A rapid detection method for compound natural pigments

Abstract

This invention discloses a rapid detection method for compound natural pigments, belonging to the field of food testing. The specific steps are as follows: Prepare a compound natural pigment sample as the experimental sample, and simultaneously prepare a standard sample with the same concentration as the experimental sample; dilute the experimental sample and the control sample to volume with water or an organic solvent, then filter using a filter, and reserve the filtrate; pour the filtrate into a glass cuvette, set the wavelength range and scan, while simultaneously testing with experimental water or an organic solvent as a blank, obtaining 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; simultaneously measure and compare the pH values ​​of the standard sample solution and the experimental sample solution to confirm whether the concentration and type of the compound natural pigment in the experimental sample are correct. This invention provides a rapid detection method for compound natural pigments, expanding the detection scope and improving the accuracy of detection, thus helping to confirm whether the concentration of natural pigments in the final product and related materials meet product requirements.

Description

Technical Field

[0001] This application relates to the field of food testing, and more specifically to a rapid detection method for compound natural pigments disclosed in this invention. Background Technology

[0002] Natural pigments are compounds extracted from nature that possess coloring properties and are widely used in food, cosmetics, and pharmaceuticals. Compared to synthetic pigments, natural pigments offer higher safety, health benefits, and environmental friendliness, meeting modern consumers' demands for safe and healthy products. However, the chemical composition of natural pigments is complex, and their hues are relatively limited, often requiring compounding to meet diverse color requirements in practical applications. Compound natural pigments involve mixing multiple natural pigments in specific proportions to achieve particular color effects and stability requirements, and are widely used, especially in the food industry. In recent years, with advancements in 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, and gas chromatography are widely used for the quantitative analysis of natural pigments.

[0003] However, traditional methods for detecting compound natural pigments often suffer from problems such as complex operation, long processing time, and high cost. Especially when the compound system contains multiple components with significant differences in content, traditional methods struggle to quickly and accurately achieve qualitative and quantitative analysis of each component. For compound natural pigment manufacturers, errors during production due to worker negligence can lead to incorrect ingredient addition or incorrect proportions, resulting in the final product's color and concentration failing to meet requirements. According to GB26687-2011, the "National Food Safety Standard for General Rules for Compound Food Additives," the relevant content only addresses sensory characteristics, harmful substances (lead, arsenic), and pathogenic microorganisms; that is, it only provides safety indicators and does not include content-related requirements.

[0004] In the prior art, CN115015402B discloses a method for determining the content of three shikonin-type natural pigments in food, namely 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 shellac red pigment. Both methods target the detection of single natural pigments. Furthermore, there are currently no relevant national standards for the detection of compound natural pigments. National standards only determine the color value of single natural pigments. Therefore, developing a rapid and accurate method for detecting compound natural pigments has significant practical importance and application value. Summary of the Invention

[0005] Existing methods for detecting natural pigments involve measuring color value using an ultraviolet spectrophotometer, which is only applicable to single pigments and requires calculation after measurement at a fixed wavelength. This invention, however, involves measuring the absorbance of a mixture of multiple natural pigments (compound natural colorants). By measuring the maximum absorbance at the characteristic wavelength of a standard sample, the concentration and type of the compound natural pigment can be confirmed as correct.

[0006] This invention provides a rapid detection method for compound natural pigments. The method utilizes the maximum absorbance value obtained by superimposing the different absorption wavelengths of the compound natural pigments to determine the wavelength range. By confirming the absorbance of a certain compound natural pigment within the superimposed absorption wavelength range, the absorbance value of the compound natural pigment is determined, and the concentration value is determined based on the absorbance value. In subsequent production testing, the absorbance value of the compound natural pigment is measured by setting a wavelength range. Based on the absorbance value and wavelength range, and by comparing it with the characteristic wavelength and absorbance value of a standard sample, the correctness of the raw materials and concentration of the compound natural pigment can be confirmed.

[0007] Each natural pigment has a fixed wavelength for its maximum absorption value; for example, carmine is 494 nm, gardenia blue is 595 nm, and β-carotene is 450 nm. However, when two or more natural pigments are blended, the combined absorbance values ​​of the blended natural pigments (also known as blended natural colorants) will exhibit a maximum absorption value in a different wavelength range than before. Therefore, by measuring various standard blended natural pigments produced by enterprises, a series of data are obtained, including the absorption wavelength range and maximum absorbance value. These data serve as standard comparison solutions for blended natural pigments to determine whether the final product meets the concentration and pigment type requirements.

[0008] The specific technical solution of this invention is as follows:

[0009] A rapid detection method for natural pigments, characterized by comprising the following steps:

[0010] (1) Prepare compound natural pigment samples as experimental samples to be tested, and at the same time prepare standard samples with the same concentration as the experimental samples;

[0011] (2) The volume of the compounded natural pigment samples and standard samples was adjusted with water or organic solvent;

[0012] (3) Filter the sample after adjusting the volume using a filter, and keep 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 compound natural pigment (natural red pigment) in step (1) includes:

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

[0016] 2) Weigh out glycerol, lactic acid fatty acid glycerides, diacetyl tartaric acid mono- and diglycerides, mono- and diglycerides of fatty acids, modified soybean lecithin, locust bean gum, sodium carboxymethyl cellulose, xanthan gum, and guar gum, add them to mixing tank 2, heat to 75°C and keep warm, stir until completely dissolved, to obtain part B;

[0017] 3) Add carmine, sodium D-isoascorbate, and sodium hexametaphosphate to water and stir in mixing tank 3 until dissolved to obtain part C;

[0018] 4) Slowly pour part A into part B, and use mixing tank 2 to perform high-speed shearing and mixing for 20 minutes until homogeneous;

[0019] 5) Add part C to the above mixing tank 2 and shear mix at high speed for 10 minutes. Then, pass it through a homogenizer at a pressure of 45 MPa and discharge the material.

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

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

[0022] 2) Add carmine, gardenia blue, sodium D-isoascorbate, and sodium hexametaphosphate to water and stir in mixing tank 3 until dissolved to obtain part B;

[0023] 3) Slowly pour part A into part B, and use mixing tank 2 to perform high-speed shearing and mixing for 20 minutes until homogeneous;

[0024] 4) Add part C to the above mixing tank 2 and shear mix at high speed for 10 minutes. Then, pass it through a homogenizer at a pressure of 45 MPa and discharge the material.

[0025] Furthermore, the compound natural pigments in step (1) include: natural red pigment or natural taro purple pigment.

[0026] Furthermore, the natural red pigment includes carmine, β-carotene, soybean oil, glycerol, butylated hydroxyanisole, butylated hydroxytoluene, lactic acid fatty acid glycerides, diacetyl tartaric acid mono- and diglycerides, mono- and diglycerides of fatty acids, 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 red pigment is selected to be in the range of 1.5%-2.5%.

[0028] Furthermore, the 1.5% natural red pigment is a compound of 1.45% carmine and 0.05% β-carotene.

[0029] Furthermore, the 2.0% natural red pigment is a compound of 1.82% carmine and 0.18% β-carotene.

[0030] Furthermore, the 2.5% natural red pigment is a compound of 2.25% carmine and 0.25% β-carotene.

[0031] Furthermore, the natural taro purple pigment includes carmine, gardenia blue, glycerol, lactic acid fatty acid glycerides, diacetyl tartaric acid mono- and diglycerides, mono- and diglycerides of fatty acids, 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 a compound of 1.0% carmine and 4.0% gardenia blue.

[0034] Furthermore, the 7.5% natural taro purple pigment is a compound of 2.0% carmine and 5.5% gardenia blue.

[0035] Furthermore, the 9.5% natural taro purple pigment is a compound of 2.5% carmine and 7.0% gardenia blue.

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

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

[0038] Furthermore, in step (4) of the test for natural red pigment, the filtrate was poured into a glass cuvette with a diameter of 1 cm, the wavelength range was set to 450-580 nm, and the wavelength was scanned at intervals of 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 and 0.8.

[0039] Furthermore, in step (4) of the test for 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 wavelength was scanned at intervals of 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 and 0.8.

[0040] Those skilled in the art will recognize that natural red pigment and natural taro purple pigment exhibit different states at different pH values. Under acidic conditions, both natural red pigment and natural taro purple pigment will precipitate and lighten in color. Only under alkaline conditions will they present a uniform state. Specifically, the test samples were deemed compliant when the pH values ​​of standard natural red pigment at concentrations of 1.5%, 2.0%, and 2.5% were within the ranges of 8.68±0.1, 8.64±0.1, and 8.60±0.1 (i.e., an allowable deviation of ±0.1). Similarly, the test samples were deemed compliant when the pH values ​​of standard natural taro purple pigment at concentrations of 5% to 9.5% were within the ranges of 8.46±0.1, 8.51±0.1, and 8.30±0.1 (i.e., an allowable deviation of ±0.1). For the test sample to be definitively confirmed as compliant, both absorbance and pH value must simultaneously meet the standard deviation requirements.

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

[0042] (1) This invention improves the flexibility and applicability of detection. This invention is applicable not only to the detection of single natural pigments but also to the detection of compound natural pigments, which is of great significance in practical applications. This invention utilizes the maximum absorption value obtained by superimposing the different absorption wavelengths of the compound natural pigments to determine the wavelength range. By comparing a series of experimental data, it can be determined whether the product has a maximum absorption value within the wavelength range and whether the absorption value is within the specified concentration range. Furthermore, by adjusting the wavelength range and scanning parameters, this invention can also be flexibly applied to the detection of different types of natural pigments, enhancing the versatility and applicability of the detection method.

[0043] (2) This invention improves detection efficiency and accuracy. Traditional methods for detecting natural pigments often involve complex extraction, separation, and purification steps, which are time-consuming, cumbersome, and prone to errors. This invention, however, simplifies the detection process and shortens the detection cycle by directly performing spectral scanning on the compounded natural pigment sample after volume adjustment and filtration. Simultaneously, scanning within a specific wavelength range using a spectrometer accurately captures the characteristic absorption peaks of the natural pigment, thereby accurately determining its maximum absorbance value. Furthermore, while measuring absorbance, the pH value of the test sample is simultaneously measured by setting the pH value of the standard sample and comparing it with the standard sample. Through this two-dimensional detection, the test sample is ultimately confirmed to meet the requirements, improving the accuracy and reliability of the detection. This fast and efficient detection method helps enterprises respond quickly to market demands and improve product quality control efficiency.

[0044] (3) This invention reduces testing costs. Compared to traditional methods, this invention reduces the amount of chemical reagents used and the need for complex equipment, such as reducing the consumption of organic solvents and the number of extraction and separation steps, thereby reducing material and labor costs in the testing process. Furthermore, by standardizing operating procedures and simplifying steps, the testing process becomes easier to master and popularize, reducing reliance on professional technicians and further lowering overall testing costs. This is particularly important for small and medium-sized enterprises (SMEs), helping them enhance their competitiveness and expand their market share.

[0045] (4) This invention reduces reagent contamination. By optimizing the detection process, this invention reduces the emission of harmful substances such as organic solvents, thereby lowering environmental pollution. Simultaneously, the simplified detection process reduces wastewater treatment costs and further minimizes environmental pollution. Attached Figure Description

[0046] Figure 1 Flowchart of the rapid detection method for compound natural pigments described in this invention Detailed Implementation

[0047] To further illustrate the technical means and effects adopted by this application in order to achieve the intended purpose, the following detailed description of the specific implementation methods, structures, features and effects of this application is provided in conjunction with the accompanying drawings and preferred embodiments.

[0048] The specific embodiments of the present invention will be further described below. It should be noted that these descriptions are for the purpose of aiding understanding the present invention, but do not constitute a limitation thereof. Furthermore, the technical features involved in the various embodiments 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, all test materials used in the following examples are available through conventional commercial channels.

[0050] Example 1

[0051] 1. Reagents and Materials

[0052] The experimental water (Grade II water as specified in GB / T 6682) contained the following ingredients: carmine, β-carotene, soybean oil, glycerol, butylated hydroxyanisole, butylated hydroxytoluene, lactic acid fatty acid glycerides, diacetyl tartaric acid mono- and diglycerides, mono- and diglycerides of fatty acids, modified soybean lecithin, locust bean gum, sodium carboxymethyl cellulose, xanthan gum, guar gum, sodium D-isoascorbate, and sodium hexametaphosphate. Additionally, the experimental water contained the following ingredients: carmine, gardenia blue, glycerol, lactic acid fatty acid glycerides, diacetyl tartaric acid mono- and diglycerides, mono- and diglycerides of fatty acids, modified soybean lecithin, locust bean gum, sodium carboxymethyl cellulose, xanthan gum, guar gum, sodium D-isoascorbate, and sodium hexametaphosphate.

[0053] 2. Instruments and equipment

[0054] mixing tank

[0055] High-speed shear mixing tank

[0056] High pressure homogenizer

[0057] 3. Method and Steps (1) The preparation process of compounding natural pigments (natural red pigments) includes:

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

[0059] b. Weigh out glycerol, lactic acid fatty acid glycerides, diacetyl tartaric acid mono- and diglycerides, mono- and diglycerides of fatty acids, modified soybean lecithin, locust bean gum, sodium carboxymethyl cellulose, xanthan gum, and guar gum, add them to mixing tank 2, heat to 75°C and keep warm, stir until completely dissolved, to obtain part B.

[0060] c. Add carmine, sodium D-isoascorbate, and sodium hexametaphosphate to water and stir in mixing tank 3 until dissolved to obtain part C;

[0061] d. Slowly pour part A into part B, and use mixing tank 2 to perform high-speed shearing and mixing for 20 minutes until homogeneous;

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

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

[0064] a. Weigh out glycerol, lactic acid fatty acid glycerides, diacetyl tartaric acid mono- and diglycerides, mono- and diglycerides of fatty acids, modified soybean lecithin, and locust.

[0065] Soy gum, sodium carboxymethyl cellulose, xanthan gum, and guar gum are added to mixing tank 2, heated to 75°C and kept at that temperature, and stirred until completely dissolved to obtain part A;

[0066] b. Add carmine, gardenia blue, sodium D-isoascorbate, and sodium hexametaphosphate to water, and stir in mixing tank 3 until dissolved to obtain part B;

[0067] c. Slowly pour part A into part B, and use mixing tank 2 to perform high-speed shearing and mixing of this part for 20 minutes until it is uniform;

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

[0069] Example 2

[0070] 1. Reagents and Materials

[0071] Experimental water (Grade II water as specified in GB / T 6682)

[0072] 2. Instruments and equipment

[0073] The electronic balance has a sensitivity of 0.001g.

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

[0075] 100ml volumetric flask (Grade A)

[0076] 0.45μm water filter

[0077] 3. Standard comparison samples

[0078] Standard natural pigments, namely carmine and beta-carotene, were purchased through conventional commercial channels, and then compounded to obtain products of relevant concentrations as standard comparison samples, i.e., standard natural bright red pigments.

[0079] The standard natural red pigment comprises: carmine, carotene, glycerin, and water; that is, the natural red pigment is a compound of two natural pigments, carmine and β-carotene; the content range of the natural red pigment is selected to be 1.5%-2.5%. The 1.5% natural red pigment is a compound of 1.45% carmine and 0.05% β-carotene. The 2.0% natural red pigment is a compound of 1.82% carmine and 0.18% β-carotene. The 2.5% natural red pigment is a compound of 2.25% carmine and 0.25% β-carotene.

[0080] 4. Testing experimental samples

[0081] Prepare the compound natural pigment X containing natural red pigment to be tested.

[0082] 4. Methods and Steps

[0083] (1) Prepare the compound natural pigment sample X containing natural red pigment as the test sample, and prepare its concentration to be 1.0 mg / ml. At the same time, prepare three sets of standard samples with the same concentration as the test sample. The content of natural red pigment in the three sets of standard compound natural pigments is 1.5%, 2.0% and 2.5%, respectively. The 1.5% natural red pigment is composed of 1.45% carmine and 0.05% β-carotene; the 2.0% natural red pigment is composed of 1.82% carmine and 0.18% β-carotene; and the 2.5% natural red pigment is composed of 2.25% carmine and 0.25% β-carotene.

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

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

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

[0087] Enable wavelength scanning to obtain the maximum absorbance at the characteristic wavelength, which is controlled between 0.2 and 0.8. Simultaneously, use experimental water or organic solvent as a blank to test and obtain the absorbance of the sample at the characteristic wavelength. 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 absorbance of the 2.5% natural red pigment standard sample is 0.751 at a wavelength of 520 nm. Assuming the absorbance of the compound natural pigment X containing natural red pigment to be tested is X1 at 520 nm, then when X1 is within the range of 0.751 ± 0.02 (i.e., the allowable deviation of X1 is ± 0.02), the pigment concentration in the compound natural pigment of the experimental sample can be confirmed to be correct.

[0092] As shown in Table 1, the maximum absorbance of the 2.0% natural red pigment standard sample is 0.574 at a wavelength of 520 nm. Assuming the absorbance of the compound natural pigment X containing natural red pigment to be tested at 520 nm is X2, then when X2 is within the range of 0.574 ± 0.02 (i.e., the allowable deviation of X2 is ± 0.02), the pigment concentration in the compound natural pigment of the experimental sample can be confirmed to be correct.

[0093] As shown in Table 1, the maximum absorbance of the 1.5% natural red pigment standard sample is 0.439 at a wavelength of 520 nm. Assuming the absorbance of the compound natural pigment X containing natural red pigment to be tested is X3 at 520 nm, then when X3 is within the range of 0.439 ± 0.02 (i.e., the allowable deviation of X3 is ± 0.02), the pigment concentration in the compound natural pigment of the experimental sample can be confirmed to be correct.

[0094] Example 3

[0095] 1. Reagents and Materials

[0096] Experimental water (Grade II water as specified in GB / T 6682)

[0097] 2. Instruments and equipment

[0098] The electronic balance has a sensitivity of 0.001g.

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

[0100] 100ml volumetric flask (Grade A)

[0101] 0.45μm water filter

[0102] 3. Standard comparison samples

[0103] Standard natural pigments, carmine and gardenia blue, were purchased through conventional commercial channels, and after being compounded, the corresponding concentrations of the product were used as standard comparison samples, namely, standard natural taro purple pigment.

[0104] The standard natural taro purple pigment comprises: carmine, gardenia blue, glycerin, and water; that is, the natural taro purple pigment is a compound of two natural pigments, carmine and gardenia blue; the content range of the natural taro purple pigment is selected as 5.0%-9.5%. The 5.0% natural taro purple pigment is a compound of 1.0% carmine and 4.0% gardenia blue. The 7.5% natural taro purple pigment is a compound of 2.0% carmine and 5.5% gardenia blue. The 9.5% natural taro purple pigment is a compound of 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 for testing.

[0107] 4. Methods and Steps

[0108] (1) A compound natural pigment sample Y containing natural taro purple pigment was prepared as the test sample, with a concentration of 1.0 mg / ml. Three sets of standard samples with the same concentration as the test sample were also prepared. The contents of natural red pigment in these three sets of standard compound natural pigments were 5.0%, 7.5%, and 9.5%, respectively. The 5.0% natural taro purple pigment was composed of 1.0% carmine and 4.0% gardenia blue. The 7.5% natural taro purple pigment was composed of 2.0% carmine and 5.5% gardenia blue. The 9.5% natural taro purple pigment was composed of 2.5% carmine and 7.0% gardenia blue.

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

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

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

[0112] Enable wavelength scanning to obtain the maximum absorbance at the characteristic wavelength, which is controlled between 0.2 and 0.8. Simultaneously, use experimental water or organic solvent as a blank to test and obtain the absorbance of the sample at the characteristic wavelength. 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 absorbance of the 9.5% natural taro purple pigment standard sample is 0.712 at a wavelength of 560 nm. Assuming the absorbance of the compound natural pigment Y containing natural taro purple pigment to be tested is Y1 at 560 nm, then when Y1 is within the range of 0.712 ± 0.02 (i.e., the allowable deviation of Y1 is ± 0.02), the pigment concentration in the compound natural pigment of the experimental sample can be confirmed to be correct.

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

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

[0118] To ensure the validity of the experimental data, the allowable deviation is ±0.02 if the absorbance Y of the sample to be tested is ≥0.400, and ±0.01 if the absorbance Y is <0.400.

[0119] Example 4

[0120] 1. Reagents and Materials

[0121] Laboratory water (Grade II water as specified in GB / T 6682), phthalate buffer solution with pH = 4.00, phosphate buffer solution with pH = 6.86, and tetraborate buffer solution with pH = 9.18.

[0122] 2. Instruments and equipment

[0123] pH meter (accuracy 0.01)

[0124] Composite electrode: assembled from a glass indicator electrode and an Ag / AgCl or Hg2Cl2 reference electrode.

[0125] Magnetic stirrer

[0126] 3. Standard comparison samples

[0127] (1) Standard natural red pigments: carmine and β-carotene were purchased through conventional commercial channels, and after compounding, the relevant concentration products were obtained as standard comparison samples, i.e., standard natural red pigments.

[0128] The standard natural red pigment comprises: carmine, carotene, glycerin, and water; that is, the natural red pigment is a compound of two natural pigments, carmine and β-carotene; the content range of the natural red pigment is selected to be 1.5%-2.5%. The 1.5% natural red pigment is a compound of 1.45% carmine and 0.05% β-carotene. The 2.0% natural red pigment is a compound of 1.82% carmine and 0.18% β-carotene. The 2.5% natural red pigment is a compound of 2.25% carmine and 0.25% β-carotene.

[0129] (2) Standard natural taro purple pigments: carmine and gardenia blue were purchased through conventional commercial channels, and after compounding, the relevant concentration products were used as standard comparison samples, i.e., standard natural taro purple pigments. The standard natural taro purple pigments include: carmine, gardenia blue, glycerin, and water; that is, the natural taro purple pigments are compounded from two natural pigments, carmine and gardenia blue; the content range of the natural taro purple pigments is selected as 5.0%-9.5%. The 5.0% natural taro purple pigment is compounded from 1.0% carmine and 4.0% gardenia blue. The 7.5% natural taro purple pigment is compounded from 2.0% carmine and 5.5% gardenia blue. The 9.5% natural taro purple pigment is compounded from 2.5% carmine and 7.0% gardenia blue.

[0130] 4. Testing experimental samples

[0131] Prepare the compound natural pigment X containing natural red pigment and prepare the compound natural pigment Y containing natural taro purple pigment to be tested.

[0132] 3. Measurement

[0133] 3.1 pH meter calibration

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

[0135] 3.2 Determination of the sample

[0136] Take a sample large enough to immerse the electrode, insert the electrode into the sample, and maintain the temperature within the range of 20±2℃. Turn on the magnetic stirrer, and after the reading stabilizes, take the reading directly.

[0137] The measured data are shown in Table 3:

[0138] Table 3

[0139]

[0140] As shown in Table 3, assuming the pH value of the compound natural pigment sample containing natural red pigment is X and the pH value of the compound natural pigment sample containing natural taro purple pigment is Y, when the pH values ​​of X and Y are within ±0.1 of the corresponding standard sample pH values ​​(i.e., the allowable deviation of X and Y is ±0.1), the pH value of the compound natural pigment in the experimental sample can be confirmed as correct.

[0141] In summary, both absorbance and pH value must meet the standard deviation requirements simultaneously for the test sample to be finally confirmed as compliant.

[0142] The above embodiments are merely preferred embodiments of this application and should not be construed as limiting the scope of protection of this application. Any non-substantial changes and substitutions made by those skilled in the art based on this application shall fall within the scope of protection claimed by this application.

Claims

1. A rapid detection method for natural pigments, characterized in that, Includes the following steps: (1) Prepare a compound natural pigment sample as the experimental sample to be tested, and at the same time prepare a standard sample with the same concentration as the experimental sample; the compound natural pigment in step (1) includes: natural red pigment; wherein the natural red pigment includes carmine, β-carotene, soybean oil, glycerol, butylated hydroxyanisole, dibutylated hydroxytoluene, lactic acid fatty acid glycerides, diacetyl tartaric acid mono- and diglycerides, mono- and diglycerides of fatty acids, modified soybean lecithin, locust bean gum, sodium carboxymethyl cellulose, xanthan gum, guar gum, sodium D-isoascorbate, sodium hexametaphosphate, and water; the preparation process of the natural red pigment in step (1) includes: 1) Add the weighed butylated hydroxyanisole and butylated hydroxytoluene to the weighed soybean oil, heat to 180°C in mixing tank 1, then add β-carotene, heat to 180°C and keep warm for 3 minutes, then cool to 90°C to obtain part A; 2) Weigh out glycerol, lactic acid fatty acid glycerides, diacetyl tartaric acid mono- and diglycerides, mono- and diglycerides of fatty acids, modified soybean lecithin, locust bean gum, sodium carboxymethyl cellulose, xanthan gum, and guar gum and add them to mixing tank 2. Heat to 75°C and keep warm. Stir until completely dissolved to obtain part B. 3) Add carmine, sodium D-isoascorbate, and sodium hexametaphosphate to water and stir in mixing tank 3 until dissolved to obtain part C; 4) Slowly pour part A into part B, then mix at high speed in mixing tank 2 for 20 minutes until homogeneous; 5) Add part C to the above mixing tank 2 and shear mix at high speed for 10 min, then pass it through a homogenizer at a pressure of 45 MPa and discharge the material; The pigment content of the selected natural red pigment is in the range of 1.5%-2.5%; (2) The compound natural pigment sample and the standard sample are diluted with water or organic solvent; in step (2), 1g of the compound natural pigment sample is weighed and added to a 100ml volumetric flask, and diluted with water to 100ml; 10.0ml of the diluted solution is taken to another 100ml volumetric flask and diluted with water to 100ml, and the solution concentration is 1mg / ml; (3) Filter the sample after volume adjustment using a filter and keep the filtrate for later use; in step (3), a water filter with a 0.45 μm filter membrane is used for filtration and the filtrate is kept 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; at the same time, measure the pH value of the standard sample solution and the experimental sample solution and compare them to confirm whether the pigment concentration in the compound natural pigment of the experimental sample is correct; in step (4), pour the filtrate into a glass cuvette with a diameter of 1 cm, set the wavelength range to 450-580 nm, scan at intervals of 10 nm; turn on the wavelength scanning function to obtain the maximum absorbance at the characteristic wavelength, and control the absorbance between 0.2 and 0.8.

Images