JP7591966B2 - Method for estimating the time of contamination by metal foreign matter - Google Patents

Description

The present invention relates to a method for estimating the time of contamination of food and beverages with metal foreign matter based on the amount of iron element on the metal surface.

Food and beverages are taken into the body, so naturally their safety must be ensured. Therefore, in the quality control of food and beverage production, any matter that could be the cause of contamination must be thoroughly eliminated.

To implement such thorough quality control, it is necessary to accurately grasp the actual state of the foreign matter contamination, and for that purpose, it is important to first verify the timing of contamination, i.e. whether the foreign matter that was found in the food or beverage was introduced during the manufacturing process of the food or beverage or whether it was introduced after the manufacturing process (for example, after the product was opened).

For this reason, various methods have been developed and reported to estimate the time when foreign matter such as hair or plastic was mixed in (Non-Patent Documents 1 and 2).

Metals are generally resistant to corrosion caused by heating and are less susceptible to change, making it more difficult to estimate the time of contamination with metal foreign bodies than with other substances. Patent Document 1 describes that when metal pieces such as aluminum are found in food, the time of contamination can be estimated by measuring the amount of thermoluminescence from the metal pieces.

However, since it is possible that metals other than aluminum may be mixed in as foreign matter, there is still a strong need in this field for a new method that would enable estimation of the time of contamination by metallic foreign matter.

JP 2007-127442 A

"Method of Identifying Contaminated Hair" by Gen Sato, Science Forum Co., Ltd., 2000 Convertec, November 2002 issue, published by Kako Gijutsu Kenkyukai Publishing Co., Ltd., "DSC analysis of CPP film reveals history of retort heat treatment by utilizing phase transition from smectic to α crystals" (Ajinomoto Co., Inc. Production Technology Development Center)

The present invention aims to provide a new method that makes it possible to estimate the time when metal foreign matter was present in food and beverages.

It has been confirmed that some metal elements leach out from metals that come into contact with food and beverages (N. Mazinanian et al., CORROSION, Vol. 72, No. 6, p. 775-790, June, 2016). As a result of extensive research conducted by the inventors to solve the above problem, they discovered that there is a correlation between the elemental composition on the surface of metal foreign matter that has been mixed into food and beverages and the processing history, such as heating and preservation treatment, that the metal foreign matter was subjected to together with the food and beverage.

More specifically, the inventors discovered that the amount of iron element on the surface of iron-containing foreign metal objects contaminated in food and beverages is significantly reduced when the foreign metal objects are subjected to heat treatment, preservation treatment, and other processes together with the food and beverages, and discovered that by measuring the amount of iron element on the surface of the foreign metal objects, it is possible to determine whether the foreign metal objects have been subjected to the above-mentioned processes (i.e., whether the foreign metal objects have a history of the above-mentioned processes), and based on this, it is possible to estimate the time when the foreign metal objects were contaminated into the food and beverages.

The present invention is based on these new findings and includes the following inventions.
[1] A method for determining whether or not a foreign metal containing iron that has been mixed into a food or beverage has been processed during the manufacturing process and/or distribution process of the food or beverage, comprising:
The method includes a step of measuring the amount of iron element on the surface of the foreign metal and comparing the amount with a similarly measured amount of iron element on the surface of a control metal containing iron, the control metal either having the treatment history or not, and if the two values are equivalent, it is determined that the foreign metal, like the control metal, either has or does not have the treatment history.
[2] The method according to [1], wherein the metal is stainless steel.
[3] The method according to [1] or [2], wherein the amount of iron element on the surface of the metal is measured using X-ray photoelectron spectroscopy, Auger electron spectroscopy, or time-of-flight secondary ion mass spectrometry.
[4] The method according to any one of [1] to [3], wherein the surface of the metal is at a depth of 10 nm or less from the surface layer of the metal.
[5] The method according to any one of [1] to [4], wherein the treatment history is a heat treatment history and/or a storage treatment history.
[6] The method according to any one of [1] to [5], further comprising measuring an amount of chromium element and/or an amount of oxygen element on a surface of the metal, wherein the value of the amount of iron element is expressed as a ratio of the amount of chromium element or the amount of oxygen element to the amount of iron element on the surface of the metal (Cr or O/Fe value).
[7] A method for estimating the time of contamination of a metal containing iron that has been present as a foreign body in a food or beverage, comprising the steps of: determining whether or not the food or beverage has a processing history during its manufacturing and/or distribution process by any of the methods [1] to [6]; and, if the metal has a processing history, estimating that the metal was present during the manufacturing and/or distribution process of the food or beverage.

The present invention provides a new method that makes it possible to estimate the time when metal foreign matter was present in food and beverages.

Figure 1 shows the results of an analysis of the concentration (%) of various metal elements of SUS304 stainless steel mixed into tomato sauce by X-ray photoelectron spectroscopy (XPS). The samples shown are (a) unmixed foreign matter, (b) foreign matter mixed in after opening the package, and (c) foreign matter mixed in during the manufacturing process. The vertical axis shows the metal element concentration (%), and the horizontal axis shows the depth (nm) from the metal surface. Figure 2 shows the results of an XPS analysis of the concentration (%) of various metal elements in stainless steel SUS420J2 mixed into tomato sauce. The samples shown are (a) unmixed foreign matter, (b) foreign matter mixed in after opening, and (c) foreign matter mixed in during the manufacturing process. The vertical axis shows the metal element concentration (%), and the horizontal axis shows the depth (nm) from the metal surface. 3 shows the results of an XPS analysis of the concentration (%) of various metal elements in stainless steel SUS420J2 mixed into white sauce. The samples shown are (a) unmixed foreign matter, (b) foreign matter mixed in after opening, and (c) foreign matter mixed in during the manufacturing process. The vertical axis shows the metal element concentration (%), and the horizontal axis shows the depth (nm) from the metal surface. 4 shows the results of an XPS analysis of the concentration (%) of various metal elements in stainless steel SUS420J2 mixed in water. The samples shown are (a) unmixed foreign matter, (b) foreign matter mixed in after opening the package, and (c) foreign matter mixed in during the manufacturing process. The vertical axis shows the metal element concentration (%), and the horizontal axis shows the depth (nm) from the metal surface. 5 shows the results of an XPS analysis of the concentration (%) of various metal elements in SUS304 stainless steel mixed into tomato sauce. The samples shown are (a) unmixed foreign matter, (b) foreign matter not subjected to heating, and (c) foreign matter subjected to heating. The vertical axis shows the metal element concentration (%), and the horizontal axis shows the depth (nm) from the metal surface. 6 shows the results of an XPS analysis of the concentration (%) of various metal elements in stainless steel SUS420J2 mixed into tomato sauce. The samples shown are (a) unmixed foreign matter, (b) foreign matter not subjected to heating, and (c) foreign matter subjected to heating. The vertical axis shows the metal element concentration (%), and the horizontal axis shows the depth (nm) from the metal surface. 7 shows the results of an XPS analysis of the concentration (%) of various metal elements in SUS304 stainless steel mixed into tomato sauce. The samples shown are (a) unmixed foreign matter, (b) foreign matter mixed in for a short period of time, and (c) foreign matter mixed in for a long period of time. The vertical axis shows the metal element concentration (%), and the horizontal axis shows the depth (nm) from the metal surface. 8 shows the results of an XPS analysis of the concentration (%) of various metal elements in stainless steel SUS420J2 mixed into tomato sauce. The samples shown are (a) unmixed foreign matter, (b) foreign matter mixed for a short time, and (c) foreign matter mixed for a long time. The vertical axis shows the metal element concentration (%), and the horizontal axis shows the depth (nm) from the metal surface.

The present invention relates to a method for determining whether or not iron-containing metals that have been mixed into food or beverages as foreign matter have been processed during the manufacturing and/or distribution process of the food or beverage.

In the present invention, "food and beverage" refers to dishes served in restaurants and the like, and various processed foods and beverages that can be distributed frozen, chilled, at room temperature, etc. Examples of processed foods and beverages include retort products such as curry, stew, soup, sauce, etc., roux products such as curry and stew, frozen foods and beverages, various spice products such as wasabi paste, mustard paste, mustard, etc., seasoning products such as mayonnaise and dressings, dairy products such as yogurt, butter, cheese, ice cream, etc., dessert products such as jelly and pudding, dessert bases for preparing dessert products, confectionery products such as chocolate and cookies, beverage products such as tea, coffee, fruit drinks, carbonated drinks, vitamin drinks, soft drinks, etc., but are not limited to these.

In the present invention, a "foreign matter" refers to a metal containing iron, and examples of such metals include iron and alloys containing iron (e.g., stainless steel, steel, etc.), with stainless steel (also called stainless steel) being preferred. There are no particular limitations on the type of stainless steel, and it may be any of austenitic (e.g., SUS304, etc.), austenitic-ferritic (e.g., SUS329J1, etc.), ferritic (e.g., SUS430, etc.), and martensitic (e.g., SUS420J2, etc.).

According to the present invention, it is possible to determine whether the metal that has been mixed in as a foreign body has been subjected to a process such as heating or preservation together with the food or drink, and based on this, it is possible to estimate when the foreign metal was mixed in with the food or drink, for example, whether it was mixed in during the manufacturing process and/or distribution process of the food or drink, or whether it was mixed in after the manufacturing process and/or distribution process of the food or drink (for example, after the product was opened). This can be done by analyzing and measuring the amount of iron element on the surface of the mixed metal.

In the present invention, the "metal surface" to be analyzed and measured may vary depending on the type of food or metal, but is within 70 nm from the surface layer (depth 0 nm) of the metal, for example, within 60 nm, 50 nm, 40 nm, 30 nm, or 20 nm, and is preferably within 10 nm, more preferably within 5 nm (for example, within 4 nm), and even more preferably within 3 nm, 2 nm, or 1 nm. For example, when the metal is austenitic stainless steel (e.g., SUS304, etc.), the "metal surface" to be analyzed and measured may be within 10 nm from the surface layer (depth 0 nm), for example, within 5 nm or 4 nm, and preferably within 3 nm. For example, when the metal is martensitic stainless steel (e.g., SUS420J2, etc.), the "metal surface" to be analyzed and measured can be within 60 nm from the surface layer (depth 0 nm), for example, within 30 nm, 2 or 0 nm, preferably within 10 nm, 5 nm, or 4 nm, more preferably within 3 nm.

In the present invention, the analysis and measurement of the "amount of iron element on the surface of a metal" can be performed using a conventionally known method for analyzing the surface of a material. Examples of such methods for analyzing the surface of a material include mass analysis methods such as X-ray photoelectron spectroscopy, Auger electron spectroscopy, secondary ion mass spectrometry, and time-of-flight secondary ion mass spectrometry, but are not limited to these.

X-ray photoelectron spectroscopy (XPS) is a method for analyzing the composition and chemical bonding state of elements that make up a sample surface by irradiating the sample surface with X-rays under ultra-high vacuum and measuring the kinetic energy of photoelectrons emitted from the sample surface due to the photoelectric effect. In addition, the elements can be quantified using peak area ratios. Furthermore, by combining this with ion etching (e.g., Ar ⁺ ion etching or C ₆₀ ⁺ ion etching), analysis in the depth direction can be performed.

Auger electron spectroscopy (AES) is a method for identifying the composition of elements that make up a sample surface by irradiating the sample with an electron beam and analyzing the energy spectrum of Auger electrons emitted from the sample surface (because Auger electrons have a specific energy for each element). In addition, the element can be quantified by using the peak intensity ratio. Furthermore, by combining with ion etching (e.g., Ar ⁺ ion etching), analysis in the depth direction can be performed.

Secondary ion mass spectrometry (SIMS) is a method of irradiating a sample surface with a continuous beam of chemically active ions (primary ions) such as cesium or oxygen in a vacuum, stirring atoms near the surface and causing neutral particles, secondary ions, and secondary electrons to fly out (so-called sputtering), and the secondary ions are analyzed (separated) and detected to determine and measure molecular weight. Sputtering using a continuous beam of primary ions makes it possible to perform depth profile analysis (this method is also called "dynamic SIMS"). On the other hand, ions (primary ions) such as gallium, gold, and bismuth can be pulsed onto the sample surface in a vacuum to cause fragment ions and molecular ions (secondary ions) to fly out from the extreme surface of the sample, which can be analyzed (separated) and detected (this method is also called "static SIMS"). In the present invention, static SIMS, which allows analysis of the outermost surface of a sample, can be suitably used to analyze the cross section of the sample.

Time-of-Flight Secondary Ion Mass Spectrometry (TOF-SIMS) is a mass spectrometry method that combines time-of-flight mass spectrometry (TOF-MS) and secondary ion mass spectrometry (SIMS). In TOF-SIMS, the SIMS can use the static SIMS described above. In static SIMS, fragment ions and molecular ions (secondary ions) that are ejected from the extreme surface of the sample by pulsed irradiation of primary ions are accelerated between high-voltage electrodes and made to fly at a constant speed toward the ion detector in a tube in a high vacuum field-free region (so-called flight tube). In this case, the lower the molecular weight, the faster it reaches the ion detector, and the higher the molecular weight, the slower it reaches the ion detector. By measuring the time it takes for the ion to reach the detector, the molecular weight of the molecule can be determined and measured.

These surface analysis techniques can be used in appropriate combination with sample ionization techniques such as matrix-assisted laser desorption ionization, laser desorption ionization, sputtering (secondary ion emission), fast atom bombardment, electrospray ionization, desorption ion electrospray ionization, scanning probe electrospray ionization, atmospheric pressure chemical ionization, atmospheric pressure direct ionization, inductively coupled plasma, electron ionization, chemical ionization, and field desorption ionization.

In the present invention, the amount of iron element on the surface of iron-containing metal (hereinafter sometimes referred to as "foreign metal") contaminated in food or beverage is measured, and the amount is compared with the amount of iron element on the surface of a control iron-containing metal (hereinafter sometimes referred to as "control metal") measured under the same conditions, thereby making it possible to determine whether the foreign metal has a processing history during the manufacturing and/or distribution process of the food or beverage.

In the present invention, the "control iron-containing metal" or "control metal" can be a metal equivalent to, and preferably the same type as, the foreign metal contaminated in the food or drink, or a part of the foreign metal contaminated in the food or drink, which is prepared by adding it to a food or drink corresponding to the food or drink contaminated with the foreign metal and processing it, or a food or drink that has not been subjected to the processing and whose history of processing is clear. "Corresponding food or drink" means that it is equivalent or of the same quality as the food or drink contaminated with the foreign metal, and can be the food or drink actually contaminated with the foreign metal, or the same food or drink as the food or drink actually contaminated with the foreign metal.

In the preparation of the control metal, the treatment in which a specific metal is applied to the corresponding food or beverage refers to one or more treatments that the food or beverage containing the foreign metal is subjected to during its manufacturing and/or distribution process. Such treatments include heat treatments when the food or beverage is a food or beverage that has been heat-treated during its manufacturing process. Heat treatments include heat cooking, sterilization, fermentation heat treatments, etc. For example, heat cooking includes treatment at 30 to 120°C for 4 minutes to 24 hours depending on the food or beverage being produced. Sterilization includes retort sterilization (pressure heat sterilization). Retort sterilization can be performed by sealing the food or beverage in a pouch or container and then generally heating the center to a temperature of 120°C for 4 minutes or by a method having an equivalent or greater effect. Fermentation heat treatments include treatment at 20 to 30°C for 5 to 24 hours. Such treatments also include preservation treatments in which the food or beverage is preserved for a specified time under specified temperature conditions. The temperature and time can be appropriately determined depending on the manufacturing and distribution process of the food and drink, and can be refrigerated to room temperature (e.g., 4°C to 40°C) and 1 minute to 1 month (e.g., 10 minutes, 1 day, 3 days, 5 days, 7 days, 10 days, 15 days, 20 days, 30 days). These treatments can be used in appropriate combinations depending on the manufacturing and distribution process of the food and drink that was contaminated with the foreign metal, for example, a heat treatment can be performed and then a preservation treatment can be performed. For example, the "control metal" can be prepared by adding it to a food and drink corresponding to the food and drink that was contaminated with the foreign metal, and then subjecting the food and drink to a retort sterilization treatment and then a preservation treatment, or it can be prepared by adding it and then subjecting it to a preservation treatment without subjecting it to a heat treatment.

When the comparison results show that the "amount of iron element on the metal surface" of the control metal and the foreign metal are equivalent, this indicates that the foreign metal, like the control metal, has a history of being subjected to the above-mentioned treatment during the manufacturing and/or distribution process together with the food or drink, or has not been subjected to the treatment. Here, "equivalent" with respect to the value means that the difference between the two is within 2 times, preferably within 1.5 times, and more preferably within 1.3 times. In general, when a foreign metal that has been mixed into a food or drink has been subjected to the above-mentioned treatment during the manufacturing and/or distribution process together with the food or drink, a decrease in the amount of iron element on the metal surface is observed compared to when the foreign metal has not been subjected to the treatment.

On the other hand, when the "amount of iron element on the metal surface" of the control metal and the measurement result of the foreign metal are different from each other as a result of the comparison, more specifically, when the amount of iron element on the metal surface of the foreign metal is higher than that of the control metal, it indicates that the foreign metal has not been subjected to the above-mentioned treatment in the manufacturing process and/or distribution process, for example, that the control metal has not been subjected to the above-mentioned treatment in the manufacturing process and/or distribution process. Here, "different" or "higher" in the value means that the difference between the two is more than two times, preferably three times or more, and more preferably five times or more. In general, when the foreign metal that has been mixed into food and beverage has not been subjected to the above-mentioned treatment in the manufacturing process and/or distribution process together with the food and beverage, there is no reduction in the amount of iron element on the metal surface compared to the control metal that has been subjected to the above-mentioned treatment.

In the present invention, in addition to the amount of iron element on the surface of the foreign metal, the amount of chromium element and/or the amount of oxygen element on the surface can be used to determine whether the foreign metal has the above-mentioned treatment history. The amount of chromium element and/or the amount of oxygen element on the surface of the foreign metal can be analyzed and measured by the same method as the amount of iron element, and the ratio of the amount of chromium element or the amount of oxygen element to the amount of iron element (hereinafter referred to as "Cr or O/Fe value") is calculated based on each of the obtained values. The result is compared with the Cr or O/Fe value calculated by analyzing and measuring a control metal under the same conditions, and the presence or absence of the above-mentioned treatment history of the foreign metal can be determined.

In general, if a foreign metal that has been mixed into a food or beverage has been subjected to the above-mentioned treatment during the manufacturing and/or distribution process together with the food or beverage, an increase in the amount of chromium and/or oxygen elements is observed on the metal surface compared to when the food or beverage has not been subjected to said treatment. On the other hand, since the variation in the amount of iron element on the surface of the foreign metal is as described above, by using the Cr or O/Fe value, it is possible to more clearly confirm whether or not a foreign metal that has been mixed into a food or beverage has been subjected to the above-mentioned treatment during the manufacturing and/or distribution process together with the food or beverage.

That is, when the Cr or O/Fe value comparison results show that the values of the control metal and the foreign metal are equivalent, it indicates that the foreign metal, like the control metal, has a history of being subjected to the above-mentioned treatment in the manufacturing process and/or distribution process together with the food or drink, or has not been subjected to the above-mentioned treatment. Here, "equivalent" with respect to the value means that the difference between the two is within 2 times, preferably within 1.5 times, and more preferably within 1.2 times. On the other hand, when the Cr or O/Fe value comparison results show that the values of the control metal and the foreign metal are different, more specifically, when the Cr or O/Fe value of the foreign metal is lower than the Cr or O/Fe value of the control metal, it indicates that the foreign metal has not been subjected to the above-mentioned treatment in the manufacturing process and/or distribution process, for example, the above-mentioned treatment in the manufacturing process and/or distribution process applied to the control metal. Here, "different" or "lower" with respect to the value means that the difference between the two is more than 2 times, preferably 3 times or more, and more preferably 5 times or more.

In any of the above embodiments, the control metal is subjected to a method of analyzing and measuring the amount of elements on the surface of the metal under the same conditions as the foreign metal, but the analysis and measurement of the control metal may be performed each time, or the analysis and measurement of the control metal alone may be performed in advance and the obtained value may be obtained as a "reference value" or "cutoff value." The value obtained from the foreign metal may be compared with the previously set "reference value" or "cutoff value" and used for the above judgment.

The present invention also relates to a method for estimating the time when a foreign metal was mixed into food or beverage, based on the presence or absence of the processing history of the foreign metal that was mixed into the food or beverage.

When the above method is used to determine that the foreign metal has the above-mentioned processing history, it suggests that the foreign metal was subjected to the processing together with the food or beverage, and it is presumed that the foreign metal was mixed in during the manufacturing and/or distribution process of the food or beverage. On the other hand, when the foreign metal is determined not to have the above-mentioned processing history, it indicates that the foreign metal was not subjected to the processing together with the food or beverage, and it can be presumed that the foreign metal was mixed in after the manufacturing and/or distribution process of the food or beverage (for example, after the product was opened).

The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these.

Example 1: Analysis of SUS304 stainless steel contaminated in retort tomato sauce

1-1. Sample preparation A 15 x 15 x 2 mm (#400 polished) stainless steel plate SUS304 was subjected to the following treatment to prepare metal samples representing different stages of food contamination. The food used was retort tomato sauce (Kagome "Basic Tomato Sauce"). After treatment, the sample was washed with water and acetone.

process:
(a) Unadulterated foreign bodies: Untreated (not introduced into food)
(b) Foreign matter that was mixed in after opening: Food that was mixed in for 30 minutes. (c) Foreign matter that was mixed in during the manufacturing process: Food that was retorted in an autoclave at 120°C for 30 minutes and then stored in a refrigerator for 3 days.

1-2. XPS Analysis The surface of each sample was measured using an X-ray photoelectron spectroscopy (XPS) device (Quantera SXM manufactured by ULVAC-PHI). First, an XPS wide spectrum measurement was performed to confirm the detected elements. The measurement conditions were as follows:
Radiation source: Monochrome Al-Kα
Voltage: 15 kV
Output: 25W
Beam diameter: 100 μm
Measurement range: 0 to 1400 eV
Pass Energy: 280eV
Step Size: 1eV

The elements detected by wide spectrum measurement were C, N, O, Cr, Fe, Ni, and P in all samples.

Next, an XPS depth profile analysis was performed by combining an XPS narrow spectrum measurement of each detected element and Ar sputtering under the following measurement conditions.
Pass Energy: 112eV
Step Size: 0.1eV
Index peaks: C1s, N1s, O1s, Cr2p, Fe2p, Ni2p3

The measurement results are shown in Figure 1. It was confirmed that in all samples, the Fe ratio increases from the surface to a depth of approximately 10 nm. It was also confirmed that the O ratio decreases over a depth of approximately 10 nm.

Furthermore, a comparison of the element ratios of each sample confirmed that sample (c), which is assumed to have been contaminated during manufacturing, has a lower Fe ratio near the depth of 0-3 nm compared to the other samples (a) and (b). In addition, a higher Cr ratio near the depth of 0-3 nm was confirmed.

The above results show that when the Fe concentration on the surface of a stainless steel plate that has been found to be contaminated as a foreign object in a food product is measured and it is confirmed that the concentration is lower than that of the control, it can be inferred that the foreign object has a heating history during the product manufacturing process and is highly likely to have been mixed in before the product was opened. In particular, when the increase in Cr concentration and decrease in Fe concentration on the surface of a stainless steel plate that has a heating history shows that the concentration ratio of Cr to Fe on the surface (Cr/Fe value) is different from that of the control (larger in this example), it can be inferred that the foreign object is highly likely to have been mixed in before the product was opened.

Example 2: Analysis of stainless steel SUS420J2 contaminated in retort tomato sauce and white sauce

2-1. Sample preparation A 15 x 15 x 2 mm (#400 polished) stainless steel plate SUS420J2 was subjected to the following treatment to prepare metal samples representing different stages of food contamination. The foods used were retort tomato sauce and white sauce (Nissin Foods "Milk-filled Carbonara"). After treatment, the samples were washed with water and acetone.

process:
(a) Unadulterated foreign bodies: Untreated (not introduced into food)
(b) Foreign matter that was mixed in after opening: Food that was mixed in for 30 minutes. (c) Foreign matter that was mixed in during the manufacturing process: Food that was retorted in an autoclave at 120°C for 30 minutes and then stored in a refrigerator for 3 days.

2-2. XPS Analysis The surface of each sample was measured by an X-ray photoelectron spectroscopy (XPS) device. First, an XPS wide spectrum measurement was performed to confirm the detected elements. The measurement conditions were the same as those in Example 1.

The elements detected in all samples were C, N, O, Cr, and Fe. P was also detected in some samples.

Next, XPS depth profile analysis was performed using a combination of XPS narrow spectrum measurement of each detected element and Ar sputtering. The measurement conditions were the same as in Example 1.

As a result, it was confirmed that in both samples, the Fe concentration changed from low to high from the surface to a depth of approximately 10 nm. It was also confirmed that the O concentration changed from high to low from the surface to a depth of approximately 10 nm.

In the case of tomato sauce (Figure 2), a comparison of the elemental ratios of each sample revealed that sample (c), which is assumed to have been mixed in during manufacturing, had a lower Fe ratio at a depth of 0-60 nm compared to the other samples (a) and (b). Additionally, a higher O and Cr ratio was confirmed in the same depth range.

On the other hand, in the case of white sauce (Figure 3), sample (c), which is assumed to have been contaminated during manufacturing, was found to have a lower ratio of Fe at a depth of 0-20 nm compared to the other samples (a) and (b). Also, a high ratio of O and Cr was found in the depth range of 5-20 nm.

In addition, when samples (b) and (c) were prepared using water instead of food, the decrease in the Fe ratio was slight, even in sample (c), which is assumed to have been contaminated during manufacturing (Figure 4).

These results show that, regardless of the type of stainless steel or food, the Fe concentration, Cr and O concentration on the surface of a stainless steel plate found in food as a foreign object can be used to determine whether the foreign object has a heating history during the manufacturing process, and it is possible to estimate when the foreign object was introduced into the product (whether it was before the product was opened or not).

Example 3: Analysis of stainless steel mixed into tomato sauce and heated, and stainless steel that was not heated

3-1. Sample preparation Stainless steel plates SUS304 and SUS420J2 measuring 15 x 15 x 2 mm (polished with #400) were mixed into tomato sauce in a retort and subjected to the following treatment to prepare metallic foreign matter that had not been heated and metallic foreign matter that had been heated in a retort. After the treatment, the samples were washed with water and acetone.

process:
(a) Unadulterated foreign bodies: Untreated (not introduced into food)
(b) Foreign matter that has not been heated: The foreign matter was mixed in and stored in a refrigerator for three days without being heated. (c) Foreign matter that has been heated in a retort: The foreign matter was heated in an autoclave at 120°C for 30 minutes and then stored in a refrigerator for three days.

3-2. XPS Analysis The surface of each sample was measured by an X-ray photoelectron spectroscopy (XPS) device. First, an XPS wide spectrum measurement was performed to confirm the detected elements. The measurement conditions were the same as those in Example 1.

The elements detected in all samples were C, N, O, Cr, Fe, and P.

Next, XPS depth profile analysis was performed using a combination of XPS narrow spectrum measurement of each detected element and Ar sputtering. The measurement conditions were the same as in Example 1.

As a result, it was confirmed that in both samples, the Fe concentration changed from low to high from the surface to a depth of approximately 10 nm. It was also confirmed that the O concentration changed from high to low from the surface to a depth of approximately 10 nm.

Comparing the element ratios of each SUS304 sample, it was confirmed that sample (c) that had been subjected to retort heating had a lower Fe ratio near the depth of 0-3 nm compared to the other samples (a) and (b). It was also confirmed that samples (b) and (c) had a higher Cr ratio near the depth of 0-3 nm (Figure 5).

Comparing the elemental ratios of each SUS420J2 sample, it was confirmed that sample (c) that had been subjected to retort heating had a lower Fe ratio at a depth of 0-60 nm compared to the other samples (a) and (b). It was also confirmed that in the same depth range, the ratios of O and Cr were high. It was also confirmed that (b) had a lower Fe ratio and a higher Cr ratio at a depth of around 0-3 nm compared to (c) (Figure 6).

These results show that even if the foreign matter has been present in the food product for a long time, it is possible to determine whether the foreign matter has had a heating history during the manufacturing process of the product by using the Fe concentration, Cr and O concentrations on the surface of the stainless steel plate, and to estimate the time when the foreign matter was present in the product (whether it had a heating history).

Example 4: Analysis of stainless steel mixed into tomato sauce for a short period of time and for a long period of time

4-1. Sample preparation Stainless steel plates SUS304 and SUS420J2 measuring 15 x 15 x 2 mm (polished with #400) were mixed into retort tomato sauce and subjected to the following treatments to produce metal foreign bodies with different mixing times. Heating was not applied. After treatment, the samples were washed with water and acetone.

process:
(a) Unadulterated foreign bodies: Untreated (not introduced into food)
(b) Foreign matter mixed in for a short period of time: left to stand in the mixed state for 30 minutes. (c) Foreign matter mixed in for a long period of time: kept in a refrigerator for 3 days in the mixed state.

4-2. XPS Analysis The surface of each sample was measured by an X-ray photoelectron spectroscopy (XPS) device. First, an XPS wide spectrum measurement was performed to confirm the detected elements. The measurement conditions were the same as those in Example 1.
The elements detected in all samples were C, N, O, Cr, Fe, and P.

Next, XPS depth profile analysis was performed using a combination of XPS narrow spectrum measurement of each detected element and Ar sputtering. The measurement conditions were the same as in Example 1.

As a result, it was confirmed that in both samples, the Fe concentration changed from low to high from the surface to a depth of approximately 10 nm. It was also confirmed that the O concentration changed from high to low from the surface to a depth of approximately 10 nm.

Comparing the element ratios of each SUS304 sample, it was confirmed that the foreign matter (c) that had been mixed in for a long time had a lower Fe ratio and a higher Cr ratio at a depth of around 0-3 nm compared to the other samples (a) and (b) (Figure 7).

Comparing the elemental ratios of each sample of SUS420J2, it was confirmed that the foreign material mixed in for a long time (c) had a lower Fe ratio at a depth of 0-3 nm compared to the foreign material mixed in for a short time (b). It was also confirmed that the foreign material mixed in for a short time (b) had a lower Fe ratio compared to the foreign material not mixed in (a). Furthermore, it was confirmed that (b) and (c) had a higher Cr ratio than (a) (Figure 8).

These results show that the Fe and Cr concentrations on the surface of a stainless steel plate found to be contaminated in food can be used to determine the degree of storage history and the presence or absence of a foreign object, and that the period during which the foreign object was present in the product can be estimated.

As described above, according to the present invention, the Fe concentration and the Cr and O concentrations on the surface of a stainless steel plate that has been found to be contaminated as a foreign object in food can be used to determine whether or not the foreign object has a processing history during the manufacturing or storage process of the product, and the period during which the foreign object was present in the product can be estimated.

Claims (5)

A method for determining whether or not a foreign metal containing iron that has been mixed into a food or beverage has been processed during the manufacturing process and/or distribution process of the food or beverage, comprising:
measuring the amount of iron element on the surface of the foreign metal and comparing the amount with a similarly measured amount of iron element on the surface of a control metal containing iron, the control metal either having or not having the treatment history, and if the two values are equivalent, determining that the foreign metal, like the control metal, either has or does not have the treatment history ;
The metal is stainless steel,
The method , wherein the treatment history is a heat treatment history and/or a preservation treatment history . 2. The method of claim 1 , wherein the amount of elemental iron on the surface of the metal is measured using X-ray photoelectron spectroscopy, Auger electron spectroscopy, or time-of-flight secondary ion mass spectrometry. The method according to claim 1 or 2 , wherein the surface of the metal is within a depth of 10 nm from the surface layer of the metal. The method according to any one of claims 1 to 3, further comprising measuring an amount of chromium element and/or an amount of oxygen element on a surface of the metal, and the value of the amount of iron element is expressed as a ratio of the amount of chromium element or the amount of oxygen element to the amount of iron element on the surface of the metal ( Cr or O/Fe value). A method for estimating the time of contamination of food and beverages with iron-containing metals that have been contaminated as foreign matter, comprising:
A step of determining the presence or absence of a processing history during the manufacturing process and/or distribution process of the food or beverage by the method according to any one of claims 1 to 4 ;
If the metal has the processing history, a step of estimating that the metal was mixed in during the manufacturing process and/or distribution process of the food or beverage;
Including,
The metal is stainless steel,
The method , wherein the treatment history is a heat treatment history and/or a preservation treatment history .