High-stability anthocyanin co-pigment as well as preparation method and application thereof

Abstract

The invention discloses an anthocyanin-quercetin copigment with high thermal stability as well as a preparation method and application of the anthocyanin-quercetin copigment and application of the anthocyanin-quercetin copigment in 3D printing and the like. The method comprises the following steps: 1, preparing a buffer solution, namely preparing a citric acid solution; preparing a disodium hydrogen phosphate solution; and the pH is calibrated to 3.00 + / -0.1 through proper mixing. 2, a preparation method of mother liquor of anthocyanin and quercetin: dissolving the anthocyanin with absolute ethyl alcohol, and adding a buffer solution after the anthocyanin is completely dissolved, so that the concentration of the anthocyanin is 0.1-10g / L; the quercetin is dissolved with absolute ethyl alcohol, a buffer solution is added after the quercetin is completely dissolved, and the concentration of the quercetin is 0.1-10 g / L; 3, preparing a co-pigment solution, namely mixing and uniformly shaking the prepared anthocyanin mother liquor and quercetin mother liquor according to the mass ratio of (1-3): (5-15); the purple ink has excellent thermal stability, can be widely applied to intelligent packaging indication labels, endows food with natural purple tone, and is especially used as an ink material for 3D printing.

Description

Technical Field

[0001] This invention relates to the field of pigments, and particularly to a highly stable anthocyanin-quercetin co-pigment, its preparation method, and its application in 3D printing, etc. Background Technology

[0002] Anthocyanins are a class of natural, water-soluble pigments widely found in plants, giving fruits and vegetables their vibrant colors. Due to their various physiological activities, including antioxidant, anti-inflammatory, and anti-cancer properties, they have broad application prospects in the food, health product, cosmetic, and pharmaceutical industries. Furthermore, the unique molecular structure of anthocyanins makes their color highly sensitive to environmental pH, a characteristic that demonstrates great potential in smart packaging applications such as intelligent labels for food freshness.

[0003] However, anthocyanins face severe challenges in practical applications. The phenolic hydroxyl groups in their molecular structure are easily affected by factors such as light, heat, pH, and oxygen, leading to molecular degradation, fading, and inactivation, resulting in poor stability and severely limiting their functional performance and practical applications. Especially in scenarios requiring exposure to light or high-temperature processing (such as food sterilization and baking) or long-term storage, the insufficient stability of anthocyanins has become a major bottleneck restricting their widespread application.

[0004] Existing methods for improving anthocyanin stability mainly include chemical structure modification, copigmentation, and the construction of delivery systems (such as microcapsules, nanoparticles, and carrier loading). Among these, copigmentation is a physical method that utilizes certain copigments to bind to anthocyanin molecules through intermolecular forces (such as π-π stacking, hydrophobic interactions, and hydrogen bonds), thereby stabilizing the chromophore structure and delaying degradation. This method has advantages such as relatively simple operation, no need for complex chemical reactions, and high safety.

[0005] Quercetin is a common flavonol natural compound widely found in various plants and possesses good biological activity. Studies have shown that quercetin, as a co-pigment, can significantly enhance the thermal and photostability of anthocyanins within a certain range when forming a co-pigment system. However, existing research on anthocyanin-quercetin co-pigments mainly focuses on exploring the co-pigmentation mechanism, lacking systematic research on preparation methods, especially in-depth exploration and optimization of the optimal ratio of co-pigments to anthocyanins, stabilization mechanisms, and practical application performance. Furthermore, existing preparation methods do not adequately consider the long-term stability of the co-pigment solution and its compatibility with solid-state supports.

[0006] Prior art WO2021262567A1 discloses a formulation based on anthocyanins and quercetin to improve respiratory health, the formulation comprising anthocyanins and quercetin. This formulation can be implemented in several different ways. For example, the formulation includes a sugar phase and an anthocyanin / quercetin phase comprising anthocyanins and quercetin. The sugar phase and the anthocyanin / quercetin phase are based on an emulsification process (es). The sugar phase is configured to promote the binding of anthocyanins and quercetin, including promoting the distribution of anthocyanins and quercetin in the formulation. However, based on the formulation administered to subjects, this formulation is configured to increase lung elasticity, reduce inflammation in the lungs, minimize fluid accumulation in the lungs, and promote the clearance of mucus from the lungs of subjects, reducing pneumonia, thereby improving lung respiratory function, and / or stopping or reducing viral replication. No stability studies of anthocyanins are involved.

[0007] Therefore, developing a method for preparing anthocyanin-quercetin co-pigments with a well-defined process, optimized formulation, significantly improved thermal and light stability of anthocyanins, and applicable to subsequent solid-state functional materials (such as smart indicator tags) has important theoretical and practical value. Summary of the Invention

[0008] This invention addresses the problems of poor anthocyanin stability, unclear ratios in existing co-pigment systems, and the difficulty in directly applying liquid systems to solid indicator materials in the prior art. It provides an anthocyanin-quercetin co-pigment with high thermal stability and its preparation method.

[0009] The steps include: 1. Preparation method of buffer solution Prepare a citric acid solution; prepare a disodium hydrogen phosphate solution; mix appropriately to calibrate the pH to 3.00 ± 0.1.

[0010] 2. Preparation method of anthocyanin and quercetin stock solution Anthocyanins are dissolved in anhydrous ethanol, and after complete dissolution, a buffer solution is added. The anthocyanin concentration is 0.1-10 g / L, preferably 0.5-5 g / L, for example 0.8 or 1 g / L.

[0011] Quercetin is dissolved in anhydrous ethanol, and after complete dissolution, a buffer solution is added. The concentration of quercetin is 0.1-10 g / L, preferably 0.5-5 g / L, for example 0.8 or 1 g / L.

[0012] 3. Preparation of co-pigment solution Mix the prepared anthocyanin stock solution and quercetin stock solution at a mass ratio of (1-3):(5-20) and shake well.

[0013] Furthermore, the mixing temperature is 20-30 degrees Celsius, such as room temperature of 25 degrees Celsius.

[0014] Furthermore, the pH of the buffer solution was calibrated to 3.00 ± 0.05.

[0015] Furthermore, the citric acid solution was prepared using citric acid monohydrate.

[0016] Furthermore, the disodium hydrogen phosphate solution was prepared using disodium hydrogen phosphate dodecahydrate.

[0017] Furthermore, anthocyanins are derived from blueberry extract.

[0018] Furthermore, in the preparation of quercetin stock solution, due to the low solubility of quercetin, thorough stirring or ultrasonic-assisted dissolution is required during preparation.

[0019] Further, the prepared anthocyanin stock solution and quercetin stock solution are mixed and shaken at a mass ratio of 1:(4-10). For example, 1:(8-10).

[0020] This application also provides an anthocyanin-quercetin co-pigment with high thermal stability, prepared by the above method.

[0021] This application also provides the application of a highly thermally stable anthocyanin-quercetin co-pigment in smart packaging indicator labels.

[0022] Furthermore, by utilizing the stability of co-pigments and the property that anthocyanins change with pH, ​​they can be used to detect the freshness of food inside packaging.

[0023] This application also provides the application of a highly thermally stable anthocyanin-quercetin co-pigment in functional foods.

[0024] Furthermore, it enhances the nutritional value of food and gives it a natural purple hue.

[0025] This application also provides the application of a highly thermally stable anthocyanin-quercetin co-pigment in 3D ink materials.

[0026] Beneficial Effects: The anthocyanin-quercetin co-pigment prepared in this application exhibits excellent thermal stability. Quercetin (containing a benzene ring and polyphenolic hydroxyl groups) and anthocyanin (flavonoid ions) form a complex through π-π stacking and hydrogen bonding, encapsulating the anthocyanin chromophore and reducing thermally induced molecular vibrations. Furthermore, quercetin also inhibits the heat-induced conversion of anthocyanin to colorless methanol pseudobase, blocking irreversible degradation pathways and maintaining structural stability. Therefore, the co-pigment prepared in this application can be widely used in smart packaging indicator labels: utilizing the stability of the co-pigment and the pH-dependent properties of anthocyanins, it can be used to detect the freshness of food within the packaging. Development of Functional Foods: For example, it can be added to food, and especially, due to its high thermal stability, it can be used as an ink material for 3D printing, imparting a natural purple hue. Attached Figure Description

[0027] Figure 1 This is a graph showing the anthocyanin-quercetin co-pigment solutions with varying concentrations before heating, after being stirred evenly. The mass ratios (anthocyanin:quercetin) from left to right are 1:0.5, 1:0, 1:1, 1:2, 1:4, 1:6, 1:8, and 1:10.

[0028] Figure 2 This is a diagram of quercetin stock solution.

[0029] Figure 3 This is a diagram of anthocyanin mother liquor.

[0030] Figure 4 The image shows a portion of the solution after heating, where the color has noticeably lightened.

[0031] Figure 5 The graph shows the degradation rate of the co-pigment after heating at 70°C.

[0032] Figure 6 The graph shows the degradation rate of the co-pigment after heating at 75°C.

[0033] Figure 7 The graph shows the degradation rate of the co-pigment after heating at 80°C.

[0034] Figure 8 The graph shows the degradation rate of the co-pigment after heating at 85°C.

[0035] Figure 9 The graph shows the degradation rate of the co-pigment after heating at 90°C. Detailed Implementation

[0036] To facilitate understanding by those skilled in the art, the present invention will be further described below with reference to embodiments. The content mentioned in the embodiments is not intended to limit the present invention. Example 1

[0037] 1. Preparation method of buffer solution Weigh 21.014 g of citric acid monohydrate (C6H8O7·H2O), add ultrapure water to a final volume of 1000 mL to obtain a 0.1 mol / L citric acid solution, denoted as solution A. Weigh 35.628 g of disodium hydrogen phosphate dodecahydrate (Na2HPO4·12H2O), add ultrapure water to a final volume of 500 mL to obtain a 0.2 mol / L disodium hydrogen phosphate solution, denoted as solution B. Mix 46.5 mL of solution A with 3.5 mL of solution B, and calibrate the pH to 3.00 ± 0.05 using a pH meter. If the pH deviates from the target value, correct by fine-tuning the ratio of solution A / B. Finally, transfer the mixture to a 100 mL volumetric flask and dilute to volume. Store at 4°C protected from light; shelf life is 7 days.

[0038] 2. Preparation method of anthocyanin and quercetin stock solution Accurately weigh 0.600g of blueberry anthocyanins, dissolve them in 50mL of anhydrous ethanol in a beaker, and then add McIlvaine buffer solution to bring the volume to 500mL after complete dissolution.

[0039] The preparation method for quercetin stock solution is the same as above, but because quercetin has low solubility, it needs to be thoroughly stirred or dissolved with ultrasonic assistance during preparation.

[0040] 3. Preparation of co-pigment solution Simply mix the prepared anthocyanin stock solution and quercetin stock solution at a mass ratio of 1:8 and shake well. Example 2

[0041] The steps are basically the same as in Example 1, except that the prepared anthocyanin stock solution and quercetin stock solution are mixed and shaken at a mass ratio of 1:4. Example 3

[0042] The steps are basically the same as in Example 1, except that the prepared anthocyanin stock solution and quercetin stock solution are mixed and shaken at a mass ratio of 1:6.

[0043] Test case A pure anthocyanin solution was set up as the control group, and anthocyanin-quercetin co-pigment solutions with mass ratios of 1:0.5, 1:1, 1:2, 1:4, 1:6, 1:8, 1:10, 1:20, and 1:30 were set up as experimental groups. Each solution was divided into three parallel groups, and 10 mL of each solution was taken from each group and heated in a constant temperature water bath. Before heating, 1 mL of sample solution was accurately pipetted from each group to determine the anthocyanin content (TAC) as the initial value. After heating for 2 h, the samples were cooled to room temperature in an ice-water bath, and the final anthocyanin content (TAC) was measured again to determine the optimal ratio for thermal stability.

[0044] The temperature of the constant temperature water bath was set to 70℃, 75℃, 80℃, 85℃ and 90℃. The TAC was measured before and after heating in six experiments according to the above steps, and the degradation rate was calculated.

[0045] At all experimental temperatures, the anthocyanin degradation rate of the pure anthocyanin solution was the highest among the temperature groups, indicating that the addition of quercetin can effectively reduce the thermal degradation of anthocyanins and improve their thermal stability through the co-pigmentation effect. As the mass ratio of anthocyanins to quercetin gradually decreased (i.e., the relative content of quercetin increased), the degradation rate at each temperature generally showed a downward trend; when the mass ratio dropped to around 1:10, the degradation rate reached a relatively low level. Taking the highest experimental temperature of 90℃ as an example, the degradation rate of pure anthocyanins was approximately 0.3198, while at a mass ratio of 1:10, the degradation rate was only 0.1665, a decrease of approximately 47.9% compared to pure anthocyanins; at the lowest experimental temperature of 70℃, the degradation rate of pure anthocyanins was 0.0888, and at a mass ratio of 1:10, the degradation rate dropped to 0.0249, a decrease of over 71%. This trend indicates that anthocyanins and quercetin can form a complex structure through intermolecular interactions such as π-π stacking and hydrogen bonding, which reduces the degradation of anthocyanin molecules under thermal conditions, and this protective effect is enhanced with the increase of the relative content of quercetin.

[0046] When the mass ratio of anthocyanins to quercetin was further reduced to 1:20 or 1:30, the degradation rate at lower temperatures (70℃, 75℃, 80℃, etc.) showed a slight rebound, but remained significantly lower than that of the pure anthocyanin group at the same temperature. This may be because excess quercetin (which has oxidizing properties) competes with anthocyanins for the antioxidant environment in the system; it also alters the molecular interaction mode of the original co-pigment system (for example, excess quercetin molecules bind to each other, reducing the amount of stable complexes that can form with anthocyanins), ultimately causing some anthocyanins to lose protection, resulting in a slight rebound in the degradation rate. Furthermore, the increase in inhibitory effect was not significant with excess quercetin, leading to low cost-effectiveness.

[0047] The results from various temperature groups indicate that the anthocyanin-quercetin co-pigment system exhibits low anthocyanin thermal degradation rate and enhanced thermal stability, demonstrating the strong thermal stability of this co-pigment product.

[0048] It will be understood by those skilled in the art that, unless otherwise defined, all terms used herein (including technical and scientific terms) have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. It should also be understood that terms such as those defined in general dictionaries should be understood to have the same meaning as in the context of the prior art, and should not be interpreted in an idealized or overly formal sense unless specifically defined as herein.

[0049] It should be understood that the above detailed description of the technical solutions of the present invention with reference to preferred embodiments is illustrative and not restrictive. Those skilled in the art can modify the technical solutions described in the embodiments or make equivalent substitutions for some of the technical features based on reading this specification; for example, different concentrations of mother liquor can be prepared and mixed in proportions different from those claimed in this application, but the proportion of anthocyanins and quercetin co-pigment solutions is substantially the same as that in the co-pigment solution of this application. These modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing anthocyanin-quercetin co-pigment with high thermal stability, characterized in that, The steps include: S1. Preparation method of buffer solution Prepare citric acid solution; prepare disodium hydrogen phosphate solution; mix appropriately to calibrate pH to 3.00±0.1; S2. Preparation method of anthocyanin and quercetin stock solution Anthocyanins are dissolved in anhydrous ethanol, and after complete dissolution, a buffer solution is added to achieve an anthocyanin concentration of 0.1-10 g / L. Quercetin was dissolved in anhydrous ethanol, and after complete dissolution, a buffer solution was added to achieve a quercetin concentration of 0.1-10 g / L. S3. Preparation of co-pigment solution Mix the prepared anthocyanin stock solution and quercetin stock solution at a mass ratio of (1-3):(5-20) and shake well.

2. The method according to claim 1, characterized in that, The pH of the buffer solution was calibrated to 3.00 ± 0.

05.

3. The method according to claim 1, characterized in that, Citric acid solution is prepared using citric acid monohydrate; and / or disodium hydrogen phosphate solution is prepared using disodium hydrogen phosphate dodecahydrate.

4. The method according to claim 1, characterized in that, In the preparation of quercetin stock solution, thorough stirring or ultrasonic-assisted dissolution is required.

5. An anthocyanin-quercetin co-pigment with high thermal stability, prepared by the method of any one of claims 1-4.

6. The application of a highly thermally stable anthocyanin-quercetin co-pigment in smart packaging indicator labels, wherein the anthocyanin-quercetin co-pigment is prepared by any one of claims 1-4.

7. The application according to claim 6, characterized in that, The stability of co-pigments and the property that anthocyanins change with pH can be used to detect the freshness of packaged food.

8. Application of a heat-stable anthocyanin-quercetin co-pigment in functional foods.

9. Application of a highly thermally stable anthocyanin-quercetin co-pigment in 3D ink materials.

Images