JP7314456B2 - milk inspection equipment - Google Patents

Description

The present invention relates to an inspection device for inspecting the fat content, protein content or vitamin B2 content of milk by measuring the intensity of backscattered light or the intensity of fluorescence generated when the milk is irradiated with light.

In milk, fat content, protein content or vitamin B2 content are important ingredients. Quality inspection of milk is performed by inspection of fat content, protein content, Ca content, somatic cell content, and the like. These quality inspections are carried out by destructive testing by inspection organizations using a portion of the milk as a sample. For this reason, it takes a long time for the quality inspection including transportation of the samples to the inspection institution, and it is impossible to inspect all the products in a non-destructive manner. Conventional non-destructive inspection techniques for milk include Patent Document 1, which irradiates milk from the outside of a container with light to measure scattering intensity, and Non-Patent Document 1 and Non-Patent Document 2, which measure forward scattered light intensity from milk. Since milk is opaque and strongly scatters incident light, these prior art techniques required a strong light source to inspect the quality inside the milk. On the other hand, vitamins such as vitamin B2, which is an important component of milk, are decomposed by light irradiation, so inspection using a strong light source was not practical.

Patent Application No. 2018-119306 Quality inspection device for fruits, vegetables and fruit juice

Ａｎｄｒｅｙ Ｂｏｇｏｍｏｌｏｖ，Ｓｔｅｆａｎ Ｄｉｅｔｒｉｃｈ，Ｂａｒｂａｒａ Ｂｏｌｄｒｉｎｉ，Ｒｕｄｏｌｆ Ｗ．Ｋｅｓｓｌｅｒ，“Ｑｕａｎｔｉｔａｔｉｖｅ ｄｅｔｅｒｍｉｎａｔｉｏｎ ｏｆ ｆａｔ ａｎｄ ｔｏｔａｌ ｐｒｏｔｅｉｎ ｉｎ ｍｉｌｋ ｂａｓｅｄ ｏｎ ｖｉｓｉｂｌｅ ｌｉｇｈｔ ｓｃａｔｔｅｒ”，Ｆｏｏｄ Ｃｈｅｍｉｓｔｒｙ １３４（２０１２）４１２－４１８．

Andrey Bogomolov, Stefan Dietrich, Barbara Boldrini, Rudolf W.; Kessler, "Quantitative determination of fat and total protein in milk based on visible light scatter", Food Chemistry 134 (2012) 412-418.

The reason why milk quality inspection using light has not been put into practical use is that milk strongly scatters light and is opaque, so a powerful light source is required, and the light scattering mechanism is complicated. Milk contains a high concentration of both light-scattering fat particles and protein particles, which strongly scatter incident light and have very low transparency. Large fat particles contained in milk are Mie scatterers, and small protein particles are Rayleigh scatterers, and the light scattering mechanism is complicated due to multiple scattering by these scatterers at high concentrations. In addition, when a strong light source is used for inspection, there is a drawback that vitamin molecules such as vitamin B2, which is an important component of milk, are photolyzed. Furthermore, since milk contains various components that may affect optical properties, it was difficult to obtain standard samples for creating calibration curves, and there was a problem in ensuring quantification.

Another inspection method using light is to measure fluorescence from vitamin B2 contained in milk, but it has been difficult to measure fluorescence without being affected by the strong light scattering of milk. Moreover, there is a drawback that when fluorescence is excited by a strong light source, vitamin molecules such as vitamin B2, which is an important component of milk, are photolyzed. These things made non-destructive inspection of milk using fluorescence difficult.

被検査試料に光を照射するための光源用光ファイバおよび散乱光または蛍光を測定するための検出器用光ファイバの両方の先端をファイバの中心間距離が１０ｍｍ以下になるようにかつ平行に設置して、容器に密着するか、直接牛乳試料に接触させるか、あるいは、牛乳試料中に浸漬することを特徴とし、かつ、光源用光ファイバおよび検出器用光ファイバの直径は３．２ｍｍ以上６．４ｍｍ以下、中心間距離は１０ｍｍ以下、光源の波長は３５０～１０００ｎｍを特徴とすることにより容器および試料の表面反射および表面散乱による照射光強度の損失および測定に与える外乱に加えて、外部からの外乱光の影響を低減することができた。
By immersing both the optical fiber for the light source and the optical fiber for the detector in the sample, we succeeded in efficiently irradiating the inside of the sample with the light from the light source. By measuring the backscattered light using the detector optical fiber, the backscattered light with high intensity can be used for the measurement, and the light source intensity required for the measurement can be reduced. This makes it possible to reduce the decomposition of vitamins contained in milk and measure them when using not only long-wavelength light but also short-wavelength light as the light source. Since the intensity of the backscattered light varies linearly with the fat or protein content of the milk, the inspection device of the present invention allows non-destructive inspection of the fat or protein content of the milk using light.

従来は、強い光散乱の影響で牛乳からの蛍光測定は困難であったが、被検査試料に光を照射するための光源用光ファイバおよび散乱光または蛍光を測定するための検出器用光ファイバの両方の先端をファイバの中心間距離が１０ｍｍ以下になるようにかつ平行に設置して、容器に密着するか、直接牛乳試料に接触させるか、あるいは、牛乳試料中に浸漬することを特徴とし、かつ、光源用光ファイバおよび検出器用光ファイバの直径は３．２ｍｍ以上６．４ｍｍ以下、中心間距離は１０ｍｍ以下、光源の波長が３５０～１０００ｎｍを特徴とした後方散乱光の強度を測定することによって、弱い励起光を使って光散乱の影響の少ない蛍光測定が可能になった。 Therefore, it has become possible to measure green fluorescence (545 nm) due to vitamin B2 contained in milk by using a violet LED (wavelength 405 nm) or a blue LED (wavelength 450 nm) as a light source. By using a periodically flashing light source (pulse light source) as a light source for irradiating milk or dairy products with light, it is possible to shorten the irradiation time of the light irradiating the milk or dairy product, which is the object to be measured, and to reduce the photodegradation of vitamin B2 contained in the milk. Furthermore, by alternately measuring and correcting the scattered light and fluorescence generated when light is irradiated from a periodically blinking light source (pulse light source) and ambient light, it is possible to eliminate the influence of ambient light on measurement results.

この発明の検査装置では、光ファイバを使って牛乳の後方散乱を測定し、被検査試料に光を照射するための光源用光ファイバおよび散乱光または蛍光を測定するための検出器用光ファイバの両方の先端をファイバの中心間距離が１０ｍｍ以下になるようにかつ平行に設置して、容器に密着するか、直接牛乳試料に接触させるか、あるいは、牛乳試料中に浸漬することを特徴とし、かつ、光 源用光ファイバおよび検出器用光ファイバの直径は３．２ｍｍ以上６．４ｍｍ以下、中心間距離は１０ｍｍ以下、光源の波長は３５０～１０００ｎｍを特徴とするため、送液配管に光ファイバを設置する簡単な構造の装置を使って牛乳の検査が可能になった。 In addition, since the measurement is performed using strong backscattering, the intensity of the light source for measurement can be reduced, which reduces the photodegradation of vitamins such as vitamin B2, which is an important component of milk, due to light irradiation, and enables energy-saving inspection. Furthermore, when a violet LED (wavelength 405 nm) or a blue LED (wavelength 450 nm) was used as the light source, in addition to the fat content inspection using light scattering intensity, vitamin B2 inspection using fluorescence could be performed simultaneously using the same inspection device. Long-term storage of milk reduces its vitamin B2 content due to photodegradation. For this reason, if the initial value of the vitamin B2 content is measured in advance, the freshness of the milk can be tested using fluorescence measurements.

An inspection device that measures light scattering and fluorescence using optical fibers immersed in milk Inspection device using multiple optical fibers immersed in milk An inspection device that uses an optical fiber installed in a pipe that conveys milk An inspection device that uses multiple optical fibers installed in a pipe that conveys milk An inspection device that uses an optical fiber installed in a bypass pipe to remove air bubbles contained in milk Inspection device using two optical fibers installed in a bypass pipe to remove air bubbles contained in milk Composition of standard sample for creating calibration curve used for quantification Variation of backscattered light intensity of milk with fat content (using 6.4 mm diameter fiber) Fluorescence spectrum of milk (Violet LED excitation, using 6.4 mm diameter fiber) Time change of fluorescence intensity of milk (purple LED excitation, using 6.4mm diameter fiber) Fluorescence spectrum of milk (blue LED excitation, using 6.4 mm diameter fiber) Time change of fluorescence intensity of milk (blue LED excitation, using 6.4 mm diameter fiber) Change in fluorescence intensity of milk with fat content (violet LED excitation)

The inspection apparatus of the present invention comprises a light source 1, a light source optical fiber 2, a photodetector 3, a detector optical fiber 4, a cylindrical glass container 5, and milk or milk product 6, as shown in FIG. The inspection apparatus shown in FIG. 1 using an optical fiber bundle in which the fibers for the light source and the detector are bundled together as an optical fiber to be immersed in the sample, the inspection apparatus shown in FIG. Furthermore, by using the inspection device shown in FIG. 5 or 6 in which an optical fiber is installed in a bypass pipe provided to remove air bubbles contained in milk, it is possible to inspect without the influence of air bubbles contained in the milk being fed.

The light emitted from the light source 1 is applied to the milk or milk product 6 filled in the cylindrical glass container 5 through the light source optical fiber 2 immersed in the milk or milk product 6 . Backscattered light generated from the milk or dairy product 6 is guided to the scattered light detector 3 through the detector optical fiber 4 immersed in the milk or dairy product 6, and the intensity of the scattered light can be measured. As a light source for measuring the backscattered light of milk, an LED capable of emitting light with a wavelength in the range of 350 nm or more and 1000 nm or less can be used. Halogen lamps can also be used as light sources. Violet and blue LEDs can be used as excitation light sources for fluorescence quality inspection of milk.

As the optical fiber for the light source and the optical fiber for the detector of the inspection apparatus of the present invention, an optical fiber bundle in which a plurality of optical fibers are bundled, a single-core optical fiber, or a combination of an optical fiber bundle and a single-core optical fiber can be used. As the light source optical fiber and the detector optical fiber used in the inspection apparatus of the present invention, optical fiber bundles with the same diameter or single core optical fibers with the same diameter can be used, but single core optical fibers with different diameters and optical fiber bundles with different diameters can also be used in combination. When optical fiber bundles are used, it is also possible to use a combination of a light source optical fiber bundle and a detector optical fiber bundle having different optical fiber bundle diameters. When an optical fiber with a small diameter or an optical fiber bundle with a small diameter is used as the optical fiber for the light source, the amount of light irradiating the sample to be inspected can be reduced, so that photodecomposition of the sample to be inspected can be reduced. When the amount of light irradiation during measurement is small, the scattering intensity and fluorescence intensity also decrease. However, by using an optical fiber with a large diameter or an optical fiber bundle with a large diameter as the optical fiber for the detector, it is possible to measure weak light scattering and weak fluorescence from the test sample with high detection sensitivity. By using a combination of a light source optical fiber with a small diameter and a detector optical fiber with a large diameter, it is possible to reduce the quality change of the sample to be inspected due to light irradiation.

Commercially available whole milk, low-fat milk, and non-fat milk were combined to prepare a standard sample for creating a calibration curve shown in FIG. Standard samples with constant protein content and different fat contents and standard samples with constant fat content and different protein contents were prepared. The backscattered light spectrum and intensity of milk were measured using the inspection apparatus of FIG. White LEDs, violet LEDs, blue LEDs, green LEDs, yellow LEDs, red LEDs, and near-infrared LEDs (wavelengths of 850 nm and 940 nm) were used as light sources. An optical fiber spectrometer was used as a detector. As optical fibers, optical fiber bundles with a diameter of 6.4 mm and a diameter of 3.2 mm were used. When the optical fiber was immersed in milk and then irradiated with light from a light source, a spherical light scattering image was observed inside the milk centered on the tip of the optical fiber. From this result, it was found that the scattered light during the measurement spreads almost spherically around the tip of the immersed optical fiber. Using white LEDs, violet LEDs, blue LEDs, green LEDs, yellow LEDs, red LEDs, and near-infrared LEDs (wavelengths of 850 nm and 940 nm), samples with a constant protein content and different fat contents were measured. It was also confirmed that the light scattering intensity changed linearly with changes in the fat content even when an optical fiber with a diameter of 3.2 mm was used. When the same light scattering intensity was measured using samples with a constant fat content and different protein contents, it was confirmed that the light scattering intensity changed linearly with the protein content. Using this linear relationship between light scattering intensity and fat content, and the linear relationship between light scattering intensity and protein content, it was possible to examine the fat and protein content of milk by measuring the backscattered light intensity.

Fluorescence spectra and fluorescence intensities were measured using commercially available whole milk, low-fat milk and non-fat milk. A violet LED and a blue LED were used as the light source 1 using the inspection apparatus of FIG. An optical fiber spectroscope was used as the photodetector 3 . The optical fiber 4 for the detector used an optical fiber bundle with a diameter of 6.4 mm and a diameter of 3.2 mm. When a violet LED and a blue LED were used as light sources, as shown in FIGS. 9 and 11, scattered light and fluorescence having a peak near a wavelength of 545 nm could be measured. Moreover, as shown in FIGS. 10 and 12, the fluorescence intensity gradually decreased with the light irradiation time. This is considered to be due to photodecomposition of vitamin B2 in the vicinity of the immersed optical fiber due to light irradiation for measurement. As shown in FIGS. 10 and 12, it was confirmed that stirring the milk sample during measurement removes the milk from the vicinity of the immersed optical fiber, thereby increasing the fluorescence intensity. In particular, when an optical fiber bundle with a diameter of 3.2 mm, which has a small optical fiber diameter, is used, the light source intensity for measurement can be reduced, so the light irradiation range can be narrowed, and fluorescence measurement without the influence of light scattering by fat particles has become possible. It was found that the effect of light scattering due to fat was extremely small when fluorescence measurements were performed using an optical fiber bundle with a diameter of 3.2 mm and a violet LED as an excitation light source. Furthermore, when an optical fiber bundle with a diameter of 3.2 mm was used as an excitation light source with a violet LED, it was confirmed that the time change in fluorescence intensity could be reduced, and it was found that the photodegradation of vitamin B2 due to light irradiation during measurement could be reduced. By measuring fluorescence intensity using a violet LED as an excitation light source and an optical fiber bundle with a diameter of 3.2 mm, it is possible to inspect the vitamin B2 content under measurement conditions that are free from the effects of light scattering and that can reduce the decomposition of vitamin B2 due to light irradiation.

The inspection device of the present invention can be used for nondestructive quality inspection of milk. In addition to the conventional quality inspection that combines sample sampling and destructive measurement by an inspection agency, non-destructive and rapid 100% inspection becomes possible. Since the inspection uses the intensity of backscattered light and the intensity of fluorescence, measurement can be performed simply by immersing the optical fiber in the sample, and rapid inspection is possible using a simple device. It does not require the use of a powerful light source and can also be powered by batteries, making it an excellent portable inspection device that can be used in a variety of locations.

Reference Signs List 1 light source 2 light source optical fiber 3 photodetector 4 detector optical fiber 5 glass cylindrical container 6 milk or dairy product 7 liquid feeding pipe 8 valve 9 valve 10 bubble removal bypass pipe

Claims (11)

An optical fiber for a light source for irradiating milk or a dairy product with light from a light source to generate scattered light or fluorescence, and an optical fiber for a detector for measuring the intensity of the scattered light or the intensity of the fluorescence, and converting the measured scattered light intensity or fluorescence intensity into a fat content, a protein content, or a vitamin content using a calibration curve prepared in advance.The quality inspection apparatus is characterized in that both ends of an optical fiber for a light source for irradiating light onto a sample to be inspected and an optical fiber for a detector for measuring scattered light or fluorescence are arranged parallel to each other so that the distance between the centers of the fibers is 10 mm or less, and are brought into close contact with the container, brought into direct contact with the milk sample, or immersed in the milk sample; A quality inspection device for milk or dairy products, wherein the wavelength of is 350 to 1000 nm. 2. The quality inspection apparatus for milk or dairy products according to claim 1 , wherein the tip of at least one of the light source optical fiber for irradiating the milk or dairy product with light from the light source and the detector optical fiber for detecting scattered light or fluorescence is immersed in the milk or dairy product, and the angle formed by the light source optical fiber for irradiating light and the detector optical fiber for measuring the scattered light intensity or the fluorescence intensity is in the range of 170 degrees or more and 180 degrees or less. The quality inspection apparatus for milk or dairy products according to any one of claims 1 and 2 , wherein at least the portion of the tip of the light source optical fiber for irradiating the milk or dairy product with light from the light source and the detector optical fiber for detecting scattered light or fluorescence is bundled into one. 4. The milk or dairy product quality inspection apparatus according to any one of claims 1 to 3 , wherein the light source optical fiber for irradiating the milk or dairy product with light from the light source and the detector optical fiber for detecting scattered light or fluorescence are installed in a liquid feeding pipe for transporting the milk or dairy product. The milk or dairy product quality inspection apparatus according to any one of claims 1 to 4 , wherein the light source optical fiber for irradiating the milk or dairy product with light from the light source and the detector optical fiber for detecting scattered light or fluorescence are installed in a bypass pipe having a function of removing air bubbles contained in the milk or dairy product. 6. The apparatus for quality inspection of milk or dairy products according to any one of claims 1 to 5 , wherein both the fluorescence intensity and the scattered light intensity generated when the milk or dairy product is irradiated with light are measured, and one of vitamin content and fat content, vitamin content and protein content, or vitamin content and fat content and protein content is measured using a calibration curve prepared in advance. 7. The milk or dairy product quality inspection device according to any one of claims 1 to 6 , wherein the freshness of the milk or dairy product is measured by comparing the fluorescence intensity generated when the milk or dairy product is irradiated with light with the fluorescence intensity measured in advance. The milk or dairy product quality inspection apparatus according to any one of claims 1 to 7, wherein a periodically flickering light source is used as the light source for irradiating the milk or dairy product with light. The quality inspection apparatus for milk or dairy products according to any one of claims 1 to 8 , wherein the diameter of the optical fiber or optical fiber bundle used as the light source optical fiber for irradiating the milk or dairy product with light from the light source and the diameter of the optical fiber or optical fiber bundle used as the detector optical fiber for detecting scattered light or fluorescence are the same. The quality inspection apparatus for milk or dairy products according to any one of claims 1 to 9 , wherein the diameter of the optical fiber or optical fiber bundle used as the light source optical fiber for irradiating the milk or dairy product with light from the light source and the diameter of the optical fiber or optical fiber bundle used as the detector optical fiber for detecting scattered light or fluorescence are different. The quality inspection apparatus for milk or dairy products according to any one of claims 1 to 10 , wherein the diameter of the optical fiber or optical fiber bundle used as the light source optical fiber for irradiating the milk or dairy product with light from the light source is smaller than the diameter of the optical fiber or optical fiber bundle used as the detector optical fiber for detecting scattered light or fluorescence.

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