Method for discriminating hair mixed in food by fluorescence analysis

Abstract

The purpose of the present invention is to provide a method for discriminating mixed hair with which it is possible to easily determine whether hair mixed in food has been mixed in a manufacturing process or after product opening; that is, the timing when the mixing has occurred. The present invention provides a method for discriminating mixed hair, the method comprising: analyzing, by a fluorescence analysis method using irradiation with ultraviolet rays or visible light having a wavelength longer than 254 nm, the degree of penetration of a fluorescent substance in food into hair mixed in the food; and discriminating the timing when the hair has been mixed on the basis of the analysis result of the degree of penetration.

Description

Method for discriminating hair mixed in food by fluorescence analysis

[0001] The present invention relates to a method for discriminating whether hair mixed in food entered during the manufacturing process or after the product is opened, that is, the timing of hair contamination, based on the analysis result of the penetration degree of fluorescent substances in food into the contaminated hair.

[0002] Food is ingested into the body, and naturally, its safety must be guaranteed. Therefore, in quality control of food manufacturing, for example, matters that can cause contamination by foreign substances such as hair must be thoroughly eliminated. To thoroughly implement such quality control, it is necessary to accurately grasp the actual situation of foreign matter contamination. For this purpose, it is first important to verify the timing of contamination, i.e., whether the foreign substance found in food entered during the manufacturing process or after the product was opened.

[0003] For example, with respect to verification of hair contamination, methods for discriminating the timing of foreign matter contamination based on the effect of heating during the manufacturing process have been studied. Non-Patent Document 1 describes that hair is made of keratin protein and morphological changes are observed through heat treatment, and discusses whether the discrimination can be performed based on such morphological changes. Specifically, it describes that heating at 200°C to 300°C is required for morphological changes to remain after heat treatment, and almost no morphological changes of hair are observed in the heat treatment of about 100°C performed in food manufacturing processes, so it is difficult to estimate the timing of hair contamination based on heat treatment-induced morphological changes through morphological inspection.

[0004] In addition, Non-Patent Document 1 discloses that when hair is heated, components inside the hair undergo changes, and catalase present in biological tissue disappears during heating, so the presence or absence of heating can be determined based on changes in catalase activity. It also discloses that if the hair root is present, there are cells that exhibit enzyme activity, so catalase activity can be measured. However, it is also described that in practice, most hair that is a contaminating foreign substance often does not have a hair root, and catalase activity itself changes under various conditions, so it is unreliable to draw conclusions on the presence or absence of heating.

[0005] Furthermore, Patent Document 1 describes a method for identifying foreign substances in food, which determines the time of contamination based on the results of an analysis of the degree to which food components penetrate into foreign substances mixed into food. It also describes that the analysis of the degree to which food components penetrate into foreign substances is performed using a fluorescence analysis method. Patent Document 1 describes that the fluorescence analysis method involves measuring the spectrum and intensity of fluorescence emitted when ultraviolet light or short-wavelength visible light is irradiated onto a fluorescent substance using a fluorophotometer or the like. It can be used for foods that contain fluorescent substances. For example, it describes that if the fluorescent substance is curcuminoids contained in turmeric, an ingredient in curry, it can fluoresce in a yellowish-green color by irradiating it with ultraviolet light at a wavelength of 254 nm.

[0006] However, in this field, there was still a strong need for a new method that would allow for simple and efficient verification of when foreign objects such as hair found in food were introduced, whether during the manufacturing process or after the product was opened.

[0007] Japanese Patent Publication No. 2005-83804

[0008] "Method for Identifying Contaminated Hair" by Hajime Sato, published by Science Forum Co., Ltd., November 7, 2000 (pp. 7-8, 88-91, 107-108).

[0009] The present invention aims to provide a method for identifying contaminated hair that can easily determine whether the hair found in food was introduced during the manufacturing process or after the product was opened, thus allowing for easy determination of the timing of the contamination.

[0010] As a result of diligent research to solve the above problems, the inventors have found that the degree to which fluorescent substances in food penetrate into hair mixed in food can be easily analyzed by a fluorescence analysis method in which ultraviolet or visible light with a wavelength longer than 254 nm is irradiated onto the surface or cross-section of the mixed hair. Based on the results of the penetration analysis, it is possible to easily determine whether the mixed hair was introduced during the manufacturing process or after the product was opened.

[0011] The present invention is based on these novel findings and includes the following inventions: [1] A method for identifying contaminated hair, which involves analyzing the degree of penetration of a fluorescent substance in food into hair that was mixed into food using a fluorescence analysis method that utilizes irradiation with ultraviolet or visible light with a wavelength longer than 254 nm, and determining the time of contamination of the hair based on the analysis results of the degree of penetration. [2] The method of [1], wherein the fluorescent substance is curcuminoid. [3] The method of [1] or [2], wherein the fluorescence analysis method utilizes irradiation with ultraviolet or visible light with a wavelength of 330 nm to 450 nm. [4] The method of any of [1] to [3], wherein the hair was irradiated with light between the time it was discovered mixed into food and the time it was analyzed. [5] The method of any of [1] to [4], wherein the analysis of the degree of penetration of a fluorescent substance in food into hair is performed based on a cross-section of the hair. [6] In the case of food products that have been heat-treated during the manufacturing process, the timing of hair contamination is determined by comparing the degree of penetration of the fluorescent substance in the food into the contaminated hair with the degree of penetration of the fluorescent substance in the food into hair that has been heat-treated under conditions equivalent to the said heat treatment, using any of the methods [1] to [5]. [7] In the case of food products that have been heat-treated during the manufacturing process, the timing of hair contamination is determined by heat-treating a portion of the contaminated hair under conditions equivalent to the said heat treatment, and comparing the degree of penetration of the fluorescent substance in the food into the heat-treated contaminated hair with the degree of penetration of the fluorescent substance in the food into the unheat-treated contaminated hair, using any of the methods [1] to [6]. [8] In the case of food products that have not been heat-treated during the manufacturing process, the timing of hair contamination is determined by comparing the degree of penetration of the fluorescent substance in the food into the contaminated hair with the degree of penetration of the fluorescent substance in hair that has been preserved by being mixed into the food for a certain period of time. This is done by any of the methods [1] to [5]. [9] In the case of food products that have not been heat-treated during the manufacturing process, the timing of hair contamination is determined by mixing a portion of the contaminated hair into the food for a certain period of time and preserving the contaminated hair with the degree of penetration of the fluorescent substance in the food into the contaminated hair that has been preserved. This is done by any of the methods [1] to [5] or [8].All publications, patents, and patent applications cited herein are incorporated herein by reference in their entirety.

[0012] According to the present invention, it is possible to provide a method for identifying contaminated hair in food that makes it easy to determine whether the hair was introduced during the manufacturing process or after the product was opened, and to determine when the hair was introduced.

[0013] Figure 1 is a photographic image showing the results of microscopic observation of the fluorescence emission of yellow pigment (curcuminoid) under visible light irradiation at a dominant wavelength of 436 nm for sample sections (cross-sections of hair) prepared from untreated hair (control, A), hair heat-treated in curry sauce (heat-treated sample, B), and hair heat-treated in curry sauce and then irradiated with fluorescent light (heat-treated and fluorescent light-irradiated sample, C). Figure 2 is a photographic image showing the results of microscopic observation of the fluorescence emission of yellow pigment (curcuminoid) under ultraviolet light irradiation at wavelengths of 254 nm (A) and 365 nm (B) from a handheld UV lamp, and under ultraviolet light or visible light irradiation at dominant wavelengths of 365 nm (C) and 436 nm (D) from an epifluorescence device.

[0014] The food products of the present invention include dishes served in restaurants, and various processed foods that can be distributed frozen, chilled, or at room temperature, and only need to contain the fluorescent substances detailed below.

[0015] Examples of such processed foods include, but are not limited to, retort products such as curry, stew, soup, and sauce; roux products such as curry and stew; various spice products such as wasabi paste, mustard paste, and mustard; condiment products such as mayonnaise and dressing; dairy products such as yogurt, butter, cheese, and ice cream; dessert products such as jelly and pudding; confectionery products such as chocolate and cookies; and beverage products such as tea, coffee, and fruit drinks.

[0016] In this invention, "hair" is not particularly limited and can include human hair, animal hair, etc. "Hair" in this invention also includes "hair" that has been exposed to any light (for example, fluorescent light) between the time it was discovered mixed in with food and the time it was analyzed.

[0017] This invention provides a method for determining when hair was introduced into food, i.e., whether it occurred during the product's manufacturing process or after the product was opened. This determination is made by analyzing the degree to which a fluorescent substance in the food penetrates the hair that was mixed into the food. This analysis is performed using a fluorescence analysis method.

[0018] Fluorescence analysis is a method in which a substance is irradiated with ultraviolet light or short-wavelength visible light, causing the constituent molecules or atoms of the substance to absorb energy, enter an excited state, and then release energy to return to the ground state. The fluorescence emitted at this time is measured using a fluorophotometer or the like, along with its spectrum and intensity. In this invention, the intensity and spectrum of fluorescence emitted by fluorescent substances contained in food are observed and / or measured using irradiation with ultraviolet light or visible light with a wavelength longer than 254 nm.

[0019] Examples of fluorescent substances contained in food include carotenoids, curcuminoids, pigments such as Red No. 106, and vitamins such as vitamin B2, with curcuminoids being preferred. Curcuminoids are, for example, the yellow pigment found in turmeric, an ingredient in curry. By irradiating with ultraviolet or visible light with a wavelength longer than 254 nm, the turmeric that has penetrated the hair can fluoresce in a yellowish-green color. When the fluorescent substance contained in food is curcuminoid, by irradiating with ultraviolet or visible light with a wavelength longer than 254 nm, preferably 330 nm to 450 nm, the fluorescence emission of curcuminoids that have penetrated the hair can be clearly observed from outside the hair (i.e., it is not necessary to measure the cross-section of the hair). In the "epifluorescence device," which is an irradiation device for ultraviolet or visible light used in the following examples, a filter is generally used that is designed to selectively pass light of a specific wavelength and block undesirable wavelengths in order to obtain the light used for fluorescence. For example, an excitation filter, which is an optical element, is used to extract light of the wavelength necessary for exciting a fluorescent substance from an excitation light source. Therefore, the wavelength of light emitted from the epifluorescence device (excitation light wavelength) may include wavelengths in the range of approximately 50 nm as the full width at half maximum of a specific wavelength (also called the "dominant wavelength") selected by the filter. Here, "full width at half maximum" refers to the width of wavelengths on the long-wavelength and short-wavelength sides where the filter achieves 50% of its maximum transmittance.

[0020] The above fluorescence analysis method is effective because it can be performed quickly and simply, and because it allows for a clear visual assessment of the degree of penetration of fluorescent substances into food, regardless of the cross-section of the hair. Furthermore, even when hair and food have similar color tones, such as when hair is mixed into a brownish food like curry, this analysis method allows for clear identification.

[0021] To confirm the penetration of fluorescent substances from food toward the center of the hair, or the amount of penetration of fluorescent substances from food, the cross-section of the hair can be irradiated with ultraviolet or visible light of a predetermined wavelength, and the intensity, spectrum, and distribution of fluorescence at the cross-section can be observed and / or measured.

[0022] In making the determination based on the fluorescence analysis method described above, in the case of food that has been heat-treated during the manufacturing process, for example, a portion of the hair found in the food is heat-treated under conditions equivalent to the heat treatment in the manufacturing process, and the degree of penetration of the fluorescent substance in the food into the heat-treated hair is compared with the degree of penetration of the fluorescent substance in the food into the hair that has not been heat-treated. Specifically, the hair found in the food is first cut in half using a cutter or the like. Next, one half of the cut hair is heat-treated under conditions equivalent to the sterilization conditions of the food in which it was found, for example, retort heat treatment, in the same manner as the manufacturing process. After that, the surface or cross-section of the retort-heat-treated hair and the other half of the hair that has not been retort-heat-treated are irradiated with ultraviolet or visible light of a predetermined wavelength, and the degree of penetration of the fluorescent substance in the food into each piece of hair is measured and compared.

[0023] Furthermore, in the case of food products that are not heat-treated during the manufacturing process, a portion of the hair found in the food is subjected to a preservation treatment in which the fluorescent substance in the food permeates the hair by being mixed into the food for a certain period of time. The degree of penetration of the fluorescent substance in the hair that has been preserved is compared with the degree of penetration of the fluorescent substance in the food into the hair that has been mixed in but has not been subjected to this preservation treatment. Specifically, similar to the food products that are heat-treated during the manufacturing process as described above, the hair found in the food is first cut in half using a cutter or the like. Next, one half of the cut hair is mixed into the same food product that the hair was originally mixed in for a certain period of time to allow the fluorescent substance in the food to permeate the hair. After that, the degree of penetration of the fluorescent substance in the food into the preserved hair and the surface or cross-section of the other half of the hair that has not been preserved are irradiated with ultraviolet or visible light of a predetermined wavelength, and the degree of penetration of the fluorescent substance in the food into each half of the hair is measured and compared.

[0024] Furthermore, the timing of hair contamination can be determined by methods other than comparing the degree of penetration of the fluorescent substance in the food into the two cut strands of contaminated hair described above.

[0025] Specifically, first, various data based on the relationship between the hair found in the food and the food itself, as well as the food's manufacturing conditions, are prepared in advance. For example, a foreign matter control sample is prepared beforehand by mixing hair into a specific food product and then retorting it. When hair found as a foreign object in the specific food product is obtained, the degree of penetration of the hair is measured, and the result is compared with the aforementioned foreign matter control sample. This allows for a quicker and more accurate determination of when the hair was introduced into the food, without requiring the hassle of reprocessing, such as cutting the hair in two and subjecting one half to retort heating.

[0026] Furthermore, even in foods that have not been heat-treated during the manufacturing process, by preparing hair that has been preserved for a certain period of time to allow fluorescent substances in the food to permeate it, as a foreign matter control sample, the timing of foreign matter contamination can be determined using the same method as described above.

[0027] The aforementioned comparison can be performed by visually observing the fluorescence intensity (shade) distribution, the presence or absence of fluorescent areas, etc., using a fluorescence microscope or similar device. Alternatively, the fluorescence intensity can be measured using a fluorophotometer.

[0028] The aforementioned comparison helps determine when the hair found in the food was introduced. If the treated hair and the untreated hair, or the foreign matter control sample and the hair found in the food, exhibit nearly identical fluorescence, it is highly likely that the hair was introduced during the food's manufacturing process. On the other hand, if the fluorescence intensity of the untreated hair or the hair found in the food compared to the foreign matter control sample is weak, or if there is almost no fluorescence distribution, it is determined that the hair was introduced after the product was opened.

[0029] In other words, regarding the determination of when hair was introduced into the food, if there is a large difference in the fluorescence state between the treated hair and the untreated hair or foreign matter control sample and the hair introduced into the food, it is highly likely that the hair was introduced into the food after the product was opened. Conversely, if the difference in fluorescence state is small, it is highly likely that the hair was introduced into the food during the food manufacturing process.

[0030] Furthermore, if hair found in food was introduced during the food manufacturing process, even if the aforementioned treatment is applied to the hair, no significant change is observed in the degree to which the fluorescent substance in the food penetrates the hair.

[0031] Furthermore, in fluorescence analysis methods, when measuring the degree of penetration of fluorescent substances in food, it is preferable, and more preferable, to set the measurement conditions, such as the size of the hair used for comparison and the measurement area, to be the same so as not to significantly affect the measurement results. The present invention will be described in more detail below with reference to examples.

[0032] Example 1: Fluorescence analysis of the degree of penetration of fluorescent substances into hair mixed in food.

[0033] (1) Sample Preparation Human hair was mixed into curry sauce contained in a retort pouch before retort sterilization. After sealing the retort pouch, it was subjected to retort sterilization at 121°C for 25 minutes. Next, the hair was removed from the resulting retort curry, and the curry sauce adhering to the surface was washed off with water to obtain a sample (heat-treated sample). Sample sections were prepared from the obtained sample (heat-treated sample) by the method described below. Similarly, sample sections were also prepared from a sample obtained by mixing human hair into curry sauce, subjecting it to retort sterilization, removing it, washing off the curry sauce adhering to the surface with water, and then irradiating it with fluorescent light for 400 hours (heat-treated and fluorescent light-irradiated sample, assuming the light irradiated between the time the hair was discovered in the food and the time it was analyzed). For control, untreated human hair that had not been in contact with curry sauce was used, and sample sections were prepared in the same manner.

[0034] (2) Preparation of sample sections Each sample prepared above was placed between two Sump plates (Sump plate B (Shiga Insect Supply Co.)) that had been cut in half (the tip of the sample was left outside the Sump plate to prevent the Sump solution from seeping into the interior from the cut surface of the tip of the hair foreign object), and fixed with Sump solution (Sump solution No. 1 (Shiga Insect Supply Co.)). Next, the Sump plate with the sample held in place was cut into slices perpendicular to the long axis of the sample using a microtome, and each sample section was prepared.

[0035] (3) Fluorescence Observation Each sample section prepared as described above was irradiated with visible light with a main wavelength of 436 nm (the full width at half maximum of the main wavelength includes the wavelength range of 400 to 450 nm) using an ultraviolet irradiation device (reflected fluorescence spectrometer EFD (Nikon)), and the yellow-green fluorescence emission from the yellow pigment (curcuminoid) contained in the curry ingredients was observed using a microscope (microscope OPTIPHOT (Nikon)).

[0036] (4) Results of fluorescence observation Figure 1 shows the results of fluorescence observation of each sample section. In hair that was heat-treated in curry sauce (heat-treated sample), fluorescence was observed throughout the entire interior of the hair (Figure 1B). On the other hand, in untreated human hair (control), faint fluorescence was observed on the surface of the hair (periphery of the cross-section), but no fluorescence was observed inside (Figure 1A). Furthermore, in hair that was heat-treated in retort curry and then irradiated with fluorescent light for 400 hours (heat-treated and fluorescent light irradiated sample), fluorescence was observed throughout the entire interior of the hair (Figure 1C).

[0037] These results suggest that, regarding hair found in retort curry, it is possible to determine whether the hair was introduced during the manufacturing process and subjected to heat treatment during manufacturing, based on the degree of curcuminoid penetration observed from its cross-section. Specifically, if curcuminoid penetration is confirmed into the hair, it is suggested that the hair was subjected to heat treatment during manufacturing and is highly likely to have been introduced during the manufacturing process. On the other hand, if curcuminoid penetration is not confirmed into the hair from the cross-section observation, it is suggested that the hair was not subjected to heat treatment during manufacturing and is unlikely to have been introduced during the manufacturing process. Furthermore, it has been conventionally believed that fluorescent substances in food are susceptible to the effects of light such as fluorescent lamps, and that exposure to such light attenuates fluorescence emission induced by ultraviolet or visible light irradiation. However, the results of this experiment confirm that even in samples exposed to such light, the degree of penetration into hair can be observed by fluorescence observation, demonstrating that it can be used to determine the timing of contamination without considering whether or not the sample was exposed to light.

[0038] Example 2: Fluorescence analysis of fluorescent substances in hair mixed with food at different wavelengths

[0039] (1) Sample preparation Heat-treated human hair samples were prepared in the same manner as in Example 1 above. Untreated human hair that had not been in contact with curry sauce was used as a control. Each sample was subjected to the following fluorescence observation without the preparation of sample sections.

[0040] (2) Fluorescence Observation The heat-treated samples prepared as described above were irradiated with ultraviolet light or visible light at wavelengths of 254 nm, 365 nm, or the main wavelength of 365 nm (with the full width at half maximum of the main wavelength including the range of 330 to 380 nm), and 436 nm (with the full width at half maximum of the main wavelength including the range of 400 to 450 nm), respectively, using an ultraviolet irradiation device (handheld UV lamp UVG-54 (UVP Corporation) or epifluorescence device EFD (Nikon)), and observed under a microscope or the like for the yellow-green fluorescence emission from the yellow pigment (curcuminoid) contained in the curry ingredients.

[0041] (3) Results of fluorescence observation Figure 2 shows the results of fluorescence observation for each sample. In the hair that was heat-treated in retort curry (heat-treated sample), fluorescence was observed throughout the entire interior of the hair, but fluorescence was observed more clearly under irradiation with ultraviolet light at a wavelength of 365 nm (Figure 2B) than under irradiation with ultraviolet light at a wavelength of 254 nm (Figure 2A), and further under irradiation with visible light at a dominant wavelength of 436 nm (Figure 2D) than under irradiation with a dominant wavelength of 365 nm (Figure 2C).

[0042] These results demonstrate that, regarding hair found in retort curry, the fluorescence emission of curcuminoids that have penetrated deep into the hair can be observed without sectioning the sample by irradiating it with ultraviolet or visible light with wavelengths longer than 254 nm (e.g., 330-450 nm), and this can be used to determine when the hair was introduced.

Claims

1. A method for identifying contaminated hair, which involves analyzing the degree of penetration of a fluorescent substance in food into hair that was mixed into food using a fluorescence analysis method that utilizes irradiation with ultraviolet or visible light with a wavelength longer than 254 nm, and determining the time when the hair was mixed in based on the analysis results of the degree of penetration.

2. The method according to claim 1, wherein the fluorescent substance is a curcuminoid.

3. The method according to claim 1, wherein the hair is hair that has been exposed to light between the time it was discovered mixed in with food and the time it was analyzed.

4. The method according to claim 1, wherein the fluorescence analysis method utilizes irradiation with ultraviolet or visible light with a wavelength of 330 nm to 450 nm.

5. The method according to claim 1, wherein the degree of penetration of a fluorescent substance in food into hair is analyzed based on a cross-section of the hair.

6. The method according to claim 1, wherein, in the case of food that has been heat-treated during the manufacturing process, the timing of hair contamination is determined by comparing the degree of penetration of the fluorescent substance in the food into the contaminated hair with the degree of penetration of the fluorescent substance in the food into hair that has been heat-treated under conditions equivalent to the said heat treatment.

7. The method according to claim 1, wherein, in the case of food that has been heat-treated during the manufacturing process, the timing of hair contamination is determined by heat-treating a portion of the contaminated hair under conditions equivalent to the heat-treating process, and comparing the degree of penetration of the fluorescent substance in the food into the heat-treated contaminated hair with the degree of penetration of the fluorescent substance in the food into the unheat-treated contaminated hair.

8. The method according to claim 1, wherein, in the case of food that has not been heat-treated during the manufacturing process, the timing of hair contamination is determined by comparing the degree of penetration of the fluorescent substance in the food into the contaminated hair with the degree of penetration of the fluorescent substance in hair that has been preserved by being mixed into the food for a certain period of time to allow the fluorescent substance in the food to penetrate.

9. The method according to claim 1, wherein, in the case of food that has not been heat-treated during the manufacturing process, the timing of hair contamination is determined by preserving a portion of the contaminated hair by mixing it into the food for a certain period of time to allow the fluorescent substance in the food to permeate into the contaminated hair, and then comparing the degree of penetration of the fluorescent substance in the food into the contaminated hair that has undergone the preservation treatment with the degree of penetration of the fluorescent substance in the food into the contaminated hair that has not undergone the preservation treatment.

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