Preparation method of gardenia blue pigment

Abstract

The invention discloses a preparation method of gardenia blue pigment. The preparation method comprises the following steps: (1) precipitating and removing impurities by copper sulfate: precipitating and removing impurities from column liquid after gardenia yellow is extracted by copper sulfate to obtain supernate; (2) oxidizing and decoloring by potassium permanganate and removing excessive copper ions: performing neutral oxidation on the supernate by potassium permanganate to obtain decolored supernate; (3) nanofiltration concentration and spray drying: carrying out alkaline nanofiltration concentration and spray drying on the decolorized supernatant to obtain a geniposide solid crude product; (4) extracting geniposide with propyl alcohol and recrystallizing: extracting the crude product with ethyl acetate and recrystallizing to obtain a fine geniposide product; (5) ethyl acetate two-phase acid hydrolysis: carrying out ethyl acetate two-phase acid hydrolysis and recrystallization on the refined product to obtain a genipin pure product; and (6) preparing a gardenia blue pigment pure product: reacting the genipin pure product with sodium isoleucine to obtain the gardenia blue pigment. The method is simple and easy to implement, convenient to operate, outstanding in product characteristics, easy in equipment type selection and matching, low in equipment investment, high in product additional value, good in economic benefit and capable of being mechanized.

Description

Technical Field

[0001] The present invention relates to the technical field of deep processing of gardenia, and more particularly to a method for preparing high-purity and high-color-value gardenia blue pigment by using the under-column liquid after extracting gardenia yellow pigment. Background Art

[0002] Gardenia jasminoides Ellis, also known as gardenia or cape jasmine, is the dried ripe fruit of the plant Gardenia jasminoides of the Rubiaceae family. Gardenia is widely distributed in South China, Central China, as well as tropical and subtropical regions around the world. The Pharmacopoeia of the People's Republic of China lists gardenia as a commonly used traditional Chinese medicine, and the fruits, flowers, roots and leaves of gardenia can all be used as medicine. "Shennong Ben Cao Jing", "Treatise on Febrile Diseases" and "Yanyi of Materia Medica" all have very detailed records on the medicinal value of gardenia. It is cold in nature, bitter in taste, non-toxic, mainly belongs to the heart, lung and triple energizer meridians, and has the effects of cooling blood and detoxifying, clearing heat and diuresis. Gardenia is mainly used in Eastern countries to extract gardenia yellow pigment as an edible pigment and a health food for cooking porridge and making tea. Gardenia has numerous and complex chemical components. Modern clinical pharmacological studies have shown that many chemical components in gardenia have pharmacological effects such as hypoglycemic, hypolipidemic, hepatoprotective and cholagogic, promoting pancreatic secretion, improving cerebral ischemia injury and anti-inflammatory. Modern research has found that gardenia contains a variety of chemical components, such as organic acid esters (chlorogenic acid, crocetin acid, etc.), iridoids (gardenoside), polyphenols, flavonoids (gardenin), triterpenoids (ursolic acid), and also contains proteins, acidic polysaccharides, D-mannitol, sterols, triterpenoid saponins, long-chain alkanes, chlorophyll and volatile oils.

[0003] The main active ingredient of gardenia is geniposide, an iridoid, which has pharmacological activities such as hepatoprotective and cholagogic, anti-inflammatory, anti-tumor, anti-mutagenic, antioxidant, anti-thrombotic, anti-hypertensive, protecting nerve cells, repairing damaged tissues and hypoglycemic. In particular, its hypoglycemic effect has received great attention in recent years. Research shows that the biological activities of geniposide are mostly achieved through its aglycone genipin. Geniposide is the glucoside of the iridoid monoterpene genipin, also known as genipin glycoside, dehydroxygardenoside, gardenoside, gardenia glycoside, with the molecular formula C 17 H 24 O, with a molecular weight of 388.37 daltons. It is a white or off-white crystalline powder, odorless, slightly hygroscopic, with a melting point of 160-164 °C, easily soluble in water, soluble in organic solvents such as ethanol and propanol, and insoluble in petroleum ether. Genipin is the hydrolysis product of geniposide, that is, gardenoside aglycone, also known as gardenin, and is derived from plants such as gardenia fruits and eucommia leaves. In 1960, Djerassit et al. prepared and extracted genipin from gardenia fruits, and determined its structure by means of nuclear magnetic resonance spectroscopy data and chemical degradation experiments. Genipin is a white crystal, belonging to the iridoid monoterpene, with the molecular formula C11 H 14 O5, with a molecular weight of 226.2, a melting point of 120 - 121 °C, and a specific rotation of +135. Genipin is easily soluble in organic solvents such as methanol, ethanol, acetone, ethyl acetate, and ether, and has a relatively low solubility in water.

[0004] Gardenia blue pigment is a blue or bluish-violet pigment prepared by the chemical reaction of genipin with the primary amino group of amino acids or proteins. Gardenia blue pigment is listed as an edible pigment in the "National Standard for the Use of Food Additives of the People's Republic of China" and has the characteristics of high safety, good coloring performance, and certain health care functions or physiological activities. At present, the preparation of gardenia blue pigment mainly uses the enzymatic method and the microbial transformation method. The principle of preparing gardenia blue pigment by the enzymatic method is as follows: A mixture including genipin obtained by hydrolyzing the glycosidic bond of geniposide with β-glucosidase reacts with amino acids under heating and neutral - alkaline conditions to prepare gardenia blue pigment (see the chemical reaction equation for the preparation of gardenia blue pigment); the principle of preparing gardenia blue pigment by the microbial transformation method is as follows: β-glucosidase produced by culturing microorganisms hydrolyzes geniposide into genipin, which reacts with amino acids produced by microbial fermentation or added to prepare gardenia blue pigment. The essential principles of preparing gardenia blue pigment by the enzymatic method and the microbial transformation method are exactly the same, but the quality, color value, purity, and other indicators of the gardenia blue pigment prepared by the microbial transformation method are far worse than those of the enzymatic method, and it is a mixture of multiple amino acids and multiple proteins reacting with genipin. There are many deficiencies in preparing gardenia blue pigment by the enzymatic method and the microbial transformation method: A. The price of β-glucosidase is expensive, and the cost of preparing genipin by the enzymatic method is too high; B. Since the genipin produced by enzymatic hydrolysis can react with β-glucosidase as a protein to produce blue substances, it not only leads to the inactivation of the enzyme, low efficiency and incomplete hydrolysis in the enzymatic hydrolysis process, but also results in the fact that the prepared gardenia blue pigment is essentially a mixture of gardenia blue pigment obtained by the reaction of amino acids with genipin and gardenia blue pigment obtained by the reaction of enzyme protein with genipin, with low color value, low stability, and poor color of the gardenia blue pigment, and also leads to difficult separation and purification; C. Similar technical problems also exist in the preparation of genipin by immobilized β-glucosidase hydrolyzing geniposide; D. The color value, purity, stability, and usability of the gardenia blue pigment prepared by the microbial transformation method are worse than those of the enzymatic method. Therefore, exploring and developing a preparation technology for high-purity and high-color-value gardenia blue pigment has very important practical significance. Summary of the Invention

[0005] Aiming at the deficiencies in the deep processing of gardenia, the purpose of the present invention is to provide a method for preparing gardenia blue pigment using the under-column liquid after extracting gardenia yellow. This method is simple and easy to implement, convenient to operate, has prominent product characteristics, easy equipment selection and matching, low equipment investment, high product added value, good economic benefits, and can be mechanized.

[0006] To achieve the above object, the present invention is realized by the following solutions:

[0007] The technical concept of the present invention is as follows: By utilizing the property that copper ions can precipitate organic compounds containing carboxyl groups, potassium permanganate has weak oxidizing property and can oxidize colored substances and reducing organic substances under neutral pH conditions, nanofiltration membranes can retain geniposide with a relatively large molecular weight and permeate small molecule organic substances such as sucrose, monovalent metal ion compounds and water, divalent metal ions cannot permeate through the nanofiltration membrane but can form hydroxide or oxide precipitates, geniposide can dissolve in propanol while the polar organic compound formed after oxidation is insoluble in propanol, geniposide is sensitive to acid and is easily hydrolyzed by acid, and the hydrolyzed genipin is soluble in ethyl acetate and insoluble in water, and pure genipin can react with sodium isoleucinate to form pure gardenia blue pigment. The supernatant obtained after the column effluent after extracting gardenia yellow is precipitated with copper sulfate to remove carboxyl-containing impurities such as acidic polysaccharides, triterpenic acids, chlorophyll acids, proteins and chlorogenic acids is subjected to oxidative decolorization with potassium permanganate under neutral pH conditions and precipitates excessive copper ions to obtain a colorless decolorized supernatant; after the inherent calcium, magnesium, zinc and other divalent metal ions in the decolorized supernatant are converted into calcium hydroxide, magnesium hydroxide and zinc oxide under alkaline conditions, the nanofiltration membrane is used to retain geniposide, permeate inorganic salts containing monovalent metal ions, sucrose, other small molecule organic components and water, and the obtained nanofiltration concentrate is subjected to solid-liquid separation to remove calcium hydroxide, magnesium hydroxide and zinc oxide, and the obtained supernatant is spray-dried to obtain crude geniposide; the crude geniposide is heated and dissolved in propanol, geniposide is extracted, the solvent is recovered, and after recrystallization with propanol, high-quality geniposide is obtained; the high-quality geniposide is dissolved in water and subjected to two-phase acid hydrolysis in an ethyl acetate phase-aqueous phase, the genipin produced by hydrolysis is dissolved in the ethyl acetate phase, and the ethyl acetate phase is recovered to obtain crude genipin; the crude genipin is heated and dissolved in ethyl acetate, genipin is extracted, solid-liquid separation is carried out, low-temperature recrystallization is carried out, and the solvent is evaporated to obtain high-purity pure genipin; pure genipin is heated and reacted with sodium isoleucinate and spray-dried to obtain pure gardenia blue pigment.

[0008] A method for preparing gardenia blue pigment, comprising the following steps:

[0009] (1) Removing impurities by copper sulfate precipitation: Taking the column effluent after extracting gardenia yellow with gardenia as the raw material, adding an aqueous copper sulfate solution with a mass percentage concentration of 1-3% and a mass multiple of 0.05-0.1 times under stirring, and continuing to stir for 0.5-1 hour to precipitate carboxyl-containing impurities such as acidic polysaccharides, triterpenic acids, chlorophyll acids, proteins and chlorogenic acids in the column effluent with copper ions; carrying out solid-liquid separation, discarding the precipitate to obtain the supernatant for standby;

[0010] (2) Decolorization by potassium permanganate oxidation and removal of excessive copper ions: Take the supernatant obtained in step (1), heat it to a temperature of 30 - 70 °C, and while stirring, adjust the pH to 6.5 - 7.5 with an alkali solution / an acid solution. Add an aqueous potassium permanganate solution with a mass percentage concentration of 0.5 - 5% and a multiple of 0.02 - 0.05 times the mass of the supernatant. Control the pH at 6.5 - 7.5. Use potassium permanganate to oxidize colored substances such as chlorophyll, polyphenols, flavonoids, and residual gardenia yellow, as well as reducing components such as reducing sugars and chlorogenic acid in the supernatant under neutral conditions. After continuing to stir for 3 - 7 hours, adjust the pH to 7.5 - 8.5 with an alkali solution / an acid solution to cause excessive copper ions to form copper oxide precipitate. Perform solid-liquid separation, discard the precipitate containing components such as manganese dioxide and copper oxide, and obtain a colorless decolorized supernatant for standby;

[0011] (3) Nanofiltration concentration, filtration, and spray drying: Take the decolorized supernatant obtained in step (2), adjust the pH to 9.5 - 10.5 with an alkali solution / an acid solution to convert divalent metal ions such as calcium, magnesium, and zinc inherent in the decolorized supernatant into calcium hydroxide, magnesium hydroxide, and zinc oxide. Use a nanofiltration membrane device to retain geniposide, and permeate inorganic salts and organic salts containing monovalent metal ions, sucrose, other small molecular organic components, and water until the solid content mass percentage concentration of the nanofiltration concentrate is 20 - 30%. Discard the nanofiltration permeate to obtain a nanofiltration concentrate. Perform solid-liquid separation on the nanofiltration concentrate, discard the precipitate with components of calcium hydroxide, magnesium hydroxide, and zinc oxide, and obtain a supernatant. Perform spray drying on the supernatant to obtain a crude geniposide solid for standby;

[0012] (4) Extraction of geniposide with propanol and recrystallization: Add propanol with a multiple of 2.5 - 4.5 times the mass of the crude geniposide solid obtained in step (3), stir and disperse, heat with reflux of condensed water to a temperature of 60 - 75 °C, continue to stir and heat for 0.5 - 2.5 hours to dissolve and extract geniposide. Perform hot solid-liquid separation to obtain a supernatant and a precipitate. Use propanol to extract the precipitate for the second and third times, discard the precipitate of the third time, and combine the supernatants extracted three times to obtain a propanol solution of geniposide. Heat and evaporate to recover propanol to obtain a crude geniposide. Dissolve the crude geniposide with propanol at 70 - 75 °C, perform solid-liquid separation and discard the precipitate to obtain a saturated propanol solution of geniposide. Recrystallize at 0 - 10 °C and dry to remove the solvent to obtain a geniposide fine product for standby;

[0013] (5)Biphasic acid hydrolysis of ethyl acetate: At room temperature (20 - 25 °C, the same below), dissolve the geniposide fine product obtained in step (4) with pure water, control the mass percentage concentration of the obtained geniposide aqueous solution to be 5 - 15%, perform solid-liquid separation to discard the precipitate, and obtain a clear and transparent geniposide aqueous solution. Under stirring conditions, add hydrochloric acid solution, control the hydrochloric acid concentration of the geniposide aqueous solution to be 0.2 - 1.0 M, add ethyl acetate with a mass multiple of 1.5 - 3.5 times that of the geniposide aqueous solution, stir and disperse, control the stirring speed to be 20 - 70 rpm, reflux and heat with condensed water to a temperature of 25 - 35 °C, continue stirring and heating for 1.0 - 4.0 hours to hydrolyze geniposide into genipin and glucose, and use ethyl acetate to dissolve the genipin produced by hydrolysis. Perform hot liquid-liquid separation, discard the aqueous phase containing glucose and hydrochloric acid, and obtain an ethyl acetate solvent phase containing genipin. Heat and evaporate to recover ethyl acetate to obtain a genipin crude product. Dissolve the genipin crude product with ethyl acetate at 50 - 60 °C, perform solid-liquid separation to discard the precipitate, obtain a saturated ethyl acetate solution of genipin, recrystallize at 0 - 5 °C, and dry to remove the solvent to obtain pure genipin;

[0014] (6)Preparation of pure gardenia blue pigment: Take the pure genipin obtained in step (5), disperse it with pure water into a dispersion with a molar concentration of 0.1 - 0.5 M. Under stirring conditions, heat to 55 - 95 °C, add solid sodium isoleucinate, control the molar concentration ratio of genipin to sodium isoleucinate to be 1:1, continue heating for 0.5 - 2.5 hours to make genipin react with sodium isoleucinate to form gardenia blue pigment. After solid-liquid separation, spray-dry the supernatant to obtain a gardenia blue pigment powder product.

[0015] Preferably, the under-column liquid after extracting gardenia yellow in step (1) is: an aqueous solution obtained by using gardenia as a raw material and water as a solvent to extract water-soluble components including gardenia yellow pigment in gardenia, with or without concentration, the liquid flowing out from the lower end of the adsorption column containing adsorption resin after adsorbing gardenia yellow pigment, or a mixture including the liquid flowing out from the lower end of the resin adsorption column after washing the resin adsorption column adsorbing gardenia yellow pigment.

[0016] Preferably, the lye in steps (2) and (3) is an aqueous solution of pharmaceutical-grade or food-grade sodium hydroxide or potassium hydroxide; the acid in steps (2), (3), and (5) is pharmaceutical-grade or food-grade hydrochloric acid; the potassium permanganate in step (2) is pharmaceutical-grade or food-grade potassium permanganate.

[0017] Preferably, the nanofiltration membrane in step (3) has a molecular weight cut-off of 350 Daltons.

[0018] Preferably, the propanol in step (4) is pharmaceutical-grade or food-grade propanol.

[0019] Preferably, the ethyl acetate described in step (5) is pharmaceutical-grade or food-grade ethyl acetate.

[0020] Preferably, the sodium isoleucinate described in step (6) is pharmaceutical-grade or food-grade sodium isoleucinate.

[0021] In addition, the high-purity gardenia blue pigment is obtained by the preparation method of the present invention.

[0022] A gardenia blue pigment. In the present invention, cupric ions are used to remove carboxyl-containing impurities, potassium permanganate is used to oxidize colored substances under neutral conditions, nanofiltration is used to remove small-molecule components and concentrate geniposide, propanol is used for dissolution, extraction and recrystallization of geniposide, ethyl acetate is used for biphasic acid hydrolysis of geniposide and dissolution and recrystallization of genipin in ethyl acetate, and the reaction of genipin pure product with sodium isoleucinate is used to prepare high-purity gardenia blue pigment, which has the advantages of high impurity removal rate, high recovery rate and purity of geniposide, sufficient hydrolysis and non-destruction of geniposide, high purity and color value of gardenia blue pigment, low cost, and the advantage of mechanized preparation of genipin.

[0023] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0024] (1) By using cupric ions of copper sulfate, the present invention's method precipitates and extracts macromolecular impurities containing carboxyl groups such as acidic polysaccharides, proteins, nucleic acids and other polysaccharides including pectin in the column bottom liquid after extracting gardenia yellow, and precipitates and extracts small and medium molecular impurities containing carboxyl groups such as triterpenic acids, chlorophyllic acids, crocetin, fatty acids and chlorogenic acids in the column bottom liquid after extracting gardenia yellow, solving the problems of difficult removal and poor effect of large and small molecular impurities containing carboxyl groups in the column bottom liquid after extracting gardenia yellow. Since the effect of cupric ions precipitating large and small molecular impurities containing carboxyl groups in the column bottom liquid after precipitating gardenia yellow is far better than that of calcium ions and zinc ions, the technical effect of fully removing large and small molecular impurities containing carboxyl groups and purifying the column bottom liquid after extracting gardenia yellow is achieved, and the removal rate reaches more than 98%.

[0025] (2) By taking advantage of the relatively weak oxidation ability of potassium permanganate under neutral pH conditions, the method of the present invention oxidizes colored substances such as chlorophyll, polyphenols, flavonoids, and residual gardenia yellow, as well as reducing components such as reducing sugars and chlorogenic acid in the supernatant obtained by removing impurities through copper ion precipitation. Through the technical treatment of precipitating excessive copper ions under weakly alkaline conditions, the problem of difficult decolorization of the column effluent after extracting gardenia yellow is solved. It avoids the oxidation of geniposide by strong oxidizing agents such as hydrogen peroxide, ozone, and chlorine dioxide, although they can oxidize and decolorize but also cause the oxidation of geniposide. The technical problems and difficulties such as the formation of water-soluble complexes between excessive copper ions and geniposide are solved. The technical effects of effective decolorization, oxidizing organic substances with relatively small polarity into those with relatively large polarity for subsequent separation, avoiding the oxidation of geniposide, generating manganese dioxide insoluble in water so that there is no residual manganese ion in the solution, and precipitating copper ions to liberate geniposide are achieved. The decolorization rate reaches 99%, the removal rates of manganese ions and copper ions reach 100%, and the retention rate of geniposide reaches 100%.

[0026] (3) By using the method of the present invention, under alkaline conditions (pH 9.5 - 10.5), the ionic compounds in the decolorized supernatant are converted into sodium salts, and divalent metal ions such as calcium, magnesium, and zinc inherent in the decolorized supernatant are converted into calcium hydroxide, magnesium hydroxide, and zinc oxide. Then, geniposide is intercepted by a nanofiltration membrane with a molecular weight cut-off of 350, and inorganic salts and organic salts containing monovalent metal ions, sucrose, other small-molecule organic components, and water pass through. After nanofiltration concentration, calcium hydroxide, magnesium hydroxide, and zinc oxide precipitates are separated from the solid and liquid. The technical problems and difficulties such as the difficult separation of geniposide from sucrose with a similar molecular weight and the ineffective permeation of divalent metal ions and polyvalent metal ions due to the Donnan effect of the nanofiltration membrane are solved. The technical effects of fully separating small-molecule organic impurities such as sucrose, fully desalting, fully intercepting geniposide and stabilizing geniposide (geniposide is stable under alkaline conditions and easily hydrolyzes under acidic conditions), and improving the membrane flux are achieved, as well as the technical effects of fully purifying geniposide and removing divalent and polyvalent metal ions. The removal rate of divalent and polyvalent metal ions reaches more than 96%, and the purity of geniposide reaches more than 85%.

[0027] (4) Purifying geniposide is one of the key steps of the present invention. The method of the present invention dissolves and extracts geniposide from the obtained crude geniposide solid by using propanol with relatively low polarity and relatively high boiling point under heating conditions. After separating impurities and recovering the solvent, a crude geniposide is obtained. The crude geniposide is subjected to technical treatments such as heating and dissolving in propanol, solid-liquid separation, and low-temperature recrystallization, which solves the technical problems and difficulties that impurities with relatively larger polarity than geniposide and impurities with relatively smaller polarity than geniposide in the crude geniposide are difficult to separate from geniposide. It achieves the technical effects that impurities with relatively larger polarity than geniposide in the crude geniposide are separated from geniposide because they are insoluble in propanol, impurities with relatively smaller polarity than geniposide dissolve in propanol and cannot crystallize and are separated from geniposide by crystallization, the purity of geniposide is improved, and high-quality geniposide is obtained. The purity of geniposide reaches over 99.5%.

[0028] (5) Preparing high-purity genipin is the second key step of the present invention. The method of the present invention uses a two-phase acid hydrolysis of geniposide to genipin and glucose in an ethyl acetate phase-aqueous phase at low temperature, and the genipin produced by the acid hydrolysis dissolves and enters the ethyl acetate phase to prevent the hydrochloric acid in the aqueous phase from destroying the structure of genipin and breaking the hydrolysis equilibrium to accelerate the acid hydrolysis of geniposide. The aqueous phase dissolves hydrochloric acid and glucose produced by the acid hydrolysis, and the genipin is recrystallized from ethyl acetate. Through these technical treatments, it solves the technical problems and difficulties such as the destruction of the structure of genipin by acid, the difficulty in obtaining pure genipin, the common use of enzymatic hydrolysis of geniposide to genipin, the reaction and color change of the enzyme with the genipin produced by the enzymatic hydrolysis, and the destruction of the enzyme structure resulting in the loss of enzyme activity, incomplete enzymatic hydrolysis, and low yield. It achieves the technical effects of preparing genipin with an undestroyed structure by acid hydrolysis of geniposide, preparing pure genipin, avoiding the high cost, low efficiency, and insufficiency of enzymatic hydrolysis of geniposide to genipin. The recovery rate of genipin reaches over 97%, and the purity of genipin reaches over 99.7%.

[0029] (6) By using the technical treatment of directly heating and reacting genipin pure product with sodium isoleucinate pure product without adjusting the pH and then spray-drying to prepare pure product and gardenia blue pigment with high color value, the method of the present invention solves the following technical problems and difficulties: the product obtained by enzymatic hydrolysis of geniposide is actually a mixture of genipin and gardenia blue obtained by the reaction of genipin with the primary amino group of enzyme protein; the product obtained by reacting this mixture with amino acid to prepare gardenia blue pigment is actually a mixture of gardenia blue pigment formed by amino acid-genipin and gardenia blue pigment formed by enzyme protein-genipin; glucose in the product obtained by enzymatic hydrolysis of geniposide is difficult to separate from genipin in the product obtained by enzymatic hydrolysis of geniposide, so genipin is impure, the obtained gardenia blue pigment is impure and has a low color value; the salt formed by adjusting the pH is difficult to separate from the gardenia blue pigment, so the obtained gardenia blue pigment is impure and has a low color value, etc. The technical effects of preparing pure product and gardenia blue pigment with high color value, simplifying the process and reducing the separation cost are achieved.

[0030] (7) Compared with the prior art, the progress of the present invention lies in that the prior art can only use adsorption resin to purify and prepare geniposide, β-glucosidase hydrolyzes geniposide into genipin and glucose, and the enzyme hydrolysis mixture and amino acid are used to prepare impure and low-color-value gardenia blue pigment by heating and adjusting the pH. However, the present invention realizes the technical breakthrough of using the under-column liquid after extracting gardenia yellow as the raw material, removing impurities by copper sulfate precipitation, decolorizing by potassium permanganate oxidation and removing excessive copper ions, nanofiltration concentration, filtration and spray-drying, extracting geniposide with propanol and recrystallizing to prepare geniposide, hydrolyzing geniposide with ethyl acetate biphasic acid to prepare genipin pure product, not using enzymatic hydrolysis of geniposide, and using pure genipin and sodium isoleucinate without adjusting the pH to prepare gardenia blue pigment with high purity and high color value. The obtained gardenia blue pigment is a dark blue crystalline solid powder, with a purity of 99.0 - 99.9%, a maximum absorption wavelength of 600 nm, and a color value E 1％ 1cm (600nm) ≥ 300. Description of the Drawings

[0031] Figure 1 It is the process flow chart of a method for preparing gardenia blue pigment by using the under-column liquid after extracting gardenia yellow according to the present invention. Detailed Embodiments

[0032] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of them. All other embodiments obtained by those of ordinary skill in the art without creative efforts based on the embodiments of the present invention belong to the protection scope of the present invention.

[0033] Example 1:

[0034] According toFigure 1 It can be known that a method for preparing gardenia blue pigment using the column bottom liquid after extracting gardenia yellow pigment includes the following steps:

[0035] (1) Removing impurities by copper sulfate precipitation: Take 5000 kg of the column bottom liquid after extracting gardenia yellow pigment, which is obtained by using water as a solvent to extract water-soluble components including gardenia yellow pigment from gardenia as a raw material and flowing out from the lower end of the resin adsorption column after adsorbing gardenia yellow pigment by an adsorption column containing adsorption resin. Under stirring, add 375 kg of an aqueous copper sulfate solution with a mass percentage concentration of 2%. After continuing to stir for 1 hour, perform plate and frame filtration, discard the precipitate, and obtain the filtrate for standby.

[0036] (2) Oxidative decolorization with potassium permanganate and removing excessive copper ions: Take the filtrate obtained in step (1), heat it to a temperature of 50 °C, under stirring, adjust the pH to 7.0 with a mass percentage concentration of 20%, add 175 kg of an aqueous potassium permanganate solution with a mass percentage concentration of 2.75%, control the pH at 7.0, continue to stir for 5 hours, then adjust the pH to 8.0 with a mass percentage concentration of 20%, perform plate and frame filtration, discard the precipitate, and obtain a colorless decolorized supernatant for standby.

[0037] (3) Nanofiltration concentration, filtration, and spray drying: Take the decolorized supernatant obtained in step (2), adjust the pH to 10.0 with a mass percentage concentration of 20%, concentrate it with a nanofiltration membrane device with a cut-off molecular weight of 350 Dalton until the solid mass percentage concentration of the nanofiltration concentrate is 25%, discard the nanofiltration permeate, and obtain the nanofiltration concentrate. The nanofiltration concentrate is filtered through a plate and frame, discard the component precipitate, and obtain the filtrate. Perform spray drying on the filtrate to obtain a crude product of geniposide solid for standby.

[0038] (4) Extracting geniposide with propanol and recrystallization: Add propanol with a mass multiple of 3.5 times that of the crude geniposide solid obtained in step (3), stir and disperse, reflux and heat with condensed water to a temperature of 67.5 °C to dissolve and extract geniposide. After continuing to stir and heat for 1.5 hours, perform hot centrifugal separation to obtain the supernatant and precipitate. Extract the precipitate with propanol for the second and third times, discard the precipitate of the third time, combine the supernatants extracted three times to obtain a propanol solution of geniposide, heat and evaporate to recover propanol to obtain a crude product of geniposide. Dissolve the crude geniposide with propanol at 72.5 °C, perform solid-liquid separation and discard the precipitate to obtain a saturated propanol solution of geniposide, recrystallize at 5 °C, and dry to remove the solvent to obtain 25 kg of geniposide fine product for standby.

[0039] (5) Biphasic acid hydrolysis of ethyl acetate: At room temperature, dissolve the geniposide fine product obtained in step (4) with pure water, control the mass percentage concentration of the obtained geniposide aqueous solution to be 10%, filter through a plate and frame to discard the precipitate, and obtain a clear and transparent geniposide aqueous solution. Under stirring conditions, add hydrochloric acid solution, control the hydrochloric acid concentration of the geniposide aqueous solution to be 0.6 M, add ethyl acetate with a mass multiple of 2.5 times that of the geniposide aqueous solution, stir and disperse, control the stirring speed to be 45 rpm, reflux and heat with condensed water to a temperature of 30 °C, continue to stir and heat for 2.5 hours, then separate the hot liquid while it is hot, discard the aqueous phase, and obtain an ethyl acetate solvent phase containing genipin. Heat and evaporate to recover ethyl acetate to obtain a genipin crude product. Dissolve the genipin crude product with ethyl acetate at 55 °C, centrifuge to separate and discard the precipitate to obtain a saturated ethyl acetate solution of genipin, recrystallize at 2.5 °C, and dry to remove the solvent to obtain 14.5 kg of genipin pure product;

[0040] (6) Preparation of pure gardenia blue pigment: Take the genipin pure product obtained in step (5), disperse it with pure water into a dispersion with a molar concentration of 0.3 M, under stirring conditions, heat to 75 °C, add solid sodium isoleucinate, control the molar concentration ratio of genipin to sodium isoleucinate to be 1:1, continue to heat for 1.5 hours, then separate the solid and liquid, and spray-dry the supernatant to obtain 23.1 kg of gardenia blue pigment powder product.

[0041] ( Figure 1 There are nine steps, and six of them are described below. The under-column liquid after extracting gardenia yellow and the copper sulfate precipitate are removed of impurities as step 1; precipitating excessive copper ions and decolorizing by potassium permanganate oxidation is step 2; nanofiltration concentration, filtration and spray drying are step 3; extracting geniposide with propanol and recrystallization are step 4; biphasic acid hydrolysis of ethyl acetate, dissolving with ethyl acetate and recrystallization are step 5; the color reaction of genipin pure product with sodium isoleucinate, spray drying, and pure gardenia blue pigment are step 6, the same below)

[0042] The obtained gardenia blue pigment is a dark blue crystalline solid powder. Determined by HPLC method, the purity of the obtained gardenia blue pigment is 99.5%; determined by full-wavelength scanning method, the maximum absorption wavelength of the obtained gardenia blue pigment is 600 nm; analyzed by spectrophotometry, the color value E 1％ 1cm (600 nm) is 325.

[0043] Example 2:

[0044] A method for preparing gardenia blue pigment using the under-column liquid after extracting gardenia yellow, comprising the following steps:

[0045] (1) Removal of impurities by copper sulfate precipitation: Take the aqueous solution obtained by extracting the water-soluble components including gardenia yellow pigment from gardenia with water as the solvent. After adsorbing gardenia yellow pigment through an adsorption column containing an adsorption resin, 7000 kg of the combined column effluent at the lower end of the resin adsorption column after extracting gardenia yellow and the washing liquid flowing out from the lower end of the resin adsorption column after washing the resin adsorption column for adsorbing gardenia yellow pigment with water is added with 350 kg of copper sulfate aqueous solution with a mass percentage concentration of 3% under stirring. After continuing to stir for 1 hour, plate and frame filtration is carried out, and the precipitate is discarded to obtain a filtrate for standby;

[0046] (2) Oxidation and decolorization with potassium permanganate and removal of excessive copper ions: Take the filtrate obtained in step (1), heat it to a temperature of 30 °C, and under stirring, adjust the pH to 7.0 with a mass percentage concentration of 40%. Add 140 kg of potassium permanganate aqueous solution with a mass percentage concentration of 5%, control the pH at 7.0, continue to stir for 7 hours, then adjust the pH to 8.5 with a mass percentage concentration of 40%, and carry out plate and frame filtration, discarding the precipitate to obtain a colorless decolorized supernatant for standby;

[0047] (3) Nanofiltration concentration, filtration and spray drying: Take the decolorized supernatant obtained in step (2), adjust the pH to 10.5 with a mass percentage concentration of 40%, and concentrate it with a nanofiltration membrane device with a cut-off molecular weight of 350 Da until the solid mass percentage concentration of the nanofiltration concentrate is 30%. Discard the nanofiltration permeate to obtain the nanofiltration concentrate. The nanofiltration concentrate is filtered through a plate and frame, and the component precipitate is discarded to obtain a filtrate. The filtrate is spray-dried to obtain a crude geniposide solid for standby;

[0048] (4) Extraction of geniposide with propanol and recrystallization: Add 4.5 times the mass of the crude geniposide solid obtained in step (3) of propanol, stir and disperse, and reflux and heat with condensed water to a temperature of 75 °C to dissolve and extract geniposide. After continuing to stir and heat for 2.5 hours, centrifuge while it is hot to obtain a supernatant and a precipitate. The precipitate is extracted with propanol for the second and third times, and the precipitate of the third extraction is discarded. The supernatants of the three extractions are combined to obtain a propanol solution of geniposide. Heat and evaporate to recover propanol to obtain a crude geniposide. Dissolve the crude geniposide with propanol at 75 °C, separate the solid and liquid, discard the precipitate, obtain a saturated propanol solution of geniposide, carry out recrystallization at 0 °C, and dry to remove the solvent to obtain 28 kg of geniposide fine product for standby;

[0049] (5) Biphasic acid hydrolysis of ethyl acetate: At room temperature, dissolve the geniposide fine product obtained in step (4) with pure water, and control the mass percentage concentration of the obtained geniposide aqueous solution to be 5%. Filter through a plate-and-frame filter to discard the precipitate, and obtain a clear and transparent geniposide aqueous solution. Under stirring conditions, add hydrochloric acid solution, control the hydrochloric acid concentration of the geniposide aqueous solution to be 0.2 M, add ethyl acetate with a mass multiple of 1.5 times that of the geniposide aqueous solution, stir and disperse, control the stirring speed to be 20 rpm, reflux and heat with condensed water to a temperature of 35 °C, continue stirring and heating for 4.0 hours, then perform liquid-liquid separation while it is hot, discard the aqueous phase, and obtain an ethyl acetate solvent phase containing genipin. Heat and evaporate to recover ethyl acetate to obtain a genipin crude product. Dissolve the genipin crude product with ethyl acetate at 50 °C, centrifuge to separate and discard the precipitate to obtain a saturated ethyl acetate solution of genipin, recrystallize at 0 °C, and dry to remove the solvent to obtain 16.2 kg of genipin pure product.

[0050] (6) Preparation of pure gardenia blue pigment: Take the genipin pure product obtained in step (5), disperse it with pure water into a dispersion with a molar concentration of 0.5 M. Under stirring conditions, heat to 95 °C, add solid sodium isoleucinate, control the molar concentration ratio of genipin to sodium isoleucinate to be 1:1, continue heating for 0.5 hours, then perform solid-liquid separation, and spray-dry the supernatant to obtain 25.9 kg of gardenia blue pigment powder product.

[0051] The obtained gardenia blue pigment is a dark blue crystalline solid powder. Determined by HPLC method, the purity of the obtained gardenia blue pigment is 99.9%; determined by full-wavelength scanning method, the maximum absorption wavelength of the obtained gardenia blue pigment is 600 nm; analyzed by spectrophotometry, the color value E 1％ 1cm (600 nm) is 339.

[0052] Example 3:

[0053] A method for preparing gardenia blue pigment using the under-column liquid after extracting gardenia yellow, comprising the following steps:

[0054] (1) Removal of impurities by copper sulfate precipitation: Take the aqueous ethanol solution obtained by extracting the alcohol-water soluble components including gardenia yellow pigment from gardenia using 75% aqueous ethanol solution as the solvent, and after heating to recover ethanol, the obtained aqueous solution is separated from the oil-like substances insoluble in water, and then the under-column liquid of 3000 kg flowing out from the resin adsorption column after adsorbing gardenia yellow pigment by the adsorption column containing adsorption resin. Under stirring conditions, add 300 kg of copper sulfate aqueous solution with a mass percentage concentration of 1%, continue stirring for 0.5 hours, then filter through a plate-and-frame filter, discard the precipitate to obtain the filtrate for standby;

[0055] (2) Oxidation decolorization with potassium permanganate and removal of excessive copper ions: Take the filtrate obtained in step (1), heat it to 70 °C, and under stirring, adjust the pH to 7.0 with a 30% mass percentage concentration. Add 150 kg of an aqueous potassium permanganate solution with a 5% mass percentage concentration, control the pH at 7.0, continue stirring for 3 hours, then adjust the pH to 7.5 with a 30% mass percentage concentration, perform plate and frame filtration, discard the precipitate, and obtain a colorless decolorized supernatant for standby;

[0056] (3) Nanofiltration concentration, filtration, and spray drying: Take the decolorized supernatant obtained in step (2), adjust the pH to 9.5 with a 30% mass percentage concentration, and concentrate it with a nanofiltration membrane device with a molecular weight cut-off of 350 Da until the solid mass percentage concentration of the nanofiltration concentrate is 20%. Discard the nanofiltration permeate to obtain the nanofiltration concentrate. The nanofiltration concentrate is filtered through a plate and frame, and the component precipitate is discarded to obtain a filtrate. The filtrate is spray-dried to obtain a crude geniposide solid for standby;

[0057] (4) Extraction of geniposide with propanol and recrystallization: Add propanol in an amount 2.5 times the mass of the crude geniposide solid obtained in step (3), stir and disperse, and reflux and heat with condensing water to 60 °C to dissolve and extract geniposide. Continue stirring and heating for 2.5 hours, then centrifuge while it is hot to obtain a supernatant and a precipitate. Use propanol to extract the precipitate for the second and third times, discard the precipitate of the third time, combine the supernatants extracted three times to obtain a propanol solution of geniposide, heat and evaporate to recover propanol to obtain a crude geniposide. Dissolve the crude geniposide with propanol at 70 °C, perform solid-liquid separation and discard the precipitate to obtain a saturated propanol solution of geniposide, recrystallize at 10 °C, and dry to remove the solvent to obtain 60 kg of geniposide fine product for standby;

[0058] (5) Biphasic acid hydrolysis with ethyl acetate: At room temperature, dissolve the geniposide fine product obtained in step (4) with pure water, control the mass percentage concentration of the obtained geniposide aqueous solution to be 15%, perform plate and frame filtration and discard the precipitate to obtain a clear and transparent geniposide aqueous solution. Under stirring conditions, add a hydrochloric acid solution, control the hydrochloric acid concentration of the geniposide aqueous solution to be 1.0 M, add ethyl acetate in an amount 3.5 times the mass of the geniposide aqueous solution, stir and disperse, control the stirring speed at 70 rpm, reflux and heat with condensing water to 35 °C, continue stirring and heating for 4.0 hours, then perform liquid-liquid separation while it is hot, discard the aqueous phase to obtain an ethyl acetate solvent phase containing genipin. Heat and evaporate to recover ethyl acetate to obtain a crude genipin. Dissolve the crude genipin with ethyl acetate at 60 °C, centrifuge and discard the precipitate to obtain a saturated ethyl acetate solution of genipin, recrystallize at 5 °C, and dry to remove the solvent to obtain 34.8 kg of genipin pure product.

[0059] (6) Preparation of pure gardenia blue pigment: Take the pure genipin obtained in step (5), disperse it with pure water into a dispersion with a molar concentration of 0.1 M, heat it to 55 °C under stirring conditions, add solid sodium isoleucinate, control the molar concentration ratio of genipin to sodium isoleucinate to be 1:1, continue heating for 2.5 hours, then perform solid-liquid separation, and spray-dry the supernatant to obtain 55.2 kg of gardenia blue pigment powder product.

[0060] The obtained gardenia blue pigment is a dark blue crystalline solid powder. Determined by HPLC method, the purity of the obtained gardenia blue pigment is 99.0%; determined by full-wavelength scanning method, the maximum absorption wavelength of the obtained gardenia blue pigment is 600 nm; analyzed by spectrophotometry, the color value E 1％ 1cm (600 nm) is 301.

[0061] Example 4:

[0062] A method for preparing gardenia blue pigment using the under-column liquid after extracting gardenia yellow, comprising the following steps:

[0063] (1) Removal of impurities by copper sulfate precipitation: Take the aqueous ethanol solution obtained by extracting the alcohol-water soluble components including gardenia yellow pigment from gardenia with a 70% aqueous ethanol solution as the solvent, the aqueous solution obtained by heating and recovering ethanol, after separating the oil-like substances insoluble in water, the under-column liquid flowing out from the lower end of the resin adsorption column after adsorbing gardenia yellow pigment by the adsorption column containing adsorption resin, and the mixed under-column liquid of the washing liquid flowing out from the lower end of the resin adsorption column after washing the resin adsorption column for adsorbing gardenia yellow pigment, which is 5000 kg. Under stirring conditions, add 250 kg of copper sulfate aqueous solution with a mass percentage concentration of 2%, continue stirring for 1.0 hour, then perform plate-and-frame filtration, discard the precipitate to obtain the filtrate for standby;

[0064] (2) Oxidation and decolorization with potassium permanganate and removal of excessive copper ions: Take the filtrate obtained in step (1), heat it to a temperature of 40 °C, under stirring conditions, adjust the pH to 7.0 with a mass percentage concentration of 25%, add 250 kg of potassium permanganate aqueous solution with a mass percentage concentration of 4.5%, control the pH to 7.0, continue stirring for 7 hours, then adjust the pH to 8.5 with a mass percentage concentration of 25%, perform plate-and-frame filtration, discard the precipitate, and obtain a colorless decolorized supernatant for standby;

[0065] (3) Nanofiltration concentration, filtration, and spray drying: Take the decolorized supernatant obtained in step (2), adjust the pH to 10.5 with a mass percentage concentration of 25%, concentrate it with a nanofiltration membrane device with a molecular weight cut-off of 350 Da until the mass percentage concentration of the solids in the nanofiltration concentrate is 30%, discard the nanofiltration permeate, and obtain the nanofiltration concentrate. The nanofiltration concentrate is filtered through a plate and frame filter, and the component precipitate is discarded to obtain the filtrate. The filtrate is spray-dried to obtain the crude geniposide solid for standby;

[0066] (4) Extraction of geniposide with propanol and recrystallization: Add propanol at a multiple of 4.5 times the mass of the crude geniposide solid obtained in step (3), stir and disperse, reflux and heat with condensing water to 70 °C to dissolve and extract geniposide. After continuing to stir and heat for 0.5 hours, centrifuge and separate while it is hot to obtain the supernatant and precipitate. Extract the precipitate with propanol for the second and third times, discard the precipitate of the third time, combine the supernatants extracted three times to obtain the propanol solution of geniposide, heat and evaporate to recover propanol to obtain the crude geniposide. Dissolve the crude geniposide with propanol at 75 °C, separate the solid and liquid, discard the precipitate, obtain the saturated propanol solution of geniposide, recrystallize at 0 °C, and dry to remove the solvent to obtain 90 kg of geniposide fine product for standby;

[0067] (5) Biphasic acid hydrolysis with ethyl acetate: At room temperature, dissolve the geniposide fine product obtained in step (4) with pure water, control the mass percentage concentration of the obtained geniposide aqueous solution to be 7.5%, filter through a plate and frame filter to discard the precipitate, and obtain a clear and transparent geniposide aqueous solution. Under stirring conditions, add hydrochloric acid solution, control the hydrochloric acid concentration of the geniposide aqueous solution to be 0.8 M, add ethyl acetate at a multiple of 3.5 times the mass of the geniposide aqueous solution, stir and disperse, control the stirring speed to be 60 rpm, reflux and heat with condensing water to 35 °C, continue to stir and heat for 4.0 hours, then separate the liquid while it is hot, discard the aqueous phase, and obtain the ethyl acetate solvent phase containing genipin. Heat and evaporate to recover ethyl acetate to obtain the crude genipin. Dissolve the crude genipin with ethyl acetate at 60 °C, centrifuge and separate to discard the precipitate, obtain the saturated ethyl acetate solution of genipin, recrystallize at 0 °C, and dry to remove the solvent to obtain 52.2 kg of genipin pure product.

[0068] (6) Preparation of pure gardenia blue pigment: Take the genipin pure product obtained in step (5), disperse it with pure water into a dispersion with a molar concentration of 0.2 M. Under stirring conditions, heat to 90 °C, add solid sodium isoleucinate, control the molar concentration ratio of genipin to sodium isoleucinate to be 1:1, continue to heat for 1.0 hour, then separate the solid and liquid, and spray-dry the supernatant to obtain 87.6 kg of gardenia blue pigment powder product.

[0069] The obtained gardenia blue pigment is a dark blue crystalline solid powder. Determined by HPLC method, the purity of the obtained gardenia blue pigment is 99.2%; determined by the full wavelength scanning method, the maximum absorption wavelength of the obtained gardenia blue pigment is 600 nm; analyzed by spectrophotometry, the color value E 1％ 1cm (600 nm) is 304.

[0070] Example 5:

[0071] A method for preparing gardenia blue pigment using the under-column liquid after extracting gardenia yellow, comprising the following steps:

[0072] (1) Removing impurities by copper sulfate precipitation: Take 10,000 kg of the under-column liquid after extracting gardenia yellow, which is obtained by using water as a solvent to extract water-soluble components including gardenia yellow pigment from gardenia as a raw material and flowing out from the lower end of the resin adsorption column after adsorbing gardenia yellow pigment by an adsorption column containing an adsorption resin. Under stirring, add 1000 kg of an aqueous copper sulfate solution with a mass percentage concentration of 1%. After continuing to stir for 0.5 hours, perform plate and frame filtration, discard the precipitate to obtain a filtrate for standby;

[0073] (2) Oxidative decolorization with potassium permanganate and removal of excessive copper ions: Take the filtrate obtained in step (1), heat it to a temperature of 55 °C. Under stirring, adjust the pH to 7.0 with a mass percentage concentration of 30%, add 500 kg of an aqueous potassium permanganate solution with a mass percentage concentration of 4%, control the pH at 7.0, continue to stir for 6 hours, then adjust the pH to 8.0 with a mass percentage concentration of 30%, perform plate and frame filtration, discard the precipitate to obtain a colorless decolorized supernatant for standby;

[0074] (3) Nanofiltration concentration, filtration and spray drying: Take the decolorized supernatant obtained in step (2), adjust the pH to 10.5 with a mass percentage concentration of 30%, concentrate it with a nanofiltration membrane device with a cut-off molecular weight of 350 Dalton until the solid mass percentage concentration of the nanofiltration concentrate is 27.5%, discard the nanofiltration permeate to obtain a nanofiltration concentrate. The nanofiltration concentrate is filtered by plate and frame, discard the component precipitate to obtain a filtrate. Perform spray drying on the filtrate to obtain a crude geniposide solid for standby;

[0075] (4) Extraction of geniposide with propanol and recrystallization: Add propanol in an amount 4.0 times the mass of the crude geniposide solid obtained in step (3), stir to disperse, heat with reflux of condensed water to 75 °C to dissolve and extract geniposide, continue to stir and heat for 2.0 hours, then centrifuge while it is hot to obtain a supernatant and a precipitate. Extract the precipitate with propanol for the second and third times, discard the precipitate from the third extraction, combine the supernatants from the three extractions to obtain a propanol solution of geniposide, heat and evaporate to recover propanol to obtain a crude geniposide product. Dissolve the crude geniposide product in propanol at 70 °C, perform solid-liquid separation and discard the precipitate to obtain a saturated propanol solution of geniposide, recrystallize at 0 °C, and dry to remove the solvent to obtain 49.8 kg of geniposide fine product for standby;

[0076] (5) Biphasic acid hydrolysis with ethyl acetate: At room temperature, dissolve the geniposide fine product obtained in step (4) with pure water, control the mass percentage concentration of the obtained geniposide aqueous solution to be 12.5%, filter through a plate and frame to discard the precipitate to obtain a clear and transparent geniposide aqueous solution. Under stirring conditions, add a hydrochloric acid solution, control the hydrochloric acid concentration of the geniposide aqueous solution to be 1.0 M, add ethyl acetate in an amount 3.0 times the mass of the geniposide aqueous solution, stir to disperse, control the stirring speed to be 55 rpm, heat with reflux of condensed water to 35 °C, continue to stir and heat for 3.5 hours, then perform liquid-liquid separation while it is hot, discard the aqueous phase to obtain an ethyl acetate solvent phase containing genipin. Heat and evaporate to recover ethyl acetate to obtain a crude genipin product. Dissolve the crude genipin product in ethyl acetate at 60 °C, centrifuge to discard the precipitate to obtain a saturated ethyl acetate solution of genipin, recrystallize at 0 °C, and dry to remove the solvent to obtain 28.6 kg of genipin pure product.

[0077] (6) Preparation of pure gardenia blue pigment: Take the genipin pure product obtained in step (5), disperse it with pure water into a dispersion with a molar concentration of 0.3 M, under stirring conditions, heat to 85 °C, add solid sodium isoleucinate, control the molar concentration ratio of genipin to sodium isoleucinate to be 1:1, continue to heat for 1.5 hours and then perform solid-liquid separation, and spray-dry the supernatant to obtain 45.7 kg of gardenia blue pigment powder product.

[0078] The obtained gardenia blue pigment is a dark blue crystalline solid powder. Determined by HPLC method, the purity of the obtained gardenia blue pigment is 99.3%; determined by full-wavelength scanning method, the maximum absorption wavelength of the obtained gardenia blue pigment is 600 nm; analyzed by spectrophotometry, the color value E 1％ 1cm (600 nm) is 316.

[0079] Example 6:

[0080] A method for preparing gardenia blue pigment using the under-column liquid after extracting gardenia yellow, comprising the following steps:

[0081] (1) Removal of impurities by copper sulfate precipitation: Take the aqueous solution obtained by extracting water-soluble components including gardenia yellow pigment from gardenia using water as a solvent. After adsorbing gardenia yellow pigment through an adsorption column containing an adsorption resin, 15000 kg of the combined column effluent at the bottom of the column after extracting gardenia yellow (the liquid flowing out from the bottom of the resin adsorption column) and the washing liquid (the liquid flowing out from the bottom of the resin adsorption column after washing the resin adsorption column for adsorbing gardenia yellow pigment) is taken. Under stirring, an aqueous copper sulfate solution with a mass percentage concentration of 2.5% and a mass multiple of 1350 kg is added. After continuing to stir for 0.75 hours, plate and frame filtration is carried out, and the precipitate is discarded to obtain a filtrate for standby;

[0082] (2) Oxidation decolorization with potassium permanganate and removal of excessive copper ions: Take the filtrate obtained in step (1), heat it to a temperature of 65 °C. Under stirring, adjust the pH to 7.0 with a mass percentage concentration of 25%. Add 600 kg of an aqueous potassium permanganate solution with a mass percentage concentration of 3.5%, control the pH at 7.0, continue to stir for 6.5 hours, then adjust the pH to 8.5 with a mass percentage concentration of 25%, and carry out plate and frame filtration, discarding the precipitate to obtain a colorless decolorized supernatant for standby;

[0083] (3) Nanofiltration concentration, filtration and spray drying: Take the decolorized supernatant obtained in step (2), adjust the pH to 9.5 with a mass percentage concentration of 25%. Concentrate it with a nanofiltration membrane device with a cut-off molecular weight of 350 Da until the solid mass percentage concentration of the nanofiltration concentrate is 27.5%, discard the nanofiltration permeate to obtain a nanofiltration concentrate. The nanofiltration concentrate is filtered through a plate and frame, and the component precipitate is discarded to obtain a filtrate. The filtrate is spray-dried to obtain a crude product of geniposide solid for standby;

[0084] (4) Extraction of geniposide with propanol and recrystallization: Add propanol with a mass multiple of 3.0 times the mass of the crude geniposide solid obtained in step (3), stir and disperse, and heat with reflux of condensed water to a temperature of 65 °C to dissolve and extract geniposide. After continuing to stir and heat for 1.0 hour, centrifuge while it is hot to obtain a supernatant and a precipitate. The precipitate is extracted with propanol for the second and third times, discard the precipitate from the third extraction, and combine the supernatants from the three extractions to obtain a propanol solution of geniposide. Heat and evaporate to recover propanol to obtain a crude geniposide product. Dissolve the crude geniposide product in propanol at 72.5 °C, separate the solid and liquid phases, discard the precipitate, obtain a saturated propanol solution of geniposide, carry out recrystallization at 0 °C, and dry to remove the solvent to obtain 59.3 kg of geniposide fine product for standby;

[0085] (5)Biphasic acid hydrolysis of ethyl acetate: At room temperature, dissolve the geniposide fine product obtained in step (4) with pure water, and control the mass percentage concentration of the obtained geniposide aqueous solution to be 12.5%. Filter through a plate and frame to discard the precipitate, and obtain a clear and transparent geniposide aqueous solution. Under stirring conditions, add hydrochloric acid solution, control the hydrochloric acid concentration of the geniposide aqueous solution to be 0.9 M, add ethyl acetate with a mass multiple of 3.5 times that of the geniposide aqueous solution, stir and disperse, control the stirring speed to be 60 rpm, reflux and heat with condensed water to a temperature of 30 °C, continue stirring and heating for 4.0 hours, then separate the liquid while it is hot, discard the aqueous phase, and obtain an ethyl acetate solvent phase containing genipin. Heat and evaporate to recover ethyl acetate to obtain a genipin crude product. Dissolve the genipin crude product with ethyl acetate at 60 °C, centrifuge to discard the precipitate, obtain a saturated ethyl acetate solution of genipin, recrystallize at 0 °C, dry to remove the solvent, and obtain 33.9 kg of genipin pure product.

[0086] (6)Preparation of gardenia blue pigment pure product: Take the genipin pure product obtained in step (5), disperse it with pure water into a dispersion with a molar concentration of 0.4 M. Under stirring conditions, heat to 80 °C, add solid sodium isoleucinate, control the molar concentration ratio of genipin to sodium isoleucinate to be 1:1, continue heating for 2.0 hours, then separate the solid and liquid, and spray-dry the supernatant to obtain 53.8 kg of gardenia blue pigment powder product.

[0087] The obtained gardenia blue pigment is a dark blue crystalline solid powder. Determined by HPLC method, the purity of the obtained gardenia blue pigment is 99.4%; determined by full-wavelength scanning method, the maximum absorption wavelength of the obtained gardenia blue pigment is 600 nm; analyzed by spectrophotometry, the color value E 1％ 1cm (600 nm) is 321.

[0088] Example 7:

[0089] A method for preparing gardenia blue pigment using the under-column liquid after extracting gardenia yellow, comprising the following steps:

[0090] (1)Removing impurities by copper sulfate precipitation: Take the aqueous ethanol solution obtained by extracting the alcohol-water soluble components including gardenia yellow pigment from gardenia with a 70% aqueous ethanol solution as a solvent, and the aqueous solution obtained by heating and recovering ethanol. After separating the oil-like substances insoluble in water, pass the under-column liquid of 1500 kg flowing out from the lower end of the resin adsorption column that adsorbs gardenia yellow pigment through an adsorption column containing an adsorption resin. Under stirring conditions, add 75 kg of an aqueous copper sulfate solution with a mass percentage concentration of 1.5%, continue stirring for 1.0 hour, then filter through a plate and frame, discard the precipitate to obtain a filtrate for standby;

[0091] (2) Decolorization by potassium permanganate oxidation and removal of excessive copper ions: Take the filtrate obtained in step (1), heat it to 55 °C, and while stirring, adjust the pH to 7.0 with 30% by mass concentration. Add 75 kg of an aqueous potassium permanganate solution with a mass percentage concentration of 5%, control the pH at 7.0, continue stirring for 7 hours, then adjust the pH to 8.5 with 30% by mass concentration, and perform plate and frame filtration. Discard the precipitate to obtain a colorless decolorized supernatant for standby;

[0092] (3) Nanofiltration concentration, filtration, and spray drying: Take the decolorized supernatant obtained in step (2), adjust the pH to 10.5 with 30% by mass concentration, and concentrate it with a nanofiltration membrane device with a molecular weight cut-off of 350 Da until the solid mass percentage concentration of the nanofiltration concentrate is 30%. Discard the nanofiltration permeate to obtain the nanofiltration concentrate. The nanofiltration concentrate is filtered through a plate and frame, and the component precipitate is discarded to obtain a filtrate. The filtrate is spray-dried to obtain a crude geniposide solid for standby;

[0093] (4) Extraction of geniposide with propanol and recrystallization: Add propanol with a mass multiple of 4.5 times that of the crude geniposide solid obtained in step (3), stir and disperse, and heat with reflux of condensed water to 65 °C to dissolve and extract geniposide. Continue stirring and heating for 0.5 hours, then centrifuge while it is hot to obtain a supernatant and a precipitate. Extract the precipitate with propanol for the second and third times, discard the third precipitate, and combine the supernatants extracted three times to obtain a propanol solution of geniposide. Heat and evaporate to recover propanol to obtain a crude geniposide product. Dissolve the crude geniposide product with propanol at 75 °C, perform solid-liquid separation and discard the precipitate to obtain a saturated propanol solution of geniposide. Recrystallize at 0 °C and dry to remove the solvent to obtain 27.1 kg of geniposide fine product for standby;

[0094] (5) Biphasic acid hydrolysis with ethyl acetate: At room temperature, dissolve the geniposide fine product obtained in step (4) with pure water, control the mass percentage concentration of the obtained geniposide aqueous solution to be 15%, perform plate and frame filtration and discard the precipitate to obtain a clear and transparent geniposide aqueous solution. While stirring, add a hydrochloric acid solution, control the hydrochloric acid concentration of the geniposide aqueous solution to be 0.9 M, add ethyl acetate with a mass multiple of 3.0 times that of the geniposide aqueous solution, stir and disperse, control the stirring speed at 45 rpm, heat with reflux of condensed water to 25 °C, continue stirring and heating for 4.0 hours, then perform liquid-liquid separation while it is hot, discard the aqueous phase to obtain an ethyl acetate solvent phase containing genipin. Heat and evaporate to recover ethyl acetate to obtain a crude genipin product. Dissolve the crude genipin product with ethyl acetate at 55 °C, centrifuge and discard the precipitate to obtain a saturated ethyl acetate solution of genipin. Recrystallize at 0 °C and dry to remove the solvent to obtain 15.6 kg of genipin pure product.

[0095] (6) Preparation of pure gardenia blue pigment: Take the pure genipin obtained in step (5), disperse it with pure water into a dispersion with a molar concentration of 0.5 M, heat it to 75 °C under stirring conditions, add solid sodium isoleucinate, control the molar concentration ratio of genipin to sodium isoleucinate to be 1:1, continue heating for 2.5 hours, then perform solid-liquid separation. Spray-dry the supernatant to obtain 24.7 kg of gardenia blue pigment powder product.

[0096] The obtained gardenia blue pigment is a dark blue crystalline solid powder. Determined by HPLC method, the purity of the obtained gardenia blue pigment is 99.5%; determined by full-wavelength scanning method, the maximum absorption wavelength of the obtained gardenia blue pigment is 600 nm; analyzed by spectrophotometry, the color value E 1％ 1cm (600 nm) is 323.

[0097] Example 8:

[0098] A method for preparing gardenia blue pigment using the under-column liquid after extracting gardenia yellow, comprising the following steps:

[0099] (1) Removal of impurities by copper sulfate precipitation: Take the aqueous ethanol solution obtained by extracting the alcohol-water soluble components including gardenia yellow pigment from gardenia using a 70% aqueous ethanol solution as a solvent, the aqueous solution obtained by heating and recovering ethanol, after separating the oil-like substances insoluble in water, pass the under-column liquid flowing out from the lower end of the resin adsorption column that adsorbs gardenia yellow pigment through an adsorption column containing an adsorption resin, and the mixed under-column liquid of 2000 kg of the washing liquid flowing out from the lower end of the resin adsorption column after washing the resin adsorption column that adsorbs gardenia yellow pigment. Under stirring conditions, add 100 kg of an aqueous copper sulfate solution with a mass percentage concentration of 1%, continue stirring for 0.5 hours, then perform plate-and-frame filtration, discard the precipitate to obtain the filtrate for standby;

[0100] (2) Oxidation decolorization by potassium permanganate and removal of excessive copper ions: Take the filtrate obtained in step (1), heat it to a temperature of 65 °C, under stirring conditions, adjust the pH to 7.0 with a mass percentage concentration of 25%, add 80 kg of an aqueous potassium permanganate solution with a mass percentage concentration of 5.0%, control the pH to 7.0, continue stirring for 5.5 hours, then adjust the pH to 8.5 with a mass percentage concentration of 25%, perform plate-and-frame filtration, discard the precipitate to obtain a colorless decolorized supernatant for standby;

[0101] (3) Nanofiltration concentration, filtration, and spray drying: Take the decolorized supernatant obtained in step (2), adjust the pH to 10.5 with a mass percentage concentration of 25%, concentrate it with a nanofiltration membrane device with a molecular weight cut-off of 350 Dalton until the mass percentage concentration of the solids in the nanofiltration concentrate is 20%, discard the nanofiltration permeate, and obtain the nanofiltration concentrate. The nanofiltration concentrate is filtered through a plate and frame filter, and the component precipitate is discarded to obtain the filtrate. The filtrate is spray dried to obtain a crude geniposide solid for standby;

[0102] (4) Extraction of geniposide with propanol and recrystallization: Add propanol at a multiple of 2.5 times the mass of the crude geniposide solid obtained in step (3), stir and disperse, and reflux and heat with condensed water to 75 °C to dissolve and extract geniposide. After continuing to stir and heat for 1.0 hour, centrifuge while it is hot to obtain the supernatant and precipitate. Use propanol to extract the precipitate for the second and third times, discard the precipitate of the third time, and combine the supernatants extracted three times to obtain a propanol solution of geniposide. Heat and evaporate to recover propanol to obtain crude geniposide. Dissolve the crude geniposide with propanol at 70 °C, separate the solid and liquid, discard the precipitate, obtain a saturated propanol solution of geniposide, recrystallize at 0 °C, and dry to remove the solvent to obtain 35.8 kg of geniposide fine product for standby;

[0103] (5) Biphasic acid hydrolysis with ethyl acetate: At room temperature, dissolve the geniposide fine product obtained in step (4) with pure water, control the mass percentage concentration of the obtained geniposide aqueous solution to be 13.5%, filter through a plate and frame filter to discard the precipitate, and obtain a clear and transparent geniposide aqueous solution. Under stirring conditions, add hydrochloric acid solution, control the hydrochloric acid concentration of the geniposide aqueous solution to be 0.4 M, add ethyl acetate at a multiple of 3.0 times the mass of the geniposide aqueous solution, stir and disperse, control the stirring speed to be 25 rpm, reflux and heat with condensed water to 35 °C, continue to stir and heat for 3.5 hours, then separate the liquid while it is hot, discard the aqueous phase, and obtain an ethyl acetate solvent phase containing genipin. Heat and evaporate to recover ethyl acetate to obtain crude genipin. Dissolve the crude genipin with ethyl acetate at 60 °C, centrifuge to separate and discard the precipitate, obtain a saturated ethyl acetate solution of genipin, recrystallize at 0 °C, and dry to remove the solvent to obtain 20.6 kg of genipin pure product.

[0104] (6) Preparation of pure gardenia blue pigment: Take the genipin pure product obtained in step (5), disperse it with pure water into a dispersion with a molar concentration of 0.3 M. Under stirring conditions, heat to 95 °C, add solid sodium isoleucinate, control the molar concentration ratio of genipin to sodium isoleucinate to be 1:1, continue to heat for 1.0 hour, then separate the solid and liquid, and spray dry the supernatant to obtain 32.6 kg of gardenia blue pigment powder product.

[0105] The obtained gardenia blue pigment is a dark blue crystalline solid powder. Determined by HPLC method, the purity of the obtained gardenia blue pigment is 99.6%; determined by full wavelength scanning method, the maximum absorption wavelength of the obtained gardenia blue pigment is 600 nm; analyzed by spectrophotometry, the color value E 1％ 1cm (600 nm) is 329.

[0106] Example 9:

[0107] A method for preparing gardenia blue pigment by using the under-column liquid after extracting gardenia yellow, comprising the following steps:

[0108] (1) Removing impurities by copper sulfate precipitation: Taking 7500 kg of the under-column liquid after extracting gardenia yellow, which is obtained by taking an aqueous solution obtained by extracting water-soluble components including gardenia yellow pigment from gardenia with water as a solvent and flowing out from the lower end of the resin adsorption column after adsorbing gardenia yellow pigment by an adsorption column containing an adsorption resin. Under stirring, adding an aqueous copper sulfate solution with a mass multiple of 750 kg and a mass percentage concentration of 3%. After continuing to stir for 0.75 hours, performing plate and frame filtration, discarding the precipitate to obtain a filtrate for standby;

[0109] (2) Oxidative decolorization with potassium permanganate and removing excessive copper ions: Taking the filtrate obtained in step (1), heating it to a temperature of 70 °C. Under stirring, adjusting the pH to 7.0 with a mass percentage concentration of 30%, adding 375 kg of an aqueous potassium permanganate solution with a mass percentage concentration of 4.5%, controlling the pH at 7.0, continuing to stir for 7 hours, then adjusting the pH to 8.5 with a mass percentage concentration of 30%, performing plate and frame filtration, discarding the precipitate to obtain a colorless decolorized supernatant for standby;

[0110] (3) Nanofiltration concentration, filtration and spray drying: Taking the decolorized supernatant obtained in step (2), adjusting the pH to 10.5 with a mass percentage concentration of 30%, concentrating it with a nanofiltration membrane device with a cut-off molecular weight of 350 Dalton until the solid mass percentage concentration of the nanofiltration concentrate is 20%, discarding the nanofiltration permeate to obtain a nanofiltration concentrate. The nanofiltration concentrate is subjected to plate and frame filtration, discarding the component precipitate to obtain a filtrate. Performing spray drying on the filtrate to obtain a crude geniposide solid for standby;

[0111] (4) Extraction of geniposide with propanol and recrystallization: Add propanol in a mass multiple of 2.75 times that of the crude geniposide solid obtained in step (3), stir and disperse, and heat under reflux with condensing water to 70 °C to dissolve and extract geniposide. After continuing to stir and heat for 1.5 hours, centrifuge while it is hot to obtain a supernatant and a precipitate. Extract the precipitate with propanol for the second and third times, discard the precipitate from the third extraction, combine the supernatants from the three extractions to obtain a propanol solution of geniposide, heat and evaporate to recover propanol to obtain a crude geniposide. Dissolve the crude geniposide with propanol at 75 °C, perform solid-liquid separation and discard the precipitate to obtain a saturated propanol solution of geniposide, recrystallize at 0 °C, and dry to remove the solvent to obtain 37.2 kg of geniposide fine product for standby;

[0112] (5) Biphasic acid hydrolysis with ethyl acetate: At room temperature, dissolve the geniposide fine product obtained in step (4) with pure water, control the mass percentage concentration of the obtained geniposide aqueous solution to be 13.5%, filter through a plate and frame to discard the precipitate to obtain a clear and transparent geniposide aqueous solution. Under stirring conditions, add a hydrochloric acid solution, control the hydrochloric acid concentration of the geniposide aqueous solution to be 0.85 M, add ethyl acetate in a mass multiple of 3.5 times that of the geniposide aqueous solution, stir and disperse, control the stirring speed to be 40 rpm, heat under reflux with condensing water to 35 °C, continue to stir and heat for 2.0 hours, then perform liquid-liquid separation while it is hot, discard the aqueous phase to obtain an ethyl acetate solvent phase containing genipin. Heat and evaporate to recover ethyl acetate to obtain a crude genipin. Dissolve the crude genipin with ethyl acetate at 60 °C, centrifuge to discard the precipitate to obtain a saturated ethyl acetate solution of genipin, recrystallize at 0 °C, and dry to remove the solvent to obtain 21.4 kg of genipin pure product.

[0113] (6) Preparation of pure gardenia blue pigment: Take the genipin pure product obtained in step (5), disperse it with pure water into a dispersion with a molar concentration of 0.25 M. Under stirring conditions, heat to 90 °C, add solid sodium isoleucinate, control the molar concentration ratio of genipin to sodium isoleucinate to be 1:1, continue to heat for 1.5 hours, then perform solid-liquid separation, and spray-dry the supernatant to obtain 34.0 kg of gardenia blue pigment powder product.

[0114] The obtained gardenia blue pigment is a dark blue crystalline solid powder. Determined by HPLC method, the purity of the obtained gardenia blue pigment is 99.7%; determined by full-wavelength scanning method, the maximum absorption wavelength of the obtained gardenia blue pigment is 600 nm; analyzed by spectrophotometry, the color value E 1％ 1cm (600 nm) is 332.

[0115] Example 10:

[0116] A method for preparing gardenia blue pigment using the under-column liquid after extracting gardenia yellow, comprising the following steps:

[0117] (1) Removal of impurities by copper sulfate precipitation: Take 3500 kg of the column effluent after extracting Gardenia yellow from the aqueous solution obtained by using water as a solvent to extract the water-soluble components including Gardenia yellow from Gardenia jasminoides Ellis. Add 175 kg of an aqueous copper sulfate solution with a mass percentage concentration of 2.5% under stirring. After continuing to stir for 1.0 hour, perform plate and frame filtration, discard the precipitate, and obtain the filtrate for standby.

[0118] (2) Oxidation and decolorization with potassium permanganate and removal of excessive copper ions: Take the filtrate obtained in step (1), heat it to a temperature of 50 °C, adjust the pH to 7.0 with a mass percentage concentration of 30%, add 175 kg of an aqueous potassium permanganate solution with a mass percentage concentration of 4.0%, control the pH at 7.0, continue to stir for 5 hours, then adjust the pH to 8.0 with a mass percentage concentration of 30%, perform plate and frame filtration, discard the precipitate, and obtain a colorless decolorized supernatant for standby.

[0119] (3) Nanofiltration concentration, filtration and spray drying: Take the decolorized supernatant obtained in step (2), adjust the pH to 10.0 with a mass percentage concentration of 30%, concentrate it with a nanofiltration membrane device with a cut-off molecular weight of 350 Da until the solid mass percentage concentration of the nanofiltration concentrate is 25%, discard the nanofiltration permeate, and obtain the nanofiltration concentrate. The nanofiltration concentrate is filtered through a plate and frame, discard the component precipitate, and obtain the filtrate. Perform spray drying on the filtrate to obtain a crude geniposide solid for standby.

[0120] (4) Extraction of geniposide with propanol and recrystallization: Add propanol with a mass multiple of 3.5 times that of the crude geniposide solid obtained in step (3), stir and disperse, reflux and heat with condensed water to a temperature of 67.5 °C to dissolve and extract geniposide. After continuing to stir and heat for 2.0 hours, perform hot centrifugation to obtain the supernatant and precipitate. Extract the precipitate with propanol for the second and third times, discard the precipitate of the third time, combine the supernatants extracted three times to obtain a propanol solution of geniposide, heat and evaporate to recover propanol to obtain a crude geniposide product. Dissolve the crude geniposide product in propanol at 75 °C, perform solid-liquid separation to discard the precipitate, obtain a saturated propanol solution of geniposide, perform recrystallization at 0 °C, and dry to remove the solvent to obtain 17.3 kg of geniposide fine product for standby.

[0121] (5)Biphasic acid hydrolysis of ethyl acetate: At room temperature, dissolve the geniposide fine product obtained in step (4) with pure water, control the mass percentage concentration of the obtained geniposide aqueous solution to be 12%, filter through a plate-and-frame filter to discard the precipitate, and obtain a clear and transparent geniposide aqueous solution. Under stirring conditions, add hydrochloric acid solution, control the hydrochloric acid concentration of the geniposide aqueous solution to be 1.0 M, add ethyl acetate with a mass multiple of 3.0 times that of the geniposide aqueous solution, stir and disperse, control the stirring speed to be 40 rpm, reflux and heat with condensed water to a temperature of 35 °C, continue to stir and heat for 4.0 hours, then perform liquid-liquid separation while it is hot, discard the aqueous phase, and obtain an ethyl acetate solvent phase containing genipin. Heat and evaporate to recover ethyl acetate to obtain a genipin crude product. Dissolve the genipin crude product with ethyl acetate at 60 °C, centrifuge to separate and discard the precipitate, obtain a saturated ethyl acetate solution of genipin, recrystallize at 0 °C, dry to remove the solvent, and obtain 9.9 kg of genipin pure product.

[0122] (6)Preparation of pure gardenia blue pigment: Take the genipin pure product obtained in step (5), disperse it with pure water into a dispersion with a molar concentration of 0.3 M. Under stirring conditions, heat to 75 °C, add solid sodium isoleucinate, control the molar concentration ratio of genipin to sodium isoleucinate to be 1:1, continue to heat for 2.0 hours, then perform solid-liquid separation, and spray-dry the supernatant to obtain 15.6 kg of gardenia blue pigment powder product.

[0123] The obtained gardenia blue pigment is a dark blue crystalline solid powder. Determined by HPLC method, the purity of the obtained gardenia blue pigment is 99.5%; determined by full-wavelength scanning method, the maximum absorption wavelength of the obtained gardenia blue pigment is 600 nm; analyzed by spectrophotometry, the color value E 1％ 1cm (600 nm) is 323.

[0124] For those skilled in the art, it is obvious that the present invention is not limited to the details of the above exemplary embodiments, and without departing from the spirit or basic characteristics of the present invention, the present invention can be implemented in other specific forms. Therefore, from any point of view, the embodiments should be regarded as exemplary and non-limiting. The scope of the present invention is defined by the appended claims rather than the above description. Therefore, all changes falling within the meaning and scope of the equivalent elements of the claims are intended to be included in the present invention.

[0125] In addition, it should be understood that although this specification is described according to embodiments, not every embodiment only contains an independent technical solution. This narrative way of the specification is only for clarity. Those skilled in the art should regard the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A method for preparing gardenia blue pigment, characterized in that: The steps include: (1) Precipitation of impurities with copper sulfate: Take the liquid below the column after extracting gardenia yellow from gardenia as the raw material, add 0.05 to 0.1 times the mass percentage of 1 to 3% copper sulfate aqueous solution under stirring, continue stirring for 0.5 to 1 hour, and use copper ions to precipitate acidic polysaccharides, triterpene acids, chlorophyllins, proteins and chlorogenic acid carboxyl-containing impurities in the liquid below the column; Solid-liquid separation, discard the precipitate to obtain the supernatant for later use; (2) Decolorization by potassium permanganate and removal of excess copper ions: The supernatant obtained in step (1) is heated to a temperature of 30 to 70° C., and while stirring, the pH is adjusted to 6.5 to 7.5 with an alkali solution / acid solution, and a 0.5 to 5% potassium permanganate aqueous solution with a mass percentage concentration of 0.02 to 0.05 times the mass of the supernatant is added to control the pH to 6.5 to 7.

5. The chlorophyll, polyphenols, flavonoids, residual gardenia yellow and other colored substances and reducing sugars and chlorogenic acid reducing components in the supernatant are oxidized by potassium permanganate under neutral conditions. After continuing to stir for 3 to 7 hours, the pH is adjusted to 7.5 to 8.5 with an alkali solution / acid solution to produce copper oxide precipitates from excess copper ions, solid-liquid separation is performed, and the precipitate containing manganese dioxide and copper oxide components is discarded to obtain a colorless decolorized supernatant for later use; (3) Nanofiltration concentration, filtration and spray drying: the decolorized supernatant obtained in step (2) is taken, and the pH value is adjusted to 9.5-10.5 with an alkaline solution / acid solution to convert the inherent divalent metal ions of calcium, magnesium and zinc in the decolorized supernatant into calcium hydroxide, magnesium hydroxide and zinc oxide. Geniposide is retained by a nanofiltration membrane device, and inorganic salts and organic salts containing monovalent metal ions, sucrose, other small molecular organic components and water are passed through until the solid mass percentage concentration of the nanofiltration concentrate is 20-30%. The nanofiltration permeate is discarded to obtain a nanofiltration concentrate. The nanofiltration concentrate is separated into solid and liquid, and the precipitate of calcium hydroxide, magnesium hydroxide and zinc oxide is discarded to obtain a supernatant. The supernatant is spray dried to obtain a solid crude product of geniposide for standby use. (4) Extracting geniposide with propanol and recrystallizing: adding propanol in an amount of 2.5 to 4.5 times the mass of the crude solid geniposide obtained in step (3), stirring and dispersing, reflux heating the condensed water to a temperature of 60 to 75° C., continuing stirring and heating for 0.5 to 2.5 hours to dissolve and extract the geniposide, performing solid-liquid separation while hot to obtain a supernatant and a precipitate, extracting the precipitate with propanol for a second and third time, discarding the third precipitate, combining the supernatants of the three extractions to obtain a propanol solution of geniposide, heating and evaporating to recover the propanol, obtaining a crude geniposide, dissolving the crude geniposide with propanol at 70 to 75° C., performing solid-liquid separation and discarding the precipitate, obtaining a saturated propanol solution of geniposide, recrystallizing at 0 to 10° C., drying and removing the solvent, obtaining a fine geniposide for standby use; (5) Ethyl acetate biphasic acid hydrolysis: at room temperature, dissolve the geniposide concentrate obtained in step (4) in pure water, control the mass percentage concentration of the obtained geniposide aqueous solution to be 5-15%, separate the solid and liquid and discard the precipitate to obtain a clear and transparent geniposide aqueous solution, add hydrochloric acid solution under stirring, control the hydrochloric acid concentration of the geniposide aqueous solution to be 0.2-1.0 M, add ethyl acetate in an amount of 1.5-3.5 times the mass of the geniposide aqueous solution, stir and disperse, control the stirring speed to be 20-70 rpm, and reflux the condensed water. The method comprises heating the genipin to a temperature of 25 to 35° C., continuing to stir and heat for 1.0 to 4.0 hours to hydrolyze genipin glycoside into genipin and glucose, dissolving the genipin produced by the hydrolysis in ethyl acetate, performing liquid-liquid separation while hot, discarding the aqueous phase containing glucose and hydrochloric acid, obtaining an ethyl acetate solvent phase containing genipin, heating and evaporating to recover ethyl acetate, obtaining a crude genipin product, dissolving the crude genipin product in ethyl acetate at 50 to 60° C., performing solid-liquid separation and discarding the precipitate, obtaining a saturated ethyl acetate solution of genipin, recrystallizing at 0 to 5° C., drying and removing the solvent, and obtaining a pure genipin product; (6) Preparation of pure gardenia blue pigment: take the pure genipin obtained in step (5), disperse it with purified water into a dispersion with a molar concentration of 0.1 to 0.5 M, heat it to 55 to 95° C. under stirring, add solid sodium isoleucinate, control the molar concentration ratio of genipin to sodium isoleucinate to be 1:1, continue heating for 0.5 to 2.5 hours, so that genipin and sodium isoleucinate react to form gardenia blue pigment, separate the solid and liquid, and spray dry the supernatant to obtain a gardenia blue pigment powder product.

2. A method for preparing a gardenia blue pigment according to claim 1, characterized in that: The column liquid after extracting gardenia yellow in the step (1) is: a. an aqueous solution obtained by extracting water-soluble components including gardenia yellow pigment in gardenia using gardenia as raw material and water as solvent, a liquid flowing out from the lower end of an adsorption column after the gardenia yellow pigment is adsorbed by an adsorption column containing adsorption resin or not, or a mixture of liquids flowing out from the lower end of the resin adsorption column after the resin adsorption column adsorbed with gardenia yellow pigment is washed with water; b. an ethanol aqueous solution obtained by extracting alcohol-water soluble components including gardenia yellow pigment in gardenia using gardenia as raw material and 10-75% ethanol aqueous solution as solvent, a liquid obtained by heating and recovering ethanol, a water solution obtained by separating water-insoluble oily substances, a liquid flowing out from the lower end of a resin adsorption column after the gardenia yellow pigment is adsorbed by an adsorption column containing adsorption resin, or a mixture of liquids flowing out from the lower end of a resin adsorption column after the resin adsorption column adsorbed with gardenia yellow pigment is washed with water.

3. A method for preparing a gardenia blue pigment according to claim 1, characterized in that: The alkali solution in step (2) and step (3) is an aqueous solution of sodium hydroxide or potassium hydroxide of industrial grade, chemically pure, analytically pure, pharmaceutical grade or edible grade; the acid in step (2), step (3) and step (5) is hydrochloric acid of industrial grade, chemically pure, analytically pure, pharmaceutical grade or edible grade; the potassium permanganate in step (2) is potassium permanganate of industrial grade, chemically pure, analytically pure, pharmaceutical grade or edible grade.

4. A method for preparing a gardenia blue pigment according to claim 1, characterized in that: The nanofiltration membrane in step (3) has a molecular weight cutoff of ≤350 Daltons.

5. A method for preparing a gardenia blue pigment according to claim 1, characterized in that: The propanol in step (4) is analytical grade, pharmaceutical grade or food grade propanol.

6. A method for preparing a gardenia blue pigment according to claim 1, characterized in that: The ethyl acetate in step (5) is analytical grade, pharmaceutical grade or food grade ethyl acetate.

7. A method for preparing a gardenia blue pigment according to claim 1, characterized in that: The sodium isoleucine in step (6) is chemically pure, analytically pure, pharmaceutical grade or edible grade sodium isoleucine.

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