 24h.

[0099] (3) Visual monitoring of pork freshness using starch-based nano-smart tags: The starch-based nano-smart tags from step (2) were fumigated with acetic acid (fumigation distance 6.5cm; fumigation time 2min), and then pasted on the top of the inside of a transparent food storage box. 150g of fresh pork was placed in the food storage box and refrigerated. During this period, the color change was recorded using a smartphone and the L value was analyzed. * a * b * and ΔE value.

[0100] Testing revealed that the starch-based nano-smart tags obtained in step (2) exhibited a network structure composed of interwoven nanofibers. Figure 13 The average fiber diameter is 551 nm. Figure 14 ), and its water contact angle is 112°. Figure 15 ), with good hydrophobicity; and during the fresh fish and pork preservation and refrigeration process in step (3), a significant color change of red → pink → purple appeared, with a ΔE value of 8.3 (>5); Figure 16 This allows for the visual monitoring of meat freshness.

[0101] Example 3

[0102] The preparation method of starch-based nano-smart tags and their application in visual monitoring of meat freshness includes the following steps:

[0103] (1) Preparation of electrospinning solution: Purple sweet potato anthocyanin solution (solvent: 80% ethanol aqueous solution) was added dropwise to cassava starch debranching solution (solvent: 3% acetic acid aqueous solution; preparation conditions: starch debranching enzymes were pullulanase and saccharifying enzyme; starch debranching enzyme concentration was 30 U / g, enzymatic hydrolysis temperature was 65℃, and enzymatic hydrolysis time was 7 h; the molecular weight of the resulting starch debranching solution was 2 × 10⁻⁶. 5 In a mixed solution of acetic acid, ethanol, and water (90% ethanol aqueous solution), the concentration of purple sweet potato anthocyanins was 0.02 g / mL, the concentration of debranched cassava starch was 0.2 g / mL, the concentration of acetic acid was 0.25 g / mL, and the volume ratio of acetic acid:ethanol:water was 1.5:8:0.5. After thorough mixing, the mixture was ultrasonically homogenized for 2 min, and after centrifugation, the composite coagulated layer (the middle opaque layer) was taken, which is the electrospinning solution.

[0104] (2) Preparation of starch-based nano-smart tags by electrospinning: The electrospinning solution in step (1) is loaded into a syringe and connected to a 20G spinning needle. The electrospinning parameters are: voltage of 18kV, spinning distance of 15cm, syringe flow rate of 0.8mL / h, and roller speed of 80rpm. Starch-based nano-smart tags can be obtained after electrospinning (temperature of 25℃ and humidity of 45%) for 24h.

[0105] (3) Visual monitoring of beef freshness using starch-based nano-smart tags: The starch-based nano-smart tags from step (2) were subjected to acetic acid fumigation (fumigation distance 5cm; fumigation time 3min), and then pasted onto the top of the inside of a transparent food storage container. 200g of fresh beef was placed in the container and refrigerated. During this period, the color change was recorded using a smartphone and the L value was analyzed. * a * b * and ΔE value.

[0106] Testing revealed that the starch-based nano-smart tags obtained in step (2) exhibited a network structure composed of interwoven nanofibers. Figure 17 The average fiber diameter is 600 nm. Figure 18 ), and its water contact angle is 120°. Figure 19 ), with good hydrophobicity; and during the fresh beef preservation and refrigeration process in step (3), a significant color change of red → pink → purple appeared, with a ΔE value of 9.6 (>5); Figure 20 This allows for the visual monitoring of meat freshness.

Claims

1. A method for preparing starch-based nano-smart tags, characterized in that, The specific steps are as follows: (1) Preparation of electrospinning solution: Anthocyanin solution is added dropwise to a mixture of starch debranching solution and alcohol-soluble protein solution, and stirred thoroughly until a homogeneous mixture is formed. The mixture is then homogenized by ultrasonication, centrifuged, and the middle composite coagulated layer is taken. In the mixture, the concentration of anthocyanin is 0.01~0.03 g / mL, the concentration of starch debranching is 0.2~0.3 g / mL, the concentration of alcohol-soluble protein is 0.15~0.25 g / mL, and the volume ratio of acetic acid, ethanol and water is 0.5~1.5:9~7.5:0.5~1. The starch debranching solution is prepared by the following steps: the starch solution is placed in a 60~70 ℃ water bath, 20~40 U / g starch debranching enzyme is added, and enzymatic hydrolysis is performed for 6~8 h to obtain the starch debranching solution. The starch debranching enzyme is one or two of pullulanase, saccharifying enzyme or β-amylase. The molecular weight of the starch debranching solution is 1~3×10 5 g / mol; (2) Preparation of starch-based nano-smart tags by electrospinning: Using the composite cohesive layer as the electrospinning solution, starch-based nano-smart tags were obtained by electrospinning technology. The electrospinning conditions were: voltage of 15~25 kV, spinning distance of 10~20 cm, spinning needle size of 18~23 G, flow rate of 0.6~1 mL / h, and roller speed of 50~100 rpm.

2. The preparation method according to claim 1, characterized in that, In step (1), anthocyanins are derived from one or two of blueberries, purple sweet potatoes, or mulberries; starch is derived from one or two of corn, potatoes, or cassava; and alcohol-soluble protein is derived from one or two of corn or wheat. The solvent for the anthocyanin solution is a 60-80% aqueous ethanol solution, the solvent for the starch debranching solution is a 3-6% aqueous acetic acid solution, and the solvent for the alcohol-soluble protein solution is a 70-90% aqueous ethanol solution.

3. The preparation method according to claim 1, characterized in that, In step (1), the ultrasonic homogenization time is 1~2 min; in step (2), the electrospinning time is more than 24 h, the electrospinning temperature is 20~30 ℃, the electrospinning humidity is 45~55%, the average fiber diameter of the starch-based nano-smart label is 450~600 nm, and the water contact angle of the starch-based nano-smart label is 100~120 °.

4. Starch-based nano-smart tags prepared by any one of the preparation methods according to claims 1 to 3.

5. The application of the starch-based nano-smart tag according to claim 4 in the visual monitoring of meat freshness.

6. The application according to claim 5, characterized in that, The application method is as follows: the starch-based nano-smart tags are fumigated with volatile acid, and then pasted on the top of the inside of a transparent food storage box. Fresh meat products are placed in the food storage box and refrigerated. During this period, the color change of the starch-based nano-smart tags is recorded and the color value of the starch-based nano-smart tags is analyzed to achieve visual monitoring of the freshness of fresh meat products.

7. The application according to claim 6, characterized in that, The volatile acid is one or both of hydrochloric acid and acetic acid; the fumigation distance is 5-8 cm; the fumigation time is 1-3 min.

8. The application according to claim 6, characterized in that, Fresh meat products include pork, beef, or fish.

9. The application according to claim 6, characterized in that, The method for monitoring and analyzing the freshness of fresh meat products is as follows: record the color values ​​under the corresponding storage conditions, and calculate the total color difference Δ of the starch-based nano-smart tags under the corresponding storage conditions according to the following formula. E : ， In the formula, L * , a * and b * The brightness, redness, and yellowness values ​​of the starch-based nano-smart tags under corresponding storage conditions; L 0 * , a 0 * and b 0 * The initial brightness, redness, and yellowness values ​​of the starch-based nano-smart tag; Δ E The larger the size, the higher the level of corruption.

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