Antibacterial and antioxidant monascus yellow pigment as well as preparation method and application thereof

Abstract

The invention discloses an antibacterial and antioxidant monascus yellow pigment as well as a preparation method and application thereof. The preparation method comprises the following steps: reacting monascus yellow pigment with tannic acid in a solution state, carrying out solid-liquid separation on the obtained product, washing to remove uncombined pigment, and drying the obtained solid to obtain the antibacterial and antioxidant monascus yellow pigment. The preparation method is simple in process, mild in reaction condition, low in cost and suitable for large-scale production; the obtained anti-bacterial and anti-oxidation monascus yellow pigment has the characteristics of safety, anti-bacterial and anti-corrosion effects, high stability, bright color and the like, and can be popularized and applied as a food additive in the food industry.

Description

Technical Field

[0001] The present invention belongs to the field of food additives, and particularly relates to an antibacterial and antioxidant Monascus yellow pigment, a preparation method thereof, and an application thereof. Background Art

[0002] Monascus pigment is a secondary metabolite produced by the fermentation of Monascus mold, and its molecular structure is a polyketone structure. According to the secretion characteristics during the fermentation of Monascus, it can be divided into extracellular pigments and intracellular pigments. Among them, the intracellular pigments are mainly alcohol-soluble, while the extracellular pigments have better water solubility. In addition, according to their colors, they are mainly divided into three categories: red, orange, and yellow. Among them, the water-soluble yellow pigment has a soft and attractive color, can well improve the aesthetics of food, promote consumers' appetite, and enhance consumers' desire to purchase. However, the water-soluble yellow pigment produced by fermentation has problems such as poor stability, darker color, and poor dyeing effect. In addition, due to its poor antibacterial activity, the food is prone to spoilage after dyeing and is difficult to be applied to food coloring.

[0003] Studies have shown that chemical modification (Liu L, et al. Sulfonation of Monascus pigments to produce water-soluble yellow pigments. Dyes and Pigments, 2020: 173, 107965) and encapsulating materials (Huang Z, et al. Preparing bright Monascus yellow pigments by loading quercetin-Sn(II)-albumin–chitosan: Enhanced stability and bioactivity. Food Hydrocolloids, 2023: 142, 108776.) can be used to improve the biological activity and physicochemical stability of pigments. However, these methods still face many challenges such as complex preparation processes, high costs, and safety issues.

[0004] Therefore, there is an urgent need to develop a green preparation method for improving the antibacterial activity and stability of natural Monascus yellow pigment to promote the application of natural Monascus yellow pigment in the food industry. Summary of the Invention

[0005] The primary object of the present invention is to overcome the disadvantages and deficiencies of the prior art and provide a preparation method for an antibacterial and antioxidant Monascus yellow pigment.

[0006] Another object of the present invention is to provide an antibacterial and antioxidant Monascus yellow pigment obtained by the above preparation method.

[0007] Another object of the present invention is to provide the application of the above antibacterial and antioxidant monascus yellow pigment.

[0008] The object of the present invention is achieved by the following technical solutions: A preparation method of an antibacterial and antioxidant monascus yellow pigment, comprising the following steps: (1) Dissolve the monascus yellow pigment sufficiently with a solvent to obtain a monascus yellow pigment solution; (2) Add tannic acid to the monascus yellow pigment solution, mix evenly, and heat to obtain a monascus yellow pigment - tannic acid complex suspension; (3) Perform solid - liquid separation on the monascus yellow pigment - tannic acid complex suspension to obtain a monascus yellow pigment - tannic acid complex; (4) Wash the precipitate of the monascus yellow pigment - tannic acid complex repeatedly with a solvent to obtain a pure complex precipitate; (5) Freeze - dry the complex precipitate obtained in step (4) to obtain an antibacterial and antioxidant monascus yellow pigment.

[0009] The monascus yellow pigment described in step (1) is a natural monascus yellow pigment; more preferably a water - soluble natural monascus yellow pigment.

[0010] The solvents described in steps (1) and (4) are preferably citric acid - sodium citrate buffer solution or water.

[0011] The solvents described in steps (1) and (4) are preferably solvents with a pH of 4 - 7; more preferably a solvent with a pH of 7.

[0012] The concentration of the monascus yellow pigment solution described in step (1) is 0.5% - 1.5% by mass percentage; more preferably 1% by mass percentage.

[0013] The tannic acid described in step (2) is hydrolyzed tannic acid.

[0014] The tannic acid and the monascus yellow pigment described in step (2) are preferably proportioned by a mass ratio of 1:1 - 1:10; more preferably proportioned by a mass ratio of 1:5.

[0015] The rotation speed of the mixing described in step (2) is preferably 400 - 800 rpm; more preferably 600 rpm.

[0016] The heating method described in step (2) is preferably water - bath heating.

[0017] The heating temperature described in step (2) is preferably 30 - 50 °C; more preferably 35 °C.

[0018] The heating time described in step (2) is preferably 5 - 15 minutes; more preferably 10 minutes.

[0019] The solid-liquid separation method described in step (3) is preferably centrifugation.

[0020] The rotation speed of the centrifugation is preferably 8000 - 12000 rpm; more preferably 10000 rpm.

[0021] The time of the centrifugation is preferably 5 - 15 minutes; more preferably 10 minutes.

[0022] The number of washing times described in step (4) is preferably 2 - 3 times; more preferably 3 times.

[0023] The pre-freezing temperature of the freeze-drying described in step (5) is preferably -40°C to -80°C; more preferably -80°C.

[0024] The shelf temperature of the freeze-drying described in step (5) is preferably -30°C to -50°C; more preferably -45°C.

[0025] An antibacterial and antioxidant monascus yellow pigment is obtained by the above preparation method.

[0026] The above antibacterial and antioxidant monascus yellow pigment has the characteristics of safety, antibacterial and antiseptic efficacy, antioxidant activity, high stability, bright color, etc., and can be promoted and applied as a food additive in the food industry.

[0027] The present invention has the following advantages and effects compared with the prior art: (1) The monascus yellow pigment - tannic acid complex prepared by the present invention is characterized in that the phenolic hydroxyl group of tannic acid is used to spontaneously combine with the flavonoid structure of the yellow pigment through hydrogen bonding and π-π stacking co-coloring action to form a new pigment structure, improve the color of the monascus yellow pigment, and endow it with excellent antioxidant activity and antibacterial and antiseptic properties, overcoming the application problems of natural monascus yellow pigment such as dull color, unsatisfactory stability and low activity; at the same time, the use of preservatives is eliminated, which is an advantage that other commercial pigments do not have.

[0028] (2) The antibacterial and antioxidant monascus yellow pigment prepared by the present invention has a composite structure formed by conjugate binding, and can still maintain a stable pigment structure and color value under the stress of various adverse environments.

[0029] (3) The composite pigment powder prepared by the present invention is evenly dispersed, not easy to get damp and caked, and is convenient for transportation, storage and application.

[0030] (4) The preparation method provided by the present invention has a simple process, mild reaction conditions, the optimal pH is neutral, low cost, and is suitable for large-scale production; the raw materials and reagents for preparation are all food-grade, which is greener and safer than the chemical modification process and avoids the question of its safety. Description of the Drawings

[0031] Figure 1 Detection result graph of the pigment binding rate of antibacterial and antioxidant monascus yellow pigment prepared at different pH values.

[0032] Figure 2 Ultraviolet full-wavelength scanning spectrum graph of antibacterial and antioxidant monascus yellow pigment.

[0033] Figure 3 Scanning electron microscope images of monascus yellow pigment, tannic acid, and antibacterial and antioxidant monascus yellow pigment prepared in Examples 3-5.

[0034] Figure 4 Graph of the color performance and chromaticity analysis results of the powder and solution of antibacterial and antioxidant monascus yellow pigment; among them, A is the physical picture, and B is the color difference analysis graph of the pigment solution.

[0035] Figure 5 Graph of the stability analysis results of antibacterial and antioxidant monascus yellow pigment under different environmental stresses; among them, A is the color value retention rate under ascorbic acid treatment conditions, B is the color value retention rate under heat treatment conditions, C is the color value retention rate under light treatment conditions, and D is the color value retention rate under light-shielding treatment conditions.

[0036] Figure 6 Graph of the test results of the dyeing and anti-corrosion application of antibacterial and antioxidant monascus yellow pigment; among them, A is the result of the dye uptake rate of the pigment, and B is the result of the anti-corrosion application. Specific embodiments

[0037] The present invention will be further described in detail below in conjunction with the embodiments and the accompanying drawings, but the embodiments of the present invention are not limited thereto.

[0038] (1) Preparation of natural monascus yellow pigment: Monascus Monascus ruber WQ 15, with the preservation number of CGMCC No. 10910, was preserved on July 2, 2015 at the China General Microbiological Culture Collection Center of the Institute of Microbiology, Chinese Academy of Sciences, located at No. 3, Yard 1, Beichen West Road, Chaoyang District, Beijing, and has been disclosed in Patent 201510449543.6.

[0039] Monascus culture medium: PDA medium: Potato glucose 200 g / L, glucose 20 g / L, agar 15 - 20 g / L, made up to volume with distilled water, natural pH, sterilized at 121 °C for 20 min.

[0040] Seed medium: Glucose 20 g / L, yeast extract powder 3 g / L, fish meal peptone 10 g / L, potassium dihydrogen phosphate 4 g / L, potassium chloride 0.5 g / L, ferrous sulfate heptahydrate 0.01 g / L, made up to volume with distilled water, natural pH, sterilized at 121 °C for 20 min.

[0041] Fermentation medium: glucose 150 g / L, sodium nitrate 5 g / L, ammonium sulfate 5 g / L, potassium dihydrogen phosphate 5 g / L, potassium chloride 0.5 g / L, magnesium sulfate heptahydrate 0.5 g / L, ferric sulfate heptahydrate 0.01 g / L, zinc sulfate heptahydrate 0.01 g / L, manganese sulfate monohydrate 0.03 g / L, made up to volume with distilled water, natural pH, sterilized at 121 °C for 20 min.

[0042] Monascus culture: Strain activation: Take out the strain stored in a glycerol tube at -80 °C, thaw it at room temperature and inoculate it into the seed medium, culture it on a shaker at 30 °C and 180 rpm for 24 hr for activation. After activation, streak it on a PDA medium and culture it in an incubator at 30 °C for 8 d. The cultured seed plate is stored in a 4 °C refrigerator and used within 14 days.

[0043] Seed liquid culture: Scrape 8 Monascus single colonies (about 1 cm in diameter) from the plate into a 250 mL Erlenmeyer flask containing 50 mL of seed liquid medium, and culture it on a shaker at 30 °C and 180 rpm for 24 hr.

[0044] Fermentation culture: Inoculate the cultured seed liquid into a 250 mL Erlenmeyer flask containing 50 mL of fermentation medium at an inoculation amount of 10% (v / v), and culture it on a shaker at 30 °C and 180 rpm for 8 d.

[0045] After fermentation is completed, collect all 50 mL of the fermentation broth, perform suction filtration using a cellulose ester mixed filter membrane with a pore size of 0.8 μm, and separate to obtain a fermentation filtrate which is a hydrophilic natural Monascus yellow pigment and is used in the preparation of antibacterial and antioxidant Monascus yellow pigment.

[0046] (2) Tannic acid was purchased from Shanghai Macklin Biochemical Co., Ltd.

[0047] Example 1 This example provides a method for preparing antibacterial and antioxidant Monascus yellow pigment: (1) Dissolve the natural Monascus yellow pigment in a pH 4, 0.1 M citric acid - sodium citrate buffer solution, and fully dissolve it to obtain a Monascus yellow pigment solution with a mass concentration of 1%.

[0048] (2) Add tannic acid to the Monascus yellow pigment solution obtained in step (1), control the mass ratio of the yellow pigment to tannic acid to be 1:1, the mixing speed to be 600 rpm, the water bath temperature to be 35 °C, and the reaction time to be 10 minutes to obtain a Monascus yellow pigment - tannic acid complex suspension.

[0049] (3) Centrifuge the Monascus yellow pigment - tannic acid complex suspension prepared in step (2) at 10000 rpm for 10 minutes to obtain a Monascus yellow pigment - tannic acid complex precipitate.

[0050] (4) Wash the Monascus yellow pigment - tannic acid complex precipitate prepared in step (3) three times repeatedly with a citric acid - sodium citrate buffer solution with a pH of 4.

[0051] (5) Pre - freeze the Monascus yellow pigment - tannic acid complex precipitate prepared in step (4) at - 80 °C and then freeze - dry it at - 45 °C to obtain the antibacterial and antioxidant Monascus yellow pigment.

[0052] Example 2 This example provides a preparation method of antibacterial and antioxidant Monascus yellow pigment: (1) Dissolve natural Monascus yellow pigment in a citric acid - sodium citrate buffer solution with a pH of 6 and a concentration of 0.1 M, and dissolve it fully to obtain a Monascus yellow pigment solution with a mass concentration of 1%.

[0053] (2) Add tannic acid to the Monascus yellow pigment solution obtained in step (1), control the mass ratio of the yellow pigment to tannic acid to be 1:1, the mixing speed to be 600 rpm, the water bath temperature to be 35 °C, and the reaction time to be 10 minutes to obtain a Monascus yellow pigment - tannic acid complex suspension.

[0054] (3) Centrifuge the Monascus yellow pigment - tannic acid complex suspension prepared in step (2) at 10000 rpm for 10 minutes to obtain a Monascus yellow pigment - tannic acid complex precipitate.

[0055] (4) Wash the Monascus yellow pigment - tannic acid complex precipitate prepared in step (3) three times repeatedly with a citric acid - sodium citrate buffer solution with a pH of 6.

[0056] (5) Pre - freeze the Monascus yellow pigment - tannic acid complex precipitate prepared in step (4) at - 80 °C and then freeze - dry it at - 45 °C to obtain the antibacterial and antioxidant Monascus yellow pigment.

[0057] Example 3 This example provides a preparation method of antibacterial and antioxidant Monascus yellow pigment: (1) Dissolve natural Monascus yellow pigment in deionized water with a pH of 7.0, and dissolve it fully to obtain a Monascus yellow pigment solution with a mass concentration of 1%.

[0058] (2) Add tannic acid to the Monascus yellow pigment solution obtained in step (1), control the mass ratio of the yellow pigment to tannic acid to be 1:1, the mixing speed to be 600 rpm, the water bath temperature to be 35 °C, and the reaction time to be 10 minutes to obtain a Monascus yellow pigment - tannic acid complex suspension.

[0059] (3) Centrifuge the Monascus yellow pigment - tannic acid complex suspension prepared in step (2) at 10000 rpm for 10 minutes to obtain a Monascus yellow pigment - tannic acid complex precipitate.

[0060] (4) Wash the monascus yellow pigment - tannic acid complex precipitate prepared in step (3) three times repeatedly with deionized water at pH 7.0.

[0061] (5) Pre - freeze the monascus yellow pigment - tannic acid complex precipitate prepared in step (4) at - 80 °C and freeze - dry it at - 45 °C to obtain antibacterial and antioxidant monascus yellow pigment.

[0062] Example 4 This example provides a method for preparing antibacterial and antioxidant monascus yellow pigment: (1) Dissolve natural monascus yellow pigment in deionized water at pH 7.0 and dissolve it fully to obtain a monascus yellow pigment solution with a mass concentration of 1%.

[0063] (2) Add tannic acid to the monascus yellow pigment solution obtained in step (1), control the mass ratio of yellow pigment to tannic acid to be 5:1, the mixing speed to be 600 rpm, the water - bath temperature to be 35 °C, and the reaction time to be 10 minutes to obtain a monascus yellow pigment - tannic acid complex suspension.

[0064] (3) Centrifuge the monascus yellow pigment - tannic acid complex suspension prepared in step (2) at 10000 rpm for 10 minutes to obtain a monascus yellow pigment - tannic acid complex precipitate.

[0065] (4) Wash the monascus yellow pigment - tannic acid complex precipitate prepared in step (3) three times repeatedly with deionized water at pH 7.0.

[0066] (5) Pre - freeze the monascus yellow pigment - tannic acid complex precipitate prepared in step (4) at - 80 °C and freeze - dry it at - 45 °C to obtain antibacterial and antioxidant monascus yellow pigment.

[0067] Example 5 This example provides a method for preparing antibacterial and antioxidant monascus yellow pigment: (1) Dissolve natural monascus yellow pigment in deionized water at pH 7.0 and dissolve it fully to obtain a monascus yellow pigment solution with a mass concentration of 1%.

[0068] (2) Add tannic acid to the monascus yellow pigment solution obtained in step (1), control the mass ratio of yellow pigment to tannic acid to be 10:1, the mixing speed to be 600 rpm, the water - bath temperature to be 35 °C, and the reaction time to be 10 minutes to obtain a monascus yellow pigment - tannic acid complex suspension.

[0069] (3) Centrifuge the monascus yellow pigment - tannic acid complex suspension prepared in step (2) at 10000 rpm for 10 minutes to obtain a monascus yellow pigment - tannic acid complex precipitate.

[0070] (4) Wash the monascus yellow pigment - tannic acid complex precipitate obtained in step (3) three times repeatedly with deionized water having a pH of 7.0.

[0071] (5) Pre - freeze the monascus yellow pigment - tannic acid complex precipitate obtained in step (4) at - 80 °C and then freeze - dry it at - 45 °C to obtain the antibacterial and antioxidant monascus yellow pigment.

[0072] Effect examples 1. Determination of physicochemical indexes: (1) Analysis of pigment binding rate: Take appropriate amounts of the pigment before binding and the pigment solution in the supernatant after binding, and use a UV - Vis spectrophotometer (UV - 2802S, Younik (Shanghai) Instruments Co., Ltd., China) to measure the UV characteristic absorption spectrum of the sample at 380 nm. Calculate the pigment binding rate using formula 1 - 1: (1 - 1); Where, MYPo is the color value of the initial unreacted monascus yellow pigment solution, and MYPu is the color value of the unbound monascus yellow pigment in the supernatant.

[0073] (2) UV characteristic absorption analysis: Weigh appropriate amounts of monascus yellow pigment, tannic acid, and the antibacterial and antioxidant monascus yellow pigment prepared in Examples 3 - 5, dissolve them in an ethanol solution with a volume fraction of 70%, and use a UV - Vis spectrophotometer (UV - 2802S, Younik (Shanghai) Instruments Co., Ltd., China) to measure the UV characteristic absorption spectrum of the sample.

[0074] (3) Surface microstructure analysis: Weigh appropriate amounts of monascus yellow pigment, tannic acid, and the antibacterial and antioxidant monascus yellow pigment prepared in Examples 3 - 5, and use a scanning electron microscope (Merlin, Zeiss, Germany) to analyze the surface microstructure of the sample.

[0075] (4) Chromaticity analysis: Weigh appropriate amounts of monascus yellow pigment and the antibacterial and antioxidant monascus yellow pigment prepared in Examples 3 - 5, dissolve them separately in an ethanol solution with a volume fraction of 70% to prepare pigment solutions with a color value concentration of about 1.0 AU / mL, and use a color difference meter (CR - 400, Konica, Minolta, Japan) to analyze the chromaticity of the freeze - dried powder and solution of the antibacterial and antioxidant monascus yellow pigment.

[0076] (5) Antibacterial activity analysis: Weigh appropriate amounts of monascus yellow pigment, tannic acid, and the antibacterial and antioxidant monascus yellow pigment prepared in Examples 3 - 5, and prepare solutions with different concentrations respectively, using the solvent (70% ethanol solution) as a blank control. Inoculate Staphylococcus aureus GDMCC No. 1.2442 (which can be purchased from the Guangdong Provincial Culture Collection Center of Microorganisms) into 50 mL of LB medium and culture it in a shaker at 37 °C and 180 rpm for 8 hours. The cultured bacterial solution is used as the bacterial stock solution. In the antibacterial experiment, mix 40 µL of the bacterial stock solution, 950 µL of LB medium, and 10 µL of the monascus yellow pigment solution, antibacterial and antioxidant monascus yellow pigment solution, or tannic acid solution with different concentrations in a shaking tube and culture it in a shaker at 37 °C and 180 rpm for 8 hours. After the culture, evenly coat the mixture on an LB agar plate and continue to culture for 16 hours. Subsequently, record the number of colony - forming units (CFU).

[0077] (6)DPPH scavenging rate analysis: Weigh appropriate amounts of monascus yellow pigment, tannic acid, and the antibacterial and antioxidant monascus yellow pigment prepared in Examples 3 - 5, and prepare solutions with different concentrations using 70% ethanol solution to obtain sample solutions. Mix 50 μL of the sample solution with 400 μL of DPPH - methanol solution (60 μM) and react for 30 minutes under dark conditions at 30 °C. Subsequently, measure its absorbance at 515 nm.

[0078] (7)Ascorbic acid stability analysis: Weigh appropriate amounts of monascus yellow pigment and the antibacterial and antioxidant monascus yellow pigment prepared in Examples 3 - 5, dissolve them in 70% ethanol solution by volume respectively, and prepare pigment solutions with a color value concentration of approximately 1.0 AU / mL. Add ascorbic acid and mix well, controlling the final concentration of ascorbic acid to be 0, 0.25, 0.5, and 1 mg / mL. Subsequently, store them in the dark at 30 °C. After 24 hours, use a UV - visible spectrophotometer to measure the change in color value and calculate the retention rate of the pigment.

[0079] (8)Thermal stability analysis: Weigh appropriate amounts of monascus yellow pigment and the antibacterial and antioxidant monascus yellow pigment prepared in Examples 3 - 5, dissolve them in 70% ethanol solution by volume respectively, and prepare pigment solutions with a color value concentration of approximately 1.0 AU / mL. Place them in a 90 °C water bath for 4 hours, take samples every hour, use a UV - visible spectrophotometer to measure the change in color value, and calculate the retention rate of the pigment.

[0080] (9)Light stability analysis: Weigh appropriate amounts of monascus yellow pigment and the antibacterial and antioxidant monascus yellow pigment prepared in Examples 3 to 5, dissolve them separately in an ethanol solution with a volume fraction of 70%, prepare pigment solutions with a color value concentration of approximately 1.0 AU / mL, place them in a light box with a light intensity of 5000 lx, and leave them at room temperature for 4 days. Sample every other day, use a UV-visible spectrophotometer to measure the change in color value, and calculate the retention rate of the pigment.

[0081] (10)Storage stability analysis: Weigh appropriate amounts of monascus yellow pigment and the antibacterial and antioxidant monascus yellow pigment prepared in Examples 3 to 5, dissolve them separately in an ethanol solution with a volume fraction of 70%, prepare pigment solutions with a color value concentration of approximately 1.0 AU / mL, place them in a dark environment, and leave them at room temperature for 4 days. Sample every other day, use a UV-visible spectrophotometer to measure the change in color value, and calculate the retention rate of the pigment.

[0082] (11)Detection of application effects: Weigh appropriate amounts of the antibacterial and antioxidant monascus yellow pigment prepared in Examples 3 to 5, dissolve them separately in an ethanol solution with a volume fraction of 70%, prepare pigment solutions with a color value concentration of approximately 1.0 AU / mL, add 4 g of rice with uniform size, dye for 2 hours at 25°C, take out and record the dyeing situation, use a UV-visible spectrophotometer to measure the change in color value, and calculate the dye uptake rate of the pigment. Place the dyed rice in the air and culture it at room temperature for 5 days, and photograph and record the situation on the first day and the fifth day. Set monascus yellow pigment as the control.

[0083] 2. Detection results: (1)The detection results of the pigment binding rate of the antibacterial and antioxidant monascus yellow pigment prepared at different pH values are as Figure 1 shown: The binding rates of the antibacterial and antioxidant monascus yellow pigment prepared in Examples 1 to 3 are 31.03%, 33.43%, and 37.29% respectively, indicating that the closer the pH is to neutral, the higher the pigment binding rate.

[0084] (2)The UV characteristic absorption spectra are as Figure 2 shown: The characteristic absorption wavelength of natural monascus yellow pigment is at 380 nm, the characteristic coefficient wavelength of tannic acid is at 276 nm, and the antibacterial and antioxidant monascus yellow pigment prepared in Examples 3 to 5 has characteristic absorption peaks at both 380 nm and 276 nm.

[0085] (3)The scanning electron microscope images of the surface microstructure are as Figure 3 shown: The surface structure of monascus yellow pigment is rough spheres with irregular shapes attached; tannic acid is spherical particles with a smooth surface; in contrast, the antibacterial and antioxidant monascus yellow pigment (Examples 3 to 5) formed by reaction complexation resulting in molecular aggregation is a rough and irregular block structure with irregular small holes.

[0086] (4)The results of appearance and chromaticity analysis are as Figure 4 shown: As shown by A in Figure 4 , the natural monascus yellow pigment powder is prone to moisture absorption and caking, while the antibacterial and antioxidant monascus yellow pigment powders prepared in Examples 3-5 are evenly dispersed, not easily affected by moisture, and convenient for transportation and application; as shown by B in Figure 4 , the C* value of the antibacterial and antioxidant monascus yellow pigment solutions prepared in Examples 3-5 is higher, and the color is more saturated and vivid.

[0087] (5)The test results of antibacterial activity and antioxidant properties are shown in Table 1: Table 1

[0088] The results in Table 1 show that the antibacterial activity of the bright antibacterial monascus yellow pigment prepared in Examples 3-5 is greatly enhanced compared with the natural monascus yellow pigment. High antibacterial activity helps to inhibit bacteria and prevent spoilage of dyed foods. In addition, the IC 50 of DPPH radical scavenging in Example 4 is 57.710 μg / mL, which is lower than that of tannic acid (69.343 μg / mL), indicating that it achieves the effect of "1+1>2".

[0089] (6)The test results of physicochemical stability are as Figure 5 shown: Ascorbic acid is a commonly used food additive with a fresh-keeping effect. When ascorbic acid coexists with natural pigments during processing and storage, it will cause the degradation of natural pigments. This degradation is mainly due to the oxidation of ascorbic acid autoxidation products, especially the degradation effect of hydrogen peroxide (H2O2) on pigments. As shown by A in Figure 5 , under the treatment of different concentrations of ascorbic acid (0, 0.25, 0.5, and 1.0 mg / mL), after 24 hours, the retention rates of monascus yellow pigment and the antibacterial and antioxidant monascus yellow pigment prepared in Examples 3-5 are both higher than 84%. This shows that monascus yellow pigment and antibacterial and antioxidant monascus yellow pigment have excellent tolerance to ascorbic acid. The processing and sterilization of foods are generally carried out under heat treatment at 90 °C. As shown by B in Figure 5 , after 4 hours of heat treatment, the pigment retention rates of the antibacterial and antioxidant monascus yellow pigment prepared in Examples 3-5 are 31.47%, 37.99%, and 34.20% respectively, while the pigment retention rate of monascus yellow pigment is only 24.19%. It can be seen that Examples 3-5 all show better thermal stability than natural monascus yellow pigment. As shown in Figure 5As shown in C of [reference], after 4 days of light treatment with a light intensity of 5000 lx, the retention rate of the monascus yellow pigment solution was 40.80%, while the color retention rates of the antibacterial and antioxidant monascus yellow pigments prepared in Examples 3 to 5 were 60.32%, 53.20% and 55.16% respectively, which were significantly higher than that of the monascus yellow pigment solution. In addition, the storage and transportation of pigments are often carried out in a light-proof environment, such as Figure 5 shown in D of [reference], after 4 days of light-proof treatment, the pigment retention rates of Examples 3 to 5 were 87.70%, 75.11% and 76.61% respectively, which were significantly higher than the retention rate of 69.46% of the monascus yellow pigment.

[0090] (7)The effects of the application in dyeing and anti-corrosion are as Figure 6 shown: As Figure 6 shown in A of [reference], the dyeing rates of Examples 3 to 5 were 23.45%, 24.62% and 22.83% respectively, which were significantly higher than the dyeing rate of 17.23% of the monascus yellow pigment. In addition, as Figure 6 shown in B of [reference], the rice dyed with Examples 3 to 5 was still not infected and deteriorated by microorganisms after 5 days of treatment at room temperature, while the rice dyed with the monascus yellow pigment and the blank control group showed visible signs of decay and deterioration after 5 days of treatment, indicating that the prepared antibacterial and antioxidant monascus yellow pigment has the effect of dyeing and anti-corrosion.

[0091] The above embodiments are the preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications made without departing from the spirit and principle of the present invention shall be equivalent replacement methods and shall be included in the protection scope of the present invention.

Claims

1. A method for preparing an antibacterial and antioxidant monascus yellow pigment, characterized in that The steps include: (1) Fully dissolving the monascus yellow pigment in a solvent to obtain a monascus yellow pigment solution; (2) adding tannic acid to the monascus yellow pigment solution, mixing evenly, and heating to obtain a monascus yellow pigment-tannic acid complex suspension; (3) performing solid-liquid separation on the monascus yellow pigment-tannic acid complex suspension to obtain the monascus yellow pigment-tannic acid complex; (4) repeatedly washing the monascus yellow pigment-tannic acid complex precipitate with a solvent to obtain a pure complex precipitate; (5) freeze-drying the complex precipitate obtained in step (4) to obtain antibacterial and antioxidant monascus yellow pigment.

2. The method for preparing the antibacterial and antioxidant monascus yellow pigment according to claim 1, characterized in that: The monascus yellow pigment in step (1) is natural monascus yellow pigment; The tannic acid described in step (2) is hydrolyzed tannic acid; The tannic acid and the monascus yellow pigment in step (2) are mixed in a mass ratio of 1:1 to 1:

10.

3. The method for preparing the antibacterial and antioxidant monascus yellow pigment according to claim 2, characterized in that: The monascus yellow pigment described in step (1) is a water-soluble natural monascus yellow pigment; The tannic acid and the monascus yellow pigment in step (2) are mixed in a mass ratio of 1:

5.

4. The method for preparing the antibacterial and antioxidant Monascus yellow pigment according to claim 1, characterized in that: The solvent in step (1) and step (4) is citric acid-sodium citrate buffer or water; The solvent in step (1) and step (4) is a solvent with a pH of 4 to 7; The concentration of the monascus yellow pigment solution in step (1) is 0.5% to 1.5% by mass.

5. The method for preparing the antibacterial and antioxidant Monascus yellow pigment according to claim 4, characterized in that: The solvent in step (1) and step (4) is a solvent with a pH of 7; The concentration of the monascus yellow pigment solution described in step (1) is 1% by mass.

6. The method for preparing the antibacterial and antioxidant Monascus yellow pigment according to claim 1, characterized in that: The mixing speed in step (2) is 400-800 rpm; The heating method in step (2) is water bath heating; The heating temperature in step (2) is 30-50°C; The heating time in step (2) is 5 to 15 minutes.

7. The method for preparing the antibacterial and antioxidant Monascus yellow pigment according to claim 1, characterized in that: The solid-liquid separation method in step (3) is centrifugation; The washing times in step (4) are 2 to 3 times; The pre-freezing temperature of freeze drying in step (5) is -40°C to -80°C; The freeze-drying plate temperature in step (5) is -30°C to -50°C.

8. The method for preparing the antibacterial and antioxidant Monascus yellow pigment according to claim 7, characterized in that: The centrifugal speed is 8000-12000 rpm; The centrifugal time is 5 to 15 minutes; The number of washing steps in step (4) is 3 times; The pre-freezing temperature of the freeze-drying in step (5) is -80°C; The freeze-drying plate temperature in step (5) is -45°C.

9. An antibacterial and antioxidant monascus yellow pigment, characterized in that: The method is obtained by the preparation method according to any one of claims 1 to 8.

10. Use of the antibacterial and antioxidant Monascus yellow pigment according to claim 9 in the preparation of food additives.

Images