Method of identifying foreign matter contaminating food by elemental concentration analysis using epma

Abstract

To provide a method of identifying foreign matter contaminating a food product, which enables easy determination of when contamination occurred, meaning whether the foreign matter contaminating the food product was mixed into the product during manufacture or after the product was opened.SOLUTION: An contaminating hair identification method is provided, comprising analyzing the degree of penetration of a trace element in food into foreign matter contaminating the food by an elemental concentration analysis method using an electron probe micro analyzer (EPMA) including given conditions, and determining when the foreign matter was mixed into the food based on a result of the penetration degree analysis.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a method for determining whether a foreign matter that has been mixed into food was mixed in during the manufacturing process or after the product was opened, i.e., the time of mixing in of the foreign matter, based on the results of the analysis of the degree of penetration by analyzing the degree of penetration of trace elements in the food into the foreign matter using an element concentration analysis method using an electron probe micro analyzer (EPMA). [Background technology]

[0002] Food is something that is taken into the body, and so naturally, its safety must be ensured. For this reason, in the quality control of food production, any matter that may cause the inclusion of foreign matter, such as hair, must be thoroughly eliminated. In order to thoroughly implement such quality control, it is necessary to accurately grasp the actual state of foreign matter contamination, and for this purpose, it is important to first verify when the foreign matter that was found in the food was introduced, whether it was introduced during the manufacturing process or after the product was opened.

[0003] For example, in relation to the verification of hair, a method for determining the time of contamination based on the effect of heating during the manufacturing process is being studied. Non-Patent Document 1 describes a study into whether or not the above-mentioned determination is possible based on morphological changes, since hair is made of keratin protein and undergoes morphological changes upon heat treatment. Specifically, it describes that heating at 200 to 300 degrees is required for morphological changes to remain due to heat treatment, and since most hairs do not undergo morphological changes with heat treatment at around 100 degrees during food manufacturing, it is difficult to estimate the time of hair contamination based on changes during heat treatment from morphological examination.

[0004] In addition, Non-Patent Document 1 discloses that when hair is heated, the components inside the hair are changed, and catalase in biological tissue disappears during heating, so that the presence or absence of heating can be determined by the change in activity, and that if there is a hair root, there will be cells that exhibit enzyme activity, and catalase activity can be measured. However, in reality, many of the hairs that are contaminating foreign bodies do not have hair roots, and catalase activity itself changes under various conditions, so it is dangerous to comment on the presence or absence of heating.

[0005] Patent Document 1 also describes a method for identifying contaminated foreign matter, which identifies the time of contamination based on the results of an analysis of the degree of penetration of food components into foreign matter that has been contaminated in food, and describes that the analysis of the degree of penetration of food components into foreign matter is performed by an elemental concentration analysis method. Patent Document 1 also describes that the elemental concentration analysis method can be performed using an Electron Probe Micro Analyzer (EPMA) device, which irradiates an electron beam onto the surface of an object and detects characteristic X-rays and the like generated therefrom, and that elements can be identified by the characteristic X-rays, and that, for example, the concentration distribution of sodium chloride (sodium and chlorine) in the food can be measured using the elemental analysis device EPMA for a cross section of a hair that has been contaminated in food, and the time of contamination of the hair can be determined from the state of penetration of sodium chloride into the hair. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2005-83804 A [Non-patent literature]

[0007] [Non-Patent Document 1] "Method of Identifying Contaminated Hair" by Gen Sato, published by Science Forum Co., Ltd., November 7, 2000 (pp. 7-8, 88-91, 107-108) DISCLOSURE OF THEINVENTION [Problem to be solved by the invention]

[0008] In the method of Patent Document 1, the penetration degree of sodium chloride contained in food into the inside of hair is analyzed by an element concentration analysis method using EPMA, but some foods contain little or no sodium chloride, and the penetration degree of sodium chloride cannot be detected or measured for hair that has been mixed into such foods, and it may be difficult to determine the time of mixing. Also, since foods contain relatively large amounts of sodium chloride, such as table salt, the penetration degree of sodium chloride into the inside of mixed hair can be easily detected and measured by an element concentration analysis method using EPMA, but for elements that exist in trace amounts in food, the same analysis method as for elements that exist in large amounts, such as sodium chloride, cannot detect or measure the penetration degree of the trace element into the inside of mixed hair, and it may be difficult to determine the time of mixing.

[0009] Therefore, the objective of this field is to provide a method for identifying foreign matter that has been mixed into food, which can detect and measure the degree of penetration of trace elements into foreign matter in food, and can determine the time of mixing, whether the foreign matter was mixed in during the manufacturing process or after the product was opened. [Means for solving the problem]

[0010] As a result of intensive research into solving the above-mentioned problems, the inventors have discovered that by subjecting the degree of penetration of trace elements in food into foreign matter mixed into food to an elemental concentration analysis method using an EPMA having specified conditions of accelerating voltage, probe current and measurement time, it is possible to detect and measure the degree of penetration of trace elements in food into foreign matter, and based on the analysis results of the degree of penetration, it is possible to determine whether the foreign matter was mixed in during the manufacturing process or after the product was opened.

[0011] The present invention is based on these new findings and includes the following inventions. [1] A method for identifying contaminants in food, which involves analyzing the degree of penetration of trace elements in food into contaminants that have been mixed into the food by an elemental concentration analysis method using an electron probe micro analyzer (EPMA), and determining the time when the contaminants were mixed in based on the results of the analysis of the degree of penetration, wherein the analytical conditions for the EPMA include the following conditions: Acceleration voltage: 5kV~25kV Irradiation current: 30nA~200nA Measurement time per pixel: 20mSec~60mSec. [2] The method of [1], wherein the trace elements are elements present in amounts of 500 mg or less, 400 mg or less, 300 mg or less, 200 mg or less, or 100 mg or less per 100 g of food. [3] The method of [1] or [2], wherein the trace element is potassium, phosphorus, sodium, or chloride. [4] Any of the methods [1] to [3], in which the EPMA analysis conditions include the following: Acceleration voltage: 15 kV Irradiation current: 30nA~100nA Measurement time per pixel: 20mSec~40mSec. [5] Any of the methods [1] to [4] in which the degree of penetration of trace elements in food into a foreign object is analyzed based on the cross-section of the foreign object. [6] A method according to any of [1] to [5], in which the time when the foreign matter was mixed in is determined in the case of foods that have not been heat-treated during the manufacturing process, by comparing the degree of penetration of trace elements in the food into the contaminated foreign matter with the degree of penetration of the trace elements in the foreign matter that has been mixed into the food for a certain period of time and subjected to a preservation process to allow the trace elements in the food to penetrate. [7] Any of the methods [1] to [6], in the case of foods that have not been heat-treated during the manufacturing process, the time when the foreign matter was mixed in is determined by mixing a portion of the foreign matter into the food for a certain period of time and subjecting the food to a preservation treatment that allows trace elements in the food to penetrate into the foreign matter, and then comparing the degree of penetration of the trace elements in the food into the foreign matter that has been subjected to the preservation treatment with the degree of penetration of the trace elements in the food into the foreign matter that has not been subjected to the preservation treatment. [8] The method according to [6] or [7], wherein the food is selected from the group consisting of tofu, soy milk, milk and dairy products, Chinese noodles, soba, udon, hiyamugi, somen and other noodles, cut vegetables, salads and foods and beverages containing one or more of them. [9] A method comprising any of the methods [1] to [5] in which the time when a foreign object was introduced into a food that has been heat-treated during the manufacturing process is determined by comparing the degree of penetration of trace elements in the food into the foreign object with the degree of penetration of trace elements in the food into foreign object that has been heat-treated under conditions equivalent to those of the heat treatment.

[10] In the case of foods that have been heat-treated during the manufacturing process, the time when the foreign matter was introduced is determined by heat-treating a portion of the foreign matter under conditions equivalent to those of the heat treatment, and comparing the degree of penetration of trace elements in the food into the heat-treated foreign matter with the degree of penetration of trace elements in the food into the non-heat-treated foreign matter, using any of the methods [1] to [5] or [9].

[11] Any of methods [1] to

[10] , wherein the foreign object is a hair, an insect, or a part thereof. Effect of the Invention

[0012] According to the present invention, it is possible to detect and measure the degree of penetration of trace elements into foreign matter in food, and to provide a method for identifying foreign matter that has been mixed into food, which can determine whether the foreign matter was mixed in during the manufacturing process or after the product was opened, and the time of mixing. [Brief description of the drawings]

[0013] [Figure 1]FIG. 1 is a photograph showing the results of analysis by element mapping method using an elemental analyzer EPMA (apparatus name: JXA-isp100, JEOL Ltd.) under the analytical conditions of <Example> or <Comparative Example>, of the phosphorus concentration distribution in the cross section of untreated hair (control) and hair mixed into yogurt (before fermentation) and stored for a specified period of time. [Diagram 2] FIG. 2 is a photograph showing the results of analysis by element mapping method using an elemental analyzer EPMA (apparatus name: JXA-isp100, JEOL Ltd.) under the analytical conditions of <Example> or <Comparative Example>, of the potassium concentration distribution in the cross section of untreated hair (control) and hair mixed into yogurt (before fermentation) and stored for a specified period of time. [Diagram 3] FIG. 3 is a photograph showing the results of elemental mapping analysis of potassium concentration distribution in cross sections of a control (Blank), a hair that had been in contact with tofu for a specified time (model of contamination after opening of product), and a hair that had been mixed into a mixture of soy milk and nigari during the manufacturing process and then mixed into tofu (model of contamination during product manufacturing) using an elemental analyzer EPMA (apparatus name: JXA-isp100, JEOL Ltd.) under the analysis conditions of <Example>. [Figure 4] FIG. 4 is a photograph showing the results of elemental mapping analysis of potassium concentration distribution in cross sections of a control (Blank), hair that had been in contact with tofu for a specified time (model of contamination after opening the product), and hair that had been mixed into a container containing tofu and enclosed water and stored for a specified period (model of contamination during product manufacturing) using an elemental analyzer EPMA (apparatus name: JXA-isp100, JEOL Ltd.) under the analysis conditions of <Examples>. [Diagram 5] FIG. 5 is a photograph showing the results of analysis of the sodium and chlorine concentration distribution in the cross section of a hair by an element mapping method using an elemental analyzer EPMA (apparatus name: JXA-isp100, JEOL Ltd.) under the analysis conditions of <Examples>, in which 0.1% by mass salt solution was prepared, mixed therein, and either (i) heated at 120°C for a predetermined period of time and then left to stand in an environment of about 20°C, or (ii) left to stand in an environment of about 20°C. [Figure 6] FIG. 6 is a photograph showing the results of elemental mapping analysis of the sodium concentration distribution in the cross sections of untreated hair (control), hair that had been in contact with Chinese noodles for a specified time (model of contamination after opening of product), and hair that had been mixed into a container so as to come into contact with Chinese noodles and stored for a specified period of time (model of contamination during product manufacturing) using an elemental analyzer EPMA (apparatus name: JXA-isp100, JEOL Ltd.) under analysis condition A. [Figure 7] Figure 7 is a photograph showing the results of an elemental mapping analysis using an EPMA elemental analyzer (apparatus name: JXA-isp100, JEOL Ltd.) under analysis condition B to determine the sodium concentration distribution in cross sections of the abdomen of an untreated chironomid (control), a chironomid that had been in contact with Chinese noodles for a specified period of time (model of contamination after product opening), and a chironomid that had been mixed into a container so that it was in contact with Chinese noodles and stored for a specified period of time (model of contamination during product manufacturing). [Figure 8] FIG. 8 is a photograph showing the results of analysis by elemental mapping method using an elemental analyzer EPMA (apparatus name: JXA-isp100, JEOL Ltd.) under analysis condition C to determine the phosphorus concentration distribution in the cross sections of untreated hair (control), hair that had been in contact with buckwheat noodles for a specified period of time (model of contamination after opening of product), and hair that had been mixed into a container so that it came into contact with buckwheat noodles and stored for a specified period of time (model of contamination during product manufacturing). [Figure 9] Figure 9 is a photograph showing the results of an elemental mapping analysis of the chlorine concentration distribution in the cross sections of an untreated Smoky Brown cockroach leg (control), a Smoky Brown cockroach leg that had been in contact with shredded radish in a commercially available radish salad for a specified period of time (model of contamination after opening the product), and a Smoky Brown cockroach leg that had been immersed in electrolyzed water used in the manufacturing process and then mixed into a bag so that it was in contact with shredded radish in a commercially available radish salad and stored for a specified period of time (model of contamination during product manufacturing) using an elemental analyzer EPMA (device name: JXA-isp100, JEOL Ltd.) under analysis condition D. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] The food of the present invention includes dishes served in restaurants and the like, and various processed foods that can be distributed frozen, chilled, at room temperature, etc.

[0015] Examples of such processed foods include 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; seasoning products such as mayonnaise and dressing; dairy products such as yogurt, butter, cheese, and ice cream; dessert products such as tofu, jelly, and pudding; confectionery products such as chocolate and cookies; noodles such as Chinese noodles, soba, udon, hiyamugi, and somen; cut vegetables, salads, and beverage products such as tea, soy milk, coffee, and fruit drinks, but are not limited thereto. Preferably, the food of the present invention is a food that does not contain a large amount of the element selected as the measurement target in the element concentration analysis method of the present invention. Here, "a large amount" regarding the amount of the element selected as the measurement target contained in the food means that the element selected as the measurement target is contained in an amount of more than 500 mg in 100 g of the food. The amount of each element contained in 100 g of the food can be determined by referring to, for example, the Standard Tables of Food Composition in Japan (Ministry of Education, Culture, Sports, Science and Technology). For example, preferred foods in the present invention include tofu (cotton tofu, silken tofu, soft tofu, packed tofu, baked tofu, raw tofu, fried tofu, etc.), soy milks (soy milk, prepared soy milk, soy milk beverages), milk (raw milk, cow's milk, special cow's milk, raw goat's milk, pasteurized goat's milk, raw sheep's milk, raw buffalo milk, ingredient-adjusted milk, low-fat milk, non-fat milk, and processed milk), and dairy products (cream, butter, butter oil, cheese, concentrated whey, ice cream, concentrated milk, skim concentrated milk, condensed milk, sweetened skim condensed milk, prepared liquid milk, fermented milk (yogurt, etc.), lactic acid bacteria beverages, and milk beverages), noodles (Chinese noodles, soba, udon, hiyamugi, somen, etc.), cut vegetables, salads, and foods and beverages containing one or more of these. Examples of foods and beverages containing soy milk include soy milk yogurt, and examples of foods and beverages containing milk or dairy products include processed milk or dairy products (e.g., foods made by combining milk or dairy products with other ingredients (vegetable oils and fats, defatted soy flour, etc.)), but are not limited to these.

[0016] In the present invention, "foreign matter" refers to any substance that may be mixed into the above-mentioned food, but it refers to substances that trace elements in food ingredients can penetrate, and substances that trace elements in food ingredients, such as metals, that cannot be penetrated by are not included in the "foreign matter" of the present invention. Examples of "foreign matter" in the present invention include, but are not limited to, hair, nails, paper, cotton products (thread, cloth), wood chips, stems, stems, and roots of plant materials, bone fragments of animal materials, thread, rope, string, insects, plastics and rubber, etc., as well as parts of these. In the present invention, the "hair" is not particularly limited, and examples thereof include human hair, animal hair, and the like. Preferably, in the present invention, a "foreign object" is a hair, an insect, or a part thereof.

[0017] The present invention is a method for determining when a foreign object was mixed into a food, i.e., whether it was during the manufacturing process of the product or after the product was opened, and this is analyzed based on the degree of penetration of trace elements in the food into the foreign object that was mixed into the food. This analysis is performed by an element concentration analysis method using an electron probe micro analyzer (EPMA). EPMA irradiates a finely focused electron beam in a vacuum using an accelerating voltage and a projection current onto a minute section (pixel) on the surface of a solid sample that has been polished to a mirror finish, detects characteristic X-rays emitted from the sample, and can determine the type and concentration of elements contained therein. In addition, it is possible to analyze multiple pixels contained within a certain area for a specified measurement time, and display the magnitude of the element concentration determined for each pixel in a different color, and visually display the concentration distribution of elements in two dimensions (element mapping method).

[0018] In order to confirm the penetration status of trace elements in food progressing toward the center of the foreign object, or the amount of trace elements penetrated in food, it is preferable to irradiate the cross-section of the foreign object with an electron beam and measure the degree of penetration / concentration distribution of the trace elements on the cross-section.

[0019] In the present invention, the analysis conditions for EPMA include the following conditions: Acceleration voltage: 5kV~25kV Irradiation current: 30nA~200nA Measurement time per pixel: 20mSec~60mSec.

[0020] The acceleration voltage can be selected from the range of 5 kV to 25 kV, preferably 10 kV to 20 kV, and is more preferably 15 kV.

[0021] The irradiation current can be selected from the range of 30 nA to 200 nA, preferably 30 nA to 150 nA, and more preferably 30 nA to 100 nA.

[0022] The measurement time per pixel can be selected from the range of 20 mSec to 60 mSec, preferably 20 mSec to 50 mSec, for example, 30 mSec to 50 mSec, and is more preferably 20 mSec to 40 mSec.

[0023] In the present invention, it is preferable to set the accelerating voltage, irradiation current, and measurement time per pixel of the EPMA within the above ranges, since this makes it possible to satisfactorily detect and measure the concentration distribution of trace elements in food that have permeated into foreign matter.

[0024] Particularly preferably, in the present invention, EPMA is carried out under analytical conditions including the following conditions: Acceleration voltage: 15 kV Irradiation current: 30nA~100nA Measurement time per pixel: 20mSec~40mSec.

[0025] In the present invention, the EPMA analysis may use a polycrystalline addition program. According to the polycrystalline addition program, simultaneous measurement and data processing are performed using multiple spectroscopes in the analysis, data measured by the multiple spectroscopes are added, and the added data is converted into concentration by a calibration curve method, which is preferable because it can provide a high S / N (signal / noise ratio), i.e., a clearer measurement result.

[0026] In the present invention, "trace elements in food" refers to elements contained in 100 g of food containing foreign matter in an amount of 500 mg or less, 400 mg or less, 300 mg or less, 200 mg or less, or 100 mg or less, for example, 0.5 mg to 500 mg, 1 mg to 500 mg, 3 mg to 500 mg, 5 mg to 500 mg, 10 mg to 500 mg, 50 mg to 500 mg, 60 mg to 500 mg, 70 mg to 500 mg, 80 mg to 500 mg, or 90 mg to 500 mg, preferably 100 mg to 400 mg, more preferably 100 mg to 300 mg, and even more preferably 100 mg to 200 mg, and it is preferable that the trace elements to be measured are elements that are not contained in the foreign matter or that are contained in extremely small amounts in the foreign matter. The trace elements to be measured may vary depending on the food, but examples include sodium, chlorine, potassium, phosphorus, magnesium, calcium, zinc, iron, etc. The amount of trace elements in food can be determined by referring to, for example, the Standard Tables of Food Composition in Japan (Ministry of Education, Culture, Sports, Science and Technology) for the amount of each element contained in 100 g of food. The trace elements to be measured originate from various food components contained in food, and the penetration of the various food components into foreign matter is affected by the food's heat sterilization temperature and time, cooking heating temperature and time, storage period and temperature, pH, acidity, degree of decomposition of the food components, and the molecular size of the food components, but the present invention can be applied as long as the content in the food of the element to be measured that constitutes the food component is within the above-mentioned range.

[0027] In the case of a food product that has been heat-treated during the manufacturing process, for example, a part of the foreign matter mixed in the food product is heat-treated under the same conditions as the heat treatment, and the degree of penetration of the trace elements in the food product into the heat-treated foreign matter is compared with the degree of penetration of the trace elements in the food product into the foreign matter that has not been heat-treated. Specifically, the foreign matter mixed in the food product is first cut into almost half using a cutter or the like. Next, one of the cut foreign matter products is subjected to a heat treatment under the same conditions as the sterilization conditions of the food product, for example, a retort heat treatment. Then, the cross sections of the foreign matter that has been retort heat-treated and the other foreign matter that has not been retort heat-treated are irradiated with an electron beam, and the degree of penetration of the trace elements in the food product into each foreign matter is measured and compared.

[0028] In addition, for foods that have not been heat-treated during the manufacturing process, the degree of penetration of trace elements in foreign matter that has been mixed into the food and subjected to a preservation treatment in which a part of the foreign matter that has been mixed into the food is mixed into the food for a certain period of time to allow the trace elements in the food to penetrate is compared with the degree of penetration of trace elements in the food into the foreign matter that has not been subjected to the preservation treatment. Specifically, as with the food that is heat-treated during the manufacturing process described above, the foreign matter that has been mixed into the food is first cut into approximately half using a cutter or the like. Next, one of the foreign matter that has been cut is mixed again into a food similar to the food that the foreign matter was mixed into for a certain period of time to allow the trace elements in the food to penetrate into the mixed foreign matter, and a preservation treatment is performed. After that, the degree of penetration of the trace elements in the food into the mixed foreign matter that has been subjected to the preservation treatment and the cross section of the other foreign matter that has not been subjected to the preservation treatment are irradiated with an electron beam, and the degree of penetration of the trace elements in the food into each foreign matter is measured and compared.

[0029] In addition, the time of contamination by the foreign object can also be determined by other comparison methods than the above-mentioned comparison of the degree of penetration of trace elements in food in the two cut pieces of contaminant.

[0030] Specifically, first, various data based on the relationship between the foreign matter mixed in the food and the food, the manufacturing conditions of the food, etc. are prepared in advance. For example, the same type of object as the foreign matter is prepared in advance, and a foreign matter control product is prepared in advance by mixing it with a specific food and subjecting it to retort heating. When the foreign matter mixed in the specific food is obtained as a foreign matter, the foreign matter is cut into two pieces as described above, and the penetration degree of the trace elements in the food in the foreign matter is measured as it is without subjecting one of the pieces to reprocessing such as retort heating, and the result is compared with the foreign matter control product. This makes it possible to more quickly and accurately determine the time of mixing in the foreign matter mixed in the food without the trouble of the reprocessing.

[0031] In addition, even in foods that have not been heat-treated during the manufacturing process, the time when the foreign object was mixed in can be determined using a method similar to that described above by preparing in advance as a foreign object control item the same type of foreign object that has been mixed in for a certain period of time and subjected to a preservation treatment to allow the trace elements in the food to penetrate.

[0032] The above-mentioned comparison may be performed by visually observing the element concentration distribution, the presence or absence of elemental parts, etc., with the naked eye or a fluorescent microscope, etc., using an element mapping method using a normal computer, etc. According to the element mapping method, increasing concentrations of elements are displayed in the order of purple, blue, green, yellow, red, and white, and the degree of penetration can be clearly grasped.

[0033] Such a comparison can also be performed by measuring the amount of a specific element detected in an EPMA chart.

[0034] The comparison is used to determine the time of contamination of the foreign matter in the food, and if the elemental concentrations of the treated foreign matter and the foreign matter not treated, or of the foreign matter control product and the foreign matter in the food, are approximately the same, it is determined that there is a high possibility that the foreign matter that was in the food was introduced during the food manufacturing process.On the other hand, if the elemental concentrations of the foreign matter not treated or the foreign matter in the food compared to the foreign matter control product are low, or there is almost no elemental concentration distribution, it is determined that the foreign matter that was in the food was introduced after the product was opened.

[0035] In other words, when it comes to determining when a foreign matter was mixed into food, if there is a large difference in elemental concentration distribution between the foreign matter that has been treated and the untreated foreign matter that has not been treated, or between the foreign matter control product and the foreign matter that was mixed into the food, then it is highly likely that the foreign matter that was mixed into the food after the product was opened, and if the difference in elemental concentration distribution is small, then it can be determined that there is a high possibility that the foreign matter that was mixed into the food was mixed in during the food manufacturing process.

[0036] Furthermore, if the foreign matter that was mixed into the food was introduced during the food manufacturing process, even if the foreign matter is subjected to the above-mentioned treatment, there will be no significant change in the degree to which trace elements in the food penetrate the foreign matter.

[0037] In addition, when measuring the degree of penetration of trace elements in food in elemental concentration analysis methods using EPMA, it is important to set the measurement conditions, such as the size of the foreign object being compared and the part being measured, to be the same so as not to significantly affect the measurement results. The present invention will now be described in more detail with reference to examples. EXAMPLES

[0038] Example 1: Element concentration analysis using EPMA to examine the penetration of trace elements in hair contaminated with yogurt (1) Sample preparation A commercially available Caspian Sea yogurt starter culture was mixed with milk in a hot water sterilized container with a lid to produce yogurt (before fermentation), which was then mixed with human hair and stored in a refrigerator (10°C or less) with the lid on for 1, 3, 7, 14, or 24 days. After the specified period had passed, the hair was removed from the yogurt obtained, and the yogurt adhering to the surface was wiped off to obtain a sample. From this sample, a sample for element concentration analysis of the cross section of the sample was prepared using the method described below. As a control, untreated human hair (i.e., not exposed to yogurt) was used, and samples for elemental concentration analysis were prepared in the same manner.

[0039] (2) Preparation of samples for elemental concentration analysis of cross-sections Each sample prepared above was immersed in photopolymerization resin, and the resin was hardened with an ultraviolet ray irradiation device to produce a composite resin in which the sample was encapsulated and hardened. Next, the cross section of the sample was polished using a cutter knife, sandpaper, etc. Next, gold was evaporated using a gold evaporation device to prepare samples for element concentration analysis of each sample cross section.

[0040] (3) Measurement of element concentration distribution The sample for each element concentration analysis prepared above was fixed on a sample stage for an elemental analyzer so that the cross section of the sample was facing upward. Next, the concentration distribution of phosphorus and potassium was measured for the cross section of each element concentration analysis sample using an elemental analyzer EPMA (device name: JXA-isp100, JEOL Ltd.) under the following analysis conditions.

[0041] Analysis conditions: <Example> Acceleration voltage: 15 kV Irradiation current: 100nA Measurement time per pixel: 40mSec

[0042] <Comparative Example> Acceleration voltage: 15 kV Irradiation current: 30nA Measurement time per pixel: 20mSec

[0043] (4) Measurement results of element concentration distribution The concentration distribution of phosphorus and potassium in the cross section of each sample was analyzed by an element mapping method as shown in Figs. 1 and 2 to measure the concentration distribution of each element in the cross section.

[0044] Figure 1 shows the measurement results of phosphorus concentration distribution in the cross section of each sample, and when analyzed under the conditions of <Example>, the presence of phosphorus was confirmed throughout the inside of the hair stored in yogurt for a certain period of time. In addition, when comparing the hair stored for one day with the hair stored for three days, it was confirmed that more phosphorus was present inside the hair stored for three days.

[0045] Furthermore, when comparing hair stored for 3 days with hair stored for 7, 14, or 24 days, no significant differences were found in the amount of phosphorus inside the hair.

[0046] Very little phosphorus was detected in untreated (i.e., not exposed to yogurt) hair.

[0047] Furthermore, when analyzed under the conditions of <Comparative Example>, the presence of phosphorus was hardly confirmed in the cross-sections of any of the samples. It has been confirmed that the conditions of <Comparative Example> give good results when measuring the concentration distribution of elements that are present in amounts of approximately 500 mg or more in 100 g of food (data not shown). However, since phosphorus is a trace element contained in yogurt in an amount of approximately 100 mg / 100 g (Standard Tables of Food Composition in Japan 2020 Edition (8th Edition), Ministry of Education, Culture, Sports, Science and Technology), it was confirmed that under the conditions of the <Comparative Example>, it is difficult to detect phosphorus that has penetrated from yogurt into the inside of the contaminated hair.

[0048] FIG. 2 shows the measurement results of potassium concentration distribution in the cross section of each sample. When analyzed under the conditions of the <Example>, the presence of potassium was confirmed inside the hair stored in yogurt for a specified period of time.

[0049] It was also confirmed that the longer the storage period, the greater the amount of potassium present inside the hair.

[0050] Very little potassium was detected inside untreated (i.e., hair that had not been mixed into yogurt) hair.

[0051] Furthermore, when analyzed under the conditions of the <Comparative Example>, the presence of potassium was hardly confirmed in the cross sections of any of the samples. Since potassium is a trace element contained in yogurt in an amount of approximately 170 mg / 100 g (Standard Tables of Food Composition in Japan 2020 Edition (8th Edition), Ministry of Education, Culture, Sports, Science and Technology), it was confirmed that under the conditions of the <Comparative Example>, it is difficult to detect potassium that has penetrated from yogurt into the inside of the contaminated hair.

[0052] From these results, it is possible to determine the period during which a hair found in yogurt was contaminated, depending on the degree of penetration or concentration distribution of phosphorus and potassium inside the hair, and it is also possible to determine whether the hair was contaminated during the manufacturing process; that is, if penetration of phosphorus and potassium into the hair is confirmed and / or the presence of a large amount of phosphorus and potassium inside the hair, it is suggested that the period during which the hair was contaminated is long and that it is highly likely that the hair was contaminated during the manufacturing process. On the other hand, if penetration of phosphorus and potassium into the hair is not confirmed and / or the presence of a large amount of phosphorus and potassium inside the hair is not confirmed, it is suggested that the period during which the hair was contaminated is short and that it is unlikely that the hair was contaminated during the manufacturing process.

[0053] Example 2: Element concentration analysis using EPMA to examine the penetration degree of trace elements in hair contaminated with tofu (1) Sample preparation Assuming contamination during manufacturing, human hair was mixed into a mixture of soy milk and nigari, heated in a microwave oven to make homemade tofu, and stored in a refrigerator (below 10°C) for 7 days. In addition, to simulate contamination after the product was opened, human hair was placed in contact with commercially available tofu and left to stand at room temperature for 20 minutes. After a specified period of time had passed, the hair was removed from the tofu, and the tofu and / or water adhering to the surface was wiped off to obtain a sample. From the obtained sample, a sample for elemental concentration analysis of the cross section of the sample was prepared using the method described in Example 1(2) above. As a control, human hair was not included, and samples for elemental concentration analysis were prepared similarly.

[0054] (2) Measurement of element concentration distribution Using the samples for element concentration analysis prepared above, the potassium concentration distribution in the cross section of the sample was measured according to the method described in Example 1(3) above and under the analytical conditions of the <Example>.

[0055] (3) Measurement results of element concentration distribution The potassium concentration distribution in the cross section of each sample was analyzed by an element mapping method as shown in FIG. 3 to measure the potassium concentration distribution in the cross section.

[0056] Figure 3 shows the measurement results of potassium concentration distribution in the cross section of each sample, and when analyzed under the conditions of <Example>, the presence of potassium was confirmed inside the hair mixed with tofu. In addition, when comparing the case where the hair was in contact with tofu for 20 minutes (model of mixing after opening the product) with the case where the hair was mixed with a mixture of soy milk and bittern (model of mixing during product manufacturing), the presence of potassium was confirmed throughout the hair, including inside the hair, and a larger amount of potassium was confirmed to be present in the model of mixing during product manufacturing.

[0057] Potassium is a trace element contained in tofu in amounts of approximately 110 mg to 150 mg per 100 g (Standard Tables of Food Composition in Japan 2020 Edition (8th Edition), Ministry of Education, Culture, Sports, Science and Technology). It was confirmed that under the conditions of the above <Example>, potassium that had penetrated from the tofu into the inside of the contaminated hair could be detected.

[0058] These results suggest that for a hair found in tofu, it is possible to determine the period during which the hair was present depending on the degree of potassium penetration or concentration distribution inside the hair, and it is also possible to determine whether the hair was present during the manufacturing process; that is, if potassium penetration into the hair is confirmed and / or if a large amount of potassium is confirmed inside the hair, it is highly likely that the hair was present for a long time and that it was present during the manufacturing process (the tofu manufacturing stage). On the other hand, if potassium penetration into the hair is not confirmed and / or if a large amount of potassium is not confirmed inside the hair, it is highly likely that the hair was present for a short time and that it was not present during the manufacturing process.

[0059] Example 3: Element concentration analysis using EPMA on the penetration degree of trace elements in hair contaminated with tofu (enclosed water) (1) Sample preparation Assuming contamination during manufacturing, human hair was mixed into a commercially available container containing tofu and sealed water, and the container was stored in a refrigerator (4°C) for one or seven days. In addition, to simulate contamination after the product was opened, human hair was placed in contact with commercially available tofu and left to stand at room temperature for 20 minutes. After a specified period of time had passed, the hair was removed from the tofu, and the tofu and / or water adhering to the surface was wiped off to obtain a sample. From the obtained sample, a sample for elemental concentration analysis of the cross section of the sample was prepared using the method described in Example 1(2) above. As a control, human hair was not included, and samples for elemental concentration analysis were prepared similarly.

[0060] (2) Measurement of element concentration distribution Using the samples for element concentration analysis prepared above, the potassium concentration distribution in the cross section of the sample was measured according to the method described in Example 1(3) above and under the analytical conditions of the <Example>.

[0061] (3) Measurement results of element concentration distribution The potassium concentration distribution in the cross section of each sample was analyzed by an element mapping method to measure the potassium concentration distribution in the cross section, as shown in FIG.

[0062] Figure 4 shows the measurement results of potassium concentration distribution in the cross section of each sample. Comparing the case where the sample was in contact with tofu for 20 minutes (product-opening contamination model) with the case where a human hair was mixed into a container containing tofu and enclosed water (product-manufacturing contamination model), in the product-manufacturing contamination model, potassium was confirmed to be present throughout the hair, even inside the hair, and a greater amount of potassium was confirmed to be present. It was also confirmed that the longer the contamination period, the greater the amount of potassium present inside the hair.

[0063] These results suggest that for a hair found in a container containing tofu and sealed water, it is possible to determine the period during which the hair has been mixed in, depending on the degree of potassium penetration or concentration distribution inside the hair, and it is also possible to determine whether the hair was mixed in during the manufacturing process; that is, if potassium penetration into the hair is confirmed and / or if a large amount of potassium is confirmed inside the hair, it is highly likely that the hair has been mixed in for a long time and that it was mixed in during the manufacturing process (before the container was sealed). On the other hand, if potassium penetration into the hair is not confirmed and / or if a large amount of potassium is not confirmed inside the hair, it is highly likely that the hair has been mixed in for a short time and that it is unlikely that the hair was mixed in during the manufacturing process.

[0064] Example 4: Element concentration analysis using EPMA to examine the penetration level of trace elements other than phosphorus and potassium in hair (1) Sample preparation Similarly, to verify whether it is possible to measure the degree of penetration or concentration distribution in hair for trace elements other than phosphorus and potassium, a saline solution with a concentration of 0.1% by mass was prepared, human hair was mixed into it, and either (i) it was heated at 120°C for 15 minutes and then immersed in an environment of about 20°C for half a day, or (ii) it was immersed in an environment of about 20°C for half a day. After a specified period of time had passed, the hair was removed from the saline solution, and the water adhering to the surface was wiped off to obtain a sample. From the obtained sample, a sample for element concentration analysis of the cross section of the sample was prepared using the method described in Example 1(2) above.

[0065] (2) Measurement of element concentration distribution Using the samples for element concentration analysis prepared above, the concentration distributions of sodium and chlorine in the cross section of the sample were measured according to the method described in Example 1(3) above and under the analytical conditions of the <Example>.

[0066] (3) Measurement results of element concentration distribution The potassium concentration distribution in the cross section of each sample was analyzed by an element mapping method as shown in FIG. 5, and the concentration distributions of the elements sodium and chlorine in the cross section were measured.

[0067] Figure 5 shows the measurement results of the sodium and chlorine concentration distribution in the cross section of each sample. The presence of both elements was confirmed throughout each sample, even inside the hair.

[0068] These results confirmed that it is possible to measure the penetration degree or concentration distribution in hair for trace elements other than phosphorus and potassium by analyzing them under the conditions of the above <Examples>, and demonstrated that various trace elements in food can be used to determine the time when hair was mixed into food.

[0069] Example 5: Element concentration analysis using EPMA to examine the penetration degree of trace elements in hair contaminated with chilled Chinese noodles (1) Sample preparation Assuming contamination during manufacturing, human hair was mixed into Chinese noodles in a commercially available chilled Chinese noodle packaged in a plastic container with a fitting lid that was distributed refrigerated (10°C or less) so that it came into contact with the noodles (contact with the Chinese noodle itself, not with the soup, etc.), the container was then fitted with a fitting lid, and the container was stored in a refrigerator (10°C or less) for 72 hours (3 days). After a prescribed period had passed, the hair was removed from the chilled Chinese noodle, and the moisture adhering to the surface was wiped off to obtain a sample, from which a sample for element concentration analysis of the cross section of the sample was prepared by the method described in Example 1(2) above. As controls, untreated human hair (i.e., not in contact with Chinese noodles) and human hair that had been exposed to Chinese noodles after the lid of the container of chilled Chinese noodles was opened and left at room temperature (20-28°C) for 20 minutes to simulate contamination after the product was opened were used, and samples for elemental concentration analysis were similarly prepared.

[0070] (2) Measurement of element concentration distribution The sample for each element concentration analysis prepared above was fixed on a sample stage for an elemental analyzer so that the cross section of the sample was facing upward. Next, the sodium concentration distribution of the cross section of each element concentration analysis sample was measured using an elemental analyzer EPMA (apparatus name: JXA-isp100, JEOL Ltd.) under the following analysis condition A. Since brine (kansui, water containing salts such as sodium chloride) is used in the production of Chinese noodles, the element measured was sodium.

[0071] Analysis conditions A: Acceleration voltage: 15 kV Irradiation current: 30nA Measurement time per pixel: 20mSec

[0072] (3) Measurement results of element concentration distribution FIG. 6 shows the results of analysis and measurement of the sodium concentration distribution in the cross section of each sample using the elemental mapping method. When analyzed under the above conditions, the presence of sodium was confirmed throughout the entire inside of a hair that had been stored on Chinese noodles for a specified period of time (a model of sodium contamination during product manufacturing).

[0073] The presence of sodium was barely detected inside untreated hair (i.e., hair not exposed to Chinese noodles) and human hair that had been exposed to Chinese noodles and left at room temperature (20-28°C) for 20 minutes (a model of contamination after the product was opened).

[0074] Sodium is a trace element found in Chinese noodles at approximately 66 mg / 100 g (Standard Tables of Food Composition in Japan 2020 Edition (8th Edition), Ministry of Education, Culture, Sports, Science and Technology). It was confirmed that under the above conditions, sodium could be detected that had penetrated from the surface of the Chinese noodles into the inside of the contaminated hair, even though the noodles were simply in contact with the noodles.

[0075] These results show that even in foods that contain sodium as a trace element, such as Chinese noodles, it is possible to detect and measure the degree of sodium penetration or concentration distribution within any foreign matter found in the food, and that it is possible to determine the time when the foreign matter was introduced based on the degree of penetration or concentration distribution of the trace element sodium.

[0076] Example 6: Element concentration analysis using EPMA to examine the degree of penetration of trace elements in insects (midges) that had been mixed into chilled Chinese noodles (1) Sample preparation Assuming contamination during manufacturing, chironomids (corpses) were mixed into the noodles of chilled Chinese noodles in a plastic container with a fitting lid that was commercially available and distributed refrigerated (below 10°C) so that they came into contact with the noodles (the noodles themselves, not the soup, etc.), the container was then fitted with a fitting lid, and the noodles were stored in a refrigerator (below 10°C) for 72 hours (3 days). After a specified period had passed, the chironomids were removed from the chilled Chinese noodles, and the moisture adhering to the surface was wiped off to obtain a sample, from which a sample cross-section for element concentration analysis was prepared using the method described below. As controls, untreated chironomids (corpses) (i.e., not brought into contact with Chinese noodles) and, to simulate contamination after the product was opened, chironomids (corpses) that had been brought into contact with Chinese noodles after the lid of the container of chilled Chinese noodles had been opened and left at room temperature (20-28°C) for 20 minutes were used, and samples for elemental concentration analysis were similarly prepared.

[0077] (2) Preparation of samples for elemental concentration analysis of cross-sections The chironomids prepared above were submerged in photopolymerized resin, and the resin was hardened with an ultraviolet ray irradiation device to produce a composite resin in which the specimens were encapsulated and hardened. Next, the cross sections of the abdomens of the specimens were surfaced using a cutter knife, sandpaper, etc. Next, gold was evaporated using a gold evaporation device to produce samples for element concentration analysis of the cross sections of each specimen.

[0078] (3) Measurement of element concentration distribution The sample for each element concentration analysis prepared above was fixed on a sample stage for an elemental analyzer so that the cross section of the sample was facing upward. Next, the sodium concentration distribution of the cross section of each element concentration analysis sample was measured using an elemental analyzer EPMA (apparatus name: JXA-isp100, JEOL Ltd.) under the following analysis condition B.

[0079] Analysis condition B: Acceleration voltage: 15 kV Irradiation current: 30nA Measurement time per pixel: 20mSec

[0080] (4) Measurement results of element concentration distribution Figure 7 shows the results of analysis and measurement of the sodium concentration distribution in the cross section of each sample using the elemental mapping method. When analyzed under the above conditions, the presence of sodium was confirmed inside the chironomids (a model of contamination during product manufacturing) that had been stored for a specified period on Chinese noodles.

[0081] The presence of sodium was barely detected inside untreated chironomids (i.e., not in contact with Chinese noodles) and chironomids that had been in contact with Chinese noodles and left at room temperature (20-28°C) for 20 minutes (model of contamination after product opening).

[0082] As mentioned above, sodium is a trace element in Chinese noodles, and it was confirmed that under the above conditions, sodium can be detected that has penetrated from the surface of the Chinese noodles into the inside of the contaminated chironomids, even though they are simply in contact with each other.

[0083] These results show that it is possible to detect and measure the degree of sodium penetration or concentration distribution inside foreign objects found in foods, whether the foreign object is a food that contains sodium as a trace element, such as Chinese noodles, or a foreign object such as an insect (chironomid), and that it is possible to determine the time when the foreign object was introduced based on the degree of penetration or concentration distribution of the trace element sodium.

[0084] Example 7: Element concentration analysis using EPMA to examine the penetration degree of trace elements in hair contaminated with buckwheat (1) Sample preparation Assuming contamination during manufacturing, human hair was mixed into noodles of cold soba noodles in a plastic container with a fitting lid that is commercially available and distributed refrigerated (10°C or less) so that it came into contact with the noodles (contact with the soba noodles themselves, not with the soup, etc.), the container was then covered with a fitting lid, and the container was stored in a refrigerator (10°C or less) for 72 hours (3 days). After a specified period had passed, the hair was removed from the cold soba noodles, and the moisture adhering to the surface was wiped off to obtain a sample, from which a sample for element concentration analysis of the cross section of the sample was prepared by the method described in Example 1(2) above. As controls, untreated human hair (i.e., not in contact with buckwheat noodles) and human hair that had been exposed to buckwheat noodles after the lid of the container of chilled soba noodles had been opened and left for 20 minutes at room temperature (20-28°C) were used as controls, and samples for elemental concentration analysis were similarly prepared.

[0085] (2) Measurement of element concentration distribution The sample for each element concentration analysis prepared above was fixed on a sample stage for an elemental analyzer so that the cross section of the sample was facing upward. Next, the phosphorus concentration distribution of the cross section of each element concentration analysis sample was measured using an elemental analyzer EPMA (apparatus name: JXA-isp100, JEOL Ltd.) under the following analysis condition C.

[0086] Analysis conditions C: Acceleration voltage: 15 kV Irradiation current: 100nA Measurement time per pixel: 40mSec

[0087] (3) Measurement results of element concentration distribution FIG. 8 shows the results of analyzing and measuring the phosphorus concentration distribution in the cross section of each sample using the element mapping method. When analyzed under the above conditions, the presence of phosphorus was confirmed throughout the inside of a hair (a model of contamination during product manufacturing) that had been stored on soba noodles for a specified period of time.

[0088] The presence of phosphorus was also confirmed inside untreated hair (i.e., hair that had not come into contact with buckwheat noodles) and human hair that had been in contact with buckwheat noodles and left at room temperature (20-28°C) for 20 minutes (a model of contamination after the product was opened); however, the amount was small compared to human hair that had been stored for 72 hours (3 days) (a model of contamination during product manufacturing).

[0089] Phosphorus is a trace element found in soba noodles at approximately 80 mg / 100 g (Standard Tables of Food Composition in Japan 2020 Edition (8th Edition), Ministry of Education, Culture, Sports, Science and Technology). It was confirmed that under the above conditions, phosphorus that had penetrated into the contaminated hair from the surface of the soba noodles could be detected, even though the noodles were simply in contact with each other.

[0090] These results show that even if a food contains phosphorus as a trace element, such as soba noodles, it is possible to detect and measure the degree of phosphorus penetration or concentration distribution within any foreign matter found in the food, and that it is possible to determine the time when the foreign matter was introduced based on the degree of phosphorus penetration or concentration distribution as a trace element.

[0091] Example 8: Element concentration analysis using EPMA to determine the degree of penetration of trace elements in insects (smoky-brown cockroach legs) that were mixed into radish salad (1) Sample preparation Assuming contamination during manufacturing, the legs of a Smoky Brown cockroach (corpse) were immersed in the electrolyzed water used in the manufacturing process, and then the legs of the Smoky Brown cockroach were mixed into shredded radish (contacting the vegetable itself, not the dressing, etc.) of a commercially available refrigerated (below 10°C) bagged radish salad so that they were in contact with it, and stored in a refrigerator (below 10°C) for 48 hours (2 days). After a specified period had passed, the legs of the Smoky Brown cockroach were removed from the radish salad, and the moisture on the surface was wiped off to obtain a sample, from which a sample for element concentration analysis of the cross section of the sample was prepared by the method described below. For controls, untreated (i.e., not immersed in electrolyzed water and not in contact with the shredded radish in the commercially available radish salad) legs of a Smoky Brown cockroach (corpse) and, assuming contamination after opening the product, the legs of a Smoky Brown cockroach (corpse) were not immersed in electrolyzed water but were placed in contact with the shredded radish in the commercially available radish salad and left in a refrigerator (below 10°C) for 48 hours (2 days) to prepare samples for element concentration analysis in the same manner.

[0092] (2) Preparation of samples for elemental concentration analysis of cross-sections The legs of the cockroach prepared above were immersed in the photopolymerization resin, and the resin was hardened with an ultraviolet irradiation device to produce a composite resin in which the sample was encapsulated and hardened. Next, the cross sections of the legs of the sample were surfaced using a cutter knife, sandpaper, etc. Next, gold was evaporated using a gold evaporation device to prepare samples for element concentration analysis of each sample cross section.

[0093] (3) Measurement of element concentration distribution The sample for each element concentration analysis prepared above was fixed on a sample stage for an elemental analyzer so that the cross section of the sample was facing upward. Next, the concentration distribution of chlorine was measured for the cross section of each element concentration analysis sample using an elemental analyzer EPMA (apparatus name: JXA-isp100, JEOL Ltd.) under the following analysis condition D. In the manufacture of commercially available bagged cut vegetables / salads, electrolyzed water is generally used to sterilize raw vegetables, and this electrolyzed water contains sodium hypochlorite at a concentration of approximately 80 ppm. Therefore, since the electrolyzed water contains approximately 38 ppm of chlorine, chlorine was measured as a trace element in this test.

[0094] Analysis conditions: Example D Acceleration voltage: 15 kV Irradiation current: 30nA Measurement time per pixel: 20mSec

[0095] (4) Measurement results of element concentration distribution Figure 9 shows the results of analyzing and measuring the chlorine concentration distribution in the cross section of each sample using the elemental mapping method. When analyzed under the above conditions, the presence of chlorine was confirmed throughout the entire inside of the legs of a Smoky Brown cockroach (a model of contamination during product manufacturing) that had been immersed in electrolyzed water and stored for a specified period of time on shredded radish in the commercially available radish salad.

[0096] The presence of chlorine was confirmed inside the legs of untreated Smoky Brown cockroaches (i.e., not in contact with electrolyzed water or the shredded radish in the commercially available radish salad) and inside the legs of Smoky Brown cockroaches that had not been immersed in electrolyzed water but had been in contact with the shredded radish in the commercially available radish salad and left in a refrigerator (below 10°C) for 48 hours (2 days) (model in which chlorine was mixed in after the product was opened); however, the amount of chlorine was smaller than that in the model in which chlorine was mixed in during product manufacturing.

[0097] These results confirmed that, under the above conditions, chlorine could be detected penetrating through the surface of the shredded radish onto the legs of a contaminated Smoky Brown cockroach, even though the cockroach had only been in contact with the shredded radish in a commercially available radish salad.

[0098] These results confirmed that it is possible to detect and measure the degree of penetration or concentration distribution of trace elements inside foreign objects found in foods, even if the foreign objects are foods that contain chlorine as a trace element, such as pre-cut vegetables / salads in bags, or foreign objects such as insects (cockroach legs).It was also shown that the time when the foreign object was introduced into the food can be determined based on the degree of penetration or concentration distribution of the trace elements.

[0099] From the above results, it was confirmed that it is possible to use various trace elements in foods to detect and measure the degree of penetration or concentration distribution of foreign matter contained in food for a wide variety of foods and foreign matter, and it was shown that the method of the present invention for determining the time of contamination of food with a foreign matter can be applied to a wide variety of foods and foreign matter.

Claims

1. A method for discriminating between contaminants in food, which comprises analyzing the degree of penetration of trace elements in food into contaminants that have been mixed into the food by an element concentration analysis method using an electron probe micro analyzer (EPMA) and discriminating the time of the contaminants being mixed in based on the results of the analysis of the degree of penetration, the method comprising the steps of: Acceleration voltage: 5 kV to 25 kV Irradiation current: 30nA to 200nA Measurement time per pixel: 20 mSec to 60 mSec.

2. 2. The method according to claim 1, wherein the trace element is an element present in an amount of 500 mg or less per 100 g of food.

3. 3. The method of claim 2, wherein the trace element is potassium, phosphorus, sodium, or chlorine.

4. The method according to claim 1, wherein the EPMA analysis conditions include the following conditions: Acceleration voltage: 15 kV Irradiation current: 30nA to 100nA Measurement time per pixel: 20 mSec to 40 mSec.

5. The method according to claim 1, wherein the analysis of the degree of penetration of trace elements in food into the foreign object is performed based on a cross-section of the foreign object.

6. The method described in claim 1, wherein the time of contamination of a foreign matter is determined in the case of a food that has not been heat-treated during the manufacturing process by comparing the degree of penetration of trace elements in the food into the contaminated foreign matter with the degree of penetration of the trace elements in the foreign matter that has been mixed into the food for a certain period of time and subjected to a preservation process to allow the trace elements in the food to penetrate.

7. The method described in claim 1, wherein the time of contamination with foreign matter is determined in the case of foods that have not been heat-treated during the manufacturing process by mixing a portion of the contaminating foreign matter into the food for a certain period of time and subjecting the food to a preservation treatment that allows trace elements in the food to penetrate into the contaminating foreign matter, and then comparing the degree of penetration of the trace elements in the food into the contaminating foreign matter that has been subjected to the preservation treatment with the degree of penetration of the trace elements in the food into the contaminating foreign matter that has not been subjected to the preservation treatment.

8. 7. The method of claim 6, wherein the food product is selected from the group consisting of tofu, soy milk, milk and dairy products, noodles, cut vegetables, salads, and food and beverage products containing one or more of the above.

9. The method described in claim 1, wherein the time when the foreign matter was mixed in is determined by comparing the degree of penetration of trace elements in the food into the foreign matter that has been heat-treated during the manufacturing process with the degree of penetration of trace elements in the food into the foreign matter that has been heat-treated under conditions equivalent to the heat treatment.

10. The method described in claim 1, wherein the time of contamination of a foreign matter is determined in the case of a food that has been heat-treated during the manufacturing process by heat-treating a portion of the contaminating foreign matter under conditions equivalent to those of the heat treatment, and comparing the degree of penetration of trace elements in the food into the heat-treated contaminating foreign matter with the degree of penetration of trace elements in the food into the non-heat-treated contaminating foreign matter.

11. The method of claim 1 , wherein the foreign object is a hair, an insect, or a part thereof.

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