OIL-SOLUBLE BEETROOT RED PIGMENT AND PREPARATION METHOD AND APPLICATION THEREOF

Abstract

The present invention belongs to the field of natural pigment modification and specifically relates to an oil-soluble beetroot red pigment, its preparation method and application. An aqueous solution containing beetroot red pigment and phospholipids is added to an aqueous solution containing water-soluble proteins and/or water-soluble peptides, and the mixture is dried to obtain an oil-soluble beetroot red pigment composite powder. The powder is subjected to low-temperature ultra-fine grinding to produce ultra-fine oil-soluble beetroot red pigment powder. Finally, the ultra-fine powder is added to vegetable oil and processed through a ball mill-colloid mill cycle to obtain the oil-soluble beetroot red pigment. The oil-soluble beetroot red pigment requires no chemical modification and contains no synthetic emulsifiers or additives. The materials used are natural and safe, improving the light stability and thermal stability of beetroot red pigment, expanding its application scope, and providing a viable alternative to industrially synthesized oil-soluble pigments.

Claims

1. A method for preparing an oil-soluble beetroot red pigment, comprising the following steps: (1) adding an aqueous solution containing a beetroot red pigment and a phospholipid to an aqueous solution containing a water-soluble protein and/or water-soluble peptide to obtain a beetroot red pigment-phospholipid-protein/peptide mixture; (2) drying the beetroot red pigment-phospholipid-protein/peptide mixture obtained in step (1) to obtain an oil-soluble beetroot red pigment composite powder; (3) subjecting the oil-soluble beetroot red pigment composite powder obtained in step (2) to low-temperature ultra-fine grinding to obtain an oil-soluble beetroot red pigment ultra-fine powder; and (4) adding the oil-soluble beetroot red pigment ultra-fine powder obtained in step (3) to vegetable oil, and grind to disperse, thereby obtaining the oil-soluble beetroot red pigment.

2. The method for preparing the oil-soluble beetroot red pigment according to claim 1, wherein in step (1), a mass ratio of the beetroot red pigment to the phospholipid is 1:(0.05-30.0), a mass fraction of the aqueous solution containing the water-soluble protein and/or water-soluble peptide is 5-45%, and a mass ratio of the water-soluble proteins and water-soluble peptides to the beetroot red is (0.01-13.0):1 in the beetroot red pigment-phospholipid-protein/peptide mixture.

3. The method for preparing the oil-soluble beetroot red pigment according to claim 1, wherein in step (1), the phospholipid is lecithin, modified soybean phospholipid, or enzymatically hydrolyzed soybean phospholipid; the water-soluble protein is a collagen, a soy protein isolate, or a sodium caseinate; and the peptide is a soybean oligopeptide.

4. The method for preparing the oil-soluble beetroot red pigment according to claim 1, wherein in step (3), the low temperature is set at 0-10 C.

5. The method for preparing the oil-soluble beetroot red pigment according to claim 1, wherein in step (3), a particle size of the oil-soluble beetroot red ultra-fine powder ranges from 100 to 300 mesh.

6. The method for preparing the oil-soluble beetroot red pigment according to claim 1, wherein in step (4), a mass fraction of the beetroot red ultra-fine powder in the vegetable oil ranges from 10% to 50%.

7. The method for preparing the oil-soluble beetroot red pigment according to claim 1, wherein in step (4), the grinding and dispersion is performed using a ball mill-colloid mill cycle treatment.

8. The method for preparing the oil-soluble beetroot red pigment according to claim 1, wherein in step (4), a grinding and dispersion treatment is conducted until a D90 of the beetroot red pigment is less than 0.5 m.

Description

DESCRIPTION OF THE DRAWINGS

[0049] FIG. 1 is a diagram showing the appearance of an emulsion made from the oil-soluble beetroot red pigment obtained in Examples 1 to 7 after 12 months of storage under natural light at 25 C.

[0050] FIG. 2 is a diagram showing the appearance of chocolate made from the oil-soluble beetroot red pigments obtained in Examples 1 to 7.

[0051] FIG. 3 is a diagram showing the appearance of the emulsions made from the oil-soluble beet red pigments numbered as control samples 1 to 8 in Comparative Example 1 after 12 months of storage under natural light at 25 C.

[0052] FIG. 4 is a diagram showing the appearance of chocolates made from oil-soluble betaine pigments numbered as control samples 1 to 8 in Comparative Example 1.

[0053] FIG. 5 is a diagram showing the appearance of the emulsion made from the oil-soluble beetroot red pigment numbered as control samples 9 to 16 in Comparative Example 2 after 12 months of storage under natural light at 25 C.

[0054] FIG. 6 is a diagram showing the appearance of chocolate made from the oil-soluble beetroot red pigments numbered as control samples 9 to 16 in Comparative Example 2.

[0055] FIG. 7 is a diagram showing the appearance of the emulsion made from oil-soluble beetroot red pigments numbered as control samples 17 to 24 in Comparative Example 3 after 12 months of storage under natural light at 25 C.

[0056] FIG. 8 is a diagram showing the appearance of chocolate made from the oil-soluble beetroot red pigments numbered as control samples 17 to 24 in Comparative Example 3.

[0057] FIG. 9 is a diagram showing the appearance of the emulsion and chocolate made from the oil-soluble beetroot red pigments in Comparative Examples 4 and 5 after 12 months of storage under natural light at 25 C.

DETAILED DESCRIPTION OF EMBODIMENTS

[0058] The present invention is further described in detail below in conjunction with embodiments and drawings, but the embodiments of the present invention are not limited thereto.

[0059] Unless otherwise specified, the experimental methods used are standard techniques, and the materials used (modified soybean phospholipid, enzymatically hydrolyzed soybean phospholipid, sodium caseinate, soy protein isolate, soy oligopeptides, etc.) are commercially available.

[0060] (1) Beetroot red pigment described in the embodiment is: using beetroot as raw material, and preparing it through crushing-water extraction-filtration-refining-drying according to a conventional method;

[0061] (2) The chocolate application test method described in the embodiment is as follows: 0.1 g of oil-soluble beetroot red pigment is added to 10 g of fully liquefied white chocolate, then stirred evenly and poured into a mold for cooling and shaping. The mold has no restrictions on shape and can be used for easy observation. Under natural light, the optimal result is when the chocolate exhibits a uniform color appearance with no pigment bleeding. Otherwise, it indicates that the beetroot red pigment did not achieve an oil-dispersed state.

[0062] (3) The method for detecting color intensity described in the embodiment is as follows: weigh 0.1 g of sample (accurate to 0.0002 g), extract the beetroot red pigment from the oil using 10 ml of acetate-sodium acetate buffer solution (pH 5.4). Repeat the procedure 3-4 times, combine the buffer solutions, and dilute to a final volume of 100 ml. Using the buffer solution as the reference, measure the absorbance of the test solution at 535 nm with a spectrophotometer in a 1 cm cuvette. This absorbance value represents the color intensity.

[00001]$E\frac{1\%}{1\mathrm{cm}}=\frac{A}{c1}$

[0063] Wherein: Aabsorbance at 535 nm; cconcentration of beetroot red solution

[0064] (4) The deposition rate described in the embodiment refers to the precipitation and accumulation of beetroot red pigment under centrifugal action. The deposition rate reflects the stability of beetroot red in oil. The higher the deposition rate, the more unstable the oil-soluble beetroot red. A deposition rate of less than 10% indicates prolonged stability of the beetroot red pigment in oil, meeting shelf-life requirements. The detection method is: take 5.0 g of oil-soluble beetroot red pigment, centrifuge at 25 C. and 6000 rpm for 10 minutes, pour out the supernatant to obtain xg of the oil layer. The deposition rate () is calculated using the following formula:

[00002]$=\left(5-x\right)/5100\%$

Example 1

[0065] (1) Add 100 g of beetroot red pigment (color value 150) and 50 g of modified soybean phospholipid to 3500 ml of water, stirring until completely dissolved to obtain an aqueous solution containing beetroot red pigment and phospholipid. Dissolve 350 g of sodium caseinate in 4650 ml of water to obtain a 7% (w/w) sodium caseinate solution.

[0066] (2) Slowly add the aqueous solution containing beetroot red pigment and phospholipid prepared in step (1) into the sodium caseinate aqueous solution at a rate of 10 ml/s. Shear the mixture using a high-speed homogenizer at a linear velocity of 20 m/s for 10 minutes to obtain a beetroot red-phospholipid-sodium caseinate mixture.

[0067] (3) Homogenize the beetroot red-phospholipid-sodium caseinate mixture obtained in step (2) at 45 Mpa, then pressure spray drying it into a dry powder to obtain a beetroot red pigment composite powder.

[0068] (4) The beetroot red pigment composite powder obtained in step (3) is ultra-finely ground at 12,000 rpm in a dry environment at 0 to 10 C. and passed through a 200-mesh sieve to obtain beetroot red pigment ultra-fine powder.

[0069] (5) Add 200 g of the beetroot red pigment ultra-fine powder obtained in step (4) to 1800 ml of olive oil and subject to a ball mill-colloid mill grinding cycle for 120 minutes to obtain an oil-soluble beetroot red pigment with a particle size of D90=0.788 m, a color intensity of 3.0, and a deposition rate of 12.3%. In chocolate applications, the color is uniform with no visible beetroot red pigment particles.

Example 2

[0070] (1) Add 100 g of beetroot red pigment (color value 150) and 150 g of modified soybean phospholipid into 2600 ml water, stirring until completely dissolved to obtain an aqueous solution containing beetroot red pigment and phospholipid. Dissolve 500 g of soy protein isolate in 4500 ml of water to obtain a 10% (w/w) soy protein isolate aqueous solution.

[0071] (2) Slowly add the aqueous solution containing beetroot red pigment and phospholipid prepared in step (1) into the soy protein isolate aqueous solution at a rate of 10 ml/s. Shear the mixture using a high-speed homogenizer at a linear velocity of 20 m/s for 20 minutes to obtain a beetroot red-phospholipid-soy protein isolate mixture.

[0072] (3) Homogenize the beetroot red-phospholipid-soy protein isolate mixture obtained in step (2) at 45 Mpa, then pressure spray drying it into a dry powder to obtain a beetroot red pigment composite powder.

[0073] (4) The beetroot red pigment composite powder obtained in step (3) is ultra-finely ground at 12,000 rpm in a dry environment at 0 to 10 C. and passed through a 260-mesh sieve to obtain beetroot red pigment ultra-fine powder.

[0074] (5) Add 200 g of the beetroot red pigment ultra-fine powder obtained in step (4) to 1800 ml of olive oil and subject to a ball mill-colloid mill grinding cycle for 120 minutes to obtain an oil-soluble beetroot red pigment with a particle size of D90=0.609 m, a color intensity of 2.0, and a deposition rate of 8.5%. In chocolate applications, the color is uniform with no visible beetroot red pigment particles.

Example 3

[0075] (1) Add 500 g of beetroot red pigment (color value 150) and 250 g of enzymatically hydrolyzed soybean phospholipid into 3500 ml water, stirring until completely dissolved to obtain an aqueous solution containing beetroot red pigment and phospholipid. Dissolve 600 g of sodium caseinate in 3400 ml of water to obtain a 15% (w/w) sodium caseinate aqueous solution.

[0076] (2) Slowly add the aqueous solution containing beetroot red pigment and phospholipid prepared in step (1) into the sodium caseinate aqueous solution at a rate of 10 ml/s. Shear the mixture using a high-speed homogenizer at a linear velocity of 20 m/s for 10 minutes to obtain a beetroot red-phospholipid-sodium caseinate mixture.

[0077] (3) Homogenize the beetroot red-phospholipid-sodium caseinate mixture obtained in step (2) at 45 Mpa, then pressure spray drying it into a dry powder to obtain a beetroot red pigment composite powder.

[0078] (4) The beetroot red pigment composite powder obtained in step (3) is ultra-finely ground at 12,000 rpm in a dry environment at 0 to 10 C. and passed through a 300-mesh sieve to obtain beetroot red pigment ultra-fine powder.

[0079] (5) Add 400 g of the beetroot red pigment ultra-fine powder obtained in step (4) to 1600 ml of corn oil and subject to a ball mill-colloid mill grinding cycle for 240 minutes until the beetroot red pigment particle size reaches D90<0.5 m, resulting in an oil-soluble beetroot red pigment with D90=0.430 m, a color intensity of 11.1, and a deposition rate of 6.9%. In chocolate applications, the color is uniform with no visible beetroot red pigment particles.

Example 4

[0080] (1) Add 500 g of beetroot red pigment (color value 150) and 700 g of enzymatically hydrolyzed soybean phospholipid into 6300 ml water, stirring until completely dissolved to obtain an aqueous solution containing beetroot red pigment and phospholipid. Dissolve 300 g of soy protein isolate in 2700 ml of water to obtain a 10% (w/w) soy protein isolate aqueous solution.

[0081] (2) Slowly add the aqueous solution containing beetroot red pigment and phospholipid prepared in step (1) into the soy protein isolate aqueous solution at a rate of 10 ml/s. Shear the mixture using a high-speed homogenizer at a linear velocity of 20 m/s for 10 minutes to obtain a beetroot red-phospholipid-soy protein isolate mixture.

[0082] (3) Homogenize the beetroot red-phospholipid-soy protein isolate mixture obtained in step (2) at 45 Mpa, then pressure spray drying it into a dry powder to obtain a beetroot red pigment composite powder.

[0083] (4) The beetroot red pigment composite powder obtained in step (3) is ultra-finely ground at 12,000 rpm in a dry environment at 0 to 10 C. and passed through a 260-mesh sieve to obtain beetroot red pigment ultra-fine powder.

[0084] (5) Add 400 g of the beetroot red pigment ultra-fine powder obtained in step (4) to 1600 ml of corn oil and subject to a ball mill-colloid mill grinding cycle for 240 minutes until the beetroot red pigment particle size reaches D90<0.5 m, resulting in an oil-soluble beetroot red pigment with D90=0.481 m, a color intensity of 10.0, and a deposition rate of 4.7%. In chocolate applications, the color is uniform with no visible beetroot red pigment particles.

Example 5

[0085] (1) Add 800 g of beetroot red pigment (color value 150), 370 g of modified soybean phospholipid, and 220 g of enzymatically hydrolyzed soybean phospholipid into 6600 ml water, stirring until completely dissolved to obtain an aqueous solution containing beetroot red pigment and phospholipid. Dissolve 500 g of soy protein isolate in 2000 ml of water to obtain a 20% (w/w) soy protein isolate aqueous solution.

[0086] (2) Slowly add the aqueous solution containing beetroot red pigment and phospholipid prepared in step (1) into the soy protein isolate aqueous solution at a rate of 10 ml/s. Shear the mixture using a high-speed homogenizer at a linear velocity of 20 m/s for 20 minutes to obtain a beetroot red-phospholipid-soy protein isolate mixture.

[0087] (3) Homogenize the beetroot red-phospholipid-soy protein isolate mixture obtained in step (2) at 45 Mpa, then pressure spray drying it into a dry powder to obtain a beetroot red pigment composite powder.

[0088] (4) The beetroot red pigment composite powder obtained in step (3) is ultra-finely ground at 12,000 rpm in a dry environment at 0 to 10 C. and passed through a 220-mesh sieve to obtain beetroot red pigment ultra-fine powder.

[0089] (5) Add 600 g of the beetroot red pigment ultra-fine powder obtained in step (4) to 1400 ml of sunflower oil and subject to a ball mill-colloid mill grinding cycle for 320 minutes until the beetroot red pigment particle size reaches D90<0.5 m, resulting in an oil-soluble beetroot red pigment with D90=0.218 m, a color intensity of 19.0, and a deposition rate of 1.87%. In chocolate applications, the color is uniform with no visible beetroot red pigment particles.

Example 6

[0090] (1) Add 800 g of beetroot red pigment (color value 80), 300 g of modified soybean phospholipid, and 520 g of enzymatically hydrolyzed soybean phospholipid into 7600 ml water, stirring until completely dissolved to obtain an aqueous solution containing beetroot red pigment and phospholipid. Dissolve 600 g of soy protein isolate and 150 g of sodium caseinate in 3000 ml of water to obtain a 20% (w/w) mixed protein aqueous solution.

[0091] (2) Slowly add the aqueous solution containing beetroot red pigment and phospholipid prepared in step (1) into the mixed protein aqueous solution at a rate of 10 ml/s. Shear the mixture using a high-speed homogenizer at a linear velocity of 20 m/s for 20 minutes to obtain a beetroot red-phospholipid-mixed protein mixture.

[0092] (3) Homogenize the beetroot red-phospholipid-mixed protein mixture obtained in step (2) at 45 Mpa, then pressure spray drying it into a dry powder to obtain a beetroot red pigment composite powder.

[0093] (4) The beetroot red pigment composite powder obtained in step (3) is ultra-finely ground at 12,000 rpm in a dry environment at 0 to 10 C. and passed through a 300-mesh sieve to obtain beetroot red pigment ultra-fine powder.

[0094] (5) Add 600 g of the beetroot red pigment ultra-fine powder obtained in step (4) to 1400 ml of sunflower oil and subject to a ball mill-colloid mill grinding cycle for 320 minutes until the beetroot red pigment particle size reaches D90<0.5 m, resulting in an oil-soluble beetroot red pigment with D90=0.198 m, a color intensity of 8.1, and a deposition rate of 0.94%. In chocolate applications, the color is uniform with no visible beetroot red pigment particles.

Example 7

[0095] (1) Add 500 g of beetroot red pigment (color value 80), 150 g of modified soybean phospholipid, and 350 g of enzymatically hydrolyzed soybean phospholipid into 8000 ml water, stirring until completely dissolved to obtain an aqueous solution containing beetroot red pigment and phospholipid. Dissolve 300 g of soy oligopeptides and 150 g of sodium caseinate in 2197 ml of water to obtain a 17% (w/w) mixed protein aqueous solution.

[0096] (2) Slowly add the aqueous solution containing beetroot red pigment and phospholipid prepared in step (1) into the mixed protein aqueous solution at a rate of 10 ml/s. Shear the mixture using a high-speed homogenizer at a linear velocity of 20 m/s for 20 minutes to obtain a beetroot red-phospholipid-mixed protein mixture.

[0097] (3) Homogenize the beetroot red-phospholipid-mixed protein mixture obtained in step (2) at 45 Mpa, then pressure spray drying it into a dry powder to obtain a beetroot red pigment composite powder.

[0098] (4) The beetroot red pigment composite powder obtained in step (3) is ultra-finely ground at 12,000 rpm in a dry environment at 0 to 10 C. and passed through a 240-mesh sieve to obtain beetroot red pigment ultra-fine powder.

[0099] (5) Add 450 g of the beetroot red pigment ultra-fine powder obtained in step (4) to 1550 ml of sunflower oil and subject to a ball mill-colloid mill grinding cycle for 300 minutes until the beetroot red pigment particle size reaches D90<0.5 m, resulting in an oil-soluble beetroot red pigment with D90=0.375 m, a color intensity of 6.1, and a deposition rate of 2.94%. In chocolate applications, the color is uniform with no visible beetroot red pigment particles.

Comparative Example 1

[0100] This embodiment serves as a comparative example, intended to evaluate the effects of directly mixing ordinary beet red powder (containing dextrin) with emulsifiers and oils on the quality of the resulting oil-soluble beetroot red pigment. The specific method is as follows:

[0101] Replace the ultra-fine powder of beetroot red pigment in step (5) of Example 1 with ordinary beetroot red powder (containing dextrin) of equivalent color value and quality, and add it together with the emulsifiers from Table 1 into olive oil, maintaining the same emulsifier ratio as the phospholipids in Example 1. Each group of experiments is conducted under the same conditions as in step (5) of Example 1 to prepare the oil-soluble beetroot red pigment. The resulting oil-soluble beetroot red pigment is analyzed for chocolate appearance and emulsion stability after being stored for 12 months.

TABLE-US-00001 TABLE 1 Types of emulsifiers, proportions, and final product appearances of each control sample in Comparative Example 1 Emul- Choco- Control sifier Depo- late After 12 Sample Propor- sition Appear- Months of Number Emulsifier Name tion (%) Rate(%) ance Storage 1 Polyglycerol 1.0 79.4 Uneven Precipitation Esters (HLB 2.5-4.5) 2 Sucrose Fatty 1.0 91.2 Uneven Precipitation Acid Esters (HLB 2.0-3.0) 3 Citric Acid Fatty 1.0 77.0 Uneven Precipitation Acid Glycerides 4 Polyglycerol 1.0 79.9 Uneven Precipitation Ricinoleate 5 Enzymatically 1.0 85.3 Uneven Precipitation Hydrolyzed Soybean Phospholipids 6 Modified Soybean 1.0 81.7 Uneven Precipitation Phospholipids 7 Diacetyl Tartaric 1.0 70.4 Uneven Precipitation Acid Mono- and Diglycerides 8 Mono- and 1.0 93.2 Uneven Precipitation Diglycerides of Fatty Acids (HLB 3.0)

Comparative Example 2

[0102] This embodiment serves as a comparative example, intended to evaluate the effects of directly mixing ordinary beet red powder (containing dextrin) with emulsifiers and oils on the quality of the resulting oil-soluble beetroot red pigment. The specific method is as follows:

[0103] Replace the ultra-fine powder of beetroot red pigment in step (5) of Example 4 with ordinary beetroot red powder (containing dextrin) of equivalent color value and quality, and add it together with the emulsifiers from Table 2 into olive oil, maintaining the same emulsifier ratio as the phospholipids in Example 4. Each group of experiments is conducted under the same conditions as in step (5) of Example 4 to prepare the oil-soluble beetroot red pigment. The resulting oil-soluble beetroot red pigment is analyzed for chocolate appearance and emulsion appearance after being stored for 12 months.

TABLE-US-00002 TABLE 2 Types of emulsifiers, proportions, and final product appearances of each control sample in Comparative Example 2 Control Emulsifier Depo- Chocolate After 12 Sample Emulsifier Proportion sition Appear- Months of Number Name (%) Rate(%) ance Storage 9 Polyglycerol 9.3 65.6 Uneven Precipitation Esters (HLB 2.5-4.5) 10 Sucrose Fatty 9.3 77.9 Uneven Precipitation Acid Esters (HLB 2.0-3.0) 11 Citric Acid 9.3 69.1 Uneven Precipitation Fatty Acid Glycerides 12 Polyglycerol 9.3 42.6 Uneven Precipitation Ricinoleate 13 Enzymatically 9.3 73.4 Uneven Precipitation Hydrolyzed Soybean Phospholipids 14 Modified 9.3 77.0 Uneven Precipitation Soybean Phospholipids 15 Diacetyl Tartaric Acid 9.3 23.7 Uneven Precipitation Mono-and Diglycerides 16 Mono-and 9.3 81.2 Uneven Precipitation Diglycerides of Fatty Acids (HLB 3.0)

Comparative Example 3

[0104] This embodiment serves as a comparative example, intended to evaluate the effects of directly mixing ordinary beet red powder (containing dextrin) with emulsifiers and oils on the quality of the resulting oil-soluble beetroot red pigment. The specific method is as follows:

[0105] Replace the ultra-fine powder of beetroot red pigment in step (5) of Example 6 with ordinary beetroot red powder (containing dextrin) of equivalent color value and quality, and add it together with the emulsifiers from Table 3 into olive oil, maintaining the same emulsifier ratio as the phospholipids in Example 6. Each group of experiments is conducted under the same conditions as in step (5) of Example 6 to prepare the oil-soluble beetroot red pigment. The resulting oil-soluble beetroot red pigment is analyzed for chocolate appearance and emulsion appearance after being stored for 12 months.

TABLE-US-00003 TABLE 3 Types of emulsifiers, proportions, and final product appearances of each control sample in Comparative Example 3 Control Emulsifier Depo- Chocolate After 12 Sample Emulsifier Proportion sition Appear- Months of Number Name (%) Rate(%) ance Storage 17 Polyglycerol 11.0 59.7 Uneven Precipitation Esters (HLB 2.5-4.5) 18 Sucrose Fatty 11.0 92.9 Uneven Precipitation Acid Esters (HLB 2.0-3.0) 19 Citric Acid 11.0 75.5 Uneven Precipitation Fatty Acid Glycerides 20 Polyglycerol 11.0 37.7 Uneven Precipitation Ricinoleate 21 Enzymatically 11.0 65.2 Uneven Precipitation Hydrolyzed Soybean Phospholipids 22 Modified 11.0 49.6 Uneven Precipitation Soybean Phospholipids 23 Diacetyl 11.0 12.4 Uneven Precipitation Tartaric Acid Mono-and Diglycerides 24 Mono-and 11.0 80.1 Uneven Precipitation Diglycerides of Fatty Acids (HLB 3.0)

Comparative Example 4

Comparative Example 4: Excessive Phospholipid Ratio

[0106] (1) Add 50 g of beetroot red pigment (color value of 150) and 1800 g of enzymatically hydrolyzed soybean phospholipid to 13.950 L of water, and stir until fully dissolved to obtain an aqueous solution containing beetroot red pigment and phospholipids. Dissolve 350 g of sodium caseinate in 4650 ml of water to prepare a 7% (w/w) sodium caseinate solution.

[0107] (2) Slowly add the aqueous solution containing beetroot red pigment and phospholipids prepared in step (1) to the mixed protein solution at a rate of 10 ml/s. Then, use a high-speed shear mixer to shear at a linear speed of 20 m/s for 10 minutes to obtain a beetroot red-phospholipid-protein mixture.

[0108] (3) Homogenize the beetroot red-phospholipid-protein mixture prepared in step (2) at 45 MPa, then perform pressure spray drying to obtain a dry powder, resulting in a beetroot red pigment composite powder. Due to the high phospholipid ratio, this composite powder exhibits high viscosity and poor flowability, causing severe adhesion during drying, with a thick layer of beetroot red powder adhering to the inner walls of the equipment.

[0109] (4) Subject the beetroot red pigment composite powder prepared in step (3) to ultra-fine grinding at 12,000 rpm in a drying environment of 0-10 C. Due to the high viscosity of the powder, it adheres to the pin bars of the grinder, making sieving difficult. Lowering the temperature to-10 C. to 0 C. does not improve the grinding effect.

[0110] (5) Add 200 g of the ultra-fine beetroot red pigment powder prepared in step (4) to 1800 ml of olive oil, and process it using a ball mill-grinding and colloid mill-crushing cycle for 120 minutes to obtain oil-soluble beetroot red pigment with a particle size of D90=15.388 m. Due to the presence of numerous insoluble particles during testing, its coloring strength could not be measured. In chocolate applications, the pigment could not mix with chocolate for coloring purposes. During the cycle process, the ball mill and colloid mill experienced multiple blockages, with irregular paste-like lumps being cleared as blockage material. Analysis indicated that the cause was the high viscosity of the beetroot red powder, leading to adhesion and aggregation under mechanical forces.

Comparative Example 5

[0111] (1) Add 800 g of beetroot red pigment (color value 150), 370 g of modified soybean phospholipid, and 220 g of enzymatically hydrolyzed soybean phospholipid to 6600 ml of water, and stir until completely dissolved to obtain an aqueous solution containing beetroot red pigment and phospholipids. Dissolve 500 g of soy protein isolate in 2000 ml of water to obtain a 20% (w/w) soy protein isolate solution.

[0112] (2) Slowly add the soy protein isolate solution prepared in step (1) to the aqueous solution containing beetroot red pigment and phospholipids at a rate of 10 ml/s. As the protein solution is added, solid particles gradually appear on the surface and increase in quantity. Use a high-speed shear mixer to shear at a linear speed of 20 m/s for 20 minutes, then filter through a 100-mesh screen to obtain a beetroot red-phospholipid-protein mixture. A large amount of pigment-containing insoluble material is observed on the filter screen, indicating that the protein likely denatured upon encountering the highly polar beetroot red-phospholipid solution.

[0113] (3) Homogenize the beetroot red-phospholipid-protein mixture obtained by filtration in step (2) at 45 MPa, then perform pressure spray drying to obtain a dry powder, resulting in beetroot red pigment composite powder.

[0114] (4) Grind the beetroot red pigment composite powder obtained in step (3) at an elevated temperature of 12,000 rpm in a drying environment of 0-10 C., and pass it through a 220-mesh screen to obtain ultra-fine beetroot red pigment powder.

[0115] (5) Add 600 g of the ultra-fine beetroot red pigment powder prepared in step (4) to 1400 ml of sunflower oil, and process it using a ball mill-colloid mill cycle for 320 minutes to obtain oil-soluble beetroot red pigment with a particle size of D90=1.884 m, a coloring strength of 9.2, and a deposition rate of 23.94%. In chocolate applications, the color is uneven, and beetroot red pigment particles are present.

[0116] The results of Comparative Examples 1-3 indicate that increasing the amount of emulsifier can enhance the stability of oil-soluble beetroot red pigment, but the improvement is very limited. The primary reason is that beetroot red pigment molecules lack lipophilicity. Although emulsifiers contain hydrophilic groups, there is no water in the oil-soluble environment. The hydrophilic groups of the emulsifier and beetroot red molecules are maintained only by intermolecular forces, which are far from sufficient to overcome the gravitational forces of the beetroot red molecules themselves. This results in easy aggregation and deposition during the shelf life, adversely affecting the product's usability.

[0117] As shown in FIGS. 3-8, the stability of the oil-soluble beetroot red pigment emulsion in Comparative Examples 1-3 is positively correlated with the amount of emulsifier used. However, beetroot red pigment itself lacks the ability to bind with the emulsifier and can only rely on the viscosity of the emulsifier to maintain a limited suspended dispersion. Compared to the preparation method provided by this invention, the stability differs significantly. In the 12-month storage test of Examples 1-7, no changes were observed in the emulsion state, and the appearance in chocolate applications remained normal (FIGS. 1-2). In Comparative Example 1, all pigments in Control Samples 1-8 precipitated after 12 months of storage, resulting in a light and uneven color appearance in chocolate applications (FIGS. 3-4). In Comparative Example 2, all pigments in Control Samples 9-16 precipitated after 12 months, with a reduced extent of deposition, though the color in chocolate applications remained uneven (FIGS. 5-6). In Comparative Example 3, all pigments in Control Samples 17-24 precipitated after 12 months, with further reduced deposition, but the color in chocolate applications was still uneven (FIGS. 7-8). Among these, Control Sample 23 exhibited less deposition, but the diacetyl tartaric acid mono- and diglycerides imparted a strong acetic acid odor, significantly affecting the flavor.

[0118] Additionally, it can be observed from Examples 1-7 that a longer processing time in the ball mill grinding-colloid mill crushing cycle results in a smaller particle size of the oil-soluble beetroot red pigment, a lower deposition rate, and increased stability.

[0119] The above examples represent preferred embodiments of the present invention; however, the implementation of the invention is not limited to these examples. Any modifications, alterations, substitutions, combinations, or simplifications that do not deviate from the spirit and principles of the present invention are considered equivalent substitutions and are included within the protection scope of this invention.