Optimization method for measuring color value of white sugar

Abstract

The invention discloses a method for optimizing the color value measurement of granulated sugar. The method is mainly used for grading granulated sugar, does not require adjustment of instruments, can measure granulated sugar of various grades at the same time, uses different filter combinations as intermediate comparison quantities, obtains optimized granulated sugar color values ​​after measurement and mathematical model calculation, and makes the color value measurement more accurate.

Description

Technical Field

[0001] The invention relates to the field of white sugar detection, and in particular to a method for optimizing the color value measurement of white sugar. Background Art

[0002] The color value of white sugar is an important basis for the classification of white sugar as stipulated in the national standard GB / T 317-2018 "White Sugar", and ultimately determines the trade price of white sugar products. Therefore, the color value of white sugar is a technical indicator that both enterprises and the market pay close attention to.

[0003] According to GB / T 35887-2018 "Test Method for Granulated Sugar", the color value of granulated sugar is calculated from several parameters such as the absorbance of the granulated sugar solution and the thickness of the cuvette. Among them, the most difficult parameter to measure accurately is the absorbance of the granulated sugar solution. If this parameter is measured accurately, the color value can also be measured accurately.

[0004] The absorbance of white sugar solution is measured by a spectrophotometer. GB / T 35887-2018 requires that the wavelength error of the spectrophotometer at 420nm should not exceed 1nm. During the sugar-making season that lasts for several months, the spectrophotometer is generally used continuously, and it is difficult to always meet the wavelength error requirement, resulting in inaccurate measurements. It is also very difficult to adjust the instrument during use. At the same time, white sugar is divided into four grades. It is difficult for an ordinary spectrophotometer to measure accurately at each grade. Generally, it can only be used for a certain grade, resulting in low efficiency.

[0005] Therefore, it is necessary to provide an optimized method for measuring the color value of white sugar, which does not require adjustment of the instrument and can measure white sugar of various grades at the same time, so that the color value measurement value is more accurate. Summary of the invention

[0006] In order to solve the above technical problems, the technical solution adopted by the present invention is:

[0007] A method for optimizing the measurement of color value of white sugar comprises the following steps:

[0008] 1) Prepare the white sugar solution to be measured according to GB / T 35887-2018 "Test Method for White Sugar"; use a spectrophotometer to measure the white sugar solution to obtain an absorbance measurement value A;

[0009] 2) determining whether to replace the cuvette and measure the absorbance of the white sugar solution again according to the numerical interval of the absorbance measurement value A of the white sugar solution;

[0010] 3) According to the absorbance measurement value A of the white sugar solution determined in step 2), a filter combination is selected, and the absorbances A1, A2, and A3 under three different filter combinations are measured using a spectrophotometer;

[0011] 4) Calculate the transmittance standard value T of the three filter combinations based on the mathematical model of filter superposition and the standard value of a single filter. S1 , T S2 , T S3 ;

[0012] 5) According to the relationship between absorbance A and transmittance T:

[0013] A = -log(T)(T = T S1 , T S2 , T S3 ) Calculate the absorbance standard value A of the three filter combinations S1 , A S2 , A S3 ;

[0014] 6) According to the formula

[0015] and A c =(dA) / a, and the optimized absorbance A is obtained c ;

[0016] 7) According to the optimized absorbance A c , calculate the optimized color value Then grade it according to the color value.

[0017] Establishment of the mathematical model of filter superposition:

[0018] The filters are placed parallel to each other, with the plane perpendicular to the incident light direction. What needs to be established is the outgoing light intensity A n The mathematical model of the relationship between the incident light intensity A0 and the reflection of light between filters, including primary reflection, secondary reflection and multiple reflections. Take the superposition of two filters as an example:

[0019] A0——incident light intensity; A1——light intensity between filters 1 and 2; A2——outgoing light intensity;

[0020] T1——transmittance of filter 1; T2——transmittance of filter 2;

[0021] K1——reflectivity of filter 1; K2——reflectivity of filter 2;

[0022] A 1i ——The intensity of light reflected by filter 2 for the i-th time

[0023] A1 can be considered as an infinite number of light beams A 10 , A 11 , A 12 ...A 1i Composition, A 1iRepresents the light reflected i times by filter 1 and filter 2 (i = 0, 1, 2...)

[0024]

[0025] in

[0026] A 1i =A0T1(K1K2) i

[0027] Substituting into the above formula, we get

[0028]

[0029] Since K1K2<<1, we have

[0030]

[0031] If T1=T2=T,K1=K2=K, we get

[0032]

[0033] By extending this method to the case of n filters, we can obtain:

[0034]

[0035] If T1=T2=…=T i =T,K1=K2=…=K i =K, let the equivalent transmittance T i =A i / A0, we get

[0036]

[0037] Substituting n=1, 2, 3, 4 respectively, we get

[0038]

[0039] T1, T2, T3, T4 correspond to the transmittance values ​​of a single piece, two pieces stacked, three pieces stacked, and four pieces stacked respectively. T and K can be measured by a higher-level spectrophotometer as standard values.

[0040] The absorbance of white sugar solution measured on a spectrophotometer is A. The same spectrophotometer measures three different superposition combinations of filter sets to obtain a set of absorbance values ​​A1, A2, and A3. The standard transmittance values ​​T of the three superposition combinations can be calculated based on the mathematical model. S1 , T S2 , T S3 , optimized value A C The calculation method is as follows:

[0041] Absorbance standard value A S (A S1 , A S2 , A S3 ) and the standard value of transmittance T S (T S1 , T S2 , T S3 )satisfy

[0042] A si = -log(T si )i=1,2,3

[0043] Under the conditions of a certain wavelength and a small absorbance range, the absorbance measurement value A of the filter set can be considered i (A1, A2, A3) and transmittance standard value T Si (T S1 , T S2 , T S3 ) satisfies the linear relationship:

[0044] A i =alog(T si )+di=1,2,3

[0045] The absorbance measurement value A i (A1, A2, A3) and absorbance measurement value T Si (T S1 , T S2 , T S3 )satisfy

[0046] A i =-aA si +di=1,2,3

[0047] Where a and d are function fitting values, which can be calculated by the least squares method:

[0048]

[0049] Measured value A and optimized value A c The relationship can be expressed as:

[0050] A=-aA c +d

[0051] Right now

[0052] A c

[0053] Preferably, in step 1), a cuvette with a thickness of 5 cm is selected, and a spectrophotometer is used to measure the white sugar solution at a wavelength of 420 nm to obtain an absorbance measurement value A.

[0054] Preferably, in step 2): ① If 0.05 ≤ A ≤ 0.07 in step 1), replace the colorimetric cell with a thickness of 10 cm and measure again to obtain the absorbance value A; ② If 0.07 < A ≤ 0.10 in step 1), there is no need to replace the colorimetric cell, and the absorbance value A is the value obtained in step 1); ③ If 0.10 < A ≤ 0.16 in step 1), there is no need to replace the colorimetric cell, and the absorbance value A is the value obtained in step 1); ④ If 0.3 ≤ A ≤ 0.5 in step 1), replace the colorimetric cell with a thickness of 1 cm and measure again to obtain the absorbance value A; ⑤ If 0.5 < A ≤ 0.75 in step 1), replace the colorimetric cell with a thickness of 1 cm and measure again to obtain the absorbance value A; The absorbance measurement values of the remaining granulated sugar solutions do not need to be measured again, and the absorbance value A is the value obtained in step 1).

[0055] Preferably, the selection method of the 3 different filter combinations in step 3) is as follows: If the absorbance value A in step 2) is the one obtained in ①, the 3 different filter combinations are 2 pieces stacked, 3 pieces stacked, and 4 pieces stacked;

[0056] If the absorbance value A in step 2) is the one obtained in ②, the 3 different filter combinations are single piece, 2 pieces stacked, and 3 pieces stacked;

[0057] If the absorbance value A in step 2) is the one obtained in ③, the 3 different filter combinations are 2 pieces stacked, 3 pieces stacked, and 4 pieces stacked;

[0058] If the absorbance value A in step 2) is the one obtained in ④, the 3 different filter combinations are single piece, 2 pieces stacked, and 3 pieces stacked;

[0059] If the absorbance value A in step 2) is the one obtained in ⑤, the 3 different filter combinations are 2 pieces stacked, 3 pieces stacked, and 4 pieces stacked.

[0060] Preferably, for the 3 different filter combinations selected in step 3), the measured absorbances are A1, A2, A3, which satisfy A1 < A2 < A3, and at the same time, the relationship with the absorbance A determined in step 2) satisfies A1 < A < A3.

[0061] Preferably, in step 2): If A < 0.05, the quality of the granulated sugar is defined as refined grade; if 0.16 < A < 0.3, the quality of the granulated sugar is defined as premium grade; if A > 0.75, the quality of the granulated sugar is defined as second grade; For other ranges of A values, calculate the optimized color value according to step 7), and then grade according to Table 6 of the granulated sugar color value and grading standard.

[0062] Preferably, in step 2), the spectrophotometer measures the absorbance value of the granulated sugar solution at a wavelength of 420 nm.

[0063] Preferably, when measuring refined sugar in step 2), a 10 cm cuvette is used; when measuring premium sugar, a 5 cm cuvette is used; when measuring primary sugar and secondary sugar, a 1 cm cuvette is used.

[0064] The filter combination is a combination of a plurality of filters with the same optical parameters superimposed on each other.

[0065] Due to the adoption of the above technical solution, the present invention has the following technical advances compared with the prior art:

[0066] The optimized method for measuring the color value of white sugar does not require adjustment of the instrument and can measure white sugar of all grades at the same time. Different filter combinations are used as intermediate comparison quantities. After measurement and mathematical model calculation, the optimized absorbance A is obtained. c , and then calculate the optimized color value to make the color value measurement more accurate. BRIEF DESCRIPTION OF THE DRAWINGS

[0067] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the structures shown in these drawings without paying creative work.

[0068] Figure 1 A distribution diagram of absorbance values ​​of white sugar solution and filter combination selection in the white sugar color value measurement optimization method of the present invention;

[0069] Figure 2 It is a flow chart of the method for optimizing the color value measurement of white granulated sugar of the present invention; DETAILED DESCRIPTION

[0070] The following embodiments may help those skilled in the art to more fully understand the present invention, but shall not limit the present invention in any way.

[0071] Example 1

[0072] A method for optimizing the measurement of color value of white sugar comprises the following steps:

[0073] 1) Prepare the white sugar solution to be measured according to GB / T 35887-2018 "Test Method for White Sugar"; use a spectrophotometer to measure the white sugar solution to obtain an absorbance measurement value A;

[0074] 2) determining whether to replace the cuvette and measure the absorbance of the white sugar solution again according to the numerical interval of the absorbance measurement value A of the white sugar solution;

[0075] 3) Based on the measured absorbance value A of the white granulated sugar solution determined in step 2), select a filter combination, and use a spectrophotometer to measure the absorbances A1, A2, and A3 under 3 different filter combinations respectively;

[0076] 4) Calculate the standard transmittance values T S1 , T S2 , T S3 of the 3 filter combinations according to the mathematical model of filter stacking and the standard values of single filters;

[0077] 5) According to the relationship between absorbance A and transmittance T:

[0078] A = -log(T) (T = T S1 , T S2 , T S3 ), calculate the standard absorbance values A S1 , A S2 , A S3 of the 3 filter combinations;

[0079] 6) According to the formula

[0080] and A c = (d - A) / a, obtain the optimized absorbance A c ;

[0081] 7) According to the optimized absorbance A c , calculate the optimized color value and then grade according to the color value.

[0082] In this embodiment, in step 1), under the condition of a wavelength of 420 nm, using a spectrophotometer under the measurement condition of a cuvette thickness of 5 cm, measure the white granulated sugar solution to obtain the measured absorbance value A.

[0083] In this embodiment, in step 2): ① If 0.05 ≤ A ≤ 0.07 in step 1), replace the cuvette with a thickness of 10 cm and measure again to obtain the absorbance value A; ② If 0.07 < A ≤ 0.10 in step 1), there is no need to replace the cuvette, and the absorbance value A is the value obtained in step 1); ③ If 0.10 < A < 0.16 in step 1), there is no need to replace the cuvette, and the absorbance value A is the value obtained in step 1); ④ If 0.30 ≤ A ≤ 0.50 in step 1), replace the cuvette with a thickness of 1 cm and measure again to obtain the absorbance value A; ⑤ If 0.50 < A ≤ 0.75 in step 1), replace the cuvette with a thickness of 1 cm and measure again to obtain the absorbance value A; for the measured absorbance values of the remaining white granulated sugar solutions, there is no need to measure again, and the absorbance value A is the value obtained in step 1).

[0084] In this embodiment, the selection method of the three different filter combinations in step 3) is as follows: If the absorbance value A in step 2) is obtained as ①, then the three different filter combinations are 2 filters stacked, 3 filters stacked, and 4 filters stacked;

[0085] If the absorbance value A in step 2) is obtained as ②, then the three different filter combinations are a single filter, 2 filters stacked, and 3 filters stacked;

[0086] If the absorbance value A in step 2) is obtained as ③, then the three different filter combinations are 2 filters stacked, 3 filters stacked, and 4 filters stacked;

[0087] If the absorbance value A in step 2) is obtained as ④, then the three different filter combinations are a single filter, 2 filters stacked, and 3 filters stacked;

[0088] If the absorbance value A in step 2) is obtained as ⑤, then the three different filter combinations are 2 filters stacked, 3 filters stacked, and 4 filters stacked.

[0089] In this embodiment, for the three different filter combinations selected in step 3), the measured absorbances are A1, A2, and A3, which satisfy A1 < A2 < A3, and at the same time, the relationship with the absorbance A determined in step 2) satisfies A1 < A < A3.

[0090] In this embodiment, in step 2): If A < 0.05, the quality of the white granulated sugar is defined as the refined grade; if 0.16 < A < 0.3, the quality of the white granulated sugar is defined as the premium grade; if A > 0.75, the quality of the white granulated sugar is defined as the second grade; for other ranges of A values, the optimized color value is calculated according to step 7), and then the grading is carried out according to Table 6 of the white granulated sugar color value and the grading standard.

[0091] In this embodiment, in step 2), the spectrophotometer measures the absorbance value of the white granulated sugar solution at a wavelength of 420 nm.

[0092] In this embodiment, in step 2), when measuring refined sugar, a 10 cm cuvette is selected; when measuring premium sugar, a 5 cm cuvette is selected; when measuring first-grade sugar and second-grade sugar, a 1 cm cuvette is selected.

[0093] The filter combination is a combination of several filters with the same optical parameters stacked together.

[0094] Example 2

[0095] An optimization method for measuring the color value of white granulated sugar, comprising the following steps:

[0096] 1) Prepare a white granulated sugar solution from the white granulated sugar sample to be measured. The white granulated sugar to be measured is a refined color value reference material of white granulated sugar developed by the Physical and Chemical Institute of Guangxi Institute of Metrology and Testing, and its standard color value is 22.8 IU. After the white granulated sugar is prepared into a solution, the sample solution concentration is 0.5060 g / mL. Use a spectrophotometer with a model of 721G-100 to measure the white granulated sugar solution. The thickness of the colorimetric cell is 5 cm, and the measured absorbance value of the solution is A = 0.064;

[0097] 2) In step 1), 0.05 < A < 0.07. Replace the 10 cm colorimetric cell and re-measure to get A = 0.128;

[0098] 3) According to the measured absorbance value of the white granulated sugar solution determined in step 2), select combinations of filter plates with 2 filter plates stacked, 3 filter plates stacked, and 4 filter plates stacked and measure them on this spectrophotometer respectively. The average absorbance values obtained are:

[0099] A1 = 0.072, A2 = 0.114, A3 = 0.158;

[0100] 4) Calculate the standard transmittance values of the 3 filter plate combinations according to the mathematical model of filter plate stacking and the standard values of single filter plates:

[0101] T S1 = 0.8361, T S2 = 0.7733, T S3 = 0.7149

[0102] 5) According to the relationship between absorbance A and transmittance T:

[0103] A = -log(T) (T = T S1 , T S2 , T S3 ) Calculate the standard absorbance values of the 3 filter plate combinations to be

[0104] A S1 = 0.0777, A S2 = 0.1116, A S3 = 0.1458

[0105] 6) According to the formula

[0106]

[0107] From A c = (d - A) / a, calculate the optimized absorbance to be:

[0108]

[0109] 7) According to the optimized absorbance A c, calculate the optimized color value

[0110]

[0111] Based on the optimized color value, the white sugar sample was graded as refined grade, which is the same as the actual grade.

[0112] If not optimized, the color value is

[0113]

[0114] If not optimized, the white sugar sample will be graded as superior, which is inconsistent with the actual grade.

[0115] ΔC1=CC S =25.3-22.8=2.5IU

[0116] ΔC2=C VC -C S =24.0-22.8=1.2IU

[0117] Among them, 22.8 is the color value standard value of the refined grade white sugar color value standard material, 25.3 is the absorbance measurement value of the white sugar solution measured by the spectrophotometer model 721G-100, which is A=0.128 and the unoptimized color value is calculated, and 24.0 is the optimized color value. It can be seen that the unoptimized color value has a large deviation and the classification is incorrect. After optimization, the deviation is significantly reduced and the classification is correct.

[0118] Calculation method of color value of white sugar

[0119] The test method for the chromaticity of white sugar is specified in GB / T 35887-2018 "Test method for white sugar": it is calculated by measuring the absorbance value of the solution at a wavelength of 420nm, the thickness of the cuvette and the concentration of the solution.

[0120] C v

[0121] C v ——Color value (IU)

[0122] A - absorbance measured at 420 nm

[0123] b——Cuvette thickness (cm)

[0124] c——sample concentration (mg / L)

[0125] Selection of filter combinations

[0126] The selected filters are made by Chengdu Aotai Technology Co., Ltd., numbered F001-F005, one of which is used as a spare. The measuring instrument is the ultraviolet, visible, and near-infrared spectrophotometer manufactured by PE Company of the United States, model Lambda950, with the main parameters as follows: wavelength range (175-3300) nm, transmittance range (0-100)%, maximum allowable wavelength error ±0.5 nm, maximum allowable transmittance error ±0.3%, and stray radiation level less than 0.2%. The spectrophotometer is used to scan the 5 filters at (400-440) nm, with a wavelength interval of 0.1 nm. The transmittance data are as follows (due to the large amount of data, only the data of (415-425) nm are listed, with a wavelength interval of 1 nm):

[0127]

[0128] Table 2 Transmittance data of filter at (415~425)nm

[0129] The relationship between absorbance A and transmittance T is as follows

[0130] A

[0131] From Table 1, we can see that the transmittance of the filter is between 0.905 and 0.915, and the corresponding absorbance range is 0.038 to 0.043. The range that can be achieved by superposition is 0.038-0.173, which is enough to cover Figure 1 The absorbance of the medium white sugar solution ranges from 0.05 to 0.16. The reflectance of the filter measured by Lambda950 is between 0.06 and 0.07, which is much smaller than the transmittance value.

[0132] Experimental example

[0133] Taking 3-sheet superposition and 4-sheet superposition as examples, Lambda950 spectrophotometer was used to scan in the (400-440) nm wavelength range, with a wavelength interval of 0.1 nm. Two combinations were selected for each, and the model value and measured value data of the transmittance are as follows (due to the large amount of data, only the data of (415-425) nm are listed, with a wavelength interval of 1 nm):

[0134]

[0135] Table 3 Comparison of 3 filter superposition model values ​​and measured values

[0136]

[0137]

[0138] Table 4 Comparison of 4 filter superposition model values ​​and measured values

[0139] From the data in the two tables, it can be seen that the deviation between the model value and the measured value is very small, and the consistency is also very good near 420nm.

[0140] Select different filter combinations according to the absorbance range. The specific method is as follows:

[0141]

[0142] Table 5 Absorbance range and filter combination selection

[0143]

[0144] Table 6 Color value and grading standard of white sugar

[0145] The above generally describes the present invention in detail, but it is obvious to a person skilled in the art that some modifications or improvements can be made to the present invention. Therefore, modifications or improvements that do not depart from the spirit of the present invention are within the scope of protection of the present invention.

Claims

1. A method for optimizing the measurement of color value of white sugar, characterized in that: It includes the following steps: 1) Prepare a white granulated sugar solution with the white granulated sugar to be measured; Use a spectrophotometer to measure the white granulated sugar solution to obtain the absorbance measurement value A; 2) Determine whether to replace the cuvette and measure the absorbance of the white granulated sugar solution again according to the numerical range where the absorbance measurement value A of the white granulated sugar solution is located; 3) According to the absorbance measurement value A of the white granulated sugar solution determined in step 2), select 3 different filter combinations, and use a spectrophotometer to measure the absorbances A1, A2, and A3 under the 3 different filter combinations respectively; 4) According to the mathematical model of filter superposition and the standard value of single filter, calculate the standard transmittance value T of the three filter combinations S1 , T S2 , T S3 ; 5) According to the relationship between the absorbance A and the transmittance T: A = -log(T)(T = T S1 , T S2 , T S3 ) Calculate the absorbance standard values ​​As1, A of the three filter combinations S2 , A S3 ; 6) According to the formula and A c =(dA) / a, and the optimized absorbance A is obtained c ; 7) According to the optimized absorbance A c , calculate the optimized color value Then grade it according to the color value.

2. The method for optimizing the color value measurement of white sugar according to claim 1, characterized in that: Use a spectrophotometer to measure under the measurement parameter conditions where the absorbance value of the white granulated sugar solution is measured at a wavelength of 420 nm.

3. The method for optimizing the color value measurement of white sugar according to claim 2, characterized in that: In step 2): ① If 0.05 ≤ A ≤ 0.07 in step 1), replace the cuvette with a thickness of 10 cm and measure again to obtain the absorbance value A; ② If 0.07 < A ≤ 0.10 in step 1), there is no need to replace the cuvette, and the absorbance value A is the value obtained in step 1); ③ If 0.10 < A ≤ 0.16 in step 1), there is no need to replace the cuvette, and the absorbance value A is the value obtained in step 1); ④ If 0.30 ≤ A ≤ 0.50 in step 1), replace the cuvette with a thickness of 1 cm and measure again to obtain the absorbance value A; ⑤ If 0.50 < A ≤ 0.75 in step 1), replace the cuvette with a thickness of 1 cm and measure again to obtain the absorbance value A; For the absorbance measurement values of the remaining white granulated sugar solutions, there is no need to measure again, and the absorbance value A is the value obtained in step 1).

4. The method for optimizing the color value measurement of white sugar according to claim 3, characterized in that: The selection method of the 3 different filter combinations in step 3) is as follows: If the absorbance value A in step 2) is the one obtained in ①, the 3 different filter combinations are 2 pieces stacked, 3 pieces stacked, and 4 pieces stacked; If the absorbance value A in step 2) is the one obtained in ②, the 3 different filter combinations are single piece, 2 pieces stacked, and 3 pieces stacked; If the absorbance value A in step 2) is the one obtained in ③, the 3 different filter combinations are 2 pieces stacked, 3 pieces stacked, and 4 pieces stacked; If the absorbance value A in step 2) is the one obtained in ④, the 3 different filter combinations are single piece, 2 pieces stacked, and 3 pieces stacked; If the absorbance value A in step 2) is the one obtained in ⑤, the 3 different filter combinations are 2 pieces stacked, 3 pieces stacked, and 4 pieces stacked.

5. The method for optimizing the color value measurement of white sugar according to claim 4, characterized in that: For the 3 different filter combinations selected in step 3), the measured absorbances are A1, A2, and A3, which satisfy A1 < A2 < A3, and at the same time, the relationship with the absorbance A determined in step 2) satisfies A1 < A < A3.

6. The method for optimizing the color value measurement of white sugar according to claim 1, characterized in that: In step 1), use a spectrophotometer under the measurement condition of a cuvette thickness of 5 cm to measure the white granulated sugar solution to obtain the absorbance measurement value A.

7. The method for optimizing the color value measurement of white sugar according to claim 1, characterized in that: The filter combination is a combination of several filters with the same optical parameters stacked together.

8. The method for optimizing the color value measurement of white sugar according to claim 3, characterized in that: In step 2): If A < 0.05, the quality of the white granulated sugar is defined as refined grade; if 0.16 < A < 0.3, the quality of the white granulated sugar is defined as premium grade; if A > 0.75, the quality of the white granulated sugar is defined as second grade.

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