Preparation method of monascus red pigment and prepared monascus red pigment

Abstract

The invention discloses a preparation method of monascus red pigment and the prepared monascus red pigment, and relates to the field of food additives. The preparation method of the monascus red pigment comprises the following steps: S1, inoculating a monascus strain into a basic culture medium to carry out batch propagation operation; s2, after the bacterial colony in the step S1 is mature, carrying out centrifugal separation to take solid residues, adding 3-5 times of alcohol with the volume concentration of 95% or above, stirring, then carrying out solid-liquid separation to take liquid, and concentrating at 45-55 DEG C to obtain a concentrated solution; s3, a protective agent is added into the concentrated solution obtained in the step S2, after high-speed uniform stirring is conducted, cooling and curing are conducted, and the protective agent is at least one of maltodextrin, Arabic gum and a sodium alginate water solution; and S4, performing freeze drying on the cooled and cured product in the step S3 to obtain the monascus red pigment. The monascus red pigment prepared by the method has the advantages of high yield, high thermal stability and the like.

Description

Technical Field

[0001] The present application relates to the field of food additives, and in particular to a method for preparing monascus red pigment and the prepared monascus red pigment. Background Art

[0002] Monascus red is a red food additive made by fermentation of Monascus purpureus. It is a secondary metabolite of Monascus purpureus and has rich nutritional and medicinal value. Among them, Monascus red pigment is non-toxic and harmless to the body, has abundant sources, high safety, natural coloring, and has many physiological activities such as antioxidant, anti-tumor, and anti-fatigue. It is widely used in the coloring of meat products, pasta, and wine.

[0003] At present, the production process of Monascus red mainly includes the steps of selection and optimization of fermentation medium, biotransformation, physical and chemical extraction, separation and drying. Among them, spray drying is currently widely used in the drying of Monascus red pigment due to its rapid drying characteristics. However, spray drying needs to be carried out under high temperature conditions, which can easily cause the inactivation of the active substances in Monascus red pigment. Moreover, when Monascus red pigment is exposed to heat during the subsequent storage process, it is easy to fade, which reduces the market competitiveness of Monascus red pigment. Summary of the invention

[0004] The present application provides a method for preparing a monascus red pigment and the prepared monascus red pigment, so as to solve the problem that the existing spray drying method of the monascus red pigment easily causes the loss of active substances and the monascus red pigment easily fades when heated during the subsequent storage process.

[0005] In the first aspect, the present application provides a method for preparing red pigment of Monascus using the following technical scheme: A method for preparing monascus red pigment comprises the following steps: S1. Inoculate the Monascus species into the basic culture medium to carry out batch expansion operations; S2, after the bacterial colonies in step S1 mature, centrifuge to obtain the solid residue, add 3-5 times the volume of alcohol with a concentration of more than 95%, stir, then separate the solid and liquid to obtain the liquid, and concentrate at 45°C-55°C to obtain a concentrated solution; S3, adding a protective agent to the concentrated solution of step S2, stirring at high speed, and cooling to solidify, wherein the protective agent is at least one of maltodextrin, gum arabic, and sodium alginate aqueous solution; S4, freeze-drying the product after cooling and solidification in step S3 to obtain Monascus red pigment.

[0006] The difference from the prior art is that: (1) the present application adopts freeze drying to freeze dry the concentrated solution obtained after fermentation of Monascus species to obtain Monascus red pigment; freeze drying is carried out at low temperature and low pressure, which can prevent the problem of high temperature degradation of Monascus red pigment; (2) in view of the fact that the molecular structure of macromolecules such as proteins and polysaccharides in Monascus red is easily squeezed by ice crystals and molecular chain breaks or spatial structure changes occur, forcing the effective components of Monascus red pigment to be damaged by ice crystals, so the present application adds a protective agent before freeze drying the concentrated solution. The protective agent adopts at least one of maltodextrin, gum arabic, and sodium alginate aqueous solution. The protective agent can be embedded on the surface of Monascus red pigment to form Monascus red pigment with an embedded structure. Among them, the protective agent can protect the effective components of Monascus red pigment from ice crystal damage on the one hand, improve the yield of Monascus red pigment, and on the other hand, it can also reduce the influence of the external environment on Monascus red pigment, which is conducive to improving the thermal stability of Monascus red pigment.

[0007] Specifically, the present application adds a protective agent to the concentrated solution and then recovers the red yeast powder product by freeze drying. The yield of the red yeast powder product is as high as more than 98%, while the concentrate is directly freeze dried without adding a protective agent, and the yield of the red yeast powder product is 90-95%. In addition, the recovery rate of red yeast spray drying is between 50-90%. By optimizing process parameters and adding protective agents, the highest recovery rate of the spray drying method is 85%-90%, that is, when the red yeast powder product is recovered by spray drying, it is difficult to achieve a recovery rate of more than 95%. In summary, the red yeast powder product is recovered by the method of the present application, which has better recovery stability and higher yield.

[0008] Preferably, the protective agent comprises maltodextrin, gum arabic and a sodium alginate aqueous solution with a mass concentration of 1.5%-2.5%, the maltodextrin is used in an amount of 15%-25% by weight of the concentrated solution in step S2, the gum arabic is used in an amount of 4%-6% by weight of the concentrated solution in step S2, and the sodium alginate aqueous solution with a mass concentration of 1.5%-2.5% is used in an amount of 0.2%-0.3% by weight of the concentrated solution in step S2.

[0009] In the present application, when maltodextrin, gum arabic and sodium alginate are used as protective agents, the wall material structure on the surface of red yeast rice pigment can be improved under the coordinated cooperation of maltodextrin, gum arabic and sodium alginate in a reasonable ratio. The wall material structure can be protected from ice crystal damage and denaturation and degradation during freeze drying, and has a uniform and tiny porous structure, which is convenient for the diffusion and sublimation of water vapor while preventing the loss of effective ingredients, and can improve the drying effect of red yeast rice pigment. In addition, the wall material structure can also reduce the impact of the external environment on the red yeast rice pigment, which is conducive to improving the thermal stability of the red yeast rice pigment.

[0010] Further preferably, the amount of maltodextrin is 20% by weight of the concentrated solution in step S2, the amount of gum arabic is 5% by weight of the concentrated solution in step S2, and the amount of the sodium alginate aqueous solution with a mass concentration of 1.5%-2.5% is 0.25% by weight of the concentrated solution in step S2.

[0011] Preferably, the DE value of the maltodextrin is 16-20.

[0012] In the present application, the DE value of maltodextrin is preferably 16-20. The maltodextrin molecular chain within this DE value range is shorter, the degree of polymerization is lower, and the solubility and dispersibility are good. It can improve the drying effect and product uniformity of Monascus red pigment while improving the water solubility and quality stability of Monascus red pigment.

[0013] Preferably, the molecular weight of the gum arabic is 220,000-300,000.

[0014] In the present application, the preferred molecular weight of gum arabic is 220,000-300,000, wherein gum arabic within this molecular weight range can be evenly dispersed in the concentrate and can serve as a stabilizer during the freezing process of monascus red pigment, thereby enhancing the stability of monascus red pigment and preventing the denaturation or degradation of monascus red pigment during the freeze-drying process, which is conducive to obtaining monascus red pigment that is both water-soluble and stable.

[0015] Preferably, in the sodium alginate aqueous solution with a mass concentration of 1.5%-2.5%, the molecular weight of the sodium alginate is 50,000-100,000.

[0016] In the present application, the molecular weight of sodium alginate is preferably 50,000-100,000, which is beneficial to improving the drying effect and product uniformity of the monascus red pigment, and is beneficial to obtaining a monascus red pigment with good water solubility and stable quality.

[0017] In step S3, the rotation speed of high-speed stirring is 10000r / min-15000r / min.

[0018] In the present application, the rotation speed is controlled within the above range. On the one hand, the protective agent can be evenly dispersed in the concentrated solution, which is beneficial to improving the embedding effect of the finished Monascus red pigment, thereby improving the stability of the Monascus red pigment; on the other hand, the Monascus red pigment can be protected from shear damage, which is beneficial to improving the yield of the Monascus red pigment.

[0019] In step S3, the curing temperature is (-38°C)-(-45°C).

[0020] Preferably, in step S4, the freeze-drying comprises the following steps: S41. Dehydrate for 1-2 hours in an environment with a temperature of -25°C to -20°C and a vacuum degree of 5Pa-10Pa; S42, dehydrate for 1-2h in an environment with a temperature of -15℃~-10℃ and a vacuum degree of 5Pa-10Pa; S43, dehydrate for 2-4 hours in an environment with a temperature of -6°C to 0°C and a vacuum degree of 5Pa-10Pa; S44, dehydrate for 2-4 hours in an environment with a temperature of 1°C to 5°C and a vacuum degree of 5Pa-10Pa; S45, dehydrate for 4-6 hours in an environment with a temperature of 6°C to 10°C and a vacuum degree of 5Pa-10Pa; S46, dehydrate for 1-2h in an environment with a temperature of 10℃~15℃ and a vacuum degree of 5Pa-10Pa; S47, dehydrate for 1-2h in an environment with a temperature of 20℃~25℃ and a vacuum degree of 5Pa-10Pa; S48. Dehydrate for 6-8 hours in an environment with a temperature of 30℃~35℃ and a vacuum degree of 5Pa-10Pa.

[0021] In the present application, the red pigment of Monascus is freeze-dried according to the above freeze-drying curve, which is conducive to preventing the inhomogeneity in the crystallization and de-crystallization process, thereby improving the uniformity and stability of the red pigment product, so as to better retain the active ingredients and original quality of the red pigment product, and improve the drying effect of the red pigment of Monascus, and reduce the water content of the red pigment of Monascus. In addition, the design of the above freeze-drying curve of the present application can also reduce energy consumption, reduce production costs, shorten the time of the entire freeze-drying process, thereby improving production efficiency.

[0022] In a second aspect, the present application provides a Monascus red pigment, which is prepared by any one of the above-mentioned methods for preparing Monascus red pigment.

[0023] The Monascus red pigment of the present application is obtained by freeze-drying, and a protective agent is added during the freeze-drying process. The freeze-drying process is carried out under low temperature and low pressure conditions, so that the water in the Monascus red pigment is directly sublimated from a solid state to a gaseous state, avoiding problems such as reduced pigment activity, discoloration, and decomposition caused by high-temperature drying. In addition, the addition of the protective agent protects the effective ingredients of the Monascus red pigment from damage by ice crystals, retains the color valence and other properties of the Monascus red pigment to the greatest extent, and ensures its quality in application.

[0024] In summary, this application at least includes the following beneficial technical effects: (1) The present application adds a protective agent to the concentrated solution and then recovers the red yeast powder product by freeze drying. The yield of the red yeast powder product is as high as more than 98%, while the concentrate is directly freeze dried without adding a protective agent, and the yield of the red yeast powder product is 90-95%. In addition, the recovery rate of red yeast spray drying is between 50-90%. The highest recovery rate of the spray drying method is 85%-90% by optimizing process parameters and adding protective agents. That is, when the red yeast powder product is recovered by spray drying, it is difficult to achieve a recovery rate of more than 95%. In summary, the red yeast powder product is recovered by the method of the present application, which has better recovery stability and higher yield. In addition, it can also reduce the impact of the external environment on the red yeast pigment and improve the thermal stability of the red yeast pigment.

[0025] (2) In the present application, when maltodextrin, gum arabic and sodium alginate are used as protective agents, the wall material structure on the surface of red yeast rice pigment can be improved under the synergistic cooperation of maltodextrin, gum arabic and sodium alginate in a reasonable ratio. The wall material structure can not only be protected from ice crystal damage and denaturation and degradation during freeze-drying, but also has a uniform and tiny porous structure, which is convenient for the diffusion and sublimation of water vapor while preventing the loss of effective ingredients, and can improve the drying effect of red yeast rice pigment. In addition, the wall material structure can also reduce the impact of the external environment on the red yeast rice pigment, which is beneficial to improve the thermal stability of the red yeast rice pigment. DETAILED DESCRIPTION

[0026] The present application is further described below in conjunction with specific experiments. Example

[0027] [Example 1] A method for preparing monascus red pigment comprises the following steps: S1. Inoculate the Monascus species into the basal culture medium, control the temperature to 35° C., and culture in a shake flask for 6 days; wherein the Monascus species is the purple Monascus species numbered CGMCC No.3.15548 purchased from the Institute of Microbiology, Chinese Academy of Sciences, and the basal culture medium includes 10 g of rice flour, 2 g of corn steep liquor powder, 1 g of glucose, 10 g of peptone, 15 g of sodium nitrate, 0.2 g of magnesium sulfate, and 0.15 g of potassium dihydrogen sulfate, and the pH is adjusted to 7.0 to obtain a culture medium; S2. After the bacterial colonies in step S1 mature, centrifuge to obtain the solid residue, add 4 times the volume of alcohol with a concentration of more than 95%, stir at a stirring speed of 100 r / min for 10 hours, then separate the solid and liquid to obtain the liquid, and concentrate it at 50° C. using a low-temperature vacuum concentrator to obtain a concentrated solution, the solid content of the concentrated solution is 38.2%; S3, adding a protective agent to the concentrated solution of step S2, stirring at a high speed of 10000r / min for 5min, cooling to -38°C for solidification; the protective agent is specifically maltodextrin with a DE value of 16-20, and the amount of maltodextrin is 15% of the weight of the concentrated solution of step S2; S4, freeze-drying the product after cooling and solidification in step S3, freeze-drying is carried out according to the following steps S41 to S48 to obtain red pigment of Monascus, wherein: S41, dehydrate for 2 hours in an environment with a temperature of -25°C and a vacuum degree of 10Pa; S42, dehydrate for 2 hours in an environment with a temperature of -15°C and a vacuum degree of 10Pa; S43, dehydrate for 2 hours in an environment with a temperature of -6°C and a vacuum degree of 10Pa; S44, dehydrate for 2 hours in an environment with a temperature of 1°C and a vacuum degree of 10Pa; S45, dehydrate for 6 hours in an environment with a temperature of 6°C and a vacuum degree of 10Pa; S46, dehydrate for 1 hour in an environment with a temperature of 10°C and a vacuum degree of 10Pa; S47, dehydrate for 1 hour in an environment with a temperature of 20°C and a vacuum degree of 10Pa; S48. Dehydrate for 8 hours in an environment with a temperature of 30°C and a vacuum degree of 10Pa.

[0028] [Example 2] A method for preparing monascus red pigment comprises the following steps: S1. Inoculate the Monascus species into the basal culture medium, control the temperature to 35° C., and culture in a shake flask for 6 days; wherein the Monascus species is the purple Monascus species numbered CGMCC No.3.15548 purchased from the Institute of Microbiology, Chinese Academy of Sciences, and the basal culture medium includes 10 g of rice flour, 2 g of corn steep liquor powder, 1 g of glucose, 10 g of peptone, 15 g of sodium nitrate, 0.2 g of magnesium sulfate, and 0.15 g of potassium dihydrogen sulfate, and the pH is adjusted to 7.0 to obtain a culture medium; S2. After the bacterial colonies in step S1 mature, centrifuge to obtain the solid residue, add 4 times the volume of alcohol with a concentration of more than 95%, stir at a stirring speed of 100 r / min for 10 hours, then separate the solid and liquid to obtain the liquid, and concentrate it at 50° C. using a low-temperature vacuum concentrator to obtain a concentrated solution, the solid content of the concentrated solution is 38.2%; S3, adding a protective agent to the concentrated solution of step S2, stirring at a high speed of 15000r / min for 3min, cooling to -45°C for solidification; the protective agent is specifically maltodextrin with a DE value of 16-20, and the amount of maltodextrin is 25% of the weight of the concentrated solution of step S2; S4, freeze-drying the product after cooling and solidification in step S3, freeze-drying is carried out according to the following steps S41 to S48 to obtain red pigment of Monascus, wherein: S41, dehydrate in an environment with a temperature of -20°C and a vacuum degree of 5Pa for 1h; S42, dehydrate in an environment with a temperature of -10°C and a vacuum degree of 5Pa for 1h; S43, dehydration for 4 hours in an environment with a temperature of 0°C and a vacuum degree of 5Pa; S44, dehydrate in an environment with a temperature of 5°C and a vacuum degree of 5Pa for 4 hours; S45, dehydrate for 4 hours in an environment with a temperature of 10°C and a vacuum degree of 5Pa; S46, dehydrate for 2 hours in an environment with a temperature of 15°C and a vacuum degree of 5Pa; S47, dehydrate for 2h in an environment with a temperature of 25°C and a vacuum degree of 5Pa; S48. Dehydrate for 6 hours in an environment with a temperature of 35°C and a vacuum degree of 5Pa.

[0029] [Example 3] A method for preparing red pigment of Monascus, which differs from that of Example 1 in that: in S3, a different protective agent is used.

[0030] In this embodiment, the protective agent in step S3 is specifically gum arabic with a molecular weight of 220,000-300,000, and the amount of gum arabic used is 6% of the weight of the concentrated solution in step S2.

[0031] [Example 4] A method for preparing red pigment of Monascus, which differs from that of Example 1 in that: in S3, a different protective agent is used.

[0032] In this embodiment, the protective agent in step S3 is a sodium alginate aqueous solution with a mass concentration of 2%, and the amount of the sodium alginate aqueous solution with a mass concentration of 2% is 0.3% of the weight of the concentrated solution in step S2; wherein, the sodium alginate aqueous solution with a mass concentration of 2% is obtained by uniformly mixing sodium alginate with a molecular weight of 70,000-80,000 and water in a weight ratio of 2:98.

[0033] [Example 5] A method for preparing red pigment of Monascus, which differs from that of Example 1 in that: in S3, a different protective agent is used.

[0034] In this embodiment, the protective agent of step S3 includes maltodextrin with a DE value of 16-20, gum arabic with a molecular weight of 220,000-300,000, and a sodium alginate aqueous solution with a mass concentration of 2%, wherein the amount of maltodextrin is 15% of the weight of the concentrate in step S2, the amount of gum arabic is 6% of the weight of the concentrate in step S2, and the amount of the sodium alginate aqueous solution with a mass concentration of 2% is 0.3% of the weight of the concentrate in step S2. In this embodiment, the sodium alginate aqueous solution with a mass concentration of 2% is obtained by uniformly mixing sodium alginate with a molecular weight of 70,000-80,000 and water in a weight ratio of 2:98.

[0035] [Example 6] A method for preparing red pigment of Monascus, which differs from that of Example 1 in that: in S3, a different protective agent is used.

[0036] In this embodiment, the protective agent of step S3 includes maltodextrin with a DE value of 16-20, gum arabic with a molecular weight of 220,000-300,000, and a sodium alginate aqueous solution with a mass concentration of 2%, wherein the amount of maltodextrin is 20% of the weight of the concentrate in step S2, the amount of gum arabic is 5% of the weight of the concentrate in step S2, and the amount of the sodium alginate aqueous solution with a mass concentration of 2% is 0.25% of the weight of the concentrate in step S2. In this embodiment, the sodium alginate aqueous solution with a mass concentration of 2% is obtained by uniformly mixing sodium alginate with a molecular weight of 70,000-80,000 and water in a weight ratio of 2:98.

[0037] [Example 7] A method for preparing red pigment of Monascus, which differs from that of Example 1 in that: in S3, a different protective agent is used.

[0038] In this embodiment, the protective agent of step S3 includes maltodextrin with a DE value of 16-20, gum arabic with a molecular weight of 220,000-300,000, and a sodium alginate aqueous solution with a mass concentration of 2%, wherein the amount of maltodextrin is 25% of the weight of the concentrate in step S2, the amount of gum arabic is 4% of the weight of the concentrate in step S2, and the amount of the sodium alginate aqueous solution with a mass concentration of 2% is 0.2% of the weight of the concentrate in step S2. In this embodiment, the sodium alginate aqueous solution with a mass concentration of 2% is obtained by uniformly mixing sodium alginate with a molecular weight of 70,000-80,000 and water in a weight ratio of 2:98.

[0039] [Example 8] A method for preparing red pigment of Monascus, which differs from [Example 6] in that: in this embodiment, maltodextrin with a DE value of 4-6 is used in the malt paste selection in step S3.

[0040] [Example 9] A method for preparing monascus red pigment, which differs from [Example 6] in that: in this example, the gum arabic in step S3 is replaced by guar gum.

[0041] [Example 10] A method for preparing monascus red pigment, which differs from [Example 6] in that: in this embodiment, a sodium alginate aqueous solution with a mass concentration of 2% is obtained by uniformly mixing sodium alginate with a molecular weight of 140,000-150,000 and water in a weight ratio of 2:98.

[0042] [Example 11] A method for preparing red pigment of Monascus, which differs from Example 6 in that: in step S4, freeze drying is performed according to the following steps S41 to S48: S41, dehydrate for 3 hours in an environment with a temperature of -25°C and a vacuum degree of 10Pa; S42, dehydrate for 3 hours in an environment with a temperature of -15°C and a vacuum degree of 10Pa; S43, dehydrate in an environment with a temperature of -6°C and a vacuum degree of 10Pa for 1 hour; S44, dehydrate for 1 hour in an environment with a temperature of 1°C and a vacuum degree of 10Pa; S45, dehydrate for 4 hours in an environment with a temperature of 6°C and a vacuum degree of 10Pa; S46, dehydrate for 3 hours in an environment with a temperature of 10°C and a vacuum degree of 10Pa; S47, dehydrate in an environment with a temperature of 20°C and a vacuum degree of 10Pa for 4 hours; S48. Dehydrate for 5 hours in an environment with a temperature of 30°C and a vacuum degree of 10Pa.

[0043] Comparative Example [Comparative Example 1] A method for preparing red pigment of Monascus, which differs from [Example 1] in that: No protective agent maltodextrin was added in step S3.

[0044] [Comparative Example 2] A method for preparing red pigment of Monascus, which differs from [Example 1] in that: In step S3, sodium alginate is used as the protective agent. Sodium alginate is directly added to the concentrated solution of step S2. The amount of sodium alginate used is 0.02% of the weight of the concentrated solution of step S2.

[0045] Performance testing (1) Yield: Calculate the yield of red pigment in each embodiment and comparative example, wherein red pigment yield = (red pigment freeze-dried powder unit color value * total weight) / (freeze-dried solution unit color value * total weight) * 100%, wherein the red pigment freeze-dried powder unit color value and the solution unit color value before freeze-drying are the average color values ​​of three randomly selected samples, and the standard deviation of the color value of the three red pigment freeze-dried powder samples is recorded at the same time. The smaller the standard deviation, the better the product uniformity. The color value detection is carried out with reference to Appendix A in GB 1886.181-2016 "National Food Safety Standard Food Additive Red Rice".

[0046] (2) Diffusion time: Accurately weigh 1 g of Monascus red pigment powder sample, use a 100 mL measuring cylinder of the same specification to measure 100 mL of distilled water, pour the Monascus red pigment powder from the top of the measuring cylinder, observe the Monascus red powder, and record the time required for the red color in the measuring cylinder to diffuse to the bottom of the measuring cylinder. The shorter the diffusion time, the faster the dissolution rate of the Monascus red pigment.

[0047] (3) Loss on drying: Refer to the direct drying method in GB 5009.3-2016 “National Food Safety Standard - Determination of Water Content in Food” for testing. The lower the loss on drying, the lower the water content of the product.

[0048] (4) Thermal stability: The red pigment of each embodiment and comparative example was dissolved in water to prepare a diluted sample solution with an absorbance of about 1.1, and the specific absorbance A1 of the diluted sample solution corresponding to each embodiment and comparative example was tested, and then the diluted sample solution prepared in each embodiment and comparative example was poured into a colorimetric tube to prepare 4 sets of parallel samples, and then each parallel sample was placed on a test tube rack, and placed in a water bath at 90°C for 6 hours, taken out, and cooled in a dark place, and the average absorbance of the 4 parallel samples after cooling was tested and recorded as A2. Among them, the smaller the difference between A1 and A2, the better the thermal stability of the red pigment sample.

[0049] Table 1 Yield and color value standard deviation record Table 2 Diffusion time and drying loss record sample Diffusion time / s Loss on drying / % Example 1 60 4.85 Example 2 60 4.46 Example 3 60 4.26 Example 4 60 4.91 Example 5 40 2.51 Example 6 40 2.12 Example 7 40 2.46 Example 8 60 3.67 Example 9 60 3.48 Example 10 60 3.75 Embodiment 11 40 2.78 Comparative Example 1 60 2.08 Comparative Example 2 90 6.92 Table 3 Combining the comparative example 1 with the example 1 and the test data in Tables 1-3, it can be seen that: in the comparative example 1, no protective agent was added, and the yield of the Monascus red pigment obtained by the freeze-drying method was less than 95%. At the same time, the thermal stability of the Monascus red pigment was significantly reduced.

[0050] Combining the comparative example 2 with the test data in Example 2 and Tables 1-3, it can be seen that the sodium alginate in the comparative example 2 is not added in the form of an aqueous solution, the yield of the obtained red pigment of Monascus is less than 95%, and there are disadvantages such as poor product uniformity, slow dissolution rate, low drying efficiency, and poor thermal stability. It can be seen that sodium alginate should be added in the form of a sodium alginate aqueous solution.

[0051] Combining the test data in Example 1, Examples 3-7 and Tables 1-3, it can be seen that when maltodextrin, gum arabic and sodium alginate are combined as protective agents, the wall material structure on the surface of the Monascus red pigment can be improved under the synergistic cooperation of maltodextrin, gum arabic and sodium alginate in a reasonable ratio. The wall material structure can not only be protected from ice crystal damage and denaturation and degradation during the freeze-drying process, but also has a uniform and fine porous structure, which facilitates the diffusion and sublimation of water while preventing the loss of effective ingredients, thereby improving the drying effect of the Monascus red pigment and, at the same time, improving the thermal stability of the Monascus red pigment.

[0052] Combining Example 6 with Example 8 and the test data in Table 1-3, it can be seen that the preferred maltodextrin is maltodextrin with a DE value of 16-20. The maltodextrin within this DE value range has a shorter molecular chain, a lower degree of polymerization, and good solubility and dispersibility. It can improve the drying effect and product uniformity of Monascus red pigment while improving the water solubility rate and quality stability of Monascus red pigment.

[0053] Combining Example 6 and Example 9 and the test data in Table 1-3, it can be seen that when guar gum is used instead of gum arabic, the drying effect, product uniformity, water solubility rate and thermal stability of Monascus red pigment are all reduced, indicating that maltodextrin, gum arabic and sodium alginate can synergistically improve the drying effect, product uniformity, water solubility rate and thermal stability of Monascus red.

[0054] Combining Example 6 with Example 10 and the test data in Tables 1-3, it can be seen that in the sodium alginate aqueous solution with a mass concentration of 2%, the molecular weight of sodium alginate is preferably in the range of 50,000-100,000, which is beneficial to improving the drying effect and product uniformity of the monascus red pigment, and is beneficial to obtaining a monascus red pigment with fast water solubility and stable quality.

[0055] The dehydration time of Monascus red pigment at different temperatures in Example 11 is different from that in Example 6, but the total dehydration time remains the same. Combined with the test data in Tables 1-3, it can be seen that freeze-drying the Monascus red pigment using the freeze-drying step claimed in the present application is more conducive to improving the product uniformity, drying efficiency and thermal stability of the Monascus red pigment.

[0056] This specific implementation manner is merely an explanation of the present application and is not a limitation of the present application. After reading this specification, those skilled in the art may make non-creative modifications to the specific implementation manner as needed, but such modifications are protected by the patent law as long as they are within the scope of the claims of the present application.

Claims

1. A method for preparing red pigment of Monascus, characterized in that: The following steps are involved: S1. Inoculate the Monascus species into the basic culture medium to carry out batch expansion operations; S2. After the bacterial colonies in step S1 mature, centrifuge to obtain the solid residue, add 3-5 times the volume of alcohol with a concentration of more than 95%, stir, then separate the solid and liquid to obtain the liquid, and concentrate at 45°C-55°C to obtain a concentrated solution; S3, adding a protective agent to the concentrated solution of step S2, stirring at high speed, and cooling to solidify, wherein the protective agent is at least one of maltodextrin, gum arabic, and sodium alginate aqueous solution; S4, freeze-drying the product after cooling and solidification in step S3 to obtain Monascus red pigment.

2. A method for preparing a monascus red pigment according to claim 1, characterized in that: The protective agent includes maltodextrin, gum arabic and a sodium alginate aqueous solution with a mass concentration of 1.5%-2.5%, wherein the maltodextrin is used in an amount of 15%-25% by weight of the concentrated solution in step S2, the gum arabic is used in an amount of 4%-6% by weight of the concentrated solution in step S2, and the sodium alginate aqueous solution with a mass concentration of 1.5%-2.5% is used in an amount of 0.2%-0.3% by weight of the concentrated solution in step S2.

3. A method for preparing a monascus red pigment according to claim 2, characterized in that: The amount of maltodextrin used is 20% of the weight of the concentrated solution in step S2, the amount of gum arabic used is 5% of the weight of the concentrated solution in step S2, and the amount of the sodium alginate aqueous solution with a mass concentration of 1.5%-2.5% used is 0.25% of the weight of the concentrated solution in step S2.

4. A method for preparing a monascus red pigment according to any one of claims 1 to 3, characterized in that: The DE value of the maltodextrin is 16-20.

5. A method for preparing a monascus red pigment according to any one of claims 1 to 3, characterized in that: The molecular weight of the gum arabic is 220,000-300,000.

6. A method for preparing a monascus red pigment according to any one of claims 1 to 3, characterized in that: In the sodium alginate aqueous solution with a mass concentration of 1.5%-2.5%, the molecular weight of sodium alginate is 50,000-100,000.

7. A method for preparing a monascus red pigment according to any one of claims 1 to 3, characterized in that: In step S3, the rotation speed of high-speed stirring is 10000r / min-15000r / min.

8. A method for preparing a monascus red pigment according to any one of claims 1 to 3, characterized in that: In step S3, the curing temperature is (-38°C) - (-45°C).

9. A method for preparing a monascus red pigment according to any one of claims 1 to 3, characterized in that: In step S4, the freeze drying comprises the following steps: S41. Dehydrate for 1-2h in an environment with a temperature of -25℃~-20℃ and a vacuum degree of 5Pa-10Pa; S42, dehydrate for 1-2h in an environment with a temperature of -15℃~-10℃ and a vacuum degree of 5Pa-10Pa; S43, dehydrate for 2-4 hours in an environment with a temperature of -6°C to 0°C and a vacuum degree of 5Pa-10Pa; S44, dehydrate for 2-4h in an environment with a temperature of 1℃~5℃ and a vacuum degree of 5Pa-10Pa; S45, dehydrate for 4-6 hours in an environment with a temperature of 6℃~10℃ and a vacuum degree of 5Pa-10Pa; S46, dehydrate for 1-2h in an environment with a temperature of 10℃~15℃ and a vacuum degree of 5Pa-10Pa; S47, dehydrate for 1-2h in an environment with a temperature of 20℃~25℃ and a vacuum degree of 5Pa-10Pa; S48. Dehydrate for 6-8 hours in an environment with a temperature of 30℃~35℃ and a vacuum degree of 5Pa-10Pa.

10. A red pigment of Monascus, characterized in that: The method is prepared by the method for preparing the monascus red pigment according to any one of claims 1 to 9.

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