JPH04208842A - Method and device for measuring sugar content of vegetable and fruit - Google Patents

Abstract

PURPOSE:To improve the estimating accuracy of sugar contents of vegetables and fruits by measuring absorbancy against a wavelength in a near infrared band and calculating the second derivating of the absorbancy. CONSTITUTION:Reflected light from a vegetable or fruit to be measured is received and the absorbancy against a wavelength of 2,500nm in a near infrared band is measured with a spectroscope. In this method and device for measuring sugar content of the vegetable or fruit from the measured value of the spectroscope, the absorbancy against the wavelength of 912nm attributable to the sugar and the wavelength of, for example, 888nm belonging to an element having a specific relation with the sugar are measured and the second derivative calculating section 12 calculates the quadratic differential values of the absorbancies. Then a sugar content calculating section 13 calculates the sugar content of the vegetable or fruit on the basis of the calculated results of the section 12.

Description

[Detailed description of the invention]

[0001]

[Field of Industrial Application] The present invention relates to a method and apparatus for measuring the sugar content of fruits and vegetables, which non-destructively measures the sugar content of fruits and vegetables from light reflected from the fruits and vegetables obtained by irradiating the fruits and vegetables with light. The present invention relates to a method and apparatus for measuring the sugar content of fruits and vegetables, which measures the absorbance of wavelengths in the near-infrared region and measures the sugar content of fruits and vegetables based on the measured values. [0002]

[Prior Art] In general, the sugar content of fruits and vegetables, such as vegetables and fruits, is an important factor in determining the quality of fruits and vegetables. Measured by analysis etc. However, since this method is a destructive test and requires a long time to inspect, in recent years, attention has been focused on non-destructive testing based on the optical characteristics of fruits and vegetables, which allows testing of many objects in a short time. Therefore, methods have been developed that can be used for quality control of fruits and vegetables. Recently, methods of measuring the sugar content of fruits and vegetables using light with wavelengths in the near-infrared region have been studied. [0003] Conventionally, as a method for measuring the sugar content of fruits and vegetables using light with a wavelength in the near-infrared region, for example, Japanese Patent Application Laid-Open No. 1-301
The one published in Publication No. 147 is known. this※
*Receives reflected light from the fruits and vegetables to be tested; 3.
Measuring the reflection intensities corresponding to at least three wavelengths (λ1, λ2, λ3) included in the near-infrared region of 0 μm or less,
From this, the reflectance at each wavelength (R1 (A1), R2
(A2), R3 (A3)), and using these reflectances, the sugar content is calculated according to the following formula 2. [0004] C-aO+al R1(A1)+a2
R2(A2)+a3 R3(A3) (Formula 2) [0005] Here, at least three different wavelengths are
0.90-1.10 μm, 1.11-1.3171 m. 1.24-1.44 μm, 1.35-1.55 μm. 1.58-1.78μm, 1. 72~1.92μ
It is included in any range of m. Also, a
O, al, a2. a3 is a coefficient determined by the least squares method using reflectance and actually measured sugar content measured in a sufficiently large population. [0006]

[Problems to be Solved by the Invention] However, in the above-mentioned conventional sugar content measuring method, an appropriate wavelength (λ1, λ2, λ3) that falls within any of the above ranges is determined for each subject.
Since you have to select and then perform the measurement,
This makes the process of selecting a wavelength more complicated, and the formula changes every time the wavelength changes, making the calculation process more complicated and making the measurement more complicated. That is, for example, if we take apples as an example of fruits and vegetables, the wavelength must be reset for each type of apple (for example, "Fuji", "Starking", etc.), and the formula ( (calibration curve) will be different. [0007] Furthermore, in calculating the sugar content, the reflectance is determined by extracting the weak signal of the original spectrum, so since the signal is weak, noise is likely to be directly included in the data and its influence is large. Therefore, even if the optimum wavelength could be selected, there was a problem in that it would have a negative effect on the estimation accuracy of sugar content and would not necessarily be used for accurate quality determination. [0008] The present invention has been made in view of the above-mentioned problems, and has the object of making it possible to fix the formula for calculating sugar content, and to improve the accuracy of estimating sugar content. [0009]

[Means for Solving the Problems] The technical means of the present invention for solving such problems consists of: [0010] receiving reflected light from fruits and vegetables to be examined;
In the sugar content measurement method, which measures the absorbance at a wavelength in the near-infrared region of 2500 nm or less and uses this measurement value to measure the sugar content of fruits and vegetables, the absorbance at a wavelength that is attributable to sugar and an element that has a predetermined relationship with sugar is used. The absorbance of the associated wavelength is measured**, the second-order differential value of these absorbances is calculated, and the sugar content of fruits and vegetables is calculated based on the result of this calculation. [0011] And the wavelength attributed to the above sugar is 912
A wavelength near nm is effective. [0012] In addition, 2500 nm was applied to the fruits and vegetables to be tested.
A light source unit that irradiates light that includes light with wavelengths in the near-infrared region below; a light receiving unit that receives reflected light from the fruits and vegetables; A spectrometer that separates light with wavelengths that belong to elements that have a predetermined relationship with sugar, and absorbance of wavelengths that belong to sugar and wavelengths that belong to elements that have a predetermined relationship with sugar from the reflected light received by the light receiving part. Comprising an absorbance calculation unit that calculates absorbance, a second-order differential calculation unit that calculates second-order differential values of these absorbances, and a sugar content calculation unit that calculates sugar content of fruits and vegetables using the calculated second-order differential values. There is a sugar content measuring device for fruits and vegetables. [0013] The sugar content calculation section calculates the following formula 1.
It is effective to have a function to calculate the sugar content. In Equation 1, λ is the wavelength, A1 (2, 1) is the absorbance at wavelength λ1 that belongs to sugar, A2 (A2) is the absorbance at wavelength λ2 that belongs to an element that has a predetermined relationship with sugar, K0,
K1 and K2 are coefficients determined by the least squares method using the absorbance measured in a sufficiently large population and the actually measured sugar content. [0014]

[Math. 2] d”Ayu(λ+) ct” AI(n,)C=
KO + Ki + 2
(Formula 1) % formula %: A, fλ, ): Absorbance at wavelength λ1 A t fλ,
): Absorbance KO at wavelength λ, 1. 2: Coefficient [0015]

[Operation] According to the sugar content measuring method and sugar content measuring device having the above configuration, reflected light from the fruits and vegetables to be tested is received,
Measure the absorbance at wavelengths attributed to sugar and the absorbance at wavelengths attributed to elements that have a predetermined relationship with sugar, calculate the second derivative of these absorbances, and calculate the sugar content of fruits and vegetables based on the results of this calculation. calculate. [0016] In this case, since the calculation is performed using the second-order differential value, the data is processed from which noise due to the background has been removed, and more accurate measurement can be performed. In addition, the above 2
Since absorbance data for different wavelengths are derived from different absorptions, they can be treated as data that are primarily independent of each other. [Oo 17]

[Embodiments] Hereinafter, a method and apparatus for measuring sugar content of fruits and vegetables according to embodiments of the present invention will be described based on the accompanying drawings. The method for measuring the sugar content of fruits and vegetables according to the example is carried out using the sugar content measuring device according to the example, so it will be explained along with the operation of this sugar content measuring device. [0018] The apparatus for measuring the sugar content of fruits and vegetables according to the embodiment measures the sugar content of apples as fruits and vegetables, and as shown in FIGS. The sugar content measuring device measures the sugar content of the apple when the apple is placed at the measurement position. , a light source unit 4 that irradiates the apple of the test subject 1 with light containing light with a wavelength in the near-infrared region of 2500 nm or less; and a spectrometer 5 such as a monochromator that separates light into wavelengths belonging to elements that have a predetermined relationship with sugar. A light receiving section 6 receives the reflected light reflected from the light receiving section 1, converts it into an electric signal, and performs A/D conversion. Based on the signal from the light receiving section 6, the display control of the display section 7 and the sorting machine 8
A control section 10 is provided for controlling the drive of. [00201 As shown in FIG. 2, the control unit 10 includes an absorbance calculation unit 11 that calculates the absorbance of a wavelength attributed to sugar and the absorbance of a wavelength attributed to an element having a predetermined relationship with sugar from the signal from the light receiving unit 6. , a second-order differential calculation unit 12 that calculates the second-order differential values of these absorbances, and a sugar content calculation unit 13 that calculates the sugar content of fruits and vegetables using the calculated second-order differential values.
and a determination unit 14 that determines the accuracy grade based on the calculation result of the sugar content calculation unit 13. The functions of each part are realized, for example, by the functions of a microprocessor. [00211 The sugar content calculating section 13 has a function of calculating sugar content using Equation 1 below. [0022]

[Math. 3] d” A, (λt) ci”8*(t*)C
= KO + Kl + 2
(Formula 1) % formula %: A r [λI): Absorbance at wavelength λ, AX [E,
] - absorbance at wavelength KO, K1. 2: Coefficient [0023] In formula 1, λ is the wavelength, Al(A1)
is the absorbance at wavelength λ1 attributed to sugar, A2 (A2) is the absorbance at wavelength λ2 attributed to an element in a predetermined relationship with sugar, K
0, K1, and K2 are coefficients determined by the least squares method using the absorbance measured in a sufficiently large population and the actually measured sugar content. [002411 constant part 14 has the calculated sugar content, for example, A, B, and C ranked in descending order of sugar content.
It has a function to determine which rank it belongs to among the three ranks. [0025] The display unit 7 is equipped with a display 15 that displays the sugar content calculated by the sugar content calculation unit 13, and has color-coded lamps 16 corresponding to, for example, A, B, and C ranks. It has a function of lighting a corresponding lamp based on the determination result of the section 14. [0026] The sorting machine 8 sorts the apples ranked, for example, into A, B, and C ranks based on the determination result of the determination unit 14, by rank by means of, for example, changing the route of the belt conveyor 2. It has a sorting function. [0027] Further, the control unit 10 sequentially irradiates light with a wavelength that belongs to sugar and light with a wavelength that belongs to an element that has a predetermined relationship with sugar while measuring the apple at the measurement position. It has a function to control the spectrometer 5. [0028] Next, the wavelength of the irradiation light will be explained in detail. In the examples, the wavelengths attributed to the sugars are:
912 nm is used. This is done by selecting absorption wavelengths attributed to sugars based on well-known assignment tables. Generally, the frequency in the near-infrared region is a harmonic or a combination of a reference vibration existing in the infrared region. Here, the wavelength 912
※※nm belongs to the third overtone of the C-H group. [0029] In making this selection, the attribution relationship was confirmed in advance through the following experiment. First, near-infrared spectrum data analysis will be performed using dozens of apple samples. For example, regression analysis is performed between the values of the second-order differential spectra of these spectra and the manually analyzed values (actually measured values),
Several statistically significant wavelengths were selected from among the wavelengths showing negative correlation coefficients, and then the attribution of these wavelengths to sugars was confirmed, and then 912 nm was selected as the optimal one. FIG. 3 is a correlation diagram of sugar content in the apple type "Fuji". Here, wavelengths other than 912 nm may be wavelengths that do not belong to sugars (for example, 774 nm, 110 nm, etc.).
At 32n and 1176 nm, absorptions other than C-H groups and O-H groups are observed. ), or because it was statistically disadvantageous, it was excluded from selection. In addition, similar experiments were conducted not only for "Fuji" but also for other samples such as "Starking" and "a mixture of Fuji and Starking", and it was confirmed that 912 nm is the optimal wavelength. [00301 Furthermore, the following experiment confirmed that the wavelength of 912 nm is a wavelength that belongs to sugar. Since there are mainly three types of sugar in apple fruits: sucrose, fructose, and glucose, an aqueous solution of this was prepared and near-infrared spectroscopy was performed to analyze the absorption wavelength. The correlation coefficients at each wavelength are shown in FIGS. 4 to 6. As can be seen from these measured values, the wavelength of 912 nm has a high correlation and is found to be derived from sugar. Note that when taking the second-order differential value of the value of the spectrum that physically has a positive correlation with the sugar concentration, this value becomes a negative value, so it shows a negative correlation with the concentration. Therefore, in FIGS. 4 to 6, wavelengths showing a positive correlation are determined to be wavelengths unrelated to sugar. [00311 Next, in the examples, 888 nm is used as a wavelength belonging to an element that has a predetermined relationship with sugar. This is done by selecting several statistically significant wavelengths with high correlation through near-infrared spectral data analysis similar to the above, and selecting wavelengths that are not considered to belong to sugars from among these. [0032] Therefore, the sugar content measuring device according to this embodiment operates as follows. When the apples conveyed by the belt conveyor 2 reach the measurement position, the irradiation unit 3
The apple is irradiated with light of a wavelength that belongs to sugar and light of a wavelength that belongs to an element that has a predetermined relationship with sugar. Then, at the measurement position, the light reflected from the subject 1 is received by the light receiving section 6 and outputted to the control section 10 as an electrical signal. In the control unit 10, the absorbance calculation unit 11 calculates the absorbance of the wavelength attributed to sugar and the absorbance of the wavelength attributed to an element having a predetermined relationship with sugar from the signal from the light receiving unit 6, and calculates the absorbance of the wavelength attributed to the sugar and the element having a predetermined relationship with the sugar, 12 calculates the second-order differential values of these absorbances, and the sugar content calculation unit 13 uses the calculated second-order differential values to calculate the sugar content of fruits and vegetables. This calculation result is displayed on the display section 7. [0033] In this case, since the calculation is performed using the second-order differential value, the noise due to the background can be removed from the data compared to the case where the original spectrum is used as data, and the accuracy of sugar content estimation is improved accordingly. will improve. still,
Figure 7 shows the near-infrared absorption spectrum of apple fruit. (a) is the original spectrum, and (b) is the second derivative spectrum. [0034] In addition, in this case, the formula uses the absorbance of the wavelength attributed to the sugar and the absorbance of the wavelength attributed to the element that has a predetermined relationship with the sugar, so 2 is linearly independent of each other. It becomes a calibration curve for variables, and the sugar content can be calculated with higher accuracy. [0035] Furthermore, since the wavelengths attributed to sugar and the wavelengths attributed to elements that have a predetermined relationship with sugar are determined in advance, the same calibration curve can be used even if the type of apple to be measured, production area, or cultivation method is different. It becomes possible to measure the sugar content. Therefore, even if the types, production areas, and cultivation methods are different, there is no need to select measurement wavelengths one by one, and the efficiency of measurement work can be improved accordingly. [00361 Next, experimental results using the above device will be shown. FIG. 8 is a graph showing the correlation between the NIR value (estimated sugar content calculated using formula 1 above) and manual analysis value (actual value) when measuring 40 samples of the apple type "Fuji". . In this case, the correlation coefficient is 0.94, which is a very high value. [0,0371 Let's compare this with the conventional method. Figure 9 shows the results obtained using absorbance at wavelengths of 912 nm and 888 nm, using the same method as the conventional method.
NIR when measuring 40 samples at "Fuji"
It is a graph showing the correlation between values and manual analysis values. According to this, the correlation coefficient is as low as 0.66. Therefore, it is known that the measurement method of this example is intended to improve accuracy by reducing the influence of noise due to the background. [0038] In addition, FIG. 10 shows the NIR when measuring 40 samples of the apple type “Star King”.
It is a graph showing the correlation between values and manual analysis values. Figure 11 shows
It is a graph showing the correlation between NIR values and manual analysis values when 80 specimens were measured for a mixture of apple types "Fuji" and "Starking". It can be seen from this figure that high correlations can be found in other types as well. In other words, since the absorbance is calculated at a wavelength that is universally determined in advance, even if the apples to be measured are different, there is no need to select the measurement wavelength and re-determine the calibration curve, and the same calibration curve can be used. It becomes possible to make measurements using [0039]The determining unit 14 then determines to which rank the calculated sugar content belongs, for example, among the three ranks of A, B, and C ranks. Also,
This determination result is displayed on the lamp 16 of the display section 7. Further, the sorting machine 8 sorts the apples ranked, for example, A, B, and C ranks, based on the determination result of the determination unit 14, by rank. [00401 In the above example, 912 nm was used as the wavelength belonging to sugar, and 888 nm was used as the wavelength belonging to the element having a predetermined relationship with sugar, but it is not necessarily limited to this, and it may be used as appropriate. Good choice. Further, in the above embodiment, the present invention was applied to the measurement of apples, but the present invention is not necessarily limited to this, and it goes without saying that the present invention may be applied to other fruits and vegetables. Further, the number of terms in the formula is not limited to the above, and may be determined to be calculated using second-order differential values of absorbance at three or more wavelengths. [00411] [Effects of the Invention] As explained above, according to the fruit and vegetable sugar content measuring method and accuracy measuring device of the present invention, since sugar content is calculated using the second derivative of absorbance, the original spectrum is used as data. Compared to the case, the noise due to the background can be erased from the data and only,
The accuracy of sugar content estimation can be improved. [0042] Furthermore, since the absorbance of the wavelength attributed to the sugar and the absorbance of the wavelength attributed to the element having a predetermined relationship with the sugar are used, a fixed calibration curve of two variables that are linearly independent of each other is used. can be created, and the sugar content can be calculated with high accuracy. [0043] Furthermore, since the wavelengths attributed to sugar and the wavelengths attributed to elements that have a predetermined relationship with sugar are determined in advance, the same calibration curve can be used even if the types of fruits and vegetables to be measured, production areas, cultivation methods, etc. are different. It becomes possible to measure sugar content using this method. Therefore, even if the species, production area, cultivation method, etc. are different, there is no need to select the measurement wavelength one by one, and the efficiency of the measurement work can be improved accordingly. [0044] That is, according to the present invention, since wavelengths effective for determining the sugar content of fruits and vegetables are determined in consideration of wavelength attribution, the sugar content of fruits and vegetables can be measured non-destructively with good accuracy. By introducing this into a fruit and vegetable sorting line, it is possible to inspect all fruits and vegetables.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing a sugar content measuring device according to an embodiment of the present invention.

FIG. 2 is a block diagram showing main parts of a sugar content measuring device according to an embodiment of the present invention.

FIG. 3 is a correlation diagram of sugar content in apple “Fuji”.

FIG. 4 is a correlation diagram of a sucrose aqueous solution.

FIG. 5 is a correlation diagram of a fructose aqueous solution.

FIG. 6 is a correlation diagram of a glucose aqueous solution.

FIG. 7 is a diagram showing a near-infrared absorption spectrum of apple fruit.

FIG. 8 is a graph showing the correlation between NIR values and manual analysis values for apple “Fuji”.

FIG. 9 is a graph showing the correlation between NIR values and manual analysis values for the apple "Fuji" measured by a method similar to the conventional method.

FIG. 10 is a graph showing the correlation between NIR values and manual analysis values for the apple "Star King".

FIG. 11 is a diagram showing the correlation between NIR values and manual analysis values in a mixture of apple types "Fuji" and "Starking".

[Explanation of symbols]

1.Test subject 3 Irradiation section 4. Light source 5 Spectrometer 6 Light receiving part 7 Display section 8 Sorting machine 10 Control section 11 Absorbance calculation section 12 Second-order differential calculation section 13 Sugar content calculation section 14 Judgment section

[Figure 3] (72) Inventor: Grafted by Fujitoshi, Aomori Prefecture Industrial Technology Development Center, 2O2-4 Ashiya, Aomori City, Aomori Prefecture (72) Inventor: Takeo, 5-1 Kinzoku-cho, Hirosaki City, Aomori Prefecture Inside Towa Denki Kogyo Co., Ltd.

Claims (4)

[Claims] Claim 1: Receives reflected light from fruits and vegetables to be tested;
In a sugar content measurement method that measures the absorbance at a wavelength in the near-infrared region of 2500 nm or less and uses this measurement value to measure the sugar content of fruits and vegetables, the absorbance at a wavelength attributed to sugar and the absorbance attributable to an element having a predetermined relationship with sugar are 1. A method for measuring the sugar content of fruits and vegetables, comprising: measuring the absorbance of wavelengths, calculating second-order differential values of these absorbances, and calculating the sugar content of the fruits and vegetables based on the calculation results. 2. The method for measuring sugar content according to claim 1, wherein the wavelength attributed to sugar is a wavelength around 912 nm. 3. A light source unit that irradiates the fruits and vegetables to be tested with light containing light with a wavelength in the near-infrared region of 2500 nm or less, a light receiving unit that receives reflected light from the fruits and vegetables, and the irradiated light and the reflected light. A spectrometer that splits either of the above into light with a wavelength that belongs to sugar and light with a wavelength that belongs to an element that has a predetermined relationship with sugar; an absorbance calculation section that calculates the absorbance of a wavelength belonging to an element that has a predetermined relationship with , a second-order differential calculation section that calculates the second-order differential values of these absorbances, and a second-order differential calculation section that calculates the second-order differential values of these absorbances. A sugar content measuring device for fruits and vegetables, comprising: a sugar content calculation section that calculates the sugar content of fruits and vegetables. 4. The apparatus for measuring the sugar content of fruits and vegetables according to claim 3, wherein the sugar content calculation section has a function of calculating the sugar content using Equation 1 below. In formula 1, λ is the wavelength, A1 (λ1) is the absorbance at wavelength λ1 attributed to sugar,
A2 (λ2) is the absorbance at wavelength λ2 that belongs to an element that has a predetermined relationship with sugar, and K0, K1, and K2 are determined by the least squares method using the absorbance measured in a sufficiently large population and the measured sugar content. is the coefficient. [Math 1] ▲There are mathematical formulas, chemical formulas, tables, etc.▼ (Formula 1) C: Sugar content λ: Wavelength A_1 (λ_1): Absorbance at wavelength λ_1 A_2 (
λ_2): Absorbance K0, K1, K2 at wavelength λ_2
:coefficient