Preparation method of steady-state monascus red pigment

Abstract

The invention relates to the technical field of monascus pigments, and discloses a preparation method of a steady-state monascus red pigment, which comprises the following steps: taking a monascus pigment generated by solid or liquid fermentation monascus as a raw material, carrying out two-stage reaction on the monascus pigment and amino acid in an ethanol system, and then carrying out separation, concentration and other processes to obtain the steady-state monascus red pigment. And the oil-soluble and water-soluble monascus red pigment is prepared. The method has the advantages that the defects that in the traditional method for preparing the monascus red pigment through alkali treatment, the pigment is easily subjected to alkaline hydrolysis, the stability is reduced, the color becomes yellow and the like are overcome, and meanwhile the method has the advantages of being mild in preparation condition and high in process operability. Compared with the monascus red pigment prepared by the traditional process, the monascus red pigment prepared by the method has the advantages that the color value is high, and the stability is remarkably improved.

Description

Technical Field

[0001] The present invention relates to the technical field of monascus pigments, and in particular to a method for preparing stabilized monascus red pigment. Background Art

[0002] Monascus red pigment, a polyketide secondary metabolite produced by the metabolism of Monascus purpureus, has a long history of application and offers the multiple advantages of being "natural, safe, nutritious, and multifunctional." With the growing trend toward naturalization and health in the food industry, Monascus red pigment has become a key component of the food colorant market. In particular, with the continuous improvement of living standards and consumer awareness of food safety, food pigments, as a key component of food additives, have attracted increasing attention. As a natural food colorant, Monascus red pigment holds broad application prospects.

[0003] Currently, the industrial production of red yeast rice pigment generally utilizes an ethanol-water solvent system, extracting the fermented red yeast mycelium under alkaline conditions, either in liquid or solid form. To improve the extraction yield and water solubility of the red yeast rice pigment, a certain amount of protein is often added to the extraction system. The resulting red yeast rice pigment exhibits good water solubility. Depending on the fermentation and extraction process, the resulting red yeast rice pigment typically exhibits a maximum absorption peak in ethanol of approximately λmax 490±10nm. This pigment is widely used for coloring meat products, beverages, condiments, and other products.

[0004] However, this process also faces the following challenges: (1) The red pigment produced by this process is insoluble in non-polar solvents such as oil, which limits its application in oil-based foods; (2) The red pigment produced by this process is prone to fading under conditions such as heating or light, affecting the commercial value of the product.

[0005] In order to develop oil-soluble red yeast rice pigment and improve the stability of red yeast rice pigment, scientific researchers have done a lot of work. The invention patent (application number 201910557316.3) discloses a method for preparing oil-soluble red yeast rice pigment. The invention adopts high-pressure jet homogenization and multiple high-efficiency cutting and grinding methods, and combines a new red yeast rice pigment post-processing process to make the red yeast rice particles nano-scale refined to achieve oil-soluble transformation, which can be stably stored in the oil phase system. However, it is still based on the traditional preparation of water-soluble red yeast rice pigment, and further emulsification technology is used to realize the conversion of red yeast rice pigment from water-soluble to oil-soluble. Li Dandan (Li Dandan. Analysis of Monascus Pigment Components and Preparation and Characterization of Its Oil-Soluble Derivatives [D]. Fujian Agriculture and Forestry University, 2015) used defatted acidified monascus pigment and dicyclohexylcarbodiimide as raw materials, and used dichloromethane / N,N-dimethylformamide (20 / 3) as solvent. After reacting at 35°C for 24 hours, the crude product was filtered, washed with water, and dried. This crude product was then subjected to Soxhlet extraction with petroleum ether / ethyl acetate (3 / 1) as solvent to obtain the oil-soluble primary monascus pigment. Solubility tests showed that the primary oil-soluble monascus pigment was soluble in low-polarity solvents such as carbon tetrachloride and petroleum ether, as well as edible oil. However, the reactant system used in this method poses certain risks to food safety. A People's Republic of China invention patent (application number 202410530234.0) discloses a novel method for constructing nanoparticles to enhance the stability of red yeast rice pigment. The nanoparticles comprise: red yeast rice pigment; a protein coating the outer layer of the red yeast rice pigment; and a pectin-rutin conjugate coated on the outer layer of the protein layer. These nanoparticles can significantly enhance the stability of water-soluble red yeast rice pigment. This invention enhances the stability of water-soluble red yeast rice pigment through encapsulation technology and does not address the stability of oil-soluble red yeast rice pigment. This system poses a risk of instability under continuous heating.

[0006] Therefore, it is particularly important to develop a preparation method that can improve the solubility of red yeast rice pigment and significantly increase the stability of red yeast rice pigment. Summary of the Invention

[0007] In view of this, the present invention proposes a method for preparing stabilized red yeast rice pigment, aiming to solve the problem of poor solubility and stability of red yeast rice pigment in the current technology.

[0008] On the one hand, the present invention provides a method for preparing a stabilized red pigment of Monascus japonica, comprising the following steps:

[0009] S1: The raw material is monascus pigment produced by solid or liquid fermentation of Monascus purpureus, and is recorded as monascus pigment A;

[0010] S2: mixing monascus pigment A and amino acid in a ratio of 1:(0.1-2), dissolving the mixed ingredients in a reaction medium, wherein the reaction medium is a 60%-95% ethanol-water solution, wherein the mass volume fraction of monascus pigment A in the reaction medium is 0.1-10%, which is recorded as the initial reaction system;

[0011] S3: reacting the primary reaction system at 40-100° C. for 5-200 min;

[0012] S4: After the reaction is completed, the mixture is concentrated under reduced pressure until no fraction is distilled out, and then anhydrous ethanol is added to the primary reaction system to dissolve it again to obtain a secondary reaction system;

[0013] S5: adding phosphorus pentoxide to the secondary reaction system to react while stirring;

[0014] S6: Preparation of oil-soluble red pigment:

[0015] Taking the secondary reaction system, performing solid-liquid separation to remove insoluble matter, then adding edible oil to the secondary reaction system, and performing reduced pressure concentration at a temperature of 30-50° C. and a vacuum degree controlled at -0.095 to -0.06 MPa, and concentrating until the residual solvent content is ≤5% w / w to obtain oil-soluble red yeast rice pigment;

[0016] Preparation of water-soluble red pigment:

[0017] The secondary reaction system is taken, solid-liquid separation is performed to remove insoluble matter, and then the secondary reaction system is directly concentrated under reduced pressure to a solid content of 5-20%, glyceride or sucrose ester is added to the secondary reaction system, heated and dispersed evenly, and the system is again concentrated under reduced pressure until no fraction is distilled out, and then starch, gum arabic and maltodextrin aqueous solution are added to the secondary reaction system, wherein the total mass fraction of starch, gum arabic and maltodextrin is 2-30%, and the mass ratio of starch, gum arabic and maltodextrin is 1: (0.1-2): (0.1:2), and after drying, water-soluble monascus red pigment is obtained.

[0018] Furthermore, the molecular structure of the monascus pigment A is the general formula (1) or the general formula (2);

[0019]

[0020] In the general formula (1) and the general formula (2), R represents a methyl group.

[0021] Furthermore, in step S4, the amount of anhydrous ethanol added is 10-300 times the mass of monascus pigment A.

[0022] Furthermore, in step S5, the mass ratio of the added amount of phosphorus pentoxide to the monascus pigment A is 1:(1-20).

[0023] Furthermore, in step S5, the reaction temperature is controlled at 40-95° C., and the reaction is heated under reflux for 0.5-4 h.

[0024] Furthermore, when preparing the water-soluble Monascus red pigment in step S6, the added amount of the glyceride or sucrose ester is 0.05-0.2 times the mass of Monascus pigment A.

[0025] On the other hand, the present invention also protects an oil-soluble monascus red pigment or a water-soluble monascus red pigment obtained by the preparation method of the above-mentioned stabilized monascus red pigment.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] (1) The advantage of the present invention is that it overcomes the defects of the traditional method of preparing red pigment by alkali treatment, which causes the pigment to be easily alkaline-lyzed, resulting in reduced stability and yellowing of the color. At the same time, it has mild preparation conditions and strong process operability.

[0028] (2) The method for preparing oil-soluble red yeast rice pigment of the present invention has mild production conditions, and the prepared red yeast rice pigment product has high color value, which is suitable for industrial application and promotion.

[0029] (3) The most significant advantage of the red yeast rice pigment prepared by the present invention over the red yeast rice pigment products prepared by the traditional industrial process is that the stability has been significantly improved, especially the application stability has been greatly improved. The heat stability test shows that the oil-soluble red yeast rice pigment prepared by the present invention maintains a pigment retention rate of more than 95% after being continuously heated at 95°C for 4 hours, and the problem of pigment migration to the aqueous phase does not occur. The water-soluble red yeast rice pigment prepared by the present invention maintains a pigment retention rate of more than 90% after being continuously heated at 95°C for 4 hours. The above characteristics are of great significance to the application and promotion of red yeast rice pigment.

[0030] (4) The oil-soluble red pigment prepared by the present invention can be applied to oil-medium products, and is particularly suitable for continuously heated oil-medium products, such as hot pot base, hot-processed foods, etc. The water-soluble red pigment prepared by the present invention has significant application effects in meat products and baked products. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Various other advantages and benefits will become apparent to those skilled in the art upon reading the detailed description of the preferred embodiment below. The accompanying drawings are for illustration purposes only and are not to be considered as limiting the present invention. The same reference symbols are used throughout the drawings to represent the same components. In the drawings:

[0032] Figure 1This is the UV-visible absorption spectrum of the raw materials in Example 1 of the present invention.

[0033] Figure 2 Spectra of the oil-soluble red monascus pigment and the water-soluble red monascus pigment in Example 1 of the present invention.

[0034] Figure 3 This is a graph showing the thermal stability test results of the oil-soluble monascus red pigment of an embodiment of the present invention.

[0035] Figure 4 This is a graph showing the thermal stability test results of the water-soluble monascus red pigment of an embodiment of the present invention. DETAILED DESCRIPTION

[0036] The following is a clear and complete description of the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of the present invention.

[0037] In response to the problems pointed out in the background technology, the embodiments of the present invention start from the red yeast rice pigment molecule itself and establish a new method for preparing oil-soluble red yeast rice pigment and water-soluble red yeast rice pigment suitable for industrial application through chemical derivatization and physical action. The solubility of red yeast rice pigment is improved from both the molecule itself and the carrier system, and the stability of red yeast rice pigment is greatly improved.

[0038] In response to the current industrial and technological status of red yeast rice pigments, which face poor oil solubility and stability in industrial production, the present invention provides a method for preparing an oil-soluble, stabilized red yeast rice pigment to overcome the problem of oil-soluble red yeast rice pigments being prone to water phase migration under continuous heating. This technical invention has practical significance for enriching the variety of red yeast rice pigment products, expanding the application range of red yeast rice pigments, and promoting the development of the red yeast rice pigment industry.

[0039] It should be noted that the total mass fraction of starch, gum arabic, and maltodextrin is 2-30%, and the mass ratio of starch, gum arabic, and maltodextrin is 1:(0.1-2):(0.1:2). In the following examples and test examples, the mass ratio of starch, gum arabic, and maltodextrin is 1:1:1, and the total mass fraction is 15%. The specific amount of added depends on the color value required for specific product production.

[0040] Example 1

[0041] (1) Raw material: The red pigment produced by liquid fermentation of Monascus purpureus is used as raw material, which is recorded as red pigment A. The spectrum of the raw material red pigment A in ethanol solution is as follows: Figure 1 shown.

[0042] (2) Monascus pigment A and tyrosine were mixed in a ratio of 1:1 and dissolved in a reaction medium. The reaction medium was an 80% ethanol-water solution, wherein the mass volume fraction of Monascus pigment A in the reaction medium was 5%, which was recorded as the initial reaction system.

[0043] (3) The initial reaction system obtained in step (2) was reacted at 60° C. for 30 min, with stirring or ultrasound-assisted reaction.

[0044] (4) After the reaction in step (3) is completed, the reaction system is concentrated under reduced pressure to remove the solvent until no fraction is distilled out, and then anhydrous ethanol is added to the system for redissolution to obtain a secondary reaction system, wherein the amount of anhydrous ethanol added is 100 times the mass of Monascus pigment A.

[0045] (5) Add phosphorus pentoxide to the secondary reaction system obtained in step (4), wherein the mass ratio of phosphorus pentoxide to monascus pigment A is 1:10. The reaction is carried out under continuous stirring, the reaction temperature is controlled at 60° C., and the reaction is refluxed for 1 hour.

[0046] (6) Preparation of oil-soluble red monascus pigment: Prepare the product based on the process of step (5). After the reaction of step (5) is completed, remove the insoluble matter in the reaction system by centrifugation or filtration. Then, add corn germ oil to the system in an amount of 20 times the mass of monascus pigment A. Then, concentrate under reduced pressure until no fraction flows out, thereby obtaining oil-soluble red monascus pigment.

[0047] (7) Preparation of water-soluble red monascus pigment: Prepare on the basis of step (5), after the reaction of step (5) is completed, remove the insoluble matter in the reaction system by centrifugation or filtration. Then, the reaction system is concentrated under reduced pressure to a solid content of 15%, and then sucrose ester is added to the system, and the amount of sucrose ester added is 1 / 10 of the mass of red monascus pigment A. Heat and disperse evenly, then reduce pressure and concentrate again until no fraction flows out, and then add starch, gum arabic, and maltodextrin aqueous solution in appropriate proportions to the system. Dry to obtain water-soluble red monascus pigment.

[0048] Example 2

[0049] (1) Raw materials: The monascus pigment produced by liquid fermentation of Monascus purpureus was used as the raw material, which was recorded as monascus pigment A. The raw material monascus pigment A was taken from the same batch of raw materials as in Example 1, so the spectrum is not shown here.

[0050] (2) Monascus pigment A and glycine were mixed in a ratio of 1:0.5 and dissolved in a reaction medium. The reaction medium was an 80% ethanol-water solution, wherein the mass volume fraction of Monascus pigment A in the reaction medium was 8%, which was recorded as the initial reaction system.

[0051] (3) The initial reaction system obtained in step (2) was reacted at 60° C. for 30 min, with stirring or ultrasound-assisted reaction.

[0052] (4) After the reaction in step (3) is completed, the reaction system is concentrated under reduced pressure to remove the solvent until no fraction is distilled out, and then anhydrous ethanol is added to the system for redissolution to obtain a secondary reaction system, wherein the amount of anhydrous ethanol added is 100 times the mass of Monascus pigment A.

[0053] (5) Add phosphorus pentoxide to the secondary reaction system obtained in step (4), wherein the mass ratio of phosphorus pentoxide to monascus pigment A is 1:10. The reaction is carried out under continuous stirring, the reaction temperature is controlled at 60° C., and the reaction is refluxed for 1 hour.

[0054] (6) Preparation of oil-soluble red monascus pigment: Prepare the product based on the process of step (5). After the reaction of step (5) is completed, remove the insoluble matter in the reaction system by centrifugation or filtration. Then, add corn germ oil to the system in an amount of 20 times the mass of monascus pigment A. Then, concentrate under reduced pressure until no fraction flows out, thereby obtaining oil-soluble red monascus pigment.

[0055] (7) Preparation of water-soluble red monascus pigment: Prepare on the basis of step (5), after the reaction of step (5) is completed, remove the insoluble matter in the reaction system by centrifugation or filtration. Then, the reaction system is concentrated under reduced pressure to a solid content of 15%, and then sucrose ester is added to the system, and the amount of sucrose ester added is 1 / 10 of the mass of red monascus pigment A. Heat and disperse evenly, then reduce pressure and concentrate again until no fraction flows out, and then add starch, gum arabic, and maltodextrin aqueous solution in appropriate proportions to the system. Dry to obtain water-soluble red monascus pigment.

[0056] Test Example 1

[0057] Spectral analysis of oil-soluble and water-soluble red pigments prepared in Example 1 of the present invention:

[0058] Weigh 0.05 g to 0.10 g of the oil-soluble red monascus pigment and the water-soluble red monascus pigment prepared in Example 1 of the present invention, fully dissolve them with anhydrous ethanol, and make the volume to 100 ml. Then dilute them a certain multiple, use anhydrous ethanol as a blank control, and perform wavelength scanning on the sample in the scanning range of 350 nm to 700 nm to obtain the spectra of the oil-soluble red monascus pigment and the water-soluble red monascus pigment prepared by the present invention, as shown in FIG. Figure 1 The results show that the maximum absorption wavelengths of the oil-soluble red pigment and the water-soluble red pigment prepared by the present invention in anhydrous ethanol solution are λ max 509nm, λ max506nm, which is about 20nm red-shifted compared with the red pigment prepared by traditional process.

[0059] Test Example 2

[0060] Thermal stability test of the oil-soluble red pigment prepared by the present invention:

[0061] Weigh the oil-soluble red pigment prepared in Example 1 of the present invention, fully dissolve it with corn germ oil, and dilute it appropriately to obtain a test sample for thermal stability. The sample was placed in a 95°C water bath and heated continuously for 4 hours. The absorbance value change of the sample at the maximum absorption wavelength (λmax) before and after heating was then measured, and the retention rate of the pigment was calculated to evaluate its stability. The test was repeated three times under parallel conditions and the average value was taken. The calculation formula for the pigment retention rate is as follows:

[0062] Pigment retention rate (%) = (absorbance of sample after heating A λmax / Absorbance of sample before heating A λmax )*100%

[0063] The results of the thermal stability test of oil-soluble red pigment are shown in Table 1. The spectrum of the pigment before and after heating is shown in Table 1. Figure 2 shown.

[0064] Table 1 Thermal stability test results of oil-soluble red pigment

[0065] <![CDATA[Absorbance value A before heating λmax > <![CDATA[Absorbance value A after heating λmax > Pigment retention rate (%) 0.512 0.496 96.88

[0066] The results of the thermal stability test show that the oil-soluble red yeast rice pigment prepared by the present invention maintains a pigment retention rate of 96.88% after continuous heating at 95°C for 4 hours, and has good thermal processing stability. It is particularly suitable for continuous heating product applications, such as hot pot ingredients, and coloring of cooked products.

[0067] Test Example 3: Oil-water two-phase migration stability test of the oil-soluble monascus red pigment prepared by the present invention during continuous heating.

[0068] Weigh the oil-soluble red pigment prepared in Example 1 of the present invention, fully dissolve it with corn germ oil, take 50 mL of the prepared oil-soluble red pigment-corn germ oil solution into a colorimetric tube, and then add 50 mL of distilled water to the colorimetric tube, mix thoroughly, and after the system is completely separated, take the aqueous phase solution of the lower layer and measure its λ max Place the colorimetric tube in a 100℃ water bath and heat continuously for 4 hours, then take out the lower aqueous solution and measure its absorbance at λ max By comparing the changes in absorbance before and after heating, the oil-water two-phase migration stability of oil-soluble red yeast rice pigment during continuous heating was evaluated. The migration rate of the pigment to the water phase was calculated. The results are as follows: Figure 3 As shown, the mobility calculation formula is as follows:

[0069] Pigment mobility (%) = (absorbance value of the heated aqueous phase A λmax -Absorbance value of water phase before heating A λmax ) / Absorbance of oil phase before heating A λmax *100%.

[0070] The results showed that during the continuous heating process, the migration rate of the oil-soluble red yeast rice pigment into the aqueous solution was less than 0.1%. No migration of the red yeast rice pigment from the oil phase to the aqueous phase was observed with the naked eye, and the aqueous solution remained colorless and transparent. This has significant application advantages compared to the traditional oil-soluble pigment prepared by emulsification encapsulation method.

[0071] Test Example 4 Thermal Stability Test of Water-Soluble Monascus Red Pigment Prepared by Example of the Present Invention

[0072] Weigh the oil-based red pigment prepared in Example 1 of the present invention, dissolve it in distilled water, and dilute it appropriately to obtain a test sample for thermal stability. Place the sample in a 95°C water bath and heat it for 4 hours. Then measure the λ value of the sample before and after heating. max The absorbance value change of the pigment was measured and the retention rate of the pigment was calculated to evaluate its stability. The test was repeated three times under parallel conditions and the average value was taken. The calculation formula of the pigment retention rate is as follows:

[0073] Pigment retention rate (%) = (absorbance of sample after heating A λmax / Absorbance of sample before heating A λmax )*100%.

[0074] The results of the thermal stability test of water-soluble red pigment are shown in Table 2. The spectrum of the pigment before and after heating is shown in Table 2. Figure 4 shown.

[0075] Table 2: Thermal stability test results of oil-soluble red pigment of the present invention

[0076] <![CDATA[Absorbance value A before heating λmax > <![CDATA[Absorbance value A after heating λmax > Pigment retention rate (%) 0.653 0.619 94.79

[0077] The results of the thermal stability test show that the water-soluble Monascus red pigment prepared by the present invention maintains a pigment retention rate of 94.79% after continuous heating at 95°C for 4 hours, and has good thermal processing stability. It is particularly suitable for continuous heating product applications, such as coloring cooked products.

[0078] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, ordinary technicians in the field should understand that the specific implementation methods of the present invention can still be modified or replaced by equivalents. Any modification or equivalent replacement that does not depart from the spirit and scope of the present invention should be covered by the scope of protection of the claims of the present invention.

Claims

1. A method for preparing a stabilized red pigment of Monascus koji, characterized in that: The following steps are involved: S1: The raw material is monascus pigment produced by solid or liquid fermentation of Monascus purpureus, and is recorded as monascus pigment A; S2: mixing monascus pigment A and amino acid in a ratio of 1:(0.1-2), dissolving the mixed ingredients in a reaction medium, wherein the reaction medium is a 60%-95% ethanol-water solution, wherein the mass volume fraction of monascus pigment A in the reaction medium is 0.1-10%, which is recorded as the initial reaction system; S3: reacting the primary reaction system at 40-100° C. for 5-200 min; S4: After the reaction is completed, the mixture is concentrated under reduced pressure until no fraction is distilled out, and then anhydrous ethanol is added to the primary reaction system to dissolve it again to obtain a secondary reaction system; S5: adding phosphorus pentoxide to the secondary reaction system to react while stirring; S6: Preparation of oil-soluble red pigment: Taking the secondary reaction system, performing solid-liquid separation to remove insoluble matter, then adding edible oil to the secondary reaction system, and performing reduced pressure concentration at a temperature of 30-50° C. and a vacuum degree controlled at -0.095 to -0.06 MPa, and concentrating until the residual solvent content is ≤5% w / w to obtain oil-soluble red yeast rice pigment; Preparation of water-soluble red pigment: The secondary reaction system is taken, solid-liquid separation is performed to remove insoluble matter, and then the secondary reaction system is directly concentrated under reduced pressure to a solid content of 5-20%, glyceride or sucrose ester is added to the secondary reaction system, heated and dispersed evenly, and the system is again concentrated under reduced pressure until no fraction is distilled out, and then starch, gum arabic and maltodextrin aqueous solution are added to the secondary reaction system, wherein the total mass fraction of starch, gum arabic and maltodextrin is 2-30%, and the mass ratio of starch, gum arabic and maltodextrin is 1: (0.1-2): (0.1:2), and after drying, water-soluble monascus red pigment is obtained.

2. The preparation method of the stabilized red yeast rice pigment according to claim 1, wherein The molecular structure of the monascus pigment A is the general formula (1) or the general formula (2); In the general formula (1) and the general formula (2), R represents a methyl group.

3. The preparation method of the stabilized red yeast rice pigment according to claim 1, wherein In step S4, the amount of anhydrous ethanol added is 10-300 times the mass of monascus pigment A.

4. The preparation method of the stabilized red yeast rice pigment according to claim 1, wherein The mass ratio of the added amount of phosphorus pentoxide to the monascus pigment A in step S5 is 1:(1-20).

5. The preparation method of the stabilized red yeast rice pigment according to claim 1, wherein In step S5, the reaction temperature is controlled at 40-95° C. and the mixture is heated under reflux for 0.5-4 h.

6. The preparation method of the stabilized red yeast rice pigment according to claim 1, wherein When preparing the water-soluble monascus red pigment in step S6, the added amount of the glyceride or sucrose ester is 0.05-0.2 times the mass of monascus pigment A.

7. A water-soluble red monascus pigment or oil-soluble red monascus pigment obtained according to the preparation method according to any one of claims 1 to 6.

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