Rapid detection method for compound natural pigment

Abstract

The invention discloses a rapid detection method of a compound natural pigment, and belongs to the field of food detection. The method comprises the following specific steps: preparing a compound natural pigment sample as a to-be-detected experimental sample, and preparing a standard sample with the same concentration as the experimental sample; fixing the volume of the experimental sample and the contrast sample by using water or an organic solvent, then filtering by using a filter, and keeping the filtrate for later use; pouring the filtrate into a glass cuvette, setting a wavelength range, scanning, and testing by taking experimental water or an organic solvent as a blank to obtain the maximum absorbance under the characteristic wavelength of the sample; comparing the maximum absorbance of the experimental sample with the maximum absorbance of the standard sample; meanwhile, the pH values of the standard sample solution and the experimental sample solution are measured and compared, so that whether the concentration of the compound natural pigment of the experimental sample and the type of the pigment are correct or not is determined. According to the rapid detection method for the compound natural pigment, provided by the invention, the detection object is expanded, the detection accuracy is improved, and whether the concentration of the natural pigment of a final product and related materials meet the product requirements or not can be determined.

Description

Technical Field

[0001] The present application relates to the field of food detection, and more specifically to a quick detection method for compound natural pigments disclosed by the present invention. Background Art

[0002] Natural pigments are compounds extracted from nature with coloring functions, and are widely used in food, cosmetics, medicine and other fields. Compared with artificial synthetic pigments, natural pigments are safer, healthier and more environmentally friendly, and meet the needs of modern consumers for safe and healthy products. However, the chemical composition of natural pigments is complex, and the color tone is relatively single. In practical applications, compounding is often required to meet diverse color requirements. Compounding natural pigments is to mix multiple natural pigments in a certain proportion to achieve specific color effects and stability requirements. Especially in the field of food, natural pigments are widely used. In recent years, with the advancement of science and technology and consumers' pursuit of natural and healthy products, the research and application of natural pigments have made significant progress. In terms of detection methods, traditional spectrophotometry, liquid chromatography, gas chromatography, etc. have been widely used in the quantitative analysis of natural pigments.

[0003] However, for the detection of compound natural pigments, traditional methods often have problems such as complex operation, long time consumption, and high cost. Especially when the compound system contains multiple components and the content difference is large, it is difficult for traditional methods to quickly and accurately achieve qualitative and quantitative analysis of each component. For compound natural production enterprises, due to negligence and mistakes made by staff during the production process, wrong materials or inconsistent proportions may occur, resulting in the color and concentration of the final product not meeting the requirements. According to GB26687-2011 "General Rules for Compound Food Additives of National Food Safety Standard", the relevant content of the general rules for compound food additives only has requirements for sensory organs, harmful substances (lead, arsenic) and pathogenic microorganisms, that is, there are only safety indicators, no content and other related requirements.

[0004] In the prior art, CN115015402B discloses a method for determining the content of three kinds of shikonin-type natural pigments in food, wherein the shikonin-type natural pigments are shikonin red, acetylshikonin, and deoxyshikonin. CN114858943B discloses a method for detecting the content of animal-derived natural pigments in food, wherein the animal-derived natural pigment is lac red pigment, and both are directed to detecting a single natural pigment. In addition, there is no relevant national standard for the detection of compound natural pigments at this stage. The national standard only determines the color value of a single natural pigment. Therefore, developing a fast and accurate method for detecting compound natural pigments has important practical significance and application value. Summary of the invention

[0005] The existing natural pigment detection method is to measure the color value by ultraviolet spectrophotometer, which can only be used for a single pigment and the calculation can be performed after setting a fixed wavelength. The present invention measures the absorbance after mixing multiple natural pigments (compounded natural colorants), and determines the maximum absorption value of the characteristic wavelength of the standard sample to confirm whether the concentration of the compounded natural pigment and the type of pigment are correct.

[0006] The present invention provides a quick detection method for compound natural pigments. The present invention determines the wavelength range by using the maximum absorption value after superposition of different absorption wavelengths of compound natural pigments, confirms the absorption wavelength range of a certain compound natural pigment absorbance after superposition, thereby confirming the absorption value of the compound natural pigment, and confirms the concentration value according to the absorption value. In future production detection of the compound natural pigment, the absorption value is determined by setting a wavelength range, and according to the absorption value and wavelength range, by comparing with the characteristic wavelength and absorption value of the standard comparison sample, it can be confirmed whether the raw material and the concentration of the compound natural pigment are correct.

[0007] Each natural pigment has a fixed wavelength of maximum absorption, for example: cochineal red is 494nm; gardenia blue is 595nm; beta-carotene is 450nm. However, when two or more natural pigments are compounded, the absorbance values ​​of the compounded natural pigment (also called compounded natural colorant) are superimposed, and the maximum absorption value will be displayed in a wavelength range different from the previous one. Therefore, by measuring the various standard compounded natural pigments produced by the company, a series of data, including absorption wavelength range, maximum absorption value, etc., are obtained as a standard comparison solution for compounded natural pigments to determine whether the final product meets the concentration requirements and pigment type requirements.

[0008] The specific technical solutions of the present invention are as follows:

[0009] A quick detection method for natural pigments, characterized in that it comprises the following steps:

[0010] (1) preparing a composite natural pigment sample as an experimental sample to be tested, and preparing a standard sample with the same concentration as the experimental sample;

[0011] (2) Using water or organic solvent to make up the volume of the composite natural pigment sample and standard sample;

[0012] (3) Filter the sample after volume adjustment using a filter, and reserve the filtrate for later use;

[0013] (4) Pour the filtrate into a glass cuvette, set the wavelength range and scan, and test with experimental water or organic solvent as blank to obtain the maximum absorbance at the characteristic wavelength of the sample; compare the maximum absorbance of the experimental sample with the maximum absorbance of the standard sample to confirm whether the pigment concentration in the compound natural pigment of the experimental sample is correct.

[0014] Furthermore, the preparation process of the composite natural pigment (natural bright red pigment) in step (1) comprises:

[0015] 1) Add weighed butyl hydroxyanisole and butylated hydroxytoluene to weighed soybean oil, heat to 180° C. in a mixing tank 1, then add β-carotene, heat to 180° C. and keep warm for 3 minutes, and cool to about 90° C. to obtain part A;

[0016] 2) Weigh glycerol, lactic acid glyceride, diacetyl tartaric acid mono- and diglyceride, mono- and diglycerol fatty acid esters, modified soybean lecithin, locust bean gum, sodium carboxymethyl cellulose, xanthan gum, and guar gum and add them into a mixing tank 2, heat to 75° C. and keep warm, stir until completely dissolved, and obtain part B;

[0017] 3) Add carmine, sodium D-isoascorbate and sodium hexametaphosphate into water, and stir and dissolve them uniformly in a stirring tank 3 to obtain part C;

[0018] 4) Slowly pour part A into part B, and stir the part in mixing tank 2 with high-speed shear for 20 minutes until it is uniform;

[0019] 5) Add part C into the above mixing tank 2 and stir at high speed for 10 minutes, then pass through a homogenizer at a pressure of 45 MPa and discharge.

[0020] Furthermore, the preparation process of the composite natural pigment (natural taro purple pigment) in step (1) includes:

[0021] 1) Weigh glycerol, lactic acid glyceride, diacetyl tartaric acid mono- and diglyceride, mono- and diglyceride fatty acid esters, modified soybean lecithin, locust bean gum, sodium carboxymethyl cellulose, xanthan gum, and guar gum and add them into a mixing tank 2, heat to 75° C. and keep warm, stir until completely dissolved, and obtain part A;

[0022] 2) Add cochineal red, gardenia blue, sodium D-isoascorbate and sodium hexametaphosphate into water, stir and dissolve evenly in a stirring tank 3 to obtain part B;

[0023] 3) Slowly pour part A into part B, and stir the part in mixing tank 2 with high-speed shear for 20 minutes until it is uniform;

[0024] 4) Add part C into the above mixing tank 2 and stir at high speed for 10 minutes, then pass through a homogenizer at a pressure of 45 MPa and discharge.

[0025] Furthermore, the compound natural pigment in step (1) includes: natural scarlet pigment or natural taro purple pigment.

[0026] Furthermore, the natural scarlet pigment includes cochineal red, β-carotene, soybean oil, glycerol, butylated hydroxyanisole, butylated hydroxytoluene, lactic acid fatty acid glyceride, diacetyl tartaric acid mono- and diglyceride, mono- and diglycerol fatty acid esters, modified soybean lecithin, locust bean gum, sodium carboxymethyl cellulose, xanthan gum, guar gum, sodium D-isoascorbate, sodium hexametaphosphate, and water.

[0027] Furthermore, the pigment content of the natural scarlet pigment is selected to be in the range of 1.5%-2.5%.

[0028] Furthermore, the 1.5% natural scarlet pigment is compounded by 1.45% cochineal carmine and 0.05% beta-carotene.

[0029] Furthermore, the 2.0% natural scarlet pigment is compounded by 1.82% cochineal carmine and 0.18% beta-carotene.

[0030] Furthermore, the 2.5% natural scarlet pigment is compounded by 2.25% cochineal carmine and 0.25% beta-carotene.

[0031] Furthermore, the natural taro purple pigment includes cochineal red, gardenia blue, glycerol, lactic acid fatty acid glyceride, diacetyl tartaric acid mono- and diglyceride, mono- and diglycerol fatty acid esters, modified soybean lecithin, locust bean gum, sodium carboxymethyl cellulose, xanthan gum, guar gum, sodium D-isoascorbate, sodium hexametaphosphate, and water.

[0032] Furthermore, the pigment content of the natural taro purple pigment is selected to be in the range of 5.0%-9.5%.

[0033] Furthermore, the 5.0% natural taro purple pigment is compounded by 1.0% cochineal carmine and 4.0% gardenia blue.

[0034] Furthermore, the 7.5% natural taro purple pigment is compounded by 2.0% cochineal carmine and 5.5% gardenia blue.

[0035] Furthermore, the 9.5% natural taro purple pigment is compounded by 2.5% cochineal carmine and 7.0% gardenia blue.

[0036] Furthermore, in the step (2), 1 g of the composite natural pigment sample is weighed, added to a 100 ml volumetric flask, and diluted to 100 ml with water; 10.0 ml is taken from the diluted solution and added to another 100 ml volumetric flask, and diluted to 100 ml with water, and the solution concentration is 1 mg / ml.

[0037] Furthermore, in step (3), a water filter with a filter membrane of 0.45 μm is used for filtration, and the filtrate is reserved for later use.

[0038] Furthermore, in step (4) of the test for natural scarlet pigment, the filtrate is poured into a glass cuvette with a diameter of 1 cm, the wavelength range is set to 450-580 nm, and the interval scanning is 10 nm; the wavelength scanning function is turned on to obtain the maximum absorbance at the characteristic wavelength, and the absorbance is controlled between 0.2-0.8.

[0039] Furthermore, in step (4) of the test on natural taro purple pigment, the filtrate was poured into a glass cuvette with a diameter of 1 cm, the wavelength range was set to 490-600 nm, and the interval scanning was 10 nm; the wavelength scanning function was turned on to obtain the maximum absorbance at the characteristic wavelength, and the absorbance was controlled between 0.2-0.8.

[0040] At the same time, those skilled in the art know that natural scarlet pigment and natural taro purple pigment will have different states at different pH values. Under acidic conditions, natural scarlet pigment and natural taro purple pigment will precipitate and lighten in color. Only under alkaline conditions will natural scarlet pigment and natural taro purple pigment present a uniform state. Among them, after testing, the pH values ​​of the standard natural scarlet pigments with concentrations of 1.5%, 2.0%, and 2.5% are set to be within the range of 8.68 ± 0.1, 8.64 ± 0.1, and 8.60 ± 0.1 (i.e., the allowable deviation is ± 0.1), respectively, and the test sample is determined to meet the requirements. After testing, the pH values ​​of the standard natural taro purple pigments with concentrations of 5% to 9.5% are set to be within the range of 8.46 ± 0.1, 8.51 ± 0.1, and 8.30 ± 0.1 (i.e., the allowable deviation is ± 0.1), respectively, and the test sample is determined to meet the requirements. When both the absorbance and the pH value must meet the requirements within the standard deviation at the same time, it can be finally confirmed that the test sample meets the requirements.

[0041] The beneficial technical effects of the present invention are as follows:

[0042] (1) The present invention improves the flexibility and applicability of detection. The present invention is not only applicable to the detection of a single natural pigment, but is more applicable to the detection of compound natural pigments, which is of great significance in practical applications. The present invention uses the maximum absorption value after the different absorption wavelengths of the compound natural pigments are superimposed to determine the wavelength range, thereby comparing a series of experimental data to determine whether the product has a maximum absorption value within the wavelength range and whether the absorption value is within the specified concentration range. In addition, by adjusting the wavelength range and scanning parameters, the present invention can also be flexibly applied to the detection of different types of natural pigments, thereby enhancing the versatility and applicability of the detection method.

[0043] (2) The present invention improves detection efficiency and accuracy. Traditional natural pigment detection methods often involve complex extraction, separation and purification steps, which are time-consuming and cumbersome to operate, and are prone to errors. The present invention greatly simplifies the detection process and shortens the detection cycle by directly performing spectral scanning on the composite natural pigment sample after volume adjustment and filtration. At the same time, by using a spectrometer to scan within a specific wavelength range, the characteristic absorption peak of the natural pigment can be accurately captured, thereby accurately determining its maximum absorbance value. In addition, while measuring the absorbance, the pH value of the standard sample is set, the pH value of the test sample is simultaneously determined, and compared with the standard sample. Through two-dimensional detection, it is finally confirmed that the test sample meets the requirements, thereby improving the accuracy and reliability of the detection. This fast and efficient detection method helps companies quickly respond to market demand and improve product quality control efficiency.

[0044] (3) The present invention reduces the cost of testing. Compared with traditional methods, the present invention reduces the amount of chemical reagents used and the need for complex instruments and equipment, such as reducing the consumption of organic solvents and multiple extraction and separation steps, thereby reducing the material cost and labor cost in the testing process. In addition, by standardizing the operating procedures and simplifying the steps, the testing process is easier to master and popularize, reducing the dependence on professional technicians and further reducing the overall testing cost. This is particularly important for small and medium-sized enterprises, as it helps them improve their competitiveness and expand their market share.

[0045] (4) The present invention reduces the pollution of detection reagents. The present invention reduces the emission of harmful substances such as organic solvents by optimizing the detection process, thereby reducing the pollution to the environment. At the same time, due to the simplification of the detection process, the amount of waste treatment is also reduced accordingly, which reduces the cost of sewage treatment and reduces environmental pollution. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Figure 1 Flow chart of the quick detection method of compound natural pigments described in the present invention DETAILED DESCRIPTION

[0047] In order to further explain the technical means and effects adopted by the present application to achieve the predetermined purpose, the specific implementation methods, structures, features and effects of the present application are described in detail below in combination with the accompanying drawings and preferred embodiments.

[0048] The specific embodiments of the present invention are further described below. It should be noted that the description of these embodiments is used to help understand the present invention, but does not constitute a limitation of the present invention. In addition, the technical features involved in each embodiment of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0049] Unless otherwise specified, the test materials used in the following examples can be purchased through conventional commercial channels.

[0050] Example 1

[0051] 1. Reagents and Materials

[0052] Experimental water (secondary water specified in GB / T 6682), cochineal, β-carotene, soybean oil, glycerol, butylated hydroxyanisole, butylated hydroxytoluene, lactic acid glyceryl esters of fatty acids, diacetyl tartaric acid mono- and diglycerol esters, mono- and diglycerol fatty acid esters, modified soybean lecithin, locust bean gum, sodium carboxymethyl cellulose, xanthan gum, guar gum, sodium D-isoascorbate, sodium hexametaphosphate; cochineal, gardenia blue, glycerol, lactic acid glyceryl esters of fatty acids, diacetyl tartaric acid mono- and diglycerol esters, mono- and diglycerol fatty acid esters, modified soybean lecithin, locust bean gum, sodium carboxymethyl cellulose, xanthan gum, guar gum, sodium D-isoascorbate, sodium hexametaphosphate.

[0053] 2. Instruments and Equipment

[0054] Mixing tank

[0055] High speed shear mixing cylinder

[0056] High pressure homogenizer

[0057] 3. Method Step (1) The preparation process of compounding natural pigment (natural scarlet pigment) includes:

[0058] a. Add the weighed butyl hydroxyanisole and butylated hydroxytoluene to the weighed soybean oil, heat to 180°C in a mixing tank 1, then add β-carotene, heat to 180°C for 3 minutes, and cool to about 90°C to obtain part A;

[0059] b. Weigh glycerol, lactic acid glycerol esters, diacetyl tartaric acid mono- and diglycerol esters, mono- and diglycerol fatty acid esters, modified soybean lecithin, locust bean gum, sodium carboxymethyl cellulose, xanthan gum, and guar gum and add them to a stirring tank 2, raise the temperature to 75 ° C and keep warm, stir until completely dissolved to obtain part B;

[0060] c. Add cochineal red, sodium D-isoascorbate and sodium hexametaphosphate to water and stir to dissolve evenly in a stirring tank 3 to obtain part C;

[0061] d. Slowly pour part A into part B, and stir the part in mixing tank 2 for 20 minutes at high speed until it is uniform;

[0062] e. Add part C to the above mixing tank 2 and stir at high speed for 10 minutes, then pass it through a homogenizer at a pressure of 45MPa and discharge it.

[0063] (2) The preparation process of the compound natural pigment (natural taro purple pigment) includes:

[0064] a. Weigh glycerol, lactic acid glycerol esters, diacetyl tartaric acid mono- and diglycerol esters, mono- and diglycerol fatty acid esters, modified soybean lecithin, and acacia

[0065] Add soybean gum, sodium carboxymethyl cellulose, xanthan gum and guar gum into mixing tank 2, raise the temperature to 75°C and keep warm, stir until completely dissolved, and obtain part A;

[0066] b. The carmine, gardenia blue, D-sodium isoascorbate, sodium hexametaphosphate were added to water and stirred in a stirring tank 3 to dissolve evenly to obtain part B;

[0067] c. Slowly pour part A into part B, and stir the part in mixing tank 2 with high-speed shear for 20 minutes until it is uniform;

[0068] d. Add part C to the above mixing tank 2 and stir at high speed for 10 minutes, then pass it through a homogenizer at a pressure of 45 MPa and discharge it.

[0069] Example 2

[0070] 1. Reagents and Materials

[0071] Experimental water (secondary water specified in GB / T 6682)

[0072] 2. Instruments and Equipment

[0073] Electronic balance, sensitivity is 0.001g.

[0074] UV spectrophotometer (with multi-wavelength scanning function)

[0075] 100ml volumetric flask (Grade A)

[0076] 0.45μm water filter

[0077] 3. Standard comparison samples

[0078] The standard natural pigments, cochineal red and β-carotene, are purchased through conventional commercial channels. After compounding, products with relevant concentrations are obtained as standard comparison samples, namely, standard natural scarlet pigments.

[0079] The standard natural scarlet pigment includes: carmine, carotene, glycerin, and water; that is, the natural scarlet pigment is compounded by carmine and β-carotene; the content range of the natural scarlet pigment is 1.5%-2.5%. The 1.5% natural scarlet pigment is compounded by 1.45% carmine and 0.05% β-carotene. The 2.0% natural scarlet pigment is compounded by 1.82% carmine and 0.18% β-carotene. The 2.5% natural scarlet pigment is compounded by 2.25% carmine and 0.25% β-carotene.

[0080] 4. Testing experimental samples

[0081] Prepare a compound natural pigment X containing natural scarlet pigment to be tested.

[0082] 4. Methods and Steps

[0083] (1) A composite natural pigment sample X containing natural scarlet pigment is prepared as a test sample to be tested, and its concentration is 1.0 mg / ml. Three groups of standard samples with the same concentration as the test sample are prepared at the same time. The contents of natural scarlet pigment in the three groups of standard composite natural pigments are 1.5%, 2.0% and 2.5%, respectively; wherein the 1.5% natural scarlet pigment is compounded from 1.45% carmine and 0.05% β-carotene; the 2.0% natural scarlet pigment is compounded from 1.82% carmine and 0.18% β-carotene; and the 2.5% natural scarlet pigment is compounded from 2.25% carmine and 0.25% β-carotene.

[0084] (2) For the composite natural pigment sample and the comparative sample, dilute to volume with water or organic solvent: take 1 g of the composite natural pigment sample, add it to a 100 ml volumetric flask, and dilute to 100 ml with water; take 10.0 ml from the dilute solution and put it into another 100 ml volumetric flask, dilute to 100 ml with water, and the solution concentration is 1 mg / ml.

[0085] (3) Filter the sample after volume adjustment using a water filter with a membrane of 0.45 μm and keep the filtrate for later use.

[0086] (4) Pour the filtrate into a 1 cm diameter glass cuvette, set the wavelength range to 450-580 nm, scan at intervals of 10 nm;

[0087] Turn on the wavelength scanning function to obtain the maximum absorbance at the characteristic wavelength, and the absorbance is controlled between 0.2-0.8; at the same time, test with experimental water or organic solvent as blank to obtain the absorbance at the characteristic wavelength of the sample, where the absorbance of the standard compound natural pigment is shown in Table 1; experimental sample; compare the maximum absorbance of the experimental sample with the maximum absorbance of the standard sample to confirm whether the pigment concentration in the compound natural pigment of the experimental sample is correct.

[0088] Table 1

[0089]

[0090]

[0091] As shown in Table 1, the maximum absorption value of the 2.5% natural crimson pigment standard sample is the absorbance at a wavelength of 520nm, i.e. 0.751. Assuming that the absorbance of the composite natural pigment X containing natural crimson pigment to be detected at 520nm is X1, then when X1=0.751±0.02 (i.e. the allowable deviation of X1 is ±0.02), it can be confirmed that the pigment concentration in the composite natural pigment of the experimental sample is correct.

[0092] As shown in Table 1, the maximum absorption value of the 2.0% natural scarlet pigment standard sample is the absorbance at a wavelength of 520nm, i.e. 0.574. Assuming that the absorbance of the composite natural pigment X containing natural scarlet pigment to be detected at 520nm is X2, then when X2=0.574±0.02 (i.e. the tolerance of X2 is ±0.02), it can be confirmed that the pigment concentration in the composite natural pigment of the experimental sample is correct.

[0093] As shown in Table 1, the maximum absorption value of the 1.5% natural crimson pigment standard sample is the absorbance at a wavelength of 520nm, i.e. 0.439. Assuming that the absorbance of the composite natural pigment X containing natural crimson pigment to be detected at 520nm is X3, then when X3=0.439±0.02 (i.e. the allowable deviation of X3 is ±0.02), it can be confirmed that the pigment concentration in the composite natural pigment of the experimental sample is correct.

[0094] Example 3

[0095] 1. Reagents and Materials

[0096] Experimental water (secondary water specified in GB / T 6682)

[0097] 2. Instruments and Equipment

[0098] Electronic balance, sensitivity is 0.001g.

[0099] UV spectrophotometer (with multi-wavelength scanning function)

[0100] 100ml volumetric flask (Grade A)

[0101] 0.45μm water filter

[0102] 3. Standard comparison samples

[0103] The standard natural pigments, cochineal red and gardenia blue, were purchased through conventional commercial channels. After compounding, products with relevant concentrations were obtained as standard comparison samples, namely, standard natural taro purple pigment.

[0104] The standard natural taro purple pigment includes: carmine, gardenia blue, glycerin, and water; that is, the natural taro purple pigment is compounded by two natural pigments, carmine and gardenia blue; the content range of the natural taro purple pigment is selected to be 5.0%-9.5%. The 5.0% natural taro purple pigment is compounded by 1.0% carmine and 4.0% gardenia blue. The 7.5% natural taro purple pigment is compounded by 2.0% carmine and 5.5% gardenia blue. The 9.5% natural taro purple pigment is compounded by 2.5% carmine and 7.0% gardenia blue.

[0105] 4. Testing experimental samples

[0106] Prepare the compound natural pigment Y containing natural taro purple pigment to be tested.

[0107] 4. Methods and Steps

[0108] (1) Prepare a composite natural pigment sample Y containing natural taro purple pigment as the experimental sample to be tested, and configure its concentration to 1.0 mg / ml. At the same time, prepare three groups of standard samples with the same concentration as the experimental sample, and the contents of natural red pigment in the three groups of standard composite natural pigments are 5.0%, 7.5% and 9.5% respectively; wherein the 5.0% natural taro purple pigment is compounded by 1.0% carmine and 4.0% gardenia blue. The 7.5% natural taro purple pigment is compounded by 2.0% carmine and 5.5% gardenia blue. The 9.5% natural taro purple pigment is compounded by 2.5% carmine and 7.0% gardenia blue.

[0109] (2) For the composite natural pigment sample and the comparative sample, dilute to volume with water or organic solvent: take 1 g of the composite natural pigment sample, add it to a 100 ml volumetric flask, and dilute to 100 ml with water; take 10.0 ml from the dilute solution and put it into another 100 ml volumetric flask, dilute to 100 ml with water, and the solution concentration is 1 mg / ml.

[0110] (3) Filter the sample after volume adjustment using a water filter with a membrane of 0.45 μm and keep the filtrate for later use.

[0111] (4) Pour the filtrate into a 1 cm diameter glass cuvette, set the wavelength range to 490-600 nm, and scan at intervals of 10 nm.

[0112] Turn on the wavelength scanning function to obtain the maximum absorbance at the characteristic wavelength, and the absorbance is controlled between 0.2-0.8; at the same time, test with experimental water or organic solvent as blank to obtain the absorbance at the characteristic wavelength of the sample, where the absorbance of the standard compound natural pigment is shown in Table 2; experimental sample; compare the maximum absorbance of the experimental sample with the maximum absorbance of the standard sample to confirm whether the pigment concentration in the compound natural pigment of the experimental sample is correct.

[0113] Table 2

[0114]

[0115] As shown in Table 2, the maximum absorption value of the 9.5% natural taro purple pigment standard sample is the absorbance value at a wavelength of 560nm, that is, 0.712. Assuming that the absorbance of the composite natural pigment Y containing natural taro purple pigment to be detected at 560nm is Y1, when Y1=0.712±0.02 (i.e., the allowable deviation of Y1 is ±0.02), it can be confirmed that the pigment concentration in the composite natural pigment of the experimental sample is correct.

[0116] As shown in Table 2, the maximum absorption value of the 7.5% natural taro purple pigment standard sample is the absorbance value at a wavelength of 560nm, that is, 0.391. Assuming that the absorbance of the composite natural pigment Y containing natural taro purple pigment to be detected at 560nm is Y2, when Y2=0.439±0.01 (i.e., the allowable deviation of Y2 is ±0.01), it can be confirmed that the pigment concentration in the composite natural pigment of the experimental sample is correct.

[0117] As shown in Table 2, the maximum absorption value of the 5.0% natural taro purple pigment standard sample is the absorbance value at a wavelength of 560nm, that is, 0.263. Assuming that the absorbance of the composite natural pigment Y containing natural taro purple pigment to be detected at 560nm is Y3, when Y3=0.263±0.01 (i.e., the allowable deviation of Y3 is ±0.01), it can be confirmed that the pigment concentration in the composite natural pigment of the experimental sample is correct.

[0118] In order to ensure the validity of the test data, if the absorbance Y of the sample to be tested is ≥0.400, the allowable deviation is ±0.02; if the absorbance Y is <0.400, the allowable deviation is ±0.01.

[0119] Example 4

[0120] 1. Reagents and Materials

[0121] Experimental water (secondary water specified in GB / T 6682), phthalate buffer solution with pH = 4.00, phosphate buffer solution with pH = 6.86, tetraborate buffer solution with pH = 9.18

[0122] 2. Instruments and Equipment

[0123] pH meter (accuracy 0.01)

[0124] Composite electrode: composed of a glass indicator electrode and an Ag / AgCl or Hg2Cl2 reference electrode

[0125] Magnetic stirrer

[0126] 3. Standard comparison samples

[0127] (1) Standard natural scarlet pigments are purchased through conventional commercial channels: cochineal red and β-carotene. After compounding, products with relevant concentrations are obtained as standard comparison samples, i.e., standard natural scarlet pigments.

[0128] The standard natural scarlet pigment includes: carmine, carotene, glycerin, and water; that is, the natural scarlet pigment is compounded by carmine and β-carotene; the content range of the natural scarlet pigment is 1.5%-2.5%. The 1.5% natural scarlet pigment is compounded by 1.45% carmine and 0.05% β-carotene. The 2.0% natural scarlet pigment is compounded by 1.82% carmine and 0.18% β-carotene. The 2.5% natural scarlet pigment is compounded by 2.25% carmine and 0.25% β-carotene.

[0129] (2) Standard natural taro purple pigment is purchased through conventional commercial channels: cochineal carmine and gardenia blue, and after compounding, a product of relevant concentration is obtained as a standard comparison sample, namely, standard natural taro purple pigment. The standard natural taro purple pigment includes: cochineal carmine, gardenia blue, glycerin, and water; that is, the natural taro purple pigment is compounded by two natural pigments, cochineal carmine and gardenia blue; the content range of the natural taro purple pigment is selected to be 5.0%-9.5%. The 5.0% natural taro purple pigment is compounded by 1.0% cochineal carmine and 4.0% gardenia blue. The 7.5% natural taro purple pigment is compounded by 2.0% cochineal carmine and 5.5% gardenia blue. The 9.5% natural taro purple pigment is compounded by 2.5% cochineal carmine and 7.0% gardenia blue.

[0130] 4. Testing experimental samples

[0131] A compound natural pigment X containing natural scarlet pigment to be tested and a compound natural pigment Y containing natural taro purple pigment to be tested.

[0132] 3. Determination

[0133] 3.1 Calibration of pH meter

[0134] The pH meter is calibrated with two buffer solutions of precise pH (as close as possible to the pH of the solution to be measured) at the measuring temperature while stirring with a magnetic stirrer.

[0135] 3.2 Determination of samples

[0136] Take a certain amount of sample that can immerse the electrode, insert the electrode into the sample, and keep the temperature within the range of 20±2℃. Turn on the magnetic stirrer, and read the reading directly after the reading is stable.

[0137] After measurement, the data are shown in Table 3:

[0138] Table 3

[0139]

[0140] As shown in Table 3, it is assumed that the pH value of the composite natural pigment sample containing natural red pigment to be detected is X and the pH value of the composite natural pigment sample containing natural taro purple pigment is Y. When the pH values ​​of X and Y are within the range of ±0.1 of the pH value of the corresponding standard sample (i.e., the allowable deviation of X and Y is ±0.1), it can be confirmed that the pH value in the composite natural pigment of the experimental sample is correct.

[0141] In summary, when both the absorbance and pH value meet the requirements within the standard deviation at the same time, it can be finally confirmed that the test sample meets the requirements.

[0142] The above-mentioned implementation modes are only preferred implementation modes of the present application and cannot be used to limit the scope of protection of the present application. Any non-substantial changes and substitutions made by technicians in this field on the basis of the present application shall fall within the scope of protection required by the present application.

Claims

1. A quick detection method for natural pigments, characterized in that: The following steps are involved: (1) preparing a composite natural pigment sample as an experimental sample to be tested, and preparing a standard sample with the same concentration as the experimental sample; (2) Using water or organic solvent to make up the volume of the composite natural pigment sample and standard sample; (3) Filter the sample after volume adjustment using a filter, and reserve the filtrate for later use; (4) Pour the filtrate into a glass cuvette, set the wavelength range and scan, and test with experimental water or organic solvent as blank to obtain the maximum absorbance at the characteristic wavelength of the sample; compare the maximum absorbance of the experimental sample with the maximum absorbance of the standard sample; and simultaneously determine the pH value of the standard sample solution and the experimental sample solution and compare them to confirm whether the pigment concentration in the experimental sample compound natural pigment is correct.

2. The method according to claim 1, characterized in that The composite natural pigment in step (1) includes: natural scarlet pigment or natural taro purple pigment; wherein the natural scarlet pigment includes cochineal, β-carotene, soybean oil, glycerol, butylated hydroxyanisole, butylated hydroxytoluene, lactic acid fatty acid glyceride, diacetyl tartaric acid mono- and diglycerol esters, mono- and diglycerol fatty acid esters, modified soybean lecithin, locust bean gum, sodium carboxymethyl cellulose, xanthan gum, guar gum, sodium D-isoascorbate, sodium hexametaphosphate, and water; the natural taro purple pigment includes cochineal, gardenia blue, glycerol, lactic acid fatty acid glyceride, diacetyl tartaric acid mono- and diglycerol esters, mono- and diglycerol fatty acid esters, modified soybean lecithin, locust bean gum, sodium carboxymethyl cellulose, xanthan gum, guar gum, sodium D-isoascorbate, sodium hexametaphosphate, and water.

3. The method according to claim 2, characterized in that The preparation process of the composite natural pigment (natural bright red pigment) in step (1) comprises: 1) Add weighed butyl hydroxyanisole and butylated hydroxytoluene to weighed soybean oil, heat to 180° C. in a mixing tank 1, then add β-carotene, heat to 180° C. and keep warm for 3 minutes, and cool to about 90° C. to obtain part A; 2) Weigh glycerol, lactic acid glyceride, diacetyl tartaric acid mono- and diglyceride, mono- and diglycerol fatty acid esters, modified soybean lecithin, locust bean gum, sodium carboxymethyl cellulose, xanthan gum, and guar gum and add them into a mixing tank 2, heat to 75° C. and keep warm, stir until completely dissolved, and obtain part B; 3) Add carmine, sodium D-isoascorbate and sodium hexametaphosphate into water, and stir and dissolve them uniformly in a stirring tank 3 to obtain part C; 4) Slowly pour part A into part B, and stir the part in mixing tank 2 with high-speed shear for 20 minutes until it is uniform; 5) Add part C into the above mixing tank 2 and stir at high speed for 10 minutes, then pass through a homogenizer at a pressure of 45 MPa and discharge.

4. The method according to claim 2, characterized in that: The preparation process of the composite natural pigment (natural taro purple pigment) in step (1) comprises: 1) Weigh glycerol, lactic acid glyceride, diacetyl tartaric acid mono- and diglyceride, mono- and diglyceride fatty acid esters, modified soybean lecithin, locust bean gum, sodium carboxymethyl cellulose, xanthan gum, and guar gum and add them into a mixing tank 2, heat to 75° C. and keep warm, stir until completely dissolved, and obtain part A; 2) Add cochineal red, gardenia blue, sodium D-isoascorbate and sodium hexametaphosphate into water, stir and dissolve evenly in a stirring tank 3 to obtain part B; 3) Slowly pour part A into part B, and stir the part in mixing tank 2 with high-speed shear for 20 minutes until it is uniform; 4) Add part C into the above mixing tank 2 and stir at high speed for 10 minutes, then pass through a homogenizer at a pressure of 45 MPa and discharge.

5. The method according to claim 3, characterized in that: The pigment content of the natural scarlet pigment is selected to be in the range of 1.5%-2.5%.

6. The method according to claim 5, characterized in that The pigment content of the natural taro purple pigment is selected to be in the range of 5.0%-9.5%.

7. The method according to claims 1-6, characterized in that: In the step (2), 1 g of the composite natural pigment sample is weighed, added to a 100 ml volumetric flask, and diluted to 100 ml with water; 10.0 ml is taken from the diluted solution and added to another 100 ml volumetric flask, and diluted to 100 ml with water, and the solution concentration is 1 mg / ml.

8. The method according to claims 1-6, characterized in that: In the step (3), a water filter with a filter membrane of 0.45 μm is used for filtration, and the filtrate is used for later use.

9. The method according to claims 3-4, characterized in that: In the step (4), the filtrate is poured into a glass cuvette with a diameter of 1 cm, the wavelength range is set to 450-580 nm, and interval scanning is performed with a scanning interval of 10 nm; the wavelength scanning function is turned on to obtain the maximum absorbance at the characteristic wavelength, and the absorbance is controlled between 0.2 and 0.

8.

10. The method according to claims 5-6, characterized in that: In the step (4), the filtrate is poured into a glass cuvette with a diameter of 1 cm, the wavelength range is set to 490-600 nm, and the interval scanning is 10 nm; the wavelength scanning function is turned on to obtain the maximum absorbance at the characteristic wavelength, and the absorbance is controlled between 0.2-0.8.

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