JP2022117893A - Method for estimating heating history of resin product - Google Patents

Abstract

To develop a method for estimating a heating history of resin and make it possible to estimate whether a foreign substance made of resin found in a process including a heating process of a processed food product, etc. is mixed before the heating process or mixed after the heating process using a method of determining degradation (oxidation) by heating.SOLUTION: A heating history of a resin product is investigated by using FT-IR to examine the infrared absorption on a surface and inside of a target resin material at wavelengths in a range of 1,650 to 1,750 cm-1.SELECTED DRAWING: Figure 1

Description

The present invention relates to a method of estimating the heating history of resin or the like. The present invention also relates to a method that can estimate the mixing time of a resinous foreign substance mixed in the food manufacturing process by using the present estimation method.

Resin materials such as plastics are used in many fields, but it is known that the resin materials are gradually degraded (oxidized) by oxygen in the air. In particular, heat and light accelerate the deterioration.
On the other hand, it is often difficult to determine the heating history of the resin by visually inspecting the resin itself. Therefore, it would be convenient if there was a method for objectively estimating the heating history of the resin.

Furthermore, it is extremely rare that a foreign substance made of resin is found as a foreign substance in the manufacturing process of processed foods. In such a case, if the processed food has a manufacturing process such as heating, the resin foreign matter is mixed before the heat treatment process of the processed food or mixed after the heat treatment process. It would be useful to be able to estimate the origin of the substance and more accurately estimate the timing of contamination.

Furthermore, if the resin-made foreign matter is broken by some kind of impact or the like, that is, if the foreign matter has the fractured surface, the deterioration (oxidation) state of the fractured surface is examined to determine whether the fractured surface is broken. It is more useful if it is possible to estimate whether the timing of is before heating or after heating.
As a prior art related to such a field, for example, Prior Art Document 1 discloses a method of estimating the timing of mixing of resin pieces using DSC (differential scanning calorimetry).

JP 2009-128010

On the other hand, the method of measuring the mixing timing of the prior art uses DSC, but it is pointed out that DSC heats the resin piece to be measured, which causes heating damage to the sample. be done. This problem is particularly serious when the amount of resin pieces is small. Therefore, there is still room for examination of other measurement methods.

Therefore, the inventors of the present invention set the task of developing a new method as a method for estimating the heating history of resin. Furthermore, by using the deterioration (oxidation) determination method, it is estimated whether the resin foreign matter found in the process including the heating process of processed food was mixed before the heating process or after the heating process. The challenge was to make it possible to

As a result of intensive research by the present inventors, FT-IR is used to examine the absorption of infrared absorption at a wavelength within the range of 1650 to 1750 cm-1 for the surface and interior of a resinous substance of interest. Thus, the inventors have found that it is possible to examine the heating history of the resin product, and completed the present invention.
That is, the first invention of the present application is
"For the deterioration or oxidation state of the surface or inside of the resin product, the infrared absorption of the wavelength within the range of 1650 to 1750 cm ^-1 by Fourier transform infrared spectroscopy (FT-IR) is measured on the surface or inside of the resin product. A method of estimating the heating history of the resin product by measuring it.”

Next, in the present invention, the surface or internal oxidation state is preferably mapped by measuring the infrared absorption at a plurality of points on the surface or inside the resin product.
That is, the second invention of the present application is
"A method according to claim 1, wherein the surface or internal degradation (oxidation) state is mapped by measuring the infrared absorption at multiple points on or within the resin product."

Furthermore, the resin product can be used for analysis of resin-made foreign matters that have been mixed in during the production of foods including a heating process or during subsequent distribution.
That is, the third invention of the present application is
"The method according to claim 1 or 2, wherein said resinous product is a resinous foreign matter mixed in during the production of processed food including a heating process."

In particular, for resin foreign matter found in a processed food manufacturing factory that involves heating, it is possible to estimate before and after heating by measuring the degree of deterioration (oxidation) by performing the surface mapping of the present invention. Therefore, an important effect can be exhibited in foreign matter inspection.
That is, the fourth invention of the present application is
"Using the method according to claim 3, resin-made foreign matter mixed in during the production of processed foods including the heating process or during subsequent distribution, and the foreign matter mixed in before the heating process or a method of estimating whether it was mixed after the heating process.",

Furthermore, each of the above inventions can be suitably used when the resin piece of the foreign matter to be measured has a fracture surface in a state of being fractured by an impact or the like.
That is, the fifth invention of the present application is
"When the resin foreign matter has a fracture surface, the resin foreign matter may be broken before the heating process or after the heating process using the method of claim 4. A method for estimating whether

By using the estimation method of the present invention, it is possible to grasp the deterioration (oxidation) state of the resin product, and by using this, it is possible to estimate the heating history of the foreign matter during food production. In addition, it is possible to estimate the time when the foreign matter is introduced.
Furthermore, if the foreign matter has a fractured surface, it can be estimated whether the foreign matter made of resin was broken before the heating step or after the heating step.

FIG. 10 is a diagram of infrared microscope FT-IR measurement results of a section of a polypropylene resin piece after heating. FIG. 2 is a diagram showing a method of preparing a cross section for infrared microscope FT-IR measurement after deterioration of a resin piece in Test Example 1. FIG. 4 is a photograph showing a change in the appearance of a resin piece on each day after UV irradiation and after thermal deterioration in Test Example 1. FIG. FIG. 3 is a diagram showing the results of surface state mapping by an infrared microscope FT-IR of a sliced sample after a deterioration test by UV irradiation in Test Example 1; FIG. 10 is a diagram showing the mapping results of the infrared microscope FT-IR surface state of the sliced sample after the deterioration test due to thermal deterioration in Test Example 1 (partly including the results after heating with palm oil). 4 is a photograph before heating of a fulcrum resin cover used in Test Example 2. FIG. Photographs of Sample A (crushed after heating and before crushing) (1) and Sample B (crushing before heating and after heating) of the fulcrum resin cover used in Test Example 2 are shown immediately after heating. 1 is a schematic diagram showing a preparation image of Sample A (crushed after heating and before crushing) (1) and Sample B (crushing before heating and after heating) used in Test Example 2. FIG. 11. It is the schematic diagram which showed description of the X-axis, Y-axis, Z-axis, surface, and deep part in FIG.10 and FIG.11. FIG. 10 is a diagram showing the result of mapping the surface state of Sample A (crushed after heating) in Test Example 2 by infrared microscope FT-IR. FIG. 10 is a diagram showing the result of mapping the surface state of Sample B (crushed before heating) in Test Example 2 by an infrared microscope FT-IR.

Hereinafter, the contents of the present invention will be described in detail with reference to embodiments. However, the present invention is not limited to the embodiments disclosed below.
1) Resin products to be measured Various types of resins to be measured in the present invention are possible. Specifically, various resin products such as polyethylene, polypropylene, polystyrene, polyvinyl chloride, phenol resin, urea resin, melamine resin, silicone resin, nylon 66, nylon 6, and vinylon can be targeted. However, it is of course possible to use other resin products without being limited to the above.

However, in the present invention, the resin preferably does not have a carbonyl group in its main structure (for example, polyethylene terephthalate, acrylic resin, etc.).
In addition, various types of samples, such as bulk solid type and thin film type such as film, can be measured in the present invention.

2) Size of resin to be measured The size of the resin to be measured is not particularly limited. In particular, when an infrared microscope FT-IR is used as the FT-IR to be used, it is possible to measure even if the area of the measurement region is about 100 μm×100 μm. Moreover, it is preferably 1 mm×1 mm or more. Most preferably, it is 10 mm x 10 mm or more.
Also, the thickness of the resin product can be measured if it has a thickness of about 60 μm or more, although it depends on the measurement method.

3) Measurement of internal deterioration (oxidation) of resin piece In the present invention, the surface of the resin in the resin product to be measured is measured by FT-IR, and not only the surface but also the inside is measured. That is, by cutting with a slicer or the like to expose the inside and measuring the FT-IR of the inside, the deterioration (oxidation) state of the inside can be estimated.

As for the direction of cutting, it is preferable to perform FT-IR measurement by cutting in a direction perpendicular to the surface of the resin product and exposing a cross section extending from the surface toward the inside (deep portion). This makes it possible to estimate how the deterioration (oxidation) state changes toward the inside.
Furthermore, it is also possible to cut the substrate substantially parallel to the surface, expose only the interior sequentially, and perform FT-IR measurement.

4) FT-IR measurement
FT-IR stands for Fourier Transform Infrared Spectroscopy (abbreviated as FT-IR).In this method, when the substance to be measured is irradiated with infrared light, the infrared light detects the vibration and rotational motion of molecules. This is a measurement method that utilizes the phenomenon of absorption based on This is because infrared light (2.5 to 25 μm) is used as molecular vibration energy.

FT-IR is a type of infrared spectroscopy that qualitatively and quantifies compounds using the infrared absorption spectrum thus obtained. Further, a specific spectrum can be obtained by Fourier transforming the obtained absorption data. Various types of FT-IR measuring devices are available on the market, and any of them can be used.
The type of FT-IR measurement device that can be used in the present invention is not particularly limited. As for the measuring method, it is preferable to use different methods depending on the shape of the resin piece, etc., but in general, it is roughly divided into a transmission method and a reflection method.

As for the transmission method, the KBr plate method, KBr tablet method, Nujol method, and thin film method can be applied depending on the form and condition of the sample. As for the reflection method, there are various methods such as the ATR method (total reflection measurement method), the specular reflection method, the diffuse reflection method, and the high-sensitivity reflection method, depending on the form and condition of the sample.
In particular, in the present invention, it is preferable to use an infrared microscope FT-IR (microscopic FT-IR) in order to measure deterioration (oxidation) of the resin in minute portions. By using the infrared microscope FT-IR, it is generally possible to measure a sample with an area of about 100 μm ² or a minute area.

By using the FT-IR microscope, it is possible to ascertain the state of deterioration of the resin in minute parts, so it is possible to obtain information on the chemical structure, heterogeneous layers, and boundary layers.
In principle, it is often the case that infrared light is focused on a sample using an aperture or Cassegrain, and absorbed light (transmitted or reflected light) is detected with a semiconductor detector or the like. In this way, the infrared microscope FT-IR can measure the infrared absorption spectrum of a small-sized resin piece, which is smaller than the normal FT-IR.

Next, in the present invention, an infrared microscope FT-IR having a mapping analysis function is preferred. As for the detector, either a linear array detector or a single-element detector can be used, but a linear array detector is more preferable because it shortens the measurement time.

5) Sample preparation Various types of resin sample forms are possible in the present invention. Specific examples include a solid form and a thin film form (film form).
For example, in the case of a solid state, the measuring method can be roughly classified into a transmission method and a reflection method.

Here, the permeation method includes the KBr plate method, the KBr tablet method, the Nujol method, and the like.
As a reflection method, an ATR method, a regular reflection method (regular reflection light), a regular reflection method (transmission reflection light), or the like can be used.
Especially in the present invention, the KBr plate method is preferable among the transmission methods. When the KBr plate method is used in the present invention, a resin sample thinned to about 100 μm (in the range of about 50 to 300 μm) by a slicer or the like is sandwiched between KBr plates for measurement. Generally, in the case of resin, it is easy to form a thin film using a slicer, so sampling can be performed relatively easily in many cases.

Also, it is preferable to measure a permeable resin sample such as a film having a thickness of several μm or less by the transmission method.
Next, as another method, the ATR method can also be used. In the case of the ATR method, an infrared spectrum can be obtained during total reflection in a prism, and the state of the surface can be known. In particular, solid resin or the like that does not transmit infrared light can be measured as it is.
Also, by changing the entrance angle of the infrared light and the type of the prism, it is possible to examine the infrared absorption from various aspects.

Depending on the state of the resin surface, it is also possible to examine the infrared absorption by a specular reflection method.
Moreover, in the case of a resin piece having a large sample size, a method of cutting or peeling off the portion to be measured, or a method of scraping off the sample with a file or the like is also possible. These various methods allow samples to be sampled.
Furthermore, in the case of minute samples, it is effective to use an infrared microscope FT-IR. Infrared microscopes can measure even minute samples of around 50 μm to 100 μm x 50 μm to 100 μm, so if the resin sample is small or the amount of sample is small, the infrared microscope FT-IR is ideally used. be able to. Moreover, in the case of a resin sample composed of a plurality of thin resin layers, each layer can be measured by thinly slicing the cross section.

6) Measurement of the inside of the resin piece In the present invention, not only the surface of the resin piece sample but also the inside is measured. That is, deterioration (oxidation) of the resin is generally reduced from the surface toward the inside.
In particular, when it is desired to know the heating history of a resin sample, the degree of deterioration of the inside may suddenly decrease while the surface of the resin sample undergoes a rapid heat treatment for a short period of time with a large degree of deterioration (oxidation). In the case of such deterioration (oxidation) due to thermal history, it is an effective method to measure the inside after measuring the surface. In particular, it is effective to cut the cross-section perpendicular to the surface so that the transition (change) of deterioration (oxidation) from the surface to the inside can be measured.
As another method, a method of exposing the inner surface by cutting a piece of resin with a slicer or the like is also suitable. By repeating this process, it is possible to confirm by measurement how deterioration (oxidation) is reduced (changed) toward the inside.

7) Measurement execution - measurement wavelength -
In the present invention, the absorption is examined for infrared absorption at wavelengths within the range of 1650-1750 cm ⁻¹ . In the present invention, all of these wavelengths may be measured, or only specific wavelengths within this range may be measured. The absorption in the range of 1650-1750 cm ⁻¹ is assumed to be the peak due to C═O (carbonyl group).

For example, in Fig. 1, after heating a resin piece of polypropylene (Scientific Polymer Products, Inc.) with palm oil at 130 ° C for 3 minutes, a cross section was created with a slicer, and the size of each absorption wavelength at a wavelength of 600 to 4000 cm ^-1 It is a diagram of infrared microscope FT-IR measurement showing the thickness, and it is recognized that there is a unique absorption (because of C=O) at 1650 to 1750 cm ^-1 .

Therefore, the measurement wavelength for FT-IR according to the present invention is approximately 1650 cm to 1750 cm ⁻¹ . Measurements may be made over the entire range of 1650 cm to 1750 cm ⁻¹ . Also, within this range, the wavelength may be in a narrower range (for example, 1670 cm to 1730 cm ⁻¹ ). Also, for example, 1700 cm ⁻¹ , 1680 ⁻¹ , 1720 ⁻¹ or the like may be selected as specific fixed wavelengths. Also, any combination of these wavelengths may be used.

─Measurement range─
In the present invention, it is preferable to map a specific region using FT-IR measurement. By performing mapping, it is possible to two-dimensionally measure the deterioration (oxidation) state of the resin surface. This makes it possible to observe the distribution state of deterioration (oxidation state) of the sample surface. Data can be collected by setting a range to be mapped on the microscope image of the resin sample. In addition, the internal oxidation state can be measured after slicing the surface, or by mapping after measuring the cross section, it is possible to visually grasp the state distribution of internal deterioration (oxidation) more two-dimensionally. can.

Normally, the mapping conditions are not particularly limited, but when using an infrared microscope, the mapping conditions are not particularly limited, but the area of the measurement target is generally 300 μm × 300 μm to 2000 μm × 2000 μm, the number of measurement points is 25 (5 × 5 ) point to 900 (30×30) point.

8) Evaluation method As a result of the measurement, if absorption at 1650 cm to 1750 cm ^-1 is observed in FT-IR on the surface of the resin piece, it is presumed that there is deterioration (oxidation) of the resin due to heating. In this respect, more specifically, it is effective to compare using the same resin material as a comparison object.

For example, when a resin piece exists as a foreign matter, a resin sample made of the same material as the foreign matter can be obtained and compared by measuring the deterioration (oxidation) state of the surface.
Further, when the degree of deterioration (oxidation) of the resin piece as the foreign matter is large, the deterioration (oxidation) state of the surface can be measured after the resin sample for comparison is heat-treated. In the case where the comparative sample shows absorption in the same oxidation state, it is presumed that the foreign matter has undergone a similar heating history.
Furthermore, when the size of the resin piece as a foreign matter is large, a non-oxidized portion inside the sample is sampled and heated in the same manner as the above-mentioned comparative sample, so that the resin piece that becomes a foreign matter is heated. History can be estimated.

9) Specific application examples using the method of the present invention In particular, when resin foreign matter is mixed in the food manufacturing process or the subsequent distribution stage, the degree of deterioration (oxidation) of the resin foreign matter It is possible to estimate the heating history by determining whether the
This makes it possible to estimate the time when the foreign matter is mixed in the food manufacturing process including the heating process. That is, if it is mixed before the heating process, the degree of deterioration (oxidation) of the surface of the foreign matter made of resin will be large.

On the other hand, if it is mixed after the heating process, the degree of deterioration (oxidation) of the surface of the foreign matter made of resin is small.
Next, by measuring the cross section of the sample cut by the slicer, it is possible to determine the progress of the deterioration state inside. Normally, the deterioration state gradually and gently decreases toward the inside, but here, when the internal oxidation state decreases rapidly compared to the surface oxidation state, It can be inferred that it was suddenly exposed to a severe heating environment (high temperature, high heat, etc.). That is, the possibility of contamination before the heating process increases.
More specifically, regarding infrared absorption in the range of 1650 cm to 1750 cm ⁻¹ , while a large infrared absorption is observed on the surface side of the resin, a rapid decrease in infrared absorption is observed inside the resin. , high temperature, and high heat.

Next, in the above analysis, it is preferable to obtain and prepare a resin product of the same material as a comparison target for the resin product to be analyzed, which is the foreign matter. That is, by obtaining a resin sample to be compared and analyzing the components of the comparative sample, the degree of deterioration (oxidation) of the foreign matter can be determined by comparing the infrared absorption results of the resin foreign matter to be measured. It is possible to judge
In addition, it is possible to test whether or not the comparison sample can be subjected to a heat treatment such as heating or high temperature to obtain an oxidation state comparable to that of the sample to be analyzed. This makes it possible to estimate the heating status of the resin foreign matter.

In addition, a portion of the sample to be analyzed, which is a foreign matter, is not degraded (oxidized) and is cut out, and is forcibly degraded by heating as described above, thereby estimating the deterioration state of the sample to be analyzed. good too.
As described above, the heating history of the sample to be analyzed can be estimated by various methods.
Moreover, in the obtained resin piece of the foreign matter, there are many cases where the surface is broken by some kind of impact. The present invention can be particularly effectively used when such a resin has a fractured surface. If the foreign matter is found in a process that has a heating process in a food factory, etc., the entire fractured surface is deteriorated (oxidized) with respect to the foreign matter that has a fractured surface, and the fractured surface deteriorates inward. If it was (oxidized), it is presumed that it was heated after it cracked. In addition, if deterioration (oxidation) is not observed on the fractured surface, and deterioration (oxidation) is observed from the surface to the center of the fractured surface, it is presumed that the specimen was heated after being cracked.
Thus, it can be deduced whether the fracture occurred before heating or after heating. Test examples of the present invention are shown below.

[Test Example 1] (Degradation (oxidation) due to UV irradiation or heating)
A resin piece made of polypropylene was used and subjected to UV irradiation for forced deterioration. An infrared microscope (FT-IR) was used to examine the degradation (oxidation) state of resin pieces after UV irradiation or heat treatment.
○ Target sample A plurality of pieces of polypropylene (Scientific Polymer Products, Inc.) resin pieces (disc-shaped with a diameter of 3 mm and a height of 2 mm) were used.
〇 Analysis method (1) Degradation test As a degradation test (forced degradation test), two types of UV irradiation and thermal degradation were carried out.
─Ultraviolet irradiation─

As a deterioration test, ultraviolet deterioration was performed. Using a handy type UV lamp (ASONE Co., Ltd. SLUV-4), the target sample was irradiated with a wavelength of 365 nm to cause ultraviolet deterioration. Samples were collected before UV irradiation, 2 days, 5 days, 12 days and 36 days after irradiation.
─Thermal deterioration─
A constant temperature dryer was set to 130° C. to heat-degrade the target sample. Samples were collected before the start of heating and 2 days, 5 days, 12 days, and 36 days after the start of heating.

(2) Measurement method After deterioration for a predetermined time, cut the central part vertically as shown in FIG. A cross section was prepared as shown in FIG. 2 using a mold angle variable slicer.
The cross section was mapped by infrared microscope FT-IR at wavelengths (infrared absorption over the range of 1650 cm to 1750 cm ⁻¹ ) derived from degradation (oxidation). FT/IR-6100 and IRT-5000 manufactured by JASCO Corporation were used as the infrared microscope FT-IR.

Among transmission methods, the KBr plate method was used as the measurement method. In this test example, a resin thinned to a thickness of about 100 μm by a slicer was sandwiched between KBr plates and measured.
Mapping conditions were a measurement area of 800 μm×600 μm and a measurement point of 48 points (8 points×6 points).
As a result, first, FIG. 3 shows changes in the appearance of the resin piece (ultraviolet irradiation and thermal degradation) after UV irradiation and thermal degradation for each number of days.

As for the change in appearance, a change in color to yellow was observed in the UV-irradiated one. The UV-irradiated one became yellowish over time, but no significant change was observed after the 12th day. On the other hand, no remarkable change was observed in the case of heat deterioration.
Next, the resin piece after each day was cut as shown in FIG. 2, the cross section was sliced, and the surface state was mapped in the measurement area of the sample. FIG. 4 shows the results for UV irradiation, and FIG. 5 shows the results for thermal degradation. In addition, FIG. 5 also shows the result of heating the resin piece with palm oil at 130° C. for 3 minutes as a comparison of the case of rapid heating with respect to the heating conditions.

In the case of FIG. 4 (ultraviolet degradation), the absorption peak derived from degradation by UV rays increased from the surface. UV deterioration gradually progressed inward from the surface of the resin sample. In this way, it was found that the deterioration state of the surface or inside of resin products due to ultraviolet rays can be determined by using the infrared microscope FT-IR.
Next, in the case of FIG. 5 (thermal deterioration), the absorption peak derived from resin deterioration increased from the surface. In the case of deterioration (oxidation) due to heating, the deterioration toward the inside of the sample was relatively small compared to the case of UV.

In addition, heating in palm oil caused oxidation even for a short time of 3 minutes. This is considered to be due to the difference in thermal conductivity (oil (around 0.15) and air (0.025)). In this way, by using an infrared microscope FT-IR, it is possible to determine the state of deterioration on the surface or inside of a resin product, and to estimate whether the deterioration (oxidation) is due to UV irradiation or heating. rice field.
Furthermore, it was found that it is possible to estimate whether it is thermal deterioration due to hot air or thermal deterioration in oils and fats from the difference in deterioration due to heating (atmosphere) and deterioration in liquids such as oils and fats in FIG.

[Test Example 2] (When using a sample after crushing the resin)
In many cases, a resin piece as a foreign matter found in an actual production line of processed foods has a fractured surface where the surface is fractured by some kind of impact. The present invention has been tested to see if such resins can be used particularly effectively when they have fractured surfaces. Using the resin cover (material: polypropylene) of the fulcrum of the kitchen scissors as the resin piece, the resin piece was prepared by heating after breaking the target resin and heating before breaking, and the infrared microscope FT after the adjustment -Measurement test by IR was carried out.
As for the infrared microscope FT-IR, as in Test Example 1, types FT/IR-6100 and IRT-5000 manufactured by JASCO Corporation were used. As for the measurement method, the KBr plate method among transmission methods was used as in Test Example 1.

○ Analysis method (1) Degradation test Resin pieces were prepared by heating after breaking the target resin and heating before breaking, and a measurement test was performed with an infrared microscope FT-IR after the adjustment. The fulcrum resin cover was forcedly deteriorated by heating in palm oil at 130° C. for 3 minutes in two patterns. First, FIG. 6 shows a photograph of the resin cover before heating.
For sample A, the fulcrum resin cover was heated at 130° C. for 3 minutes in palm oil and then crushed. For sample B, after crushing the fulcrum resin cover, it was heated in palm oil at 130° C. for 3 minutes. Photographs of sample A (before crushing) and sample B immediately after heating are shown in FIGS. 7(1) and 7(2).

(2) Measurement Method As in Test Example 1, the samples A and B were mapped using an FT-IR infrared microscope at wavelengths derived from deterioration (oxidation) (infrared absorption over the entire range of 1650 cm to 1750 cm ⁻¹ ).
As for the mapping conditions, as in Test Example 1, the measurement area was 1000 μm×600 μm and the number of measurement points was 60 points (10 points×6 points).

Further, for sample A, the resin cover crushed after heating was subjected to mapping of the surface and cross section after slicing with an infrared microscope FT-IR. For sample B, the resin cover heated after crushing was mapped by an infrared microscope FT-IR on the surface and cross section after slicing.
Preparation images of sample A and sample B are shown in FIG.

As for the mapping results, FIG. 10 shows the surface degradation (oxidation) state mapping results for Sample A (when crushed after heating). FIG. 11 shows the mapping of the surface oxidation state of sample B (when heated after crushing).
Further, in each figure of the results, as shown in FIG. 9, the fracture surface is expressed as the X and Y axes, and the Z axis extending from the fracture surface toward the depth.

FIG. 10 shows the results of surface state mapping by an infrared microscope FT-IR for sample A (crushed after heating) and sample B (crushed before heating).
In the case of sample A (crushed after heating), the fracture surface (XY axis) is remarkably oxidized at the surface and gradually oxidized toward the center. In addition, almost no deterioration (oxidation) was observed in the deep part (Z-axis) from the fracture surface.
In the case of sample B (crushed before heating), the entire surface of the fractured surface (XY axes) was oxidized. In addition, the surface was remarkably oxidized from the fracture surface to the depth (Z-axis), and the oxidation progressed gradually toward the depth.

From the above results, when using the determination method of the present invention, for foreign matter with a fractured surface with an unknown heating history, the entire fractured surface has deteriorated (oxidized), and the fractured surface has deteriorated (oxidized) inward. oxidation) progressed, it can be presumed that it was heated after cracking.
On the other hand, if deterioration (oxidation) is not observed on the fractured surface, and deterioration (oxidation) is observed from the surface to the center of the fractured surface, it can be assumed that the fractured surface has been heated.
Considering the results of Test Example 1, deterioration (oxidation) takes a long time in ultraviolet deterioration and thermal deterioration due to heat, but deterioration (oxidation) occurs in a short period of several minutes in the case of thermal deterioration in fats and oils.
Thus, in both cases of Test Examples 1 and 2, it was found that the heating history of resin products can be estimated by using FT-IR (infrared microscope FT-IR).

Claims (5)

Regarding the state of deterioration or oxidation of the surface or inside of the resin product, measure the infrared absorption of the wavelength within the range of 1650 to 1750 cm ^-1 by Fourier transform infrared spectroscopy (FT-IR) on the surface or inside of the resin product. A method of estimating the heating history of the resin product by
2. The method of claim 1, wherein the infrared absorption measurements are taken at multiple points on the surface or inside the resin product to map the surface or internal degradation (oxidation) state.
3. The method according to claim 1 or 2, wherein the resin product is a resin foreign matter mixed in during the production of processed food including a heating process.
Using the method according to claim 3, resin-made foreign matter that was mixed in during the production of processed food including the heating process or during the subsequent distribution, and whether the foreign matter was mixed before the heating process. , or a method of estimating whether it was mixed after the heating process.
When the resin foreign matter has a fracture surface, the method according to claim 4 is used to determine whether the resin foreign matter is fractured before the heating step or after the heating step. How to estimate .

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