A smart label with high sensitivity and low mobility and preparation method thereof

Abstract

The present invention discloses a smart label with both high sensitivity and low mobility and a preparation method thereof, and belongs to the technical field of food packaging. The present invention first uses lipase and organic acid to hydrophobically modify anthocyanin to obtain acylated anthocyanin; then the acylated anthocyanin and the oil phase gelling agent are dissolved in vegetable oil as the oil phase, and the thermoreversible gel aqueous solution is used as the water phase, the two are mixed, and the gel is quickly cooled to obtain a smart label. The smart label prepared by the present invention has both high sensitivity and low mobility, and the preparation method is simple, green, pollution-free, and low in energy consumption; compared with the smart label prepared by the original anthocyanin, the external aqueous phase of the smart label prepared by the present invention can protect the leakage of anthocyanin and ensure the entry of pH sensing signals, and the finally prepared smart label has improved stability, low mobility and good sensing performance.

Description

Technical Field

[0001] The invention relates to an intelligent label with high sensitivity and low mobility and a preparation method thereof, belonging to the technical field of food packaging. Background Art

[0002] With the rapid development of social economy, the consumption of food in the form of commodities is increasing, including a large number of fresh products. At the same time, consumers' awareness of healthy eating is increasing, and they are also very concerned about the quality and safety of food. Fresh food is easily affected by external microorganisms, endogenous enzymatic reactions and other factors in an unsuitable environment, which reduces its quality or even spoils, loses its nutritional and commercial value. Therefore, it is very necessary to package fresh food. Conventional food packaging only serves to separate food from external pollution sources and provide information about commodity production, but cannot provide information about food quality.

[0003] Freshness-indicating smart labels directly indicate the microbial conditions in food by responding to the metabolism of microorganisms during the growth period. Bacterial growth labels indicate the number of pathogenic bacteria, and the response principle can be to react with certain metabolites (volatile or non-volatile), or to establish a pathogen detection system based on the principle of immunochemical reaction, or pH dyes to detect volatile biogenic amines produced by food spoilage to show freshness (threshold).

[0004] The preparation of freshness-indicating smart labels is usually achieved by simply mixing pigments with sensing functions (such as anthocyanins) with traditional packaging materials (starch, polymers, etc.). However, the smart labels prepared by mixing usually have problems such as poor pigment sensitivity and high mobility, which greatly limits the application of smart labels.

[0005] At present, smart gel is a method to solve the problem of "poor pigment sensitivity and high mobility". It is usually formed by embedding emulsion gel to control the migration of pigments. Due to the water solubility of anthocyanins, it is often only possible to reduce the migration of pigments by preparing oil-in-water emulsion gel. However, the external oil phase cannot allow the pH signal to pass, which will reduce the sensing sensitivity of the smart gel and cannot be actually applied to food freshness detection. Moreover, conventional smart labels used for freshness indication are mostly obtained by rapid cooling of thermoreversible gel. The gel obtained in this way has poor uniformity and processability, and is not easy to be applied in actual production processes. Summary of the invention

[0006] The purpose of the present invention is to solve the technical problems that the existing smart labels have poor sensitivity, high pigment mobility and cannot have both high sensitivity and low mobility.

[0007] In order to solve the above problems, the present invention provides a smart label with both high sensitivity and low mobility and a preparation method thereof, that is, firstly hydrophobically modifying anthocyanin with lipase and organic acid to obtain acylated anthocyanin; then dissolving the acylated anthocyanin and oil phase gelling agent in vegetable oil as the oil phase, using a thermoreversible gel aqueous solution as the water phase, mixing the two, and rapidly cooling to form a gel to obtain a smart label. The smart label prepared by the present invention has both high sensitivity and low mobility, and the preparation method is simple, green, pollution-free, and low in energy consumption; compared with the smart label prepared from the original anthocyanin, the external aqueous phase of the smart label prepared by the present invention can both protect the leakage of anthocyanin and ensure the entry of pH sensing signals, and the finally prepared smart label has improved stability, low mobility and good sensing performance.

[0008] The first object of the present invention is to provide a method for preparing a smart label with high sensitivity and low mobility, comprising the following steps:

[0009] Acylated anthocyanin and oil phase gelling agent are dissolved in vegetable oil as the oil phase, and the thermoreversible gel aqueous solution is used as the water phase. The water phase and the oil phase are evenly mixed in a volume ratio of 7:3-4:1, rapidly cooled to form a gel, and allowed to stand to obtain a smart label with both high sensitivity and low mobility.

[0010] In one embodiment of the present invention, the preparation method of acylated anthocyanin is as follows:

[0011] Anthocyanins, lipase, organic acids, The molecular sieves are mixed and dispersed in an organic solvent, and heated to carry out an acylation reaction. After the reaction is completed, the organic solvent and unreacted raw materials are filtered to remove the organic solvent and the unreacted raw materials, and the mixture is dried to obtain acylated anthocyanins;

[0012] Wherein, the anthocyanin is one or more of blueberry anthocyanin, roselle anthocyanin, grape anthocyanin, mulberry anthocyanin, black bean anthocyanin, and purple sweet potato anthocyanin;

[0013] The lipase is one or more of Novozym 435, lipase acrylic resin (recombinant), and lipase (Candida); the enzyme activity of Novozym 435 is ≥5000U / g, the CAS code of lipase acrylic resin (recombinant) is 9001-62-1, and the enzyme activity is ≥5000U / g; the enzyme activity of lipase (Candida) is ≥5000U / g;

[0014] The organic acid is ferulic acid or caffeic acid;

[0015] The organic solvent is one or more of n-butanol, isopropanol, tetrahydrofuran, acetonitrile, tert-amyl alcohol, pyrimidine and acetone;

[0016] Anthocyanins, lipase, organic acids, The usage ratio of molecular sieve and organic solvent is 0.1g: 0.2-0.4g: 1.2-1.4g: 2-4g: 30-60mL;

[0017] The acylation reaction is carried out by heating at 40-60°C for 20-30h;

[0018] Filtration is a suction filtration, the purpose is to remove lipase, Molecular sieves;

[0019] Removing the organic solvent and unreacted raw materials involves removing the organic solvent by rotary evaporation, followed by re-dissolving, and passing the re-dissolved mixture through a filter membrane to remove organic acid;

[0020] The drying is freeze-drying.

[0021] In one embodiment of the present invention, the oil phase gelling agent is one or both of beeswax and glycerol monooleate, and the mass ratio of beeswax to glycerol monooleate is 2-4:1.

[0022] In one embodiment of the present invention, the usage ratio of acylated anthocyanin, oil phase gelling agent and vegetable oil is 0.6 g: 3-5 g: 40-60 mL.

[0023] In one embodiment of the present invention, the vegetable oil is one or more of soybean oil, peanut oil, rapeseed oil and sesame oil.

[0024] In one embodiment of the present invention, the thermoreversible gel is one or more of curdlan, gelatin, and agar.

[0025] In one embodiment of the present invention, the usage ratio of the thermoreversible gel to water in the thermoreversible gel aqueous solution is 2-4 g:120 mL.

[0026] In one embodiment of the present invention, the water phase and the oil phase need to be stirred at 70-90° C. for 20-40 min during preparation.

[0027] In one embodiment of the present invention, the high-speed shearing is 10000-14000 rpm high-speed shearing for 2-5 min.

[0028] In one embodiment of the present invention, the rapid cooling is performed by placing the mixture in an ice box.

[0029] In one embodiment of the present invention, the standing is standing at 4° C. for more than 10 hours.

[0030] The second objective of the present invention is to prepare a smart label with high sensitivity and low mobility using the method described in the present invention.

[0031] The third object of the present invention is to use the smart label with high sensitivity and low mobility in packaging materials, wearable materials or degradable materials.

[0032] The fourth objective of the present invention is to use the smart label with high sensitivity and low mobility in the field of food, medicine or agricultural products.

[0033] In one embodiment, the food is a meat product or aquatic product.

[0034] A fifth object of the present invention is to provide a method for detecting the freshness of meat products, wherein the method uses the smart label with high sensitivity and low mobility described in the present invention.

[0035] In one embodiment of the present invention, the method for detecting the freshness of meat products is as follows:

[0036] The smart label with high sensitivity and low mobility described in the present invention is used as a detection matrix, and the freshness of the meat product is determined according to the color change of the smart label.

[0037] The sixth object of the present invention is to provide a method for improving the sensitivity of anthocyanin smart labels and reducing the low mobility of anthocyanin, comprising the following steps:

[0038] Acylated anthocyanin and oil phase gelling agent are dissolved in vegetable oil as the oil phase, and the thermoreversible gel aqueous solution is used as the water phase. The water phase and the oil phase are evenly mixed in a volume ratio of 7:3-4:1, rapidly cooled to form a gel, and allowed to stand to obtain a smart label with both high sensitivity and low mobility.

[0039] Beneficial effects of the present invention:

[0040] (1) The present invention prepares a smart label with both high sensitivity and low mobility based on the color development characteristics of anthocyanins that change with pH and the binding characteristics that acylated (hydrophobic) anthocyanins can be distributed at the interface of the emulsion gel phase, wherein the acylated (hydrophobic) anthocyanins can be better bound and protected by the oil phase, thereby improving their stability and reducing their mobility. The external aqueous phase protects the stability of anthocyanins while not affecting the sensing of the pH signal, thereby forming a smart label with both high sensitivity and low mobility;

[0041] (2) The smart label prepared by the present invention is complete and continuous, has reduced mobility, and has good sensing performance. It can effectively display the freshness of food and the shelf life of food, and can be used in the field of food packaging. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 Actual pictures of smart labels with high sensitivity and low mobility at different water-to-oil ratios prepared in Examples 1 and 2 and Comparative Examples 3 and 4.

[0043] Figure 2 Actual photos of smart tags with high sensitivity and low mobility prepared using different thermoreversible gels in Example 5 and Comparative Examples 6 and 7.

[0044] Figure 3 This is a diagram showing the fat solubility of anthocyanins in the smart labels with high sensitivity and low mobility prepared in Examples 1-4 and Comparative Examples 1, 2, and 5.

[0045] Figure 4 This is a data graph of the fat solubility of anthocyanins in the smart labels with high sensitivity and low mobility prepared in Examples 1, 3, 4 and Comparative Examples 1, 2, 5.

[0046] Figure 5 This is a diagram showing the sensing effect of the smart tag with high sensitivity and low mobility prepared in Example 1 in an ammonia atmosphere.

[0047] Figure 6 This is a diagram showing the migration effect of pigments (anthocyanins) of the smart labels prepared in Examples 1 and 2 and Comparative Examples 4 and 5 after being immersed in water. DETAILED DESCRIPTION

[0048] The present invention is further described below in conjunction with examples, but the examples do not limit the present invention in any form. Unless otherwise specified, the reagents, methods and equipment used in the present invention are conventional reagents, methods and equipment in the art.

[0049] The present invention relates to a determination method:

[0050] 1. Determination of pigment fat solubility:

[0051] n-Octanol and water were mixed and stirred overnight to saturate each other, and then the two phases were separated. The sample was added to the water-saturated n-octanol and the absorbance A1 of the sample at 540 nm was measured. Then, an equal volume of water saturated with n-octanol was added, vortexed and mixed, and after stratification, the upper n-octanol was aspirated and the absorbance A2 was measured again. The pigment lipid solubility log P was calculated by formula (1):

[0052]

[0053] 2. Color development ability determination:

[0054] Sodium hydroxide / hydrochloric acid aqueous solutions with pH = 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, and 12 were prepared respectively. The samples were immersed in sodium hydroxide / hydrochloric acid water with different pH values ​​for 30 min. The color changes of the samples were recorded using a camera. The photo data were converted into CIE L * a * b *Color value, L * Indicates brightness, from 0 (black) to 100 (white); a * Indicates green (-a * ) to red (+a * );b * Indicates blue (-b *) To yellow (+b * ).

[0055] The total color difference (TCD) is calculated using formula (2):

[0056]

[0057] The initial color parameters are expressed as and

[0058] 3. Pigment mobility determination:

[0059] Soak the label in water, take out the solution every other day to measure its absorbance to record its leakage status.

[0060] 4. Determination of sensitivity to ammonia:

[0061] Prepare 100 mg / mL ammonia solution, the test label sample specification is Φ25mm×10mm, pour 10mL of ammonia solution of different concentrations into a 20mm×15mm cylindrical container openly, and place it together with the sample in a 100mm×100mm×20mm square transparent container, and use a camera to record the color change of the sample every 5 minutes.

[0062] The raw materials involved in the present invention are:

[0063] Blueberry anthocyanins (5-25%) were purchased from Nanjing Xinhou Biological Co., Ltd.;

[0064] Lipase (Candida) (enzyme activity ≥ 5000U / g) and beeswax were purchased from Shanghai Titan Technology Co., Ltd.;

[0065] Lipase acrylic resin (recombinant) (enzyme activity ≥ 5000U / g), ferulic acid, methyl ferulate, isooctane, ethyl acetate, glycerol monooleate, and sodium alginate were purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.;

[0066] Lipase (enzyme activity 20000U / g, L874984), caffeic acid, tert-amyl alcohol, n-octanol, and gellan gum were purchased from Shanghai MacLean Biochemical Technology Co., Ltd.;

[0067] Soybean oil was purchased from Yihai Kerry Golden Dragon Fish Cereals, Oils and Foods Co., Ltd.;

[0068] Curdlan, gelatin, and carrageenan were purchased from Shanghai Titan Technology Co., Ltd.

[0069] Example 1

[0070] A method for preparing a smart label with high sensitivity and low mobility comprises the following steps:

[0071] (1) 100 mg of blueberry anthocyanins, 300 mg of lipase acrylic resin (recombinant), 1.35 g of ferulic acid, 3 g of The molecular sieves were mixed and dispersed in 50 mL of tert-amyl alcohol and stirred continuously (stirred at 500 rpm for 10 min); then stirred and reacted in a 50° C. water bath for 24 h to obtain a mixture;

[0072] The mixture was filtered to remove the lipase acrylic resin (recombinant) and molecular sieve, rotary evaporation to remove the organic solvent and reconstitute with water; the reconstituted mixture was filtered through a 0.45 μm filter membrane to remove unreacted organic acid, and freeze-dried at -50°C for 48 hours to obtain acylated anthocyanin powder;

[0073] (2) Dissolve 3 g of beeswax, 1 g of glycerol monooleate, and 0.6 g of acylated anthocyanin powder in 50 mL of soybean oil and stir at 70°C for 30 min as the oil phase; dissolve 2.4 g of curdlan in 120 mL of water and stir at 70°C for 30 min as the water phase;

[0074] Take 14 mL of water phase and mix it with 6 mL of oil phase, shear it at a high speed of 12000 rpm for 2 minutes under a shearing machine, and quickly place it in an ice box to quickly cool it to form a gel, and put it in a 4°C refrigerator to stand for 12 hours, take it out and cut it to obtain a smart label with both high sensitivity and low mobility.

[0075] Example 2

[0076] The aqueous phase in step (2) of Example 1 was adjusted to 16 mL, the oil phase to 4 mL, and the rest was kept consistent with Example 1, thereby obtaining a smart label with both high sensitivity and low mobility.

[0077] Example 3

[0078] The lipase acrylic resin (recombinant) in step (1) of Example 1 was adjusted to lipase (Candida), and the rest was kept the same as Example 1, thereby obtaining a smart label with both high sensitivity and low mobility.

[0079] Example 4

[0080] The ferulic acid in step (1) of Example 1 was adjusted to caffeic acid, and the other steps were kept the same as in Example 1, thereby obtaining a smart tag with both high sensitivity and low mobility.

[0081] Example 5

[0082] The curdlan in step (2) of Example 1 was adjusted to gelatin, and the other parts were kept the same as in Example 1 to obtain a smart label.

[0083] Comparative Example 1

[0084] The lipase acrylic resin (recombinant) in step (1) of Example 1 was adjusted to lipase (L874984), and the rest was kept the same as Example 1 to obtain a smart label.

[0085] Comparative Example 2

[0086] The ferulic acid in step (1) of Example 1 was adjusted to methyl ferulate, and the other steps were kept the same as those of Example 1 to obtain a smart label.

[0087] Comparative Example 3

[0088] The aqueous phase in step (2) of Example 1 was adjusted to 12 mL, the oil phase to 8 mL, and the rest was kept the same as Example 1 to obtain a smart label.

[0089] Comparative Example 4

[0090] The aqueous phase in step (2) of Example 1 was adjusted to 18 mL, the oil phase to 2 mL, and the rest was kept the same as Example 1 to obtain a smart label.

[0091] Comparative Example 5

[0092] The acylation step (1) of Example 1 was omitted, and blueberry anthocyanin was directly used. The smart label was obtained in the same manner as in Example 1.

[0093] Comparative Example 6

[0094] The curdlan in step (2) of Example 1 was adjusted to gellan gum, and the other steps were kept the same as in Example 1 to obtain a smart label.

[0095] Comparative Example 7

[0096] The curdlan in step (2) of Example 1 was adjusted to carrageenan, and the other steps were kept the same as in Example 1 to obtain a smart label.

[0097] The smart labels obtained in Examples 1-4 and Comparative Examples 1-7 were subjected to performance tests, and the test results are as follows:

[0098] Figure 1 The following are the physical pictures of the smart labels with high sensitivity and low mobility prepared in Examples 1 and 2 and Comparative Examples 3 and 4. Figure 1It can be seen that: with the increase of oil content, the label shows a significant decrease in strength, but at the water-oil ratio of 3:2 and 9:1, the shape begins to be difficult to maintain, indicating that the water-oil ratio of 7:3-4:1 is a ratio range that maintains a relatively moderate strength of the label and is convenient for processing.

[0099] Figure 2 The following are the physical pictures of the smart labels with high sensitivity and low mobility prepared in Example 5 and Comparative Examples 6 and 7. Figure 2 It can be seen that Example 5 and Comparative Example 6 have good color uniformity, showing good emulsification characteristics, but Comparative Example 7 shows obvious phase unevenness, which is because the addition of carrageenan affects the emulsification effect and causes premature separation of the two phases, which is not conducive to color development. In terms of mechanical properties, Comparative Example 6 shows the hard and brittle type of gellan gum, which is easy to break during processing and is not suitable for actual production. Comparative Example 7 directly shows the weak elasticity of the oil phase gel due to separation, indicating that it is not suitable for label production.

[0100] Figure 3 The fat solubility effect diagram and data diagram of anthocyanins in the smart labels with high sensitivity and low mobility prepared in Examples 1-4 and Comparative Examples 1, 2, and 5. Figure 3 and Figure 4 It can be seen that comparative example 5, without acylation, showed obvious strong water solubility, which is also Figure 4 It was confirmed that its log P was -0.2, showing a strong hydrophilicity; Examples 1 to 4 showed that after acylation, the fat solubility of anthocyanins was significantly improved, and the color was concentrated in the upper n-octanol phase. The improvement of fat solubility will help reduce the leakage of pigments and the formation of subsequent water-in-oil emulsions; the fat solubility improvement effect of Comparative Examples 1 and 2 was significantly poor, indicating that ordinary lipase and methyl ferulate could not undergo a good enzymatic acylation reaction with anthocyanins to improve the fat solubility of anthocyanins.

[0101] Figure 5 This is a diagram showing the sensing effect of the smart label with high sensitivity and low mobility prepared in Example 1 in an ammonia atmosphere. Table 1 shows the color change of the smart label of Example 1 in an ammonia atmosphere over time. Figure 5 It can be seen from Table 1 that in an ammonia atmosphere, the smart label produces a color response of ΔE>5, indicating that the smart label prepared in Example 1 has a good response capability to ammonia and can be used for food freshness detection.

[0102] Table 1 Color changes of the smart label of Example 1 in ammonia atmosphere over time

[0103]

[0104]

[0105] Figure 6 The figure shows the migration effect of the pigment (anthocyanin) of the smart labels prepared in Examples 1 and 2 and Comparative Examples 4 and 5 after being immersed in water. Figure 6 It can be seen that the labels prepared in Examples 1 and 2 still maintained extremely low pigment leakage after 5 days of immersion (the absorbance was only 0.081, which can be regarded as no leakage), while the unmodified anthocyanin in Comparative Example 5 was more prone to leakage due to its excessive hydrophilicity; and the gel with a water-oil ratio of 9:1 in Comparative Example 4 also showed a higher pigment migration condition, indicating that a certain oil phase ratio is required to maintain the structure of the gel in order to achieve the binding of the pigment and reduce the migration of the pigment.

Claims

1. A method for preparing a smart label with both high sensitivity and low mobility, characterized in that: The steps include: Acylated anthocyanin and oil phase gelling agent are dissolved in vegetable oil as the oil phase, and a thermoreversible gel aqueous solution is used as the water phase. The water phase and the oil phase are mixed evenly in a volume ratio of 7:3-4:1, rapidly cooled to form a gel, and allowed to stand to obtain a smart label with both high sensitivity and low mobility; Wherein, the preparation method of acylated anthocyanin is as follows: Anthocyanin, lipase, organic acid and 4Å molecular sieve are mixed and dispersed in an organic solvent, heated to perform acylation reaction, filtered to remove the organic solvent and unreacted raw materials after the reaction is completed, and dried to obtain acylated anthocyanin; the lipase is one or more of lipase acrylic resin (recombinant) and lipase derived from Candida; the organic acid is ferulic acid or caffeic acid; The thermoreversible gel is one or more of curdlan, gelatin, and agar; The oil phase gel is one or two of beeswax and glycerol monooleate; the usage ratio of acylated anthocyanin, oil phase gel and vegetable oil is 0.6 g: 3-5 g: 40-60 mL.

2. The method according to claim 1, characterized in that The water phase and oil phase preparation require stirring at 70-90°C for 20-40 min.

3. The method according to claim 1, characterized in that In the preparation method of acylated anthocyanins, the anthocyanins are one or more of blueberry anthocyanins, roselle anthocyanins, grape anthocyanins, mulberry anthocyanins, black bean anthocyanins and purple sweet potato anthocyanins.

4. The method according to claim 1, characterized in that The amount ratio of the thermoreversible gel to water in the thermoreversible gel aqueous solution is 2-4 g:120 mL.

5. The method according to claim 1, characterized in that High-speed shearing is 10000-14000 rpm for 2-5 min.

6. The method according to claim 1, characterized in that In the preparation method of acylated anthocyanin, the organic solvent is one or more of n-butanol, isopropanol, tetrahydrofuran, acetonitrile, tert-amyl alcohol, pyrimidine and acetone.

7. The method according to claim 1, characterized in that In the preparation method of acylated anthocyanin, the dosage ratio of anthocyanin, lipase, organic acid, 4Å molecular sieve and organic solvent is 0.1 g: 0.2-0.4 g: 1.2-1.4 g: 2-4 g: 30-60 mL.

8. The method according to claim 1, characterized in that In the preparation method of acylated anthocyanins, the acylation reaction is carried out by heating at 40-60°C for 20-30 hours.

9. The method according to claim 1, characterized in that: The vegetable oil is one or more of soybean oil, peanut oil, rapeseed oil and sesame oil.

10. The method according to claim 1, characterized in that Standing means standing at 4°C for more than 10 h.

11. A smart label with high sensitivity and low mobility prepared by the method according to any one of claims 1 to 10.

12. Use of the smart label with high sensitivity and low mobility as claimed in claim 11 in packaging materials, wearable materials or degradable materials.

13. Application of the smart label with high sensitivity and low mobility as claimed in claim 11 in the field of food, medicine or agricultural products.

14. A method for detecting the freshness of meat products, characterized in that: The method adopts the smart label with high sensitivity and low mobility as described in claim 11.

15. A method for improving the sensitivity of anthocyanin smart labels and reducing the low mobility of anthocyanins, characterized in that: The steps include: Acylated anthocyanin and oil phase gelling agent are dissolved in vegetable oil as the oil phase, and a thermoreversible gel aqueous solution is used as the water phase. The water phase and the oil phase are mixed evenly in a volume ratio of 7:3-4:1, rapidly cooled to form a gel, and allowed to stand to obtain a smart label with both high sensitivity and low mobility; The anthocyanin, lipase, organic acid and 4Å molecular sieve are mixed and dispersed in an organic solvent, heated for acylation reaction, filtered, the organic solvent and unreacted raw materials are removed, and dried to obtain acylated anthocyanin; the lipase is one or more of lipase acrylic resin (recombinant) and lipase derived from Candida; the organic acid is ferulic acid or caffeic acid; The thermoreversible gel is one or more of curdlan, gelatin, and agar; The oil phase gel is one or two of beeswax and glycerol monooleate; the usage ratio of acylated anthocyanin, oil phase gel and vegetable oil is 0.6 g: 3-5 g: 40-60 mL.

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