Edible natural pigment ink for digital inkjet and preparation method thereof

Abstract

The present application relates to the field of edible ink, especially to the field of C09D11 / 00, and more particularly to an edible natural pigment ink for digital inkjet and a preparation method thereof. The edible natural pigment ink is prepared by using specific preparation raw materials in a specific ratio, including a moisturizing solvent, a quick-drying solvent, a sweetener, a pigment liquid, a color protection agent, a surfactant, a PH regulator, and water, and by using a specific preparation process. The edible natural pigment ink has suitable viscosity and surface tension, the viscosity is 2-5 cps, and the surface tension is 30-34 mN / m. After the process step of digital inkjet, the edible natural pigment ink can be effectively sprayed on the surface of the food material to be sprayed, the conductivity is small, the ink breakage does not occur, the continuous inkjet printing can be realized, the conductivity is low, the inkjet head of the printer is not affected, and the printing inkjet head can work continuously for a long time.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of edible ink, in particular to the field of C09D11 / 00, and more particularly to an edible natural pigment ink for digital inkjet and a preparation method thereof. BACKGROUND

[0002] Some common food products, including bread, chocolate, hard candy, cookies, etc., are coated with some beautiful decorative patterns on the surface of the product, which can often better stimulate the purchasing desire of consumers, especially for children's food, spraying some exquisite decorative patterns can significantly improve the sales of the product. In the field of edible food inkjet ink, the edible safety of the ink is a basic requirement, in addition to this, how to ensure that the pattern can exist stably for a long time without blurring under some high or low temperature environment after the edible ink is jetted on the surface of the food, and how to ensure the efficiency of the inkjet process are also points that the industry is currently concerned about. Due to the physicochemical properties of the food surface and the special nature of the food, it is difficult to achieve high printing clarity and beautiful appearance of the pattern on the food surface by using the existing printing method; at present, the method of digital inkjet is the most widely used, because the ink needs to have certain viscosity to be smoothly sprayed on the surface of the food, therefore, how to ensure the continuity of the inkjet and prevent the clogging of the inkjet head, how to make the inkjet head work for a long time and be quickly cleaned are also technical problems that need to be solved urgently.

[0003] The prior art CN107955451B discloses a preparation method of edible printing ink, mainly including: dissolving cyclodextrin and iron salt in water by ultrasonic, controlling the pH of the aqueous solution to be acidic; adding carbohydrate sweetener, soybean phospholipid and other raw materials for mixing to obtain the ink. The ink prepared by the above formula and process can be well attached to the surface of food with oily spices, anti-sticking agents and other oily substances, without printing defects, and has high edible safety; the prior art CN105209560A discloses an inkjet printing using edible ink, which can effectively print the edible ink on the material; but the above formula and process cannot guarantee the continuity of the inkjet, and the reduction degree of the ink is also affected to a certain extent. SUMMARY

[0004] In order to solve the above technical problems, the present application provides a first aspect of an edible natural pigment ink for digital inkjet, and the preparation raw materials are as follows in terms of mass percentage: 5-20% of moisturizing solvent, 1-10% of quick-drying solvent, 1-15% of sweetener, 10-50% of pigment liquid, 0.1-5% of color protection agent, 0.5-2% of surfactant, 0.1-1% of pH regulator, and the balance of deionized water.

[0005] Preferably, the moisturizing solvent comprises at least one of glycerin, propylene glycol, sorbitol, xylitol, potassium lactate, sodium lactate, lactitol, and maltitol.

[0006] Preferably, the fast-drying solvent comprises at least one of isopropyl alcohol, n-butyl alcohol, and ethanol.

[0007] Further preferably, the weight ratio of the moisturizing solvent to the fast-drying solvent is not less than 2:1.

[0008] Preferably, the sweetener comprises at least one of erythritol, polydextrose, fructose, and maltose.

[0009] Preferably, the preparation raw material of the colorant solution comprises a natural colorant solution.

[0010] Preferably, the natural colorant solution comprises one or more of betacyanin, cochineal carmine, gardenia yellow, turmeric, beta-carotene, gardenia blue, algal blue, and cuttlefish ink.

[0011] Preferably, the preparation method of the colorant solution comprises the following steps: washing the natural colorant solution through a cation chromatography column, washing the natural colorant solution through an anion chromatography column, adjusting the pH of the system to be weakly acidic, and filtering to obtain the colorant solution.

[0012] Preferably, the preparation method of the anion chromatography column is as follows: soaking the resin in the column with an alcohol solution with a concentration of 95wt% or above for 2-4h, then performing column treatment with the same alcohol solution, controlling the treatment flow rate at 100-400mL / h, until the effluent is not turbid when diluted with water in a test tube; then performing column cleaning with pure water, until the ethanol content is less than 1wt% or there is no obvious alcohol smell, and stopping the cleaning, and retaining a liquid surface layer on the resin bed layer to prevent the column from drying.

[0013] Preferably, the preparation method of the cation ion chromatography column is as follows: soaking the resin in the column with an alcohol solution with a concentration of 95wt% or above for 2-4h, then performing column treatment with the same alcohol solution, controlling the treatment flow rate at 100-400mL / h, until the effluent is not turbid when diluted with water in a test tube; then performing column cleaning with pure water, until the ethanol content is less than 1wt% or there is no obvious alcohol smell, and stopping the cleaning, and retaining a liquid surface layer on the resin bed layer to prevent the column from drying.

[0014] Preferably, the washing step of the anion chromatography column comprises: performing column treatment with an alkali solution, controlling the treatment flow rate at 100-400mL / h; after the treatment, performing column cleaning with pure water to remove the alkali remaining in the column bed and resin pores, until the pH of the effluent is less than 10, stopping the water washing, and retaining a certain liquid surface layer on the resin bed layer to prevent the column from drying.

[0015] Preferably, the cleaning step of the cation chromatographic column comprises: using an acid solution to do column treatment again, the treatment flow rate is controlled at 100-400 mL / h: after the treatment is completed, the residual alkali in the column bed and the resin pore channel is washed away by using pure water column cleaning, until the outlet liquid pH<10, stop water washing, at least a certain liquid surface layer is reserved on the resin bed layer to prevent dry column.

[0016] Preferably, the color protection agent comprises one or more of phospholipids, vitamin C, and water-soluble vitamin E.

[0017] Preferably, the surfactant comprises one of Tween 20, Tween 80, monoglyceride fatty acid ester, diglyceride fatty acid ester, polyglycerol fatty acid ester, sucrose fatty acid ester, hydroxypropyl starch, acetylated monoglyceride fatty acid ester, acetylated diglyceride fatty acid ester, alpha cyclodextrin, beta cyclodextrin, and gamma cyclodextrin.

[0018] Preferably, the pH regulator comprises one of citric acid, sodium citrate, potassium citrate, sodium bicarbonate, potassium hydroxide, and sodium hydroxide.

[0019] The second aspect of the embodiment provides a preparation method of edible natural pigment ink for digital inkjet, comprising the following steps:

[0020] S1, mixing and stirring: according to the proportion, deionized water, solvent, surfactant, color protection agent, sweetener, and pH regulator are added into a container, the stirring speed is 500-800 r / min, and the stirring time is 30-90 min, then the pigment solution is added and stirred, the stirring speed is controlled at 800-1000 r / min, and the stirring time is 1-4 h;

[0021] S2, filtering and defoaming: the solution obtained in step S1 is filtered by using a micrometer filter, and then the filtrate is defoamed under the condition that the vacuum degree is 0.06-0.1 MPa, and the defoaming time is 30-60 min;

[0022] S3, sterilization: the defoamed solution is sterilized to obtain edible natural pigment ink, and then the edible natural pigment ink is filled.

[0023] Beneficial effects

[0024] (1) The edible natural pigment ink prepared by the present application has suitable viscosity and surface tension, and can be effectively sprayed on the surface of food to be sprayed after the process of digital inkjet, and the conductivity is low, so that the inkjet printing can be realized continuously, and the low conductivity does not affect the inkjet head, so that the printing head can work continuously for a long time.

[0025] (2) In the present application, the preparation raw materials include specific moisturizing solvent and fast-drying solvent, and the mass ratio of the two is not less than 2:1, which can ensure good printing effect of inkjet, and the printed pattern is clear. If the mass ratio of the moisturizing solvent and the fast-drying solvent is less than 2:1, the conductivity of the edible natural pigment ink will increase, and the phenomenon of broken hole will occur during the actual inkjet printing process, which affects the continuity of printing on the surface of food, thereby affecting the beauty of the printed pattern.

[0026] (3) In the present application, a specific preparation process is adopted, in which the non-pigment liquid raw materials are first mixed and stirred, and then the pigment liquid is added. The ink can be smoothly printed by inkjet. If the pigment liquid and other raw materials are added together, the inventor finds that the pigment liquid will be precipitated, and the ink cannot be printed. Only by mixing and stirring the non-pigment liquid raw materials first, and then adding and stirring the pigment liquid, the compatibility of the pigment liquid in the solution system is good, and the situation of precipitation does not occur, so that the ink can realize normal printing function.

[0027] (4) The present application adds a specific color protection agent, which can ensure that the pattern formed after the ink is sprayed on the surface of food has high stability and obvious improvement in weather resistance. The inventor speculates that the addition of the color protection agent can interact with the pigment liquid to form a more stable spatial molecular structure, and can form intermolecular forces with the surface of the food, so that the pattern will not fade even when placed outdoors.

[0028] (5) In the present application, a specific purification treatment process is adopted for the natural pigment liquid, which can effectively remove anions and cation impurities in the natural pigment liquid system, and improve the purity of the pigment. If the anion and cation column chromatography purification process is not performed, the ion concentration in the natural pigment liquid is high, and the conductivity of the corresponding ink system is high, so that the digital inkjet continuous printing cannot be realized.

[0029] (VI) The edible natural pigment ink prepared by the application has high safety, good adaptability to printers, good on-machine cleaning performance, good continuous printing effect, good printing effect on food, and can avoid the use of preservatives through the sterilization process in the preparation process. In addition, as long as the pigment is selected and the concentration is controlled, the color reduction degree of the pattern printed by the ink is high, the appearance is exquisite and beautiful, and the application in the food field can effectively improve the experience and purchase desire of consumers for the product. BRIEF DESCRIPTION OF DRAWINGS

[0030] Figure 1 The spraying effect diagram of the ink prepared in the example.

[0031] Figure 2 The effect diagram of the ink prepared in the example sprayed on the surface of the paper and placed outdoors for one week, the left half is the appearance effect diagram after printing, and the right half is the appearance effect diagram after printing for one week.

[0032] Figure 3 The effect diagram of the ink prepared in Comparative Example 3 sprayed on the surface of the paper and placed outdoors for one week, the left half is the appearance effect diagram after printing, and the right half is the appearance effect diagram after printing for one week. DETAILED DESCRIPTION

[0033] Example 1

[0034] The first aspect of the embodiment provides an edible natural pigment ink for digital inkjet, and the preparation raw materials are specifically 55.4% deionized water, 15% glycerol, 3% ethanol, 5% fructose, 0.5% vitamin C, 1% alpha-cyclodextrin, 0.1% sodium citrate, and 20% pigment liquid according to mass percentage; the preparation raw materials of the pigment liquid are algal blue and deionized water, and the mass ratio of algal blue to deionized water is 1:9; the specific preparation method of the pigment liquid is: mixing algal blue and deionized water, cleaning through a cation exchange column, cleaning through an anion exchange column, adjusting the pH of the system to 6-7, and filtering with a 0.45 micron filter to obtain the pigment liquid.

[0035] The cation exchange column manufacturing method is:

[0036] Soak the resin in the column with an alcohol solution of 95wt% or more for 2-4h, then use the same alcohol solution for column treatment, control the treatment flow rate at 200mL / h, and stop when the diluted water in the test tube is not turbid. Then use pure water for column cleaning, stop when the ethanol content is less than 1wt% or there is no obvious alcohol smell, and keep a certain liquid level on the resin bed to prevent dry column.

[0037] The anion chromatography column manufacturing method is:

[0038] The column resin is soaked in an alcohol solution with a concentration of 95wt% or above for 2-4h, and then treated with the same alcohol solution at a flow rate of 200mL / h until the effluent is not turbid when diluted with water in a test tube.

[0039] The cleaning step of the anion chromatography column includes: treating the column with a 4wt% sodium hydroxide solution at a flow rate of 200mL / h; after the treatment, washing the column with pure water to remove the residual alkali in the column bed and resin pores until the outlet liquid pH<10, stopping the water washing, and retaining a certain liquid level on the resin bed to prevent the column from drying.

[0040] The cleaning step of the anion chromatography column includes: treating the column with a 4wt% sodium hydroxide solution at a flow rate of 200mL / h; after the treatment, washing the column with pure water to remove the residual alkali in the column bed and resin pores until the outlet liquid pH<10, stopping the water washing, and retaining a certain liquid level on the resin bed to prevent the column from drying.

[0041] The second aspect of the embodiment provides a preparation method of edible natural pigment ink for digital inkjet, which includes the following steps:

[0042] S1, mixing and stirring: add deionized water, glycerol, ethanol, fructose, vitamin C, α-cyclodextrin and sodium citrate into a container, stir at a speed of 600r / min for 60min, then add the pigment solution and stir at a speed of 1000r / min for 2h;

[0043] S2, filtering and defoaming: filter the solution obtained in step S1 using a micrometer filter, and then defoam the filtrate under a vacuum degree of 0.1MPa for 60min;

[0044] S3, sterilization: sterilize the defoamed solution by pasteurization to obtain edible natural pigment ink, and then perform filling and packaging in low-transmittance ink bottles.

[0045] Example 2

[0046] The first aspect of the embodiment provides an edible natural pigment ink for digital inkjet, and the preparation raw materials are specifically as follows in percentage by mass: deionized water 53.1%, glycerol 12%, ethanol 5%, fructose 8%, vitamin C 0.5%, α-cyclodextrin 1%, β-cyclodextrin 0.3%, sodium citrate 0.1%, and pigment liquid 20%; the pigment liquid is prepared from gardenia yellow and deionized water, and the mass ratio of the gardenia yellow to the deionized water is 1:9; and the specific preparation method of the pigment liquid is as follows: the gardenia yellow and the deionized water are mixed, cleaned through a cation exchange column, cleaned through an anion exchange column, adjusted to a pH of 6-7, and filtered through a 0.45-micron filter to obtain the pigment liquid.

[0047] The cation exchange column is prepared by the following method:

[0048] The resin in the column is soaked in an alcohol solution with a concentration of 95wt% or above for 2-4 hours, and then treated with the same alcohol solution at a flow rate of 200mL / h until the effluent is not turbid when diluted with water in a test tube; then the column is cleaned with pure water until the ethanol content is less than 1wt% or there is no obvious alcohol smell, and a certain liquid level is reserved on the resin bed to prevent the column from drying.

[0049] The anion exchange column is prepared by the following method:

[0050] The resin in the column is soaked in an alcohol solution with a concentration of 95wt% or above for 2-4 hours, and then treated with the same alcohol solution at a flow rate of 200mL / h until the effluent is not turbid when diluted with water in a test tube; then the column is cleaned with pure water until the ethanol content is less than 1wt% or there is no obvious alcohol smell, and a certain liquid level is reserved on the resin bed to prevent the column from drying.

[0051] The cleaning step of the anion exchange column is as follows: the column is treated with a 4wt% sodium hydroxide solution at a flow rate of 200mL / h; after the treatment, the column is cleaned with pure water to remove the residual alkali in the column bed and the resin pores until the pH of the effluent is less than 10, and the water cleaning is stopped; and a certain liquid level is reserved on the resin bed to prevent the column from drying.

[0052] The cleaning step of the cation exchange column includes: the column is treated with a 4wt% hydrochloric acid solution at a flow rate of 200mL / h; after the treatment, the column is cleaned with pure water to remove the residual alkali in the column bed and the resin pores until the pH of the effluent is less than 10, and the water cleaning is stopped; and a certain liquid level is reserved on the resin bed to prevent the column from drying.

[0053] The second aspect of the embodiment provides a preparation method of an edible natural pigment ink for digital inkjet, and the method includes the following steps:

[0054] S1, mixing and stirring: add deionized water, glycerol, ethanol, fructose, vitamin C, α-cyclodextrin, β-cyclodextrin, sodium citrate into a container, stirring at 600 r / min for 60 min, then add pigment solution and stir, control the stirring speed at 1000 r / min, and stirring time for 2 h;

[0055] S2, filtering and defoaming: filter the solution obtained in step S1 using a micrometer filter, then defoam the filtrate under the condition of vacuum degree of 0.1 MPa for 60 min;

[0056] S3, sterilization: sterilize the solution after defoaming by adopting pasteurization, to obtain edible natural pigment ink, then perform filling, and the filling bottle is a low-transmittance ink bottle.

[0057] Example 3

[0058] The first aspect of the embodiment provides an edible natural pigment ink for digital inkjet, and the preparation raw materials are specifically as follows in terms of mass percentage: deionized water 40.9%, glycerol 12%, propylene glycol 5%, ethanol 5%, fructose 5%, vitamin C 1%, α-cyclodextrin 1%, sodium citrate 0.1%, and pigment solution 30%; the preparation raw materials of the pigment solution are beet red and deionized water, and the mass ratio of beet red to deionized water is 1:9; and the specific preparation method of the natural pigment is as follows: mix beet red and deionized water, clean by a cation exchange column, clean by an anion exchange column, adjust the pH of the system to 6-7, and filter by a 0.45-micron filter, to obtain the pigment solution.

[0059] The cation exchange column manufacturing method is as follows:

[0060] Soak the resin in the column with an alcohol solution of 95wt% or more for 2-4 h, then perform column treatment with the same alcohol solution, control the treatment flow rate at 200 mL / h, and stop until the effluent is not turbid when diluted with water by one time in a test tube. Then perform column cleaning with pure water, stop when the ethanol content is less than 1wt% or there is no obvious alcohol smell, and retain a certain liquid level on the resin bed layer to prevent dry column.

[0061] The anion exchange column manufacturing method is as follows:

[0062] Soak the resin in the column with an alcohol solution of 95wt% or more for 2-4 h, then perform column treatment with the same alcohol solution, control the treatment flow rate at 200 mL / h, and stop until the effluent is not turbid when diluted with water by one time in a test tube. Then perform column cleaning with pure water, stop when the ethanol content is less than 1wt% or there is no obvious alcohol smell, and retain a certain liquid level on the resin bed layer to prevent dry column.

[0063] The cleaning step of the anion chromatographic column comprises: using 4wt% sodium hydroxide solution to perform column treatment, and the treatment flow rate is controlled at 200mL / h; after the treatment is completed, pure water is used to perform column cleaning to remove the residual alkali in the column bed and the resin pore channel, until the outlet liquid pH is less than 10, the water cleaning is stopped, and at least a certain liquid surface layer is reserved on the resin bed layer to prevent the column from drying.

[0064] The cleaning step of the cation chromatographic column comprises: using 4wt% hydrochloric acid solution to perform column treatment again, and the treatment flow rate is controlled at 200mL / h; after the treatment is completed, pure water is used to perform column cleaning to remove the residual alkali in the column bed and the resin pore channel, until the outlet liquid pH is less than 10, the water cleaning is stopped, and at least a certain liquid surface layer is reserved on the resin bed layer to prevent the column from drying.

[0065] The second aspect of the embodiment provides a preparation method of edible natural pigment ink for digital inkjet, specifically comprising the following steps:

[0066] S1, mixing and stirring: deionized water, glycerol, propylene glycol, ethanol, fructose, vitamin C, α-cyclodextrin and sodium citrate are added into a container, stirring is performed at a speed of 600r / min for 60min, then pigment liquid is added and stirring is performed at a speed of 1000r / min for 2h;

[0067] S2, filtering and defoaming: the solution obtained in the step S1 is filtered by using a micrometer filter, and then the filtrate is defoamed under the condition of a vacuum degree of 0.1MPa for 60min;

[0068] S3, sterilization: the defoamed solution is subjected to sterilization treatment by using pasteurization, and then edible natural pigment ink is obtained, and then filling and packaging are performed, and the packaging bottle is a low-transmittance ink bottle.

[0069] Example 4

[0070] The first aspect of the embodiment provides an edible natural pigment ink for digital inkjet, and the preparation raw materials specifically comprise, in percentage by mass: deionized water 44.9%, glycerol 12%, propylene glycol 3%, ethanol 3%, fructose 5%, vitamin C 1%, α-cyclodextrin 1%, sodium citrate 0.1%, and pigment liquid 30%; the preparation raw materials of the pigment liquid are natural pigment liquid and deionized water, the mass ratio of the natural pigment liquid to the deionized water is 1:9, the natural pigment liquid comprises beet red, gardenia yellow and gardenia blue, and the mass ratio of the three is 4:3:3; the specific preparation method of the pigment liquid comprises the following steps: mixing the natural pigment liquid and the deionized water, cleaning by using a cation chromatographic column, cleaning by using an anion chromatographic column, adjusting the pH of the system to 6-7, and filtering by using a 0.45-micron filter.

[0071] The cation chromatographic column is prepared by the following method:

[0072] Soak the resin in the column with 95wt% or more alcohol solution for 2-4h, then do column treatment with the same alcohol solution, control the treatment flow rate at 200mL / h, until the effluent is not turbid when diluted with water in a test tube; then do column cleaning with pure water, stop cleaning when the ethanol content is less than 1wt% or there is no obvious alcohol smell, keep a certain liquid level on the resin bed to prevent dry column.

[0073] The method for manufacturing the anion chromatography column is:

[0074] Soak the resin in the column with 95wt% or more alcohol solution for 2-4h, then do column treatment with the same alcohol solution, control the treatment flow rate at 200mL / h, until the effluent is not turbid when diluted with water in a test tube; then do column cleaning with pure water, stop cleaning when the ethanol content is less than 1wt% or there is no obvious alcohol smell, keep a certain liquid level on the resin bed to prevent dry column.

[0075] The cleaning step of the anion chromatography column is: do column treatment with 4wt% sodium hydroxide solution, control the treatment flow rate at 200mL / h; after treatment, clean the column bed and resin pores with pure water to remove residual alkali, stop water washing when the outlet liquid pH<10, keep a certain liquid level on the resin bed to prevent dry column.

[0076] The cleaning step of the cation chromatography column includes: do column treatment with 4wt% hydrochloric acid solution again, control the treatment flow rate at 200mL / h; after treatment, clean the column bed and resin pores with pure water to remove residual alkali, stop water washing when the outlet liquid pH<10, keep a certain liquid level on the resin bed to prevent dry column.

[0077] The second aspect of the embodiment provides a preparation method of edible natural pigment ink for digital inkjet, specifically the following steps:

[0078] S1, mixing and stirring: add ionized water, glycerol, propylene glycol, ethanol, fructose, vitamin C, alpha-cyclodextrin and sodium citrate into a container, stir at a speed of 600r / min for 60min, then add pigment solution and stir at a speed of 1000r / min for 2h;

[0079] S2, filter and remove bubbles: filter the solution obtained in step S1 using a micrometer filter, then remove bubbles from the filtrate under a vacuum degree of 0.1MPa for 60min;

[0080] S3, sterilization: sterilize the solution after bubble removal by pasteurization to obtain edible natural pigment ink, then perform filling and packaging, and the packaging bottle is a low-transmittance ink bottle.

[0081] Comparative Example 1

[0082] The first aspect of the comparative example provides an edible natural pigment ink for digital inkjet, and the preparation raw materials are specifically as follows in terms of mass percentage: deionized water 73.4%, glycerol 15%, ethanol 3%, fructose 5%, vitamin C 0.5%, α-cyclodextrin 1%, sodium citrate 0.1%, and natural pigment liquid gardenia blue 2%.

[0083] The second aspect of the embodiment provides a preparation method of the edible natural pigment ink for digital inkjet, and the method specifically includes the following steps:

[0084] S1, mixing and stirring: the deionized water, glycerol, ethanol, fructose, vitamin C, α-cyclodextrin, sodium citrate, and natural pigment liquid gardenia blue are added into a container, the stirring speed is 600 r / min, and the stirring time is 60 min; then the natural pigment liquid gardenia blue is added and stirred, the stirring speed is controlled to be 1000 r / min, and the stirring time is 2 h;

[0085] S2, filtering and defoaming: the solution obtained in the step S1 is filtered by using a micrometer filter, and then the filtrate is defoamed under the condition that the vacuum degree is 0.1 MPa, and the defoaming time is 60 min;

[0086] S3, sterilization: the solution after defoaming is subjected to sterilization treatment by using the pasteurization, to obtain the edible natural pigment ink, and then the ink is filled into bottles, and the bottles are ink bottles with low light transmittance.

[0087] Comparative Example 2

[0088] The specific implementation of the comparative example is the same as that of the embodiment 2, except that the preparation raw materials are specifically as follows in terms of mass percentage: deionized water 71.1%, glycerol 12%, ethanol 5%, fructose 8%, vitamin C 0.5%, α-cyclodextrin 1%, α-cyclodextrin 0.3%, sodium citrate 0.1%, and natural pigment liquid gardenia yellow 2%.

[0089] In the preparation process S1, the specific steps are as follows: the deionized water, glycerol, ethanol, fructose, vitamin C, α-cyclodextrin, sodium citrate, and natural pigment liquid gardenia yellow are added into a container, the stirring speed is 600 r / min, and the stirring time is 60 min.

[0090] Comparative Example 3

[0091] The specific implementation of the comparative example is the same as that of the embodiment 3, except that the preparation raw materials do not include the color protection agent vitamin C, and the mass percentages of the raw materials are as follows: deionized water 55.9%, glycerol 15%, ethanol 3%, fructose 5%, α-cyclodextrin 1%, sodium citrate 0.1%, and pigment liquid 20%.

[0092] Comparative Example 4

[0093] The specific implementation of the comparative example is the same as that of Example 1, except that the preparation raw materials are specifically 55.4% deionized water, 9% glycerol, 9% ethanol, 5% fructose, 0.5% vitamin C, 1% a-cyclodextrin, 0.1% sodium citrate, and 20% pigment liquid, in terms of mass percentage; that is, the mass ratio of the quick-drying solvent and the moisturizing solvent is 1:1.

[0094] Performance test

[0095] 1. Physicochemical parameters: viscosity, surface tension, conductivity, pH; all measured at 25°C and standard atmospheric pressure

[0096] Viscosity and surface tension are the basis for determining whether the ink is suitable for printing, and conductivity is used to judge the continuous printing performance of the ink and the influence of long-term use on the nozzle;

[0097]

[0098]

[0099] The viscosity and surface tension are suitable for printing, and the conductivity of the ink is low.

[0100] 2. Machine printing and cleaning performance, printing equipment: Dian printing technology food printer SY-P-A2C

[0101] Washing 1st Washing 2nd Washing 3rd Example 1 Good condition of spray head Good condition of spray head Good condition of spray head Example 2 1 hole broken Good condition of spray head Good condition of spray head Example 3 3 holes broken Good condition of spray head Good condition of spray head Example 4 1 hole broken Good condition of spray head Good condition of spray head Comparative Example 1 10 holes broken Cannot print Cannot print Comparative Example 2 Cannot print Cannot print Cannot print Comparative Example 3 5 holes broken Good condition of spray head Good condition of spray head Comparative Example 4 3 holes broken Good condition of spray head Good condition of spray head

[0102] Examples 1-4 basically clean the nozzle state within 3 times, and the comparative examples 1 and 2 have poor cleaning state;

[0103] 3. Continuous printing performance on the machine (printing A4 size 100% solid color block)

[0104]

[0105]

[0106] The example continuously prints 100 pages, and the nozzle state is basically intact. The comparative example continuously prints 20 pages, and the line is severely broken and cannot be printed;

[0107] 4. Light resistance effect

[0108] The ink prepared by Examples and Comparative Example 3 is sprayed on paper, and then placed outdoors for one week. The paper surface is observed to be significantly faded, and the details are as indicated in Figure 2 and Figure 3 .

Claims

1. An edible natural colorant ink for digital inkjet printing, characterized by: The preparation raw materials include, by mass percentage: 5-20% of moisturizing solvent, 1-10% of fast-drying solvent, 1-15% of sweetener, 10-50% of colorant liquid, 0.1-5% of color protection agent, 0.5-2% of surfactant, 0.1-1% of pH regulator, and the rest of deionized water; The moisturizing solvent includes at least one of glycerol, propylene glycol, sorbitol, xylitol, potassium lactate, sodium lactate, lactitol, and maltitol; The fast-drying solvent includes at least one of isopropyl alcohol, n-butanol, and ethanol; The weight ratio of the moisturizing solvent to the fast-drying solvent is not less than 2:1; The color protection agent includes one or more of phospholipid, vitamin C, and water-soluble vitamin E; The preparation raw materials of the colorant liquid include natural colorant liquid; The preparation method of the colorant liquid includes the following steps: washing the natural colorant liquid through a cation chromatography column, washing again through an anion chromatography column, adjusting the pH of the system to weak acidity, and filtering to obtain the colorant liquid. The preparation method of the anion chromatography column is: soaking the resin in the column with an alcohol solution of 95wt% or more for 2-4h, then performing column treatment with the same alcohol solution, the treatment flow rate is controlled at 100-400mL / h, until the effluent is not turbid when diluted with water in a test tube; then performing column cleaning with pure water until the ethanol content is less than 1wt% or there is no obvious alcohol smell, and a liquid surface layer is reserved on the resin bed layer to prevent the column from drying out; The preparation method of the cation chromatography column is: soaking the resin in the column with an alcohol solution of 95wt% or more for 2-4h, then performing column treatment with the same alcohol solution, the treatment flow rate is controlled at 100-400mL / h, until the effluent is not turbid when diluted with water in a test tube; then performing column cleaning with pure water until the ethanol content is less than 1wt% or there is no obvious alcohol smell, and a liquid surface layer is reserved on the resin bed layer to prevent the column from drying out; The preparation method of the edible natural colorant ink for digital inkjet includes the following steps: S1, mixing and stirring: adding deionized water, solvent, surfactant, color protection agent, sweetener, and pH regulator into a container according to the proportion, stirring at a speed of 500-800r / min for 30-90min, then adding the colorant liquid and stirring at a speed of 800-1000r / min for 1-4h; S2, filtering and defoaming: filtering the solution obtained in step S1 using a micrometer filter, then defoaming the filtrate under a vacuum degree of 0.06-0.1MPa for 30-60min; S3, sterilization: sterilizing the defoamed solution to obtain the edible natural colorant ink, then filling and sealing.

2. The edible natural colorant ink for digital inkjet according to claim 1, characterized by, The surfactant includes one or more of Tween 20, Tween 80, monoglyceride fatty acid ester, diglycerol fatty acid ester, polyglycerol fatty acid ester, sucrose fatty acid ester, hydroxypropyl starch, acetylated monoglyceride fatty acid ester, acetylated diglycerol fatty acid ester, α-cyclodextrin, β-cyclodextrin, and γ-cyclodextrin.

3. The edible natural colorant ink for digital inkjet according to claim 1, characterized by, The pH adjusting agent includes one or more of citric acid, sodium citrate, potassium citrate, sodium bicarbonate, potassium hydroxide, and sodium hydroxide.

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