Preparation method and application of aluminum-free cochineal red pigment microemulsification

Abstract

The present invention discloses a method for preparing aluminum-free carmine pigment microemulsion, comprising the following steps: S1: mixing a whey protein isolate solution with an aluminum-free carmine pigment solution, adding a copigment solution, adjusting the pH to 3-6, obtaining a premixed pigment solution, and mixing the premixed pigment solution with a cosurfactant, glycerol, in a 1:1 ratio to form a new aqueous phase; S2: mixing oil and a mixed emulsifier to obtain an oil phase; and S3: dropwise adding the aqueous phase formed in S1 to the oil phase obtained in S2 to obtain the aluminum-free carmine pigment in a microemulsion. The present invention utilizes the synergistic effect of protein and polyphenol copigments with the aluminum-free carmine pigment, as well as the encapsulation effect of the microemulsion, to enhance the stability of the aluminum-free carmine pigment. The method is simple to operate, non-toxic, and harmless, effectively inhibiting the degradation and fading of the aluminum-free carmine pigment caused by light exposure, and has good application prospects in the processing of oily liquids and solid foods.

Description

Technical Field

[0001] The invention belongs to the technical field of natural pigments, and particularly relates to a preparation method and application of aluminum-free cochineal red pigment microemulsification. Background Art

[0002] Aluminum-free cochineal red pigment is a natural anthraquinone pigment derived from cochineal. Due to its bright color and stable physical and chemical properties, it has been used in food, cosmetics, and pharmaceuticals. However, the color of aluminum-free cochineal red pigment is very sensitive to pH and metal ions. It will show different colors under different pH conditions. It is also easy to form complexes with metal ions. 3+ , Fe 2+ , Ca 2+ and Sn 2+ When there are such substances, precipitation is likely to form, which in turn leads to pigment loss.

[0003] Food systems are complex, with varying pH values ​​and containing a variety of substances, including metal ions, proteins, starches, oils, oxidants, and reducing agents. Any substance in food that interacts with aluminum-free carmine pigments can affect their color. Generally speaking, aluminum-free carmine pigments are relatively stable in acidic foods, but their color is easily affected in neutral and alkaline foods. When used to dye animal livers, which are high in iron and calcium, and dairy products with high calcium content, the color of aluminum-free carmine pigments can also be affected by the presence of metal ions and pH in the food. These issues limit their widespread use in food. Currently, aluminum lakes, which are relatively stable, are commonly used commercially for dyeing. However, the presence of aluminum in aluminum lake molecules raises questions about their safety in food. Therefore, new methods are needed to stabilize the color of aluminum-free carmine pigments and ensure their safe application in food processing.

[0004] Current methods for improving pigment stability primarily include interactions with macromolecules, addition of small molecule co-pigmentants, metal ion chelation, pigment molecule modification, and encapsulation. Microemulsions generally refer to colorless, transparent (or translucent), low-viscosity, thermodynamically stable systems composed of surfactants, co-surfactants, oil, and water in appropriate proportions. In food, microemulsions have been used to improve nutrient digestibility, inhibit bacteria, and encapsulate active substances and pigments to increase their stability or solubility. Using water-in-oil microemulsions, water-soluble pigment molecules can be encapsulated, thereby avoiding color changes caused by complex food environments. Furthermore, oil-in-water microemulsions facilitate the application of water-soluble pigments in various oil-containing food systems, expanding their application in the food industry. Summary of the Invention

[0005] One of the purposes of the present invention is to provide a method for preparing an aluminum-free cochineal pigment microemulsion. The present invention overcomes the problem of unstable coloration of existing aluminum-free cochineal pigments and provides a method for improving pigment stability by combining protein-small molecule co-pigment agents and microemulsion encapsulation.

[0006] The second purpose of the present invention is to use the prepared aluminum-free cochineal red pigment emulsion in the fields of food, cosmetics and medicine.

[0007] In order to achieve the above purpose, the following technical solutions are adopted:

[0008] In a first aspect, a method for preparing an aluminum-free cochineal red pigment microemulsion comprises the following steps:

[0009] S1: mixing a whey protein isolate solution with an aluminum-free cochineal red pigment solution, adding a co-pigment solution, adjusting the pH value to 3-6 to obtain a premixed pigment solution, and mixing the premixed pigment solution with a cosurfactant to form a new aqueous phase;

[0010] S2: mixing the oil and the mixed emulsifier to prepare the oil phase;

[0011] S3: The aqueous phase formed in S1 is added dropwise to the oil phase prepared in S2 to obtain an aluminum-free cochineal red pigment microemulsion.

[0012] Furthermore, the preparation method of the S1 whey protein isolate solution is: dissolving whey protein isolate powder in a pH 7.4 buffer solution to prepare the whey protein isolate solution.

[0013] Furthermore, the whey protein isolate solution has a concentration of 5-10 mg / mL, the solvent for the whey protein isolate solution is a phosphate buffer solution with a pH of 6-8, the concentration of the aluminum-free carmine pigment solution is 0.6%-6%, the solvent for the aluminum-free carmine pigment solution is a citric acid buffer solution with a pH of 6, and the mass concentration ratio of the whey protein isolate solution to the aluminum-free carmine pigment solution is 1:1-20:1. Furthermore, the S1 cosurfactant is glycerol, and the ratio of the cosurfactant to the pigment solution is 4:6-7:3.

[0014] Furthermore, the S1 auxiliary pigment solution is a polyphenolic substance, and the auxiliary pigment solution is preferably one of ferulic acid solution, catechin solution, gallic acid solution, quercetin solution, naringenin solution or resveratrol solution, and the mass concentration of the auxiliary pigment solution is 5-20 mg / mL.

[0015] Furthermore, the S2 oil is sunflower oil or corn oil, the mixed emulsifier is Span 80 and Tween 80, the ratio of the sunflower oil or corn oil to the mixed emulsifier is 4:6~9:1, and the ratio of Span 80 to Tween 80 is 5:5~9:1.

[0016] Furthermore, the operation steps of S3 are as follows: the aqueous phase mixture formed in S1 is added dropwise to the oil phase formed in S2 at a rotation speed of 800 r / min and stirred evenly.

[0017] Another object of the present invention is to use the prepared aluminum-free cochineal red pigment emulsion in the fields of food, cosmetics, and medicine.

[0018] The technical solution of the present invention has the following advantages:

[0019] This study addresses the vulnerability of aluminum-free carmine pigment to environmental factors such as pH and metal ions. By interacting with the pigment through a protein-polyphenol complex system, the pigment solution was encapsulated into a water-in-oil (W / O) pigment microemulsion to enhance its stability. Whey protein isolate was used as a macromolecular copigment, while ferulic acid, catechin, gallic acid, quercetin, naringenin, and resveratrol were used as small-molecule polyphenol copigments. After protection treatment, the pigment retention of the aluminum-free carmine pigment increased from 32.23% to 35.56%–51.28% after irradiation (15,000 lx, 28°C, 2 weeks). The pigment's color in oily food systems closely resembles that of commercial carmine aluminum lakes. The method has simple and convenient operation steps, does not use any non-edible chemical additives, significantly improves the color stability of the aluminum-free cochineal red pigment, and is suitable for meeting the demand for aluminum-free cochineal red pigment in oil-containing food systems. DETAILED DESCRIPTION

[0020] The technical solutions of the present invention will be described clearly and completely below with reference to the embodiments. Obviously, the embodiments described are only a portion of the embodiments of the present invention, not all of them. All other embodiments derived by persons of ordinary skill in the art without creative effort based on the embodiments of the present invention are intended to fall within the scope of protection of the present invention.

[0021] The color of aluminum-free cochineal red pigment is very sensitive to pH value and metal ions. It will show different colors under different pH conditions. It is easy to form complexes with metal ions. 3+ , Fe 2+ , Ca 2+ and Sn 2+ When there are such substances, precipitation is likely to form, which in turn leads to pigment loss.

[0022] In view of this, the present invention provides a method for preparing an aluminum-free carmine pigment microemulsion. The method has simple and convenient operation steps, does not use any non-edible chemical additives, significantly improves the color stability of the aluminum-free carmine pigment, and is suitable for meeting the demand for aluminum-free carmine pigment in oil-containing food systems.

[0023] According to a first aspect of the present invention, a method for preparing aluminum-free carmine pigment microemulsification provided by the present invention comprises the following steps:

[0024] S1: mixing a whey protein isolate solution with an aluminum-free cochineal red pigment solution, adding a co-pigment solution, adjusting the pH value to 3-6 to obtain a premixed pigment solution, and mixing the premixed pigment solution with a cosurfactant to form a new aqueous phase;

[0025] S2: mixing the oil and the mixed emulsifier to prepare the oil phase;

[0026] S3: The aqueous phase formed in S1 is added dropwise to the oil phase prepared in S2 to obtain an aluminum-free cochineal red pigment microemulsion.

[0027] In a preferred embodiment, the preparation method of the S1 whey protein isolate solution is: dissolving whey protein isolate powder in a pH 7.4 buffer solution to prepare the whey protein isolate solution.

[0028] In a preferred embodiment, the concentration of the whey protein isolate solution is 5-10 mg / mL, the solvent of the whey protein isolate solution is a phosphate buffer with a pH value of 6-8, the concentration of the aluminum-free cochineal pigment solution is 0.6%-6%, the solvent of the aluminum-free cochineal pigment solution is a citric acid buffer with a pH value of 6, and the mass concentration ratio of the whey protein isolate solution to the aluminum-free cochineal pigment solution is 1:1-20:1. Its typical but non-limiting concentration of whey protein isolate solution is 5 mg / mL, 6 mg / mL, 7 mg / mL, 8 mg / mL, 9 mg / mL or 10 mg / mL, etc., its typical but non-limiting pH value of phosphate buffer is 6, 7 or 8, etc., and its typical but non-limiting mass concentration ratio of whey protein isolate solution to aluminum-free cochineal red pigment solution is 1:1, 2:1, 3:1, 4:1, 5:1, 6:1, 7:1, 8:1, 9:1, 10:1, 11:1, 12:1, 13:1, 14:1, 15:1, 16:1, 17:1, 18:1, 19:1 or 20:1, etc.

[0029] In a preferred embodiment, the S1 cosurfactant is glycerol, and the ratio of the cosurfactant to the pigment solution is 4:6 to 7:3.

[0030] In a preferred embodiment, the S1 auxiliary pigment solution is a polyphenolic substance, and the auxiliary pigment solution is preferably one of ferulic acid solution, catechin solution, gallic acid solution, quercetin solution, naringenin solution or resveratrol solution, and the mass concentration of the auxiliary pigment solution is 5 to 20 mg / mL. Its typical but non-limiting auxiliary pigment solution is one of ferulic acid solution, catechin solution, gallic acid solution, quercetin solution, naringenin solution or resveratrol solution, and its typical but non-limiting auxiliary pigment solution mass concentration is 5 mg / mL, 6 mg / mL, 7 mg / mL, 8 mg / mL, 9 mg / mL, 10 mg / mL, 11 mg / mL, 12 mg / mL, 13 mg / mL, 14 mg / mL, 15 mg / mL, 16 mg / mL, 17 mg / mL, 18 mg / mL, 19 mg / mL or 20 mg / mL, etc.

[0031] In a preferred embodiment, the S2 oil is sunflower oil or corn oil, the mixed emulsifier is Span 80 and Tween 80, the ratio of the sunflower oil or corn oil to the mixed emulsifier is 4:6~9:1, and the ratio of Span 80 to Tween 80 is 5:5~9:1.

[0032] In a preferred embodiment, the operation steps of S3 are as follows: the aqueous phase mixture formed in S1 is added dropwise to the oil phase formed in S2 at a rotation speed of 800 r / min and stirred evenly.

[0033] The second aspect of the present invention is the application of the prepared aluminum-free cochineal red pigment emulsion in the fields of food, cosmetics, and medicine.

[0034] This invention provides a method for preparing aluminum-free carmine pigment by microemulsion. This method addresses the issue of aluminum-free carmine pigment being susceptible to environmental factors such as pH and metal ions. By interacting with the pigment through a protein-polyphenol complex system, the pigment solution is encapsulated into a water-in-oil (W / O) pigment microemulsion to improve the pigment's stability. Whey protein isolate is used as a macromolecular co-pigment, while ferulic acid, catechin, gallic acid, quercetin, naringenin, and resveratrol are used as small-molecule polyphenol co-pigment agents. These are encapsulated within the microemulsion system. After protection treatment, the pigment retention rate of the aluminum-free carmine pigment after irradiation (15,000 lx, 28°C, 2 weeks) increases from 32.23% to 35.56%–51.28%. The pigment's color in oily food systems is closer to that of commercial carmine aluminum lakes. The method has simple and convenient operation steps, does not use any non-edible chemical additives, significantly improves the color stability of the aluminum-free cochineal red pigment, and is suitable for meeting the demand for aluminum-free cochineal red pigment in oil-containing food systems.

[0035] The present invention is further described below by way of examples. Unless otherwise specified, the materials in the examples were prepared according to existing methods or directly purchased from the market.

[0036] Example 1:

[0037] A 0.02% (w / w) aluminum-free cochineal pigment solution was prepared. The solution was stirred at 300 r / min for 2 h and the pH was adjusted to 6 to obtain a final concentration of 0.02% aluminum-free cochineal pigment in the pigment solution.

[0038] Example 2:

[0039] Whey protein isolate powder was used as the raw material and dissolved in a pH 7.4 buffer solution to prepare a 5.3 mg / mL whey protein isolate solution. The solution was stirred at 300 r / min for 2 h to fully dissolve the solution. A 0.6% (w / w) aluminum-free carmine pigment solution was prepared. Equal volumes of the whey protein isolate solution and pigment solution were mixed and stirred at 300 r / min for 1 h. An equal volume of 10.0 mg / mL ferulic acid solution was added and stirred at 300 r / min for 1 h. The pH was adjusted to 6 to prepare the pigment solution, which was then mixed with an equal volume of glycerol to form a new aqueous phase. A 10 g oil phase was prepared by mixing sunflower oil and a mixed emulsifier (Tween 80 to Span 80, 5:5, by mass) in a 5:5 ratio. The new aqueous phase was added dropwise to the oil phase while stirring at 800 r / min. The final concentration of aluminum-free carmine pigment in the resulting microemulsion was 0.02%. Example 3:

[0040] Whey protein isolate powder was used as the raw material and dissolved in a pH 7.4 buffer solution to prepare a 5.3 mg / mL whey protein isolate solution. The solution was stirred at 300 r / min for 2 h to fully dissolve the whey protein isolate solution. A 0.6% (w / w) pigment solution was prepared with aluminum-free carmine. Equal volumes of the whey protein isolate solution and pigment solution were mixed and stirred at 300 r / min for 1 h. An equal volume of 10.0 mg / mL catechin solution was added and stirred at 300 r / min for 1 h. The pH was adjusted to 6 to prepare the pigment solution, which was then mixed with an equal volume of glycerol to form a new aqueous phase. A 10 g oil phase was prepared by mixing sunflower oil and a mixed emulsifier (Tween 80 to Span 80, 5:5 by mass) in a 5:5 ratio. The new aqueous phase was added dropwise to the oil phase while stirring at 800 r / min. The final concentration of aluminum-free carmine pigment in the resulting microemulsion was 0.02%.

[0041] Example 4:

[0042] Whey protein isolate powder was used as the raw material and dissolved in a pH 7.4 buffer solution to prepare a 5.3 mg / mL whey protein isolate solution. The solution was stirred at 300 r / min for 2 h to fully dissolve the whey protein isolate solution. A 0.6% (w / w) pigment solution was prepared with aluminum-free carmine. Equal volumes of the whey protein isolate solution and pigment solution were mixed and stirred at 300 r / min for 1 h. An equal volume of 10.0 mg / mL gallic acid solution was added and stirred at 300 r / min for 1 h. The pH was adjusted to 6 to prepare the pigment solution, which was then mixed with an equal volume of glycerol to form a new aqueous phase. A 10 g oil phase was prepared by mixing sunflower oil and a mixed emulsifier (Tween 80 to Span 80, 5:5 by mass) in a 5:5 ratio. The new aqueous phase was added dropwise to the oil phase while stirring at 800 r / min. The final concentration of aluminum-free carmine pigment in the resulting microemulsion was 0.02%. Example 5:

[0043] Whey protein isolate powder was used as the raw material and dissolved in a pH 7.4 buffer solution to prepare a 5.3 mg / mL whey protein isolate solution. The solution was stirred at 300 r / min for 2 h to fully dissolve the whey protein isolate solution. A 0.6% (w / w) pigment solution was prepared with aluminum-free carmine. Equal volumes of the whey protein isolate solution and pigment solution were mixed and stirred at 300 r / min for 1 h. An equal volume of 10.0 mg / mL quercetin solution was added and stirred at 300 r / min for 1 h. The pH was adjusted to 6 to prepare the pigment solution, which was then mixed with an equal volume of glycerol to form a new aqueous phase. A 10 g oil phase was prepared by mixing sunflower oil and a mixed emulsifier (Tween 80 to Span 80, 5:5 by mass) in a 5:5 ratio. The new aqueous phase was added dropwise to the oil phase while stirring at 800 r / min. The final concentration of aluminum-free carmine pigment in the resulting microemulsion was 0.02%.

[0044] Example 6:

[0045] Whey protein isolate powder was used as the raw material and dissolved in a pH 7.4 buffer solution to prepare a 5.3 mg / mL whey protein isolate solution. The solution was stirred at 300 r / min for 2 h to fully dissolve the solution. A 0.6% (w / w) aluminum-free carmine pigment solution was prepared. Equal volumes of the whey protein isolate solution and pigment solution were mixed and stirred at 300 r / min for 1 h. An equal volume of 10.0 mg / mL naringenin solution was added and stirred at 300 r / min for 1 h. The pH was adjusted to 6 to prepare the pigment solution, which was then mixed with an equal volume of glycerol to form a new aqueous phase. A 10 g oil phase was prepared by mixing sunflower oil and a mixed emulsifier (Tween 80 to Span 80, 5:5 by mass) in a 5:5 ratio. The new aqueous phase was added dropwise to the oil phase while stirring at 800 r / min. The final concentration of aluminum-free carmine pigment in the resulting microemulsion was 0.02%.

[0046] Example 7:

[0047] Whey protein isolate powder was used as the raw material and dissolved in a pH 7.4 buffer solution to prepare a 5.3 mg / mL whey protein isolate solution. The solution was stirred at 300 r / min for 2 h to fully dissolve the whey protein isolate solution. A 0.6% (w / w) pigment solution was prepared with aluminum-free carmine. Equal volumes of the whey protein isolate solution and pigment solution were mixed and stirred at 300 r / min for 1 h. An equal volume of 10.0 mg / mL resveratrol solution was added and stirred at 300 r / min for 1 h. The pH was adjusted to 6 to prepare the pigment solution, which was then mixed with an equal volume of glycerol to form a new aqueous phase. A 10 g oil phase was prepared by mixing sunflower oil and a mixed emulsifier (Tween 80 to Span 80, 5:5 by mass) in a 5:5 ratio. The new aqueous phase was added dropwise to the oil phase while stirring at 800 r / min. The final concentration of aluminum-free carmine pigment in the resulting microemulsion was 0.02%.

[0048] Determination of light stability in the present invention:

[0049] (1) Preparation of the standard curve: Aqueous solutions and microemulsions of aluminum-free carmine pigment at mass fractions of 0.01%, 0.02%, 0.03%, 0.04%, and 0.05% (w / w) were prepared using sodium dihydrogen phosphate-citric acid buffer solution (0.05 mol / L, pH = 3). The absorbance was measured at 490 nm, and the standard curves of the aqueous solutions and microemulsions of aluminum-free carmine pigment were prepared based on the results.

[0050] (2) Five groups of 0.02% (w / w) aluminum-free carmine pigment aqueous solutions and microemulsions were pipetted, with two replicates per group, each 5 mL. One group was stored in the dark, and the remaining four groups were placed in a constant temperature light incubator with a light intensity of 15,000 lx and a set temperature of 28°C. One group of samples was taken out at 2 weeks and 4 weeks, respectively, and stored in the dark. The retention rate of aluminum-free carmine pigment was calculated based on the respective standard curves. The retention rates of the pigment in the aqueous solution and microemulsion were compared to determine the light stability of the aluminum-free carmine pigment microemulsion.

[0051]

[0052] in: The concentration of aluminum-free cochineal red pigment in the aqueous solution or microemulsion measured by taking samples for the corresponding weeks; is the concentration of aluminum-free cochineal red pigment in the pigment aqueous solution or microemulsion at week 0.

[0053] Table 1 Results of aluminum-free cochineal red pigment retention rate

[0054]

[0055] As shown in Table 1, in comparative experiments conducted under identical conditions, pigment retention in aluminum-free cochineal pigment aqueous solutions decreased to 32.23% and 24.56% after two and four weeks of illumination, respectively. In microemulsion systems prepared by mixing with protein and polyphenols, all six polyphenols exhibited excellent stabilization, maintaining the same protein, polyphenol, and pigment mass ratios and microemulsion system conditions. Among the six phenolic compounds, the microemulsion system containing resveratrol exhibited the highest pigment retention, reaching 51.28% and 43.45% after two and four weeks, respectively.

[0056] Example 8:

[0057] A 0.02% aluminum-free cochineal carmine aqueous solution and a 0.02% aluminum-free cochineal carmine microemulsion described in Example 7 were prepared and added to the fish paste and chicken paste, respectively, at a mass ratio of 2:1, and stirred evenly. Commercial cochineal carmine aluminum lake was added to the above two ingredients in the same proportion and stirred evenly.

[0058] Table 2 Dyeing results of two classic oily food systems

[0059]

[0060] As shown in Table 2, the microemulsion system prepared in the present invention effectively stabilizes the color of aluminum-free cochineal red pigment. Compared to the coloring of aluminum-free cochineal red aqueous solution, the microemulsion prepared in the present invention imparts a color to minced fish and minced chicken that is close to that of commercial cochineal red aluminum lake, meeting the coloring requirements of aluminum-free cochineal red pigment in oil-containing food systems.

[0061] This invention provides a method for improving the color stability of aluminum-free carmine pigment by combining protein interactions, small molecule co-pigmentation, and microemulsion encapsulation. Whey protein isolate is used as a biomacromolecule protective agent, while ferulic acid, catechin, gallic acid, quercetin, naringenin, or resveratrol are added as co-pigments. A water-in-oil (W / O) microemulsion is prepared via a self-emulsification method. After the protective treatment, the pigment retention rate of aluminum-free carmine pigment after irradiation (15,000 lx, 28°C, 2 weeks) increases from 32.23% to 35.56%–51.28%. The coloration in oil-containing food systems is closer to that of commercial carmine aluminum lakes. The treatment method disclosed herein utilizes the interaction between biomacromolecules and aluminum-free cochineal pigments to prepare a microemulsion to improve pigment stability. The method is simple and convenient to operate, is non-toxic and harmless, effectively inhibits the fading of aluminum-free cochineal red pigment caused by light, and has a coloring effect in oil-containing food systems that is closer to that of commercial cochineal red aluminum lake. The method has good application prospects in food system dyeing.

[0062] Obviously, the above embodiments are merely examples for clarity of explanation and are not intended to limit the implementation methods. Those skilled in the art will appreciate that other variations or modifications can be made based on the above description. It is not necessary and impossible to enumerate all implementation methods here. Obvious variations or modifications arising therefrom remain within the scope of protection of the present invention.

Claims

1. A method for preparing an aluminum-free cochineal red pigment microemulsion, characterized in that: The steps include: S1: mixing a whey protein isolate solution with an aluminum-free cochineal red pigment solution, adding an auxiliary pigment solution, adjusting the pH value to 3-6 to obtain a premixed pigment solution, and mixing the premixed pigment solution with a cosurfactant in proportion to form a new aqueous phase; S2: mixing the oil and the mixed emulsifier to prepare the oil phase; S3: adding the aqueous phase formed in S1 dropwise to the oil phase prepared in S2 to obtain an aluminum-free cochineal pigment microemulsion; The S1 cosurfactant is glycerol, the S1 auxiliary pigment solution is a polyphenol substance, and the mixed emulsifier is a mixture of Tween 80 and Span 80.

2. The method for preparing an aluminum-free cochineal red pigment microemulsion according to claim 1, wherein: The preparation method of the S1 whey protein isolate solution is as follows: dissolving whey protein isolate powder in a pH 7.4 buffer solution to prepare the whey protein isolate solution.

3. The method for preparing an aluminum-free cochineal red pigment microemulsion according to claim 1 or 2, wherein: The whey protein isolate solution S1 has a concentration of 5-10 mg / mL, the solvent of the whey protein isolate solution is a phosphate buffer with a pH value of 6-8, the concentration of the aluminum-free cochineal pigment solution is 0.6%-6%, the solvent of the aluminum-free cochineal pigment solution is a citric acid buffer with a pH value of 6, and the mass concentration ratio of the whey protein isolate solution to the aluminum-free cochineal pigment solution is 1:1-20:

1.

4. The method for preparing an aluminum-free cochineal red pigment microemulsion according to claim 1, wherein: The ratio of the cosurfactant to the pigment solution is 4:6-7:

3.

5. The method for preparing an aluminum-free cochineal pigment microemulsion according to claim 1, wherein: The auxiliary pigment solution is one of ferulic acid solution, catechin solution, gallic acid solution, quercetin solution, naringenin solution or resveratrol solution, and the mass concentration of the auxiliary pigment solution is 5-20 mg / mL.

6. The method for preparing an aluminum-free cochineal red pigment microemulsion according to claim 1, wherein: The S2 oil is sunflower oil or corn oil, the ratio of the sunflower oil or corn oil to the mixed emulsifier is 4:6-9:1, and the ratio of Span 80 to Tween 80 is 1:1-9:

1.

7. The method for preparing an aluminum-free cochineal red pigment microemulsion according to claim 1, wherein: The operation steps of S3 are as follows: the aqueous phase mixture formed in S1 is added dropwise to the oil phase formed in S2 at a rotation speed of 800 r / min and stirred evenly.

8. Use of the aluminum-free cochineal pigment microemulsion prepared according to any one of claims 1 to 7 in the fields of food, cosmetics and medicine.

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