A method for preparing capsicum red food pigment rich in free amino acids

Abstract

The present invention relates to the technical field of preparation of edible pigments, and discloses a method for preparing a capsanthin edible pigment rich in free amino acids, comprising the following steps: (1) processing dry red pepper to obtain red pigment powder; (2) mixing silk fibroin powder and red pigment powder in a mass ratio of 17-25:5-8, adding the obtained mixture to a Tween solution for dissolution, and then adding edible glacial acetic acid at a temperature of -5 to 5°C, reacting for 2-3 hours, and obtaining an edible pigment. In the present invention, silk fibroin is added to capsanthin to obtain an edible pigment, which is rich in free amino acids, can not only give the edible pigment a higher edible value, but also improve the pigment stability, reduce the use of other additives, and reduce costs.

Description

Technical Field

[0001] The invention belongs to the technical field of food coloring preparation, and more specifically relates to a method for preparing a capsicum red food coloring rich in free amino acids. Background Art

[0002] Capsanthin is a pigment found in ripe red pepper fruits. It has strong tinting power and good color retention effect. It is widely used in the coloring of various foods and can effectively extend the shelf life of simulated foods. It is highly safe, has nutritional and health benefits, and has been proven by modern science to have anti-cancer and anti-radiation functions. It has good development prospects.

[0003] However, capsanthin is susceptible to accelerated decomposition by ultraviolet rays, so it generally needs to be stored away from light, which limits its use scenarios, or requires the addition of many additional stabilizers and additives to overcome such problems, which greatly increases the cost, and the addition of various other stabilizers and additives affects the nutritional value of capsanthin. Therefore, it is of great significance to produce a healthy, green, nutritious and affordable food coloring. Summary of the invention

[0004] In view of the shortcomings of the prior art, the present invention provides a method for preparing a capsanthin edible pigment rich in free amino acids. Silk fibroin is added to capsanthin to obtain an edible pigment. The edible pigment is rich in free amino acids, which can not only give the edible pigment a higher edible value, but also improve the pigment stability, reduce the use of other additives, and reduce costs.

[0005] To achieve the above object, the specific technical scheme of the present invention is: a method for preparing a capsicum red food pigment rich in free amino acids, comprising the following steps:

[0006] (1) Processing dried red pepper to obtain red pigment powder;

[0007] (2) Silk fibroin powder and red pigment powder are mixed in a mass ratio of 17-25:5-8, the resulting mixture is added to a Tween solution to dissolve, and then edible glacial acetic acid is added at a temperature of -5 to 5°C and reacted for 2-3 hours to obtain an edible pigment.

[0008] Silk fibroin is composed of nearly 20 different amino acids, of which glycine (Gly), alanine (A1a) and serine (Ser) account for 80%. Serine can slow down skin aging and has a beauty and whitening effect. Glycine can neutralize excess stomach acid and reduce the harm of salicylic acid to the stomach and intestines. Amino acids such as tryptophan and tyrosine can also absorb ultraviolet rays. The properties of these amino acids determine the excellent functions of silk fibroin and its extremely high edible value.

[0009] Silk protein with high free amino acid content plays a huge role in the production of bread and other foods that need to be foamed. It can make the pores of cakes small and uniform, reducing the difficulty of cake making. In addition, amino acids are easy to combine with the holes in the pigment under low temperature conditions to form a relatively stable structure. The specific principle is that under low temperature and acid conditions, the number of holes in the pigment increases, and the positive charge of the amino group in the amino acid is enhanced, making it easier for the two to combine and the combination is more stable. In addition, the use of food-grade acetic acid is harmless to the human body and is green and safe.

[0010] The present invention uses silk fibroin and capsanthin to mix to make edible pigment, adds multiple types of free amino acids to the edible pigment, makes the pigment more stable, reduces the use of other additives, reduces costs, and at the same time improves the nutritional value of the pigment, and also has certain beauty and whitening effects.

[0011] Further preferably, in step (2), the mass concentration of the Tween solution is 0.1-0.2%.

[0012] As a good dispersant and solubilizer, Tween solution can effectively disperse protein powder and pigment powder in the solution, which is beneficial to the effect of acetic acid on the two and increases the binding amount of the two.

[0013] Further preferably, in step (2), the volume ratio of the mixture to the Tween solution is 1:50.

[0014] Further preferably, in step (2), the concentration of the edible glacial acetic acid is 0.04-0.06 mol / ml; and the volume ratio of the edible glacial acetic acid to the Tween solution is 1:2.

[0015] Further preferably, in step (1), the processing of the dried red pepper is as follows: the dried red pepper is crushed and dried to obtain dried pepper fragments; the dried pepper fragments are refluxed in anhydrous ethanol, filtered after the reflux is completed, and the filtrate is subjected to reduced pressure distillation to obtain red pigment powder.

[0016] More preferably, the reflux temperature is 80-90° C. and the reflux time is 2-4 h.

[0017] Further preferably, the temperature of the reduced pressure distillation is 55-65° C. and the pressure is 0.01-0.03 MPa.

[0018] Further preferably, the silk fibroin powder is prepared by cutting silkworm cocoons, washing and drying them to obtain silkworm fragments; 2 CO 3 The silk is boiled in a solution for degumming, and then the cocoons are recovered, washed and dried; the dried cocoons are added into a NaOH solution, heated at 90-95°C for reaction for 3-5 hours to obtain a silk fibroin solution, and then dialyzed and freeze-dried to obtain a silk fibroin powder.

[0019] The present invention uses sodium hydroxide to hydrolyze silk, and the obtained silk fibroin solution is rich in various free amino acids and can be used as a green and healthy food additive. The silk fibroin extraction is simple and convenient, low in cost, high in use value, and has a huge application market in green food and food safety.

[0020] Further preferably, the silkworm fragments and Na 2 CO 3 The bath ratio of the solution is 1:30-80g / ml; the Na 2 CO 3 The concentration of the solution is 0.1-1.2 wt%.

[0021] Further preferably, the bath ratio of the dried cocoon silk and the NaOH solution is 1:30-50 g / ml; the concentration of the NaOH solution is 0.1-0.5 mol / L; the molecular weight cutoff of the dialysis bag is 1000-5000; and the freeze-drying is carried out at a temperature of -60°C to 0°C for 2-3 days.

[0022] Compared with the prior art, the present invention has the following advantages: silk fibroin is added to capsanthin to obtain edible pigment, and the free amino acids rich in silk fibroin can not only give the edible pigment a higher edible value, but also can combine with the cavities of capsanthin to improve the pigment stability, reduce the use of other additives, reduce costs, and be green and safe. DETAILED DESCRIPTION

[0023] The technical content and effects of the present invention are further described in detail below in conjunction with the embodiments, but the present invention is not limited thereto.

[0024] Example 1

[0025] (1) Preparation of silk fibroin powder: Weigh 10.0 g of clean silk cocoons, cut them open and clean the inner and outer surfaces, cut them into 2 mm long and 1 mm wide silkworm pieces, and dry them in an oven at 37°C. 2 CO 3 The solution was boiled for 1 hour for degumming, with a bath ratio of 1:50 g / ml, and the degumming was repeated twice, and the cocoons and silks were recovered, washed, and dried at 37°C. The dried cocoons and silks were added to a 0.35 mol / L NaOH solution with a bath ratio of 1:30 g / ml, and heated at 90°C for 5 hours to obtain a silk fibroin solution, which was cooled to room temperature and loaded into a dialysis bag with a molecular weight cutoff of 1000, and dialyzed with deionized water for 72 hours, with the water changed every 2 hours. After the dialysis, the solution obtained was freeze-dried at -30°C for 72 hours to obtain a silk fibroin powder.

[0026] (2) Preparation of red pigment powder: 10.0 g of dried red pepper was crushed to an average particle size of 0.5 mm, and dried at 65° C. for 5 h to obtain dried pepper fragments. The dried pepper fragments were refluxed in anhydrous ethanol at 85° C. for 3 h, and filtered after reflux. The filtrate was distilled under reduced pressure at 0.01 MPa and 60° C. to obtain red pigment powder.

[0027] (3) Silk fibroin powder and red pigment powder were mixed at a mass ratio of 25:5, and the resulting mixture was dissolved in a 0.1wt% Tween solution at a volume ratio of 1:50; the mixture was then cooled to -5°C, and 0.05mol / ml of edible glacial acetic acid (with a volume ratio of 1:2 to the Tween solution) was added, and the reaction was carried out for 2h to obtain edible pigment.

[0028] Example 2

[0029] (1) Preparation of silk fibroin powder: Weigh 10.0 g of clean silk cocoons, cut them open and clean the inner and outer surfaces, cut them into 3 mm long and 2 mm wide silkworm pieces, and dry them in an oven at 37°C. 2 CO 3 The solution was boiled for 1 hour for degumming, with a bath ratio of 1:40 g / ml, and the degumming was repeated twice, and the cocoons were recovered, washed, and dried at 37°C. The dried cocoons were added to a 0.40 mol / L NaOH solution with a bath ratio of 1:40 g / ml, and heated at 93°C for 4 hours to obtain a silk fibroin solution, which was cooled to room temperature and loaded into a dialysis bag with a molecular weight cutoff of 1500, and dialyzed with deionized water for 48 hours, with the water changed every 3 hours. After the dialysis, the solution obtained was freeze-dried at -35°C for 60 hours to obtain a silk fibroin powder.

[0030] (2) Preparation of red pigment powder: 10.0 g of dried red pepper was crushed to an average particle size of 0.7 mm, and dried at 68° C. for 4 h to obtain dried pepper fragments. The dried pepper fragments were refluxed in anhydrous ethanol at 85° C. for 4 h, filtered after reflux, and the filtrate was distilled under reduced pressure at 0.03 MPa and 65° C. to obtain red pigment powder.

[0031] (3) Silk fibroin powder and red pigment powder are mixed at a mass ratio of 20:6, and the resulting mixture is dissolved in a 0.1wt% Tween solution at a volume ratio of 1:50; the mixture is then cooled to 0°C, and 0.05mol / ml of edible glacial acetic acid (with a volume ratio of 1:2 to the Tween solution) is added, and the reaction is carried out for 2h to obtain edible pigment.

[0032] Example 3

[0033] (1) Preparation of silk fibroin powder: Weigh 10.0 g of clean silk cocoons, cut them open and clean the inner and outer surfaces, cut them into 4 mm long and 2 mm wide silkworm pieces, and dry them in an oven at 37°C. 2 CO 3 The solution was boiled for 1 hour for degumming, with a bath ratio of 1:60 g / ml, and the degumming was repeated twice, and the cocoons were recovered, washed, and dried at 37°C. The dried cocoons were added to a 0.3 mol / L NaOH solution with a bath ratio of 1:50 g / ml, and heated at 95°C for 3 hours to obtain a silk fibroin solution, which was cooled to room temperature and loaded into a dialysis bag with a molecular weight cutoff of 2000, and dialyzed with deionized water for 60 hours, with the water changed every 4 hours. After the dialysis, the solution obtained was freeze-dried at -25°C for 66 hours to obtain a silk fibroin powder.

[0034] (2) Preparation of red pigment powder: 10.0 g of dried red pepper was crushed to an average particle size of 0.9 mm, and dried at 75°C for 3 h to obtain dried pepper fragments. The dried pepper fragments were refluxed in anhydrous ethanol at 90°C for 2 h, filtered after reflux, and the filtrate was distilled under reduced pressure at 0.02 MPa and 55°C to obtain red pigment powder.

[0035] (3) Silk fibroin powder and red pigment powder were mixed at a mass ratio of 18:8, and the resulting mixture was dissolved in a 0.1wt% Tween solution at a volume ratio of 1:50; the mixture was then cooled to -5°C, and 0.05mol / ml of edible glacial acetic acid (with a volume ratio of 1:2 to the Tween solution) was added, and the reaction was carried out for 2h to obtain edible pigment.

[0036] Comparative Example 1 (the only difference from Example 1 is that no silk fibroin is added)

[0037] (1) Preparation of red pigment powder: 10.0 g of dried red pepper was crushed to an average particle size of 0.5 mm, and dried at 65° C. for 5 h to obtain dried pepper fragments. The dried pepper fragments were refluxed in anhydrous ethanol at 85° C. for 3 h, and filtered after reflux. The filtrate was distilled under reduced pressure at 0.01 MPa and 60° C. to obtain red pigment powder.

[0038] (2) Dissolve the red pigment powder in a 0.1 wt% Tween solution at a volume ratio of 1:50; then cool to -5°C, add 0.05 mol / ml edible glacial acetic acid (with a volume ratio of 1:2 to the Tween solution), and react for 2 hours to obtain the edible pigment.

[0039] Comparative Example 2 (the difference from Example 1 is that the NaOH solution is not used, but the cocoon silk is treated with protease)

[0040] (1) Preparation of silk fibroin powder: Weigh 10.0 g of clean silk cocoons, cut them open and clean the inner and outer surfaces, cut them into 2 mm long and 1 mm wide silkworm pieces, and dry them in an oven at 37°C. 2 CO 3 The solution was boiled for 1 hour for degumming, with a bath ratio of 1:50 g / ml, and the degumming was repeated twice, and the cocoons were recovered, washed, and dried at 37°C. The dried cocoons were added to a 0.35 mol / L protease solution with a bath ratio of 1:30 g / ml, and heated at 90°C for 5 hours to obtain a silk fibroin solution, which was cooled to room temperature and loaded into a dialysis bag with a molecular weight cutoff of 1000, and dialyzed with deionized water for 72 hours, with the water changed every 2 hours. After the dialysis, the solution obtained was freeze-dried at -30°C for 72 hours to obtain a silk fibroin powder.

[0041] (2) Preparation of red pigment powder: 10.0 g of dried red pepper was crushed to an average particle size of 0.5 mm, and dried at 65° C. for 5 h to obtain dried pepper fragments. The dried pepper fragments were refluxed in anhydrous ethanol at 85° C. for 3 h, and filtered after reflux. The filtrate was distilled under reduced pressure at 0.01 MPa and 60° C. to obtain red pigment powder.

[0042] (3) Silk fibroin powder and red pigment powder were mixed at a mass ratio of 25:5, and the resulting mixture was dissolved in a 0.1wt% Tween solution at a volume ratio of 1:50; the mixture was then cooled to -5°C, and 0.05mol / ml of edible glacial acetic acid (with a volume ratio of 1:2 to the Tween solution) was added, and the reaction was carried out for 2h to obtain edible pigment.

[0043] Comparative Example 3 (the difference from Example 1 is only that glacial acetic acid is not added)

[0044] (1) Preparation of silk fibroin powder: Weigh 10.0 g of clean silk cocoons, cut them open and clean the inner and outer surfaces, cut them into 2 mm long and 1 mm wide silkworm pieces, and dry them in an oven at 37°C. 2 CO 3 The solution was boiled for 1 hour for degumming, with a bath ratio of 1:50 g / ml, and the degumming was repeated twice, and the cocoons and silks were recovered, washed, and dried at 37°C. The dried cocoons and silks were added to a 0.35 mol / L NaOH solution with a bath ratio of 1:30 g / ml, and heated at 90°C for 5 hours to obtain a silk fibroin solution, which was cooled to room temperature and loaded into a dialysis bag with a molecular weight cutoff of 1000, and dialyzed with deionized water for 72 hours, with the water changed every 2 hours. After the dialysis, the solution obtained was freeze-dried at -30°C for 72 hours to obtain a silk fibroin powder.

[0045] (2) Preparation of red pigment powder: 10.0 g of dried red pepper was crushed to an average particle size of 0.5 mm, and dried at 65° C. for 5 h to obtain dried pepper fragments. The dried pepper fragments were refluxed in anhydrous ethanol at 85° C. for 3 h, and filtered after reflux. The filtrate was distilled under reduced pressure at 0.01 MPa and 60° C. to obtain red pigment powder.

[0046] (3) Silk fibroin powder and red pigment powder were mixed at a mass ratio of 25:5, and the resulting mixture was dissolved in a 0.1 wt % Tween solution at a volume ratio of 1:50; the mixture was then cooled to -5°C and maintained for 2 hours to obtain an edible pigment.

[0047] Comparative Example 4 (the only difference from Example 1 is that low temperature operation was not performed when adding edible glacial acetic acid)

[0048] (1) Preparation of silk fibroin powder: Weigh 10.0 g of clean silk cocoons, cut them open and clean the inner and outer surfaces, cut them into 2 mm long and 1 mm wide silkworm pieces, and dry them in an oven at 37°C. 2 CO 3 The solution was boiled for 1 hour for degumming, with a bath ratio of 1:50 g / ml, and the degumming was repeated twice, and the cocoons and silks were recovered, washed, and dried at 37°C. The dried cocoons and silks were added to a 0.35 mol / L NaOH solution with a bath ratio of 1:30 g / ml, and heated at 90°C for 5 hours to obtain a silk fibroin solution, which was cooled to room temperature and loaded into a dialysis bag with a molecular weight cutoff of 1000, and dialyzed with deionized water for 72 hours, with the water changed every 2 hours. After the dialysis, the solution obtained was freeze-dried at -30°C for 72 hours to obtain a silk fibroin powder.

[0049] (2) Preparation of red pigment powder: 10.0 g of dried red pepper was crushed to an average particle size of 0.5 mm, and dried at 65° C. for 5 h to obtain dried pepper fragments. The dried pepper fragments were refluxed in anhydrous ethanol at 85° C. for 3 h, and filtered after reflux. The filtrate was distilled under reduced pressure at 0.01 MPa and 60° C. to obtain red pigment powder.

[0050] (3) Silk fibroin powder and red pigment powder were mixed at a mass ratio of 25:5, and the resulting mixture was dissolved in a 0.1 wt% Tween solution at a volume ratio of 1:50; at room temperature, 0.05 mol / ml edible glacial acetic acid (with a volume ratio of 1:2 to the Tween solution) was added and reacted for 2 h to obtain edible pigment.

[0051] Comparative Example 5 (the difference from Example 1 is only that an excess of edible glacial acetic acid is added)

[0052] (1) Preparation of silk fibroin powder: Weigh 10.0 g of clean silk cocoons, cut them open and clean the inner and outer surfaces, cut them into 2 mm long and 1 mm wide silkworm pieces, and dry them in an oven at 37°C. 2 CO 3 The solution was boiled for 1 hour for degumming, with a bath ratio of 1:50 g / ml, and the degumming was repeated twice, and the cocoons and silks were recovered, washed, and dried at 37°C. The dried cocoons and silks were added to a 0.35 mol / L NaOH solution with a bath ratio of 1:30 g / ml, and heated at 90°C for 5 hours to obtain a silk fibroin solution, which was cooled to room temperature and loaded into a dialysis bag with a molecular weight cutoff of 1000, and dialyzed with deionized water for 72 hours, with the water changed every 2 hours. After the dialysis, the solution obtained was freeze-dried at -30°C for 72 hours to obtain a silk fibroin powder.

[0053] (2) Preparation of red pigment powder: 10.0 g of dried red pepper was crushed to an average particle size of 0.5 mm, and dried at 65° C. for 5 h to obtain dried pepper fragments. The dried pepper fragments were refluxed in anhydrous ethanol at 85° C. for 3 h, and filtered after reflux. The filtrate was distilled under reduced pressure at 0.01 MPa and 60° C. to obtain red pigment powder.

[0054] (3) Silk fibroin powder and red pigment powder were mixed at a mass ratio of 25:5, and the resulting mixture was dissolved in a 0.1wt% Tween solution at a volume ratio of 1:50; the mixture was then cooled to -5°C, and 0.05mol / ml of edible glacial acetic acid (with a volume ratio of 1:1 to the Tween solution) was added, and the mixture was reacted for 2h to obtain edible pigment.

[0055] Comparative Example 6 (the only difference from Example 1 is that an excess amount of silk fibroin powder is added)

[0056] (1) Preparation of silk fibroin powder: Weigh 10.0 g of clean silk cocoons, cut them open and clean the inner and outer surfaces, cut them into 2 mm long and 1 mm wide silkworm pieces, and dry them in an oven at 37°C. 2 CO 3 The solution was boiled for 1 hour for degumming, with a bath ratio of 1:50 g / ml, and the degumming was repeated twice, and the cocoons and silks were recovered, washed, and dried at 37°C. The dried cocoons and silks were added to a 0.35 mol / L NaOH solution with a bath ratio of 1:30 g / ml, and heated at 90°C for 5 hours to obtain a silk fibroin solution, which was cooled to room temperature and loaded into a dialysis bag with a molecular weight cutoff of 1000, and dialyzed with deionized water for 72 hours, with the water changed every 2 hours. After the dialysis, the solution obtained was freeze-dried at -30°C for 72 hours to obtain a silk fibroin powder.

[0057] (2) Preparation of red pigment powder: 10.0 g of dried red pepper was crushed to an average particle size of 0.5 mm, and dried at 65° C. for 5 h to obtain dried pepper fragments. The dried pepper fragments were refluxed in anhydrous ethanol at 85° C. for 3 h, and filtered after reflux. The filtrate was distilled under reduced pressure at 0.01 MPa and 60° C. to obtain red pigment powder.

[0058] (3) Silk fibroin powder and red pigment powder were mixed at a mass ratio of 36:5, and the resulting mixture was dissolved in a 0.1wt% Tween solution at a volume ratio of 1:50; the mixture was then cooled to -5°C, and 0.05mol / ml edible glacial acetic acid (with a volume ratio of 1:2 to the Tween solution) was added, and the reaction was carried out for 2h to obtain the edible pigment.

[0059] Comparative Example 7 (the difference from Example 1 is that the silk fibroin is replaced by a mixture of glycine and alanine)

[0060] (1) Preparation of red pigment powder: 10.0 g of dried red pepper was crushed to an average particle size of 0.5 mm, and dried at 65° C. for 5 h to obtain dried pepper fragments. The dried pepper fragments were refluxed in anhydrous ethanol at 85° C. for 3 h, and filtered after reflux. The filtrate was distilled under reduced pressure at 0.01 MPa and 60° C. to obtain red pigment powder.

[0061] (2) Mix amino acids (glycine and alanine in a mass ratio of 1:1) and red pigment powder in a mass ratio of 25:5, and dissolve the resulting mixture in a 0.1wt% Tween solution in a volume ratio of 1:50; then cool to -5°C, add 0.05mol / ml edible glacial acetic acid (with a volume ratio of 1:2 to the Tween solution), and react for 2h to obtain edible pigment. Performance Test

[0062] (1) Determination of amino acid content: First, the amino acids remaining in the pigment were removed by nanofiltration membrane separation, and then 93.2 ml of 0.1 mol / L Na 2 HPO 4 solution and 6.8 ml of 0.1 mol / L NaH 2 PO 4 The solution was mixed and added to 400 ml of deionized water to prepare a buffer solution with a pH of 8.0. The above-mentioned edible coloring except amino acids was mixed with the buffer solution at a mixing mass ratio of 1:10. Then 2 wt% of ninhydrin solution (the mass ratio of ninhydrin solution to the mixed solution was 1:50) was added and then boiled in a water bath for 2 minutes to form a purple complex. The optical density value was detected at an absorption wavelength of 570 nm, thereby calculating the free amino acid content.

[0063] (2) Pigment stability: The food pigment prepared above was placed under ultraviolet light, and its color was measured with a colorimeter every 1 h, and the saturation was recorded.

[0064] (3) Foaming after adding pigment to cake: During the cake making process, the same mass of the prepared edible pigment was added to the cake to foam. The cake was cut open to observe the foaming of the cake and the pore size of the cake was recorded.

[0065] The edible pigments obtained in Examples 1-3 and Comparative Examples 1-7 were analyzed, and the results are shown in Tables 1-4.

[0066] Table 1

[0067]

[0068] Table 2

[0069]

[0070] Table 3

[0071]

[0072] Table 4

[0073]

[0074] As shown in Table 1 and Table 3, compared with Example 1-3, due to the difference in the content of fibroin, as the content of fibroin increases, the performance of the pigment in all aspects is more excellent, such as better fastness, higher amino acid content, foaming effect, and better cake pore regularity. As shown in Table 2 and Table 4, compared with Example 1, Comparative Example 1 has a substantially zero amino acid content in the pigment due to the absence of fibroin, so the foaming performance of the cake is extremely poor, and, due to the absence of fibroin, capsanthin is easily decomposed by ultraviolet light, so the saturation is very low in a short time, and its storage time is the shortest. Compared with Example 1, Comparative Example 2 uses protease when processing fibroin, which can cause the content of free amino acids to decrease, and the pore size of the cake is significantly irregular compared with Example 1. Compared with Example 1, Comparative Example 3 has a higher free amino acid content in the solution and a better foaming effect because acetic acid is not added, so the corresponding ability to protect the pigment from decomposition will deteriorate. Compared with Example 1, Comparative Example 4 does not perform low temperature treatment on the pigment solution, resulting in a decrease in the amount of amino acid and pigment binding. The principle is the same as that of Comparative Example 3. The reason for the difference is that the ability of amino acids to bind to pigments is affected by low temperature and acid addition, but is more affected by environmental acidity, so the binding of amino acids and pigments in Comparative Example 4 will be more. Compared with Example 1, the excess of acetic acid in Comparative Example 5 leads to enhanced solution acidity, which competes with the pigment cavities and leads to a decrease in the binding rate of amino acids and pigments. Compared with Example 1, when the content of silk protein exceeds 5:1, even if it is increased, its various performances do not change much, because the ability of pigments to bind amino acids is limited, so it is not appropriate to add excessive silk protein. Compared with Example 1, Comparative Example 7 shows that the composite foaming effect of multiple amino acids in silk protein is better, and it also contains amino acids that can absorb ultraviolet rays and protect pigments from being decomposed. There are more types of amino acids that bind to pigments, so the color saturation of the pigment is higher.

[0075] The above embodiments of the present invention are merely examples for illustrating the present invention, and are not intended to limit the embodiments of the present invention. For those skilled in the art, other different forms of changes and modifications can be made based on the above description. It is impossible to list all the embodiments here. Any obvious changes or modifications derived from the technical solution of the present invention are still within the scope of protection of the present invention.

Claims

1. A method for preparing a capsicum red food coloring rich in free amino acids, characterized in that: The following steps are involved: (1) Processing dried red pepper to obtain red pigment powder; (2) Mixing silk fibroin powder and red pigment powder in a mass ratio of 17-25:5-8, adding the obtained mixture into a Tween solution with a mass concentration of 0.1-0.2% to dissolve, the volume ratio of the mixture to the Tween solution is 1:50, then adding edible glacial acetic acid with a concentration of 0.04-0.06 mol / mL at a temperature of -5~5°C, the volume ratio of edible glacial acetic acid to the Tween solution is 1:2, reacting for 2-3 hours to obtain edible pigment; The silk fibroin powder is prepared by cutting silkworm cocoons, washing and drying them to obtain silkworm fragments; boiling and degumming the silkworm fragments in a Na2CO3 solution, and then recovering the cocoon silk, washing it and drying it; adding the dried cocoon silk into a NaOH solution, heating it at 90-95°C for reaction for 3-5h to obtain a silk fibroin solution, and then dialyzing and freeze-drying it to obtain the silk fibroin powder.

2. The method for preparing the capsicum red food coloring rich in free amino acids as claimed in claim 1, characterized in that, In step (1), the processing of the dried red pepper is as follows: the dried red pepper is crushed and dried to obtain dried pepper fragments; the dried pepper fragments are refluxed in anhydrous ethanol, filtered after the reflux is completed, and the filtrate is subjected to reduced pressure distillation to obtain red pigment powder.

3. The preparation method of the capsicum red food coloring rich in free amino acids as claimed in claim 2, characterized in that, The reflux temperature is 80-90°C and the reflux time is 2-4h.

4. The method for preparing the capsicum red food coloring rich in free amino acids as claimed in claim 2 or 3, characterized in that, The temperature of the reduced pressure distillation is 55-65°C and the pressure is 0.01-0.03MPa.

5. The method for preparing the capsicum red food coloring rich in free amino acids as claimed in claim 1, characterized in that, The bath ratio of the silkworm fragments to the Na2CO3 solution is 1:30-80 g / mL; the concentration of the Na2CO3 solution is 0.1-1.2 wt%.

6. The method for preparing the capsicum red food coloring rich in free amino acids as claimed in claim 1 or 5, characterized in that: The bath ratio of the dried cocoon silk and the NaOH solution is 1:30-50 g / mL; the concentration of the NaOH solution is 0.1-0.5 mol / L; the freeze drying is carried out at a temperature of -60°C to 0°C for 2-3 days.

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